The utility of CT optic nerve sheath diameter in patients with traumatic brain injury referred to Muhimbili National Hospital

Abstract

Traumatic brain injury is a major public health problem in Tanzania and indeed worldwide. Many concerns that arise from different research are that neurological damage from Traumatic Brain Injury does not occur at the moment of injury but occurs after hours and day’s 1.The rise in Intracranial Pressure is considered an integral part in the pathophysiology of traumatic brain injury. ICP monitoring is crucial in management of TBI 2, 3.Recent cranial Computed Tomography scan studies have shown relationship between CT Optic Nerve Sheath Diameter and Intracranial Pressure 4,5,6,7. Various non invasive methods have been used to measure signs of raised ICP like fundoscopy and ocular ultrasound of which the results are operator dependent 8,9,10. To date little is known in this study area in our community. This study wasassessing the utility of CT scan Optic Nerve Sheath Diameter as a measure of raised intracranial pressure in patients with TBI and the findings will help the clinicians in the triaging patients at risk of having raised ICP. Broad objective To determine utility of CT Optic Nerve Sheath Diameter in patients with Traumatic Brain Injury referred to CT unit Muhimbili National Hospital from June 2016 to December 2016. Methodology This was a prospective Hospital based Cross sectional study which was conducted at Radiology department, Muhimbili National Hospital from June to December 2016 among head injury patients referred to CT scan unit.Structured questionnaire were used for recording patient’s demographics, clinical information and Brain CT scan findings. Finally, a systematic dataanalysis was done and Statistical Association was done by using cross tabulations; Chi-square test was used to compare proportions. P value of < 0.05 was considered statistically significant.

Results Two hundred and twelve patients with traumatic brain injury whom underwent head CT scan were included in this study, in which 175(82.5%) were male and 37(17.5%) were female. The participants mean age was 33.26 years with range of 18-76 years and standard deviation of 11.7. This study shows that patients with abnormal ONSD were 83 (39.2%) with mean ONSD of 0.6cm and mean GCS of 12 respectively which was statistically significant P=0.0011. Cutoff value of > 0.57cm was used. Sixty percent of patients with linear and depressed fractures significantly contributed more to the traumatic brain injuries and abnormal ONSD [P=0.0001 each].The secondary complications of traumatic brain injury like brain edema,midline shift, effacement of cistern and ventricles were all significantlyrelated to abnormal ONSD with the Pvalue of <0.001. There was strong relationship [P=0.0001] between GCS and ONSD among TBI patients where bymore than 60% of patients with severe and moderate TBI had abnormal ONSD. Conclusion Based on these study findings there is strong relationship between Glasgow Coma Scale and CT Optic Nerve Sheath Diameter in patients with Traumatic Brain Injury. Patients with moderate and severe TBI have higher ONSD measurements than mild TBI patients. In a limited setting CT ONSD obtained from initial scan can be used in triaging patients at risk of having raised ICP. ONSD measurement is indicated in patients with moderate and severe TBI than mild TBI.