Transcranial sonography in ataxia.

Transcranial sonography (TCS) identifies basal ganglia alterations in extrapyramidal movement disorders such as Parkinson's disease or dystonia. Although only rarely reported, TCS also reveals signal alterations of basal ganglia in several forms of hereditary and nonhereditary ataxia. Here, the examination procedure and its diagnostic value for the classification of ataxia are reviewed. Three TCS studies reported hyperechogenicity of substantia nigra (SN) as a frequent finding in spinocerebellar ataxia type 2, type 3, and type 17, indicating a vulnerability of the nigrostriatal system in SCA patients. A new "cerebellar examination plane" was proposed, allowing better visualization of fourth ventricle enlargement and nucleus dentatus hyperechogenicity as a characteristic finding in SCA3 patients. In sporadic Creutzfeldt-Jakob disease, a blurry inhomogeneous hyperechogenic signal pattern of lentiform nucleus was identified in all of the patients in a small case series. Furthermore, distinct bilateral hyperechogenicity of pallidostriatal regions have been described as a novel diagnostic feature in the sonographic differentiation of extrapyramidal and atactic movement disorders. TCS is a commonly available, noninvasive, and inexpensive diagnostic tool, which provides reliable information about the morphology of the brain in ataxias, even in agitated patients who do not tolerate other imaging techniques. Further neuropathological and multimodal imaging studies are needed to elucidate the precise morphological and pathogenetic background of the detected echosignal pathology, and also to correlate these findings to the various clinical features of this disease entity.