Supracerebellar transtentorial approach to posterior temporomedial structures

Surgical Anatomy of the Retrosigmoid Approach With Transtentorial Extension: Protecting the 4th Cranial Nerve

BACKGROUND AND OBJECTIVES

The retrosigmoid approach with transtentorial extension (RTA) allows us to address posterior cranial fossa pathologies that extend through the tentorium into the supratentorial space. Incision of the tentorium cerebelli is challenging, especially for the risk of injury of the cranial nerve (CN) IV. We describe a tentorial incision technique and relevant anatomic landmarks.

METHODS

The RTA was performed stepwise on 5 formalin-fixed (10 sides), latex-injected cadaver heads. The porus trigeminus's midpoint, the lateral border of the suprameatal tubercle (SMT)'s base, and cerebellopontine fissure were assessed as anatomic landmarks for the CN IV tentorial entry point, and relative measurements were collected. A clinical case was presented.

RESULTS

The tentorial opening was described in 4 different incisions. The first is curved and starts in the posterior aspect of the tentorium. It has 2 limbs: a medial one directed toward the tentorium's free edge and a lateral one that extends toward the superior petrosal sinus (SPS). The second incision turns inferiorly, medially, and parallel to the SPS down to the SMT. At that level, the second incision turns perpendicular toward the tentorium's free edge and ends 1 cm from it. The third incision proceeds posteriorly, parallel to the free edge. At the cerebellopontine fissure, the incision can turn toward and cut the tentorium-free edge (fourth incision). On average, the CN IV tentorial entry point was 12.7 mm anterior to the SMT base's lateral border and 20.2 mm anterior to the cerebellopontine fissure. It was located approximately in the same coronal plane as the porus trigeminus's midpoint, on average 1.9 mm anterior.

CONCLUSION

The SMT and the cerebellopontine fissure are consistently located posterior to the CN IV tentorial entry point. They can be used as surgical landmarks for RTA, reducing the risk of injury to the CN IV.

SupraPetrous InfraTemporal Approach: A Supplemental Approach to Supracerebellar Infratentorial for Inferior Amygdala and Hippocampal Head Access-A Cadaveric Study With Case Illustrations

BACKGROUND AND OBJECTIVES

Access to the amygdala and hippocampus (A/H) is complex. To address the limitations and invasiveness of traditional approaches, including the Transsylvian, Subtemporal, and Supracerebellar infratentorial approaches, we developed the suprapetrous infratemporal (SPIT) approach. This study describes the nuances of this approach in both cadaveric studies and clinical cases.

METHODS

Three unilateral exposures were performed using microscopic and endoscopic methodologies in the SPIT approach. After cadaveric investigation, this approach was successfully implemented in representative clinical cases.

RESULTS

The SPIT approach enabled direct access to the inferior A/H, circumventing the requirement for temporal lobe retraction and detachment of the temporal lobe from the dura through a subtemporal route by drilling the upper part of the mastoid, consequently mitigating tension on the vein of Labbé. This enabled a bottom-up view because one would gain with a zygomatic osteotomy and forward projection like a mini-posterior petrosal view by using a transmastoid view, without cutting down the zygomatic arch and opening the dura subtemporally, limiting patient pain and preventing case comorbidity. The SPIT approach was performed in 2 cases of mesial temporal cavernoma presenting with seizures. The lesion was visualized intraoperatively and was successfully removed in these cases. The postoperative course was excellent with no complications, and gross total resection was radiographically confirmed with Engel Class 1a seizure freedom.

CONCLUSION

The SPIT approach is a complementary approach for inferior A/H disease, combining the combined middle fossa approach modified for intradural pathology. Limited drilling of the upper aspect of the mastoid with a medial dural opening at the level of the arcuate eminence provides a direct trajectory with minimal brain retraction. Additional research encompassing a larger patient cohort and extended follow-up periods is required to substantiate the advantages of SPIT in the management of inferior A/H lesions.

Endoscopic-enhanced supra-cerebellar trans-tentorial (SCTT) approach to temporo-mesial region: a multicenter study

Surgical access to the temporo-mesial area may be achieved by several routes such as the sub-temporal, the temporal trans-ventricular, the pterional/trans-sylvian, and the occipital interhemispheric approaches; nonetheless, none of them has shown to be superior to the others. The supra-cerebellar trans-tentorial approach allows a great exposure of the middle and posterior temporo-mesial region, while avoiding temporal lobe retraction. A prospective multicenter study was designed to collect data on patients undergoing endoscopic-enhanced SCTT approach to excise left temporo-mesial lesions. The study involved 5 different neurosurgical European centers and ran from 2015 to 2020. All patients had preoperative as well as postoperative brain MRI and ophthalmology evaluation. A total of 30 patients were included in this study, the mean follow-up was 44 months (range 18 to 84 months), male/female ratio was 16/14, and mean age was 39 years. A gross total resection was achieved in 29/30 (96.7%) cases. All surgical procedures were uneventful, without transient or permanent neurological deficits thanks to the preservation of the posterior cerebral artery. The endoscopic-enhanced SCTT approach provides satisfactory exposure to the left temporo-mesial region. Its minimally invasive nature helps minimize the surgical risks related to vascular and white tract manipulation, which represent known limitations of open microsurgical as well as other approaches.

Endovascular treatment of P3 segment of posterior cerebral artery aneurysm with stent and coils

Posterior cerebral artery (PCA) aneurysms are rare and usually arise from proximal portion of the artery. The distal location is even less frequent, and aneurysms in this location tend to be larger and dissecting. Although they can be treated by direct surgery, recently endovascular procedures have been preferred in some centers. We report a case of large aneurysm of the posterior cerebral artery in a 45-year-old female presenting with headache. An uneventful endovascular treatment was performed with stent and platinum coils achieving total occlusion of the aneurysm, and the patient had good recovery. The findings are compared to earlier reports and literature regarding the issue is discussed.

Supracerebellar transtentorial approach for left parahippocampal cavernous malformation

Background:

Lesions in the temporomesial region can be reached by various approaches: subtemporal, transsylvian, transcortical, interhemispheric parieto-occipital, or supracerebellar transtentorial (SCTT). The choice varies according to the characteristics of the lesion and neighboring structures.

Case Description:

In this clinical case, it is presented a 56-year-old man with long-term evolution of drug-resistant epilepsy secondary to a cavernoma in the left parahippocampal gyrus. After assessing the lesion, it was decided a SCTT approach for its resection in a semi-sitting position, to avoid language disorders or visual damage. The surgery was uneventful and the patient did not present epileptic seizures during 6-month follow-up.

Conclusion:

Performing a SCTT is safe and feasible option for resection of lesions located in the basal temporomesial region without causing damage to neighboring structures, especially those located in the middle and posterior two-thirds of temporal region.

How I do it: paramedian supracerebellar transtentorial approach for a temporomesial glioma

BACKGROUND

Classical approaches to the temporomesial region (TMR) include transtemporal, transylvian, or subtemporal. The supracerebellar infratentorial, initially developed to access dorsolateral cavernomas, has of late shown its versatility to access areas around the central core. The TMR is one such area that can be accessed through this approach with the addition of a tentorial incision.

METHOD

The paramedian supracerebellar transtentorial approach (PSCTA) is described along with its advantages and limits compared to other approaches to treat TMR gliomas.

CONCLUSION

The PSCTA offers a basal panoramic view of the TMR without the need of retraction, cortical incision, and white matter transgression.

Comparison of the keyhole trans-middle temporal gyrus approach and transsylvian approach for selective amygdalohippocampectomy: A single-center experience

Several approach routes exist for selective amygdalohippocampectomy (SAH); however, previous reports regarding a comparison of these routes are limited. Here, we compared trans-middle temporal gyrus (T2) SAH and transsylvian (TS) SAH in terms of seizure outcome, visual-field defect, memory function, and operation time in our institution. This retrospective study examined the data of 16 patients with medically intractable mesial temporal lobe epilepsy. Six patients underwent trans-T2 SAH and 10 patients underwent TS SAH between July 2014 and February 2019 in Osaka City University Hospital. In trans-T2 SAH, we performed a keyhole temporal craniotomy and a small corticotomy on T2. In TS SAH, we performed a 1.5 cm corticotomy along the inferior periinsular sulcus after opening the sylvian fissure. Amygdalohippocampectomy after reaching the inferior horn of the lateral ventricle was performed in the same manner in both procedures. The seizure outcome, visual-field defect, memory function, and operation time were retrospectively compared between the procedures. Seizure-free outcomes were achieved for six patients in the trans-T2 SAH and eight patients in the TS SAH group. There were no significant differences in the seizure outcome, visual-field defect, and memory function. The operation time was significantly shorter for trans-T2 SAH than TS SAH. The postoperative scar was less conspicuous for trans-T2 SAH. Trans-T2 SAH and TS SAH were comparable in terms of the seizure outcome, visual-field defect, and memory function. The operation time and length of the skin incision were shorter for trans-T2 SAH, suggesting that it may be preferable for general epilepsy surgeons.

Outcomes in single-level posterior cervical spine surgeries performed in the sitting and prone positions

OBJECTIVE

The sitting or semisitting position in neurosurgery allows for several technical advantages, including improved visualization of the surgical field. However, it has also been associated with an increased risk of venous air embolisms and positioning-related complications that limit its commonplace adoption. The authors report a large, single-center series of cervical spine procedures performed with patients in the sitting or prone position in order to assess the perceived risk of intraoperative and postoperative complications associated with the sitting position.

METHODS

Noninstrumented, single-level posterior cervical spine procedures performed with patients in the sitting/semisitting or prone position from 2000 to 2016 at a single institution were reviewed. Institutional abstraction tools (DataMart and Chart Plus) were used to collect data from the medical records. The two positions were compared with regard to preoperative factors, intraoperative variables, and postoperative outcomes. Multivariable logistic regression models were fitted for 30-day readmission, 30-day return to the operating room, and complication rates.

RESULTS

A total of 750 patients (sitting, n = 480; prone, n = 270) were analyzed. The median age was 53 years for those who underwent surgery in the prone position and 50 years for those who underwent surgery in the sitting position (IQRs 45-62 years and 43-60 years, respectively), and 35% of the patients were female. Sitting cases were associated with significantly longer anesthetic times (221 minutes [range 199-252 minutes] vs 205 minutes [range 179-254 minutes]) and operative times (126 minutes [range 101-163 minutes] vs 149 minutes [120-181 minutes]). Cardiorespiratory events in the postanesthesia care unit (PACU) were comparable between the two groups, with the exception of episodes of apnea (2.6% vs 0.6%, p = 0.041) and hypoventilation (4.4% vs 0.8%, p < 0.003), which were more frequent in the prone-position cohort. On multivariable analysis, the effect of the sitting versus the prone position was not significant for 30-day readmission (OR 0.77, 95% CI 0.34-1.71, p = 0.52) or reoperation (OR 0.71, 95% CI 0.31-1.60, p = 0.40). The sitting position was associated with lower odds of developing any complication (OR 0.31, 95% CI 0.16-0.62, p < 0.001).

CONCLUSIONS

Based on the intraoperative and postoperative complications chosen in this study, the sitting position confers a similar safety profile to the prone position. This can be explained by a more anatomic positioning accounting for reduced temporary neurological deficits and reduced PACU-associated hypoventilation noted in this series. Nevertheless, the findings may also reflect institutional familiarity, experience, and mastery of this position type, and outcomes may not reflect practices in general.

Ergonomics of surgical microscopes for the sitting position as determined by ocular-corpus length

Background:

The sitting position is favorable for microsurgical procedures applied to posterior midline pathologies in both the supra- and infratentorial regions. The dimensions of the microscope corpus affect the device’s comfort and handling in the hands of the microneurosurgeon for such procedures. A shorter microscope corpus provides more favorable intraoperative ergonomics for surgical practice.

Methods:

Evaluation of the most comfortable microscope for its application in microsurgical procedures in the sitting position as determined by ocular-corpus length.

Results:

Six modern surgical microscopes were tested and evaluated regarding their ocular-corpus lengths and working distances: the Mitaka MM90, Zeiss Kinevo 900, Zeiss Pentero 900, Leica M530, Zeiss Neuro NC4, and Möller-Wedel Hi-R 1000. The ocular-corpus lengths vary between 270 and 380 mm. The Mitaka MM90 microscope has the shortest ocular-corpus length at 270 mm.

Conclusion:

The ocular-corpus length determines the predominant part of the lever arm, which affects the fatigue of the surgeon. By virtue of its short ocular-corpus length, the Mitaka MM90 is currently the most favorable microscope for microsurgical procedures using a sitting position.

Parietal transventricular approach for medial temporal glioma: A technical report

Background:

Medial temporal lobectomy (MTLy) poses a surgical challenge due to convoluted anatomy of medial temporal lobe (MTL). Various approaches have been described to access MTL for removing various pathologies. We, hereby, describe the parietal transventricular approach for removing a concurrent medial temporal glioma in a patient with recurrent parietal glioma.

Case Description:

A 40-year-old female operated and diagnosed case of the right parietal anaplastic astrocytoma presented to us with a recurrence in parietal region. In addition, a fresh lesion was observed in the right MTL suggestive of a separate temporal glioma. The patient underwent excision of both parietal and temporal gliomas through the parietal approach only. Complete excision of parietal recurrence and near-total excision of medial temporal glioma was achieved.

Conclusion:

The parietal approach can be used for excision of medial temporal lesions, especially those involving or extending into its posterior limits. In the presence of concurrent parietal and MTL lesions, both lesions can be removed through a single parietal approach rather than a separate approach for MTLy. It offers additional advantages of the preservation of optic radiations as well as the temporal neocortex. The visual orientation of MTL structures is different when viewed from the parietal approach as compared to the temporal approaches. The parietal approach provides in line orientation of medial temporal structures contrary to the perpendicular orientation visualized in temporal approaches. An understanding of MTL anatomy as viewed from a parietal vantage point and its three-dimensional conceptualization is very important to successfully remove lesions of MTL through the parietal approach.

Supracerebellar Transtentorial Approach for Occipital Meningioma to Maximize Visual Preservation: Technical Note

BACKGROUND AND IMPORTANCE

Surgery for resection of tentorial meningiomas compressing primary visual cortex carries a significant risk of worsening vision. This concern is especially acute in patients with a preexisting visual deficit. Approaches that involve mechanical retraction of the occipital lobe further threaten visual function. The supracerebellar transtentorial (SCTT) approach, which does not carry a risk of occipital retraction injury, should be considered for patients with occipital tentorial meningiomas to maximize functional visual outcomes.

CLINICAL PRESENTATION

A 54-yr-old woman underwent 2 resections and radiation therapy for a right occipital oligodendroglioma as a teenager. She was left with a complete left homonymous hemianopsia. The patient now presented with progressive vision loss in her remaining right visual field. Imaging revealed a left occipital superiorly projecting tentorial meningioma. To preserve her remaining visual function the SCTT approach was chosen for resection. A Simpson grade 1 removal was achieved without disrupting the occipital lobe pia or requiring mechanical cerebellar retraction. A diagnosis of a WHO grade II meningioma (presumably radiation induced) was made. The patient's vision returned to premorbid baseline 1 wk after surgery.

CONCLUSION

The SCTT approach should be considered for the surgical management of patients with occipital tentorial meningiomas when visual preservation is at risk. This approach avoids transgression of visual cortex and minimizes the risk of venous infarction or contusions from retraction injury.

UniversitätsSpital Zürich: 80 years of neurosurgical patient care in Switzerland

Background

The predecessor of today’s Department of Neurosurgery, UniversitätsSpital Zürich (USZ), was founded 80 years ago as the first independent Swiss clinic dedicated to neurosurgical patient care. On the occasion of this anniversary, we aimed to highlight the history of neurosurgery as a specialty at the USZ, and to put it into the historical context of Swiss and European Neurosurgery.

Method

A literature review was conducted and we searched the archives of the USZ and the city of Zurich, as well as those of Swiss journals to extract relevant published articles, books, historical reports and pictures. The USZ Department of Medical History, the Museum of Medical History and the Swiss National Library were contacted to provide source material. To further verify the content, (emeritus) faculty from the USZ and external experts on the history of Swiss neurosurgery reviewed the manuscript.

Results

Surgeries of the head and spine had occasionally been conducted in Zurich by the general surgeons, Rudolf Ulrich Krönlein and Paul Clairmont, before an independent neurosurgical clinic was founded by Hugo Krayenbühl on 6 July 1937. This was the first Swiss department dedicated to neurosurgical patient care. Besides providing high-quality medicine for both the local and wider population, the department was chaired by eminent leaders of neurosurgery, who influenced the scientific and clinical neurosurgery of their time. As such, it has long been regarded as one of the top teaching and research hospitals in Switzerland and in Europe.

Conclusions

On the occasion of its 80th anniversary, we have performed an in-depth review of its development, successes and challenges, with a special focus on the early decades. Reflecting on the past, we have identified common denominators of success in neurosurgery that remain valid today.

Electronic supplementary material

The online version of this article (10.1007/s00701-017-3357-z) contains supplementary material, which is available to authorised users.

Microsurgical and endoscopic approaches to the pulvinar

OBJECTIVE

Approaches to the pulvinar remain challenging because of the depth of the target, surrounding critical neural structures, and complicated arterial and venous relationships. The purpose of this study was to compare the surgical approaches to different parts of the pulvinar and to examine the efficacy of the endoscope as an adjunct to the operating microscope in this area.

METHODS

The pulvinar was examined in 6 formalin-fixed human cadaveric heads through 5 approaches: 4 above and 1 below the tentorium. Each approach was performed using both the surgical microscope and 0° or 45° rigid endoscopes.

RESULTS

The pulvinar has a lateral ventricular and a medial cisternal surface that are separated by the fornix and the choroidal fissure, which wrap around the posterior surface of the pulvinar. The medial cisternal part of the pulvinar can be further divided into upper and lower parts. The superior parietal lobule approach is suitable for lesions in the upper ventricular and cisternal parts. Interhemispheric precuneus and posterior transcallosal approaches are suitable for lesions in the part of the pulvinar forming the anterior wall of the atrium and adjacent cisternal part. The posterior interhemispheric transtentorial approach is suitable for lesions in the lower cisternal part and the supracerebellar infratentorial approach is suitable for lesions in the inferior and medial cisternal parts.

The microscope provided satisfactory views of the ventricular and cisternal surfaces of the pulvinar and adjacent neural and vascular structures. The endoscope provided multi-angled and wider views of the pulvinar and adjacent structures.

CONCLUSIONS

A combination of endoscopic and microsurgical techniques allows optimal exposure of the pulvinar.

Endoscopic Supracerebellar Transtentorial Approach to Atrium of Lateral Ventricle: Preliminary Surgical and Optical Considerations

OBJECTIVE

We sought to report the operative techniques of the endoscopic supracerebellar transtentorial approach (ESTA) to the atrium of the lateral ventricle, especially focusing on the role of the endoscope and analyzing optically related issues.

METHODS

A retrospective data review was performed on 5 patients with lesions in the atrium of the lateral ventricle undergoing the ESTA. The patients were positioned in the three quarters prone position, and a paramidline linear incision was used. After performing a suboccipital craniotomy extending immediately above the transverse sinus and tentorium incision with precisely neuronavigation, corticotomy in the posterior mediobasal temporal region created a corridor to the tumor. All of the procedures were performed with an endoscope in a pneumatic arm holder. The preoperative and postoperative perimetry test and diffusion tensor imaging fiber tracking of the optic radiations were compared and analyzed.

RESULTS

Three patients had meningiomas, and 2 patients had high-grade gliomas in the atrium. The meningiomas were totally removed, and the gliomas were subtotally resected. One patient with glioblastoma died 2 months later after surgery because of the tumor progression; the remaining 4 patients had a visual field deficit without any other neurologic complications. The endoscope improved the surgical viewing angle, which was restricted by the microscope and slope of the tentorium.

CONCLUSIONS

ESTA is an alternative route to the atrium of the lateral ventricle. However, the collateral sulcus, which is highly relied on in neuronavigation, is illegible in the limited area. And the visual field deficit remains the primary challenge with this approach.

Transtentorial transcollateral sulcus approach to the ventricular atrium: an endoscope-assisted anatomical study

OBJECTIVE

Conventional approaches to the atrium of the lateral ventricle may be associated with complications related to direct cortical injury or brain retraction. The authors describe a novel approach to the atrium through a retrosigmoid transtentorial transcollateral sulcus corridor.

METHODS

Bilateral retrosigmoid craniotomies were performed on 4 formalin-fixed, colored latex–injected human cadaver heads (a total of 8 approaches). Microsurgical dissections were performed under 3× to 24× magnification, and endoscopic visualization was provided by 0° and 30° rigid endoscope lens systems. Image guidance was provided by coupling an electromagnetic tracking system with an open source software platform. Objective measurements on cortical thickness traversed and total depth of exposure were recorded. Additionally, the basal occipitotemporal surfaces of 10 separate cerebral hemisphere specimens were examined to define the surface topography of sulci and gyri, with attention to the appearance and anatomical patterns and variations of the collateral sulcus and the surrounding gyri.

RESULTS

The retrosigmoid approach allowed for clear visualization of the basal occipitotemporal surface. The collateral sulcus was identified and permitted easy endoscopic access to the ventricular atrium. The conical corridor thus obtained provided an average base working area of 3.9 cm2 at an average depth of 4.5 cm. The mean cortical thickness traversed to enter the ventricle was 1.4 cm. The intraventricular anatomy of the ipsilateral ventricle was defined clearly in all 8 exposures in this manner. The anatomy of the basal occipitotemporal surface, observed in a total of 18 hemispheres, showed a consistent pattern, with the collateral sulcus abutted by the parahippocampal gyrus medially, and the fusiform and lingual gyrus laterally. The collateral sulcus was found to be caudally bifurcated in 14 of the 18 specimens.

CONCLUSIONS

The retrosigmoid supracerebellar transtentorial transcollateral sulcus approach is technically feasible. This approach has the potential advantage of providing a short and direct path to the atrium, hence avoiding violation of deep neurovascular structures and preserving eloquent areas. Although this approach appears unconventional, it may provide a minimally invasive option for the surgical management of selected lesions within the atrium of the lateral ventricle.

[An aneurysm of the medial posterior choroidal artery: a case report and a literature review]

INTRODUCTION

Aneurysms of the medial posterior choroidal artery are very rare. To date, only 5 cases have been reported. The article presents a case of successful surgical treatment of an aneurysm of the medial posterior choroidal artery and a literature review.

CLINICAL CASE

A 57-year-old male was admitted to the Center 1 month after a massive subarachnoid hemorrhage. CT angiography revealed an aneurysm of the right posterior medial choroidal artery in the perimesencephalic cistern and resolved hemorrhage.

TREATMENT

The paramedian supracerebellar transtentorial approach to the lateral surface of the midbrain was used. The posterior cerebral artery was identified in the perimesencephalic cistern, and the medial posterior choroidal artery aneurysm was isolated and successfully clipped, with the parent artery being preserved. Postoperative CT and MRI scans revealed a small asymptomatic ischemic lesion in the tectal region on the right. The patient was discharged without any neurological symptoms 10 days after surgery.

CONCLUSION

Medial posterior choroidal artery aneurysms can be clipped using the paramedian supracerebellar transtentorial approach.

Efficacy of the transtemporal approach with awake brain mapping to reach the dominant posteromedial temporal lesions

BACKGROUND

Surgeries for lesions in the dominant hippocampal and parahippocampal gyrus involving the posteromedial temporal regions are challenging to perform because they are located close to Wernicke's area; white matter fibers related with language; the optic radiations; and critical neurovascular structures. We performed a transtemporal approach with awake functional mapping for lesions affecting the dominant posteromedial temporal regions. The aim of this study was to assess the feasibility, safety, and efficacy of awake craniotomy for these lesions.

METHODS

We retrospectively reviewed four consecutive patients with tumors or cavernous angiomas located in the left hippocampal and parahippocampal gyrus, which further extended to the posteromedial temporal regions, who underwent awake surgery between December 2014 and January 2016.

RESULTS

Four patients with lesions associated with the left hippocampal and parahippocampal gyrus, including the posteromedial temporal area, who underwent awake surgery were registered in the study. In all four patients, cortical and subcortical eloquent areas were identified via direct electrical stimulation. This allowed determination of the optimal surgical route to the angioma or tumor, even in the language-dominant hippocampal and parahippocampal gyrus. In particular, this approach enabled access to the upper part of posteromedial temporal lesions, while protecting the subcortical language-related fibers, such as the superior longitudinal fasciculus.

CONCLUSIONS

This study revealed that awake brain mapping can enable the safe resection of dominant posteromedial temporal lesions, while protecting cortical and subcortical eloquent areas. Furthermore, our experience with four patients demonstrates the feasibility, safety, and efficacy of awake surgery for these lesions.

Surgical Approaches to the Temporal Horn: An Anatomic Analysis of White Matter Tract Interruption

BACKGROUND: Surgical access to the temporal horn is necessary to treat tumors and vascular lesions, but is used mainly in patients with mediobasal temporal epilepsy. The surgical approaches to this cavity fall into 3 primary categories: lateral, inferior, and transsylvian. The current neurosurgical literature has underestimated the interruption of involved fiber bundles and the correlated clinical manifestations.

OBJECTIVE: To delineate the interruption of fiber bundles during the different approaches to the temporal horn.

METHODS: We simulated the lateral (trans-middle temporal gyrus), inferior (transparahippocampal gyrus), and transsylvian approaches in 20 previously frozen, formalin-fixed human brains (40 hemispheres). Fiber dissection was then done along the lateral and inferior aspects under the operating microscope. Each stage of dissection and its respective fiber tract interruption were defined.

RESULTS: The lateral (trans-middle temporal gyrus) approach interrupted “U” fibers, the superior longitudinal fasciculus (inferior arm), occipitofrontal fasciculus (ventral segment), uncinate fasciculus (dorsolateral segment), anterior commissure (posterior segment), temporopontine, inferior thalamic peduncle (posterior fibers), posterior thalamic peduncle (anterior portion), and tapetum fibers. The inferior (transparahippocampal gyrus) approach interrupted “U” fibers, the cingulum (inferior arm), and fimbria, and transected the hippocampal formation. The transsylvian approach interrupted “U” fibers (anterobasal region of the extreme capsule), the uncinate fasciculus (ventromedial segment), and anterior commissure (anterior segment), and transected the anterosuperior aspect of the amygdala.

CONCLUSION: White matter dissection improves our knowledge of the complex anatomy surrounding the temporal horn. Identifying the fiber bundles at risk during each surgical approach adds important information for choosing the appropriate surgical strategy.

The paramedian supracerebellar transtentorial approach to the posterior fusiform gyrus

BACKGROUND

The posterior fusiform gyrus lies in a surgically challenging region. Several approaches have been described to access this anatomical area. The paramedian supracerebellar transtentorial (SCTT) approach benefits from minimal disruption of normal neurovascular tissue. The aim of this study was to demonstrate its application to access the posterior fusiform gyrus.

METHODS

Three brains and six cadaveric heads were examined. A stepwise dissection of the SCTT approach to the posterior fusiform gyrus was performed. Local cortical anatomy was studied. The operability score was applied for comparative analysis on surgical anatomy.

RESULTS

The major posterior landmark used to identify the fusiform gyrus with respect to the medial occipitotemporal gyrus was the collateral sulcus, which commonly bifurcated at its caudal extent. Compared with other surgical approaches addressed to access the region, SCTT demonstrated the best operability in terms of maneuverability arc. Favorable tentorial anatomy is the only limiting factor.

CONCLUSIONS

The supracerebellar transtentorial approach is able to provide access to the posterior fusiform gyrus via a minimally disruptive, anatomic, microsurgical corridor.

[The paramedian supracerebellar transtentorial approach to the mediobasal temporal region]

The mediobasal temporal region (MTR) is located near the brain stem and surrounded by the eloquent neurovascular structures. The supracerebellar transtentorial approach (STA) is safe access to the posterior MTR structures, however its use for resection of anterior MTR lesions still remains controversial. The article describes the technique and outcome of surgery for different MTR structures using STA.

MATERIAL AND METHODS

The paramedian STA was used in 18 patients (13 females and 5 males) for 7 years. Ten patients presented with glial MTR tumors, 3 patients with cavernomas, 2 patients with arteriovenous malformations (AVMs), 2 patients with intraventricular meningiomas, and 1 patient with mesial temporal sclerosis. The patient age ranged from 19 to 57 years. In 10 cases, lesions were localized on the left. Epilepsy was the leading symptom in 14 cases. Patients underwent preoperative high-resolution MRI, electroencephalography video monitoring before and after surgery, intraoperative corticography (if necessary), and postoperative CT and MRI.

RESULTS

Lesions were located in the anterior third of MTR in 5 patients, in the anterior and middle thirds in 2 patients, in the middle third in 5 patients, in the middle and posterior thirds in 2 patients, in the posterior third in 1 patient, in the anterior, middle, and posterior thirds in 1 patient, and in the ventricular triangle area in 2 patients. In all patients with intraventricular tumors, AVMs, and cavernous malformations and in 8 patients with glial MTR tumors, the lesions were totally resected. Two patients with intracerebral tumors underwent subtotal resection. A patient with intractable epilepsy and mesial temporal sclerosis underwent resection of the anterior two-thirds of the hippocampus and parahippocampal gyrus and, partially, amygdala using intraoperative corticography. There was no surgical mortality; 2 patients developed a transient neurological deficit, and 1 patient had a cerebellar hematoma that was successfully removed during surgery.

CONCLUSION

STA enables resection of lesions localized in all parts of the MTR, without damage to the surrounding nerve and vascular structures.

[Supracerebellar transtentorial approach to tumors of the posterior portions of the medial temporal region]

OBJECTIVE

Despite the advances in microsurgery, the choice of the most adequate approach to the posterior part of the medial temporal region (MTR) remains a very controversial issue. The supracerebellar transtentorial approach (STA) is considered as the most preferable one, since it provides the optimal balance between retraction, incision, and resection of the brain tissue. Here, we present our consecutive series of 20 patients who underwent STA surgery.

MATERIAL AND METHODS

Twenty patients with glial tumors affecting the posterior MTR underwent STA surgery between 2006 and 2014. The mean age of the patients was 20 years. Benign tumors were predominant (18 out of 20 cases).

RESULTS

Resection of the posterior and middle MTRs was conducted in 16 cases. The anterior MTR was accessed through STA in 1 patient only; in 2 patients, STA was combined with the infraoccipital approach. Cerebellar edema occurred in 4 patients, with hemiparesis persisting in one of the cases for 1 year after surgery. Of 8 patients with drug resistant epilepsy, the Engel class 1 or 2 outcome was achieved in 6 cases within 1 year after surgery.

CONCLUSION

STA provides an excellent surgical route to the posterior and middle MTR portions; however, the anterior MTR portions cannot be reached safely. The operative risks of STA increase as the surgeon proceeds with resection of the anterior MTR portions. Anterior MTR structures can be removed using a combination of the supracerebellar and infraoccipital transtentorial approaches or two-stage resection.

Endoscopic and Gravity-Assisted Resection of Medial Temporo-occipital Lesions Through a Supracerebellar Transtentorial Approach: Technical Notes With Case Illustrations

BACKGROUND

Traditional approaches to medial temporo-occipital intra-axial brain tumors carry the risk of visual or language deficits related to brain retraction or transgression of deep fiber tracts. To reduce these risks, the microscopic supracerebellar transtentorial approach with the patient in the sitting position has been previously described for lesions in relative proximity to the tentorium.

OBJECTIVE

We describe this approach performed with endoscopic tumor resection to allow better visualization and a more ergonomic operating position.

METHODS

Four consecutive patients harboring a medial temporo-occipital lesion are reported. All were operated on while in the sitting position using frameless navigation and a supracerebellar transtentorial approach. Tumor resection was performed by 2 surgeons with endoscopic visualization.

RESULTS

Pathologies included intraparenchymal metastatic melanoma, cavernous hemangioma, and ganglioglioma, as well as an intraventricular metastatic tumor. The distance from the tentorium to the lesion ranged from 1 to 4 mm. Gross total resection was achieved in 3 of the 4 patients. The patient with a metastatic melanoma had an intentional near-total resection given the tumor encasing a branch of the posterior cerebral artery. The patient with the intraventricular tumor sustained a small but symptomatic infarct of the lateral geniculate region, resulting in a visual field deficit.

CONCLUSION

This small series suggests that the endoscopic supracerebellar transtentorial approach with the patient in the sitting position can be a safe and effective approach for removing medial temporo-occipital lesions. It allows excellent tumor visualization, eliminates the need for brain retraction, minimizes parenchymal transgression, and improves surgical ergonomics. Significant experience in endoscopy and excellent neuroanesthesia support are recommended before undertaking this approach.

Lateral supracerebellar infratentorial approach for microsurgical resection of large midline pineal region tumors: techniques to expand the operative corridor

Pineal region tumors pose certain challenges in regard to their resection: a deep surgical field, associated critical surrounding neurovascular structures, and narrow operative working corridor due to obstruction by the apex of the culmen. The authors describe a lateral supracerebellar infratentorial approach that was successfully used in the treatment of 10 large (> 3 cm) midline pineal region tumors. The patients were placed in a modified lateral decubitus position. A small lateral suboccipital craniotomy exposed the transverse sinus. Tentorial retraction sutures were used to gently rotate and elevate the transverse sinus to expand the lateral supracerebellar operative corridor. This approach placed only unilateral normal structures at risk and minimized vermian venous sacrifice. The surgeon achieved generous exposure of the caudal midline mesencephalon through a "cross-court" oblique trajectory, while avoiding excessive retraction on the culmen. All patients underwent the lateral approach with no approach-related complication. The final pathological diagnoses were consistent with meningioma in 3 cases, pilocytic astrocytoma in 3 cases, intermediate grade pineal region tumor in 2 cases, and pineoblastoma in 2 cases. The entire extent of these tumors was readily reachable through the lateral supracerebellar route. Gross-total resection was achieved in 8 (80%) of the 10 cases; in 2 cases (20%) near-total resection was performed due to adherence of these tumors to deep diencephalic veins. Large midline pineal region tumors can be removed through a unilateral paramedian suboccipital craniotomy. This approach is simple, may spare some of the midline vermian bridging veins, and may be potentially less invasive and more efficient.

The supracerebellar-transtentorial approach to posteromedial temporal lesions in children with refractory epilepsy

OBJECT

Operations on tumors of the posteromedial temporal (PMT) region, that is, on those arising from the posterior parahippocampal, fusiform, and lingual gyri, are challenging to perform because of the deep-seated location of these tumors between critical cisternal neurovascular structures and the adjacent temporal and occipital cortexes. Traditional surgical approaches require temporal or occipital transgression, retraction, or venous sacrifice. These approaches may result in unintended complications that should be avoided. To avoid these complications, the supracerebellar-transtentorial (SCTT) approach to this region has been used as an effective alternative treatment in adult patients. The SCTT approach uses a sitting position that offers a direct route to the posterior fusiform and lingual gyri of the temporal lobe. The authors report the feasibility, safety, and efficacy of this approach, using a modified lateral park-bench position in a small cohort of pediatric patients.

METHODS

The authors carried out a retrospective case review of 5 consecutive patients undergoing a paramedian SCTT approach between 2009 and 2014 at the authors' institution.

RESULTS

The SCTT approach in the park-bench position was used in 3 boys and 2 girls with a mean age of 7.8 years (range 13 months to 16 years). All patients presented with a seizure disorder related to a tumor in a PMT region involving the parahippocampal and fusiform gyri of the left (n = 3) or right (n = 2) temporal lobe. No procedure-related complications were observed. Gross-total resection and control of seizures were achieved in all cases. Tumor classes and types included 1 Grade II astrocytoma, 1 pleomorphic xanthoastrocytoma, 1 ganglioglioma, and 2 glioneural tumors. None of the tumors had recurred by the mean follow-up of 22 months (range 1-48 months). Outcomes of epileptic seizures were excellent, with seizure symptoms in all 5 patients scoring in Engel Class IA.

CONCLUSIONS

The SCTT approach represents a viable option when resecting tumors in this region, providing a reasonable working corridor and low morbidity. The authors' experience in a cohort of pediatric patients demonstrates that complete resection of the lesions in this location is feasible and is safe when involving an approach that involves using a park-bench lateral positioning.

Keyhole supracerebellar transtentorial transcollateral sulcus approach to the lateral ventricle

BACKGROUND AND IMPORTANCE

Meningiomas of the lateral ventricles are commonly located in the atria. Surgical access to such tumors is challenging because of their deep location and proximity to critical neurovascular structures, particularly if situated on the dominant side. Although a number of approaches have been described in the literature, most carry the risk of postoperative neuropsychological, visual, or speech deficits, especially when operating on the dominant hemisphere. The supracerebellar transtentorial transcollateral sulcus (STTCS) approach offers the potential to circumvent functionally important structures, reducing the risk of these approach-related neurological deficits.

CLINICAL PRESENTATION

Two patients with dominant hemisphere trigonal meningiomas underwent surgical resection with the use of the STTCS approach. Neuronavigation was used to carefully plan the incision, craniotomy, and exposure, and also intraoperatively to orientate the operating surgeon at key steps, particularly when raising the tentorial flap in line with the tumor. Endoscopy was used to provide increased light intensity, an extended viewing angle, and higher magnification in comparison with a microscope. Specially designed tube-shaft instruments were also used to assist with manipulation through the narrow surgical corridor. In both cases, the tumors were fully resected without approach-related morbidity.

CONCLUSION

The STTCS approach provides good access to tumors located in the trigonal region, reducing the risk of iatrogenic language or visual field deficits. In dominant hemisphere lesions, in the hands of an experienced neurosurgeon, the STTCS approach is an effective alternative to existing techniques.

The extended supracerebellar transtentorial approach for resection of medial tentorial meningiomas

BACKGROUND

The supracerebellar transtentorial (SCTT) approach has been established as a safe corridor to access the posteriomedial basal temporal region. Previous reports have demonstrated the efficacy of this route in the resection of intrinsic tumors and small arteriovenous malformations. Only one report in the English literature has described its use to resect a medial tentorial meningioma.

METHODS

The authors discuss the relevant surgical anatomy of this approach and its advantages compared with more traditional routes, and illustrate its application to remove medial tentorial meningiomas through two operative cases with accompanying videos.

RESULTS

In illustrative case one, the patient recovered from surgery with no deficits. All his preoperative symptoms had resolved at 3-month follow-up. At the 4-year follow-up, MRI did not demonstrate any growth of the residual tumor. In case two, gross total resection was achieved and the patient did not suffer any postoperative language or visual deficit. At 2-year follow-up, no tumor recurrence was present.

CONCLUSION

The SCTT approach has a potential to safely access extra-axial lesions located around the medial tentorial incisura. As demonstrated in these two cases, the approach merits consideration in patients with tentorial meningiomas as an alternative to more widely utilized skull base approaches and subtemporal routes.

Occipital-posterior cerebral artery bypass via the occipital interhemispheric approach

Background:

The unavailability of the superficial temporal artery (STA) and the location of lesions pose a more technically demanding challenge when compared with conventional STA-superior cerebellar or posterior cerebral artery (PCA) bypass in vascular reconstruction procedures. To describe a case series of patients with cerebrovascular lesions who were treated using an occipital artery (OA) to PCA bypass via the occipital interhemispheric approach.

Methods:

We retrospectively reviewed three consecutive cases of patients with cerebrovascular lesions who were treated using OA-PCA bypass.

Results:

OA-PCA bypass was performed via the occipital interhemispheric approach. This procedure included: (1) OA-PCA bypass (n = 1), and combined OA-posterior inferior cerebellar artery and OA-PCA saphenous vein interposition graft bypass (n = 1) in patients with vertebrobasilar ischemia; (2) OA-PCA radial artery interposition graft bypass in one patient with residual PCA aneurysm.

Conclusions:

OA-PCA bypass represents a useful alternative to conventional STA-SCA or PCA bypass.

Medial posterior choroidal artery territory infarction associated with tumor removal in the pineal/tectum/thalamus region through the occipital transtentorial approach

OBJECT

Damage to the deep venous system, occipital lobe, and/or corpus callosum is well known to cause complications associated with the occipital transtentorial approach (OTA), but ischemic complications are not well documented. The authors investigated the high incidences of ischemic complications associated with removal of pineal/tectal/thalamic tumors through the OTA.

METHODS

Clinical records of 29 patients who underwent 31 surgeries using the OTA from December 2001 to May 2011 were retrospectively studied. Tumor locations were the pineal/tectal/thalamic region for 19, cerebellum for 7, and medial temporal lobe for 3.

RESULTS

Postoperative diffusion-weighted magnetic resonance images obtained within 72 h after surgery detected infarction in the tectal/splenial/thalamic region, presumably representing the medial posterior choroidal artery (MPChA) territory, in 10 patients. All these patients had tumor in the pineal/tectal/thalamic region. Deteriorated or newly developed eye symptoms including vertical gaze palsy tended to persist in these patients compared to those without ischemic complications.

CONCLUSIONS

A relatively high incidence of MPChA territory infarction was associated with removal of tumors in the pineal/tectal/thalamic region through the OTA. Eye symptoms often occurred post-surgery and tended to persist in these patients. Neurosurgeons must be aware of the possibility of MPChA territory infarction to further increase the safety of the OTA.

Interhemispheric approach to tumors of the posterior gyrus cinguli

OBJECTIVE

Posterior gyrus cinguli tumors are a well-defined group of tumors that pose considerable challenges in creating surgical access and manipulating adjacent eloquent areas (visual and motor). Here we report our 5-year experience in the surgical treatment of these tumors and describe tumor characteristics, surgical steps, critical aspects, and prognostic factors.

METHODS

This series comprises 37 patients operated on for glioma (high-grade in 28, low-grade in 9), often presenting with motor impairment (n=20), intracranial hypertension (n=15), seizures (n=11), and/or hemianopia (n=9). Preoperative assessment was performed with magnetic resonance imaging. Half of the tumors were more than 4 cm in size, and the majority presented secondary extension into the fronto-parieto-occipital area, the temporo-mesial area, and/or the corpus callosum. Positioning and assisted surgery were optimized in each patient based on preoperative planning.

RESULTS

The ipsilateral interhemispheric approach was elected in all cases. Tumor size and extension were significantly associated with the degree of tumor removal. Total removal was achieved in 25 patients (65%); 4 (10%) had persistent morbidity (visual or motor deficits). The occurrence of local and systemic complications was negligible.

CONCLUSIONS

Surgical treatment of posterior gyrus cinguli tumors can be safely approached via the interhemispheric route as it permits several beneficial operative maneuvers in selected cases.

The paramedian supracerebellar-transtentorial approach to the entire length of the mediobasal temporal region: an anatomical and clinical study

Object

The exploration of lesions in the mediobasal temporal region (MTR) has challenged generations of neurosurgeons to achieve an appropriate approach. To address this challenge, the extensive use of the paramedian supracerebellar-transtentorial (PST) approach to expose the entire length of the MTR, as well as the fusiform gyrus, was investigated.

Methods

The authors studied the microsurgical aspects of the PST approach in 20 cadaver brains and 5 cadaver heads under the operating microscope. They evaluated the features, advantages, difficulties, and limitations of the PST approach and refined the surgical technique. They then used the PST approach in 15 patients with large intrinsic MTR tumors (6 patients), tumor in the posterior fusiform gyrus with mediobasal temporal epilepsy (MTE) (1 patient), cavernous malformations in the posterior MTR including the fusiform gyrus (2 patients), or intractable MTE with hippocampal sclerosis (6 patients) from December 2007 to May 2010. Patients ranged in age from 11 to 63 years (mean 35.2 years), and in 9 patients (60%) the lesion was located on the left side.

Results

In all patients with neuroepithelial tumors or cavernous malformations, the lesions were completely and safely resected. In all patients with intractable MTE with hippocampal sclerosis, the anterior two-thirds of the parahippocampal gyrus and hippocampus, as well as the amygdala, were removed selectively through the PST approach. There was no surgical morbidity or mortality in this series. Three patients (20%) with high-grade neuroepithelial tumors underwent postoperative radiotherapy and chemotherapy but needed a second surgery for recurrence during the follow-up period. In all patients with MTE, antiepileptic medication could be decreased to a single drug at lower doses, and no seizure activity has occurred until this point.

Conclusions

The PST approach provides the surgeon precise anatomical orientation when exposing the entire length of the MTR, as well as the fusiform gyrus, for removing any lesion. This is a novel technique especially for removing tumors involving the entire MTR in a single session without damaging neighboring neural or vascular structures. This approach can also be a viable alternative for selective removal of the parahippocampal gyrus, hippocampus, and amygdala in patients with MTE due to hippocampal sclerosis.

Supracerebellar transtentorial approach—resection of the tentorium instead of an opening—to provide broad exposure of the mediobasal temporal lobe: anatomical aspects and surgical applications

Object

The aim of this study was to describe the surgical anatomy of the mediobasal aspect of the temporal lobe and the supracerebellar transtentorial (SCTT) approach performed not with an opening, but with the resection of the tentorium, as an alternative route for the neurosurgical management of vascular and tumoral lesions arising from this region.

Methods

Cadaveric specimens were used to illustrate the surgical anatomy of the mediobasal region of the temporal lobe. Demographic aspects, characteristics of lesions, clinical presentation, surgical results, follow-up findings, and outcomes were retrospectively reviewed for patients referred to receive the SCTT approach with tentorial resection.

Results

Ten patients (83%) were female and 2 (17%) were male. Their ages ranged from 6 to 59 years (mean 34.5 ± 15.8 years). All lesions (3 posterior cerebral artery aneurysms, 3 arteriovenous malformations, 3 cavernous malformations, and 3 tumors) were completely excluded or resected. After a mean follow-up period of 143 months (range 10–240 months), the mean postoperative Glasgow Outcome Scale score was 4.9.

Conclusions

Knowledge of the surgical anatomy provides improvement for microsurgical approaches. The evolution from a small opening to a resection of the tentorium absolutely changed the exposure of the mediobasal aspect of the temporal lobe. The SCTT approach with tentorial resection is an excellent alternative route to the posterior part of mediobasal aspect of the temporal lobe, and it was enough to achieve the best neurosurgical management of tumoral and vascular lesions located in this area.

The challenge of access to the pontomesencephalic junction: an anatomical study of lateral approach and exposure

We quantitatively compared relative merits of lateral approaches to the pontomesencephalic junction (PMJ): anterior petrosectomy, subtemporal transtentorial, posterior petrosectomy, and retrosigmoid transtentorial. In dissected cadaveric heads, lengths of exposure were measured anteriorly from CN V along the pontomesencephalic sulcus (PMS); posterosuperiorly along the lateral mesencephalic sulcus (LMS); and posteroinferiorly along the interpeduncular sulcus (IPS). Subtemporal transtentorial approach provided best anterior exposure along the PMS (23.8 ± 4.5 mm). Posterosuperior exposures were comparable for all approaches except anterior petrosectomy (limited). Posteroinferior exposure was most with subtemporal transtentorial approach (13.2 ± 2.8 mm). CN V entry/exit point was identified through all approaches, except for subtemporal transtentorial; shortest surgical depth with posterior petrosectomy was 43.7 ± 5.5 mm. PMS-LMS-IPS convergence point: reached through all approaches, except for anterior petrosectomy (limited); shortest surgical depth with posterior petrosectomy was 40.3 ± 4.3 mm. Anterior petrosectomy provides direct anterolateral views of the pons not afforded by subtemporal approach. Subtemporal transtentorial approach provides optimal posterolateral view to the PMJ and cerebellar peduncles. Retrosigmoid transtentorial approach offers wide exposure of the lateral surface, limited on the posteroinferior PMJ by the cerebellum. The small opening of posterior petrosectomy creates an awkward corridor to anterior PMJ targets but provides a direct and shortest route to the cerebellar peduncles.

Aneurysms of the posterior cerebral artery and approach selection in their microsurgical treatment: emphasis on the approaches: SAHEA and SCTTA

Aneurysms of the posterior cerebral artery (PCA) are infrequent and located in the central depth of the brain. Hence their optimal microsurgical management has not been discussed systematically, as institutions and/or neurosurgeons have only limited experience. The purpose of this communication is to report our considerations on this topic with emphasis on the selection of approaches by reviewing our 20 consecutive cases of PCA aneurysms out of more than 1,000 aneurysm patients seen over the past 15 years. Although the subtemporal approach appears to be prevalent in the literature, in our series we applied the pterional approach with or without selective extradural anterior clinoidectomy (SEAC) for P1, P1-P2 aneurysms, and either a selective amygdalohippocampectomy approach (SAHEA) or supracerebellar transtentorial approach (SCTTA) for P2 and P2-P3 aneurysms. Construction of an extracranial-intracranial EC-IC bypass, when necessary, in conjunction with parent artery occlusion or with trapping of aneurysms was adapted to selected approaches.

Microvascular anatomy of the medial temporal region: part 1: its application to arteriovenous malformation surgery

BACKGROUND

The medial temporal region (also called the temporomesial or mediobasal temporal region) is the site of the most complex cortical anatomy.

OBJECTIVE

To investigate the anatomic variability of the arterial supply and venous drainage of each segment of the medial temporal region (MTR), and to discuss and illustrate the implications of the findings for surgery of arteriovenous malformations (AVM) of the MTR.

METHODS

Forty-seven cerebral hemispheres and 10 silicon-injected cadaveric heads were examined using x3 to x40 magnification. Illustrative surgical cases of MTR AVMs were selected.

RESULTS

The anterior choroidal artery (AChA) gave rise to an anterior uncal artery in 83% of hemispheres and a posterior uncal or unco-hippocampal artery in 98%. The plexal segment of the AChA gave off neural branches in 38%. The MCA was the site of origin of anterior uncal, unco-parahippocampal, or anterior parahippocampal arteries in 94% of hemispheres. An anterior uncal artery arose from the internal carotid artery (ICA) in 45% of hemispheres. The posterior cerebral artery (PCA) irrigated the entorhinal area through its anterior parahippocampal or hippocampo-parahippocampal branches in every case. A PCA bifurcation was identified in 89% of hemispheres, typically at the middle segment of the MTR. The most common pattern of bifurcation was by division into posteroinferior temporal and parieto-occipital arterial trunks. The anterior segment of the basal vein had a predominant anterior drainage in 35% of hemispheres, and the middle segment had a predominant inferior drainage in 16%.

CONCLUSION

An understanding of the vascular variability of the MTR is essential for accurate microsurgical resection of MTR AVMs.

The posterior subtemporal keyhole approach combined with the transchoroidal approach to the ambient cistern: microsurgical anatomy and image-guided quantitative analysis

PURPOSE

The aim of this study is to describe microsurgical anatomy and to quantitatively analyze exposure using the posterior subtemporal keyhole (PSK) approach combined with the transchoroidal keyhole (TCK) approach to the ambient cistern.

METHODS

We determined the proper location of craniotomy of such combined keyhole approach on 16 sides of cadaver heads. The PSK approach and the TCK approach were performed in the same minicraniotomy to observe microanatomic features and to quantitatively measure exposure limits of the ambient cistern and related structures using image-guided system.

RESULTS

Some superficial and bone landmarks could be used to find the proper location of such combined minicraniotomy. In the PSK approach, the exposure distances of the trigeminal nerve and the anterior portion of the P2 segment (P2a) were 10.02 ± 0.76 mm and 16.32 ± 2.02 mm, respectively. The superior, inferior, anterior, and posterior exposure limit of brainstem from the intersection point of the lateral mesencephalic sulcus and pontomesencephalic sulcus was 7.5 ± 0.19 mm, 11.04 ± 0.27 mm, 15.72 ± 0.52 mm, and 10.16 ± 0.38 mm, respectively. In the TCK approach, the vertical distances between the taenia fimbriae and the lateral geniculate body without and with mild caudal retraction of the hippocampus were 5.28 ± 0.46 mm and 11.18 ± 0.57 mm, respectively. The linear exposure distances of the posterior portion of the P2 segment (P2p) or P3 segment were 12.14 ± 1.88 mm. Except of one case, the P2p could be exposed using the TCK approach. The midpoint of the medial edge of the parahippocampal gyrus on the coronal magnetic resonance images provides landmark to choose the appropriate approach.

CONCLUSIONS

The PSK combined with the TCK approach can simultaneously expose the lower and upper ambient cistern in a proper minicraniotomy.

Posterior interhemispheric transfalx transprecuneus approach to the atrium of the lateral ventricle: a cadaveric study

OBJECT

The posterior interhemispheric transprecuneus gyrus approach is one of the surgical routes that has been suggested to reach the atrium of the lateral ventricle. It has the advantage of avoiding the disruption of the optic radiations; however, it has a narrow working area that at times makes the execution of this approach rather challenging. The aim of this study was to test a modification of the approach that might create a better surgical angle and a wider corridor by accessing the atrium from the contralateral side after transection of the falx. The authors named this new approach the "posterior interhemispheric transfalx transprecuneus approach."

METHODS

The posterior interhemispheic transfalx transprecuneus approach was performed bilaterally on 6 fresh adult cadaveric specimens for a total of 12 procedures. Every head was held in the semisitting position and a parasagittal parietooccipital craniotomy on the contralateral side of the targeted ventricle was executed. The dura mater was opened and reflected based on the sagittal sinus. Then the falx was cut in a triangular fashion based on the inferior sagittal sinus. Using the parietooccipital artery and sulcus as landmarks, the contralateral precuneus gyrus was indentified, and a small area of the gyrus was transected to gain access to the atrium. A neuronavigational system was also used to conduct this approach. The working angle of this approach and other distances were measured.

RESULTS

The authors were able to visualize the ventricular atrium, posterior part of the temporal horn, pulvinar, and choroid plexus in all specimens. The temporal horn could be exposed for a length of 20-30 mm from the atrium. The working angle of the approach was better than that of the classic posterior interhemispheric transprecuneus approach with a mean value of 44.5° as opposed to 25.8°. The distance from the middle point of the corticotomy to the splenium ranged from 11 to 16 mm (mean 13.3 mm); the distance to the torcula, from 34 to 53 mm (mean 41.3 mm); and the distance to the atrium, from 22 to 31 mm (mean 25.7 mm).

CONCLUSIONS

Results of this study suggested that the proposed approach can expose the atrium and the posterior part of the temporal horn of the lateral ventricle with a wider surgical angle compared with the conventional homolateral posterior interhemispheric transprecuneus gyrus approach. Moreover, by minimizing the amount of brain retraction homolateral to the target, this approach could make navigation more accurate.

Posterior circulation EC-IC bypass via supracerebellar transtentorial SCTT approach applied in a young patient with congenital multiple occlusive cerebrovascular anomalies - case report and technical note

A case of remarkable vertebrobasilar insufficiency due to congenital multiple occlusive cerebro-vascular anomalies is presented. Anomalies are of the anterior and posterior circulation, presumably induced by "segmental vulnerability" and modified by infection of recurrent tonsillitis. Symptoms of repeated faintness and black-out attacks and deterioration of cognitive function compromised the quality of life considerably. Successful treatment was achieved by combination of a new type of posterior circulation revascularization procedure, namely occipital artery - superior cerebellar artery bypass via the supracerebellar transtentorial SCTT approach in the sitting position in combination with a standard superficial temporal artery STA-MCA bypass.

Comparative analysis of posterior approaches to the medial temporal region: supracerebellar transtentorial versus occipital transtentorial

OBJECTIVE

Cortical and subcortical lesions in the posterior portion of the medial temporal region (MTR) are routinely resected through the supracerebellar transtentorial (SCTT) or occipital transtentorial (OCTT) route. We compared the exposures provided by these 2 approaches to this region.

METHODS

Eight sides of injected cadaver heads were dissected using both approaches. Identical deep target points were collected for SCTT and OCTT routes while accepting variations in initial exposures. Data gathered with the P2-P3 junction as an apex created 2 adjoining triangles (anterior and posterior) in the middle and posterior MTR. Real, projected, and freedom areas were calculated for comparison.

RESULTS

The approach-related differences for the real and projected areas were expressed in relative values. There were no differences in the percentage of projected area between the 2 approaches (e.g., working in the middle of the opening, anterior triangle: SCTT, 5.2 +/- 4.1%; OCTT, 8.4 +/- 5.6%; P = 0.313; posterior triangle: SCTT, 8.6 +/- 3.8%; OCTT, 8.8 +/- 6.3%; P = 0.937). Freedom areas for the SCTT approach were smaller than those for the OCTT approach at many deep points (P < 0.05), except in the posterior margin of the MTR (P = 0.21).

CONCLUSION

The SCTT and OCTT approaches provided no differences in surgical views to the MTR. However, the OCTT approach provides a wider corridor for surgical manipulation compared with the SCTT approach in most parts of the MTR. These data may help neurosurgeons to select a favorable approach to specific lesions of the MTR.

Supracerebellar transtentorial transcollateral sulcus approach to the atrium of the lateral ventricle: microsurgical anatomy and surgical technique in cadaveric dissections

BACKGROUND

Access to lesions located in the atrium of the lateral ventricle without causing neurologic deficit can be challenging. Here, we demonstrate the supracerebellar transtentorial transcollateral sulcus (STTS) approach as an alternative route to the atrium of the lateral ventricle using anatomical dissections in cadavers.

METHODS

Suboccipital craniotomy with extension above the transverse sinus was performed in 5 arterial and venous latex-injected cadaveric heads (10 hemispheres). After the dural opening, arachnoidal dissection of the supracerebellar space was performed, and the tentorium cerebelli was cut from lateral to medial. This revealed the parahippocampal and fusiform gyri and collateral sulcus (CS). The distance from the CS to the atrium was measured.

RESULTS

The atrium of the lateral ventricle was entered through the CS in each specimen. The cerebral hemispheres were removed from each cadaveric specimen, and dissections were performed. The distance from the CS to the atrium was 1.30 cm on the right side and 1.31 cm on the left. The CS was bifurcated in 62% of the hemispheres, whereas it was single in 38%. Through this approach, only the "u" fibers of the CS were damaged, and the fibers of the optic radiation in the inferolateral wall of the atrium were preserved.

CONCLUSION

The STTS approach may be an effective alternative approach to lesions located in the medioposterior aspect of the atrium of the lateral ventricle in selected cases. Further clinical studies to evaluate the safety and efficacy of this approach are needed.

Microsurgical Anatomy of the Supracerebellar Transtentorial Approach to the Posterior Mediobasal Temporal Region: Technical Considerations With a Case Illustration

Objective:

Surgical access to the posterior portion of the mediobasal temporal lobe presents a formidable challenge to neurosurgeons, and much controversy still exists regarding the selection of the surgical approach to this region. The supracerebellar transtentorial (SCTT) approach to the posterior mediobasal temporal region can be used as an alternative to the subtemporal or transtemporal approaches. The aim of this study was to demonstrate the surgical anatomy of the SCTT approach and review the gyral, sulcal, and vascular anatomy of the posterior mediobasal temporal lobe. The use of this approach in the resection of a ganglioglioma located in the left posterior parahippocam-pal gyrus is illustrated.

Methods:

The SCTT approach to the posterior parahippocampal gyrus was performed on three silicone-injected cadaveric heads. The gyral, sulcal, and arterial anatomy of the posterior mediobasal temporal lobe was studied in six formalin-fixed injected hemispheres.

Results:

The SCTT approach provided a direct path to the posterior mediobasal temporal lobe and exposed the posterior parahippocampal gyrus as well as the adjacent gyri in all of the cadaveric specimens. Through this approach, gross total resection of the ganglioglioma was possible in our patient.

Conclusion:

The SCTT approach provided a viable surgical route to the posterior mediobasal temporal lobe in the cadaveric studies. This approach provides an advantage over the subtemporal and transtemporal routes in that there is less temporal lobe retraction.

Microsurgical approaches to the medial temporal region: an anatomical study

OBJECTIVE

To describe the surgical anatomy of the anterior, middle, and posterior portions of the medial temporal region and to present an anatomic-based classification of the approaches to this area.

METHODS

Twenty formalin-fixed, adult cadaveric specimens were studied. Ten brains provided measurements to compare different surgical strategies. Approaches were demonstrated using 10 silicon-injected cadaveric heads. Surgical cases were used to illustrate the results by the different approaches. Transverse lines at the level of the inferior choroidal point and quadrigeminal plate were used to divide the medial temporal region into anterior, middle, and posterior portions. Surgical approaches to the medial temporal region were classified into four groups: superior, lateral, basal, and medial, based on the surface of the lobe through which the approach was directed. The approaches through the medial group were subdivided further into an anterior approach, the transsylvian transcisternal approach, and two posterior approaches, the occipital interhemispheric and supracerebellar transtentorial approaches.

RESULTS

The anterior portion of the medial temporal region can be reached through the superior, lateral, and basal surfaces of the lobe and the anterior variant of the approach through the medial surface. The posterior group of approaches directed through the medial surface are useful for lesions located in the posterior portion. The middle part of the medial temporal region is the most challenging area to expose, where the approach must be tailored according to the nature of the lesion and its extension to other medial temporal areas.

CONCLUSION

Each approach to medial temporal lesions has technical or functional drawbacks that should be considered when selecting a surgical treatment for a given patient. Dividing the medial temporal region into smaller areas allows for a more precise analysis, not only of the expected anatomic relationships, but also of the possible choices for the safe resection of the lesion. The systematization used here also provides the basis for selection of a combination of approaches.

Surgery for temporal mediobasal tumors: experience based on a series of 235 patients

OBJECTIVE

To describe the clinical characteristics, diagnosis, various approaches, and outcomes in a retrospective review of a large series of temporomediobasal (TMB) tumors.

METHODS

Charts from 235 patients with TMB tumors were identified from the glioma and epilepsy surgery database and from the electronic operations log. Preoperative magnetic resonance imaging scans were available for all patients and postoperative follow-up was available for 155 of these patients (mean follow-up period, 59 mo; range, 2-172 mo). Preoperative symptoms, approaches, technical problems, and surgical complications are described.

RESULTS

Two hundred and thirty-five patients with intra-axial TMB tumors (mean age, 35 yr) were collected during an 11-year period. The largest tumor groups were astrocytomas (38.0%), gangliogliomas (29.8%), dysembryoplastic neuroepithelial tumor (11.1%), and glioblastomas (11.1%). The most frequent tumor location was the mesial Type A tumor (45.1%), with this type also showing the highest proportion of benign (World Health Organization Grades I and II) histological features (91.3%). Of all tumors, 76.2% were benign. Larger tumor size was associated with higher frequency of malignant histopathological findings. The leading symptom was epilepsy in 91% of patients, followed by drug-resistant epilepsy in 71.5%. Significant preoperative neurological deficits, such as hemiparesis or aphasia, were seen in 3.8% of the patients; another 12% had visual field deficits. Thirty-eight patients with low-grade tumors had undergone surgery previously. Several surgical approaches were chosen: transsylvian in 28%, anterior two-thirds temporal lobe resection in 23%, temporal pole resection in 15.3%, subtemporal in 19%, and transcortical in 6%. The most frequent neurological complications were transient: dysphasia (4.2%), hemiparesis (5%), and oculomotor disturbance (2.5%). Permanent nonvisual neurological complications occurred in fewer than 2% of the patients and significant new hemianopic defects were found in another 5.4% of the patients. The most severe complication was one intraoperative internal carotid artery lesion. One patient died.

CONCLUSION

Small tumor size, magnetic resonance imaging, and microsurgery have made resection of mostly benign TMB tumors possible in a large number of patients. This series supports the conclusion that these tumors can be operated on with a relative degree of safety for the patient, provided that the anatomy of the mesial temporal lobe and the variety of approaches are well known to the surgeon. However, because of the complex anatomic structures in the vicinity, transient neurological deterioration is not infrequent and certain neurological disturbances (e.g., quadrantanopia) even seem to be unavoidable, whereas permanent significant deficits are rare.

Posterior interhemispheric approach: surgical technique, application to vascular lesions, and benefits of gravity retraction

OBJECTIVE

To review an experience with the posterior interhemispheric approach applied to vascular lesions in the posterior midline, to examine the effects of patient position and gravity retraction of the occipital lobe, and to identify circumstances requiring increased exposure by sectioning the falx and tentorium.

METHODS

During a 6.5-year period, 46 posterior interhemispheric approaches were performed to treat 28 arteriovenous malformations, 10 dural arteriovenous fistulae, seven cavernous malformations, and one posterior cerebral artery aneurysm. Twenty-three patients were positioned prone and 23 patient were positioned laterally.

RESULTS

A standard posterior interhemispheric approach was used in 38 patients, and the occipital bitranstentorial/falcine approach was used in seven patients. A contralateral occipital transfalcine approach was used with one thalamic cavernous malformation. All lesions were resected completely and/or obliterated angiographically, with good neurological outcomes in 83% of patients and no operative mortality. Blood loss was lower, operative durations were shorter, postoperative cerebral edema was decreased, and visual outcomes were improved in patients positioned laterally.

CONCLUSION

The posterior interhemispheric approach, without additional dural cuts, is appropriate for most vascular lesions in the posterior midline. Gravity retracts the occipital lobes when patients are positioned laterally, enhancing operative exposure and reducing morbidity. Extension of the posterior interhemispheric approach to a transtentorial or transfalcine approach is required for falcotentorial dural arteriovenous fistulae and vein of Galen arteriovenous malformations, but is not usually necessary with cavernous malformations or other arteriovenous malformations.

Revascularizing the upper basilar circulation with saphenous vein grafts: operative technique and lessons learned

BACKGROUND

The purpose of this study was to report our operative technique and lessons learned using saphenous vein conduits to revascularize the rostral basilar circulation (ie, bypass to the posterior cerebral or superior cerebellar arteries). We also review the evolution of this technique for the treatment of vertebrobasilar insufficiency (VBI) and complex posterior fossa aneurysms.

METHODS

Data were collected retrospectively for 8 consecutive patients undergoing rostral basilar circulation saphenous vein bypass grafts at our institution between 1989 and 2004 for the treatment of VBI or in conjunction with Hunterian ligation of complex posterior circulation aneurysms. The indications for treatment, pre- and postoperative neurologic status, angiographic results, operative complications, and long-term clinical outcomes were analyzed for each patient.

RESULTS

With clinical and angiographic follow-up ranging from 3 months to 15 years, 7 of 8 bypasses remained patent, 3 of 3 aneurysms remained obliterated, and 4 of 5 patients with VBI experienced resolution of their preoperative symptoms. There were no surgery-related deaths, but 2 patients did experience major neurologic morbidity. The outcomes for the 217 total patients reported in the literature were as follows: 135 excellent (62%), 26 good (12%), 30 poor (14%), and 26 dead (12%).

CONCLUSIONS

Despite the risk of serious neurologic complications with this procedure, when one considers the natural history of untreated patients, saphenous vein revascularization of the rostral basilar circulation remains an acceptable option. Although surgical technique has varied, patient selection criteria, graft patency, and patient outcomes have been relatively constant over the past 25 years.

Surgical approaches to the atrium of the lateral ventricle: microsurgical anatomy

BACKGROUND

Managing lesions situated in the atrium of the lateral ventricle remains a challenging neurosurgical problem. The purposes of this study were to examine the microsurgical anatomy of the atrium of the lateral ventricle and the optic radiation and to define the differences in the exposure obtained by various surgical approaches.

METHODS

Fifteen adult cadaveric specimens were studied using magnification x3 to x40 after perfusion of the arteries and veins with colored silicone. The microsurgical anatomy of the atrium of the lateral ventricle was examined. The relationship between the optic radiation and the atrium was studied using the white matter fiber dissection technique. Surgical approaches to the atrium of the lateral ventricle were examined in stepwise dissection.

RESULTS

The medial and inferior walls of the atrium were free from optic radiation fibers. Surgical approaches to the atrium of the lateral ventricle are divided into 3 routes: (1) anterior approach: transsylvian approach, (2) posterior approaches: posterior transcortical, posterior transcallosal, occipital, and supracerebellar transtentorial approaches, and (3) lateral approaches: transtemporal and subtemporal approaches.

CONCLUSION

Knowledge of the microsurgical anatomy of the atrium of the lateral ventricle and surrounding vital structures and the choice of an appropriate surgical approach will help surgeons perform safe and minimally invasive surgery.