The precise threshold differentiating normal and elevated intracranial pressure (ICP) is variable among individuals. In the context of several pathophysiological conditions, elevated ICP leads to abnormalities in global cerebral functioning and impacts the function of cranial nerves (CNs), either or both of which may contribute to ocular dysmotility. The purpose of this study was to assess the impact of elevated ICP on eye-tracking performed while patients were watching a short film clip.
Awake patients requiring placement of an ICP monitor for clinical purposes underwent eye tracking while watching a 220-second continuously playing video moving around the perimeter of a viewing monitor. Pupil position was recorded at 500 Hz and metrics associated with each eye individually and both eyes together were calculated. Linear regression with generalized estimating equations was performed to test the association of eye-tracking metrics with changes in ICP.
Eye tracking was performed at ICP levels ranging from −3 to 30 mm Hg in 23 patients (12 women, 11 men, mean age 46.8 years) on 55 separate occasions. Eye-tracking measures correlating with CN function linearly decreased with increasing ICP (p < 0.001). Measures for CN VI were most prominently affected. The area under the curve (AUC) for eye-tracking metrics to discriminate between ICP < 12 and ≥ 12 mm Hg was 0.798. To discriminate an ICP < 15 from ≥ 15 mm Hg the AUC was 0.833, and to discriminate ICP < 20 from ≥ 20 mm Hg the AUC was 0.889.
Increasingly elevated ICP was associated with increasingly abnormal eye tracking detected while patients were watching a short film clip. These results suggest that eye tracking may be used as a noninvasive, automatable means to quantitate the physiological impact of elevated ICP, which has clinical application for assessment of shunt malfunction, pseudotumor cerebri, concussion, and prevention of second-impact syndrome.
Correspondence Uzma Samadani, Department of Neurosurgery, Hennepin County Medical Center and University of Minnesota, 701 Park Ave. S, PL.610, Minneapolis, MN 55415. email: firstname.lastname@example.org.
INCLUDE WHEN CITING Published online June 2, 2017; DOI: 10.3171/2016.12.JNS161265.
Disclosures Dr. Samadani has been issued a patent describing the technology used in this paper. The ICP patent which has been issued is jointly owned by New York University (NYU) and the Veterans Administration (VA). Other patents related to this work are owned by NYU, the VA, and the Hennepin County Medical Center (HCMC) and are licensed to Oculogica Inc., a company in which Dr. Samadani, NYU, the VA, and HCMC have an equity interest. She also discloses support from Abbott Diagnostic Labs and Integra, Inc., for a non–study-related clinical or research effort that she oversees. Dr. Kondziolka discloses support from Brainlab for a non–study-related clinical or research effort that he oversees.
BrattonSLChestnutRMGhajarJMcConnell HammondFFHarrisOAHartlR: Guidelines for the management of severe traumatic brain injury. VIII. Intracranial pressure thresholds. J Neurotrauma24 (Suppl 1):S55–S582007(Erratum in J Neurotrauma 25:276–278 2008)
ChesnutRBleckTCiterioGClaassenJCooperDJCoplinW: A consensus-based interpretation of the Benchmark Evidence from South American Trials: Treatment of Intracranial Pressure Trial. J Neurotrauma32:1722–17242015
FarahvarAGerberLMChiuYLHärtlRFroelichMCarneyN: Response to intracranial hypertension treatment as a predictor of death in patients with severe traumatic brain injury. J Neurosurg114:1471–14782011(Erratum in J Neurosurg 115:191 2011)
KaramanosETeixeiraPGSivrikozEVargaSChouliarasKOkoyeO: Intracranial pressure versus cerebral perfusion pressure as a marker of outcomes in severe head injury: a prospective evaluation. Am J Surg208:363–3712014
LafrenayeADKraheTEPovlishockJT: Moderately elevated intracranial pressure after diffuse traumatic brain injury is associated with exacerbated neuronal pathology and behavioral morbidity in the rat. J Cereb Blood Flow Metab34:1628–16362014