Substantia nigra hyperechogenicity correlates with clinical status and number of Parkin mutated alleles
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To further evaluate (1) transcranial sonography (TCS) for (pre)clinical diagnosis of Parkinson's disease (PD) and (2) to examine asymptomatic carriers of Parkin mutations we investigated substantia nigra (SN) hyperechogenicity in PD patients and unaffected subjects with and without Parkin mutations. The area (aSN) of the hyperechogenic SN were calculated bilaterally and study subjects were assigned to high versus low value groups. Eleven of the (affected and unaffected) mutation carriers had previously undergone 18-fluoro-dopa-(FDOPA)-PET scans. Fifty-eight individuals were investigated, including 24 with clinically definite and 34 without symptoms or signs of PD. Of the patients, three had one mutated and six had two mutated Parkin alleles. Of the unaffected subjects, 13 carried a single Parkin mutated allele. After dichotomization, 21 subjects had high and 37 subjects low values of mean aSN. Regarding the clinical status, 13 (62%) of the individuals with a high mean aSN had PD,while 26 (70%) of the study subjects with low values did not show signs of PD (p = 0.0393). Similarly, probands with high mean aSN values more frequently carried Parkin mutations (58%) than probands with low values (27%, p = 0.0234). A negative correlation between FDOPA uptake in the posterior putamen and maximum aSN was found in the group of mutation carriers (r = -0.809, p = 0.0234). In conclusion, hyperechogenicity of the SN is found in both idiopathic and Parkin-associated PD. Further strengthening the notion of a potential relationship between SN hyperechogenicity and Parkin mutational status, a larger aSN was associated with an increasing number of mutated alleles in our study.