Dystonia

INDEX

Oromandibular dystonia (OMD) refers to repetitive movements and sustained abnormal postures of the lower face, the muscles of mastication and the muscles of the tongue. Morning benefit (milder symptoms during morning) and overflow phenomena (aberrant muscle activation during certain tasks) are also relatively common in oromandibular dystonia.  The dystonia may be triggered by activities such as talking, yawning, chewing, or swallowing, often causing severe social impairment, reduced quality of life, and weight loss.

Spasm in OMD may be elicited or worsened by glaring lights, watching television, driving, reading, speaking, fatigue, and chewing.
Orofacial/oromandibular dystonia may be task specific with symptoms elicited, for example, by speaking, biting into food, auctioneer speech, singing but not speaking, prayer, and when speaking one language but not another.
Secondary disability from OMD includes dysarthria, dysphagia, difficulty breathing, temporomandibular joint dysfunction, weight loss, pain, and bruxism.
When severe, the lips, oral mucosa, or tongue become mutilated; teeth and dental devices may be damaged.
Sensory tricks can ameliorate OMD temporarily. Common sensory tricks include light touches to the face, chewing gum, or biting on a toothpick. Sensory tricks may be more effective in those with jaw-opening rather than jaw-closing dystonia, and even those without a known sensory trick may improve when a stick is placed in their mouth.

There are a number of different subtypes:

  1. Jaw-Opening dystonia
  2. Jaw-closing dystonia
  3. Jaw-Deviating oromandibular dystonia
  4. Perioral dystonias
  5. Lingual Oromandibular dystonia
  6. Meige syndrome: oromandibular dystonia associated with blepharospasm

Aetiology

  1. Medications: acute oromandibular dystonia is a common form of an acute dystonic reaction.  50% of cases occur during the first 24 hours and 90% of cases in the first five days. Orofacial dyskinesias are a common manifestation of tardive dyskinesia, noting that the movements of neuroleptic-induced tardive OMD may be more stereotyped than those of idiopathic OMD.
  2. Peripheral oral factors likely play an important role, including edentulousness, poorly fitting dentures and oral pain.  In addition, a number of outpatient dental procedures or other causative or predispose a patient to the development of oromandibular dystonia.
  3. Neurodegenerative
    - PD
    - MSA
    - PSP
    - HD
  4. Genetic forms of dystonia:

DYT-THAP1  Prominent craniocervical dystonia

DYT-TUBB4  Prominent craniocervical dystonia with prominent spasmodic dysphonia

DYT-GNAL  Predominantly craniocervical form of dystonia

DYT-ATP1A3(RAPID-ONSET DYSTONIA PARKINSONISM)  Rostro-caudal gradient with a strong involvement of the bulbar region, sometimes with laryngeal involvement

- Lesch-Nyhan syndrome
- Wilson's disease
- Neuroacanthocytosis
- Pantothenate kinase-associated neurodegeneration

 

Treatment

Oral medications used for OMD include anticholinergic drugs, dopamine depleters, benzodiazepines, dopamine agonists, anticonvulsants, baclofen, lithium, and gabapentin. OMD typically responds poorly to oral medications, and botulinum toxin is the treatment of choice.  Oromandibular dystonia encompasses a broader range of musculature than blepharospasm, and is more difficult to treat. In contrast to blepharospasm, which has a response rate of over 90%, about two-thirds of patients with OMD have at least moderate improvement with BoNT.
Jaw-closing may be more responsive than jaw-opening dystonia.
Musician embouchure dystonia is rarely helped.
The benefit for OMD typically lasts 3 to 6 months and can be sustained for years without loss of efficacy or the emergence of serious adverse effects.

Muscle Selection

Patients should be examined as follows, and the predominant direction of movement and limitations in range of motion noted.
For OMD, it is often neither possible nor necessary to inject every muscle with excessive movement, and substantial benefit can often be achieved by injection limited to the most affected muscles.

  1. At rest with the eyes open and eyes closed.
  2. The effects of speaking, chewing, and any exacerbating or alleviating activities should be determined.
  3. The tongue should be observed at rest on the floor of the mouth as well as on extension and with speech.

    Note that injections may be needed into orbicularis oculi for accompanying blepharospasm, neck muscles for concomitant cervical dystonia, and tongue muscles for lingual involvement.


Adverse Effects
Adverse effects, especially weakness of injected or nearby muscles, complicate injection in about one-third of patients.
Weakness can cause or worsen pre-existing dysarthria and dysphagia.
Tongue injections may be especially likely to cause or worsen dysphagia, making lingual dystonia particularly difficult to treat.
 

 

 

 

 

 

 

 

 

 

 

 

 

References