Introduction: The indirect transmission of intracranial pressure (ICP) to the orbit via the intervening venous anatomy has lead to the proposal of intraocular pressure (IOP) as a non-invasive means of detection of intracranial hypertension (IC-HTN). We therefore sought to determine the diagnostic accuracy of IOP for IC-HTN.
Methods: Patients' greater than 18 years of age and warranting ICP monitoring were screened for enrollment. In instances of non-emergent ICP monitor placement, the measurement of IOP was performed immediately prior to and following monitor insertion. The simultaneous measurement of IOP and ICP was subsequently performed twice daily for up to eight measurements or until the termination of ICP monitoring. Outcomes included measures of the diagnostic accuracy of an IC-HTN predictive index devised through the evaluation of regressor terms for age, Glasgow Coma Scale motor score (GCS-M), hypotension, Injury Severity Score, Rotterdam CT Head Classification, PaCO2, serum sodium, and IOP.
Results: A total of 64 IOP measurements were obtained. Participants' mean age was 49.5 years, 69.2% were male, and median presenting GCS was 8. Mean ICP and IOP were 11.9 mmHg and 16.6 mmHg, respectively. The prevalence of IC-HTN during IOP measurement was 8.3%. Of the clinical characteristics evaluated, GCS-M and serum sodium were correlated with IC-HTN (coefficients of -0.45 [p-value<0.01] and 0.58 [p-value<0.001], respectively). The area under the receiver-operating-characteristics curve associated with an IC-HTN predictive index incorporating IOP, serum sodium, and GCS-M was 0.91 with a positive predictive value of 36.4% and a negative predictive value of 100.0%. No adverse events relating to IOP measurement occurred.
Conclusions: A predictive index incorporating IOP with clinical characteristics known to be associated with ICP may aid in the recognition of IC-HTN. Spectrum bias due to the low prevalence of IC-HTN among subjects may limit the utility of the derived index. Further investigation is therefore warranted prior to its adoption.
Patient Care: Our work attempts to exploit the relationship between IOP and ICP to improve upon the current accuracy of non-invasive IC-HTN diagnosis via a predictive index incorporating both IOP and existing invasive ICP monitoring indications. Such a predictive index will allow earlier recognition of IC-HTN and intervention thereby avoiding progressive cerebral ischemia while sparing those patients with normal ICP from the undue hazard from invasive ICP monitoring.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Discuss the value of intraocular pressure measurement in the evaluation of intracranial hypertension; 2) Describe the association between intraocular pressure, intracranial pressure, serum sodium, and the Glasgow Coma Scale Score; 3) Understand the limitations of the existing literature on the subject of intracranial and intraocular pressure.