A parkinsonian gait suggests a lesion in which brain structure?

• A. Basal ganglia
• B. Cerebellum
• C. Posterior column
• D. Peripheral nerves

Answer: (A)

A parkinsonian gait points to dysfunction in the basal ganglia circuits that control the initiation and amplitude of voluntary movement. When dopaminergic neurons in the substantia nigra pars compacta degenerate, the striatum gets less dopamine, tipping the balance toward the indirect pathway. This increases inhibitory output from the globus pallidus interna and substantia nigra reticulata to the thalamus, dampening thalamocortical drive. The result is slower, more rigid movement with reduced arm swing, shuffling steps, stooped posture, and episodes of freezing—hallmarks of parkinsonism seen with basal ganglia dysfunction.

In contrast, cerebellar lesions produce an unsteady, wide-based gait with intention tremor; posterior column loss leads to sensory ataxia with impaired proprioception and a positive Romberg sign; and peripheral nerve problems cause neuropathic gait patterns from distal weakness or sensory loss.