Magnetic resonance tomography in Parkinson's syndrome

The clinical distinction of Parkinson's disease (PD) from other disorders w ith parkinsonian features is often difficult. Routine magnetic resonance im aging of the brain (MRI) is typically normal in patients with PD. However, it can be helpful in supporting a diagnosis of atypical parkinsonian disord ers and excluding non-parkinsonian disorders that can mimic parkinsonism, s uch as vascular parkinsonism or hydrocephalus. MRI in atypical parkinsonian syndromes, such as multiple-system atrophy (MSA), progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) can reveal characteristic features that cannot only differentiate these syndromes from PD, but also h elp to differentiate between these atypical disorders. These features inclu de a hyperintense rim at the lateral putaminal edge and infratentorial sign al change and atrophy in MSA, marked atrophy and hyperintensity of the midb rain on T-2-weighted images in PSP, and asymmetrical parieto-frontal atroph y in CBD. Although these findings are very specific, they are present in on ly a proportion of patients with these diseases. MRI-spectroscopy (1H-MRS) of the lentiform nucleus is similarly normal in patients with PD, but can s how a reduced ratio of N-acetyl-aspartate (NAA) to creatine-phosphocreatine (Cre) or choline (Cho) concentration in atypical parkinsonian disorders. T he pattern of reduction of NAA/Cre or NAA/Cho in other areas of the brain m ay also help to differentiate between atypical parkinsonian syndromes. Rout ine-MRI and MRI-spectroscopy are useful tools to improve clinical diagnosis of parkinsonian syndromes.