Transcranial sonography for the discrimination of idiopathic Parkinson's disease from the atypical parkinsonian syndromes.

We reviewed eight studies on transcranial sonography (TCS) as a tool for differentiating idiopathic Parkinson's disease (IPD) from atypical parkinsonian syndromes (APS) and included some first data on TCS findings in the subforms of PSP. Changes of specific structures on TCS like the substantia nigra (SN), lenticular nucleus (LN), and the third ventricle are discussed as well as how they can contribute to differentiate between IPD, multiple system atrophy (MSA), progressive supranuclear palsy (PSP), Lewy body disease (LBD), and corticobasal degeneration (CBD). We finish with an algorithm that may be used to employ TCS as a diagnostic instrument delineating IPD from the APS and discerning among the APS themselves. As TCS is at present the most promising tool for this particular diagnostic problem, this algorithm might be a suitable hypothesis to study in future research.