Histopathological analysis of skeletal muscle in patients with Parkinson's disease and ‘dropped head’/‘bent spine’ syndrome

Background‘Dropped head’ and ‘bent spine’ phenomena are recognized clinical presentations of neuromuscular disorders. Similar symptoms are known in patients with parkinsonian syndromes, but their pathophysiology remains unclear. One hypothesis is a relation between the movement disorder and the skeletal muscle pathology.MethodsWe describe detailed histopathological data from 19 consecutive skeletal muscle biopsies in patients with idiopathic Parkinson's disease (PD) and concomitant ‘dropped head’ or ‘bent spine’ syndrome. A biochemical analysis of the respiratory chain complexes was also performed, and clinical, electrophysiological, and imaging data were analyzed.ResultsThe subjects developed neuromuscular symptoms 2.7 ± 2.4 years after onset of PD. We found no correlation with the age at onset of the disease, disease duration, or severity. We found no evidence for dystonia nor did we find any relationship between their anti-parkinsonian medication, and possible drug side effects. Muscle biopsies were abnormal in all patients. Based on histopathological criteria we divided the muscle pathology into three different groups, i.e. necrotizing myopathy, inflammatory myopathy, and myopathy with mitochondrial abnormalities. Biochemical analysis of respiratory chain complexes revealed abnormalities in nine patients.Conclusions‘Dropped head’ and ‘bent spine’ symptoms in association with PD appear to be accompanied by a wide spectrum of histopathological abnormalities in skeletal muscle. A muscle biopsy should be performed to identify potentially treatable conditions (i.e. inflammatory myopathies).