Treatment strategy for the tumor cyst of the medulla in an eloquent area: a case report and review of the literature

This is a clinical case of a 24-year-old woman with the unrescetable cystic tumor of the medulla because of eloquent area involved and severe neurological symptoms caused by the recurrent cystic component. The patient underwent emptying the cyst twice previously by means of safe entry zone myelotomy. Later there was a recurrence of the cyst with a significant neurological and oweral deterioration which is typical for such neoplasms. Recurrent cystic mass-effect was resolved with the help of newly designed device implanted. It provided simultaneous stable cisternal drainage and an opportunity for active aspiration via Ommaya reservoir.

Using the Lateral Pontine Safe Entry Zone for Resection of Deep-Seated Cavernous Malformations in the Lateral Pons: 2-Dimensional Operative Video

The retrosigmoid approach is one of the main approaches used in the surgical management of pontine cavernous malformations. It definitely provides a lateral route to large central lesions but also makes possible resection of some ventral lesions as an alternative to the petrosal approaches. However, when these vascular malformations do not emerge on surface, one of the safe corridors delimited by the origin of the trigeminal nerve and the seventh-eight cranial nerve complex can be used.1-5 Baghai et al2 described the lateral pontine safe entry zone in 1982, as an alternative to approaches through the floor of the fourth ventricle when performing tumor biopsies. They advocated a small neurotomy performed right between the emergence of the trigeminal nerve and the facial-vestibulocochlear cranial nerves complex. Accurate image guidance, intraoperative cranial nerve monitoring, and comprehensive anatomical knowledge are critical for this approach.4,5 Knowing the natural history of a brainstem cavernous malformation after bleeding,6 we sought to demonstrate in this video: (1) the use of the retrosigmoid craniotomy in lateral decubitus for resection of deep-seated pontine cavernous malformations; (2) the wide opening of arachnoid membranes and dissection of the superior petrosal vein complex to improve surgical freedom and prevent use of fixed cerebellar retraction; and (3) the opening of the petrosal fissure and exposure of the lateral pontine zone for gross total resection of a cavernous malformation in a 19-yr-old female with a classical crossed brainstem syndrome. She had full neurological recovery after 3 mo of follow-up. The patient consented in full to the surgical procedure and publication of the video and manuscript.

Posterior petrosectomy for resection of pontine cavernous malformation

Cavernous malformations (CMs) are low-pressure, focal, vascular lesions that may occur within the brainstem and require treatment, which can be a substantial challenge. Herein, we demonstrate the surgical resection of a hemorrhaged brainstem CM through a posterior petrosectomy approach. After dissection of the overlying vascular and meningeal structures, a safe entry zone into the brainstem is identified based on local anatomy and intraoperative neuronavigation. Small ultrasound probes can also be useful for obtaining real-time intraoperative feedback. The CM is internally debulked and resected in a piecemeal fashion through an opening smaller than the CM itself. As brainstem CMs are challenging lesions, knowledge of several surgical nuances and adoption of careful microsurgical techniques are requisite for success.The video can be found here: https://youtu.be/szB6YpzkuCo.

The suboccipital, telovelar, transsuperior fovea approach to dorsal pontine lesions

Dorsal pons lesions at the facial colliculus level can be accessed with a suboccipital telovelar (SOTV) approach using the superior fovea safe entry zone. Opening the telovelar junction allows visualization of the dorsal pons and lateral entry at the level of the fourth ventricle floor. Typically, a lateral entry into the floor of the fourth ventricle is better tolerated than a midline opening. This video demonstrates the use of the SOTV approach to remove a cavernous malformation at the level of the facial colliculus. This case is particularly interesting because of a large venous anomaly and several telangiectasias in the pons. Dissections in the video are reproduced with permission from the Rhoton Collection (http://rhoton.ineurodb.org).The video can be found here: https://youtu.be/LqzCfN2J3lY.

Subtemporal approach for the resection of a midbrain cavernous malformation: evaluation of safe surgical corridors

Brainstem cavernous malformation management is complex due to its critical location and deleterious effect when bleeding. Therefore, every case should be thoroughly analyzed preoperatively. We present the case of a female patient with a midbrain cavernous malformation. A comprehensive anatomical and clinical analysis of the surgical corridors is done to decide the safest route. A subtemporal approach was done and the lateral mesencephalic sulcus and vein were important anatomical landmarks to guide the safe entry zone. Nuances of technique and surgical pearls related to the safe entry zones of the midbrain are discussed and illustrated in this operative video.The video can be found here: https://youtu.be/vYA-IgiT2lU.

Posterolateral route for a midbrain cavernous malformation reaching the anterior surface of the brainstem

Cavernous malformations in the midbrain can be accessed via several safe entry zones. The accepted rule of thumb is to enter at the point where the lesion is visible at the surface of the brainstem to pass through as little normal brain tissue as possible. However, in some cases, in order to avoid critical neural structures, this rule may not apply. A different safe entry zone can be chosen. Our video presents a case of a ruptured cavernous malformation in the midbrain reaching its anterior surface which was successfully resected via a posterolateral route using the supracerebellar infratentorial approach.The video can be found here: https://youtu.be/7kt-OQuBmz0.

Median suboccipital craniotomy and telovelar approach for posterior pontine cavernous malformations

The pons is the preferred location for cavernous malformations in the brainstem. When these lesions do not surface, it is critical to select the optimal safe entry zone to reduce morbidity.1–3 In this video, we demonstrate in a stepwise manner the medial suboccipital craniotomy and the telovelar approach performed in a lateral decubitus position. They were used to successfully resect a pontine cavernous malformation in a centroposterior location in a 19-year-old patient with diplopia, right-sided numbness, and imbalance. The paramedian supracollicular safe entry zone was used once the lesion did not reach the ependymal surface.2,3 Late magnetic resonance imaging demonstrated total resection and the patient was neurologically intact after 3 months of follow-up. The approach is also demonstrated in a cadaveric dissection to better illustrate all steps.The video can be found here: https://youtu.be/ChArkxA8kig.

Fully endoscopic access and resection of hemorrhaged cavernous malformation of the posterior midbrain

Cavernous malformations in the midbrain can be accessed via several safe entry zones. The accepted rule of thumb is to enter at the point where the lesion is visible at the surface of the brainstem to pass through as little normal brain tissue as possible. However, in some cases, in order to avoid critical neural structures, this rule may not apply. A different safe entry zone can be chosen. Our video presents a case of a ruptured cavernous malformation in the midbrain reaching its anterior surface which was successfully resected via a posterolateral route using the supracerebellar infratentorial approach.The video can be found here: https://youtu.be/j7VTqRO7qd4.

Microsurgical anatomy and approaches around the lateral recess with special reference to entry into the pons

OBJECTIVEThe lateral recess is a unique structure communicating between the ventricle and cistern, which is exposed when treating lesions involving the fourth ventricle and the brainstem with surgical approaches such as the transcerebellomedullary fissure approach. In this study, the authors examined the microsurgical anatomy around the lateral recess, including the fiber tracts, and analyzed their findings with respect to surgical exposure of the lateral recess and entry into the lower pons.METHODSTen cadaveric heads were examined with microsurgical techniques, and 2 heads were examined with fiber dissection to clarify the anatomy between the lateral recess and adjacent structures. The lateral and medial routes directed to the lateral recess in the transcerebellomedullary fissure approach were demonstrated. A morphometric study was conducted in the 10 cadaveric heads (20 sides).RESULTSThe lateral recess was classified into medullary and cisternal segments. The medial and lateral routes in the transcerebellomedullary fissure approach provided access to approximately 140º–150º of the posteroinferior circumference of the lateral recess. The floccular peduncle ran rostral to the lateral recess, and this region was considered to be a potential safe entry zone to the lower pons. By appropriately selecting either route, medial-to-lateral or lateral-to-medial entry axis is possible, and combining both routes provided wide exposure of the lower pons around the lateral recess.CONCLUSIONSThe medial and lateral routes of the transcerebellomedullary fissure approach provided wide exposure of the lateral recess, and incision around the floccular peduncle is a potential new safe entry zone to the lower pons.