Template-operated MUP analysis is not accurate in the diagnosis of myopathic or neuropathic changes in the diaphragm

Abstract

The aim of this study was to evaluate the quantitative motor unit potential (MUP) analysis in the diagnosis of myopathy and neuropathy of the diaphragm. Diaphragm template-operated quantitative EMG were performed in 30 patients with myotonic dystrophy type 1 (DM1), 17 with myotonic dystrophy type 2 (DM2) and 40 with amyotrophic lateral sclerosis (ALS). Low MUP amplitude precluded MUP analysis in 21% of DM1 patients. Only a single DM1 patient had EMG findings consistent with myopathy. In this patient, and another 4 DM1 and 3 DM2 patients, findings were consistent with neuropathy. Neuropathic MUP changes were found in 92% of ALS patients, but due to motor neuron cell loss in only 60% MUPs analyses could be done. Phrenic nerve conduction studies correlated with respiratory function tests, whereas MUP parameters did not. Quantitative MUP analysis was not able to adequately sample diaphragm MUPs in patients with chronic myopathy or motor neuronopathy.