Bell palsy is defined as idiopathic peripheral facial paralysis, is characterised by rapid onset facial nerve paralysis, often with resolution in 6-8 weeks. As there are numerous causes of facial nerve palsy, which can be acute in onset, it is currently a diagnosis of exclusion supported by a typical presentation. MRI is not performed in all patients with a Bell palsy. It is most useful in two situations:
- decompressive surgery is being contemplated
- atypical signs and symptoms (diagnosis in question)
Enhancement of the nerve is not seen in all patients with Bell palsy. Typically long segments of the facial nerve enhance in a uniformly linear fashion. Nodularity should raise suspicion of a neoplastic cause. The facial nerve on either side of the geniculate ganglion is most frequently involved, from the distal internal acoustic meatus to the distal tympanic segment. The mastoid and extratemporal segments are less frequently involved.
The case is courtesy of Dr Hussam El-Nil, Radiology Consultant, Zagazig University.