Transcallosal removal of lesions affecting the third ventricle: an anatomic and clinical study

Transcallosal Retroforniceal Transchoroidal Approach: To the Posterior Third Ventricle and Beyond

BACKGROUND

The transcallosal retroforniceal transchoroidal approach represents an advanced neurosurgical technique that allows access to lesions located within the posterior third ventricle and mesencephalon. It relies on a comprehensive understanding of microsurgical anatomy and embryology, integrating modern neurosurgical operative techniques to minimize retraction and injury to the normal neuronal structures.

METHODS

We report the cases of 2 patients undergoing treatment via this approach, one presenting with a thalamic cavernoma and the other with cystic low-grade glioma of the midbrain.

RESULTS

In these 2 cases, the decision to use the transcallosal approach was mainly due to improved trajectory, gravitational retraction of the hemisphere, and improved delivery of the lesion into the operative field by gravity alone.

CONCLUSIONS

Through a detailed description of the surgical approach and anatomy, we illustrate the feasibility of the transcallosal retroforniceal transchoroidal approach for accessing lesions located deeply in the brain.

Surgical Approaches to the Third Ventricle: An Update

The third ventricle is located in the deepest part of the brain and is delimited by both telencephalic and diencephalic structures. Its location makes every surgical procedure inside or around it quite challenging, due to the distance from the surface to the fragility of the neurovascular structures that is necessary to dissect before entering its cavity and to the narrow surgical corridors through which it is necessary to work. Its geometric localization inside the cranial cavity and the anatomical relationship with the interhemispheric fissure offers nevertheless to the surgeon an impressive variety of surgical approaches, which allow to reach every millimeter of the third ventricle lumen. Mastering properly all these approaches requires an impressive anatomical knowledge, the best available technology, and most refined technical skills, making the surgery of the third ventricle a point of excellence in the evolution of each neurosurgeon. The development of neuronavigation and neuroendoscopy has been a revolution in neurosurgery in the last 20 years and offered special advantages for the surgery of the third ventricle. In fact, the narrow corridors of approach make the precision of the neuronavigation and the enlightenment and magnification of the neuroendoscopy especially useful to reach the third ventricle cavity and working inside or around it. This chapter reviews the history of the surgery of the third ventricle and offers an update of the variety of surgical corridors identified and of the technology now available to properly work through them and inside the third ventricle cavity.

Expanded Transsphenoidal Trans-Lamina Terminalis Approach to Tumors Extending Into the Third Ventricle: Technique Notes and a Single Institute Experience

Object

The trans lamina terminalis approach (TLTA) has been described as a way to remove third ventricular tumors. The aim of this paper was to analyze the feasible outcomes of TLTA applied to tumors extending into the third ventricle in our institute.

Methods

Suprasellar tumors (n = 149) were treated by the extended endonasal approach from September 2019 to December 2020 in Beijing Tiantan Hospital. Eleven of the tumors were treated by TLTA or TLTA via the trans-chiasm-pituitary corridor (TCPC). The surgical technique notes of TLTA were described and indications and outcomes of the approach were analyzed.

Results

There were 11 patients enrolled in the study, six with papillary craniopharyngiomas, two with adamantinomatous craniopharyngiomas, one with a germinal cell tumor (GCT), one with cavernous malformation and one with chordoid glioma. Four of the patients received a radical resection by TLTA alone, while seven of them received TLTA via the TCPC. Gross total resection was achieved in eight patients (72.7%), and partial resection in three patients (27.3%). Visual function was improved in four of the 11 patients (36.4%), was unchanged in five patients (45.5%), and deteriorated in two patients (18.2%). New-onset hypopituitarism occurred in seven patients (63.3%) and new-onset diabetes insipidus occurred in two patients (18.2%). Electrocyte imbalance were observed in six patients (54.5%) at post-operative week 2. There were no surgery-related deaths or cerebrospinal fluid leaks. Postoperative intracranial infection was observed in one patient (9.1%), and during the follow-up period, tumor recurrence occurred in one patient (9.1%).

Conclusion

The expanded TLTA provides a feasible suprachiasm corridor to remove tumors extending into the third ventricle, especially for craniopharyngiomas. Sound understanding of the major strengths and limitations of this approach, as well as strategies for complication avoidance, is necessary for its safe and effective application.

Surgical approaches for resection of third ventricle colloid cysts: meta-analysis

Although outcome studies and systematic reviews have been published on the surgical treatment of third ventricle colloid cysts (TVCC), there are no meta-analyses that compare the outcomes for various surgical approaches. This meta-analysis assesses the outcomes and complications for transcortical, transcallosal, and endoscopic surgical approaches used to excise TVCCs. A meta-analysis of surgically excised TVCCs was performed with an assessment of outcome for transcortical, transcallosal, and endoscopic approaches. A random-effects model analyzed the extent of surgical excision. The analysis included reports that compared at least two of these surgical approaches, for a total of 11 studies comprising a population of 301 patients. The transcortical approach was associated with a higher incidence of complete excision compared to the endoscopic approach (OR = 0.137, p = 0.041), with no significant differences observed between transcortical and transcallosal approaches, and between transcallosal and endoscopic approaches. Comparison between endoscopic and pooled microsurgical approaches was also insignificant (OR = 0.22, p = 1). The risk of motor weakness was increased with the transcortical approach compared to the endoscopic approach (OR = 6.10, p = 0.018). There were no significant differences between transcortical and transcallosal approaches regarding newly onset seizures, and no significant mortality differences between all three approaches. This study demonstrates that microsurgical approaches are associated with a greater extent of resection compared to endoscopic approaches; however, best results are likely achieved based on the surgeon's expertise, flexibility, and case review.

Comparative anatomical analysis of the transcallosal-transchoroidal and transcallosal-transforniceal-transchoroidal approaches to the third ventricle

OBJECTIVE

Access to the third ventricle is a veritable challenge to neurosurgeons. In this context, anatomical and morphometric studies are useful for establishing the limitations and advantages of a particular surgical approach. The transchoroidal approach is versatile and provides adequate exposure of the middle and posterior regions of the third ventricle. However, the fornix column limits the exposure of the anterior region of the third ventricle. There is evidence that the unilateral section of the fornix column has little effect on cognitive function. This study compared the anatomical exposure afforded by the transforniceal-transchoroidal approach with that of the transchoroidal approach. In addition, a morphometric evaluation of structures that are relevant to and common in the 2 approaches was performed.

METHODS

The anatomical exposure provided by the transcallosal-transchoroidal and transcallosal-transforniceal-transchoroidal approaches was compared in 8 fresh cadavers, using a neuronavigation system. The working area, microsurgical exposure area, and angular exposure on the longitudinal and transversal planes of 2 anatomical targets (tuber cinereum and cerebral aqueduct) were compared. Additionally, the thickness of the right frontal lobe parenchyma, thickness of the corpus callosum trunk, and longitudinal diameter of the interventricular foramen were measured. The values obtained were submitted to statistical analysis using the Wilcoxon test.

RESULTS

In the quantitative evaluation, compared with the transchoroidal approach, the transforniceal-transchoroidal approach provided a greater mean working area (transforniceal-transchoroidal 150 ± 11 mm2; transchoroidal 121 ± 8 mm2; p < 0.05), larger mean microsurgical exposure area (transforniceal-transchoroidal 101 ± 9 mm2; transchoroidal 80 ± 5 mm2; p < 0.05), larger mean angular exposure area on the longitudinal plane for the tuber cinereum (transforniceal-transchoroidal 71° ± 7°; transchoroidal 64° ± 6°; p < 0.05), and larger mean angular exposure area on the longitudinal plane for the cerebral aqueduct (transforniceal-transchoroidal 62° ± 6°; transchoroidal 55° ± 5°; p < 0.05). No differences were observed in angular exposure along the transverse axis for either anatomical target (tuber cinereum and cerebral aqueduct; p > 0.05). The mean thickness of the right frontal lobe parenchyma was 35 ± 3 mm, the mean thickness of the corpus callosum trunk was 10 ± 1 mm, and the mean longitudinal diameter of the interventricular foramen was 4.6 ± 0.4 mm. In the qualitative assessment, it was noted that the transforniceal-transchoroidal approach led to greater exposure of the third ventricle anterior region structures. There was no difference between approaches in the exposure of the structures of the middle and posterior region.

CONCLUSIONS

The transforniceal-transchoroidal approach provides greater surgical exposure of the third ventricle anterior region than that offered by the transchoroidal approach. In the population studied, morphometric analysis established mean values for anatomical structures common to both approaches.

A Single-Institution Experience with Pineal Region Tumors: 50 Tumors Over 1 Decade

BACKGROUND: Pineal region tumors are rare intracranial tumors that are more common in children than adults. Surgical management of tumors in this region using a tailored approach is a strategy that enhances extent of resection and neurological outcome.

OBJECTIVE: To review our institutional experience with pineal region tumors in children and adults over the past 10 years.

METHODS: Our institutional pathology database and patient records were retrospectively reviewed for details regarding clinical and radiological presentation, surgical management, extent of resection, morbidity, and neurological outcome. Statistical analysis was performed to assess for variables related to functional outcomes.

RESULTS: Fifty patients were identified as having undergone surgical management of a pineal region tumor with at least 1 year of follow-up. Forty-one percent presented with a Karnofsky Performance Scale (KPS) score of 70 or less, all of whom had concomitant hydrocephalus that required urgent treatment. The following variables were statistically significant to KPS score on admission: age, tumor volume, preoperative hydrocephalus, length of hospitalization (total and intensive care unit), and elevations in serum tumor markers. The median postoperative (2 months) KPS score was 90. The following variables were statistically significant with respect to change in KPS score postoperatively: tumor maximum diameter, KPS score on admission, and intensive care unit length of stay. The specific surgical strategy did not correlate to extent of tumor resection, morbidity, immediate neurological outcome, and progression-free survival.

CONCLUSION: Extent of resection, neurological outcome, and progression-free survival in the patients in our series were not related to the specific surgical approach employed and its perioperative complications.

Retractorless surgery for third ventricle tumor resection through the transcallosal approach

OBJECTIVE

Resection of tumors of the third ventricle through the transcallosal-interforniceal approach presents a surgical challenge with potential serious postoperative neurological deficits and complications. Retraction injury of the deep brain tissue and veins is a possible reason. Here, we aimed to investigate the feasibility and value of retractorless surgery in third ventricle tumor resection.

PATIENTS AND METHODS

Since 2014, a total of 31 patients with third ventricle tumors were operated in our institution. All patients were operated using the transcallosal-interforniceal approach with a straight incision. The use of self-retaining retractor or constant retraction was not allowed. At the end of surgery, the opening of corpus callosum was sealed with fibrin glues. The degrees of tumor resection and postoperative neurological function deficits as well as complications were analyzed. The effect of retractorless surgery was evaluated according to the brain edema around the surgical approach on T2 imaging.

RESULTS

Thirty-one tumors were located in the anterior, middle, and posterior of the third ventricle. Total or gross total resection was achieved in 25 patients (80.6%). Postoperative neurological function deficits occurred in 4 patients (12.9%), and patients with mutism had a good recovery 3 weeks post-surgery. Retraction injuries around the surgical pathway were not obvious on T2 imaging. In addition, no subdural hygroma and subcutaneous fluid accumulation occurred.

CONCLUSIONS

The application of retractorless surgery in third ventricle tumors is feasible with enough exposure of tumors. This application could decrease the occurrence of postoperative neurological deficits and complications by avoiding the retraction injury on the deep brain structures.

Comparative anatomical analysis of the transcallosal-transchoroidal and transcallosal-transforniceal-transchoroidal approaches to the third ventricle

OBJECTIVE

Access to the third ventricle is a veritable challenge to neurosurgeons. In this context, anatomical and morphometric studies are useful for establishing the limitations and advantages of a particular surgical approach. The transchoroidal approach is versatile and provides adequate exposure of the middle and posterior regions of the third ventricle. However, the fornix column limits the exposure of the anterior region of the third ventricle. There is evidence that the unilateral section of the fornix column has little effect on cognitive function. This study compared the anatomical exposure afforded by the transforniceal-transchoroidal approach with that of the transchoroidal approach. In addition, a morphometric evaluation of structures that are relevant to and common in the 2 approaches was performed.

METHODS

The anatomical exposure provided by the transcallosal-transchoroidal and transcallosal-transforniceal-transchoroidal approaches was compared in 8 fresh cadavers, using a neuronavigation system. The working area, microsurgical exposure area, and angular exposure on the longitudinal and transversal planes of 2 anatomical targets (tuber cinereum and cerebral aqueduct) were compared. Additionally, the thickness of the right frontal lobe parenchyma, thickness of the corpus callosum trunk, and longitudinal diameter of the interventricular foramen were measured. The values obtained were submitted to statistical analysis using the Wilcoxon test.

RESULTS

In the quantitative evaluation, compared with the transchoroidal approach, the transforniceal-transchoroidal approach provided a greater mean working area (transforniceal-transchoroidal 150 ± 11 mm2; transchoroidal 121 ± 8 mm2; p < 0.05), larger mean microsurgical exposure area (transforniceal-transchoroidal 101 ± 9 mm2; transchoroidal 80 ± 5 mm2; p < 0.05), larger mean angular exposure area on the longitudinal plane for the tuber cinereum (transforniceal-transchoroidal 71° ± 7°; transchoroidal 64° ± 6°; p < 0.05), and larger mean angular exposure area on the longitudinal plane for the cerebral aqueduct (transforniceal-transchoroidal 62° ± 6°; transchoroidal 55° ± 5°; p < 0.05). No differences were observed in angular exposure along the transverse axis for either anatomical target (tuber cinereum and cerebral aqueduct; p > 0.05). The mean thickness of the right frontal lobe parenchyma was 35 ± 3 mm, the mean thickness of the corpus callosum trunk was 10 ± 1 mm, and the mean longitudinal diameter of the interventricular foramen was 4.6 ± 0.4 mm. In the qualitative assessment, it was noted that the transforniceal-transchoroidal approach led to greater exposure of the third ventricle anterior region structures. There was no difference between approaches in the exposure of the structures of the middle and posterior region.

CONCLUSIONS

The transforniceal-transchoroidal approach provides greater surgical exposure of the third ventricle anterior region than that offered by the transchoroidal approach. In the population studied, morphometric analysis established mean values for anatomical structures common to both approaches.

Microsurgical resection of tumors of the lateral and third ventricles: operative corridors for difficult-to-reach lesions

Tumors of the lateral and third ventricles are cradled on all sides by vital vascular and eloquent neural structures. Microsurgical resection, which always requires attentive planning, plays a critical role in the contemporary management of these lesions. This article provides an overview of the open microsurgical approaches to the region highlighting key clinical perspectives.

Complication avoidance in transcallosal transforaminal approach to colloid cysts of the anterior third ventriclen: An analysis of 80 cases

Object:

The objective of the present study is to analyze the complications and their avoidance in a series of 80 patients operated by transcallosal transforaminal approach to colloid cysts of the anterior third ventricle.

Materials and Methods:

The surgical outcome and complications of 80 patients operated by transcallosal transforaminal approach for colloid cysts in the anterior third ventricle was analyzed. A detailed pre- and post-operative neurological assessment was done in all patients. Neurocognitive assessment of corpus callosal function was done in the last 22 cases. CT scan of the brain was done in all patients, before and after surgery.

Results:

All patients underwent transcallosal transforaminal approach. Total excision of the lesion was achieved in 79 patients and subtotal in one. The complications encountered were postoperative seizures in six, acute hydrocephalus in four, venous cortical infarct in four, transient hemiparesis in four, transient memory impairment, especially for immediate recall in nine, mutism in one, subdural hematoma in one, meningitis in three, and tension pneumocephalus in one patient. There were two mortalities. There was no incidence of postoperative disconnection syndrome.

Conclusion:

Colloid cyst is surgically curable. With good knowledge of the regional anatomy and meticulous microsurgical techniques, there is a low mortality and minimum morbidity, when compared to the natural history of the disease. With increasing experience, most of the complications are avoidable. The limited anterior callosotomy does not result in disconnection syndromes.

The endoscopic endonasal approach for the management of craniopharyngiomas involving the third ventricle

The third ventricle has historically represented one of the most challenging areas to access surgically, so that lesions directly harboring into the ventricular chamber or secondarily extending into it from adjacent areas have been approached by means of different transcranial routes. The aim of this work is to report our experience with the endoscopic endonasal approach in the management of a series of patients affected by craniopharyngiomas, extending into or arising from the third ventricle, evaluating pros and cons of this technique, also in regards of the anatomy and the pathology dealt with. During the period between January 2001 and February 2011, 12 patients, 9 male and 3 female (mean age 50.4 years; range 12-68) underwent an endoscopic endonasal approach for the treatment of a craniopharyngioma involving or arising from the third ventricle. According to the grade of involvement of the third ventricle, we identified three main ventricular growth patterns: (1) stalk-infundibulum; (2) infundibulum-ventricular chamber; (3) stalk-infundibulum-ventricular chamber. Though gross total removal was achieved in eight patients (66.7%), in three patients (25%) was possible a near total removal (>95%) and only in one case (8.3%) tumor removal has been partial (<50%). The overall analysis revealed a rate of 77.8% improvement of post-operative visual defects. Concerning the complications, we reported an overall CSF rate of 16.7%; two patients developed a subdural hematoma that has been treated with a surgical drainage. One patient died after the occurrence of a brainstem hemorrhage. The endoscopic endonasal route provides a good exposure, especially of the sub- and retro-chiasmatic areas, as well as of the stalk-infundibulum axis, which represents, when directly involved by a lesion, a gate to access the third ventricle chamber. Despite this study reporting only a preliminary experience, it seems that in properly selected cases--namely tumors growing mostly along the pituitary stem-infundibulum-third ventricle axis--this approach could be advocated as a valid route among the wide kaleidoscope of surgical approaches to the third ventricle.

The choroidal fissure: anatomy and surgical implications

The choroidal fissure (CF) is an important landmark that allows approaches to the deepest aspects of the brain. It is the C-shaped site of attachment of the choroid plexus in the lateral ventricles, which runs between fornix and thalamus. The thinness and the absence of neural tissue between the ependyma and pia matter of this part of the medial wall of the lateral ventricles provides a surgical pathway to the third ventricle and perimesencephalic cisterns. A precise knowledge of the microsurgical anatomy of the region, particularly vascular relationships, is essential to consider surgery through the CF. We decided to present the anatomy of the CF in three distinct chapters, corresponding to three compartments of the C-shaped structure of the CF. In each compartment - rostral, dorsal and caudal - we developed the neurovascular anatomy and then discussed the clinical and surgical applications.

Complete Microsurgical Resection of Colloid Cysts with a Dual-port Endoscopic Technique

Objective:

A dual-port endoscopic approach, used for the surgical management of colloid cysts, was developed with the following goals: 1) a direct, unobstructed, high-illumination endoscopic view of the attachment point of the colloid cyst to the tela choroidea, and 2) a gross total resection of the colloid cyst capsule using microsurgical techniques.

Methods:

Eleven symptomatic, hydrocephalic, colloid cyst patients who underwent operation with a unilateral, precoronal-frontopolar dual-port endoscopic technique were retrospectively assessed. Preoperative magnetic resonance imaging scans were analyzed, comparing the lateral precoronal to the frontopolar approach, to determine the degree of angulation that would be required to directly view the roof of the third ventricle. Clinical outcome and radiographical follow-up were assessed.

Results:

The frontopolar approach achieved an approach angle to the roof of the third ventricle of only 15 ± 4 degrees compared with 56 ± 6 degrees (P&lt; 0.0001) for the precoronal approach. The view obtained from the frontopolar endoscope allowed excellent visualization of the cyst attachment point. Microsurgical dissection techniques, using many standard microsurgical instruments introduced through the second port, were satisfactorily accomplished. Complete resections were obtained in 10 out of 11 dual-port patients. Worsening of memory deficits occurred in one patient. There was no cyst recurrence with a mean follow-up period of 26 ± 27 months.

Conclusion:

The dual-port endoscopic technique described is an alternative to classic microsurgical craniotomy approaches. The technique allows excellent visualization of the colloid cyst attachment and permits microdissection techniques.

Fetal azygos pericallosal artery

An unpaired trunk forming part of the anterior cerebral arteries, the so-called azygos pericallosal artery, was found in a male fetus among a collection of 200 fetuses. The morphological characteristics of the trunk and the anterior cerebral arteries at the "preazygos" and the "postazygos" segments were examined using an operating microscope. The azygos pericallosal artery distributes into three postazygos segments of which only the median postazygos segment or median callosal artery had a bihemispheric distribution of its branches to the medial telencephalic surfaces.

Complications of interhemispheric transcallosal approach in children: review of 15 years experience

OBJECTIVE

The interhemispheric transcallosal approach to deep-seated lesions in and around the ventricular system avoids cortical manipulation and injury. Few case series discuss the morbidity associated with this approach. This study describes the 15-year experience of the senior author in Southern California.

METHODS

All pediatric patients who have undergone interhemispheric, transcallosal resections of mass lesions over a 15-year period were identified. The surgical approach was uniform with respect to positioning of the patient. Intra-operative and post-operative data were collected retrospectively from the medical records. The need for bridging vein ligation as well as the incidence of hemiparesis, seizures, memory disturbances, and the need for subsequent cerebrospinal fluid (CSF) diversion were identified.

RESULTS

Sixty-five patients were identified. The incidence of transient post-operative hemiparesis appeared to be higher in those patients who required ligation of one or two parasagittal veins (44.6% versus 18.5%) with no difference in long-term outcome. Nineteen percent (18.5%) of patients had post-operative seizures; however, no long-term seizure disorder was identified. Nine percent (9.2%) had reports of transient short-term memory deficits. Thirty-four percent (33.8%) of patients required secondary operative intervention for CSF diversion. The total complication rate, including need for CSF diversion, transient hemiparesis, infection, post-operative seizures, and memory disturbance was 36.9%. By 1 year, the total number of patients with persistent hemiparesis, memory disturbance, or seizures refractory to medication was 4 (6.2%).

CONCLUSION

This series demonstrates that the interhemispheric transcallosal corridor is a versatile and safe approach in childhood, resulting in low post-operative permanent morbidity.

Lateral Ventricle Tumors: Surgical Strategies According to Tumor Origin and Development— A Series of 72 Cases

OBJECTIVE:

Optimal surgical management in lateral ventricle tumors remains controversial. We conducted a retrospective study of patients with these lesions treated with a surgical strategy on the basis of tumor origin: primary or secondary ventricular and associated transependymal development.

METHODS:

A total of 72 patients underwent surgery for lateral ventricle tumors. The mean patient age was 39 years (range, 6 mo to 78 yr). Raised intracranial pressure occurred in 53% of patients, followed by mental disturbances or psychiatric symptoms (32%) and motor deficits (21%). The transcortical approach was used in 44 patients, and an interhemispheric approach was used in 28 patients; a transcallosal approach was used in 16 patients, and a parasplenial approach was used in 12 patients. Neuropsychological tests were performed in selected patients.

RESULTS:

Total resection was performed in 82% of patients. Sixty-five percent of tumors were benign and low-grade tumors. There was no surgical mortality, and the morbidity rate was 11%. Postoperative epilepsy (5.9%) was significantly increased in the transcortical group. The mean follow-up period was 55 months; 59% of patients achieved good recovery and moderate disability. In postoperative neuropsychological testing sessions, deficits in verbal memory were observed in six patients (8%). Final morbidity correlated well with preoperative clinical condition and pathological diagnosis.

CONCLUSION:

Lateral ventricle tumors can be treated best by careful selection of the approach according to tumor origin and development. Overall, the transcallosal approach is preferred, but in patients with transependymal growth or large primary or secondary ventricular tumors, the transcortical is a better option.

The interhemispheric transcallosal-transversal approach to the lesions of the anterior and middle third ventricle: Surgical validity and neuropsychological evaluation of the outcome

Based on the observation of the course of callosal fibres and of their artero-venous support as appearing in a microanatomic study, the Authors propose a variant of standard callosotomy procedure by the introduction of the transverse section of callosal fibres. This technique would allow the surgeon to spare a larger number of callosal fibres by the combined effect of a lower direct mechanical traction on fibres and a lower impact on artero-venous microcircle. The neuropsychological outcome of the patients who underwent this kind of procedure was evaluated. Fourteen patients affected by occupying-space lesions involving the anterior and middle third ventricle were included in the study. Ten patients underwent transverse callosotomy, four subjects received standard sagittal callosotomy. A control group was also included in the study. All patients underwent a pre-operative and six months post-operative neuropsychological evaluation focused on performance at cognitive and attentional tasks. No disturbances in executive function were observed in either group. Patients receiving transverse callosotomy performed as well as control group subjects in attentive tasks, which is not the case of patients undergoing sagittal callosotomy who show a marked deficit in selective attention for left side visual field. The observed more favourable neuropsychological outcome supports transverse callosotomy as a valid alternative method to standard longitudinal callosotomy in third ventricle surgery.

Transcortical or transcallosal approach to ventricle-associated lesions: a clinical study on the prognostic role of surgical approach

Most entities in and around the anterior two-thirds of the supratentorial ventricles can be reached via transcortical or transcallosal approach. This study examined the effect of surgical approach on the postoperative neurological outcome. Thirty-eight patients with intra- and periventricular supratentorial lesions were operated on by either frontal transcortical or anterior transcallosal approach. Postoperative diencephalic damage occurred in 22% of patients in the transcortical group and in 36% in the transcallosal group; transient mutism was virtually equivalent in the two groups. Postoperative epilepsy (26%) and subdural fluid collections (30%) occurred only in the transcortical group. The incidence of postoperative hemiparesis was higher in the transcallosal group. There was a high correlation between postoperative Glasgow Outcome Score of 5 and preoperative severity of neurological disease but no correlation between postoperative Glasgow Outcome Score of 5 and location of the lesion or between postoperative clinical course and surgical approach. Surgical outcome of ventricle-associated lesions depends mainly on the severity of preoperative symptoms and not on surgical approach. Additionally, the incidence of postoperative seizures and subdural fluid collections after transcortical surgery is high.

Neuropsychological effects of third ventricle tumor surgery

OBJECTIVE

This study assessed the neuropsychological outcome of patients after surgical treatment for third ventricle brain tumors. Neuropsychological consequences of surgical intervention can have a major impact on patients' quality of life and therefore have important implications for treatment planning.

METHODS

A retrospective analysis of 33 patients' neuropsychological data was performed. All patients received a comprehensive neuropsychological evaluation after treatment for a primary brain tumor in the third ventricular region. Twenty-six patients underwent surgery, 14 via the transcallosal approach and 12 via a subfrontal, left transcortical, right pterional, or infratentorial supracerebellar approach. Seven patients were not treated by surgical intervention.

RESULTS

There was a significantly elevated frequency of cognitive impairment relative to normative values in memory, executive functioning, and fine manual speed and dexterity. There were no differences in mean neuropsychological scores between patients who underwent surgery and those who did not. There were no differences in mean performance on the basis of surgical approach, tumor infiltration, or history of cranial irradiation. Repeated measures data available for two patients revealed memory impairment before and after surgery, and one patient experienced major improvement after surgery on a measure of mental flexibility and problem solving.

CONCLUSION

Patients with third ventricle tumors are at risk for developing impairments in memory, executive function, and fine manual speed and dexterity, which are domains associated with frontal subcortical functions. In the current study, different types of treatment were not associated with differential cognitive sequelae, and surgical intervention did not account for cognitive deficits.

Transcallosal interforniceal-transforaminal approach for removing lesions occupying the third ventricular space: clinical and neuropsychological results

OBJECTIVE

The present study was undertaken to describe the clinical and prospective neuropsychological results for our group of 30 patients who were treated using a transcallosal interforniceal-transforaminal microsurgical approach.

METHODS

The transcallosal interforniceal and transcallosal-transforaminal approaches were used to treat 30 patients with space-occupying lesions located in the anterior part of the third ventricle. We used a modified anterior transcallosal microsurgical approach, as described recently. The patients underwent extensive, pre- and postoperative, prospective neuropsychological testing, using a specially designed test battery.

RESULTS

Twenty-three of 30 patients (77%) experienced excellent clinical outcomes (Glasgow Outcome Scale Grade V). The surgical procedures described in this report did not themselves impair attentional function. In both the early and late postoperative neuropsychological testing sessions, deficits in verbal memory were only rarely observed and were not noted to be correlated with the surgical procedures. The most relevant neuropsychological results for individual patients are reported in detail.

CONCLUSION

The approach described here can be successfully used for the resection of various space-occupying lesions in the anterior part of the third ventricle. The anatomic landmarks we recently defined and described (for example, the midline vessel on the trunk of the corpus callosum, to direct the callosotomy) guide the surgical path. Furthermore, we recommend the use of neuropsychological test batteries for both scientific and rehabilitative purposes.

The transcallosal-transforaminal approach to the third ventricle with regard to the venous variations in this region

Surgical approaches to lesions located in the anterior and middle portions of the third ventricle are challenging, even for experienced neurosurgeons. Various exposures involving the foramen of Monro, the choroidal fissure, the fornices, and the lamina terminalis have been advocated in numerous publications. The authors conducted a microsurgical anatomical study in 20 cadaveric brain specimens (40 hemispheres) to identify an exposure of the third ventricle that would avoid compromising vital structures. An investigation of the variations in the subependymal veins of the lateral ventricle in the region of the foramen of Monro was performed, as these structures are intimately associated with the surgical exposure of the third ventricle. In 16 (80%) of the brain specimens studied, 19 (47.5%) of the hemispheres displayed a posterior location of the anterior septal vein-internal cerebral vein (ASV-ICV) junction, 3 to 13 mm (average 6 mm) beyond the foramen of Monro within the velum interpositum, not adjacent to the posterior margin of the foramen of Monro (the classic description). Based on this finding, the authors advocate opening the choroidal fissure as far as the ASV-ICV junction to enlarge the foramen of Monro posteriorly. This technique achieves adequate access to the anterior and middle portions of the third ventricle without causing injury to vital neural or vascular structures. The high incidence of posteriorly located ASV-ICV junctions is a significant factor influencing the successful course of surgery. Precise planning of the surgical approach is possible, because the location of the junction is revealed on preoperative neuroradiological studies, in particular on magnetic resonance venography. It can therefore be determined in advance which foramen of Monro qualifies for posterior enlargement to gain the widest possible access to the third ventricle. This technique was applied in three patients with a third ventricular tumor, and knowledge of the venous variations in this region was an important resource in guiding the operative exposure.

Corpus callosal changes associated with hydrocephalus: a report of two cases

OBJECTIVE AND IMPORTANCE

Focal or diffuse corpus callosal changes can occur in patients with active hydrocephalus who undergo shunting procedures. The neural compression caused by active hydrocephalus and the conditions that follow ventricular shunting may contribute to the development of these changes.

CLINICAL PRESENTATION

Two patients who underwent successful shunting for hydrocephalus subsequently developed thickening and diffuse signal changes in the corpus callosum, which were revealed by magnetic resonance imaging. The abnormal signal intensity extended laterally and linearly along the callosal fiber tracts and was not associated with mass effect. These changes persisted despite clinical improvement after the shunts were implanted.

INTERVENTION

Detailed neuropsychological testing showed no evidence of residual cognitive impairment or any interruption of the interhemispheric transfer of information. It has been proposed that the impingement of the corpus callosum by the rigid falx may contribute to symptomatic hydrocephalus. Impingement may cause partial hemispheric disconnection, resulting from callosal axonal dysfunction. Our patients showed radiographic evidence of dramatic changes within the corpus callosum after ventricular shunting, consistent with a transcallosal demyelinating process. Patients demonstrated neither clinical nor neuropsychological evidence of callosal disconnection, even though the callosal changes persisted. In these two patients, it is reasonable to assume that the relative sparing of the splenium accounts for the lack of neuropsychological deficits.

CONCLUSION

Based on our findings, conservative management, rather than a stereotactic biopsy or other forms of intervention, seems reasonable when these characteristic changes of the callosum are noted by magnetic resonance imaging after a shunt for hydrocephalus has been implanted in the patient.

Stereotactic microsurgical craniotomy for the treatment of third ventricular colloid cysts

The treatment of colloid cysts remains controversial. This article reports on 18 patients with colloid cysts of the third ventricle who presented to the University of Michigan between January 1990 and June 1995. Two patients had conventional transcortical-transventricular approaches; the remaining 16 patients underwent a stereotactic modification of the transcortical approach, using a specially designed cylindrical retractor, for the resection of their colloid cysts. Minor morbidity and no mortality have been associated with this technique. There have been no instances of recurrence during the period of this report. The mean operative time for the two conventional craniotomies was 233 minutes, compared with 129 minutes for the stereotactic craniotomies. Our technique allows for a limited craniotomy and limited cortical disruption. It is not dependent on ventricular size. Localization of the colloid cyst is trivial because of modern stereotactic technology, and all standard microsurgical techniques can be used. The retractor is readily adaptable to any Leksell system. This technique shortens operative time, compared with conventional craniotomy, and allows for definitive treatment of the lesion.