Table 3 -.
Useful diagnostic tests in patients presenting with parkinsonism
| Test | Outcome | Interpretation |
|---|---|---|
| Olfactory Function (UPSIT; Sniffin Sticks) | Normosmia | Questions a PD diagnosis |
| Hyposmia | Consistent with PD | |
| Imaging | ||
| Structural MRI | Normal or signs of unrelated co-morbidity | Consistent with PD |
| Structural basal ganglia pathology (e.g., infarcts, hematoma, abscess, calcification, iron deposition), frontal meningioma, normal pressure hydrocephalus | Secondary parkinsonism | |
| Putamenal atrophy and hypointensity, putamenal rim sign, pontocerebellar atrophy, MCP atrophy, hot cross bun sign | Suggestive of MSA | |
| Midbrain atrophy (hummingbird sign), dilated 3rd ventricle, SCP atrophy | Suggestive of PSP | |
| Asymmetric parietal cortical atrophy | Suggestive of CBD | |
| MR-DWI | Normal | Consistent with PD |
| Increased putamenal diffusivity | Suggestive of MSA (may also be seen in PSP) | |
| Increased diffusivity in middle cerebellar peduncle (MCP) | Suggestive of PSP | |
| DAT-SPECT | Abnormal (asymmetric reduction of striatal tracer binding) | Consistent with PD or other degenerative parkinsonism |
| Normal | Excludes PD or other degenerative parkinsonism | |
| MIBG-SPECT | Reduced cardiac MIBG-uptake | Consistent with PD (inconclusive in early disease) |
| Normal | Suggestive of non-PD parkinsonism (inconclusive in early disease) or secondary parkinsonisms | |
| FDG-PET | Putamenal hypermetabolism (+ occipital & parietal hypometabolism) | Consistent with PD |
| Putamenal&cerebellar hypometabolism | Suggestive of MSA | |
| Frontal, caudate & brainstrem hypometabolism | Suggestive of PSP | |
| Asymmetric striatal & parietal hypometabolism | Suggestive of CBD | |
| Transcranial Ultrasound | Midbrain Hyperechogenicity & Basal Ganglia Normoechogenicity | Consistent with PD |
| Midbrain Normoechogenicity & Basal Ganglia Hyperechogenicity | May be suggestive of non-PD parkinsonism | |
| Genetic Testing | Pathogenic mutation in known PD gene | Confirms PD |
| Absence of a pathogenic mutation in known PD genes | Does not rule out PD | |
| Pathogenic mutation in a neurodegenerative disease gene other than PD genes | Suggestive of a non-PD mimic syndrome | |
*
Abbreviations: MSA: multiple system atrophy; PSP: progressive supranuclear palsy; CBD: corticobasal degeneration; MCP, middle cerebellar peduncle; SCP, superior cerebellar peduncle; MRI: magnetic resonance imaging; DWI: diffusion weighted imaging; DAT: dopamine transporter; SPECT: Single-photon emission computed tomography; MIBG: Meta-iodobenzylguanidine (myocardial scintigraphy). FDG-PET: Fluorodeoxyglucose positron emission tomography.