Suboccipital Transhorizontal Fissure Approach for Posterior Cranial Fossa Lesions: A Cadaveric Study and First Clinical Experience

BACKGROUND Surgical treatment of pathological lesions in the deep cerebellar hemisphere, cerebellopontine angle (CPA), and fourth ventricle of the posterior cranial fossa (PCF) is challenging. Conventional neurosurgical approaches to these lesions are associated with risk of various complications. Mastery of efficient fissure dissection is imperative when approaching deep-seated lesions. The horizontal fissure (HF) is the largest and deepest fissure of the cerebellum. OBJECTIVE To conduct an anatomical study and introduce a novel suboccipital trans-HF (SOTHF) approach to access lesions of the deep cerebellar hemispheres, CPA, and upper fourth ventricle of the PCF. METHODS We performed a cadaveric dissection study focusing on anatomical landmarks and surgical feasibility of the SOTHF approach then implemented it in 2 patients with a deep cerebellar hemispheric tumor. RESULTS Anatomical feasibility of the SOTHF approach was demonstrated and compared with conventional approaches in the cadaveric study. Opening the suboccipital surface of the HF to create medial, intermediate, and lateral surgical corridors provided optimal viewing angles and wide access to the deep cerebellar hemispheres, CPA, and upper fourth ventricle without heavy cerebellar retraction. Sacrificing cerebellar neural structures and complex skull base techniques were not required to obtain adequate exposure. The SOTHF approach was successfully applied without complication in 2 patients with a deep cerebellar hemispheric tumor. CONCLUSION The HF is an important cerebellar fissure that provides a gateway to deep areas of the PCF. Further studies are needed to define and expand applications of the SOTHF approach.

Endoscopic resection through a retrosigmoid transmeatal approach of a large-sized vestibular schwannoma: operative video and technical nuances

Surgical management of vestibular schwannomas has improved over the last 30 years. Whereas in the past the primary goal was to preserve the patient’s life, today neurological function safeguarding is the main objective, with numerous strategies involving single resection, staged resections, postoperative radiosurgery, or single radiosurgery. The retrosigmoid approach remains the primary pathway for surgical access to the cerebellopontine angle (CPA). The use of an endoscope has great advantages. It contributes to the visualization and resection of residual tumor and also reduces the need for cerebellar retraction. The authors present a fully endoscopic resection of a large-sized vestibular schwannoma with facial nerve preservation. The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID21106

Combined Microscopic-Endoscopic Transmastoid Resection of a Petrous Meningioma: 2-Dimensional Operative Video

Petrous meningiomas are defined as tumors with a basal dural attachment on the posterior surface of the petrous bone.1 Their insertion can be anterior to the meatus (petrous apex meningiomas), or posterior to the meatus, with associated hyperostotic bony invasion either pre- or retro-meatal.2 These meningiomas are amenable to curative surgical removal and have better surgical outcomes than more medially located true petroclival meningiomas that originate medial to the fifth nerve.2-4 They, however, remain challenging because of their close relationship to critical neurovascular structures in the cerebellopontine angle.5 The posterior petrous meningiomas might reach a significant size with compression of the cerebellum, the brainstem, and involvement of the cranial nerves, and extend posteriorly to the transverse sigmoid sinus.2,6 Transmastoid approach with skeletonization and lateral reflection of the transverse sigmoid sinus provides a superb exposure without cerebellar retraction.6,7 The ease and complete resection of the tumor and invaded bone can be facilitated by combined microscopic-endoscopic techniques. We demonstrate these principles through the resection of a petrosal meningioma in a 56-yr-patient who presented with headaches, nystagmus, and mild cerebellar signs. The patient consented to the procedure. Image at 1:36 reprinted with permission from Al-Mefty O, Operative Atlas of Meningiomas. Vol 1, ©LWW, 1998.

Endoscopic supracerebellar infratentorial approach to pineal region epidermoid tumor

Epidermoid cysts of the pineal region are a rare entity. Herein, the authors describe the endoscopic resection of a recurrent pineal region epidermoid by way of a supracerebellar infratentorial approach. The patient was positioned in the semiseated upright position with head tilted to the right and slightly flexed, maximizing gravity-based cerebellar retraction, and a paramedian craniotomy was performed owing to the gradual flattening of the tentorium from medial to lateral. This setup, in tandem with the enlarged viewing window achieved by use of 0°, 30°, and 70° endoscopes, afforded the necessary access to achieve a satisfactory resection through this anatomical corridor. The video can be found here: https://stream.cadmore.media/r10.3171/2021.4.FOCVID2131.

Radical Resection of a Giant Epidermoid Tumor Associated With Miniature Chordoma Utilizing a Combined Endoscopic-Microscopic Technique: 2-Dimensional Operative Video

Epidermoid tumors arise from misplaced squamous epithelium and enlarge through the accumulation of desquamated cell debris.1 Notwithstanding the prevailing conservative attitudes to minimize morbidity, optimal treatment consists of total removal of the capsule2,3; therefore, giant and multicompartmental tumors are particularly challenging. The utilization of simultaneous endoscopic microscopic techniques by tandem endoscopic and microscopic dissection to overcome the shortcomings of both modalities, markedly enhances the ability of radical removal,4 thus eliminating or at least long-delaying inevitable recurrences with subsequent accumulated morbidity. The transmastoid approach by skeletonizing and reflexing the transverse-sigmoid sinus offers wide exposure of the cerebellopontine angle avoiding cerebellar retraction and allowing 4-hands dissection.5 The patient is a 17-yr-old male with a giant epidermoid tumor in the cerebellopontine angle, extending through the incisura. The patient underwent surgical resection with maximum pursuit of the epithelial capsule. After removing the epidermoid tumor, a miniature intra and extradural midclival tumor was encountered and removed with a proven pathology of chordoma. Patient did well postoperatively with relief of his hemifacial spasms. Patient consented for surgery and photograph publication. Image at 1:23, ©1997, O. Al-Mefty, used with permission. All rights reserved.

Endoscope Assisted Microvascular Decompression: Are the Advantages Still Worthy Towards More?

Background Microvascular decompression is the definitive treatment of various neuralgias affecting cranial nerves. The compression on a cranial nerve could be at the root entry zone, especially the trigeminal nerve. Endoscope-assisted microsurgery may help avoid missing a hidden vascular structure. Study design Retrospective clinical case series. Patient and methods Twenty-five patients with facial pain and five patients with hemifacial spasm constituted this study. FIESTA MRI was the pre-operative neuroimaging modality. Retrosegmoid craniectomy was done for all patients. Microscope was initially used for exploration and arachnoid dissection around the nerve. The endoscope was applied thereafter for exploration and confirmation of the proper insertion of the Teflon. Results Using the endoscope, cerebellar retraction was reduced by 0.5 to 0.8 cm in 90% of patients. Root entry zone and entry of the nerve through the corresponding skull base foramen was clearly visualized by the endoscope. Endoscope enabled a wider area of exploration and panoramic view, which could not be obtained by the microscope. Patients with trigeminal neuralgia had a median pre-operative VAS of 9, while it was only 1 in early post-operative and 0 in 6-month post-operatively. Patients with HFS were completely recovered. Conclusion The advantages of microvascular decompression are still worthy. Complications are minimal, and the view is much more panoramic. The different viewing angles and ability to directly reach corners is an absolute endoscopic advantage. Therefore, avoidance of missing vascular structures and incomplete recovery can be assured.

Contralateral supracerebellar transtentorial approach for a thalamic cavernous malformation resection: operative video

This video illustrates a contralateral supracerebellar transtentorial (cSCTT) approach for resection of a ruptured thalamic cavernous malformation in a 56-year-old woman with progressive right-sided homonymous hemianopsia. The patient was placed in the sitting position, and a torcular craniotomy was performed for the cSCTT approach. The lesion was resected completely. Postoperatively, the patient had intact motor strength and baseline visual field deficits with moderate right-sided paresthesias. The cSCTT approach maximizes the lateral surgical reach without the cortical transgression seen with alternative transcortical routes.1 Contralaterality is a defining feature, with entry of the neurosurgeon’s instruments from the craniotomy edge of the craniotomy, contralateral to the lesion, allowing access to the lateral aspect of the lesion. The sitting position facilitates gravity-assisted cerebellar retraction and enhances the superior reach of this approach (Used with permission from Barrow Neurological Institute, Phoenix, Arizona).The video can be found here: https://youtu.be/lqB9mu_T8NQ.

Translabyrinthine Approach for Resection of Large Cystic Acoustic Neuroma: Operative Video and Technical Nuances of Subperineural Dissection for Facial Nerve Preservation

The translabyrinthine approach is advantageous for the resection of large acoustic neuromas compressing the brainstem when hearing loss is nonserviceable. This approach provides wide access through the presigmoid corridor without prolonged cerebellar retraction. Early identification of the facial nerve at the fundus is also achieved. In this operative video atlas manuscript, the authors demonstrate a step-by-step technique for microsurgical resection of a large cystic acoustic neuroma via a translabyrinthine approach. The nuances of microsurgical and skull base technique are illustrated including performing extracapsular dissection of the tumor while maintaining a subperineural plane of dissection to preserve the facial nerve. This strategy maximizes the extent of removal while preserving facial nerve function. A microscopic remnant of tumor was left adherent to the perineurium. A near-total resection of the tumor was achieved and the facial nerve stimulated briskly at low thresholds. Other than preexisting hearing loss, the patient was neurologically intact with normal facial nerve function postoperatively. In summary, the translabyrinthine approach and the use of subperineural dissection are important strategies in the armamentarium for surgical management of large acoustic neuromas while preserving facial nerve function.The link to the video can be found at: https://youtu.be/zld2cSP8fb8.

Lateral Basal Approach to CPA in Supine No-Retractor Method: Microvascular Decompression for Hemifacial Spasm

Objectives In this video, we demonstrate our more basal approach in microvascular decompression for hemifacial spasm. Design The patient is in supine position with the head rotated maximally to the opposite side on the U-shaped head rest. The small cranial window is made at the lateral bottom of occipital cranium with the adequate superficial manipulation on the muscles layers in the craniocervical junction. Results The more basal approach enables the surgeon to access all the segments of the VIIth nerve tract without cerebellar retraction by spatula, especially in the case with vertebral artery associated compression. Conclusion This approach safely provides the ideal operative corridor promising sufficient decompression in micorvascular decompression for the VIIth nerve.The link to the video can be found at: https://youtu.be/_nKSjGEHoB4.