Substantia nigra hyperechogenicity as a marker of predisposition and slower progression in Parkinson's disease.

Increased echogenic size (hyperechogenicity) of the substantia nigra (SN) is a characteristic transcranial sonography finding in patients with Parkinson's disease (PD). The SN echogenic size does not change in the course of the disease. In order to see whether this stable ultrasound marker may give any implications for the rate of PD progression, we sonographically investigated 16 PD patients in whom the rate of progression had been determined by serial 18-fluorodopa positron emission tomography over a follow-up period of 65.7+/-26.7 months. We found a significant negative correlation between the right-to-left averaged SN echogenic size and the rate of disease progression in the caudate nucleus and in the putamen. There was a tendency towards a younger age at symptom onset in patients with SN hyperechogenicity. It may therefore be hypothesized that a differing influence of factors determining SN echogenicity early in life and impairing forces occurring later in life may account for different pathogenetic subgroups of idiopathic PD. Copyright (c) 2005 Movement Disorder Society.