The Change of the Optic Nerve Sheath Diameter (ONSD) Following Treatment in Patients with Increased ICP

ABSTRACT

PURPOSE: Many reports have shown that the optic nerve sheath diameter (ONSD) can be measured easily by ultrasonography, and that it becomes wider when the intra-cranial pressure (ICP) is increased. However, there have been no reports comparing the two ONSDs following proper treatment. We measured the 2nd ONSDs of patients who were diagnosed with intra-cranial hemorrhage and increased ICP and who were admitted to an intensive care unit following management of their conditions, and analyzed the changes of the ONSDs and their relationship to the outcomes. METHODS: During the 10 months beginning December 1, 2004, we recruited 29 patients who were suspected to have increased ICP as indicated by computed tomography at the emergency center. Meeting any one of the following criteria was defined as elevated ICP mid-line shifting of 3 mm or greater due to mass effect; a collapsed 3rd ventricle; hydrocephalus; effacement of sulci with significant edema; abnormal mesencephalic cisterns. We determined initial ONSDs by ultraonography and the Glasgow Coma Scale (GCS). At the 7th hospital day, GCS and ONSDs were re-evaluated and compared against the previous data. RESULTS: 29 patients (21 male, 8 female, average age 55.55 years) were enrolled. Mean GCS at the admission was 7.86+/-3.60. 18 patients had spontaneous hemorrhage (62%) and 11 patients had traumatic hemorrhage (38%). 22 patients received emergency surgery, 18 patients (62%) showed improved neurological outcomes and 11 (38%) failed to achieve any good outcomes. The initial mean ONSD was 5.41+/-0.70 mm. The average ONSD for traumatic hemorrhage (5.51+/-0.45 mm) was not statistically different from the ONSD for non-traumatic hemorrhage (5.35+/-0.84 mm) (p=0.55). The mean ONSD after 7 days of admission was 4.41+/-0.53 mm, which represented a significant decrease compared with the initial measurements (p<0.05). The mean GCS and ONSD showed significant differences between the improved group and the nonimproved group (GCS 13.44+/-2.15, 3.82+/-3.82 respectively; and ONSD 4.13+/-0.40 mm, 4.86+/-0.37 mm respectively; p<0.05). CONCLUSION: Among the patients with increased ICP, the ONSDs who progressed to good neurological outcomes after treatment had a significantly smaller diameter than those of the others. Through measurement of the ONSDs using ultrasonography, we could not only predict increased ICP but also determine the correlation between a patient's ICP and clinical course.