The density of vital neurologic structures in the posterior fossa requires careful assessment and treatment planning to avoid the potential for unnecessary morbidity and mortality. Although the angioblastic variant has been associated with more aggressive behavior, there is no significant correlation between the other histologic subtypes and clinical behavior. In the posterior fossa, they usually arise on the posterior surface of the petrous bone, near the porous acusticus, or along the lateral venous sinus. Variable shapes with irregular patterns Frequently develop multiple fingerlike projections between cranial nerves and brainstem fissures and sulci May extend through the tentorium into the middle fossa, forming a dumbbell shape Facial and lower cranial nerve schwannoma arise from Schwann cells anywhere along the course of the nerve. May present with cranial nerve or cerebellar dysfunction that develops over a number of years.
Hemifacial spasm is relatively common.
Large tumors may cause deficits of all the lower cranial nerves. Due to the location of these tumors within the CPA with the significant number of closely associated vital neurologic structures, the risk of complications from cranial nerve damage and brainstem compression increases with delays in diagnosis and treatment. Patient age and medical condition, specific tumor growth rate, and pathologic behavior are taken into account when recommending a mode of therapy. Surgical resection is considered for any patient in good medical condition with a benign or malignant lesion in the CPA if the boundaries of the tumor are resectable with minimal risk to the local neurological structures. Surgical resection renders the greatest chance for complete tumor eradication of the vast majority of CPA lesions.