Elektromyographie bei Rigid-Spine-Syndrom mit spätem Erkrankungsbeginn

Abstract

beginn Electromyography in Late Onset Rigid Spine Syndrome: The rigid spine syndrome is clinically defined as a progressive stiffness and shortening of axial muscles, based on an axial myopathy. Symptoms occur in childhood. the disease is slowly progressive and leads t o respiratory failure due to restriction of the thoracic excursion. Cardiomyopathy is an uncornmon feature. We report on the case of a 39-year old male who experienced the first symptoms of increasing stiffness of the cervical axial muscles at the age of 25. At the time of investigation, the cervical spine was completely rigid; shoulder abduction was limited to 30 degrees on both sides. Active and passive movements of all other muscles were normal. Nerve conduction studies of the lower extremities were normal. Needle electromyographic examination showed frequent positive sharp waves (PSW) and fibrillation potentials (FP) in the clinically most involved trapezius muscle. Motor unit potential (MUP) analysis of 22 potentials revealed a low amplitude (av. 0.33 mV. SD 0.23 mV). an increased rate of polyphasic potentials (7/22), an increased average phase count (4.3) and a normal potential duration (av. 9.5 ms, SD 2.4 ms). In the not involved extensor carpi radialis muscle there were only few PSW and FP, in MUP-analysis some polyphasic potential~ with low amplitude were found. Average amplitude. duration and phase count was normal. No pathological findings were found in the clinically not involved anterior tibial muscle. Muscle biopsy from the trapezius muscle revealed an increase of interstitial and endomyseal connnective tissue and atrophy of muscle fibres with central nuclei; there was no selective atrophy of one type of fibres. This is a remarkable case of an adult onset RSS with electromyographic findings suggesting an ongoing muscle disease. Diagnostic criteria and differential diagnosis of RSS are discussed.