Nonvestibular Schwannoma Tumors in the Cerebellopontine Angle: A Structured Approach and Management Guidelines

Abstract

The most common cerebellopontine angle (CPA) tumor is a vestibular schwannoma, but one in five CPA tumors are not vestibular schwannomas. These tumors may require different management strategies. Compared with vestibular schwannomas, symptoms and signs from cranial nerve VIII are less frequent: other cranial nerve and cerebellar symptoms and signs predominate in patients with these less common CPA tumors. Computed tomography and magnetic resonance imaging often show features leading to the correct diagnosis. Treatment most often includes surgery, but a policy of observation or subtotal resection is often wiser. This review provides a structured approach to the diagnosis of nonvestibular schwannoma CPA lesions and also management guidelines.

Nonschwannoma Tumors of the Cerebellopontine Angle

“…4 Nevertheless, audiovestibular symptoms predominate. Facial pain, which is rarely seen in VS patients, can present in up to 30% of cerebellopontine meningiomas.…”

“…They grow slowly through accumulation of keratin and cholesterol from their squamous epithelial lining. 4 Their peak age of occurrence is 40 with no gender predilection. They tend to spread along normal cleavage planes and surround, not displace, cranial nerves and blood vessels.…”

“…18 These are presumably congenital malformations of the arachnoid and are histologically characterized by a cyst wall made of arachnoid or ependyma and a cystic space filled with CSF or xanthochromic fluid. 4 Their cause is unknown. On CT and MRI they appear almost identical in signal to spinal fluid.…”

Hearing disorders in brainstem lesions

“…Of the other benign cerebellopontine angle tumors, 5-13% are meningiomas, 3-6% cholesteatomas, the reminder representing schwannomas of the VIIth and other cranial nerves, arachnoid cyst, lipomas ( Fig. 29.6), and granulomas (Lalwani, 1992;Long, 1992;Tekkok et al, 1992;Nadol and Martuza, 2005;Springborg et al, 2008). Only approximately 2% of cerebellopontine angle tumors are malignant, either primary or metastatic (Brackmann and Bartels, 1980;Nakada et al, 1983;Link et al, 2002;Nadol and Martuza, 2005;Akamatsu et al, 2012), and they are characterized by rapid development of symptoms and by invasion of other structures in the area (Brackmann and Bartels, 1980;Hanabusa et al, 2001;Nadol and Martuza, 2005).…”

Minimally Invasive Endoscopic and Endoscopy-Assisted Microsurgery of Vestibular Schwannoma

“…Vestibular schwannomas have an incidence of 10 to 15 per million per year and represent the most common tumor in neurotology (Myrseth et al 2007, Zverina, 2010. These tumors account for approximately 10% of all intracranial and 80 to 95% of cerebellopontine angle tumors (Springborg et al 2008). Most commonly vestibular schwannomas occur during the fourth and fifth decades of life and with slightly higher incidence among females than males.…”