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Lesley French Childs, Daniel Novakovic,
and Scott R. Gibbs

Hemifacial spasm is a disorder of recurrent, involuntary twitches of facial muscles that are peripherally induced. A disorder that typically begins in middle age and more commonly in women, hemifacial spasm often first involves the orbicularis oculi and spreads slowly to other facial muscles. There is a progression seen from increased blinking initially to forced closure of the eyelids. Later, twitching of the lower face can develop. The most common spasms include eye closure and mouth retraction/elevation. The longer the duration of the disorder, the more likely it is for patients to develop midfacial weakness as well. Although it is benign, this disorder affects patients both cosmetically and functionally. Unfortunately, the disorder is chronic, with only rare reports of spontaneous recovery. Defazio et al1 describes two patients in a series of 65 patients who experienced complete and long-lasting symptom relief during their second or third year of treatment with botulinum neurotoxin (BoNT). In a Cochrane review, only one randomized placebo-controlled trial involving 11 people was identified; it this was performed by Yoshimura et al in 1992. Indeed, BoNT treatment was noted to be superior to treatment with a placebo. This, in combination with numerous other case series, suggests that BoNT is effective and safe for treating hemifacial spasm. The paucity of placebo-controlled trials comparing the efficacy of BoNT with placebo is likely due to the significant success of treatment with the toxin reported in open studies. Researchers likely would find it ethically difficult to randomize patients to simply examine efficacy. However, further trials to evaluate the technique of injection, dose, immunogenicity, and long-term efficacy would provide value.2

The etiology is thought to be due to vascular compression of the facial nerve by an aberrant vascular loop, specifically the posterior inferior cerebellar artery (PICA). Other causes of compression include tumors or vascular malformations. After vascular pressure has been exerted on the facial nerve, a secondary demyelination is thought to ensue. In an article investigating unusual causes of hemifacial spasm, specifically those other than vascular compression at the root exit zone of the facial nerve, Han et al³ emphasizes radiologic investigations for achieving accurate diagnoses. Specifically, cases of tumor compression, vascular malformation, and dolichoectatic vertebrobasilar arteries are discussed.

Treatment for hemifacial spasm includes oral doses of antiepileptic drugs (such as carbamazepine and baclofen as well as benzodiazepines), neurosurgical decompression of the seventh cranial nerve, or intramuscular BoNT injections. The BoNT injections avoid the need for oral medications, with their associated side effects and limited efficacy, as well as the risks associated with a major intracranial operation.⁴ In the neurosurgical literature, Kong and Park⁵ report that in numerous reported series, deafness occurred in 1.6 to 2.6% of cases and permanent facial weakness occurred in 3.4 to 4.8% of those undergoing microvascular decompression. Because of the potential complications and the possibility of recurrence of spasms, most patients and physicians prefer using BoNT for long-term management of hemifacial spasm. In fact, much evidence supports the use of BoNT as the first-line treatment for hemifacial spasm.⁶

Recently, Rudzińska et al⁷ noted that the often-associated sensory and autonomic complaints of hemifacial spasm also responded to treatment with BoNT. Specifically, tearing, eye irritation, and a “clicking” sound (attributed to contractions of the stapedius muscle) were reduced after treatment with the toxin. This finding is likely due to the interference of transmission at the cholinergic synapses of the parasympathetic and post-ganglionic sympathetic nervous system.⁷

Facial Synkinesis

One of the most troubling sequelae of facial nerve paralysis is synkinesis, which is the presence of unintentional motion in one area of the face produced during intentional movement in another area of the face. Synkinetic movements can be socially debilitating and can also be quite painful, with simultaneous spasm of multiple muscle groups. The most common form of synkinesis is oculo-oral, involving involuntary oral commissure movement with voluntary eye closure.

The etiology of synkinesis is thought to be multifactorial, with evidence supporting the role of aberrant axonal regeneration as well as central involvement in the form of facial nucleus hyperexcit-ability. Bajaj-Luthra et al⁸ quantitatively analyzed the patterns of synkinetic facial movements on both the affected and unaffected sides. Patients with oculo-oral synkinesis were noted to have increased modiolar motion during eye closure relative to controls. (The modiolus is where several facial muscles converge toward a focus, just lateral to the buccal angle, to form a fibromuscular mass with three-dimensional mobility.) More specifically, in patients with synkinesis, the modiolar motion was noted to be asymmetric and increased in the horizontal and vertical planes. In consideration of both the affected and unaffected sides of the face, Neely et al9 have described two types of synkinesis: synergistic synkinesis, in which movement on the affected side is similar to what might be seen on the unaffected side, but in excess thereof; and paradoxical synkinesis, in which the secondary facial movement is in a direction considered antagonistic to normal facial movement.

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