Parkinson's disease-like midbrain sonography abnormalities are frequent in depressive disorders

Abstract

Substantia nigra (SN) hyperechogenicity is a characteristic transcranial sonography (TCS) finding in idiopathic Parkinson's disease. SN hyperechogenicity, found also in approximately 10% of healthy adults, was related to a subclinical malfunction of the nigrostriatal dopaminergic system on PET studies and is, therefore, thought to represent a risk marker for Parkinson's disease. Epidemiological findings suggest an increased risk in subjects with depression. To find out whether frequency of SN hyperechogenicity is increased in depression, we performed TCS of brainstem and basal ganglia in 200 subjects: 55 controls without depression and without Parkinson's disease, 55 subjects with depression without Parkinson's disease (D+ PD-), 45 Parkinson's disease patients without depression (D- PD+) and 45 Parkinson's disease patients with depression (D+ PD+). Marked SN hyperechogenicity was found in 13% of controls, 40% of D+ PD- (chi2 test, P = 0.001), 69% of D- PD+ (vs D+ PD-, P = 0.004) and 87% of D+ PD+ patients (vs D- PD+, P = 0.04). Reduced echogenicity of brainstem raphe, thought to reflect alteration of the serotonergic system, was more frequent in depressed than in non-depressed subjects, irrespective of presence of Parkinson's disease, confirming earlier reports. The combined finding of marked SN hyperechogenicity and reduced raphe echogenicity in Parkinson's disease patients, however, was clearly associated with a history of depression prior to Parkinson's disease onset, whereas in D+ PD- patients this combined TCS abnormality was related to motor asymmetry. In D+ PD+ patients with depression prior to Parkinson's disease onset (n = 12), larger SN echogenic sizes correlated with younger age at Parkinson's disease onset (Spearman test, r = -0.607, P = 0.036). TCS findings of other basal ganglia did not differ between the groups studied. Data suggest that in subjects with depression nigrostriatal vulnerability is frequent, and that TCS might be useful to detect individuals at risk for developing Parkinson's disease.