Which neurodegenerative condition presents with asymmetric parkinsonism, apraxia (ideomotor/ideational), alien limb syndrome, and poor response to levodopa?

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This item hinges on recognizing a syndrome where movement symptoms come from cortical as well as subcortical involvement. Corticobasal degeneration typically presents with asymmetric motor symptoms starting on one side, reflecting uneven degeneration in motor and parietal regions. The apraxia—both ideomotor and ideational—shows up as trouble planning or executing purposeful movements, not just slowness or rigidity. Alien limb syndrome, where one limb seems foreign and acts with its own agenda, is another hallmark of this cortical-basal involvement. Because the impairment is not purely a dopaminergic striatal problem, these patients often have little or only transient improvement with levodopa.

In contrast, Huntington disease centers on chorea and psychiatric/cognitive changes, with at least some involvement of the basal ganglia but not the same prominent apraxia or alien limb phenomena. The syndrome typically manifests with more uniform progression rather than a strongly asymmetric onset. Normal pressure hydrocephalus presents with the triad of gait disturbance, cognitive decline, and urinary incontinence, along with ventriculomegaly on imaging, but it does not feature the apraxia or alien limb findings. Multiple system atrophy can mimic Parkinsonism and has poor levodopa response as well, but it usually shows additional autonomic failure and cerebellar/pyramidal signs and tends to be less asymmetric.

Therefore, the combination of asymmetric parkinsonism, clear apraxia, alien limb sensation, and poor dopaminergic response best fits corticobasal degeneration.