Clinical and radiological profile of Hirayama disease: A flexion myelopathy due to tight cervical dural canal amenable to collar therapy

Background: Hirayama disease (HD) is benign focal amyotrophy of the distal upper limbs, often misdiagnosed as motor neuron disease. Routine magnetic resonance imaging (MRI) is often reported normal. Objective: To study the clinicoradiological profile of hand wasting in young males. Materials and Methods: Patients presenting with insidious-onset hand wasting from March 2008 to May 2011 were evaluated electrophysiologically. Cervical MRI in neutral position was done in 11 patients and flexion contrast imaging was done in 10 patients. Results: All patients were males less than 25 years of age, with median age 23 years, except one patient who was 50 years old. Duration of illness was 3 months to 3 years. All (100) had oblique amyotrophy, four (36) cold paresis, 10 (91) minipolymyoclonus and three (27) had fasciculations. Regional reflexes were variably absent. Two patients (18) had brisk reflexes of lower limbs with flexor plantars. Electromyography (EMG) showed chronic denervation in the C7-T1 myotomes. Neutral position MRI showed loss of cervical lordosis in 10/11 (91), localized lower cervical cord atrophy in 9/11 (82), asymmetric cord flattening in 11/11 (100) and intramedullary hyperintensity in 2/11 (18); flexion study showed loss of dural attachment, anterior displacement of dorsal dura, epidural flow voids in 9/10 (90) and enhancing epidural crescent in 10/10 (100). Clinical profile, imaging and electrophysiological findings of the patient aged 50 years will be described in detail as presentation at this age is exceptional. Collar therapy slowed progression in most cases. Conclusion: Clinical features of HD corroborated well with electrophysiological diagnosis of anterior horn cell disease of lower cervical cord. While dynamic contrast MRI is characteristic, routine studies have a high predictive value for diagnosis. Prompt diagnosis is important to institute early collar therapy.