Substantia nigra hyperechogenicity in hypokinetic Huntington's disease patients

Substantia nigra (SN) hyperechogenicity can be detected by transcranial sonography (TCS) to assist the early diagnosis of idiopathic Parkinson's disease (IPD). This study prospectively investigated whether SN hyperechogenicity is also present in Huntington's disease (HD) patients with symptoms of hypokinesia and/or rigidity. All patients recruited to the study (n = 15) were characterised by hypokinesia and/or rigidity while nine of these patients also displayed chorea and/or dystonia. The control group included 15 individuals. Clinical examination was documented using the Unified Huntington's Disease Rating Scale (UHDRS). TCS examination revealed SN hyperechogenicity in 14/15 (93.3 %) patients (9/14 unilateral, 5/14 bilateral). Hyperechogenicity of the caudate and lentiform nuclei (CN, LN) was less frequent (CN: 80 % total, LN: 53.3 % total). This is the first study to assess SN hyperechogenicity in hypokinetic HD patients. Assuming that the primary sites of pathology in IPD and HD are the SN and the striatum, respectively, our observations suggest a functional impairment of the nigrostriatal system in HD, an effect that is potentially independent of the primarily-affected basal ganglia nucleus.