Endoscopic high occipital interhemispheric transtentorial approach for lesions in the anterosuperior cerebellum, upper fourth ventricle, and upper dorsal brain stem

The occipital interhemispheric transtentorial approach: historical perspective and evolution over time

PURPOSE

Access to the pineal region has always represented a fascinating challenge to the neurosurgeons. Almost equally thrilling is the historical evolution from the hard beginnings with extremely high mortality rates to the current surgical outcomes, with excellent resection rates without long-term morbidity for most of the patients. The purpose of this paper is to provide an overview of the historical evolution of the occipital interhemispheric transtentorial (OITT) approach and its role in the development of access to the pineal region.

METHODS

Review of the literature highlights the occipital transtentorial approach from the historical context prior its description and the beginning to the current modifications and new recent insights.

RESULTS

The occipital transtentorial approach described initially by Poppen in 1966 has played a key role in the progress and success accessing the pineal area.

CONCLUSION

This historical review aims to highlight the extraordinary effort of those neurosurgeons who guided and led the development of one of the most important approaches to the pineal region.

Fully endoscopic occipital transtentorial approach for pineal region tumors

PURPOSE

Aggressive surgical resection for pineal region tumors, which is a mainstay of management in almost all cases, remains technically challenging because these tumors are located at the geometric center of the brain and surrounded by critical neurovascular structures. Therefore, any refinement in the surgical procedure is desirable. We have recently introduced an endoscope to the occipital transtentorial approach (OTA), which has been one of the most common procedures for reaching the pineal region, to overcome some of the disadvantages of the procedure, including the necessity of a relatively large skin incision and bone opening, the difficulty in orientation due to the obliqueness of the approach, the possibility of retraction injury on the occipital lobe and the corpus callosum, and blind spots at the ipsilateral wall and the roof of the third ventricle.

METHODS

We performed endoscopic OTA with corresponding advantages, including less invasiveness by virtue of a small entrance limiting the retraction of the occipital lobe, the elimination of blind spots, and the facilitation of fine manipulation based on the bright endoscopic view even at substantial depth, which is panoramic and can be magnified as needed. This procedure was substantially different from a conventional microscopic OTA, though both use a similar corridor. To maximize maneuverability within the limited space in endoscopic OTA, it was necessary to thoroughly understand each step of the procedure, as well as optimal sequence in the procedure.

RESULTS AND CONCLUSION

We found endoscopic OTA to be a promising technique for resectioning pineal region tumors, with the potential for extensive and routine application for surgeons familiar with endoscopic surgery.

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

PURPOSE

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.

MATERIAL AND METHODS

Eighty patients ranging in age from 3 months to 21 years 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.

RESULTS

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.

CONCLUSION

The posterior interhemispheric OT approach provides a safe route and comfortable access to the pineal region in children. 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.

Endoscope-Controlled High Frontal Approach for Dural Arteriovenous Fistula in Anterior Cranial Fossa

BACKGROUND

Currently, surgical obliterations are a mainstay for treating dural arteriovenous fistula (DAVF) in the anterior cranial fossa (ACF), which has high risks of hemorrhage and functional disorder. By introducing an endoscope into a high frontal approach and utilizing its advantages, we attempted to establish it as a new surgical procedure that eliminates the drawbacks of various approaches that have been used to date.

METHODS

By using 30 clinical datasets of venous-phase head computed tomography angiogram, measurements and comparisons on a 3-dimensional workstation were performed to identify the appropriate positioning of keyhole craniotomy for endoscope-controlled high frontal approach (EHFA). Based on these data, a cadaver-based surgery was simulated to verify the feasibility of EHFA and develop an efficient procedure.

RESULTS

In EHFA, though raising the position of the keyhole craniotomy made the operative field deeper, significant advantages were obtained in the angle between the operative axis and the medial-anterior cranial base and the amount of bone removal required at the anterior edge of craniotomy. Minimally invasive EHFA, performed through a keyhole craniotomy without opening the frontal sinus, proved to be feasible on 10 sides of 5 cadaver heads. Moreover, 3 patients with DAVF in ACF were successfully treated by clipping the fistula via EHFA.

CONCLUSIONS

EHFA, which provided a direct corridor to the medial ACF at the level of the foramen cecum and crista galli and the minimum necessary operative field, was found to be a suitable procedure for clipping the fistula of DAVF in ACF.

Endoscopic Occipital Transtentorial Approach for Supracerebellar Lesions

The occipital transtentorial approach (OTA), which is often applied for superior cerebellar lesions, has an inevitable risk of homonymous hemianopsia due to the retraction of the occipital lobe. The endoscopic approach provides increased visibility of the surgical field due to the wide-angled panoramic view and is minimally invasive in approaching deep brain lesions compared to the conventional microscopic approach. However, little is known regarding endoscopic OTA for the removal of cerebellar lesions. We experienced a case of a hemangioblastoma in the paramedian superior surface of the cerebellum that was successfully treated with endoscopic OTA combined with gravity retraction while avoiding postoperative visual dysfunction. A 48-year-old woman was diagnosed with a hemangioblastoma in the superior surface of the cerebellum. She underwent tumor removal with endoscopic OTA combined with gravity retraction of the occipital lobe instead of using brain retractors. The narrower space was sufficient for surgical manipulation with a panoramic view obtained by endoscopy. The simultaneous observation of the lesion with both an endoscope and a microscope revealed the superiority of infratentorial visualization with an endoscope. Gross total removal was achieved with no postoperative complications, including visual dysfunction. Endoscopic OTA may reduce the risk of postoperative visual dysfunction because of its minimally invasive nature, which is enhanced when combined with gravity retraction. Additionally, the panoramic view of the endoscope allows favorable visualization of an infratentorial lesion, which is otherwise hidden partly by the tentorium. The use of endoscopy is compatible with OTA, and endoscopic OTA could be an option for superior cerebellar lesions for avoiding visual dysfunction.

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.