White Fiber Correlates of Amygdalohippocampectomy Through the Middle Temporal Gyrus Approach.

OBJECTIVE: The white fiber and gross anatomy relevant for performing amygdalohippocampectomy through the middle temporal gyrus approach for mesial temporal sclerosis has been depicted by white fiber dissection. METHODS: Three previously frozen and formalin fixed cerebral hemispheres were studied. The Klingler method of fiber dissection was used to study the anatomy. The primary tools used were hand-made wooden spatulas, forceps, and microscissors. The anatomy of the amygdala and hippocampus and the landmarks for performing the disconnection during epilepsy surgery are presented. The white fibers at risk during the middle temporal gyrus approach were studied. RESULTS: The white fiber tracts at risk during the middle temporal gyrus approach for epilepsy surgery are the fibers of the inferior frontooccipital fasciculus, temporal extension of the anterior commissure, Meyer loop of the optic radiation, and uncinate fasciculus. On the basis of our anatomic dissections, we present a novel entry point into the temporal horn, potentially minimizing injury to the fibers of the sagittal stratum. We also propose novel landmarks to perform the amygdala disconnection in mesial temporal sclerosis. CONCLUSIONS: The middle temporal gyrus is a commonly used approach to perform temporal lobectomy and amygdalohippocampectomy for patients with mesial temporal sclerosis. The anatomy relevant to the approach as presented will aid while performing epilepsy surgery.

The lateral cerebral peduncle approach to ventrally placed intra-axial midbrain tumors: A technical note.

We describe the anatomical landmarks and surgical feasibility of a novel 'safe' brainstem entry zone to approach ventrally placed intra-axial midbrain tumors. The anatomy of the brainstem was specifically studied to evaluate safe surgical entry zone in the midbrain on two formalin fixed silicon injected cadaver head specimens. A novel entry point through the lateral one - fifth of the cerebral peduncle was identified to be 'safe' to approach lesions of the ventral midbrain. Three patients, having oculomotor schwannoma, peduncular glioma and a peduncular cavernoma were operated using this safe entry zone. To approach the midbrain, retrosigmoid lateral supracerebellar route was used in two patients and a basal subtemporal avenue was deployed in one patient. On the basis of fine microanatomical dissection on cadavers, a novel entry point through the lateral one-fifth of the cerebral peduncle, 5 mm anterior to the lateral mesencephalic sulcus and approximately 5 mm superior to the fourth nerve was identified. The proposed brainstem entry point traverses the parieto-temporo-occipital pontine fibers and the trajectory is between the corticospinal tracts ventrally and the substantia nigra dorsally. Three patients were operated successfully using the approach. There were no post-operative motor, sensory or extra-pyramidal deficits. The corridor through the lateral one-fifth of the cerebral peduncle presents a safe and relative 'easy' surgical route to approach ventrally placed intra-axial midbrain tumors.

Brainstem Anatomy: A Study on the Basis of the Pattern of Fiber Organization.

OBJECTIVE: A focused dissection of the brainstem was performed to study the various fiber bundles and gray matter nuclei of the brainstem and to decipher the intricate anatomy. METHODS: Ten formalin-fixed cadaveric human brains were procured. The fiber dissection techniques described by Klingler were then adopted to study the anatomy. The primary dissection tools used were thin handmade wooden spatulas and fine jeweler's forceps. The fibers were dissected layer by layer with the use of magnification. RESULTS: The brainstem dissection was performed from the dorsal, ventral, and lateral aspects to provide a 3-dimensional perspective of the internal architecture. We have presented a novel classification of the brainstem white matter in accordance with the internal organization. The fiber tracts of the brainstem can be divided into short projection fibers, long projection fibers, traversing fibers, and association fibers. From our dissection findings, we divided these white fibers of the brainstem into 3 zones from laterally to medially. The first or outermost zone consists of short projection fibers connecting the brainstem to the cerebellum and adjacent thalamic nuclei. The second zone or the middle zone lies medial to the first zone and consists of traversing and long projection fibers. These consist of both ascending and descending fibers. The third zone or the innermost zone consists of the brainstem association fibers. CONCLUSIONS: This division of the fiber bundles into zones will help neurosurgeons in understanding the course and anatomy of the fibers, which can be cumbersome to remember when only studying the sectional anatomy of the brainstem.

Neural Circuitry: Architecture and Function-A Fiber Dissection Study.

OBJECTIVE: White fiber dissection using a gyrus-based approach was performed to study the various associations, commissural, and projection fiber bundles of the brain. METHODS: Ten previously frozen and formalin-fixed cadaveric human brains were included. The fiber dissection techniques described by Klingler were used. The primary dissection tools were thin handmade wooden spatulas and curved metallic spatulas with tips of various sizes. The fibers were studied by the naked eye and with the use of magnification. The various fiber bundles were studied using a gyrus-based approach. The dissection was performed through each named gyrus, and the fiber tracts encountered during dissection were identified, and their relationship to other adjacent fiber bundles was studied. RESULTS: From our dissections, the white fibers of the brain were divided architecturally into 5 groups-4 horizontal groups and 1 vertical group. The 4 horizontal groups were the superficial, middle, deep, and central groups. The association fibers constituted the superficial, middle, and deep groups. The commissural fibers formed the central group, and the projection fibers formed the vertical group. The course of the fiber bundles and their functional co-relationship were determined. CONCLUSIONS: When planning the surgical trajectory, knowledge of the location of white matter tracts is essential to help minimize the occurrence of postoperative deficits. Fiber dissection using the Klingler technique is useful in gaining an understanding of the complex 3-dimensional nature of these white matter tracts and can provide a valuable resource in neurosurgical training.

Exophytic pontine glioblastoma multiforme presenting as cerebellopontine angle mass.

Exophytic pontine glioblastoma multiforme (GBM) is a highly malignant tumor of posterior fossa, which is quite rare and such tumor presenting as cerebellopontine (CP) angle mass is even rarer. Here, we describe a 12-year-old boy who presented with imbalance on walking and facial nerve paresis. Magnetic resonance imaging of the brain revealed an irregular ring enhancing mass lesion of the CP angle, which was initially thought to be a tuberculoma, but was later confirmed to be a GBM. Clinical and radiological differentiation of uncommon lesions of CP angle in children is discussed with brief review of pertaining literature.

Craniovertebral junction 360°: A combined microscopic and endoscopic anatomical study.

OBJECTIVES: Craniovertebral junction (CVJ) can be approached from various corridors depending on the location and extent of disease. A three-dimensional understanding of anatomy of CVJ is paramount for safe surgery in this region. Aim of this cadaveric study is to elucidate combined microscopic and endoscopic anatomy of critical neurovascular structures in this area in relation to bony and muscular landmarks. MATERIALS AND METHODS: Eight fresh-frozen cadaveric heads injected with color silicon were used for this study. A stepwise dissection was done from anterior, posterior, and lateral sides with reference to bony and muscular landmarks. Anterior approach was done endonasal endoscopically. Posterior and lateral approaches were done with a microscope. In two specimens, both anterior and posterior approaches were done to delineate the course of vertebral artery and lower cranial nerves from ventral and dorsal aspects. RESULTS: CVJ can be accessed through three corridors, namely, anterior, posterior, and lateral. Access to clivus, foreman magnum, occipital cervical joint, odontoid, and atlantoaxial joint was studied anteriorly with an endoscope. Superior and inferior clival lines, supracondylar groove, hypoglossal canal, arch of atlas and body of axis, and occipitocervical joint act as useful bony landmarks whereas longus capitis and rectus capitis anterior are related muscles to this approach. In posterior approach, spinous process of axis, arch of atlas, C2 ganglion, and transverse process of atlas and axis are bony landmarks. Rectus capitis posterior major, superior oblique, inferior oblique, and rectus capitis lateralis (RCLa) are muscles related to this approach. Occipital condyles, transverse process of atlas, and jugular tubercle are main bony landmarks in lateral corridor whereas RCLa and posterior belly of digastric muscle are the main muscular landmarks. CONCLUSION: With advances in endoscopic and microscopic techniques, access to lesions and bony anomalies around CVJ is becoming easier and straightforward. A combination of microscopic and endoscopic techniques is more useful to understand this anatomy and may aid in the development of future combined approaches.

Pan ventricular neurocytoma.

Central neurocytomas are intraventricular benign neoplasms located within the lateral ventricle adjacent to foramen of Monro. A rare case of a central neurocytoma extending throughout the entire ventricular system at the time of presentation is reported. The clinical course of this tumor in a 25-year-old male and its management are presented with relevant review of the literature.

Craniovertebral junction melanocytoma: a case report.

Melanocytomas are rare melanocytic tumors of the central nervous system and its presence at the foramen magnum is extremely rare. We report a case of a 55-year-old male presenting with progressive quadriparesis over one year. Imaging showed a well-defined intradural extramedullary lobulated mass at craniovertebral junction towards the left side and extending to left C2-3 neural foramina. Patient was operated through foramen magnum approach with near total excision of tumor. On a ten-month follow up, he was ambulatory with normal motor power on right side of body and left lower limb and with motor power of 4-/5 in left upper limb. Histopathology and immunohistochemistry confirmed the lesion to be a melanocytoma.

Intramedullary spinal neurenteric cyst with fluid-fluid level.

Spinal neurenteric cysts are rare intradural extramedullary lesions of the spine, commonly located in the cervical and thoracic regions. The majority localize ventral to the spinal cord and are associated with other vertebral anomalies. Here, the authors report a rare case of a 3-year-old boy presenting with a 1-week history of meningismus followed by rapid-onset (over a few hours) paraplegia. Magnetic resonance imaging revealed an intramedullary cystic lesion with a fluid-fluid level in the cervicothoracic region of the spinal cord without associated bony or soft tissue abnormalities. To the best of the authors' knowledge, such clinical and radiological presentation of a spinal neurenteric cyst has never been reported. A brief review of the pertinent literature is presented, and the possible pathophysiology of such a presentation is also discussed.

Malignant peripheral nerve sheath tumour of scalp with extradural extension: case report.

Malignant peripheral nerve sheath tumours are uncommon aggressive soft tissue sarcomas that originate from peripheral nerves or cells associated with the nerve sheath. Scalp malignant peripheral nerve sheath tumours are extremely rare and the role of multimodality management is unclear. We report a 43-year-old female with scalp swelling and rapid growth. Imaging demonstrated an aggressive lesion with extradural extension. A wide excision with negative margins was achieved and he defect reconstructed by rotational flap. The patient was given adjuvant radiation. A follow-up scan done one year post radiation did not show any recurrence. Malignant peripheral nerve sheath tumours of the scalp are extremely rare and such an extradural extension has not been described earlier.

Analysis of the anatomy of the Papez circuit and adjoining limbic system by fiber dissection techniques.

Fiber dissection techniques were used to study the limbic system, in particular the Papez circuit. The course, length and anatomical relations of the structures that make up the Papez circuit were delineated. Ten previously frozen and formalin-fixed cadaveric human brains were used, and dissected according to the fiber dissection techniques of Klingler et al. (Schweiz Arch Neurol Psychiatry 1935;36:247-56). The primary dissection tools were thin and curved wooden and metallic spatulas with tips of varying sizes. We found that the Papez circuit (mean length: 350 mm) begins in the hippocampus and continues into the fornix to reach the mamillary body. From there, the mamillothalamic tract continues to the anterior nucleus of the thalamus, which in turn connects to the cingulum by means of anterior thalamic radiations (mean length: 30 mm). The cingulum courses around the corpus callosum to end in the entorhinal cortex, which then projects to the hippocampus, thus completing the circuit. The average length and breadth of the mamillothalamic tract was 18 mm and 1.73 mm respectively. The average length of the cingulum was 19.6 cm and that of the fornix was 71 mm. The entire circuit was anatomically dissected first in situ in the hemisphere and was then reconstructed outside after removing its various components using fine fiber dissection under a surgical microscope. We found that fiber dissection elegantly delineates the anatomical subtleties of the Papez circuit and provides a three-dimensional perspective of the limbic system. Intricate knowledge of the anatomy of this part of the brain aids the neurosurgeon while performing epilepsy surgery and while approaching intrinsic brain parenchymal, ventricular and paraventricular lesions.

Intraparenchymal temporal neurenteric cyst.

A 41-year-old male presented with a rare temporal intraparenchymal neurenteric cyst. A definitive preoperative diagnosis was not possible based upon the neuroradiological features. A complete excision of the cyst was achieved. Histopathology confirmed the diagnosis of a neurenteric cyst, an endodermally derived lesion of the central nervous system.

Fluid-fluid level in pituitary tumors: analysis of management of 106 cases.

OBJECT: The management issues of 106 cases of pituitary tumors with a fluid level within the fluid content of the cystic part of the tumor (a "fluid-fluid" level) were reviewed. METHODS: Between 2000 and March 2009, 1660 pituitary tumors were treated neurosurgically at K.E.M. Hospital. Investigations of 106 of these cases revealed a fluid-fluid level within the tumor. All patients underwent surgery via a transsphenoidal route. The mean follow-up duration was 46 months. RESULTS: The tumors varied in size: 31 were between 1 and 3 cm, and 75 were larger than 3 cm in maximum dimension (mean maximum dimension 3.4 cm). Fifty-two tumors had 1 fluid level, 11 had 2, and 43 had multiple fluid levels (> or = 3). The onset of symptoms was acute in 8 cases and insidious in 98 cases. In 16 cases, there was evidence of acute exacerbation of symptoms during the course of symptom progression. The symptoms were progressive in all cases. Ninety-seven percent of patients had visual deficits at the time of presentation. The solid portion of the tumor was relatively friable and vascular in most cases, and the fluid varied in color and in consistency, from a thin yellow to dark red liquid. Visual outcome was extremely gratifying in the majority of cases; of those presenting with visual dysfunction, 94% reported visual recovery in the immediate postoperative period. During the follow-up period, there was tumor recurrence in 21 cases; in 12 of these cases, the authors documented a fluid-fluid level. The histological features did not indicate malignancy in any case. CONCLUSIONS: A fluid level within a fluid cavity in pituitary tumors is rarely reported but is not uncommon in large/giant tumors. The presence of such a feature suggests that surgery in these cases can be relatively straightforward despite the lesion's large size, and the visual outcome is gratifying. However, recurrence rates are relatively higher in such cases than in other pituitary tumors.