Compression of the cervical spinal cord during neck movements ("flexion myelopathy") 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 horn cell region of the lower cervical spinal cord (T2-weighted magnetic resonance images) but without evidence of dynamic spinal cord compression. In all these patients pathomechanism distinct from mechanical damage must be assumed.