The diagnostic yield of the nerve-muscle skin biopsy in paediatric neurology practice. The Montreal Children's Hospital Neuromuscular Group.

Objective: To determine the diagnostic yield of the nerve-muscle-skin (NMS) biopsy in paediatric neurology practice.

Methods: A consecutive series of 98 paediatric NMS biopsies done 1989-1994 retrospectively reviewed in the context of pre-biopsy clinical and laboratory parameters. Bivariate associations based on chi-square test. Unconfounded associations between pre-biopsy variables and positive diagnostic yield (PDY) assessed by multiple logistic regression.

Results: Fifty seven out of 98 patients central (global delay, seizures, abnormal CNS imaging) process; 41/98 patients peripheral (motor delay, weakness) process, electromyography-nerve conduction studies (EMG-NCS) 87/98 cases; abnormal 43/87. Positive diagnostic yield (PDY) in 42/98 (43%) biopsies. Statistically significant bivariate associations between PDY and pre-biopsy; age, presenting symptom, developmental delay, weakness, reflexes, CPK, lactate, EMG-NCS and process. Unconfounded associations demonstrated with PDY and age, reflexes and process. The presence of a peripheral process or an abnormal EMG-NCS strongly predictive of PDY: 34/41 (83%) peripheral process cases had PDY, 32/40 (80%) abnormal EMG-NCS cases had PDY, and 29/31 (93.5%) peripheral process and abnormal EMG-NCS cases had PDY. Abnormal EMG-NCS with central process improved PDY to 3/9 (33%) from 4/37 (11%) for normal EMG-NCS.

Conclusions: NMS biopsy is a valuable diagnostic tool, particularly in the context of a suspected peripheral process or a central processes with an abnormal EMG-NCS.