The patient is an adult with decreased pain and temperature sensation in the upper extremities, atrophy of the intrinsic muscles of his hand, and brisk deep tendon reflexes in the upper extremity. This constellation of clinical findings strongly suggests syringomyelia, which most commonly affects the cervical spinal cord. Syringomyelia refers to a fluid-filled space within the cervical spinal cord that produces (1) cervical cord enlargement, best visualized with magnetic resonance imaging; (2) cape-like neurologic abnormalities involving the shoulders and upper extremities; (3) decreased pain and temperature sensation from involvement of the crossed lateral spinothalamic tracts, with preservation of light touch and proprioception; (4) atrophy of the small muscles of the hands from anterior horn cell involvement, simulating amyotrophic lateral sclerosis; (5) involvement of the lateral coicospinal tract with upper motor neuron findings; (6) Horner's syndrome, consisting of pupillary constriction, lid lag, and anhidrosis; (7) and associations with Arnold-Chiari malformation and Dandy-Walker cysts. Regarding the other choices: Amyotrophic lateral sclerosis involves motor neurons producing upper and lower motor neuron disease. Sensory findings are not present. Multiple sclerosis has sensory and motor deficits. Subacute combined degeneration occurs in vitamin B12 deficiency and involves the dorsal columns and the lateral coicospinal tract. Guillain-Barre syndrome is an ascending paralysis without the type of sensory deficits described in this patient. Ref - Harrison's principles of internal medicine 20e pg 3180,3180f