Diagnostic utility of tectal plate measures in clinical variants of progressive supranuclear palsy

The length of the tectal plate, which sits above the midbrain, is reduced in both the Richardson's syndrome (RS) and parkinsonism (P) variants of progressive supranuclear palsy (PSP). However, it is unclear whether tectal measurements could be useful biomarkers in other PSP variants or predict PSP pathology.

The Neurodegenerative Research Group, Mayo Clinic, enrolled 115 PSP (including seven variants), 19 corticobasal syndrome (CBS), 21 Parkinson's disease (PD), and 50 controls. Forty-seven PSP patients had PSP at autopsy, and 15 had a non-PSP pathology. Tectal plate length and area and area of the superior/inferior colliculi were measured. Measurements were compared across clinical and pathological groups, and associations were assessed with clinical severity. Effect sizes were evaluated using the area under the receiver operator characteristic curves (AUROCs).

All PSP variants showed reduced tectal plate length compared to controls, with good differentiation (AUROC > 0.80). Excellent differentiation was observed for PSP-RS and PSP-P from controls (AUROC = 0.93/0.86), and PD (AUROC = 0.92/0.83), and PSP-RS showed good differentiation from CBS (AUROC = 0.80). Tectal plate and superior colliculus areas were reduced in all PSP variants, except PSP-Speech-language (SL), compared to controls. PSP-RS and PSP-P showed reduced area measurements compared to PSP-SL. No differences were observed between PSP and non-PSP pathology. Reduced tectal plate length was associated with worse clinical severity in PSP.

Tectal plate length may have utility as a disease biomarker across PSP variants, although tectal plate measurements could not predict pathology within patients clinically diagnosed with PSP.