Role of optic nerve ultrasonography in the diagnosis of elevated intracranial pressure

Objective

In the evaluation of the emergency patients with elevated intracranial pressure (EICP) due to traumatic or nontraumatic causes, optic nerve ultrasonography (ONUS) has been researched in terms of convenience and utility.

Method

Patients who visited the University of Selcuk, Meram Medical Faculty, Department of Emergency Medicine with traumatic or nontraumatic EICP were put through the study. Among these patients, 28 patients with EICP in their cranial computed tomography (CCT) and a control group of 26 patients with no disease had the vertical and horizontal diameters of the optic nerves of both of their eyes measured by ultrasonography. The measurements were done by wetting the closed eyelids and using the 7.5-MHz linear probe placed in a bag that was full of gel. In the statistical research carried out between these two groups (t test), it was found that P < 0.001. Also, the concordance among all the measurements made in the study was examined within the frame of the 'Concordance Correlation Coefficient' formula. Five of the six values found were over 0.90, and one of them just below 0.90; these results were a sign of support for concordance among the measurements.

Results

In the study, the horizontal and vertical diameter measurements of both ONs of the 54 patients were done and then averaged. The mean ON diameter for the 28 patients in the study group was found as 6.4 ± 0.7 mm, and the mean ON diameter for the control group was 4.6 ± 0.3 mm. The ON diameter of all the control group was evaluated as normal, whereas the ON diameter of all the patients with brain edema in their CCT was raised.

Conclusion

In detecting and following up the EICP cases such as cerebrovascular accident and trauma, ONUS is a method that is quite practical, risk free, of low cost, convenient and also reliable if done by experts. For the unconscious patients with no diagnosis, ONUS would be very helpful in eliminating an EICP cause and in leading these patients to CCT. In the case of EICP, the first finding is the dilation in the ON diameter, and with this feature it may be more useful, perhaps not in diagnosing, but in detecting EICP, than CCT. In the cases where CCT is not available, the use of ONUS would help lead the diagnosis and treatment of the patients.