CPA Schwannoma Presenting with Seizures and Giant Middle Fossa Mass

Background: Schwannomas are benign tumors composed of neoplastic Schwann cells and may occur in the central nervous system. Schwannomas account for ∼8% of intracranial tumors and most commonly originate from the cerebello-pontine angle in the posterior fossa while arising from cranial nerve VIII. Often, these tumors present with balance difficulties, hearing loss, or facial pain or weakness. We present two patients who presented with seizures and predominantly middle fossa masses.

Case Description: We report two unusual cases of a lateral skull base schwannomas in patients presenting with seizures. Both patients were found to have giant middle fossa masses with erosion into the petrous bone and extending into the posterior fossa through internal auditory canal. Patient 1 is a 51-year-old male with a left sided mass ([Fig. 1]). Patient 2 was a 56-year-old female with a right sided mass ([Figs. 2] and [3]). Both patients had long standing unilateral sensorineural hearing loss. Both cases were approached in a staged manor through first a middle fossa approach and later a translabyrinthine approach. Pathology reports on both tumors indicated schwannoma ([Fig. 4]). Both patients recovered well from their surgeries with minimal deficits.

Conclusion: We present two rare patients who had schwannomas of cranial nerve VIII presenting with seizures and predominate middle fossa masses. Both patients suffered from long standing unilateral sensorineural hearing loss. Schwannomas most commonly occur in the posterior fossa with nerve or brainstem compression. However, in rare occurrences they may present as a middle fossa mass with significant temporal lobe compression and seizures.

Fig. 1 MRI of the head with contrast coronal images indicating a left middle fossa mass with significant edema.

Fig. 2 MRI of the head with contrast indicating a right middle fossa mass with erosion through the petrous bone.

Fig 3 CT of the temporal bone coronal imaging indicates erosion of the right temporal bone into the Internal auditory canal.

Fig. 4 Hematoxylin and eosin pathology slide indicating the diagnosis of schwannoma based on the presence of Antoni A cells.