Occipital Transtentorial Research Articles

Surgery for Pineal Region Tumors: Concept and Technical Aspects of Occipital Transtentorial Approach

This article describes the concept and technical aspects of the occipital transtentorial approach(OTA)for tumor extraction in the pineal region, based on the author's experience and literature review. Awareness of the successful completion of each surgical step is essential. Preoperative preparation and imaging evaluations, with particular attention to the veins and venous sinuses, are especially important. It is also helpful to perform a complete dura incision and inversion up to the edge of confluence, superior sagittal sinus, and transverse sinus. Subsequently, it is necessary to understand the usefulness of adequate dissection in the vicinity of the corpus callosum and internal occipital vein(IOV)so that the occipital lobe can be moved without difficulty. Furthermore, development of the IOV with adequate tentoriotomy facilitates contralateral work. Finally, complete understanding of each step during the bilateral, ambient cistern and cerebellomesencephalic fissure dissection process, where the cerebellar vermis can be moved without difficulty, is necessary for a safe OTA to pineal region tumor extraction.

Pediatric Pineal Region Tumors: Special Reference to Posterior Interhemispheric Trans-Tentorial Approach.

Pediatric pineal region tumors consist of tumors of pineal gland origin and parapineal origin. The former are comprised of germ cell tumor (GCT) and pineal parenchymal tumor. The latter originate from the surrounding neural structures, such as the midbrain and thalamus; thus, they are often benign gliomas during childhood. Pineal region tumors often cause obstructive hydrocephalus, which is the main cause of presenting symptoms. Advanced imaging discloses precise location and extension of the tumor and associated anomalies such as hydrocephalous, dissemination, hemorrhage, etc. Hydrocephalus has been managed with CSF diversion, mostly using an endoscopic third ventriculostomy. Because of different treatment paradigms for each tumor type, histological confirmation is needed either through biopsy, tumor markers for GCTs, and/or surgical resection sampling. Radical resection of these tumors remains a challenge due to their deep-seated location and involvement of delicate neural and vascular structures. Comparison of common craniotomy approaches, occipital transtentorial (OT) and infratentorial supracerebellar (ITSC), is reviewed for their advantages and disadvantages. Surgical area exposure and blind spots are important factors for successful tumor removal. The surgical techniques and nuances that the author employs for tumor resection via a posterior interhemispheric transtentorial approach are presented.

Surgical outcome of pineal region lesions in paediatric population

Introduction. Pineal region pathologies are heterogenous, spectrum ranging from benign, infective to malignant in nature such as parenchymal, germ cell, glial, melanomas, metastatic, tubercular, etc. These lesions are commoner in the pediatric age group and have a variable outcome. The goal of this study is to present our experience regarding the surgical outcomes of pineal region lesions in the paediatric population. Objective. The objective of this study is to access the surgical outcome of pineal region lesions in the paediatric population Methods and Material. Eighty cases of pineal region lesions in the paediatric population (upto 15 years of age) operated in the neurosurgery department, G.B Pant Hospital New Delhi via either Occipital transtentorial or Supracerebellar Infratentorial approaches were retrospectively analyzed. Results. There were four main groups of lesions with pineal parenchymal tumours (35 cases) being the commonest. Glial tumours were the next most common contributing 29 cases. Germ cell tumours comprise 7 and miscellaneous 9 cases. The outcome showed graded improvement with the extent of tumour removal and 57 patients(71.25%) improved following surgery. The clinical status of 20 patients(25%) remained unchanged and 3(3.75%) deteriorated from their pre-operative status. 3 patients(3.75%) died in the immediate post-operative period and 11(13.75%) died due to recurrent disease. Conclusion. A graded increase in survival was noted with increasing the degree of resection and postoperative adjuvant therapy in malignant pineal tumours whereas benign pineal lesions can be managed with surgery. Pure germinomas are the only tumour for which the survival rate was unrelated to extent of tumour resection.

Pediatric pineal region tumors: institutional experience of surgical managements with posterior interhemispheric transtentorial approach.

Resecting pineal region tumors in children is often challenging. Several approaches have been proposed and practiced. A personal series of pediatric pineal region tumors resected through craniotomy with posterior interhemispheric occipital transtentorial (OT) approach are reviewed. We present the surgical techniques, pitfalls, and their results. Eighty patients ranging in age from 3months to 21years old, and treated over 3 decades were reviewed. Hydrocephalus caused the main presenting symptoms and was noted in 74 patients. It was treated prior to the craniotomy for tumor resection with endoscopic third ventriculostomy (ETV) in 33, external ventricular drainage in 26, and precraniotomy shunt in 15. Nine patients had ETV together with endoscopic biopsy. All patients had a parieto-occipital craniotomy in a prone position. Through a tentorial section, a gross total resection of the tumor was attempted except for germinomas. The tumor pathology showed 32 germ cell tumors (GCT), 22 benign astrocytomas, 13 pineal parenchymal tumors, 5 ATRTs, 3 papillary tumors, and 5 others. Of GCTs, 18 were teratomas. The extent of resection consisted of 55 gross total resections, 13 subtotal resections, 10 partial, and 2 biopsies with one postoperative death. Hemiparesis in 2, cerebellar ataxia in another 2, and hemiballismus in 1 were transient and improved over time. One had permanent hemisensory loss and another patient had bilateral oculomotor palsy. Postoperative homonymous hemianopia occurred in 2 patients but subsided over a short period of time. Parinaud's sign was noted in 24 patients, of which 16 were transient. The posterior interhemispheric OT approach provides a safe route and comfortable access to the pineal region inchildren. A great majority of postoperative neurological complications are the results of direct manipulations of the midbrain at tumor resection. Identification and preservation of the tumor-brain interface are of paramount importance. GCTs other than teratomas are treated with neoadjuvant chemotherapy and may eliminate the need for craniotomy. Exophytic midbrain JPAs are amenable to resection.

Infratentorial supracerebellar approach versus occipital transtentorial approach for pineal region tumors. Our technical considerations

Introduction: Despite the deep-seated location of pineal region tumors, surgical resection has become safer and more effective, and now plays an essential role in their management. Tissue diagnosis allows the initiation of chemotherapy or radiotherapy, and resection can be curative or improve the efficacy of adjuvant therapies. Objective: Infratentorial supracerebellar (ITSC) and occipital transtentorial (OTT) approaches are the most used for pineal tumors resection. This study aims to describe feasible criteria for better approach indication based on our surgical experience. Methods: Forty-two patients were divided for tumor resection, using tentorial surface angle in sagittal MRI view in the approach selection: Group 1 (25 ITSC); Group 2 (15 OTT); Group 3 (two combined approaches). Results: Group 1 achieved successful total removal. It was observed one visual impairment, one hydrocephalus patient with postoperative meningitis, and other one with postoperative hematoma. Group 2 presented 13 total resections, one visual impairment and transient contralateral hemianesthesia. Group 3 resulted in one air embolism and one ventriculitis after ventriculoperitoneal shunt. No surgical mortality registered. Conclusion: A descriptive analysis of 42 pineal tumor cases showed minimal complications. The ideal approach is well decided based on the angle between tentorial surface and vertical midline on sagittal plane.

Occipital transtentorial approach for pineal region lesions: Addressing the controversies in conventional teaching.

Background: The occipital transtentorial (OT) approach is well-established approach for pineal region tumors and can be of choice for the lesions located around the suboccipital part of tentorium such as the quadrigeminal plate, posterior part of thalamus, tentorial surface of cerebellum, splenial region, posterior falx, and lesions around the tentorial incisura. However, it is not very much extensively used in the above-mentioned locations other than the pineal region.Methods: Thirty-one patients of pineal region lesions were operated by OT approach, the role of conventional preoperative evaluation of the anatomy of the venous sinuses, deep venous system, and tentorial angle was investigated.Results: A variety of lesions were operated using this approach achieving gross and near total resection in majority of the cases (76.6%), with acceptable postoperative mean modified Rankin scales (1.8).Conclusion: The OT is a preferable approach for pineal region lesions for patients of all ages and can be tailored for achieving high resectability rates irrespective of the status of the deep venous system and tentorial angle, with reasonable postoperative surgical outcome.

Quantitative analysis of ipsilateral and contralateral supracerebellar infratentorial and occipital transtentorial approaches to the cisternal pulvinar: laboratory anatomical investigation.

The cisternal pulvinar is a challenging location for neurosurgery. Four approaches for reaching the pulvinar without cortical transgression are the ipsilateral supracerebellar infratentorial (iSCIT), contralateral supracerebellar infratentorial (cSCIT), ipsilateral occipital transtentorial (iOCTT), and contralateral occipital transtentorial/falcine (cOCTF) approaches. This study quantitatively compared these approaches in terms of surgical exposure and maneuverability. Each of the 4 approaches was performed in 4 cadaveric heads (8 specimens in total). A 6-sided anatomical polygonal region was configured over the cisternal pulvinar, defined by 6 reachable anatomical points in different vectors. Multiple polygons were subsequently formed to calculate the areas of exposure. The surgical freedom of each approach was calculated as the maximum allowable working area at the proximal end of a probe, with the distal end fixed at the posterior pole of the pulvinar. Areas of exposure, surgical freedom, and the working distance (surgical depth) of all approaches were compared. No significant difference was found among the 4 different approaches with regard to the surgical depth, surgical freedom, or medial exposure area of the pulvinar. In the pairwise comparison, the cSCIT approach provided a significantly larger lateral exposure (39 ± 9.8 mm2) than iSCIT (19 ± 10.3 mm2, p < 0.01), iOCTT (19 ± 8.2 mm2, p < 0.01), and cOCTF (28 ± 7.3 mm2, p = 0.02) approaches. The total exposure area with a cSCIT approach (75 ± 23.1 mm2) was significantly larger than with iOCTT (43 ± 16.4 mm2, p < 0.01) and iSCIT (40 ± 20.2 mm2, p = 0.01) approaches (pairwise, p ≤ 0.01). The cSCIT approach is preferable among the 4 compared approaches, demonstrating better exposure to the cisternal pulvinar than ipsilateral approaches and a larger lateral exposure than the cOCTF approach. Both contralateral approaches described (cSCIT and cOCTF) provided enhanced lateral exposure to the pulvinar, while the cOCTF provided a larger exposure to the lateral portion of the pulvinar than the iOCTT. Medial exposure and maneuverability did not differ among the approaches. A short tentorium may negatively impact an ipsilateral approach because the cingulate isthmus and parahippocampal gyrus tend to protrude, in which case they can obstruct access to the cisternal pulvinar ipsilaterally.

Contralateral Interhemispheric Transcallosal Transchoroidal Approach for Resection of a Tumor in the Lateral Wall of the Third Ventricle: 2-Dimensional Operative Video.

Third ventricular tumors pose a surgical challenge, given the intricate surrounding anatomy and depth of the surgical field. A surgical approach to these lesions can involve several different trajectories, the selection of which is dependent on the location of the tumor. Approaches include transforaminal, translamina terminalis, interforniceal, occipital transtentorial, endoscopic transventricular, transchoroidal, and supracerebellar infratentorial. This patient had a metastatic lesion within the lateral wall of the third ventricle. The selection of the surgical approach was dependent on the laterality of the tumor. The foramen of Monro was identified, and landmarks were confirmed. The choroid plexus could then be retracted medially, and the choroidal sulcus was identified. The sulcus was entered laterally to minimize the risk of transgressing the fornix. The tumor was identified along the lateral third ventricular wall, and the plane between the tumor and normal plane was readily created. The tumor was then removed entirely, and postoperative imaging demonstrated a complete resection. The patient gave informed consent for surgery and video recording. Institutional review board approval was deemed unnecessary. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Supracerebellar Infratentorial and Occipital Transtentorial Approaches to the Pulvinar: Ipsilateral Versus Contralateral Corridors.

Due to the critical neurovascular structures that surround the pulvinar, deciding the best surgical approach can be challenging, with multiple options available. To analyze and compare the ipsilateral vs the contralateral version of the 2 main approaches to the cisternal pulvinar surface: paramedian supracerebellar infratentorial (PSCI) and interhemispheric occipital transtentorial (IOT). The PSCI and IOT approaches were performed on 7 formalin-fixed adult cadaveric heads to evaluate qualitatively and quantitatively the microsurgical exposure of relevant anatomic structures. We quantitatively measured the corridor distance to our target with each approach. The ipsilateral PSCI approach provided an easier access and a better exposure of the anteromedial portion of the cisternal pulvinar surface. The contralateral approach provided a wider and more accessible exposure of the posterolateral portion of the cisternal pulvinar surface. When protrusion of the posterior parahippocampal gyrus above the free edge of the tentorium was present, the contralateral PSCI approach provided an unobstructed view to both areas. The IOT approach provided a better view of the anteromedial portion of the cisternal pulvinar surface, especially with a contralateral approach. Multiple approaches to the pulvinar have been described, modified, and improved. Based on this anatomic study we believe that although the corridor distance with a contralateral approach is longer, the surgical view and access can be better. We recommend the use of a PSCI contralateral approach especially when a significant protrusion of the posterior parahippocampal gyrus is present.

Tentorial alignment and its relationship to cisternal dimensions of the pineal region: MRI anatomical study with surgical implications using the new clivotentorial method

ObjectivesTentorial alignment and dimensions of posterior fossa cisterns are measurements whose variability can decrease surgical freedom if not taken into account when choosing the approach to the pineal region. The aim is to provide quantitative anatomical information regarding these dimensions, and to discuss their relevance in two most commonly used approaches to this region: the occipital transtentorial and supracerebellar-infratentorial approach. Patients and MethodsA retrospective study of midsagittal T1-weighted MRI images of 410 randomly selected healthy subjects was performed. The clivus-tentorium (C–T) angle was measured to assess tentorial alignment. The following distances were used as craniocaudal cisternal measurements: quadrigeminal cistern = superior colliculi - inferior part of the splenium of corpus callosum (SC-ISCC), and superior cerebellar cistern = vermis - inferior part of the splenium of corpus callosum (VER-ISCC). ResultsMedian C–T angle value was 19 ± 7°, the quadrigeminal cistern height 6.7 ± 1.6 cm, and the superior cerebellar cistern height 10.4 ± 2.6 cm. The C-T angle was negatively correlated with the SC-ISCC distance (r = −0.271; p < 0.001) and the VER-ISCC distance (r = −0.052, p > 0.001). The SC-ISCC distance was positively correlated with the VER-ISCC distance (r = 0.282; p < 0.001). ConclusionOur new method of measuring tentorial alignment provides a simple and effective aid in preoperative planning. For the first time, we present data on craniocaudal dimensions of posterior fossa cisterns, their relationship with tentorial alignment, and discuss their relevance in SCIT and OT approaches.

Anatomy and approaches along the cerebellar-brainstem fissures.

OBJECT Fissure dissection is routinely used in the supratentorial region to access deeply situated pathology while minimizing division of neural tissue. Use of fissure dissection is also practical in the posterior fossa. In this study, the microsurgical anatomy of the 3 cerebellar-brainstem fissures (cerebellomesencephalic, cerebellopontine, and cerebellomedullary) and the various procedures exposing these fissures in brainstem surgery were examined. METHODS Seven cadaveric heads were examined with a microsurgical technique and 3 with fiber dissection to clarify the anatomy of the cerebellar-brainstem and adjacent cerebellar fissures, in which the major vessels and neural structures are located. Several approaches directed along the cerebellar surfaces and fissures, including the supracerebellar infratentorial, occipital transtentorial, retrosigmoid, and midline suboccipital approaches, were examined. The 3 heads examined using fiber dissection defined the anatomy of the cerebellar peduncles coursing in the depths of these fissures. RESULTS Dissections directed along the cerebellar-brainstem and cerebellar fissures provided access to the posterior and posterolateral midbrain and upper pons, lateral pons, floor and lateral wall of the fourth ventricle, and dorsal and lateral medulla. CONCLUSIONS Opening the cerebellar-brainstem and adjacent cerebellar fissures provided access to the brainstem surface hidden by the cerebellum, while minimizing division of neural tissue. Most of the major cerebellar arteries, veins, and vital neural structures are located in or near these fissures and can be accessed through them.

P12.13 * SURGICAL TREATMENT OF BRAINSTEM TUMORS

OBJECTIVE: To determine the extent of resection and neurological outcomes after surgical treatment of brainstem tumors. METHODS: 34 patients with brainstem tumors operated in Regional Centre of Neurosurgery and Neurology from January, 2008 till January, 2014 were retrospectively analyzed. 20 (58.8%) patients were male, and 14 (41.2%) – female. Mean age of the patients was 22.7 years. Among them 16 (47.1%) were of pediatric age, 18 (52.9%) – adults. In 20 cases (58.8%) tumor had exophytic growth pattern into fourth ventricle. In purely intrinsic tumors (14 cases, 41.2%) the localization was: midbrain – 5 patients (14.7%), ponto-mesencephalic junction – 2 cases (5.9%), pons – 2 patients (5.9%), ponto-medullary junction – 2 cases (5.9 %), medulla oblongata – 3 patients (8.8%). Patients were examined neurologically on admission and one month after surgery. The extent of tumor resection was evaluated on early postoperative MRI (first 48 hours). RESULTS: Surgical approach was chosen individually in each case according to tumor location, using a 2-point method. In patients with midbrain tumors 3 different approaches were used: subtemporal (2 cases, 5.9%), occipital transtentorial (2 cases, 5.9%) and supracerebellar (1 patient, 2.9%). In 2 patients (5.9%) retrosigmoid approach was used. The “workhorse” approach in our series was median suboccipital with telo-velar entrance into the cavity of IV ventricle, which was used in 27 cases (79.4%). The tumors were resected through “safe entry” zones in the brainstem. In 28 cases (82.4%) gross total resection was achieved, in 6 patients (17.6%) the resection was subtotal (>90%). 5 patients (14.7%) deteriorated neurologically after surgery on 30 day follow-up, 29 patients (85.3%) improved or remained stable. None of the operated patients died. Histologic results: anaplastic ependymoma – 9 patients (26.5%), ependymoma – 5 patients (14.7%), pilocityc astrocytoma – 6 patients (17.6%), anaplastic astrocytoma – 4 patients (11.8%), medulloblastoma with significant brainstem invasion – 4 patients (11.8%), choroid plexus papilloma – 2 patients (5.9%), metastasis – 2 patients (5.9%), germinoma – 1 patient (2.9%), dermoid – 1 patient (2.9%). CONCLUSION: Surgical treatment of brainstem tumors can be done effectively (gross total removal in 82.4%) and relatively safe (morbidity – 14.7%, mortality – 0%).

How I do it—pineal surgery: supracerebellar infratentorial versus occipital transtentorial

Resection of a pineal tumour requires fastidious pre-operative planning to select the optimal surgical approach and maximise resection while minimising morbidity. To describe and compare the supracerebellar infratentorial and occipital transtentorial approaches. Specific considerations include patient-specific anatomy, extent and relationships of the tumour, and the techniques likely to be employed during resection. The supracerebellar infratentorial approach provides a direct corridor to pineal tumours caudal to the deep veins; for tumours invaginating the tectal plate in a caudal direction the occipital transtentorial provides a better view.

Surgical management of brainstem cavernomas: selection of approaches and microsurgical techniques

This study reviewed surgical experience with brainstem cavernomas in an attempt to define optimal surgical approaches and risks associated with surgical management. Clinical courses were retrospectively reviewed for 36 consecutive patients (12 men, 24 women; mean age, 42 years) who underwent microsurgical resection of brainstem cavernomas between 1996 and 2006. Medical records, surgical records, and neuroimaging examinations were evaluated. All 36 patients presented with > or =1 hemorrhage from the cavernomas and preoperatively displayed some neurological symptoms. Surgical approach was midline suboccipital for 16 pontine and/or medullary cavernomas under the floor of the fourth ventricle, retrosigmoid for 10 lateral mesencephalic, pontine, and/or medullary cavernomas, occipital transtentorial for 2 thalamomesencephalic and 3 mesencephalic cavernomas, combined petrosal for 2 pontine cavernomas, and other for 3 cavernomas. Complete resection according to postoperative magnetic resonance imaging was achieved in 33 of 36 patients. No mortality was encountered in this study. New neurological deficit occurred in the early postoperative period for 18 patients, but was transient in 15 of these. Neurological state as of final follow-up was improved in 16 patients (44%), unchanged in 17 (47%), and worsened in 3 (8%) compared with preoperatively. In conclusion, symptomatic brainstem cavernomas should be considered for surgical treatment. Careful selection of the optimal operative approach and a meticulous microsurgical technique are mandatory.

OCCIPITAL TRANSTENTORIAL APPROACH TO THE PRECENTRAL CEREBELLAR FISSURE AND POSTERIOR INCISURAL SPACE

To describe the surgical techniques and postoperative clinical outcomes with the occipital transtentorial (OT) approach in patients harboring lesions arising from the precentral cerebellar fissure, posterior incisural space, and adjoining structures. Twenty-two patients underwent microsurgical resection of intra-axial lesions arising within the precentral cerebellar fissure and posterior incisural space between 1997 and 2006. Patient demographics, presenting symptoms, pathology, and neurological outcomes were retrospectively reviewed. Pre- and postoperative magnetic resonance imaging scans were evaluated to determine the anatomic extensions of the lesion and the degree of surgical resection. Patients with lesions primarily confined to the pineal and posterior third ventricle approached by a supracerebellar infratentorial trajectory were excluded from this study. Of the 22 patients reported in this series, 17 (77%) had contrast-enhancing lesions, and 5 (23%) had nonenhancing lesions arising from the precentral cerebellar fissure and posterior incisural space. The lesions were oriented dorsomedial to the midbrain and diencephalon in 6 patients (27%), dorsolateral in 14 patients (64%), and lateral in 2 patients (9%). A lateral OT approach directed under the occipitotemporal junction was used in 16 patients (73%), and an interhemispheric OT approach was used in 6 patients (27%). Transient visual field loss occurred in 3 patients (14%); it resolved by the third follow-up month. Gross total resection or near-total resection of the imaging-defined lesion volume was achieved in 19 patients (86%). The OT approaches provide excellent exposure for lesions of the precentral cerebellar fissure, posterior incisural space, and adjacent structures. The lateral OT approach directed under the occipitotemporal junction provides an inline view for lesions situated posterolateral to the brainstem. It also provides an inferiorly directed view under the venous system into the precentral cerebellar fissure and fourth ventricular roof. Visual field deficits are minimized by directing the trajectory under the occipitotemporal junction instead of retracting along the interhemispheric corridor. The interhemispheric OT approach was primarily used for lesions extending superiorly, in the midline or near midline, above the tentorium and venous system into the splenium of corpus callosum, lateral ventricle, and posterior thalamus, where extensive lateral retraction was not required.

Tentorial meningiomas: operative nuances and perioperative management dilemmas

Tentorial meningiomas, comprising approximately 3-6% of all intracranial meningiomas, are complex entities with an intricate relationship to surrounding structures and require multiple surgical approaches. In the present study, the rationale for deciding the approaches for TMs and the perioperative management dilemmas were evaluated. Thirty-seven patients (28 primary [supratentorial (2), infratentorial (20) and both (6)] and nine complex [cerebellopontine (CP) angle (5) and petroclival (4)] underwent surgery using the occipital transtentorial, supracerebellar infratentorial, subtemporal transtentorial, bioccipital suboccipital, midline suboccipital, retrosigmoid, and combined pre and retrosigmoid approaches. The extent of excision was categorized according to Simpson's grade. Simpson's grade of excision was I in six, II in 11, III in nine and IV in 11 patients, respectively. Follow-up assessment (2 months to 9 years) in 27 patients (72.9%) showed that 23 patients returned to their previous activity level with either no or minimal symptoms, three returned to previous activity level with major cranial nerve palsy, and one patient required permanent assistance. One patient had recurrence and four others underwent resurgery for residual tumor. Two patients with petroclival lesions died due to aspiration pneumonitis and meningitis, respectively; one with CP angle TM presented in a poor general condition and expired following emergency ventriculoperitoneal shunt and subsequent definite surgery. Pseudomeningocele, cerebrospinal fluid leak, and cranial nerve palsy were the major morbidities. Classifying TM into medial and lateral, supra and infratentorial groups helps in deciding an appropriate and safe approach. Meticulously preserving venous sinuses is important since the risk of venous infarction cannot be predicted even with radiological good venous collaterization and apparent venous sinus blockade by tumor. Laterally situated tumors carry a better prognosis when compared to the medially situated ones. Leaving a small residual tumor in an effort to preserve important neurovascular structures does not obviate the expectation of a good long-term prognosis with minimal morbidity and low recurrence rates.

COMPARATIVE ANALYSIS OF POSTERIOR APPROACHES TO THE MEDIAL TEMPORAL REGION

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. 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. 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). 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.

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.

Supplementary Comment on “Three-dimensional Computed Tomography Angiography of the Galenic System for the Occipital Transtentorial Approach”

Supplementary Comment on “Three-dimensional Computed Tomography Angiography of the Galenic System for the Occipital Transtentorial Approach”

Lipomas of the pineal region

Background Intracranial lipomas are rare lesions, representing 0.02% of operated intracranial lesions. Lipomas of the pineal region are even rarer and are reported occasionally in the literature. This is possibly because of the fact that they may give rise to clinical symptoms rather infrequently. When they become symptomatic, some form of management must be contemplated. Methods Four cases of lipomas of the pineal region observed in our institute during a 5-year period were investigated, and clinical-diagnostic features were studied. Two of the cases were symptomatic and were submitted to direct surgical treatment. Results Computed tomography (CT) scanning was performed in 3 cases and magnetic resonance imaging (MRI) in all 4. MRI angiography was performed in the last case. The appearance of the lipoma was quite pathognomonic in the neuroimaging diagnostic test. The infiltrative character of the lesion was better defined by MRI. MRI angiography gave evidence of the upward displacement of the deep veins. Direct surgical approach was performed via a right occipital transtentorial approach in one case and supracerebellar route in another. Neither approach appeared to be superior to the other one. Total removal of the lesion seemed to be impossible because of the infiltrative character of the lesion. Postoperative results were satisfactory even with incomplete removal of the lesion. Conclusion Lipomas of the pineal region are rare. Modern neuroimaging permits a straightforward diagnosis of the nature of intracranial lipomas in general and of these lipomas in particular. Some form of management must be contemplated when these lesions become symptomatic. Direct surgical approach, either via an occipital transtentorial or an infratentorial supracerebellar approach, is feasible. Tumor removal must be dealt with cautiously because total removal is impossible without unacceptable postoperative deficits, and generous partial removal warrants long-term symptomatic improvement.