How to Diagnose and Treat Oral Motor Disorders

Man grabs his jaw in pain while hiking outside

1. Trismus

Trismus occurs when there is an involuntary restriction of active opening (<38mm) due to abnormal or inappropriate closer muscle activity during opening movement.  This is called a co-contraction disorder; openers and jaw closers are contracting at the same time.

If the co-contraction is not too severe, it is possible to override the jaw closers by performing an assisted jaw opening procedure.  Apply slight stretching force (about 1 kg of pressure) to the teeth as a patient attempts to open.  If successful, a normal opening (>45mm) should result after passive stretching of the jaw muscles.

If the trismus is severe, the patient will not usually allow strong stretching forces to be applied to the teeth due to pain.  This is described as a passive stretch with a soft end feel.  Other terms used to describe trismus are involuntary bracing, muscle splinting, and protective guarding.  The mechanism of trismus is typically a normal protective reflex response to the presence of pain induced by movement.

Evidence Needed to Diagnose Trismus

  1. A reduced active or unassisted opening (<30mm)
  2. Passive opening, or assisted opening, increases more than 10 mm (>40mm)

Related Reading: Commonly Used Medications For Temporomandibular Disorders

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2. Spasm

A spasm is a continuous involuntary contraction of a muscle, even at rest.  Like trismus, the mechanism of this condition is often a normal protective reflex response to the presence of regional pain. Occasionally, trismus and spasm responses can also occur as a result of brain damage.

Evidence Needed to Diagnose Spasms

  1. A continuous involuntary contraction of a muscle
  2. On palpation, the muscle is firm due to the contraction

3. Extrapyramidal Reaction to Drugs

A drug-related extrapyramidal reaction can occur when a medication is present that causes a motor activation reaction such as amphetamines or SSRIs.  Fluoxitine or Paroxetine are two examples that can induce the atypical reaction in the motor neurons of the brain.  This type of reaction will disappear when the drug is withdrawn.

The clinical history and examination evidence needed for this diagnosis includes a patient that is taking one of the known motor hyperactivity inducing drugs (e.g., SSRIs, amphetamines, or ADHD and diet medications)

4. Orofacial Dyskinesia

Dyskinesia indicates abnormal movement and describes a continuous repetitive movement disorder of the jaw, lips, or tongue.  Tardive dyskinesia can be drug-induced while spontaneous dyskinesia occurs without clear cause.  Unfortunately, there is not a specific diagnostic test for dyskinesia other than clinical observation and history of a repeated stereotypic motion of the tongue, lips or jaw.

5. Orofacial Dystonia

Orofacial dystonia is a specific movement disorder present when an intermittent involuntary sustained contraction of the jaw or orofacial muscles occurs.  Depending on the muscle involved, these contractions produce opening or lateral pulling of the jaw, also known as lateral pterygoid involvement.  These movements typically disappear during sleep and can only be briefly suppressed while the patient is conscious.  Another term used to describe mandibular dystonia is Meige’s syndrome.

The evidence needed to diagnose orofacial dystonia includes involuntary, intermittent sustained contraction of jaw, facial, or tongue muscles.

Related Reading

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6. Tremor

Tremor of the orofacial structures, usually in the jaw or tongue, is defined as a visually evident, sustained, rapid involuntary oscillatory movement.  This tremor can be further described as occurring with rest or only with movement.  There are numerous pathologic neurologic diseases, and even non-pathologic muscle fatigue, that cause orofacial tremors.

The evidence needed to diagnose tremors includes relatively rapid repeating or oscillating motion of the jaw, tongue, lips, or facial muscles

7. Bruxism

Bruxism is sleep associated with a series of rhythmic, brief, strong contractions of the jaw muscles occurring either in a centric occlusion position or associated with eccentric lateral jaw movements.

Bruxism can lead to abnormal wear of the teeth, periodontal tissue damage, or jaw pain.  Bruxism rarely occurs while awake, except in brain-damaged patients (e.g., cerebral palsy and traumatic brain injury).

Evidence Needed to Diagnose Bruxism

  1. Grinding of teeth while asleep, indicated by occlusal wear patterns on the teeth
  2. Grinding of teeth while asleep, indicated by grinding sounds
  3. Exhibiting disk derangement symptoms (e.g., clicking and locking)

8. Clenching

Clenching is presumably a learned behavior and can occur both awake and asleep.  The magnitude of force generated during clenching is much lower than bruxism with estimates being between 5%-10% of maximum voluntary contraction.  Clenching behaviors can last for seconds up to 10 minutes.  Estimates suggest the behavior can occur about 20% of the time throughout the day.

Evidence Needed to Diagnose Clenching

  1. Myalgia with bilateral soreness in the jaw closers
  2. Capsulitis (bilateral)
  3. Awareness by the patient that they clench their teeth

9. Orofacial Motor Tics

Motor tics of the orofacial region are characterized as involuntary brief, but repetitive, twitches of the orobuccal (many times in the buccinator) muscles.  These events are not suppressed for long periods of time and fortunately are not highly noticeable, unless associated with a noise such as a sucking or grunting.  Many times the tics involve the facial muscles (7th nerve), but can also affect the trigeminal motor system.

There is no consensus among experts concerning the origin or nature of these events.  Facial motor tics are often seen in patients without any other motor disturbance.  Evidence needed to diagnose orofacial motor tics are repeated twitching of the facial muscles.

Additional Articles on Oral Motor Disorders

Additional Articles on Diagnosing & Treating Oral Motor Disorders

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