<s>[INST] context: 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 corticospinal 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 corticospinal tract.  Guillain-Barre syndrome is an ascending paralysis without the type of sensory deficits described in this patient. [/INST] question: A 32-year-old patient has decreased pain and temperature sensation in the upper extremities, atro¬phy of the intrinsic muscles of his hand, and brisk deep tendon reflexes in the upper extremity. Your diagnosis? | options: A: Amyotrophic lateral sclerosis B: Multiple sclerosis C: Syringomyelia D: Subacute combined degeneration | answer: C </s>