Influence of dopamine and disease severity on primitive reflexes in Parkinson's disease.

Several primitive reflexes are common in patients with Parkinson's disease (PD), but can also be noted in patients who have diffuse cerebral degeneration. The glabellar response is present in virtually all patients with PD and this reflex has been of theoretical interest in PD. It has been suggested that the glabellar response is related to inhibition via dopamine pathways. We examined changes in several primitive reflexes as a function of the plasma dopamine level and the severity of PD. The probability of observing these reflexes did not vary with dopamine levels, but the corneomandibular and palmomental reflexes were significantly more likely to be present in patients with advanced disease. Our findings confirm that primitive reflexes are prominent in PD and suggest that they may be secondary to extrapyramidal disease.