Final answer:
The symptom of taking small steps when turning in a patient with Parkinson's disease is known as bradykinesia, which is a characteristic motor sign of the degenerative brain disorder. Bradykinesia is not related to ataxia, decussation, or dystonia, but is specifically linked to the slowness of movement associated with the loss of dopamine-producing neurons in the midbrain. The correct option is D .
Step-by-step explanation:
When a patient with Parkinson's disease is asked to turn, the small steps taken until the turn is complete are a manifestation of bradykinesia. Bradykinesia refers to the slowness of movement, and it is one of the hallmark motor signs of Parkinson's disease. This neurological condition is a degenerative brain disorder characterized by the progressive death of neurons in the midbrain, particularly in the substantia nigra, which leads to a decrease in dopamine. Parkinson's disease presents with muscular symptoms including tremor, rigidity, slowness of movement, and postural instability.
Other options like ataxia do not correspond to the described symptom, as ataxia is a disorder of the cerebellum leading to a loss of coordination and is not typically associated with Parkinson's disease. Decussation refers to the crossing of nerve fibers from one side of the brain to the other and is unrelated to the symptom described. Dystonia involves involuntary muscle contractions causing repetitive movements or abnormal postures, which is different from the small-step gait in Parkinson's disease.
The pathology of Parkinson's disease involves the accumulation of Lewy bodies, which are abnormal aggregates of protein that develop inside nerve cells, and the loss of dopamine neurons. This results in a variety of motor and non-motor symptoms, such as tremor, muscle stiffness, slow movements, gait and balance problems, as well as dementia and depression in advanced stages. Treatment for Parkinson's disease includes medications designed to manage symptoms, primarily by increasing dopamine levels or mimicking its action. However, as the disease progresses, these treatments become less effective and can lead to side effects such as involuntary movements.