[Clinical Difference Between "proximal" and "distal" Type of Cervical Spondylotic Amyotrophy]

We studied 31 patients with cervical spondylotic amyotrophy. Weakness and atrophy without prominent sensory changes were started from the proximal muscles in 16 patients (proximal type), and from the distal muscles in 15 patients (distal type). In both types, the age at onset of neurological symptom ranged from thirties to sixties, and men were more frequently affected than women. Distal type patients often presented cold paresis and/or postural finger tremor, which occasionally was the initial symptom. Two patients of proximal type had muscular atrophy extended to the distal end. None of distal type patients had extension of atrophy to the proximal muscles during a long course of their illness. Most patients of proximal type had neurogenic changes on electromyography extended to the distal muscles. Neuroradiologically, proximal type patients had a cord atrophy at C4/5 intervertebral level, and distal type had cord atrophy at C5/6,6/7. We assume that the responsible lesion for the cervical spondylotic amyotrophy is in anterior horn at C5-T1 cord level for the proximal type, and at C7-T1 for the distal type. Abnormal venous circulation within the cord may cause the selective involvement of the gray matter.