Juvenile asymmetric segmental spinal muscular atrophy (Hirayama's disease)- Three cases without evidence of "flexion myelopathy"

Compression of the cervical spinal cord during neck movements ("flexion mye lopathy") was proposed to be the main pathomechanism of juvenile asymmetric spinal muscular atrophy (JASSMA). We present 3 patients with the clinical appearance of JASSMA and typical high-intensity, signals in the anterior ho rn cell region of the lower cervical spinal cord (T-2-weighted magnetic res onance images) but without evidence of dynamic spinal cord compression. In all these patients pathomechanism distinct from mechanical damage must be a ssumed.