[Juvenile muscular atrophy of the bilateral upper limbs associated with peculiar transformation of the dural tube induced by neck flexion].

We described an 18-year-old man with slowly progressive muscular atrophy in upper limbs on both sides. Regarding muscular atrophy, sensory disturbances in both palms were disproportionally very mild. Electrophysiological study suggested involvement of anterior horn restricted to the cervical cord, which resembled juvenile muscular atrophy of unilateral upper limb (Hirayama's disease). This patient, however, was unique in that the atrophy was bilateral and wider distribution of a lesion from C5 to T1 segments unlike Hirayama's disease. Neuroradiological findings in neutral position of the neck showed no abnormalities, but in flexion there was a characteristic change of the cervical cord and the posterior wall of dural canal. On myelography in flexion, anterior-posterior diameter of the middle and lower cervical dural canal decreased presumably due to an anterior shift of the dorsal part of dura mater. CT-myelography in neck flexion showed characteristic folding of the dorsal part of dura mater whose median portion seemed to intrude anteriorly and consequently concave the spinal cord. Anterior shift of the dorsal part of dura mater is known to occur in Hirayama's disease, but the folding is a peculiar finding in this patient. After laminectomy and laminoplasty of vertebrae from C3 to C7, his symptoms improved a little. On palpating the dorsal surface of dural canal, its median portion was harder than the lateral portion. A small fraction of the dura mater which was removed from hard median portion was thick, but showed no histological abnormalities. In normal functioning anatomy the dural canal is lengthened more posteriorly than anteriorly with neck flexion.(ABSTRACT TRUNCATED AT 250 WORDS)