To determine the utility of performing electromyography (EMG) in the evaluation of neonatal hypotonia.

The diagnosis of congenital neuromuscular disease relies on multiple tools in reaching a definitive diagnosis. The use of electromyography is usually delayed to avoid an uncomfortable procedure.

We performed a retrospective chart review of all patients with a diagnosis of hypotonia seen at our tertiary care center. We included all patients with a neonatal presentation including patients with infantile hypotonia over a 10-year period (2005 - 2015). All demographic and clinical data were reviewed and the utility of electromyography was based on contribution to diagnosis. A Pediatric Neuromuscular Specialist confirmed all cases in which utility was unclear.

We reviewed 1500 charts and included 958 in our analysis. The male to female ratio was 4:3. Premature patients comprised 176 (18%) cases. From the total group, 144 (15%) had a confirmed neuromuscular diagnosis. An additional 38 (4%) had a possible neuromuscular diagnosis and 402 (42%) were indeterminate. One hundred and nine patients (11%) had electromyography performed and 47 (43%) of them received a confirmed or possible neuromuscular diagnosis. For our EMGs, sensitivity for possible or confirmed neuromuscular disease was 72%, specificity 79%, positive predictive value 72% and negative predictive value 79%. The most common causes were central causes including HIE and mutations causing central hypotonia in 348 patients. Among neuromuscular etiologies, we found 34 cases of congenital myopathies and 10 of SMA.

The use of EMG as part of the diagnostic tools used to reach a definitive diagnosis in patients presenting with neonatal hypotonia should be strategically applied.

Central causes of hypotonia presented the majority of cases in our study.

Patients with evidence of peripheral hypotonia with or without central causes benefited the most from having a neuromuscular consult and EMG.

The use of EMG helped determining future studies.