A new study published in JAMA Neurology has identified distinguishing features of progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS) subtypes of atypical parkinsonian syndromes (APS) which may allow early diagnosis and separation from Parkinson's disease (PD).
The cohort study recruited 222 patients with APS (101 with PSP, 55 with multiple system atrophy [MSA], 40 with CBS and 26 indeterminate) and PD from movement disorder clinics across the UK from 1 September 2015 to 1 December 2018.
Patients with APS were stratified into the following groups: those with PSP-Richardson syndrome (PSP-RS), PSP-subcortical (including PSP-parkinsonism and progressive gait freezing subtypes), PSP-cortical (including PSP-frontal and PSP-CBS overlap subtypes), MSA-parkinsonism, MSA-cerebellar, CBS-Alzheimer’s disease (CBS-AD) and CBS-non-AD.
Applying the Movement Disorder Society PSP diagnostic criteria almost doubled the number of patients diagnosed with PSP from 58 to 101. Forty-nine of 101 patients with reclassified PSP (48.5%) did not have the classic PSP-RS subtype.
Patients in the PSP-subcortical group had a longer diagnostic latency and a more benign clinical trajectory than those in PSP-RS and PSP-cortical groups.
The PSP-subcortical group was distinguished from PSP-cortical and PSP-RS groups by cortical volumetric magnetic resonance imaging measures (area under the curve [AUC], 0.84-0.89), cognitive profile (AUC, 0.80-0.83), serum neurofilament light chain (NF-L) level (AUC, 0.75-0.83) and TRIM11 rs564309 genotype.
Eight of 17 patients with CBS (47.1%) undergoing cerebrospinal fluid analysis were identified as having the CBS-AD subtype.
Patients in the CBS-AD group had a longer diagnostic latency, relatively benign clinical trajectory, greater cognitive impairment and higher APOE-ε4 allele frequency than those in the CBS-non-AD group (AUC, 0.80-0.87; P<.05). Serum NF-L levels distinguished PD from all PSP and CBS cases combined (AUC, 0.80; P<.05).
The authors concluded that PSP and CBS subtypes have distinct characteristics that may enhance early diagnosis.
