Introduction
Idiopathic inflammatory myositis is characterized by muscle weakness and inflammation. Acute markedly asymmetrical weakness is a rare clinical presentation of inflammatory myositis. Neuromyositis, which has been very rarely reported, is the concomitant involvement of the peripheral nerve system in inflammatory myositis. Herein, we describe a case of acute peripheral neuropathy with inflammatory myositis diagnosed by electrodiagnostic study.
Case
A 62-year-old man with a history of hepatitis B virus carrier and chronic alcoholism visited an outpatient clinic regularly for radicular pain in the right lower extremity with mild lower back pain. He had undergone nerve root block of L4-L5 under lumbar radiculopathy diagnosis. A week postoperatively, he presented to the emergency room with right ankle weakness and hypesthesia in the foot dorsum area with posterior thigh pain. Manual muscle testing was normal except for ankle dorsiflexion and plantarflexed, great toe dorsiflexion (grade 0). Tenderness of the right hamstring muscles was observed. Initial laboratory data showed elevated serum levels of CPK (448 2U/L), WBC (12,440 cells/mm3), ALT (101 U/L), CRP (0.76 mg/dL), and ESR (18 mm/h) and straw-colored urine. Emergency lumbar MRI showed no definite root compression. On the next day, CPK and ALT levels increased to 10,677 and 243 U/L, respectively. The initial electrodiagnostic test showed decreased SNAP amplitude in the right peroneal and tibial nerves and no MUAP in the right lower leg muscles. MRI showed diffuse inflammation of the gluteus maximus, right vastus lateralis, hamstring, adductor muscles, and proximal portion of tibialis anterior, extensor hallucis longus, and extensor digitorum longus muscles. Under the diagnosis of inflammatory myositis with peripheral neuropathy, hydration and steroid therapy were initiated. With steroid therapy, his thigh pain gradually improved, but his foot pain persisted. At 3-week follow-up, the electrodiagnostic test suggested right sciatic axonal neuropathy with myopathy in the vastus lateralis and adductor muscles. Muscle biopsy showed severe chronic inflammation and necrosis. CD8+ T cells and macrophages (CD68+) were observed in inflamed tissues, as well as few foci of endomysial and perivascular cuffing of the inflammatory cells without vacuoles and filamentous inclusions in the muscle tissues, which can be seen in inflammatory myositis. At 3-month follow-up, the sciatic neuropathy remained stationary with incomplete recovery. The patient could walk with an ankle foot orthosis and crutch without improvement in ankle muscle power.
Conclusion
Electrodiagnostic studies were consistent with axonal neuropathy, which caused the markedly asymmetrical weakness in inflammatory myositis. This case illustrates a previously undescribed neuromyositis, a possible neurological complication of myositis, in the electrodiagnostic field. |
