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.