Eye movement abnormalities in normal pressure hydrocephalus: a video-oculographic study

Background: Eye movement dysfunction has been widely observed in several neurodegenerative diseases. Normal pressure hydrocephalus (NPH) is a treatable condition showing marked clinical and radiological overlap with neurodegenerative parkinsonism and dementia syndromes, often posing diagnostic challenges. The current study employed video-oculography (VOG) aiming to comprehensively explore possible ocular dysfunction in NPH patients. Methods: Forty-two consecutive NPH patients and seventy-six healthy controls (HC) were enrolled in the study. Participants underwent a video-oculographic assessment including reflexive saccades and fixation tasks. Amplitude, peak velocity and latency of upward, downward, and vertical saccades were calculated, together with square wave jerks (SWJ) number and amplitude during fixation. Correlations between VOG data and clinico-radiological features were investigated. Results: NPH patients showed a significant (33.8%) increase in saccadic latency compared to HC, with no differences in saccadic amplitude and peak velocity. The number and amplitude of SWJ were also similar between NPH and HC groups. Saccadic latency was specifically associated with cognitive deficits, especially phonemic fluency and executive functions, in the NPH group. Conclusion: This study characterized ocular dysfunction in NPH patients, demonstrating an increase of saccadic latency in comparison with HC, strongly associated with cognitive impairment. These results identified saccadic latency as a rapid and quantitative VOG biomarker of cognitive deficits in NPH, holding potential for repeated assessment of cognitive status over time. On the other hand, saccadic amplitude and velocity were not affected in NPH, thus suggesting their possible role in the differential diagnosis between NPH and neurodegenerative parkinsonian syndromes.