A 14-Year-Old Girl Is Brought to the Physician for a Follow-Up

A 14-year-old girl is brought to the physician for a follow-up examination. She has had frequent falls over the past 2 years. During the past 6 months, she has been unable to walk or stand without assistance and she now uses a wheelchair. Her mother was diagnosed with a vestibular schwannoma at age 52. Her vital signs are within normal limits. Her speech is slow and unclear. Neurological examination shows nystagmus in both eyes. Her gait is wide-based with irregular and uneven steps. Her proprioception and vibration senses are absent. Muscle strength is decreased especially in the lower extremities. Deep tendon reflexes are 1+ bilaterally. The remainder of the examination shows kyphoscoliosis and foot inversion with hammertoes. .  This patient most likely has which of the following neuropathologic findings?

A) Atrophy of the caudate nucleus
B) Cerebral cortex atrophy
C) Degeneration of the spinocerebellar tracts
D) Demyelination of peripheral nerves
E) Loss of neurons in the anterior horn of the spinal cord
F) Loss of neurons in the substantia nigra