Microsurgical anatomy and surgical exposure of the cerebellar peduncles.

A better understanding of the surgical anatomy of the cerebellar peduncles in different surgical approaches and their relationship with other neural structures are delineated through cadaveric dissections. We aimed to revisit the surgical anatomy of the cerebellar peduncles to describe their courses along the brain stem and the cerebellum and revise their segmental classification in surgical areas exposed through different approaches. Stepwise fiber microdissection was performed along the cerebellar tentorial and suboccipital surfaces. Multiple surgical approaches in each of the cerebellar peduncles were compared in eight silicone-injected cadaveric whole heads to evaluate the peduncular exposure areas. From a neurosurgical point of view, the middle cerebellar peduncle (MCP) was divided into a proximal cisternal and a distal intracerebellar segments; the inferior cerebellar peduncle (ICP) into a ventricular segment followed by a posterior curve and a subsequent intracerebellar segment; the superior cerebellar peduncle (SCP) into an initial congregated, an intermediate intraventricular, and a distal intramesencephalic segment. Retrosigmoid and anterior petrosectomy approaches exposed the junction of the MCP segments; telovelar, supratonsillar, and lateral ICP approaches each reached different segments of ICP; paramedian supracerebellar infratentorial, suboccipital transtentorial, and combined posterior transpetrosal approaches displayed the predecussation SCP within the cerbellomesencephalic fissure, whereas the telovelar approach revealed the intraventricular SCP within the superolateral recess of the fourth ventricle. Better understanding of the microsurgical anatomy of the cerebellar peduncles in various surgical approaches and their exposure limits constitute the most critical aspect for the prevention of surgical morbidity during surgery in and around the pons and the upper medulla. Our findings help in evaluating radiological data and planning an operative procedure for cerebellar peduncles.

Endoscopic Untethering of Tight Filum Terminale: An Operative Technique.

AIM: To demonstrate the various technical advantages of minimally invasive endoscopic untethering of tight filum terminale for the treatment of tethered cord syndrome (TCS). MATERIAL AND METHODS: In five pediatric cases of TCS, we performed untethering by using the endoscopic technique. The age of the patients were 6, 7, 8, 9, and 12 years old. We used a nasal speculum of the transsphenoidal approach during the endoscopic surgical procedure. RESULTS: All the procedures were performed uneventfully, except for one case with a split cord malformation that showed neurologic deterioration caused by excision of the diastematomyelic fibrous septum at the thoracic level (unrelated to the endoscopic procedure at the L5-S1 level). This patient was referred to a rehabilitation clinic 5 days after surgery and showed significant improvement by the third postoperative month. The other four patients were discharged 1 day after the operation. CONCLUSION: Endoscopic release of filum terminale is a safe technique especially if it is performed with neuromonitoring. This technique may shorten the length of hospital stay and reduce perioperative blood loss. However, futher studies with a larger number of patients and long-term follow-up are needed.

Assessing the connectional anatomy of superior and lateral surgical approaches for medial temporal lobe epilepsy.

The most common approaches in the treatment of epilepsy, the trans-sylvian selective amygdalohippocampectomy (SAH) and the anterior temporal lobe resection (ATLR) reach the medial temporal lobe through different surgical routes. Our aim was to delineate the white matter (WM) fiber tracts at risk in relation to trans-sylvian SAH and ATLR by defining each fascicle en route to medial temporal lobe during each approach. ATLR and trans-sylvian SAH were performedand related WM tracts en route to medial temporal region were presented in relation to the relevant approaches and surrounding neurovascular structures. The WM tracts most likely to be disrupted during trans-sylvian SAH along the roof of the temporal horn were the UF - and less commonly IFOF - at the layer of the external capsule, anterior commissure, anterior bend of optic radiations, and sublenticular internal capsule. Amygdaloid projections to the claustrum, putamen and globus pallidus, the tail of caudate and the peduncle of the lentiform nucleus were also in close proximity to the resection cavity. Fiber tracts most likely to be impaired during ATLR included the UF, ILF, IFOF, anterior commissure, optic radiations, and, less likely, the vertical ventral segment of the arcuate fascicle. Both ATLR and trans-sylvian SAH carry the risk of injury to WM pathways, which may result in unpredictable functional loss. A detailed 3-D knowledge of the related connectional anatomy will help subside neurocognitive, neuroophtalmologic, neurolinguistic complications of epilepsy surgery, providing an opportunity to tailor the surgery according to patient's unique connectional and functional anatomy.

Vascularization of the Subthalamic Nucleus: Highlighting the Significance of the Premamillary Artery.

BACKGROUND: The need for a better understanding of the subthalamic nucleus (STN)'s vascular anatomy is still evident because revealing its vascular supply may increase insight in the pathogenesis of related disorders, such as STN ischemia. The mechanisms under motor, behavioral, and cognitive changes following deep brain stimulation treatment may also be explained by its pattern of vascularization. The primary goal of this study was to delineate the vascularization of the STN and highlight the predominant perforating arteries supplying its territory. METHODS: Fiber dissections were performed with the modified Klingler technique under 6-40× magnification by preserving all vascular structures. RESULTS: The thalamic and subthalamic regions were dissected from medial to lateral in silicone-injected cadavers. The STN was revealed as a biconvex-shaped structure surrounded by dense inferolateral bundles of myelinated fibers, the zona incerta, bordering the superolateral portion of the red nucleus. The ventral limit of the STN was the substantia nigra, and the internal capsule traversed from its inferior to anterolateral side. The premamillary artery, a large perforator arising from the posterior communicating artery, constantly supplied the STN and was followed proximally along the anterior third ventricular floor toward its origin. The premamillary artery was found to be one of the posterior perforators of the posterior communicating artery in all hemispheres. CONCLUSIONS: The 3-dimensional microsurgical anatomy of the deep-seated STN region is complex, and the additional knowledge on its vascularization should improve our understanding of its surgical anatomy.

Microneuroanatomy of the Anterior Frontal Laser Trajectory to the Insula.

BACKGROUND: Magnetic resonance imaging-guided laser interstitial thermal therapy (LITT) is an emerging minimally invasive procedure for the treatment of deep intracranial lesions. Insular lesions are challenging to treat because of the risk of damaging important surrounding structures. The precise knowledge of the neural structures that are at risk along the trajectory and during the ablation is essential to reduce associated complications. This study aims to describe the relevant anatomy of the anterior frontal LITT trajectory to the insular region by using sectional anatomy and fiber dissection technique. METHODS: Three silicone-injected cadaveric heads were used to implant laser catheters bilaterally to the insular region by using a frameless stereotactic technique from a frontal approach. Sections were cut in both the oblique axial plane parallel to the trajectory and in the coronal plane. White matter fiber dissections were used to establish the tracts related to the laser trajectory from lateral to medial and medial to lateral. RESULTS: Supraorbital regions were selected as entry points. After crossing the frontal bone, the track intersected the inferior frontal lobe. The catheter was illustrated reaching the insular region medial to the inferior fronto-occipital fasciculus and insular cortex, and superior to the uncinate fasciculus. The uncinate fasciculus, extreme capsule, claustrum, external capsule, and putamen were traversed, preserving the major vascular structures. CONCLUSIONS: Independent of the insular area treated, an understanding of the neuroanatomy related to the anterior frontal laser trajectory is essential to improve the ability to perform LITT of this challenging region.

Surgical Approaches to the Thalamus in Relation to the White Matter Tracts of the Cerebrum.

BACKGROUND: Approaching the thalamus from any angle remains a challenge because of its deep-seated location and intimate relations with adjacent important neurovascular structures and functions such as relaying sensory and motor signals and cognition. Our aim was to explore the relationship of the white matter tracts of the cerebrum to the thalamus using a fiber dissection technique, to delineate anatomic principles of approaches to the thalamus, and to discuss the tracts at risk in relation to each approach. METHODS: The thalamus was subdivided into 6 different regions and 13 approaches were examined in an attempt to describe a surgical road map. RESULTS: To reach the anteroinferior, medial, and lateral parts of the thalamus, the anterior and middle group approaches were used, and to reach the posterosuperior and posteroinferior thalamus, posterior and middle group approaches were used. The anteroinferior zone was the most difficult site to be accessed and the posterosuperior thalamus had the maximum number of alternative approaches. The distal transsylvian approach to the posterosuperior thalamus and the supracarotid infrafrontal approach to the anteroinferior thalamus had the highest number of neural structures severed within the surgical corridor. The infratentorial approaches and the suboccipital transtentorial approach preserve most of the white matter tracts en route to the posterosuperior and medial posteroinferior parts of the thalamus. CONCLUSIONS: When the surgical approaches for thalamic lesions are defined, white matter tracts along the surgical route should be taken into consideration.

Fast gray matter acquisition T1 inversion recovery MRI to delineate the mammillothalamic tract for preoperative direct targeting of the anterior nucleus of the thalamus for deep brain stimulation in epilepsy.

When medically intractable epilepsy is multifocal or focal but poorly localized, neuromodulation can be useful therapy. One such technique is deep brain stimulation (DBS) targeting the anterior nucleus of the thalamus (ANT). Unfortunately, the ANT is difficult to visualize in standard MRI sequences and its indirect targeting is difficult because of thalamic variability and atrophy in patients with epilepsy. The following study describes the novel use of the fast gray matter acquisition T1 inversion recovery (FGATIR) MRI sequence to delineate the mammillothalamic tract for direct targeting of the ANT through visualizing the termination of the mammillothalamic tract in the ANT. The day prior to surgery in a 19-year-old, right-handed woman with a 5-year history of epilepsy, MRI was performed on a 3-T Siemens Prisma scanner (Siemens AG, Healthcare Sector) using a 64-channel head and neck coil. As part of the imaging protocol, noncontrast magnetization-prepared rapid gradient echo (MP-RAGE) and diffusion tensor imaging (DTI) sequences were obtained for targeting purposes. The ANT was directly targeted using the FGATIR sequence, and bilateral Medtronic 3389 leads were placed. At the last follow-up (2 months), the patient reported an approximate 75% decrease in seizure frequency, as well as a decrease in seizure severity.

Prevention of postoperative visual field defect after the occipital transtentorial approach: anatomical study.

OBJECTIVE A postoperative visual field defect resulting from damage to the occipital lobe during surgery is a unique complication of the occipital transtentorial approach. Though the association between patient position and this complication is well investigated, preventing the complication remains a challenge. To define the area of the occipital lobe in which retraction is least harmful, the surface anatomy of the brain, course of the optic radiations, and microsurgical anatomy of the occipital transtentorial approach were examined. METHODS Twelve formalin-fixed cadaveric adult heads were examined with the aid of a surgical microscope and 0° and 45° endoscopes. The optic radiations were examined by fiber dissection and MR tractography techniques. RESULTS The arterial and venous relationships of the lateral, medial, and inferior surfaces of the occipital lobe were defined anatomically. The full course of the optic radiations was displayed via both fiber dissection and MR tractography. Although the stems of the optic radiations as exposed by both techniques are similar, the terminations of the fibers are slightly different. The occipital transtentorial approach provides access for the removal of lesions involving the splenium, pineal gland, collicular plate, cerebellomesencephalic fissure, and anterosuperior part of the cerebellum. An angled endoscope can aid in exposing the superior medullary velum and superior cerebellar peduncles. CONCLUSIONS Anatomical findings suggest that retracting the inferior surface of the occipital lobe may avoid direct damage and perfusion deficiency around the calcarine cortex and optic radiations near their termination. An accurate understanding of the course of the optic radiations and vascular relationships around the occipital lobe and careful retraction of the inferior surface of the occipital lobe may reduce the incidence of postoperative visual field defect.

Anatomic Investigation of the Trajectory for Stereotactic Laser Amygdalohippocampectomy.

BACKGROUND: Magnetic resonance imaging-guided laser interstitial thermal therapy (LITT) has emerged as a promising treatment for mesial temporal lobe epilepsy. Surgeons must understand the relevant anatomy that is traversed by the catheter and affected by ablation. OBJECTIVE: To study the anatomic structures crossed by the LITT catheter until it reaches the amygdala. METHODS: Three human cadaveric heads were implanted with catheters using a frameless stereotactic technique. The Visualase® system (Medtronic, Dublin, Ireland) was utilized to ablate along the trajectory. Coronal and oblique axial slices were created. Fiber tract dissections were performed in a lateral-medial and inferior-superior scheme. Magnetic resonance tractography was acquired to illustrate the tracts dissected. RESULTS: Entry points occurred within 4 cm of the transverse and sagittal sinus, inferior to the lambdoid suture. The cortex of the inferior occipital gyrus was crossed in the region of the transverse occipital sulcus. The vertical occipital fasciculus was crossed en route to passing through the optic radiations. The catheter crossed through or inferior to the optic radiations before piercing the parahippocampal gyrus at about 4 cm from the skull. The catheter entered the hippocampus as it pierced the superior margin of the parahippocampus at 6 cm. The catheter entered the head of the hippocampus to lie inferolateral to the amygdala in the last centimeter of the trajectory. CONCLUSION: Understanding the anatomic principles of LITT catheter trajectories will improve the ability to perform this procedure. The current study is the first to examine the anatomy of this trajectory and will serve as the basis for future studies.

Midline and off-midline infratentorial supracerebellar approaches to the pineal gland.

OBJECTIVE A common approach to lesions of the pineal region is along the midline below the torcula. However, reports of how shifting the approach off midline affects the surgical exposure and relationships between the tributaries of the vein of Galen are limited. The purpose of this study is to examine the microsurgical and endoscopic anatomy of the pineal region as seen through the supracerebellar infratentorial approaches, including midline, paramedian, lateral, and far-lateral routes. METHODS The quadrigeminal cisterns of 8 formalin-fixed adult cadaveric heads were dissected and examined with the aid of a surgical microscope and straight endoscope. Twenty CT angiograms were examined to measure the depth of the pineal gland, slope of the tentorial surface of the cerebellum, and angle of approach to the pineal gland in each approach. RESULTS The midline supracerebellar route is the shortest and provides direct exposure of the pineal gland, although the culmen and inferior and superior vermian tributaries of the vein of Galen frequently block this exposure. The off-midline routes provide a surgical exposure that, although slightly deeper, may reduce the need for venous sacrifice at both the level of the veins from the superior cerebellar surface entering the tentorial sinuses and at the level of the tributaries of the vein of Galen in the quadrigeminal cistern, and require less cerebellar retraction. Shifting from midline to off-midline exposure also provides a better view of the cerebellomesencephalic fissure, collicular plate, and trochlear nerve than the midline approaches. Endoscopic assistance may aid exposure of the pineal gland while preserving the bridging veins. CONCLUSIONS Understanding the characteristics of different infratentorial routes to the pineal gland will aid in gaining a better view of the pineal gland and cerebellomesencephalic fissure and may reduce the need for venous sacrifice at the level of the tentorial sinuses draining the upper cerebellar surface and the tributaries of the vein of Galen.

The white matter tracts of the cerebrum in ventricular surgery and hydrocephalus.

OBJECTIVE The relationship of the white matter tracts to the lateral ventricles is important when planning surgical approaches to the ventricles and in understanding the symptoms of hydrocephalus. The authors' aim was to explore the relationship of the white matter tracts of the cerebrum to the lateral ventricles using fiber dissection technique and MR tractography and to discuss these findings in relation to approaches to ventricular lesions. METHODS Forty adult human formalin-fixed cadaveric hemispheres (20 brains) and 3 whole heads were examined using fiber dissection technique. The dissections were performed from lateral to medial, medial to lateral, superior to inferior, and inferior to superior. MR tractography showing the lateral ventricles aided in the understanding of the 3D relationships of the white matter tracts with the lateral ventricles. RESULTS The relationship between the lateral ventricles and the superior longitudinal I, II, and III, arcuate, vertical occipital, middle longitudinal, inferior longitudinal, inferior frontooccipital, uncinate, sledge runner, and lingular amygdaloidal fasciculi; and the anterior commissure fibers, optic radiations, internal capsule, corona radiata, thalamic radiations, cingulum, corpus callosum, fornix, caudate nucleus, thalamus, stria terminalis, and stria medullaris thalami were defined anatomically and radiologically. These fibers and structures have a consistent relationship to the lateral ventricles. CONCLUSIONS Knowledge of the relationship of the white matter tracts of the cerebrum to the lateral ventricles should aid in planning more accurate surgery for lesions within the lateral ventricles.

Fiber Tracts of the Medial and Inferior Surfaces of the Cerebrum.

OBJECTIVE: Fiber dissection studies of the cerebrum have focused on the lateral surface. No comparable detailed studies have been done on the medial and inferior surfaces. The object of this study was to examine the fiber tracts, cortical, and subcortical structures of the medial and inferior aspects of the brain important in planning operative approaches along the interhemispheric fissure, parafalcine area, and basal surfaces of the cerebrum. METHODS: Twenty formalin-fixed human hemispheres (10 brains) were examined by fiber dissection technique under ×6-×40 magnifications. RESULTS: The superior longitudinal fasciculus I, cingulum, inferior longitudinal fasciculus, uncinate fasciculus, optic radiations, tapetum, and callosal fibers were dissected step by step from medial to lateral, exposing the nucleus accumbens, subthalamic nucleus, red nucleus, and central midline structures (fornix, stria medullaris, and stria terminalis). Finally, the central core structures were dissected from medial to lateral. CONCLUSIONS: Understanding the fiber network underlying the medial and inferior aspects of the brain is important in surgical planning for approaches along the interhemispheric fissure, parafalcine area, and basal surfaces of the cerebrum.

Measuring serum matrix metalloproteinase-9 levels in peripheral blood after subarachnoid hemorrhage to predict cerebral vasospasm.

PURPOSE: We aimed to investigate serum levels of matrix metalloproteinase-9 in both subarachnoid hemorrhage and control groups for prediction of cerebral vasospasm in this study. METHODS: Venous serum matrix metalloproteinase-9 levels were prospectively measured four times (days 1, 3, 7, and 14) for 34 consecutive patients with subarachnoidal hemorrhage (n = 27) and for elective aneurysm clipping (control, n = 7). RESULTS: Vasospasm developed in 11/34 (32.4 %) patients between 3 and 10 days after subarachnoid hemorrhage (median 5.58 days), mean peak serum matrix metalloproteinase-9 compared with the non-vasospasm cohort. Matrix metalloproteinase-9 levels were higher in subarachnoid hemorrhage patients than in the controls. CONCLUSION: Increased serum matrix metalloproteinase-9 could be an accurate biomarker to predict the onset of cerebral vasospasm after subarachnoid hemorrhage.

The double massa intermedia.

BACKGROUND: To describe the rare finding of a double massa intermedia (MI). Typically, the MI (interthalamic adhesion) is a single bridge of gray matter connecting the medial surfaces of the thalami. METHODS: Twelve formalin- and alcohol-fixed human third ventricles were examined from superior to inferior by fiber dissection technique under ×6 to ×40 magnifications and with the endoscope. RESULTS: In all hemispheres, the anterior and posterior commissure were defined. The MI, which bridges the medial surfaces of the thalami, was defined in all hemispheres. In one hemisphere, there was a second bridge between the thalami, located posteroinferior to the common MI. Endoscopic view confirmed that there was a second MI in this specimen. The MI usually traverses the third ventricle posterior to the foramen of Monro and connects the paired thalami. The MI is an important landmark during endoscopic and microscopic surgeries of the third ventricle. Although a double MI is very rare, surgeons should be aware of the possibility in their surgical planning. CONCLUSION: The surgeon should be aware of the possibility of a double MI to avoid confusion during third ventricle surgery.

Microsurgical and Fiber Tract Anatomy of the Nucleus Accumbens.

BACKGROUND: The nucleus accumbens (NAc) has been a target for deep brain stimulation (DBS) in the treatment of depression and obsessive-compulsive disorder (OCD). OBJECTIVE: To examine the anatomy and connections of the NAc using a fiber dissection technique. METHODS: Ten human brains and 2 whole cadaveric heads were examined by fiber dissection technique and ×6 to ×40 surgical magnification. The NAc was examined from the lateral, medial, superior, and inferior sides to define its fiber connections and relationships with adjacent cortical and subcortical structures. Magnetic resonance imaging (MRI) with 1-mm slices was used to define its neuronavigation coordinates. RESULTS: Eight tracts, the uncinate fasciculus, cingulum, stria medullaris thalami, fornix, diagonal band of Broca, stria terminalis, medial olfactory stria, and forceps minor, form a capsule around the anterior, inferior, and medial sides of the NAc. The uncinate fasciculus connects along the inferior and adjacent part of the medial side of the NAc, the cingulum and diagonal band along the medial surface, the medial olfactory stria along the posteromedial and adjacent part of the inferior surface, the forceps minor along the anteromedial surface, and the stria terminalis, fornix, and stria medullaris along the posterosuperior surface. The subcortical gray matter related to the NAc includes the septal nuclei, indusium griseum, substantia innominata, caudate nucleus, and hypothalamus. The cortical areas communicating with and overlying the NAc are reviewed. CONCLUSION: An increased understanding of the fiber connections and neural relationships of the NAc should allow more accurate DBS targeting for the treatment of psychiatric disorders.

"Honey" can prevent epidural fibrosis development after laminectomy: an experimental study.

AIM: One of the most important causes of failed back surgery is the development of epidural fibrosis. Many methods and substances have been used to prevent the development of epidural fibrosis after laminectomy. In this study, effects of "manuka honey" on epidural fibrosis development after laminectomy was evaluated in rats. MATERIAL AND METHODS: Subjects were divided into two groups:In Group-1 (n=8);only laminectomy was carried out in the L1 level; in group-2 (n=8), laminectomy was carried out in the L1 level and manuka honey was applied to the area. The related vertebral columns were removed en bloc 6 weeks later. Leveled sections with thicknesses of 6 mm were obtained from paraffin blocks. RESULTS: In the grading made based on the fibroblast count and scar tissue degree, it was found that epidural fibrosis developed significantly less in the group-2 as compared to the group-1, and the difference was statistically significant. CONCLUSION: It was shown in our study that manuka honey reduces the degree of epidural fibrosis in rats following laminectomy. We believe that manuka honey, which can be used safely in the clinic for surgical wounds, can be used routinely to prevent development of epidural fibrosis following laminectomy.

Can recurrence of chronic subdural hematoma be predicted? A retrospective analysis of 292 cases.

BACKGROUND: Chronic subdural hematomas are the most common type of intracranial hemorrhage among the elderly. There is a substantial recurrence rate after evacuation by burr-hole surgery. In this study, we aimed to determine the predictors of recurrence after single burr-hole evacuation of chronic subdural hematomas. METHODS: We retrospectively analyzed 292 consecutive patients with chronic subdural hematoma. Clinical parameters, anamnesis, and previous anticoagulant drug use have been evaluated with univariate and multivariate analyses to determine predictors associated with recurrence. RESULTS: At least a second surgery was needed in 43 of 292 (14.7%) patients. We showed that recurrence rate was significantly higher in patients with bilateral subdural hematoma, after univariate and multivariate analyses (23.1% versus 11.4%). We did not find any significant relationship between recurrence rate and age, gender, hypertension, and/or diabetes mellitus in anamnesis, preceding head trauma, and time interval between trauma and the operation, previous anticoagulant, and/or antiaggregant therapy. CONCLUSION: After analysis of all evaluated factors, only bilateral hematoma was found correlated with high recurrence rate (p = 0.01), probably due to previous brain atrophy or existing coagulopathy.

Delayed intraventricular tension pneumocephalus due to scalp-ventricle fistula: a very rare complication of shunt surgery.

BACKGROUND: Although pneumocephalus and pneumoventricle are well known entities in neurosurgery practice, delayed intraventricular tension pneumocephalus following shunt surgery is extremely rare. CASE DESCRIPTION: A 60-year-old man presented with vomiting, drowsiness, walking difficulty, urinary incontinence and headache one month after shunt placement for communicant hydrocephalus developing secondary to aneurysmal subarachnoid hemorrhage. Skull X- Rays and Computed Tomography (CT) revealed marked air in both lateral ventricles. Neither physical and neurological examinations nor laboratory studies and cerebrospinal fluid evaluations suggested central nervous system infection. He gradually improved after repairing the scalp incision defect above the previously opened burr-hole and bed rest. CONCLUSION: In contrast to reported cases with delayed pneumocephalus developing after shunting, air entry was in skull base, air source was the scalpventricular fistula in the present case.