Hemifacial spasm secondary to vascular loop compression: a rare case report.

Hemifacial spasm (HFS) is characterised by brief, persistent, involuntary paroxysmal contractions of the facial muscles innervated by the facial nerve. Broadly its aetiology is portrayed as primary and secondary. Primary HFS is a result of vascular compression of the ipsilateral facial nerve at its root exit zone, and secondary HFS can occur after any injury to the facial nerve from the internal auditory canal to the stylomastoid foramen, which may be a result of a cerebellopontine angle tumour, schwannoma, fusiform aneurysm, or demyelinating lesion such as multiple sclerosis. We report a rare case of HFS in a 40-year-old female patient, who presented with a 4-year history of twitching of the left eye and deviation of the mouth towards the left side. An MRI of the brain revealed a vascular anomaly at the root exit zone of the left facial nerve. The present report aims to highlight MRI as a single, non-invasive diagnostic investigation to confirm the diagnosis of HFS.