Which disorder is described by parkinsonism without tremor, along with early postural instability and axial rigidity?

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Progressive Supranuclear Palsy best fits this pattern: parkinsonism without tremor, with early postural instability and axial rigidity. In PSP, degeneration affects brainstem and basal ganglia circuits, leading to parkinsonian features that are often symmetric but notably lack tremor. The axial rigidity (stiffness of the neck and trunk) and rapid postural instability—producing falls early in the disease—are key clues that distinguish PSP from classic Parkinson disease, where tremor is common early and gait problems tend to be less prominent at onset.

A hallmark feature to look for is impaired vertical gaze (supranuclear gaze palsy) that develops as the disease progresses, reinforcing the PSP pattern. The underlying pathology is a tauopathy, with widespread involvement of regions controlling eye movements, posture, and balance.

Corticobasal degeneration typically shows asymmetric motor findings with cortical signs like apraxia and alien limb; Multiple System Atrophy adds autonomic failure and cerebellar signs; Parkinson disease dementia centers on cognitive decline accompanying PD, usually with tremor and a different progression.