Approaches to the Middle Cerebellar Peduncle for Resection of Pontine Cavernomas.

INDICATIONS CORRIDOR AND LIMITS OF EXPOSURE: The expanded retrosigmoid approach with splitting of the horizontal cerebellar fissure provides a more direct and shorter route for central and dorsolateral pontine lesions while minimizing retraction of tracts, nuclei, and cerebellum. 1-4. ANATOMIC ESSENTIALS NEED FOR PREOPERATIVE PLANNING AND ASSESSMENT: The middle cerebellar peduncle is partially covered by the petrosal surface of the cerebellum. The horizontal cerebellar fissure (petrosal fissure) divides the petrosal surface of the cerebellar hemisphere into superior and inferior parts. Splitting the petrosal fissure separates the superior and inferior petrosal surfaces and exposes the posterolateral middle cerebellar peduncle (posterior and lateral to the root entry zone of CN5). 1-4. ESSENTIALS STEPS OF THE PROCEDURE: Expanded retrosigmoid craniotomy is performed, including unroofing of the sigmoid sinus; petrosal fissure is split to expose the posterolateral middle cerebellar peduncle; entry point for resection of the cavernoma is identified; nims stimulator stimulator is used to confirm the absence of tracts and nuclei; myelotomy is performed; and cavernoma and its draining vein (but not the developmental venous anomaly) are removed using a combination of traction and countertraction against gliotic plane. PITFALLS/AVOIDANCE OF COMPLICATIONS: Wide splitting of the horizontal cerebellar fissure minimizes retraction or resection of the cerebellum and offers the best angle of attack. Knowledge of brainstem anatomy and use of intraoperative navigation are critical to avoid complications. VARIANTS AND INDICATIONS FOR THEIR USE: Far lateral through the middle cerebellar peduncle is a variant that can be used to resect pontine cavernomas if a caudocranial trajectory is preferred.The patient consented to the procedure and to the publication of her image.

Microneurosurgical Anatomic Study of the Horizontal Fissure of the Cerebellum.

OBJECTIVE: The horizontal fissure of the cerebellum, which is the largest and most prominent fissure, has received less interest from anatomists and neurosurgeons. Hence, the current study aims to provide comprehensive detail about the horizontal fissure and its anatomic and surgical relationship with deeper structures such as the dentate nucleus and middle cerebellar peduncle for the benefit of the neurosurgeon. METHODS: Ten whole formalin-fixed human cadaveric cerebellar hemispheres were obtained from human cadavers donated to the institution. Different parameters of the horizontal fissure were studied, such as length, depth (medial end, lateral end, and middle), sulcal and gyral variations (superficial and deep), and its close relationship, especially at depth, with the dentate nucleus and middle cerebellar peduncle. RESULTS: The total length of the horizontal fissure on the right and the left side was 64.3 ± 7.9 mm (range, 53-77 mm) and 65.6 ± 8.01 mm (range, 53-79 mm), respectively. The medial third of the horizontal fissure, with the fewest vessels, was the most suitable place to puncture or start the dissection of the horizontal fissure. The surface projection of the center of the posterior border of the dentate nucleus lies within 20-21 mm on either side of the posterior midline along the horizontal fissure and is only approximately 4 mm deep from the horizontal fissure. CONCLUSIONS: The anatomic measurements and relationships provided in this description of the horizontal fissure will serve as a tool for surgery selection and planning, as well as an aid to improve microneurosurgical techniques, with the final goal being better patient outcomes.

Interpeduncular Sulcus Approach to the Posterolateral Pons.

OBJECTIVE: In this article, we describe a new safe entry point for the posterolateral pons. METHODS: To show the adjacent anatomy and measure the part of the interpeduncular sulcus that can be safely accessed, we first performed a review of the literature regarding the pons anatomy and its surgical approaches. Thereafter, 1 human cadaveric head and 15 (30 sides) human brainstems with attached cerebellums were bilaterally dissected with the fiber microdissection technique. A clinical correlation was made with an illustrative case of a dorsolateral pontine World Health Organization grade I astrocytoma. RESULTS: The safe distance for accessing the interpeduncular sulcus was found to extend from the caudal end of the lateral mesencephalic sulcus to the point at which the intrapontine segment of the trigeminal nerve crosses the interpeduncular sulcus. The mean distance was 8.2 mm (range, 7.15-8.85 mm). Our interpeduncular sulcus safe entry zone can be exposed through a paramedian infratentorial supracerebellar approach. When additional exposure is required, the superior portion of the quadrangular lobule of the cerebellar hemispheric tentorial surface can be removed. In the presented case, surgical resection of the tumor was performed achieving a gross total resection, and the patient was discharged without neurologic deficit. CONCLUSIONS: The interpeduncular sulcus safe entry zone provides an alternative direct route for treating intrinsic pathologic entities situated in the posterolateral tegmen of the pons between the superior and middle cerebellar peduncles. The surgical corridor provided by this entry point avoids most eloquent neural structures, thereby preventing surgical complications.

Cerebellar Peduncle Localized Oligodendroglioma: Case Report and Review of the Literature.

BACKGROUND: Oligodendrogliomas constitute 5% of all primary brain tumors and are the third most common cancer among intracranial tumors. More than 90% of oligodendrogliomas have supratentorial localization. Oligodendrogliomas arising in cerebellar peduncle are substantially rare, <1%. Up to now, 6 oligodendroglioma cases with cerebellar peduncle localization have been presented. We aimed to discuss our World Health Organization grade II oligodendroglioma case, which originated from cerebellar peduncle in the light of literature. CASE DESCRIPTION: We report a case of 43-year-old woman. Her complaints were headache, perioral numbness and gait abnormality. Magnetic resonance imaging revealed cyst-like well-demarcated lesion localized in right cerebellar peduncle. Tumor excision was performed by turning around the tumor. CONCLUSION: It should be kept in mind that oligodendrogliomas may be present as cerebellar peduncle localized tumors.

The endovascular treatment of bilateral infarction of middle cerebellar peduncles. Etiology and endovascular treatment analysis.

Infarction of the symmetrical middle cerebellar peduncles is often induced by ischemic cerebrovascular disease. Adams described the anterior inferior cerebellar artery (AICA) syndrome as early as 1943, but clinical and imaging studies following this failed to shed more light regarding the condition until the advent of magnetic resonance imaging that comprehension regarding AICA improved significantly. Infarction of the middle cerebellar peduncles (MCP) is uncommon and the endovascular treatment of this condition is even more rare. We studied 4 patients with simultaneous bilateral cerebellar infarction of whom 2 received intracranial vascular therapy and demonstrated improvement in symptoms. Our findings suggest that patients with vertebral basilar artery stenosis with potential bilateral cerebellar infarction may benefit from endovascular treatment.

Left retrosigmoid craniotomy for cavernous malformation of the middle cerebellar peduncle.

We present a 25-year-old female with a history of multiple intracranial cavernous malformations complaining of vertigo. Imaging is significant for increasing size of a lesion in her left cerebellar peduncle. Given the proximity to the lateral border of the cerebellar peduncle, a retrosigmoid approach was chosen. After performing a craniotomy that exposed the transverse-sigmoid sinus junction, the dura was open and reflected. The arachnoid was sharply opened and cerebrospinal fluid was aspirated to allow the cerebellum to fall away from the petrous bone. The cerebellopontine fissure was then opened to visualize the lateral wall of the cerebellar peduncle. The cavernous malformation was entered and resected. The video can be found here: http://youtu.be/P7mpVbaCiJE .