34-year-old woman with a long-standing history of seizure disorder presents to her neurologist with difficulty
walking and coordination. She has been on phenytoin for several days after having been switched from
valproic acid. She states she has had an acute change in gait, unclear speech, blurring of vision, tremor with
movement, and loss of hand coordination. She has never had symptoms like this before. She denies headache
and vertigo or any other complaints. On examination, she has an unstable gait and poor hand-eye
coordination. She is noted to have nystagmus along with a fine tremor of the hand when she is moving it. A
urine drug screen is negative. She has a computed tomography (CT) scan and lumbar puncture, which are
both normal. Phenytoin levels are slightly elevated. She is diagnosed with cerebellar ataxia, probably as a side
effect of phenytoin.
33. What parts of the cerebellum are responsible for motor planning of movement?
34. Is the output of the cerebellar cortex excitatory, inhibitory, or both and what are the neurotransmitters used
by Purkinje neurons?
35. Which deep cerebellar nuclei are involved with regulating motor execution and would likely be involved with
the tremor?
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36. What other deficits would you expect to note in this patient
