This case illustrates the common MRI radiological features of facial nerve Schwannoma.
Facial nerve schwannomas (FNS) of facial nerve neuromas/neurilemomas, are rare benign neoplastic lesions comprising of Schwann cells 1,2. FNS can arise from anywhere along the course of the facial nerve, from its origin in the cerebellopontine angle to its extracranial ramification within the parotid gland 3. Clinical presentation depends on the extent and location of the lesion, with common presenting symptoms of progressive facial paralysis/weakness, hemifacial spasm, conductive or sensorineural hearing loss, tinnitus and dizziness 3. Other symptoms may include disturbed lacrimation (due to involvement of the greater superficial petrosal nerve), hyperacusis (nerve to stapedius muscle) and/or disturbed taste/salivation (chorda tympani) 2.
Although diagnosis is aided by radiographic studies, the convoluted course of the facial nerve from the pontomedullary junction to the stylomastoid foramen, as well as the variation in its bony confines and surrounding anatomical landscape, makes a “typical” radiological appearance impossible to describe 4.
Bone-algorithm CT, particularly through the temporal bone, shows a mass expanding or remodeling its surrounding bony boundaries 4,5.
Features of FNS on magnetic resonance imaging include 6:
- a mass that is mildly hypointense or isointense relative to brain on non-contrasted T1-weighted images
- heterogeneity and hyperintensity on T2-weighted series
- homogeneous enhancement with larger lesions with cystic degeneration seen as focal intramural low signal intensity on contrast enhanced-T1 images
Case courtesy of Associate Professor Pramit Phal