Poor correlation between head circumference and cranial ultrasound findings in premature infants with intraventricular hemorrhage

Object: Intraventricular hemorrhage (IVH) is the most common cause of hydrocephalus in the pediatric population and is particularly common in preterm infants. The decision to place a ventriculoperitoneal shunt or ventricular access device is based on physical examination findings and radiographic imaging. The authors undertook this study to determine if head circumference (HC) measurements correlated with the Evans ratio (ER) and if changes in ventricular size could be detected by HC measurements.

Methods: All cranial ultrasound (CUS) reports at the authors' institution between 2008 and 2011 were queried for terms related to hydrocephalus and IVH, from which a patient cohort was determined. A review of radiology reports, HC measurements, operative interventions, and significant clinical events was performed for each patient in the study. Additional radiographic measurements, such as an ER, were calculated by the authors. Significance was set at a statistical threshold of p < 0.05 for this study.

Results: One hundred forty-four patients were studied, of which 45 (31%) underwent CSF diversion. The mean gestational age and birth weight did not differ between patients who did and those who did not undergo CSF diversion. The CSF diversion procedures were reserved almost entirely for patients with IVH categorized as Grade III or IV. Both initial ER and HC were significantly larger for patients who underwent CSF diversion. The average ER and HC at presentation were 0.59 and 28.2 cm, respectively, for patients undergoing CSF diversion, and 0.34 and 25.2 cm for those who did not undergo CSF diversion. There was poor correlation between ER and HC measurements regardless of gestational age (r = 0.13). Additionally, increasing HC was not found to correlate with increasing ERs on consecutive CUSs (φ = -0.01, p = 0.90). Patients who underwent CSF diversion after being followed with multiple CUSs (10 of 45 patients) presented with smaller ERs and HC than those who underwent CSF diversion after a single CUS. Just prior to CSF diversion surgery, the patients who received multiple CUSs had ERs, but not HC measurements, that were similar to those in patients who underwent CSF diversion after a single CUS.

Conclusions: The HC measurement does not correlate with the ER or with changes in ER and therefore does not appear to be an adequate surrogate for serial CUSs. In patients who are followed for longer periods of time before CSF shunting procedures, the ER may play a larger role in the decision to proceed with surgery. Clinicians should be aware that the ER and HC are not surrogates for one another and may reflect different pathological processes. Future studies that take into account other physical examination findings and long-term clinical outcomes will aid in developing standardized protocols for evaluating preterm infants for ventriculoperitoneal shunt or ventricular access device placement.