Conventional Magnetic Resonance Imaging in the Diagnosis of Parkinsonian Disorders: AMeta‐Analysis

Abstract

Background Numerous conventional magnetic resonance imaging (cMRI) parameters were previously found to differentiate parkinsonian disorders with statistical significance, but effect size has not been considered. Objectives To quantify effect size of previously identified cMRI parameters that differentiated parkinsonian disorders with statistical significance. Method A PubMed search limited to studies assessing cMRI parameters in at least 2 of Parkinson's disease, progressive supranuclear palsy, multiple system atrophy, and corticobasal degeneration/syndrome were selected. Either Cohen's d or positive and negative likelihood (LR+/−) as well as diagnostic odds ratios (DORs) were calculated as appropriate. cMRI parameter was considered useful if Cohen's d > 1.94 (<20% overlap) or if LR+ > 10, LR− < 0.1, or DOR > 20. Results Literature search identified 8848 publications and 36 were included for analysis. Putaminal (Cohen's d 2.07; DOR 23–infinity), pontine (DOR 32–infinity), and middle cerebellar peduncle (Cohen's d 2.24; DOR infinity) abnormalities were most useful in differentiating multiple system atrophy while reduced midbrain (Cohen's d 2.33–8.69; DOR infinity) and superior cerebellar peduncle (Cohen's d 2.47; DOR 51–infinity) diameters separated progressive supranuclear palsy. Corticobasal degeneration/syndrome does not have any distinguishing cMRI features, but reduced midbrain diameter may help differentiate corticobasal degeneration/syndrome from Parkinson's disease (DOR infinity). When LR− was calculated, all of these features carried a value of <0.1. Conclusion A number of cMRI features consistently demonstrated large effect size in separating parkinsonian disorders. However, it is the presence and not absence of these cMRI features that is most useful in patients with low to moderate pretest probability.

Neuroimaging in Frontotemporal Dementia: Heterogeneity and Relationships with Underlying Neuropathology

“…The degree of brainstem degeneration is greater in PSP-RS, PSP-P, and PSP-PAGF and is associated with pronounced atrophy of the midbrain and superior cerebellar peduncles, which are characteristic findings on structural MRI [ 190 , 191 ]. Additionally, several neuroimaging findings have been proposed as suggestive of PSP pathology, including the “hummingbird sign,” “Mickey Mouse sign,” and “morning glory sign.” However, their sensitivity in clinical practice is limited [ 192 , 193 ]. The hummingbird sign is seen on midline sagittal T1 sequences as atrophy of the midbrain, resulting in a flattening or concavity of the superior aspect of the midbrain, which is normally convex [ 194 , 195 ].…”

“…Additionally, several neuroimaging findings have been proposed as suggestive of PSP pathology, including the "hummingbird sign," "Mickey Mouse sign," and "morning glory sign." However, their sensitivity in clinical practice is limited [192,193]. The hummingbird sign is seen on midline sagittal T1 sequences as atrophy of the midbrain, resulting in a flattening or concavity of the superior aspect of the midbrain, which is normally convex [194,195].…”

Pragmatic Approach on Neuroimaging Techniques for the Differential Diagnosis of Parkinsonisms

“…22 In clinical practice, this pattern of brain atrophy in PSP is also supported by a recently published meta-analysis, which found that the presence of reduced midbrain and SCP diameters were useful to separate PSP from PD. 24…”

“…The underlying neuropathological changes that occur in MSA can be visualized using regional volume changes that reflect significant brain atrophy in the putamen, MCP, cerebellum, pons, and medulla oblongata 24,26 . In daily practice and integrated with clinical criteria, structural imaging can assist in the diagnosis and differential diagnosis of MSA, as exemplified by the demonstration of putaminal, pontine, and MCP atrophy in MRI in both Multiple system atrophy ‐ cerebellar subtype (MSA‐C) and MSA‐P.…”

Atypical Parkinsonian Syndromes and Subtypes of Parkinson's Disease. Will a Single Neuroimaging Modality Ever Be Enough?

“…Additionally, the effect size of these features in differentiating parkinsonian disorders has not been fully investigated. Dr. Lee from Box Hill Hospital, Australia, has performed a meta‐analysis to quantify the effect size of the most common cMRI features that have been reported to differentiate parkinsonian disorders with statistical significance 2 . Thirty‐six papers assessing cMRI findings in at least 2 Parkinsonian disorders, including PD, were included in the analysis that demonstrated a large effect size in differentiating parkinsonian disorders for the presence but not the absence of some characteristic cMRI features (putaminal, pontine, and middle cerebellar peduncle abnormalities for multiple system atrophy; reduced midbrain and superior cerebellar peduncle diameters for progressive supranuclear palsy).…”