Objective: To assess the specificity and reliability of the bedside assessment of downgaze palsy by amplitude based on the upper edge of the iris relative to the intercanthal line.

Background: Downgaze palsy is the most specific feature in PSP Richardson syndrome (-RS) and parkinsonism (-P) ^1-3. Its progression rate is also associated with disease prognosis and survival ^4-7. However, assessing downgaze palsy at bedside could be challenging, based on slow downgaze saccades at early stage and limited downgaze amplitude (palsy) at early stage and thereafter ⁸. Rating slow saccades is not easy at bedside, but rating downgaze palsy by limited amplitude could be easier if we have a reliable marker. The intercanthal line (connecting the external and internal canthus) has been reported as a very useful marker for that purpose, with the upper edge of the iris going above that line reflecting downgaze palsy in PSP, with an interrater reliability of 0.98 in the intraclass correlation coefficient (ICC) ⁵. However, the specificity of this marker and the intrarater reliability remain unknown.

Method: We have assessed downgaze limits in 36 healthy people without parkinsonism, central neurological diseases or eye surgery (M/F 15/21, 62.9 ± 8.7 YO at the assessment) and 50 patients with PD without eye surgery (M/F 29/21, 72.6 ± 10.4 YO, disease duration 10.4 ± 4.6 years) when they strived to look down, and compared to these in 23 patients with probable PSP as revealed before ⁵. We have also blindly rated downgaze palsy twice in 18 patients with probable PSP-RS/PSP-P within three months apart (M/F 10/8, 71.8 ± 6.3 YO, disease duration 3.3 ± 2.2 years), and calculated the intrarater reliability by ICC between the visits.

Results: We have found that none of the 86 healthy people and PD patients had their upper edges of the iris above the intercanthal line when they strived to look down, while the 23 patients with probable PSP in our previous report had their upper edges of the iris all above the intercanthal line ⁵. We also found a high intrarater reliability of 0.99 in ICC of the downgaze palsy rated twice from the 18 patients with PSP.

Conclusion: The bedside assessment of downgaze palsy based on the position of the upper edge of the iris relative to that of the intercanthal line has a high specificity and interrater and intrarater reliabilities, which would significantly help make a diagnosis and predict prognosis in PSP.

References: 1. Litvan I, Agid Y, Kankovic J, Goetz C, Brandel JP, Lai EC, et al. Accuracy of clinical criteria for the diagnosis of progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome). Neurology. (1996) 46:922–30.
2. Litvan I, Agid Y, Calne D, et al. Clinical research criteria for the diagnosis of progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome): report of the NINDS-SPSP International Workshop. Neurology 1996;47:1–9.
3. Hoglinger GU, Respondek G, Stamelou M, et al. Clinical diagnosis of progressive supranuclear palsy: the movement disorder society criteria. Mov Disord 2017;32:853–864.
4. Xie T, Kang UJ, Kuo SH, Poulopoulos M, Green P, Fahn S. Comparison of clinical features in pathologically confirmed PSP and MSA patients followed at a tertiary center. npj Parkinsons Dis 2015; 1:15007.
5. Xie T, Yuen CA, Kang W, Padmanaban M, Hain TC, Nichols J. Severity of downgaze palsy in the context of disease duration could estimate survival duration in patients with progressive supranuclear palsy. Front Neurol 2021;12:736784.
6. Xie T, Wills AM, Liao C, et al. Using downgaze palsy progression rate to model survival in PSP-Richardson syndrome. Mov Disord 2023;38:304-312.
7. Xie T, Liao CH, Golbe LI. Early, middle, and late-stage progression rates in
progressive supranuclear palsy-Richardson syndrome. Mov Disord Clin Pract 2023;10: 1824-1826.
8. Golbe L, Ohman-Strickland PA. A clinical rating scale for progressive supranuclear palsy. Brain 2007;130:1552–1565.

« Back to 2024 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/bedside-assessment-of-downgaze-palsy-by-amplitude-in-patients-with-progressive-supranuclear-palsy/