Diagnostic Paradox behind Facial Nerve Schwannoma

Abstract

Background: Schwannomas are benign and slow growing tumors that arise from the Schwann cells which ensheath the axons of peripheral nerve, cranial nerve and autonomic nervous system. A schwannoma of facial nerve may originate from extra or intra cranial segments of the nerve. Most of the facial nerve schwannomas originate from intra-tympanic region. In decreasing order of their frequency, schwannomas were found along the tympanic, mastoid (vertical), labrynthine and meatal segments of the facial nerve. It is an extremely rare entity as malignant degeneration of schwannomas is not frequent. A high level of clinical suspicion with detailed neuro-otological and radiological studies play important role in preoperative diagnosis of schwannomas.

Facial Palsy, Radiographic and Other Workup Negative

“…These benign tumors are usually detectable by a contrasted temporal bone MRI that includes the entire course of the facial nerve, which may demonstrate a focal facial nerve enhancement, or by noncontrast fine-cut CT of the temporal bones, which may demonstrated facial nerve enlargement and widening of the facial nerve canal. 7,8 Rare benign facial nerve tumors such as glomus faciale within the fallopian canal causing progressive facial palsy have also been reported. 9…”

“…These benign tumors are usually detectable by a contrasted temporal bone MRI that includes the entire course of the facial nerve, which may demonstrate a focal facial nerve enhancement, or by noncontrast fine-cut CT of the temporal bones, which may demonstrated facial nerve enlargement and widening of the facial nerve canal. 7,8 Rare benign facial nerve tumors such as glomus faciale within the fallopian canal causing progressive facial palsy have also been reported. 9 Slow-onset facial palsy accompanied by facial pain or otalgia that does not resolve, zonal (frontal, periorbital, midface, or lower lip weakness) or progressive facial palsy, other cranial neuropathies particularly of cranial neuropathy (CN) V, or a unilateral serous otitis media raises suspicion for an occult malignancy and merit fine-cut CT and MRI imaging along the course of the facial nerve.…”