A 53-year-old woman presents with increasing weakness, most noticeable in the legs. She has noticed some cramping and weakness in the upper extremities as well. She has more difficulty removing the lids from jars than before. She has noticed some stiffness in the neck but denies back pain or injury. There is no bowel or bladder incontinence. She takes naproxen for osteoarthritis and is on alendronate for osteoporosis. She smokes one pack of cigarettes daily. The general physical examination reveals decreased range of motion in the cervical spine. On neurological examination, the patient has 4/5 strength in the hands with mild atrophy of the interosseous muscles. She also has 4/5 strength in the feet; the weakness is more prominent in the distal musculature. She has difficulty with both heel walking and toe walking. Reflexes are hyperactive in the lower extremities. Sustained clonus is demonstrated at the ankles.
What is the best next step in her management?a. Obtain MRI scan of the head
Cervical spondylosis (arthritis) or midline disc protrusion can cause cervical myelopathy, which can mimic amyotrophic lateral sclerosis. The neck pain and stiffness can be mild, and the patient can have both lower motor neuron signs such as atrophy, reflex loss, and even fasciculations in the arms and upper motor neuron signs such as hyperreflexia and clonus (from cord compression) in the legs. Therefore, the diagnosis of ALS is never made without imaging studies of the cervical cord, as compressive cervical myelopathy is a remediable condition. Starting riluzole to slow the progression of ALS would, therefore, be inappropriate at this point. Disease in the cortex would never cause this combination of bilateral upper and lower neuron disease, so an MRI scan of the brain would be superfluous. Myopathies such as polymyositis or metabolic myopathy cause more proximal than distal weakness and would not be associated with hyperreflexia. You should think of disease of the neuromuscular junction (eg, myasthenia gravis) or muscle when the neurological examination is normal except for weakness. Simply referring the patient for physical or occupational therapy would leave her potentially treatable cervical spine disease undiagnosed. Decompressive surgery can improve symptoms and halt progressive loss of function in cervical myelopathy.