Objective: To evaluate eye movement abnormalities in patients with neurodegenerative versus non-neurodegenerative parkinsonism.

Background: Clinical distinction between neurodegenerative and non-neurodegenerative parkinsonism can be difficult[1]. Eye movement abnormalities are frequent in patients with Parkinson disease[2]. However, it is unclear if eye movement abnormalities on physical examination are clinically useful in distinguishing neurodegenerative versus non-neurodegenerative causes of parkinsonism.

Method: This is a prospective, single-center, rater-blinded, case control study. Patients with neurodegenerative parkinsonism having at least grade 2 dopaminergic loss on Dopamine Transporter (DaT) scan and patients with non-neurodegenerative parkinsonism confirmed clinically by a movement disorder specialist and by a normal DaT scan were recruited at Cleveland Clinic. Eye movement examination was recorded and shown to two blinded movement disorder specialists to assess pursuit, saccades, presence of gaze limitation, nystagus, and square-wave jerks. Rater-agreed observations were included in further analyses. Sensitivity, specificity, positive predictive value, negative predictive value, and total accuracy were calculated for the presence of each eye movement abnormality against the DaTscan as the gold standard diagnostic tool.

Results: 99 subjects were included in the study, 50 of whom had abnormal DaT scan. Among subjects where there was inter-rater agreement, the prevalence of pursuit abnormalities and saccadic abnormalities was 43.7% and 46.4%, respectively. The interrater agreement was found to be moderate for pursuit abnormalities (κ=0.45, 71 subjects), and slight to moderate for saccadic abnormalities (κ=0.40, 69 subjects). For pursuit abnormalities, sensitivity for detecting neurodegenerative parkinsonism was 47.1% and specificity was 59.5%. For saccadic abnormalities, sensitivity was 51.4% and specificity was 58.8%. Nystagmus, square wave jerks, and gaze limitation all had relatively low prevalence in our study population.

Conclusion: Abnormalities in pursuit and saccades are likely not useful in distinguishing neurodegenerative versus non-neurodegenerative parkinsonism. The prevalence of nystagmus, square wave jerks, and gaze limitation was too low in our study population to draw any conclusions regarding these clinical signs.

References: [1] C. Scherfler, J. Schwarz, A. Antonini, D. Grosset, F. Valldeoriola, K. Marek, W. Oertel, E. Tolosa, A.J. Lees, W. Poewe, Role of DAT-SPECT in the diagnostic work up of Parkinsonism, Mov. Disord. (2007) 1229–1238. doi:10.1002/mds.21505. [2] E.H. Pinkhardt, J. Kassubek, Ocular motor abnormalities in Parkinsonian syndromes, Park. Relat. Disord. (2011) 223–230. doi:10.1016/j.parkreldis.2010.08.004.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/utility-of-eye-movement-abnormalities-in-differentiating-neurodegenerative-versus-non-neurodegenerative-parkinsonism/