Assessment of Continuous Intracranial Pressure Recordings in Childhood Craniosynostosis

Abstract

In this study, we explored two strategies of assessing continuous intracranial pressure (ICP) recordings in children with craniosynostosis, namely either by computation of the mean ICP or by computation of the accurate numbers of ICP elevations of different durations. The ICP recordings of 121 consecutive patients with a tentative diagnosis of craniosynostosis who underwent continuous ICP monitoring were examined. The relationship between mean ICP and numbers of ICP elevations was defined. The distribution of numbers of ICP elevations between patients either undergoing surgery or conservative treatment was also compared, since the choice of treatment was heavily dependent on the results of ICP monitoring. At the time of ICP monitoring, calculation of mean ICP was the main parameter for assessment of ICP curves. After a median observation period of 16 months, the ICP curves were reexamined by means of the software Sensometrics^TM Pressure Analyser, which presents the ICP curve as a matrix of numbers of ICP elevations of different levels (20–40 mm Hg) and durations (0.5– 20 min). Since the recording period differed between the cases, the numbers were standardized to a given recording time of 10 h, to allow for comparisons between patients. Cases with a borderline mean ICP during sleep (mean ICP 10–15 mm Hg) constituted 40.5% of the 121 patients. In this group, a rather weak relationship between mean ICP and the number of ICP elevations above 20 mm Hg was found, as well as a relatively high number of ICP elevations above 20 mm Hg of various durations. As compared to the patients undergoing surgery, a rather high number of ICP elevations above 20 mm Hg of various durations was found in patients undergoing conservative treatment. The study confirmed our hypothesis that in children with craniosynostosis, calculation of mean ICP does not describe the ICP curve in a reliable way. Decision-making should also include the computation of the distribution of numbers of ICP elevations, since this procedure represents a more sensitive strategy of detecting intracranial hypertension.

The incidence of raised intracranial pressure in nonsyndromic sagittal craniosynostosis following primary surgery

“…Although this method requires a general anesthetic for probe placement, it has consistently proved to be a highly reliable and reproducible method of assessing ICP, with only an infrequent and minor complication rate associated with it. 11,22,33,50 In this patient series, the only significant complication was probe malfunction, necessitating a repeat procedure. Our use of a threshold of more than 15 mm Hg to define an abnormally elevated ICP is consistent with that used by all previous studies that have undertaken overnight intracranial ICP monitoring in craniosynostosis, no matter whether an extradural or subdural device was employed.…”

“…Our use of a threshold of more than 15 mm Hg to define an abnormally elevated ICP is consistent with that used by all previous studies that have undertaken overnight intracranial ICP monitoring in craniosynostosis, no matter whether an extradural or subdural device was employed. 6,11,13,28,35,42,43,45,46 The pathological significance of multiple B-type waves is also well recognized in the literature. 11,35,50 Consistent with the patient series of van Veelan et al and Cetas et al, we found that elevated ICP was diagnosed late, at least 2 years after primary surgery, with a mean at just under 4.5 years of follow-up.…”

“…6,11,13,28,35,42,43,45,46 The pathological significance of multiple B-type waves is also well recognized in the literature. 11,35,50 Consistent with the patient series of van Veelan et al and Cetas et al, we found that elevated ICP was diagnosed late, at least 2 years after primary surgery, with a mean at just under 4.5 years of follow-up. 8,47 This interval, along with the findings that only 1 patient had papilledema and that 4 children developed raised ICP on re-monitoring after a proven normal ICP, strongly suggests that the pathological rise in ICP we observed occurred after primary surgery.…”

“…Eide and colleagues, in a large series of 121 children, reported that there was little correlation between particular clinical symptoms and an abnormal ICP. 11 We suspect that this is because the typical symptoms of elevated ICP, including headaches and irritability, have a number of potential causes in children with craniosynostosis, and are therefore poorly specific. Likewise, although a beaten-copper appearance of the calvaria on radiological imaging has long been associated with raised ICP, it is common following surgery for SC, and increases in incidence with patient age.…”

“…1,24,32,47 Because the clinical symptoms and signs and radiological findings typically associated with intracranial hypertension are not reliable indicators of its presence in craniosynostosis, it is probable that the true incidence of postoperative raised ICP in SC is underestimated. 11,45,46 It is also unclear as to whether the rates of postoperative intracranial hypertension reported in the literature are specific to the surgical procedure used or are dependent on other factors.…”