Clinical commentaryNoninvasive assessment of the intracranial pressure in non-traumatic intracranial hemorrhage

- The optic nerve sheath diameter was enlarged in cases of intracranial hemorrhage.
- In these cases the diameter was enlarged by the elevated intracranial pressure.
- This enlargement correlated with invasive readings of the intracranial pressure.
- Measuring the diameter serves for noninvasive assessment of the intracranial pressure.
- This technique can be further improved to achieve greater accuracy.

The article describes the modified technique of measuring the diameters of the optic nerve sheath (ONSD) for assessment of the intracranial pressure (ICP) in patients with intracerebral or subarachnoid hemorrhage (SAH). The CT scans of 443 patients were analyzed retrospectively. The ONSDs were measured at 3 mm behind the globe and at the point where the ophthalmic artery crosses the optic nerve. The ONSD/eyeball transverse diameter (ETD) ratio was calculated. The correlation analysis was performed with the Glasgow Coma Scale score, Hemispheric Stroke Scale score, Glasgow Outcome Score, and invasive ICP readings. ONSD was enlarged in 95% of patients with intracerebral hemorrhage or SAH. Pathological ONSDs were 6.6 ± 0.8 mm (cut-off value >5.5 mm; p < 0.05). ONSD/ETD ratio was 0.29 ± 0.05 against normative 0.19 ± 0.02 (p < 0.01) with no correlation with initial Glasgow Coma Scale score or Hemispheric Stroke Scale score. There was an inverse correlation between ONSD/ETD ratio and Glasgow Outcome Score (r = −0.7) and direct correlation with invasive ICP readings. This study provides further evidence that in patients with intracranial hemorrhage and SAH, the presence of ONSD greater than a threshold of 5.5 mm is significantly predictive of invasively measured elevated ICP. The prediction of raised ICP can be further refined by measuring ONSD at the point where the optic nerve and the ophthalmic artery cross, and by determining the ratio between the ONSD and ETD.