Diagnostic Considerations
Hemimasticatory spasm
Hemimasticatory spasm is analogous to hemifacial spasm and occurs with irritation to the motor trigeminal nerve. This rare condition is a segmental myoclonus and presents with unilateral involuntary contractions of the trigeminally innervated muscles of mastication (usually the masseter). Similar to hemifacial spasm, hemimasticatory spasm responds to treatment with medications and botulinum toxin. However, less evidence exists that exploratory surgery benefits patients with this condition. [5]
Myoclonic movements
Myoclonic movements affecting facial musculature also may arise from lesions at the brain or brainstem level. These are distinguished from hemifacial spasm by the distribution of abnormal movements (more generalized, possibly bilateral) and possibly by electrodiagnostic evaluation. Imaging studies may yield an underlying cause. Central myoclonus responds to anticonvulsant management.
Oromandibular dystonia
Oromandibular dystonia refers to dystonia affecting the lower facial musculature, predominantly the jaw, pharynx, and tongue. When oromandibular dystonia occurs in conjunction with blepharospasm, the disorder is termed Meige syndrome.
Jaw-opening forms of oromandibular dystonia indicate primary involvement of the digastric and lateral pterygoid. Jaw-closing oromandibular dystonia involves the masseter, temporalis, and medial pterygoid. Jaw deviation, indicating predominant involvement of the lateral pterygoid, is rare.
Botulinum toxin is the preferred treatment for oromandibular dystonia and is most effective in the jaw-closure type. Medications seldom yield acceptable results. When medications must be used, employ the same agents as for blepharospasm. [6] Because of the risk of aspiration, never inject botulinum toxin into the tongue.
Craniofacial tremor
Craniofacial tremor may occur in association with essential tremor, Parkinson disease, thyroid dysfunction, or electrolyte disturbance. It occurs rarely in isolation. Focal motor seizures must occasionally be distinguished from other facial movement disorders, particularly hemifacial spasm. Postictal weakness and greater involvement of the lower face are distinguishing features of focal motor seizures.
Facial chorea
Facial chorea occurs in the context of a systemic movement disorder (eg, Huntington disease, Sydenham chorea). Chorea is a random, flowing, nonpatterned set of movements. A related disorder, spontaneous orofacial dyskinesia of the elderly, is observed primarily in the edentulous. It usually responds to proper fitting of dentures.
Tics
Facial tics are brief, repetitive, coordinated, semipurposeful movements of grouped facial and neck muscles. Tics may occur physiologically or in association with diffuse encephalopathy. Some medications (ie, anticonvulsants, caffeine, methylphenidate, antiparkinsonian agents) are associated with producing tics. Single, repetitive, stereotyped movements (eg, repetitive grimacing, throat clearing, vocalizations) define a simple tic disorder.
Facial myokymia
Facial myokymia appears as vermicular twitching under the skin, often with a wavelike spread. This is distinguished from other abnormal facial movements by characteristic electromyogram discharges presenting as brief, repetitive bursts of motor unit potentials firing at 2-60 Hz interrupted by periods of silence of up to a few seconds. Facial myokymia may occur with any brainstem process. Severe cases may benefit from botulinum toxin. Most cases are idiopathic and resolve without treatment over several weeks.
Tardive dyskinesia
Tardive dyskinesia appears as bilateral, irregular, and non-synkinetic muscular contractions. It occurs in the setting of medication use, usually antipsychotics.
Differential Diagnoses
