MS is a focal dystonia affecting principally eye and lower facial musculature. In general, rhythmic, spastic and tremor-like movements may be observed.

Most patients present with intermittent blepharospasm. It is not uncommon to hear that any minor accident or pathological condition, e.g., eye irritation due to dust exposure, keratoconjunctivitis sicca, conjunctivitis or blepharitis, acted as initial triggers of blepharospasm. Rapid, forced blinking may precede the latter. Here, blink frequency and muscle tone exceed those observed in healthy individuals trying to eliminate a small foreign body from their eyes.

Similarly, a patient may report trauma to have caused oromandibular dystonia. Such trauma may consist in blunt facial trauma sustained during sports accidents, falls or even dental treatment. Dystonia of lower facial musculature usually manifests after blepharospasm, i.e., the disease tends to spread. However, spread of dystonia from lower facial or neck regions to the eye is less likely [8]. Movement disorders may comprise masticatory, lingual, pharyngeal as well as laryngeal muscles [9]. In this line, patients may present with involuntary masticatory movements, clench their jaws, thrust their mandibles forward, purse their lips or grimace.

In some cases, dystonia may spread further and affect neck muscles. Spread may occur even years after symptom onset. Although trauma may account for disease progress, it is not always possibly to identify its cause.

• Movement Disorder

  The objective of this chapter is to depict the history of segmental craniocervical dystonia in order to delineate the phenotypic spectrum of the disorders and to distinguish this entity from other facial and/or oromandibular movement disorders. © 2018 [ncbi.nlm.nih.gov]

  The objective of this chapter is to depict the history of segmental craniocervical dystonia in order to delineate the phenotypic spectrum of the disorders and to distinguish this entity from other facial and/or oromandibular movement disorders. [unboundmedicine.com]

  Movement disorders in neurology concern involuntary movements of parts of the body. Many movement disorders are caused by nerve diseases such as Parkinson’s disease. [books.google.de]

• Pain

  Nine of 10 patients found lidocaine tape to be more effective than placebo tape in reducing pain during injection. CONCLUSIONS: Lidocaine tape is a simple and convenient method of reducing pain during botulinum toxin injection. [ncbi.nlm.nih.gov]

  At his first visit to our pain center, he could not walk without crutches because of severe pain accompanied by symptoms such as allodynia, decreased skin temperature, redness, edema, muscle weakness, and changes in the appearance of the affected area [pesquisa.bvsalud.org]

  These contractions can be forceful and often painful. In addition, muscles around the eyes spasm, called blepharospasm. [my.clevelandclinic.org]

• Disability

  We followed 5 patients with disabling Meige syndrome treated by bilateral GPi-DBS for 49 ± 43.7 (mean ± SD) months. [ncbi.nlm.nih.gov]

  Journal of Intellectual Disability Research. 2008;52(2):141-155 9. Fletcher R, Loschen E, Stavrakaki C, et al., editors. Diagnostic Manual-Intellectual Disability: A Textbook of Diagnosis of Mental Disorders in Persons with Intellectual Disability. [intechopen.com]

  It is a disabling spasm of the facial musculature consisting of primary blepharospasm followed by abnormal facial movement. Squinting may begin unilaterally but soon becomes bilateral. [whonamedit.com]

• Fatigue

  Fatigue was measured by a visual analogue scale (VAS) and the Fatigue Assessment Inventory (FAI). [tandfonline.com]

  Blepharospasm, or forced or frequent blinking or twitching, sometimes happens in response to bright lights, fatigue, wind or air pollution, or tension. Blepharospasm may first affect only one eye, but will affect both eventually. [my.clevelandclinic.org]

  The patient (Fig 1) complained of difficulty in opening his eyes especially when driving or using a video display terminal (VDT), and suffered from ocular fatigue, irritation, and occasional injection. [bjo.bmj.com]

  In the early stages it may only occur with specific precipitating stressors such as bright lights, fatigue, and emotional tension. It is almost always present in both eyes. As the condition progresses, symptoms may occur frequently during the day. [dystoniacanada.org]

  The spasms disappear during sleep and may be made worse with bright lights, fatigue, or emotional stress. Hemifacial spasm is the uncontrolled contraction of muscles on one side of the face, usually including the eyelids. [rogerkohnmd.com]

• Trisomy 21

  DS is a chromosomal anomaly characterized by trisomy 21. Overlapping or co-occurrence of DS and ASD mechanisms is uncertain. [intechopen.com]

• Jaw Pain

  Two months after switching from risperidone to paliperidone, his eye blinking, light sensitivity, jaw pain, and trismus gradually improved, although the dysarthria persisted. [ncbi.nlm.nih.gov]

  Due to such findings, OMD may cause jaw pain as well as difficulties eating and speaking (dysarthria). In addition, in some patients, the dystonic spasms may sometimes be provoked by certain activities, such as talking, chewing, or biting. [web.archive.org]

  Other symptoms related to the jaw can be: Facial grimacing Frowning Thrusting of the chin Displaced jaw Pain in the jaw Headaches Spasms can also occur in the tongue, throat, and respiratory tract. [my.clevelandclinic.org]

  […] deviation or protrusion of the tongue. jaw pain difficulties eating and drinking difficulties speaking (dysarthria)Blepharospasm symptoms the first symptom to appear is an increased rate of blinking uncontrollable squinting/closing of eyes light sensitivity [en.wikipedia.org]

  […] opening sideways deviation or protrusion of the jaw lip tightening and pursing drawing back (retraction) of the corners of the mouth deviation or protrusion of the tongue. jaw pain difficulties eating and drinking difficulties speaking (dysarthria). [psychology.wikia.com]

• Trismus

  Two months after switching from risperidone to paliperidone, his eye blinking, light sensitivity, jaw pain, and trismus gradually improved, although the dysarthria persisted. [ncbi.nlm.nih.gov]

  Associated findings of OMD may include spasms of jaw closure with difficulty opening the mouth (trismus) and clenching or grinding of the teeth (bruxism); spasms of jaw opening; or sideways deviation or protrusion of the jaw. [web.archive.org]

  Oromandibular Symptoms difficulty opening the mouth (trismus) clenching or grinding of the teeth (bruxism) spasms of jaw opening sideways deviation or protrusion of the jaw lip tightening and pursing drawing back (retraction) of the corners of the mouth [en.wikipedia.org]

  The combination of upper and lower dystonia is sometimes called cranial-cervical dystonia. [2] The incidence is about one case in 20,000 people. [3] Symptoms Edit Oromandibular Symptoms difficulty opening the mouth (trismus) clenching or grinding of the [psychology.wikia.com]

• Blepharospasm

  One of the earliest suspected documentations of blepharospasm is a painting - De Gaper - by the Flemish artist Brueghel (1525-1569), who painted a woman with apparent blepharospasm with facial and neck involvement. [whonamedit.com]

  We can say that botulinum toxin therapy was good or very good in 14 (77.7{\%}) patients with blepharospasm and Meige's Syndrome. [udesantiago.pure.elsevier.com]

  Oromandibular Dystonia Syndrome, Idiopathic Blepharospasm-Oromandibular Dyskinesia Blepharospasm-Oromandibular Dyskinesias Blepharospasm-Oromandibular Dystonia Blepharospasm-Oromandibular Dystonia Syndrome Blepharospasm-Oromandibular Dystonia Syndrome [finto.fi]

  Blepharospasm was associated with involuntary contractions of the jaw muscles in only one of these patients. [blepharospasm.org]

  Sixty patients had idiopathic blepharospasm, 31 patients were diagnosed with Meige syndrome (blepharospasm plus oromandibular dystonia) and nine patients with segmental dystonia (Meige syndrome plus cervical dystonia). [ncbi.nlm.nih.gov]

• Muscle Spasm

  Years later, she presented to the emergency department in intermittent respiratory distress associated with facial and cervical muscle spasms. Increasing frequency and severity of the disorder was noted over years. [ncbi.nlm.nih.gov]

  Définition: A syndrome characterized by orofacial DYSTONIA; including BLEPHAROSPASM; forceful jaw opening; lip retraction; platysma muscle spasm; and tongue protrusion. [hon.ch]

  […] of the jaw and tongue (oromandibular dystonia) and involuntary muscle spasms and contractions of the muscles around the eyes (blepharospasm). [rarediseases.org]

  Treatment Muscle spasms are remedied by injecting botulinum toxin ("Botox") into affected muscles. This is considered a safe procedure that often provides relieve for several months. [symptoma.com]

• Myopathy

  Zebrafish Model for Dravet Syndrome Scott Baraban PhD, University of California, San Francisco Application of Genetics in Drug Discovery and Development Aris Baras MD MBA, Regeneron Identifying Genetic and Chemical Modifiers: Lessons from Congenital Myopathies [event.roseliassociates.com]

• Suggestibility

  In a patient with Brueghel syndrome, paroxysmal hyperpnea coincided with dystonic gaping; the finding of upbeating nystagmus suggests pontine localization in the pathogenesis of this rare disorder. [ncbi.nlm.nih.gov]

• Fear

  Anxiety disorders Fear and anxiety are necessary to survive by resisting danger and threat. [intechopen.com]

• Facial Spasm

  History A 67-year-old black woman, who was admitted to the hospital for multiple systemic illnesses, presented to the eye clinic for a consult related to an unusual facial spasm that began 15 days earlier. [reviewofoptometry.com]

  Hemifacial spasm is believed to be caused by compression of the facial nerve. [klapperplasticsurgery.com]

  Eyelid spasms. Irritation of eyes. Midfacial or lower facial spasm. Brow spasm. Eyelid Tic (habitual spasmodic muscular contraction). Exact cause of benign essential blepharospasm is not known. [nhp.gov.in]

  The treatment unresponsive patients without Meige’s syndrome had a variety of conditions; one had hemifacial spasm, one facial spasm, and two depression. [bjo.bmj.com]

  A dystonia is a movement disorder that causes the muscles to contract and spasm involuntarily. The first record of blepharospasm and lower facial spasm was found in the 16th century in a painting titled De Gaper. [emedicine.medscape.com]

• Facial Grimacing

  Other symptoms related to the jaw can be: Facial grimacing Frowning Thrusting of the chin Displaced jaw Pain in the jaw Headaches Spasms can also occur in the tongue, throat, and respiratory tract. [my.clevelandclinic.org]

  Meige syndrome has to be treated actively with anticholinergic drugs if tolerated, clonazepam and Botulinum toxin injections into all the dystonic muscles of the face (eyes, jaw, tongue, larynx, neck) ; the facial grimaces can settle and patients with [infodystonia.com]

  When blepharospasm is part of Meige's syndrome, it is associated with facial grimacing. Reflex blepharospasm may be accompanied by photophobia and ocular signs of blepharitis and surface disease. [eyewiki.aao.org]

  Secondary blepharospasm: Meige’s syndrome: Meige’s syndrome may be associated with facial grimacing due to facial dystonia. Breughel’s syndrome: Breughel’s syndrome is a dystonia of motor trigeminal nerve which produces widely open mouth. [nhp.gov.in]

• Dystonia

  Similarly, masticatory dystonia may occur in isolation or in combination with dystonia of other cranial and cervical muscles. [ncbi.nlm.nih.gov]

  From Wikidata Jump to navigation Jump to search cranio-facial dystonia that is accompanied by blepharospasm Meige syndrome (disorder) Meige syndrome Meige dystonia edit English Meige syndrome cranio-facial dystonia that is accompanied by blepharospasm [wikidata.org]

  Clinical Features of Segmental Craniocervical Dystonia: Patients with blepharospasm may also have lower facial dystonia, masticatory (jaw muscles) dystonia, lingual (tongue) dystonia, pharyngeal (swallowing) dystonia, laryngeal (voice box) dystonia, or [blepharospasm.org]

• Irritability

  Differential diagnosis Eyelid myokymia Secondary to ocular irritation (ie dry eyes, blepharitis, entropion, intraocular inflammation, photosensitivity) Secondary to meningeal irritation (ie temporoparietal strokes) Tardive dyskinesia (secondary to neuroleptic [eyewiki.aao.org]

  When the facial nerve is irritated, it causes the facial muscles to involuntary contract and go into spasm. Fewer than 1% of cases are caused by tumor-induced facial nerve irritation. This may require and MRI to document this uncommon cause. [rogerkohnmd.com]

  Diagnosis The diagnosis is made on the basis of external signs, for example the presence of eye irritation, increased blinking frequency and spasms. [dystonia.org.uk]

  Reflex blepharospasm: Reflex blepharospasm may be secondary to irritation of ocular surface. [nhp.gov.in]

• Seizure

  There are chapters on epileptic seizures that do not look like typical epileptic seizures, and conversely, apparent epileptic seizures that are not. [books.google.de]

  People may become vulnerable to epileptic seizures through a wide variety of possible causes, including physical injury and exposure to chemical toxins. Some people with epilepsy have partial seizures, which are also known as focal seizures. [nap.edu]

  Clinical and electro-clinical classification of epileptic seizure in west Uganda. Bull Soc Pathol Exot. 2000; 93: 255-259 Newell E.D. Vyungimana F. Bradley J.E. [ijidonline.com]

  Focal seizures. Management should be under medical supervision. Currently, there is no cure for BEB and the disease frequently progresses despite treatment. [nhp.gov.in]

  Artane (anti-cholinergic), Klonopin (gabanergic muscle relaxant), and Keppra (anti-seizure) have been shown to help some essential blepharospasm and/or Meige patient. [klapperplasticsurgery.com]

• Neurologic Manifestation

  According to clinical characteristics of dystonia, dystonia is classified by age at onset, body distribution, temporal pattern, the coexistence of other movement disorders, and other neurological manifestations (3). [frontiersin.org]

• Tic Disorder

  Other disorders that can give rise to unilateral facial spasms include facial myokymia, tic disorders, focal seizures, demyelinating disorders, tetanus and, rarely, hysterical conversion reaction. [5,6] Table 1 - Disorders considered in the differential [blepharospasm.ca]

Diagnosis of MS is based on clinical examination and exclusion of secondary dystonias [9]. Laboratory analyses of blood samples, diagnostic imaging and possibly genetic screens may be applied to rule out the following differential diagnoses:

• Ischemic stroke
• Parkinson's disease
• Huntington's disease
• Neoplasms of the central nervous system
• Multiple sclerosis
• Systemic lupus erythematosus
• Intoxication

In MS patients, the aforementioned analyses and screens are normal.

MS is generally treated with injection of botulinum toxin. Such treatment is merely symptomatic and aids to resolve muscle spasms. In order to mediate that effect, botulinum toxin has to be injected into the affected muscles. Doses ranging from 5 to 25 units have been recommended for distinct muscles [10]. Decreased muscle tones are usually noted within three days after the injection and persist for several months. Effect duration varies from patient to patient - most patients are fine with four injections per year. Injection of botulinum toxin is considered a safe procedure that is rarely associated with adverse events [11].

A variety of other drugs has been applied to relieve MS-associated symptoms. However, only limited success was reported for antiepileptics, muscle relaxants, anticholinergics, benzodiazepines and related drugs as well as tetrabenazine [9]. These drugs may pose alternative treatment options if botulinum toxin injections yield only unsatisfactory results. However, possible benefits have to be considered against side effects of those medications. High risks of side effects are associated with anticholinergic therapy.

As has been indicated above, deep brain stimulation of the internal globus pallidum has been gaining importance as a therapeutic approach to otherwise intractable MS. Although many patients worry about the risks of brain surgery, stereotactic placement of electrodes is safe and bears only low risks of stroke, infection or neurological sequelae.

Prognosis is favorable. Patients who don't respond to medication may benefit from deep brain stimulation of the internal globus pallidum. According to a recent study regarding long-term treatment response to this technique, most patients experience considerably improvement, i.e., severity of blepharospasm and oromandibular dystonia significantly decreases [6]. If cervical dystonia is present, the likelihood of improvement for this particular symptom is lower. Spontaneous remission has been reported [7].

To date, MS is considered a primary dystonia, i.e., there is no underlying disease triggering disturbance of muscle tone in patients suffering from MS. In contrast, secondary dystonia may be observed in individuals suffering from Parkinson's disease or Huntington's disease or in those who sustained a trauma. Indeed, patients treated for Parkinson's disease are not unlikely to develop MS since antiparkinson drugs may trigger this facial dystonia by modulating dopamine receptors. Interaction with gamma-aminobutyric acid (GABA), serotonine and adrenergic receptors has also been proposed to contribute to MS. All these effects may be mediated by distinct psychotropic drugs [3]. However, drug-induced MS is a rare side effect of such medication and additional factors either predispose certain patients for dystonia or trigger the disease while treated for other pathological conditions. Such additional factors are most likely genetic disorders or environmental influences. Nevertheless, most MS cases are deemed idiopathic.

Functional impairment of basal ganglia and possibly additional brain regions like the brain stem are assumed to account for facial dystonia, but little more is known about their causes.

The annual incidence of focal dystonia has been estimated to be about 12 per 100,000 people [4]. With regards to that same study, one out of three patients presenting with focal dystonia suffered from blepharospasm. Due to inconsistent use of distinct designations, e.g. facial dystonia, orofacial dystonia, and craniocervical dystonia, multimorbidity and considerable overlap of symptoms, precise epidemiological data regarding MS cannot be provided here.

Regarding MS prevalence, there is a broad age peak between 30 and 70 years. Nevertheless, MS has been diagnosed in younger and older patients. Women are affected about twice as often as men, a phenomenon that can't currently be explained.

Functional impairment of basal ganglia is assumed to cause MS-associated symptoms. Basal ganglia is a rather general term that refers to a number of nuclei located at the base of the forebrain. They comprise brain regions like ventral and dorsal striatum, globus pallidum and substantia nigra, and form part of a complex neuronal network. Basal ganglia are connected to cortex and thalamus and are involved in regulatory circuits that account for a variety of motor, cognitive and limbic functions. In this context, regular, involuntary blinking may be dependent on basal ganglia function and disturbance of impulse generator or regulator, particularly abnormal excitation, may result in blepharospasm. However, further research is needed to shed more light on basal ganglia function - their involvement in determined movements is often based on little more than speculation.

However, both data regarding etiology as well as therapy of MS argue for the hypothesis of a basal ganglia-mediated disorder. As has been mentioned above, antiparkinson drugs have been reported to induce MS. Symptoms associated with Parkinson's disease are essentially caused by a shortage of dopamine and relative excess of acetylcholine. The former, in turn, results from neuronal cell death occurring in the substantia nigra. Antiparkinson drugs either aim at compensation for lack of dopamine, stimulation of dopamine receptors, reduction of dopamine degradation or decrease of acetylcholine effects. They mimic actions otherwise executed by the substantia nigra, i.e, by an anatomic structure forming part of the basal ganglia.

Another structure assumed to play a major role in control of subconscious and voluntary movements is the globus pallidum which is, as has been mentioned above, also part of the basal ganglia. Deep brain stimulation of the internal globus pallidum has been reported to relieve symptoms of movement disorders like dystonia [5]. This technique basically consists in stereotactic insertion of electrodes in very close proximity to the internal globus pallidum and continuous stimulation of local neurons. This may eventually result in excitation or inhibition of those cells. The precise mechanisms underlying deep brain stimulation effects are not yet fully understood, but the fact that modulation of neuronal signalling in this anatomical structure improves MS-associated symptoms strongly implies a role of the globus pallidum in MS pathogenesis.

No preventive measures can be recommended at this time.

Meige syndrome (MS) pertains to a group of disorders referred to as focal dystonias. It is named in honor of the French neurologist Henri Meige who is generally ascribed the first description of the disease. He published his observations in 1910 [1]. Its most characteristic symptoms are blepharospasm and oromandibular dystonia which manifest as repeated, forced blinking or the inability to open the affected eye and involuntary movements of lips, tongue, masticatory and mimic musculature, respectively. Basically any muscle contributing to lower face or neck movements may be affected. Contrary to generalized forms of dystonia, neither limbs nor trunk are involved.

MS is usually diagnosed in middle-aged persons and more often in females. Its etiology is largely unknown; some cases seem to be induced by administration of drugs. It is assumed that impairment of basal ganglia function accounts for the abovementioned symptoms. Patients often report certain environmental factors to trigger symptom onset, e.g., temperature, wind and light.

Due to knowledge gaps regarding causes and pathogenesis of MS, treatment can only be symptomatic except in cases of drug-induced pathology. Here, dose reduction may be sufficient to remedy the disease. Empiric evidence argues for injections of botulinum toxin as most effective measure to prevent muscle spasms. Muscle relaxants and anti-convulsants have been applied with less success. Deep brain stimulation of the internal globus pallidum may be an alternative therapeutic approach [2]. Additionally, those patients who identified individual environmental triggers may avoid those as much as possible.

Of note, idiopathic orofacial dystonia, idiopathic orofacial dyskinesis, craniocervical dystonia or similar designations all refer to MS.

Meige syndrome (MS) is a rare disease pertaining to the group of focal dystonia. The term dystonia refers to disturbances in muscle tone, while the attribute focal distinguishes these disorders from generalized ones that affect the whole body. As it is, MS is a facial dystonia and is therefore also called idiopathic orofacial dystonia. If neck muscle involvement is detected, physicians may talk about craniocervical dystonia.

Causes

Voluntary and subconscious movements of eye and lower facial musculature are controlled by complex neuronal circuits that involve brain regions like basal ganglia, cortex and thalamus. MS-associated symptoms are assumed to be triggered by functional impairment of basal ganglia. Overexcitation of basal ganglia neurons may result in alterations of muscle tone impulse generators and regulators and thus provoke dystonia.

Little is known about etiologic factors inducing this malfunction of basal ganglia. Most cases are deemed idiopathic, i.e., no specific cause can be identified. Some MS patients receive treatment for comorbidities like Parkinson's disease and psychological disorders. And although drugs prescribed to this end may provoke facial dystonia, such side effects are observed in a minority of patients. This fact implies that additional factors play a role in MS pathogenesis.

Symptoms

Rhythmic, spastic or tremor-like muscle contractions affecting eye, lower facial and possibly neck musculature. In detail, the following may be observed:

• Blepharospasm (eyelid spasm)
• Uncontrollable masticatory movements
• Jaw clenching
• Jaw thrusting
• Lip pursing
• Grimacing

Symptomatic episodes may be induced by air pollution, eye irritation, facial trauma or dental treatments. Some patients report certain postures, activities and environmental factors to exacerbate symptoms.

Diagnosis

MS is an exclusion diagnosis. Thus, workup mainly aims at ruling out other diseases that may trigger similar symptoms. Laboratory analyses of blood samples and diagnostic imaging are applied to this end. Stroke, Parkinson's disease, Huntington's disease, brain tumors and multiple sclerosis shall serve as examples.

Treatment

Muscle spasms are remedied by injecting botulinum toxin ("Botox") into affected muscles. This is considered a safe procedure that often provides relieve for several months. A variety of other drug therapies has been tested, but little success has been reported for administration of antiepileptics, muscle relaxants, anticholinergics, benzodiazepines and related drugs.

Otherwise intractable cases may be cured by means of deep brain stimulation of the internal globus pallidum. This procedure involves placement of electrodes in one of the basal ganglia involved in MS pathogenesis. Continuous excitation of local neurons yields significant improvement of symptoms. Contrary to general assumption, this minimally invasive brain surgery has not been related to major adverse events. It should seriously be considered if drug treatment does not provide sufficient relieve from facial dystonia.

1. Meige H. Les convulsions de la face. Ue forme clinique de convulsion faciale bilaterale et mediane. Rev Neurol. 1910; 21:437–43.
2. Bae DW, Son BC, Kim JS. Globus pallidus interna deep brain stimulation in a patient with medically intractable meige syndrome. J Mov Disord. 2014; 7(2):92-94.
3. Tsuji S, Kikkawa S, Horiguchi J, et al. Meige syndrome with apraxia of lid opening after the discontinuation of sulpiride treatment. Pharmacopsychiatry. 2002; 35(4):155-156.
4. Epidemiological Study of Dystonia in Europe (ESDE) Collaborative Group. A prevalence study of primary dystonia in eight European countries. J Neurol. 2000; 247(10):787-792.
5. Mehdorn HM. Deep brain stimulation for dystonia: review of the literature. J Neurosurg Sci. 2016; 60(2):199-210.
6. Reese R, Gruber D, Schoenecker T, et al. Long-term clinical outcome in meige syndrome treated with internal pallidum deep brain stimulation. Mov Disord. 2011; 26(4):691-698.
7. Castelbuono A, Miller NR. Spontaneous remission in patients with essential blepharospasm and Meige syndrome. Am J Ophthalmol. 1998; 126(3):432-435.
8. Weiss EM, Hershey T, Karimi M, et al. Relative risk of spread of symptoms among the focal onset primary dystonias. Mov Disord. 2006; 21(8):1175-1181.
9. LeDoux MS. Meige syndrome: what's in a name? Parkinsonism Relat Disord. 2009; 15(7):483-489.
10. Blitzer A, Binder WJ, Aviv JE, Keen MS, Brin MF. The management of hyperfunctional facial lines with botulinum toxin. A collaborative study of 210 injection sites in 162 patients. Arch Otolaryngol Head Neck Surg. 1997; 123(4):389-392.
11. Czyz CN, Burns JA, Petrie TP, Watkins JR, Cahill KV, Foster JA. Long-term botulinum toxin treatment of benign essential blepharospasm, hemifacial spasm, and Meige syndrome. Am J Ophthalmol. 2013; 156(1):173-177 e172.