• K Yoshida, R Kaji, A Takagi, and T Iizuka.
• Department of Oral and Maxillofacial Surgery, Graduate School of Medicine, Kyoto University, Japan.
• Oral Surg Oral Med O. 1999 Dec 1;88(6):664-9.

ObjectiveJaw-opening and jaw-deviation dystonias are characterized by mouth opening or lateral shift of the mandible due to involuntary contraction of the lateral pterygoid muscle, causing difficulties in speech or mastication. We introduce the method of muscle afferent block by using a removable device for inserting a hollow electromyographic needle.Study DesignA technique for fabricating a customized needle insertion guide into the lateral pterygoid muscle is described. Using the device, intramuscular injection of lidocaine and ethanol was performed in 3 patients with jaw-opening dystonia and 2 with jaw-deviation dystonia. Subjective improvement was assessed on a linear self-rating scale ranging from 0 (no improvement) to 100 points (complete cure).ResultsThe overall subjective improvement was 72% +/- 16.4% without major side effects.ConclusionsThe device is very useful for safe and accurate injection into the lateral pterygoid muscle. The muscle afferent block is effective for jaw-opening and jaw-deviation dystonias.

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