Background: Transcranial sonography (TCS) identifies hyperechogenic basal ganglia in extrapyramidal disorders such as Parkinson's disease or dystonia and reveals brain atrophy reflecting the stage of degeneration in Huntington's disease. Aim of the present study was to evaluate the diagnostic potential of TCS in spinocerebellar ataxia type 3 (SCA3), a neurodegenerative disease affecting the cerebellum, multiple pontine nuclei, substantia nigra, pallidum, putamen, caudate nucleus and long spinal tracts.
Methods: 15 patients with a molecular diagnosis of SCA3 and 15 age- and sex-matched healthy control individuals were examined with TCS. Echogenicity of the substantia nigra, caudate nucleus, pallidum, putamen, dentate nucleus and cerebellar white matter were determined quantitatively (substantia nigra by measuring the area of incresed echogenicity) or semiquantitatively (0 = none, 1 = mild, 2 = marked) on both sides and compared with the echotexture of defined brain structures. Additionally, the width of the lateral ventricles, the 3rd and 4th ventricle was measured in both groups.
Results: SCA3 patients exhibited hyperechogenicities of the cerebellar white matter (57%), substantia nigra (40%), the dentate nucleus (54%), putamen (40%) and pallidum (40%) significantly more frequently (p <0.05) than controls (20%, 13%, 9%, 0%, and 0% in the corresponding areas). In none of the healthy individuals a marked signal increase could be observed, whereas 53% of SCA3 subjects had at least one region with marked echogenicity. Cerebellar atrophy as demonstrated by an enlarged 4th ventricle was observed in all SCA3 patients whereas this structure could not be differentiated from surrounding parenchyma due to its small size in healthy individuals. 3rd and lateral ventricles were significantly larger in SCA patients as compared to controls (p < 0.05).
Conclusions: TCS is a suitable and non-invasive bed-side method to detect basal ganglia hyperechogenic lesions and posterior fossa abnormalities in SCA3 patients. The pattern of echotexture alterations and brain atrophy most likely reflects distribution and morphology of the neurodegenerative process.