Dystonia

INDEX

 

Abnormal lingual muscle contraction may be classified into four subtypes:

  1. Protrusion
  2. Retraction
  3. Curling: presents as upward curling contraction of the tongue, which may be task-specific.
  4. Laterotrusion: presents as lateral deviation of the tongue1
     

Patients with the protrusion type of lingual dystonia may also have laterotrusion or curling.

Treatment

Treatment is with botulinum toxin; typically this is for tongue protrusion in which case the posterior fibres of genioglossus require injection.

The muscles of this region include those of the submental complex: geniohyoid, mylohyoid, digastric anterior belly:

Figure 1. Submental complex

 

Injection begins by identifying the hyoid bone.  This forms the inferior margin of the submental triangle; the lateral border is made up of the anterior belly of the digastric muscle.  The digastric muscle is activated by opening mouth slightly.

The insertion points are two sites 25–30 mm posterior from the midline of the body of the mandible and 15–20 mm apart from each other (Figure X).

Figure 2. Injection sites

The needle is placed with EMG guidance through the digastric and mylohyoid muscles, and then into the genioglossus muscle at a depth of approximately 2cm2.  The patient should close the mouth lightly and push the tongue against the back of the teeth, which will activate the muscle, which can be easily felt.

Figure 3. Needle passing through anterior body of the digastric muscle

Figure 4. Muscles through which needle passes in order to reach genioglossus muscle

Dose for lingual injections.

Use a low dose, high concentration of toxin; 10-12.5 per side.
The therapeutic window is narrow and therefore it is recommended to commence with a starting dose of 5 units in each genioglossus muscle.  This may be increased by 2.5 units in each successive treatment until the patients achieves a reasonable response.

 

 

 

 

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References

1            Yoshida K. Botulinum neurotoxin therapy for lingual dystonia using an individualized injection method based on clinical features. Toxins (Basel) 2019; 11: 1–18.

2            Odell K, Sinha U. Dystonia of the Oromandibular, Lingual and Laryngeal Areas. In: Rosale, ed. Dystonia - The Many Facets. 2012. DOI:10.5772/28356.