Dados do Trabalho

Título

MOTOR UNIT NUMBER ESTIMATION IN PATIENTS WITH SPINAL MUSCULAR ATROPHY USING THE CMAP SCAN TECHNIQUE

Introdução

5q-Spinal Muscular Atrophy (SMA) is one of the most prevalent neuromuscular diseases in our country, and still an important cause of lethality, due to genetic disease, in its most severe forms. From a genetic point of view, it is already known that the number of copies of the SMN2 gene drastically influences the phenotype in an inverse relationship with the severity of the disease. Several studies show the reduction of motor unit counts by different techniques. A new Motor Unit Number Estimation (MUNE) technique described in 2016 by Bostock, MScanfit (CMAP Scan MUNE), uses a mathematical model that considers the stimulus-response curve of the compound muscle action potential (CMAP) to estimate the number of motor units. Studies have shown that this technique has greater sensitivity than other conventional techniques (MUNIX and MPS), in addition to not requiring voluntary activation, facilitating its use in children or patients with marked weakness.

Objetivo

The present study aims to evaluate the usefulness of Mscanfit in patients with SMA at the Hospital das Clinicas-FMUSP neuromuscular diseases outpatient clinic compared to other techniques (MUNIX and CMAP amplitude).

Métodos

Forty-seven patients with SMA were evaluated, CMAP scan values were obtained with surface electrodes on the abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles. MUNIX values were obtained in the same muscles, for comparison, of 40 collaborative patients for the technique. In 8 patients, the same exams were performed with one year of follow-up.

Resultados

Seven patients were SMA type 1, 25 patients were SMA type 2 and 15 were SMA type 3. Mean CMAP scan MUNE values correlated inversely with disease severity, with patients with SMA type 1 having lower values while those with patients with type 3 SMA have higher MUNE values. Among the patients who were controlled at 1 year of follow-up, only 1 patient was SMA type 1, being treated with nusinersen, and the MUNE values obtained by the CMAP scan were the same after 1 year of follow-up. The remaining seven patients who underwent the technique were SMA type 2 or 3 and the values did not differ significantly between the two exams in relation to the use or not of disease-modifying therapy.

Conclusões

CMAP Scan can be used to count motor units in patients with spinal muscular atrophy. More ongoing studies should assess its usefulness as a biomarker of disease progression and treatment response parameter.

Palavras chave

Spinal Muscular Atrophy, Motor Unit Number Estimation (MUNE), CMAP scan, Motor Unit Index (MUNIX)

Declaração de conflito de interesses de TODOS os autores

RHM and EZ have received financial support from Biogen for medical meetings and clinical trials.