Lateral Supracerebellar Infratentorial Approach Research Articles

Tentorial Incision in a Lateral-medial Direction with Minimal Retraction of the Temporal Lobe in the Subtemporal Transtentorial Approach to the Middle Tentorial Incisural Space

The subtemporal transtentorial approach provides excellent exposure of the middle incisural space. A modification of the subtemporal transtentorial approach with use of a partial mastoidectomy is presented to avoid damage to the temporal lobe as a result of retraction as well as damage to venous structures. Four patients, one with a superior cerebellar artery aneurysm, one with a metastatic tumor in the midbrain, one with a tentorial meningioma, and one with a tentorial schwannoma were treated with the present approach. After subtemporal craniotomy, all of the cortical bone overlying the mastoid was removed. The mastoid air cells were drilled down, and the upper part of Trautman's triangle was exposed above the level of the lateral semicircular canal. The presigmoid dura and the temporal dura were opened and connected by incising the superior petrosal sinus. The cerebellar tentorium was incised in a lateral-medial direction along the angle of the tentorium. In each case, the tentorium was incised with minimal retraction of the temporal lobe without any damage to the temporal lobe, or venous structures. The present approach yielded excellent visualization of the lesion and adjacent neurovascular structures. In 3 of 4 cases, the lesions were successfully treated. In the patient with a tentorial schwannoma extending from the middle to posterior incisural space, the extreme lateral supracerebellar-infratentorial approach was combined with the present approach. Although additional partial mastoidectomy is time-consuming, it reduces the risk of damage to the temporal lobe as a result of retraction as well as damage to venous structures.

Auditory Midbrain Implant

The lateral suboccipital approach is a well-established route for safe removal of vestibular schwannomas in neurofibromatosis Type 2 (NF2) patients. The goal of this study was to assess if this approach can be extended to a lateral supracerebellar infratentorial approach to enable insertion of an auditory midbrain implant (AMI) penetrating array along the tonotopic gradient of the inferior colliculus central nucleus (ICC). The AMI is a new auditory prosthesis designed for penetrating stimulation of the ICC in patients with neural deafness. The initial candidates are NF2 patients who, because of the growth and/or surgical removal of bilateral acoustic neuromas, develop neural deafness and are unable to benefit from cochlear implants. The ideal surgical approach in NF2 patients must first enable safe removal of vestibular schwannomas and then provide sufficient exposure of the midbrain for AMI implantation. This study was performed on formalin-fixed and fresh cadaver specimens. Computed tomography scan and magnetic resonance imaging were used to study the heads of the specimens and for surgical navigation. The lateral suboccipital craniotomy enabled sufficient exposure of the cerebellopontine angle and internal auditory canal for tumor removal. It could then be extended to a lateral supracerebellar infratentorial approach that provided good exposure of the dorsolateral aspect of the tentorial hiatus and mesencephalon for implantation of the AMI along the tonotopic gradient of the ICC. This approach did not endanger the trochlear nerve or any major midline venous structures in the quadrigeminal cistern. This modified lateral suboccipital approach ensures safe removal of large vestibular schwannomas and provides sufficient exposure of the inferior colliculus for ideal AMI implantation.

Far lateral supracerebellar infratentorial approach for the treatment of upper brainstem gliomas: clinical experience with pediatric patients

Surgical exposure of intrinsic lesions located lateral to the brainstem still represents a challenging task. The aim of this study was to assess the feasibility of the extracerebral far lateral supracerebellar infratentorial (FLSI) approach for the treatment of gliomas located in the upper brainstem in the pediatric population. Between 1992 and 2002, seven patients (mean age 8.7 years) with tumors of glial origin (WHO I-IV) located mainly in the pontomesencephalic region were operated with the FLSI approach in a sitting position. Satisfactory extent of resection without additional morbidity was achieved. In a carefully selected pediatric patient population, the FLSI approach proved to be a feasible and effective surgical route for the treatment of upper brainstem gliomas.