There are 12 pairs of cranial nerves responsible for transmitting signals of the different senses and controlling different organs of your body. The 7th cranial nerve controls facial muscles involved in facial expressions, and the movement of the eyes, eyebrows, lips and mouth. Hemifacial spasm is a condition characterized by involuntary twitching of the muscles on one side of the face without any pain. The twitching may start near your eye and move down the face or from your chin upward.
The underlying cause of this condition is an injury or compression of the facial nerve by a blood vessel or tumour. It may be associated with other conditions that involve the facial nerves such as Bell’s palsy (paralysis of the facial nerve) or trigeminal neuralgia (severe facial pain).
Diagnosis involves reviewing your medical history and performing a thorough neurological examination. Your doctor may order other tests such as an MRI scan to rule out aneurysms and brain tumour, electromyogram (EMG) to measure muscle activity and nerve conduction velocity (NCV) to test electrical activity of the nerve.
Treatment involves medication such as muscle relaxants and anti-convulsant drugs to relieve pain and block the misfiring of the nerve which is causing contraction of the facial nerve. Botox injections may also be indicated. Surgery is recommended when conservative treatments fail. Microvascular decompression is a surgical technique where the affected nerve is decompressed by placing a surgical sponge between the nerve and the blood vessel compressing the nerve.