gms | German Medical Science

Introduction: The question is, whether an EMG recording of the M. vocalis (TA) is sufficient to rule out substantial recurrent laryngeal nerve damage.

Method: In 69 of 177 transcutaneous laryngeal EMG studies during the last four years in our department an additional recording of the M. cricoarytaenoideus posterior (PCA) was done. After local anaesthesia of skin and subglottic mucous membranes the needle was passed on a straight way through cricothyroid membrane, subglottic space and cricoid lamina into the PCA. Density of interference pattern of TA and PCA were compared. The work up included a comprehensive medical history and a laryngostroboscopy.

Results: In 29 cases (46%) the density of interference pattern was more rarified in the PCA than in the TA indicating a higher grade of damage in nerve fibres supplying the PCA compared to those supplying the TA. In 26 cases (41.3 %) the grade of damage was the same in both muscles. Only in 8 cases (12.7%) the grade of damage was higher in the TA muscle. In laryngoscopy we had the impression that damage of the PCA had some correlation with the inclination of the arytenoid cartilage.

Conclusions: Transcutaneous-transcricoidal PCA-EMG recording is feasible in many cases during routine laryngeal EMG examination. It helps to confirm diagnosis especially in patients with vocal fold immobility and near-normal TA-EMG pattern.