W Lam, WT Fung, V Wong, L Leong

Many studies have concluded that Doppler study of the neonatal cerebral vessels can be used as an adjunct to clinical management in cases with shock, asphyxia, brain death or increased intracranial pressure. However, most studies were done in Caucasian patients. We would like to determine the resistive index (RI) of intracranial arteries in our local population and compare it with values for Caucasians. The resistive indices of the anterior cerebral artery, middle cerebral artery and internal cerebral artery on either side were measured in 318 babies over 3 years. A 7.5 MHz vector transducer (Acuson XP/10 ART) was used. The age ranged from newborn to 1.5 years, including premature and term babies. The resistive index of 219 cases of term and premature babies with normal US findings were analysed according to age. The average resistive indices of the anterior cerebral artery, middle cerebral artery and internal cerebral artery were 68 ± 10.5, 72.5 ± 9.6 and 72.5 ± 9.6, respectively; they were inversely related to the age. The resistive index of 99 cases with abnormal ultrasound findings, including hydrocephalus, convulsion, post- meningitis and abnormal intraventricular echogenicity were analysed. The average resistive index of 53 cases of dilated ventricles, 19 cases of post-meningitis and 19 cases of convulsion showed no significant deviation from the normal values. In cases of previous intraventricular haemorrhage, the increase in resistive index values correlated with the severity of dilated ventricles and haemorrhage. Five cases showed dilated ventricle on the first scan and were found to have increased ventricular size as well as elevated resistive index on follow-up scan(s). In 25 cases of asphyxia, the resistive index values were either higher or lower than our normal range. In conclusion, the measured resistive index values in normal infants in our locality were slightly lower than those in Caucasians, but the pattern of changes of resistive index were similar to those in Caucasians. As decreased resistive index in cases of asphyxia may have significant prognostic values, and increased resistive index in hydrocephalus may need intervention, the resistive index values in our study may serve as a reference for further patient management.