Optical pupillometry in traumatic brain injury: neurological pupil index and its relationship with intracranial pressure through significant event analysis

Brain Inj. 2019;33(8):1032-1038. doi: 10.1080/02699052.2019.1605621. Epub 2019 Apr 25.


Primary Objective: Treatment paradigms for traumatic brain injury (TBI) rely on invasive monitoring of intracranial pressure (ICP) for planning intervention. Optical pupillometry is a non-invasive, objective monitoring method, measuring parameters of pupillary response and displaying a scalar value - a neurological pupil index (NPi). An impaired response on NPi has been tentatively correlated with ICP, through analysis of mean/peak NPi and ICP readings. We sought to evaluate this relationship more closely. Research Design: Prospective observational. Methods and Procedures: We obtained hourly pupillometry readings, alongside ICP values, from 40 patients with TBI requiring invasive ICP monitoring. Significant events were identified for analysis based on the significant aberration of ICP or NPi. Main Outcomes and Results: On average, individuals experienced a few significant events. There was a weak relationship between ICP events and a preceding NPi event. The results show that there is a weak but statistically insignificant relationship between NPi and ICP, where reduced pupil reactivity may indicate a raised ICP. The strength of this trend appears to diminish post-decompressive surgery. Conclusions: Whilst pupillometry may not be a reliable surrogate marker for ICP, NPi may still prove to be a useful tool in a multimodal prognostic assessment of the patient with acute brain injury.

Keywords: Head trauma; ICP measurements; intracranial pressure; monitoring.

Publication types

  • Observational Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Brain Injuries, Traumatic / complications
  • Brain Injuries, Traumatic / diagnosis*
  • Brain Injuries, Traumatic / physiopathology*
  • Diagnostic Techniques, Ophthalmological*
  • Female
  • Humans
  • Intracranial Pressure / physiology*
  • Male
  • Middle Aged
  • Neurologic Examination / methods
  • Prospective Studies
  • Pupil / physiology
  • Reflex, Pupillary / physiology*
  • Young Adult