IS Case 3: Bell's Palsy
Imaging Sciences URMC 2008
Publication Date: 2009-05-18
A 63-year-old male with Ramsey Hunt Syndrome seven years earlier, new Bell's palsy and new mental status changes. History of cirrhosis secondary to nonalcoholic steatohepatitis and being worked up for liver transplant.
There is T1 contrast enhancement of the left facial nerve within the internal auditory canal extending anteriorly to the geniculate ganglion. There is also suspicion of enhancement within the petrous portion of the nerve. There is no enhancement or mass effect within the brainstem.
Figures 1A&B: Coronal and sagittal T1 images. There is contrast enhancement of the left facial nerve within the internal auditory canal extending anteriorly to the geniculate ganglion. There is also suspicion of enhancement within the petrous portion of the nerve. There is no enhancement or mass effect within the brainstem.
Patients commonly present with acute onset (24 to 48 hours) of facial nerve paralysis. People may be affected at any age and are usually otherwise healthy. There is often a viral prodrome about a week before onset. Symptoms found can include taste alteration, pain in the ipsilateral ear and numbness in the ipsilateral face. Herpes simplex DNA is often recovered from facial nerve specimens. Other etiologic factors may include systemic or central polyneuropathy and immunologic or ischemic factors. Treatment usually consists of acyclovir and steroids. Almost complete denervation may be treated with CN VII decompression from the internal auditory canal fundus to the sylomastoid foramen and must be performed within two weeks for maximal effect. Post-treatment, recovery of nerve function is less with age.
The facial nerve may normally show enhancement in the geniculate ganglion, horizontal region and descending region. Normal enhancement is seen in the circumneural arteriovenous plexus around the cranial nerve VII.
Patients with Bell's Palsy have enhancement within the facial nerve in the labyrinthine region or at the fundus of the internal auditory canal, the narrowest area of nerve passage. The nerve becomes swollen and compressed in this region. Enlarged, enhancing facial nerve in the tympanic and intramastoid region may also be suspicious for Bell's palsy with fitting patient presentation.
Many limit imaging to atypical cases of Bell's palsy in which the symptoms last for more than four weeks and progression of symptoms.
Other differential diagnostic considerations of facial nerve enhancement includes schwannoma, Lyme disease, lymphoma, hemangioma, sarcoidosis, viral neuritis, Ramsay-Hunt syndrome, Guillain Barre and perineural spread of tumor. Other differential diagnoses of facial paralysis include parotid tumors, central nervous system tumors, cerebral infarct and temporal bone fracture.
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