Neuroradiological Correlates of Abnormal Pupillary Light Reflex Findings Among Patients in the Neuroscience Intensive Care Unit.

Abstract: BACKGROUND: Changes in pupil reactivity secondary to cerebral mass effect are traditionally linked to compression of the oculomotor nerve by the uncus or by horizontal midbrain displacement. The neurological pupil index (NPi) is a metric to assess the pupillary light reflex. This study explores the relationship of midline shift, cisternal, and sulcal effacement or ventricular compression in patients with a new finding of abnormal pupillary light reflex. METHODS: This retrospective study identified adult patients with serial pupillometer readings between 2018 and 2023 who had a baseline head computed tomography (CT) scan, subsequent new-onset NPi worsening from normal to abnormal, and a repeat CT scan within 2 hours of the NPi changes. Those with NPi worsening were compared with those with no NPi change. RESULTS: Among 77 patients (27 with NPi worsening, 50 without), those with NPi worsening exhibited a higher incidence of midline shift on the repeat CT. Regression models revealed a significant correlation between midline shift change and abnormal NPi ( r = 0.2260, P < .001). However, NPi worsening was not linked to changes in ventricular compression, nor sulcal or cisternal effacement. CONCLUSION: Midline shift, rather than cisternal or sulcal effacement, is associated with abnormal NPi values.