脊椎・脊髄疾患の臨床診断と電気診断

抄録

Diagnostic measures for spinal cord or root disorders include imaging studies, typically spine MRI, electrodiagnostic studies, and clinical evaluations. MRI may be thought to be the most useful measure, although it is not at all perfect regarding specificity as well as sensitivity. In fact, neurological examinations, especially the manual muscle testing (MMT), are the most reliable measure. Electrodiagnostic measures such as nerve conduction studies and needle EMG evaluate function of the nervous system and can complement neurological signs.

Myotome is the basis for the localization of spinal and neuromuscular disorders. Existing myotomal charts often lack mention to the source of their identifications. Only few studies have provided raw data for myotomal localization. Their methods include pursuit of the nerve course during the systematic dissection, intraoperative root stimulation, and clinical and electromyographical investigations of the single–root radiculopathy. We also published two studies regarding myotome, one for C8/T1 myotomes of forearm flexors, and the other for C5/6/7 myotomes.

Cervical spondylotic amyotrophy (CSA) is a disorder characterized by atrophy and weakness of upper–limb muscles with no or minimal sensory symptoms/signs or long–tract signs. Important differential diagnoses of CSA are neuralgic amyotrophy (NA) and amyotrophic lateral sclerosis (ALS). Among these 3 disorders, only CSA presents with an accurate myotomal distribution of the weakness. Distal type of CSA often presents with drop finger, and its differentiation from NA presenting with posterior interosseous nerve palsy would be achieved by documenting involvements of ulnar–innervated forearm and intrinsic hand muscles. CSA is an important ALS mimic in Japan. Selective involvements in ALS, not only split hand but split finger, arm sparing and weak shoulder signs, would contribute to their differentiation.