Hemifacial spasm

Definition

• Involuntary irregular tonic or clonic movements of the facial muscles innervated by the facial nerve on one side of the face.

Aetiology

• Compression of the facial nerve at the root exit zone

• Vascular compression (most common)

o AICA

o PICA

o Vertebrobasilar

o Internal auditory artery

• Demyelination

• Tumours

• Cysts

Clinical

• Facial twitches usually begin in the periocular region and can progress to involve check and perioral muscles

• Rarely bilateral and if so always asynchronous

• Weakness can develop over time.

DDX

• Blepharospasm

o Usually bilaterally and only involving the eyelids

• Facial tic (Tourette’s syndrome)

o Tend to be multifocal and not unilateral, more complex movements, premonitory sensation, voluntary supression

• Post-Bell’s palsy synkinesis

• Focal seizures

• Oromandibular dystonia

o Cranial dystonia

o Referred to as Meige’s syndrome in combination with blepharospasm

o Idiopathic or often associated with neuroleptic exposure

o Jaw can be pulled in any direction

• Hemimasticatory spasm – very rare

o Affects jaw closure, painful spasm

o Disorder of trigeminal nerve (?a motor version of TGN)

• Myokymia

o Eyelid myokymia – common, benign

o Facial myokymia

- Fine rippling movement of facial muscles associated with brainstem abnormality

Investigations

• All patients should get MRI with specific brainstem imaging

Treatment - other

Medications

• May provide some benefit, although often not enough to tolerate SE:

o Baclofen

o Clonazepam

o Carbamazepine

o Phenytoin

Surgical

• Microvascular decompression (if vascular cause suspected)

• Success rates 88-97%

• Possible complications – hearing loss and facial weakness

Treatment - Botox

• Beneficial in 90% of patients

• Onset 3 days to 2 weeks, peak 2-3 weeks, mean duration 2.8 months (although large variability)

• Considerations

o Avoid middle of upper lid (pretarsal) to reduce risk of ptosis

o Caution with zygomaticus major given effect on lip droop

o Consider injecting other side to achieve symmetry

• Total doses:

o Up to 34 units Botox (or 160 units dysport)

Potential Side effects

• Erythema

• Bruising (including ‘Black eye’)

• Dry eyes

• Ptosis

• Diplopia

• Lid oedema

• Mouth droop

• Facial muscle weakness