Role of electromyography for the diagnosis of Parsonage-Turner syndrome

Abstract

Objectives Parsonage-Turner syndrome (PTS) or neuralgic amyotrophy, is a rare idiopathic disorder characterized by acute onset of upper extremity pain, with subsequent development of muscle weakness and atrophy [1] , [2] . The pathogenesis is not fully understood, but immune-mediated process is thought to be a possible cause. We aimed to characterize the electro-clinical aspects observed in the PTS. Methods We included patients with neuralgic shoulder amyotrophy. All patients underwent physical and neurological examination. A complete biological assessment, lumbar puncture (PL), MRI of the cervical spine and electromyography (EMG) were performed in all cases. Results We report the cases of 3 patients, admitted to our neurological department for PTS. They respectively aged from 66, 20 and 72 years old. First case presented with a 2-month history of pain and 10-days history of weakness in her left wrist and hand. He reported the pain as sharp. Physical examination revealed marked atrophy and absence of strength in the shoulder muscles. Second case, came for subacute hands weakness. Neurological examination found asymmetric atrophy of the muscles of both shoulders. Third case, had sudden involuntary and brief rhythmic contraction involving upper and lower limbs mimicking myoclonus. Neurological examination noticed right shoulder atrophy and proximal muscle weakness. Biological assessment, study of cerebrospinal fluid and MRI of cervical spine were normal in all patients and excluded other causes of brachial neuritis. EMG typically consistent with PTS. It showed severe left total brachial plexopathy with acute axonal involvement and abundant acute denervation potentials, in the first case and a bilateral brachial plexopthy with severe axonal involvement in the other cases. All patients underwent high corticosteroid therapy with relative recovery. Conclusion PTS is a clinical diagnosis, however clinical presentation can sometimes lead to misdiagnosis. In such situation, the use of EMG would be a key exam to make the diagnosis of PTS.