To determine the clinical, pathological, and magnetic resonance imaging (MRI) characteristics and outcome of focal myositis of the calf associated with S1 radiculopathy.
Case report and systematic review of literature using a literature review based on a Medline search from 1950 to 2006. Only cases with myositis documented on muscle biopsy examination were included.
Six patients, including ours, with focal myositis of the calf associated with chronic S1 radiculopathy have been reported. Creatine phosphokinase levels were high in 5 cases. MRI provided evidence of global hypertrophy and inflammatory signals affecting the whole of 1 or several muscle heads of the triceps. Electromyography confirmed the existence of neurogenic abnormalities with nearly constant spontaneous activity. Histological analysis of muscle tissue showed an inflammatory infiltrate and denervation lesions. Progression was slow and corticosteroid treatment had little effect. There was no extension toward a diffuse form.
Hypertrophy in a denervated muscle should lead the physician to consider a diagnosis of localized secondary myositis. On the other hand, localized hypertrophic myositis is suggestive of previous radicular distress in the territory concerned. The identification of this condition in focal myositis makes it possible to avoid unnecessary additional investigations and escalation of treatment.