Ultrasonography of the optic nerve sheath in brain death

Evaluation of optic nerve sheath by means of optic nerve ultrasonography (ONUS) is a reliable tool for assessment of patients with increased intracranial pressure. The aim of this study was to present the usefulness of optic nerve sheath ultrasonography in patients with brain death.

Ten patients with brain death as a result of traumatic or non-traumatic causes were evaluated by ONUS. Optic nerve sheath diameter (ONSD) was measured with a 12 MHz linear ultrasound probe (Terason T3000, Teratech Corporation, USA). The probe was adjusted to give a suitable angle for displaying the entry of the optic nerve into the globe, at the depth of 3 mm behind the globe. For each optic nerve four measurements were made, twice in transversal and twice in the sagittal plane, by rotating the probe clockwise. Mean ONSD for brain death patients were compared with mean ONSD of 17 healthy controls.

Ten individuals (7 males) with confirmed brain death (5 due to neurotrauma, 2 due to subarachnoid hemorrhage, 2 as a result of ischemic strokes and one of parenchymal hemorrhage), were evaluated. On the left side mean ONSD was 0.71 ± 0.06 cm on transversal plane and 0.72 ± 0.04 cm on sagittal plane. On the right side mean ONSD was 0.73 ± 0.05 cm on transversal plane and 0.73 ± 0.06 on sagittal plane. In controls left mean ONSD was 0.51 ± 0.05 cm on transversal plane and 0.55 ± 0.06 cm on sagittal plane. On the side right mean ONSD was 0.52 ± 0.05 cm on transversal plane and 0.54 ± 0.07 on sagittal plane. Mean ONSD in brain death was 0.72 ± 0.05 cm and 0.53 ± 0.06 cm in controls (p < 0.01).

Measurements of ONSD may be useful in distinguishing brain death persons from healthy controls.