3.1 Introduction

Dystonias of the facial region can be classified in a variety of ways. Dystonic movement disorders can affect the upper face, midface, lower face, and/or cervical region in a variety of combinations. To add to the complexity of the presentation, individual dystonias present with a variety of age ranges, frequency, and penetrance. As there is a varied presentation of dystonias of the facial/cervical region, several common facial dystonias and similar craniofacial muscle disorders are briefly described in this chapter, and basic treatment options are reviewed. Specific disorders are covered in further depth in separate chapters later in this book.

Benign essential blepharospasm or BEB is a focal dystonia that results in an involuntary closure of the musculature around the eye. BEB may include involuntary closure solely, or twitching, and repetitive movements in conjunction with closure. This involuntary movement is typically chronic and persistent in nature, resulting in a functional blindness in which there is an intact visual pathway. BEB is rare (1 in 20,000); when it occurs it tends to do so in the fifth and sixth decades of life. Botulinum neurotoxin injection to the local musculature has proven clinically effective in many reported trials. ^{1 ,​ 2 ,​ 3} The current recommendation from the American Academy of Neurology is that botulinum neurotoxin is probably effective for BEB and should be considered for first-line treatment. ⁴

Hemifacial spasm, first described by Gowers in 1884, is not a dystonia but a segmental myoclonus resulting in a recurrent, involuntary, synkinetic dystonic muscular contraction of the face. The muscles in contracture are those innervated by the facial nerve and are generally unilateral as is evident in its description. There are rare cases of bilateral involvement (less than 5% per reports). It typically occurs in the fourth and fifth decades of life with a prevalence of 1 in 10,000, and usually first presents in the orbicularis oculi. The most common cause of facial nerve interruption is believed to be an aberrant vascular loop (from the posterior inferior cerebellar artery) causing local compression. ⁵ Other causes of compression may include local tumor, vascular malformation, and infectious processes. ⁶ Hemifacial spasm can be misdiagnosed as isolated blepharospasm, orbicularis oculi myokymia, or synkinetic movements post-Bell palsy. In a recent study, 62% were primary vascular causes, 2% were hereditary causes, 19% were secondary causes (Bell palsy, facial nerve injury, demyelination, brain infarcts), and 18% were mimicking causes (psychogenic, tics, dystonias, myoclonus, and hemimasticatory spasm). ⁷

Given the propensity for misdiagnosis, it is important to thoroughly evaluate all dystonias for an accurate diagnosis. Anticonvulsive medication, such as oral doses of carbamazepine or valproic acid, helps control central myoclonus. Intramuscular injection of botulinum toxin reliably reduces synchronous spasms in a safe, repeatable way. ^{7 ,​ 8 ,​ 9} Defazio et al reported a 95% response rate in the effectiveness of botulinum toxin A in relieving the symptoms of primary hemifacial spasm. ¹⁰ In the case of vascular compression, surgical intervention is recommended when a localizing cause is identified.

Oromandibular dystonia (OMD) is characterized by dystonic muscular contractions affecting the jaw, mouth, and lower face. In more severe cases, the tongue musculature may be involved. In patients with OMD, involuntary contractions may involve the muscles that open the jaw, close the jaw, and the muscles of mastication. This leads to a significant variety of presentations in OMD. Associated findings may include spasms of jaw closure with difficulty opening the mouth; jaw clenching and/or bruxism; spasms of jaw opening; and sideways deviation and/or protrusion of the jaw. Additional symptoms may also be present, such as lip tightening/pursing; retraction of the corners of the mouth; and deviation and/or protrusion of the tongue. Because these findings are varied in presentation but localized, many patients with OMD may present with jaw pain, eating difficulties, or dysarthria. In a recent retrospective study, the mean age of onset was 51 years with a 2:1 female predominance with 62% having jaw-opening OMD, 20% with jaw closing, and 18% with mixed form of OMD. Lingual dystonia was present in 27% of the OMD patients. ¹¹

Dystonic spasms can sometimes be provoked by certain activities such as talking, chewing, or biting. There have been reported incidences of medications predicating orofacial dystonia or tardive dystonia, such as weak serotonin reuptake inhibitor, but no exact mechanism has been found. ^{8 ,​ 11} Particular sensory tricks may help temporarily alleviate a patient’s OMD symptoms. Reports of successful sensory tricks include chewing gum, talking, placing a toothpick in the mouth, lightly touching the lips or chin, or applying steady pressure in the submental region. Dystonic spasms may extend to involve nearby areas including the muscles of the eyelids, nose, neck, or vocal cords. Although some medications have been used, their efficacy is low in OMD. Botulinum toxin is the preferred treatment for all types of OMD but is most effective in the jaw closure subtype. ² Tongue injections are contraindicated due to the risk of aspiration and supplementary oral medications are preferred for associated lingual dystonias.

Meige syndrome is the combination of blepharospasm and OMD. Presentation can be varied. It is possible for a patient to progress from a simple blepharospasm to Meige syndrome as their disease process progresses. All patients diagnosed with Meige syndrome have the presence of some component of blepharospasm and OMD. Botulinum toxin is the treatment of choice and the treatment is tailored to their symptomatology. Oral medications can help in synergy with localized botulinum toxin injections. For those patients who have medically intractable Meige syndrome, deep brain stimulation has shown efficacy in the treatment of primary Meige syndrome. In particular, deep brain stimulation to the subthalamic nucleus has improved the dystonia movement subscores from 19.3 to 5.5 and disability score from 15.6 to 6.1. ¹² With these various treatments identified, Meige syndrome has several options for effective treatment.

Cervical dystonia, also known as spasmodic torticollis, is a focal dystonia that affects the neck and shoulders. These dystonic movements cause postural abnormalities and discomfort and can be tonic, clonic, or tonic–clonic in nature. Similar to OMD, sensory tricks can be used to relieve some of the symptoms temporarily. Physical therapy can be helpful but may not be fully effective in the treatment of these dystonic movements. Treatments include anticholinergic medications, and botulinum toxin injections to the affected musculature. Use of physical therapy and botulinum toxin in combination can also provide effective treatment for cervical dystonia. ^{13 ,​ 14}

Focal dystonias exist beyond blepharospasm, OMD, and cervical dystonia. Although the majority of dystonias affecting the lower face affect the jaw as well (OMD), one can have local focal dystonia of solely the lower face or a localized region of the lower face. These focal dystonias are typically treated with local injection of botulinum toxin to the affected area every 3 to 4 months as needed. ¹⁰ Oral medications are used if the local injections are not fully effective. If the disease continues to progress, the dystonia may spread beyond its initial site, leading to a diagnosis of OMD, Meige syndrome, or even more generalized dystonias. Treatments for progressive focal dystonias are similar to those used in OMD, Meige syndrome, or generalized dystonias. ¹⁵

Other facial manifestations of muscle contractions exist and may mimic the symptoms of a focal dystonia. Craniofacial tremor, which occurs in association with essential tremor; Parkinson disease; and electrolyte imbalances ¹⁶ are in fact focal motor seizures. The facial manifestations are typically postictal with noted weakness of the face: most often the lower face. These are typically treated by helping to treat the underlying cause of the tremor or focal motor seizure.

Facial chorea, a non-patterned movement disorder, occurs in the context of a more systemic movement disorder. Once the most systemic movement disorder is identified, the chorea can be treated in the context of the systemic movement disorder. Facial tics, on the other hand, are repetitive, partially purposeful, succinct movements of the face. Medications, physiological changes, and encephalopathy are typical causes of tic disorders and treatment of the underlying cause improves the tic disorder. Facial myokymia also presents with repetitive, succinct movements but usually begins at the vermillion border and spreads in a wave-like pattern. Myokymia is typically idiopathic and resolves over weeks to months without any further treatment.