S-1 radiculopathy as a possible predisposing factor in focal myositis with unilateral hypertrophy of the calf muscles.

Associated with chronic S-1 radiculopathy, a 44-year-old man developed unilateral hypertrophy of the calf muscles. Electromyography revealed neurogenic alterations in the corresponding limb compatible with S-1 radiculopathy. In addition, MR-tomographic and bioptic findings were consistent with a focal inflammatory myopathy of the enlarged right gastrocnemius muscle. Predisposing factors for the localisation of a focal myositis are unknown. This case report highlights the diagnostic difficulties in distinguishing focal myositis and denervation hypertrophy following S-1 radiculopathy or secondary inflammation related to denervation. We consider the possibility that in our case the inflammatory process might have been triggered by electromyographically proven chronic denervation related to radiculopathy.