Study of Normal Values of Evan’s Index on Brain CT Scan in Individuals attending Nepal Medical College Teaching Hospital, Kathmandu, Nepal

Ventriculographic indices are obtained by using Evan’s Index. Evan’s Index is a ratio which compares the maximum width of the frontal horns of the lateral ventricle to the maximum transverse diameter of the inner table of the skull and serves as an indirect marker of ventricular volume. Evan’s Index has been extensively used in the diagnosis of idiopathic normal pressure hydrocephalus, in the assessment of outcome of patients having shunt placement which is the primary mode of treatment. This study was aimed to find out the normal values of Evan’s Index on brain CT scan in individuals attending Nepal medical college teaching hospital, Kathmandu, Nepal. A total of 500 individuals CT (250 males and 250 females) were finally selected. The ages were ranged between 5 to 80 years old. The mean Evan’s Index in the studied population was 0.253 ± 0.037 in males, 0.250 ± 0.034 in the females and an overall mean of 0.251 ± 0.035. There was no significant statistical difference in the Evans ratio between male and females (P = 0.274). This study shows that Evan’s Index was higher in individuals who were 60 years and above in both males and females. The very small standard deviations appreciated in the result suggest that Evan’s index can be calculated fairly accurately.