ESTABLISHING THE OPTIC NERVE SHEET DIAMETER (ONSD) CUT–OFF FOR DIAGNOSIS OF RAISED INTRACRANIAL PRESSURE (RICP) AT LAFIA, NORTH-CENTRAL NIGERIA USING OCULAR ULTRASONOGRAPHY
Dr. Annongu I. T., Mohammad H., Chaha K., Magaji O. G. and Bulus P. U.
ABSTRACT
Objective: Certain clinical conditions are associated with Raised intracranial pressure (RICP). Early diagnosis and timely intervention is crucial to prevent secondary brain damage and death. Optic nerve sheath diameter (ONSD) measurement by ultrasound is increasingly used to detect RICP. Knowledge of normal ONSD in a healthy population is essential to interpret this measurement. Aim: To evaluate normal optic nerve sheath diameter in Lafia, north central Nigeria. Methodology: 156 healthy volunteers 15 years and above were used in this study. The ONSD was measured at 3 mm posterior to the globe using a 7.5 MHz linear transducer placed on the superior and lateral aspect of the orbit against the upper eyelid with the eye closed. Result: The study consist of 75 males and 81 females with mean age of 34.6 ± 1.5 years. The median and mean ONSD for both eyes were 4.50mm and 4.48 ± 0.05mm respectively with a range 3.20-6.00mm. On the right, the median and mean ONSD values were 4.50mm and 4.48 ±0.52 respectively with a range of 3.20–6.00 mm, while the median and the mean left ONSD were 4.50 mm and 4.47 ± 0.49mm respectively with a range of 3.50–6.00 mm. No statistically significant variation in ONSD was found between the right and left sides (P = 0.85) and also between male and female participants (P = 0.10 and 0.13 right and left respectively). Conclusion: ONSD mean value of 4.48mm has been obtained here in Lafia, north central Nigeria with no significant correlation with age and sex, height, weight and BMI. Values above 6mm with clinical suspicion could therefore be adopted for diagnosis and management as cases of RICP.
Keywords: ONSD, RICP, Nigeria, Ocular Ultrasonography.
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