A case of proximal cervical spondylotic amyotrophy in which needle electromyography contributed to diagnosis

The patient was a 65-year-old man who noticed difficulty raising his right upper limb. One month later, he began to feel numbness from the right posterior neck to the right posterior shoulder. Neurological examination revealed weakness in the muscles innervated by the right C5 and C6 nerves, but no corresponding abnormalities were identified on cervical MRI. Needle electromyography indicated fasciculation potentials, positive sharp waves and fibrillation potentials in the paraspinal muscles of the C5 and C6 levels, leading to a diagnosis of proximal cervical spondylotic amyotrophy (CSA). CSA is reported to have no significant findings on MRI in approximately half of cases. Diagnosis of CSA requires confirmation of muscle weakness and atrophy with a segmental distribution through neurological examination. Furthermore, neurogenic changes in the paraspinal muscles on needle electromyography serve as evidence of impairment from the anterior horn of the spinal cord to the posterior branches of the spinal nerves.