Final answer:
Cogwheel rigidity is a physical sign of Parkinson's disease characterized by a ratchety resistance to passive movement, indicating dysfunction in the basal ganglia.
Step-by-step explanation:
Cogwheel rigidity is a clinical manifestation often associated with Parkinson's disease. This neurological symptom is characterized by a ratchety resistance to passive movement as muscles alternately tense and relax. It's one of the cardinal signs considered during the physical examination of patients suspected to have Parkinson's disease or other forms of parkinsonism.
Cogwheel rigidity is thought to be caused by a combination of rigidity and tremor, which are both results of dysfunction in the basal ganglia, a group of nuclei in the brain that are critical for coordinating movement.