Transorbital sonographic monitoring of optic nerve diameter in patients with severe brain injury.

OBJECTIVE

We investigated whether alterations in the optic nerve diameter (OND) correlated with brain computed tomography (CT) imaging results among patients with brain injury and whether monitoring of OND could predict brain death.

PATIENTS AND METHODS

We enrolled 54 patients with brain injury (Glasgow Coma Scale < 8) and 53 controls. OND measurements were performed 3 mm posterior to the papillae by means of transorbital sonography. The severity of the injury was classified according to a semiquantitative CT neuroimaging scale (1 to 4). All patients underwent 3 repeated evaluations of OND combined with synchronous CT scans.

RESULTS

Twenty-two patients progressed to brain death, while 32 patients showed gradual clinical improvement. Upon admission, the patients showed significantly increased OND (4.84 +/- 1.2 mm) compared with the controls (3.49 +/- 1.1 mm; P < .001). The median intraobserver variation of OND was 0.2 mm (95% confidence intervals [CI]: 0.1-0.7). The median interobserver variation of OND was 0.3 mm (95% CI: 0.1-0.9). Alterations in the OND were significantly correlated with the neuroimaging scale on 3 repeated evaluations: r = .65, r = .70, and r = .73 (all P < .001). An OND greater than 5.9 mm (specificity = 65% and sensitivity = 74%; P < .01) and a 2.5 mm increased OND between repeated measurements (specificity = 70% and sensitivity = 81%; P < .01) were associated with a poor prognosis.

CONCLUSIONS

Alterations in OND strongly correlated with neuroimaging results among patients with brain injury. However, monitoring of OND exhibited a low predictive value for brain death.