Supracerebellar transtentorial approach to posterior temporomedial structures

Surgical anatomy of supratentorial midline lesions

Object

In this paper the authors correlate the surgical aspects of deep median and paramedian supratentorial lesions with the connective fiber systems of the white matter of the brain.

Methods

The cerebral hemispheres of 10 cadaveric brains were dissected in a mediolateral direction by using the fiber dissection technique, corresponding to the surgical approach.

Conclusions

This study illuminates the delicacy of the intertwined and stratified fiber laminae of the white matter, and establishes that these structures can be preserved at surgical exploration in patients.

Three-dimensional Computed Tomography Angiography of the Galenic System for the Occipital Transtentorial Approach

The venous variations of the galenic system were evaluated using three-dimensional computed tomography angiography (3D-CTA) to assess the influence on the occipital transtentorial approach in 150 patients who underwent 3D-CTA as a routine screening examination for cerebrovascular diseases. The variations of the vein of Galen with its tributaries, the tentorial sinus, and the veins around the tentorium were evaluated in multiple intensity projections and stereoscopic images. The angle between the vein of Galen and the straight sinus was 67.1 +/- 31.9 degrees (mean +/- SD). Observation of the pineal body from the direction of the approach tended to extend to the quadrigeminal bodies in acute angle cases, and to the third ventricle in obtuse angle cases. Bilateral internal cerebral veins (ICVs) joined in the anterior portion were associated with a long vein of Galen, or in the posterior portion with a short vein of Galen. The distance between the bilateral ICVs was 4.66 +/- 2.28 mm (mean +/- SD), and the shape of the space could be classified as spindle, parallel, hairpin, and round types. The basal vein could be classified into well-developed, hypoplastic, hardly recognized, and mimicking two basal veins because the tributary did not join but ran parallel to the basal vein. The drainage pathways lead to the anterior or posterior portion of the vein of Galen, the ICV, the tentorial sinus, and the superior petrosal sinus. The various types of the tentorial sinus and primitive tentorial sinus which might be sacrificed during section of the tentorium were confirmed. The inferior cerebral vein draining to the tentorial sinus could be seen. 3D-CTA could also demonstrate the presence, the course, and the drainage points of the internal occipital vein, the precentral cerebellar vein, the posterior pericallosal vein, and so on. 3D-CTA is useful to evaluate the variations of the venous system and the relationship with the tumor, and for preoperative simulation and intraoperative navigation of the occipital transtentorial approach.

MICROSURGICAL APPROACHES TO THE PERIMESENCEPHALIC CISTERNS AND RELATED SEGMENTS OF THE POSTERIOR CEREBRAL ARTERY: COMPARISON USING A NOVEL APPLICATION OF IMAGE GUIDANCE

OBJECTIVE

To describe the exposure obtained through six approaches to the perimesencephalic cisterns with an emphasis on exposure of the posterior cerebral artery and its branches.

METHODS

Dissections in 12 hemispheres exposed the crural, ambient, and quadrigeminal cisterns and related segments of the posterior cerebral artery. A Stealth Image Guidance workstation (Medtronic Surgical Navigation Technologies, Louisville, CO) was used to compare the approaches.

RESULTS

The transsylvian approach exposed the interpeduncular and crural cisterns. The subtemporal approach exposed the interpeduncular and crural cisterns as well as the lower half of the ambient cistern. Temporal lobe retraction and the position of the vein of Labbé limited exposure of the quadrigeminal cistern. Occipital transtentorial and infratentorial supracerebellar approaches exposed the quadrigeminal and lower two-thirds of the ambient cistern. Transchoroidal approaches exposed the posterior third of the crural cistern, the upper two-thirds of the ambient cistern, and the proximal quadrigeminal cistern. Transchoroidal approaches exposed the posterior portion of the P2 segment (P2p) in 9 of 10 hemispheres and were the only approaches that exposed the lateral posterior choroidal arteries and the plexal segment of the anterior choroidal artery. Occipital transtentorial and infratentorial supracerebellar approaches provided access to the P3 segment in all cases and exposed the P2p segment in 4 of 10 hemispheres. The subtemporal approach provided access to the cisternal and crural segments of the anterior choroidal and medial posterior choroidal arteries and exposed the P2p segment in 3 of 10 hemispheres.

CONCLUSION

Surgical approaches to lesions of the perimesencephalic cisterns must be tailored to the site of the pathological findings. The most challenging area to expose is the upper half of the ambient cistern, particularly the P2p segment of the posterior cerebral artery.

Surgical approaches to posterior third ventricular tumors

A variety of surgical approaches to the posterior third ventricle and pineal region exist. The choice of approach is influenced by the exact location of the lesion, its expected pathologic findings, and the comfort level of the operating surgeon with the approach that is being considered. For most pineal region masses that are situated in the midline below the deep venous system, we favor the supracerebellar-infratentorial approach in the sitting position. For pineal region lesions that displace the deep venous system inferiorly or have significant lateral extension, we prefer the occipital-transtentorial approach in the three-quarter prone or sitting position. For lesions that are truly in the posterior third ventricle without extension posterior to the splenium, we prefer the interhemispheric-transcallosal approach in the lateral position.

Small petrosal approach to the middle portion of the mediobasal temporal region: technical case report

BACKGROUND

The mediobasal temporal region has been divided into three portions: anterior, middle, and posterior. Surgical access, especially to the middle portion, presents a formidable challenge to neurosurgeons, and much controversy still exists regarding the selection of the surgical approach to this region.

CASE REPORT

We used the small petrosal approach to the middle portion of the mediobasal temporal region in a patient with intractable seizures caused by a cavernous angioma in this region. Using this approach, we selectively removed the lesion without postoperative deficits.

CONCLUSIONS

The small petrosal approach was found to be useful and safe as an alternative technique for selective removal of the lesion in the middle portion of the mediobasal temporal region.

Presurgical evaluation and surgical treatment of medically refractory epilepsy

Thanks to today's modern imaging examination techniques and especially to the common use of intracranial electrodes for localizing seizure foci, more and more patients with partial epilepsy can be treated microsurgically. The results of such neurosurgical therapies are very good, particularly in mesial temporal lobe epilepsy. In recent years, good results (60-70% seizure freedom) have also been achieved in extratemporal epilepsy surgery, so that such procedures can now be recommended for carefully selected patients. In this review, presurgical evaluations and the different surgical approaches are presented.

Strategies for surgical management of cerebral aneurysms of special location, size and form--approach, technique and monitoring

Special strategies are mandatory for optimal surgical management of aneurysms of special location, size and form. Approaches of extradural selective anterior clinoidectomy, partial occipital condylectomy, transpetrosal approach by anterior petrosectomy and supracerebellar transtentorial approach are discussed among them. Furthermore various types of temporary and permanent clipping procedures are discussed along with mention of intraoperative monitoring.

Comparison of posterior approaches to the posterior incisural space: microsurgical anatomy and proposal of a new method, the occipital bi-transtentorial/falcine approach

OBJECTIVE

Direct surgical approaches to the posterior incisural space, including the pineal region, remain as challenges for neurosurgeons. The purposes of this study were 1) to compare the surgical views in the various posterior approaches to the posterior incisural space and 2) to propose a new approach, which is a modification of the occipital transtentorial approach.

METHODS

Ten adult cadaveric specimens (20 sides) were studied, using x3 to x40 magnification, after perfusion of the arteries and veins with colored silicone. Intraoperative views in the posterior approaches to lesions were examined in stepwise dissections. In addition, the efficacy of the occipital bi-transtentorial/falcine approach was studied.

RESULTS

The posterior incisural space has a roof, a floor, and anterior and lateral walls and extends backward to the level of the tentorial apex. The operative views defined by each approach differ in the extent to which they allow observation of the anatomic structures in the posterior incisural space. The occipital bi-transtentorial/falcine approach permits better observation of the contralateral half of the quadrigeminal cistern.

CONCLUSION

Precise surgical anatomic knowledge of each approach is required for the treatment of lesions in the posterior incisural space, because the operative fields obtained with different approaches differ significantly. The occipital bi-transtentorial/falcine approach provides greater contralateral exposure of the posterior incisural space than does the occipital transtentorial approach.

Comparison of different infratentorial-supracerebellar approaches to the posterior and middle incisural space: a cadaveric study

OBJECT

The purpose of this investigation was to describe and compare through cadaveric dissection the microsurgical exposure afforded by the median, paramedian, and extreme-lateral infratentorial-supracerebellar approaches to the posterior and middle incisural space.

METHODS

The median, paramedian, and extreme-lateral infratentorial-supracerebellar approaches were performed in 10 embalmed cadaveric heads by using standard microneurosurgical methods; each approach was executed a minimum of five times. The dissections were performed in a stepwise fashion, comparing the exposure afforded by each surgical route and highlighting the relationships among the targeted neurovascular structures. Exposure of the dural sinuses and transection of the tentorium were also evaluated in relation to the degree of exposure achieved. The median infratentorial-supracerebellar route provides direct exposure of the posterior incisural space, although the culmen represents a relative obstacle to exposure of the lower quadrigeminal plate. The paramedian variant allows a more lateral perspective on the posterolateral brainstem surface at the level of the middle incisural space, in addition to exposing the homolateral collicular plate. The extreme-lateral corridor widens the exposure of the paramedian approach to include the anterolateral brainstem surface, offering a complete view of the cisternal space surrounding the middle incisural space. Complete, constant exposure and retraction of the dural sinuses facilitated the surgical exposure.

CONCLUSIONS

The infratentorial-supracerebellar approaches allow safe circumferential exposure of the posterior and middle incisural space. Choosing among different variants allows the surgeon to reach selected areas, with the midline variant being best for exposure of the posterior incisural space, and the paramedian and extreme-lateral variants being best for reaching the posterior and the anterior part of the middle incisural space, respectively. The more lateral the approach, the more anterior and multiangled the exposure gained. Complete, constant exposure and retraction of the dural sinuses improves the exposure. Accurate knowledge of the regional anatomy is mandatory.

Spinal cord injury without radiographic abnormality: results of the National Emergency X-Radiography Utilization Study in blunt cervical trauma

BACKGROUND

The purpose of this study was to better define the incidence and characteristics of patients with spinal cord injury without radiographic abnormality (SCIWORA), using the database of the National Emergency X-Radiography Utilization Study (NEXUS).

METHODS

This was a prospective, observational study of blunt trauma patients in 21 U.S. medical centers undergoing plain cervical radiography. SCIWORA was defined as spinal cord injury demonstrated by magnetic resonance imaging, when a complete, technically adequate plain radiographic series revealed no injury.

RESULTS

Of the 34,069 patients entered, there were 818 (2.4%) with cervical spine injury, including 27 (0.08%) patients with SCIWORA. Over 3,000 children were enrolled, including 30 with cervical spine injury, but none had SCIWORA. The most common magnetic resonance imaging findings among SCIWORA patients were central disc herniation, spinal stenosis, and cord edema or contusion. Central cord syndrome was described in 10 cases.

CONCLUSION

In the large NEXUS cohort, SCIWORA was an uncommon disorder, and occurred only in adults.

Volumetric stereotaxy and the supratentorial occipitosubtemporal approach in the resection of posterior hippocampus and parahippocampal gyrus lesions

OBJECTIVE

Resection of intracranial tumors in the posterior hippocampus and the parahippocampal gyrus can be associated with significant morbidity because of the parenchymal resection and the cortical retraction often required in gaining access to this infrequently explored region. With the use of image guidance, the occipitosubtemporal (OST) approach requires neither lateral cortical resection nor the placement of brain retractors to gain surgical access to the posterior hippocampus and the parahippocampal gyrus, and this approach is associated with a high rate of gross total tumor resection.

METHODS

The computer-assisted volumetric stereotactic OST approach was used to resect 40 posterior hippocampus and parahippocampal gyrus tumors in 34 consecutive patients during an 8-year period. Patient, radiographic, and surgical outcome data were collected retrospectively.

RESULTS

The series included operations in 25 men and 15 women, and the patients' average age was 40.3 years (range, 15-69 yr). Twenty-five of the 40 procedures were performed to remove lesions in the dominant hemisphere, and previous craniotomies for resection had been performed in 12 of 40 cases. In 38 of 40 cases, histopathological analysis revealed a glial neoplasm, and 50% of these tumors were high-grade lesions. Preoperatively, 23 patients were neurologically intact before 40 procedures, whereas visual field deficits were noted in 7 patients, mild hemiparesis was documented in 4 patients, and other neurological deficits were present in 9 patients. An excellent outcome (Glasgow Outcome Scale Grade 5) was noted after 38 (95%) of the 40 computer-assisted volumetric stereotactic OST procedures. Permanent postoperative hemiparesis (Glasgow Outcome Scale Grade 4) occurred after one procedure, and a second patient, despite being neurologically unchanged postoperatively and despite having had an optimal tumor resection, died on postoperative Day 33 (Glasgow Outcome Scale Grade 1). Complete resection of the preoperatively defined tumor volume was noted on postoperative gadolinium-enhanced magnetic resonance imaging examinations after 39 (97.5%) of the 40 procedures. The average duration of clinical follow-up was 15.9 months (range, 0.5-67 mo).

CONCLUSION

We think that the OST approach is well suited to the resection of tumors in the posterior hippocampus and the parahippocampal gyrus. By allowing the neurosurgeon to avoid unnecessary brain resection and retraction, this approach reduces the risk of injury to important lateral temporal and occipital lobe cortex and tracts. In addition, the resection of a posterior hippocampus or parahippocampal gyrus mass with the OST approach relieves temporal horn entrapment. Computer-assisted volumetric stereotaxy helps the neurosurgeon to maintain precise spatial and anatomic orientation and accurately delineates the margin between the tumor and the surrounding neural tissue.

Paramedian supracerebellar transtentorial approach for a medial tentorial meningioma with supratentorial extension: technical case report

OBJECTIVE AND IMPORTANCE

The choice of surgical approach to treat medial tentorial meningiomas is crucial and sometimes difficult to make. Although the subtemporal approach is most commonly used for lesions that extend mostly supratentorially, it risks injury to the vein of Labbé or the veins coursing along the subtemporal surface. To avoid venous injury, a medial tentorial meningioma was removed transtentorially through the infratentorial space via the paramedian supracerebellar transtentorial (PSCTT) approach.

CLINICAL PRESENTATION

A 35-year-old right-handed woman presented with a generalized convulsion. Magnetic resonance imaging scans revealed a left medial tentorial meningioma with supratentorial extension at the dominant hemisphere. The main venous drainage route from the ipsilateral temporal lobe was a sphenopetrosal vein.

INTERVENTION

An operation was performed with the patient in a sitting position, and the tumor was resected totally via the paramedian supracerebellar transtentorial approach without perioperative complications.

CONCLUSION

The paramedian supracerebellar transtentorial approach is useful for supratentorially located medial tentorial meningiomas without retraction of the temporal lobe and without damage to the vein of Labbé or the sphenopetrosal vein.