Surgical outcome in cystic vestibular schwannomas

Abstract

Background: Cystic vestibular schwannomas (VS) form a rare subgroup that differs from the solid variant clinically, radiologically, and histopathologically. These tumors also vary in their surgical outcome and carry a different risk of post-operative complications. We analyzed our series of 64 patients with cystic VS and discuss the technical difficulties related to total excision of these tumors and focus on complication avoidance.

Materials and methods: A retrospective review of cystic VS surgically managed over a span of 11 years. The case records were evaluated to record the clinical symptoms and signs, imaging findings, surgical procedure, complications, and follow-up data. Post-operative facial nerve palsy was analyzed with respect to tumor size and tumor type.

Results: Progressive hearing impairment was the most common initial symptom (76.6%). Atypical initial symptoms were present in 15 patients (23.4%). Preoperatively, 78% patients had good facial nerve function (HB grade 1, 2) and 22% had intermediate (HB grade 3, 4) to poor (HB grade 5 and 6) function. Mean tumor size was 4.1 cm. Complete tumor removal was achieved in 53 patients (83%). The facial nerve was anatomically intact but thinned out after tumor excision in 38 patients (59.4%). Ninety percent patients had either intermediate or poor facial nerve function at follow-up. Poor facial nerve outcome was associated with giant tumors and peripherally located, thin-walled cystic tumors.

Conclusion: Resection of cystic VS is complicated by peritumoral adhesions of the capsule to the nerve. Extensive manipulation of the nerve in order to dissect the tumor-nerve barrier results in worse facial nerve outcome. The outcome is worse in peripherally located, thin-walled cystic VS as compared to centrally located, thick-walled cystic tumors. Subtotal excision may be justified, especially in tumors with dense adhesion of the cyst wall to the facial nerve in order to preserve nerve integrity.

Keywords: Cystic vestibular schwannoma; facial nerve palsy; vestibular schwannoma.

Figure 1

Piccirillo type A3 cystic VS. non-contrast CT (a) demonstrating a hypodense lesion in the right cerebellopontine angle with hyperdensity, suggestive of bleed within the tumor. Post-contrast CT (b) done after six years did not reveal any tumor recurrence

Figure 2

Piccirillo type A1 cystic VS. plain CT (a) demonstrating a heterogenous density lesion in the left cerebellopontine angle. Axial post-gadolinium MR image (b) showing the polycystic nature of the tumor. Post-operative CT (c) with specks of blood at the operative site. Post-contrast CT (d) four years after surgery showing ring enhancement at the internal auditory meatus suggestive of recurrence. This patient was kept on follow-up imaging

Figure 3

Piccirillo type B2 cystic VS. plain (a) and contrast CT (b) brain showing a hypodense lesion in right cerebellopontine angle with enhancing solid component near the meatus, enhancing cyst wall and evidence of fluid level. Sagittal (c) and coronal (d) post-gadolinium MR images demonstrating a cyst with rim enhancement. Immediate post-excision CT (e) and one (f) taken four years after surgery showing no evidence of tumor

Figure 4

Piccirillo type A2 cystic VS. (a, b) CT brain showing a large hypodense lesion in the left cerebellopontine angle with an isodense solid component within. The septations within the cyst and the wall reveals prominent enhancement following contrast administration. Sagittal MR image (c) demonstrating the multicystic nature of the tumor and its vertical extent. CT (d) done at 6 months after surgery revealing a large pseudomeningocele that was managed with a lumboperitoneal shunt