“EMG” stands for “electromyography”. It is a test performed to study muscle activities under various conditions. Laryngeal EMG studies activities of muscles in the larynx. There are mainly four pairs of small muscles in the larynx that control the position and movement of vocal cords. Three pairs of these muscles serve to bring vocal cords together and one pair to bring them apart. Although not completely understood, SD (spasmodic dysphonia) is now known to be caused by abnormal activities of laryngeal muscles that interfere with vocal cord movement, leading to voice difficulties. Botox inhibits such abnormal muscle activities and “smoothes” out the voice. For Botox treatment to be successful, the medicine has to be placed in the muscles that bear abnormal activities, at an appropriate dose. Not all laryngeal muscles are equally active in SD. Although the doctor may often have a good guess of which muscles are most active in causing vocal cord movement problems in SD, muscle activities in the larynx can be complex and change over time. It has been observed in the clinic that some patients do not benefit from Botox treatment like other patients and some patients lose their treatment benefits after a period of success. While a number of factors need to be considered when Botox treatment is not completely satisfactory, one important consideration is to verify if the medicine has been placed in the muscles that are actually causing problems. Laryngeal EMG is helpful for this purpose as it can reveal activities in individual muscles during various laryngeal functions including speaking. Examining these activities helps identify culprit muscles and provide guidance in designing Botox treatment. Laryngeal EMG study has helped several patients regain Botox treatment benefits in our clinic. Laryngeal EMG test usually takes a separate visit that can be arranged on the same day of Botox treatment. The larynx is usually numbed for the test and the patient takes a reclined position for comfort and relaxation. Recording is made through a fine needle electrode inserted into various muscles in the larynx through the skin. The patient is asked to perform several vocal functions while a computer-controlled machine records activities from laryngeal muscles. The test takes about half an hour to complete and the patient resumes normal activities right after the test, except refraining from eating and drinking for an hour due to anesthetic effects.

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