TO THE EDITOR: We read with interest and concern the paper by Wall et al.7 summarizing their finding of intracranial pressure (ICP) monitoring in patients with radiological sagittal suture synostosis who had presented for unrelated reasons in early childhood (Wall SA, Thomas GPL, Johnson D, et al: The preoperative incidence of raised intracranial pressure in nonsyndromic sagittal craniosynostosis is underestimated in the literature. J Neurosurg Pediatr 14:674–681, December 2014). Of the 39 patients, 17 were found to have “raised ICP” and were subjected to calvarial remodeling based solely on the fact that the ICP number was high without establishing the relationship of high ICP to any symptoms.
In our review of the literature, we have not found any controlled studies investigating ranges of normal and high ICP in pediatric patients. We believe that the generally used reference ranges for pediatric ICP may be from numbers mentioned in publications by R. A. Minns6 in the 1980s, without studies backing them up. Furthermore, critical ICPs cannot be deduced from pressure readings alone. Cerebral perfusion pressure (CPP) is also an important parameter. Since there is no clearly defined measure of high ICP in the literature, in this article the authors chose to define raised ICP as ICP persistently higher than 15 mm Hg or the presence of 3 B waves in a 24-hour period. This is referenced to a review written by the senior author (P.R.) himself,8 which is then referenced to articles by Lundberg et al. from the early 1960s.3–5
These articles were from the pre-CT era and report on adult patients who had clear clinical symptoms of increased ICP unlike those in the series reported by Wall et al. In fact, Lundberg et al.3 state at the beginning of Chapter 12 of their thesis on normal ventricular fluid pressure that “Since the main indications for continuous VFP [ventricular fluid pressure] control were a space occupying lesion and intracranial hypertension, the present series does not include any cases that can with certainty be regarded as normal in respect of central nervous system. One case, where the VFP was recorded graphically can, however, be regarded as probably representative of a normal VFP.” While these papers gave us a significantly improved understanding of the patterns of ICP waveforms in symptomatic adult patients with raised ICP along with clinical symptoms and intracranial lesions, these data cannot be extrapolated to the asymptomatic pediatric patients with no intracranial pathology on whom Wall et al. report in their series.
It is well known that B waves occur in healthy individuals. Most of the work defining criteria for what constitutes pathological B waves has been done on symptomatic adult patients with normal-pressure hydrocephalus, shunt-treated hydrocephalus, or head injuries. While there continues to be some controversy as to what constitutes abnormal B waves in symptomatic adults, the authors have not given adequate justification by means of appropriate references for considering the presence of 3 or more B waves in a 24-hour period to be abnormal. Six of their patients had ICPs of 15 mm Hg or less but were subjected to a major cranial vault reconstruction based on the undefined criterion of B waves. Subjecting asymptomatic children without papilledema to a major cranial vault reconstruction without a scientific basis does not seem justifiable.
Increased ICP can cause problems in a number of ways. Focally raised pressure in its extreme form may lead to brainstem herniation and death. Increased ICP can stretch and distort sensitive basal or tentorial dura mater and cause symptoms such as headaches or vomiting from distortion of the brainstem. Increased pressure can lead to progressive papilledema and vision loss. Finally, high ICP from hydrocephalus or a normal ICP with increased brain compliance in normal-pressure hydrocephalus can distort periventricular fibers, which can result in symptoms observed in those patient populations. In patients with all of these conditions, we strongly feel that surgical intervention is required. However, none of the patients that Wall et al. present in their series had these problems, and in our opinion surgery may not have been necessary (except in the patients with significant scaphocephaly, in whom the surgery is justifiable for cosmetic reasons).
Understandably, very high ICP beyond the autoregulation capacity of the brain can compromise cerebral perfusion. In adults this generally does not happen until the pressure reaches a threshold of about 40 mm Hg. Even so, some patients with pseudotumor cerebri and ICPs in this range can function normally with no symptoms other than headaches. In children with severe traumatic brain injury, an ICP greater than 20 mm Hg and a CPP of less than 40 mm Hg has been recommended as a threshold for instituting treatment (Level III recommendation).2 As the authors rightly pointed out, if this ICP criterion were to be used, only 4 of the 39 patients would qualify as having elevated ICP. Of these 4 patients, only one was developmentally delayed and none of them were symptomatic or had papilledema. Does the mere presence of increased pressure in an asymptomatic patient without papilledema justify a major cranial vault expansion?
Presumably, chronically altered cerebral perfusion in a developing brain may have consequences such as developmental or psychomotor retardation. Wall et al. have used this as a leaning post to justify surgery in their patients. However, their own data do not support this. They very clearly state in their paper that the “high ICP” had no relationship to the patients’ presenting symptoms or developmental delay in their patient population. They further establish by way of references that there is no evidence to support improvement in neurodevelopment outcomes after corrective surgery.
The first tenet of medicine is “to do no harm.” Six of the 18 patients became symptomatic (4 of 14 who were asymptomatic developed symptoms) or remained symptomatic (2 of 4 who were symptomatic remained symptomatic after surgery) after the calvarial reconstruction. One patient, in fact, had a decline in academic performance after surgery. Wall et al. take refuge in the fact that their patients’ ICPs had normalized and, therefore, ignore the consequences. Nevertheless, in our opinion the surgery did more harm to these patients, and the good that Wall et al. intended is not reflected in any of the results.
Understandably, the Oxford craniofacial group is exploring reasons, other than for cosmesis, to justify surgery in patients with sagittal craniosynostosis. A previous publication from the Leeds craniofacial service seemed to suggest that at 5 years of age (mean age 64.9 months) patients who have undergone surgery in infancy do better in motoric function compared to the results of preoperative assessment at a mean age of 7.4 months.1 The unbalanced comparison was made to patients who did not undergo surgery, were a year and a half younger (mean age 42.9 months), and had an initial assessment at mean age of 15 months. Not surprisingly the p value was significant in the surgically treated group. Numerous other papers show conflicting results. If surgery were to be so successful in improving the neurocognitive outcome, we are certain that studies would have shown a definitive outcome. Wall et al. have acknowledged this controversy and appropriately referred to it in their article.
While we are not opposed to the authors’ presenting their data, we certainly take objection to their suggestion that asymptomatic patients with mild or no scaphocephaly with sagittal craniosynostosis and no papilledema be subjected to a major cranial vault reconstruction without there being any objective evidence of its benefits. Our main concern is that aggressive surgeons will misquote this article in their own defense at conferences and in publications for years to come.
References
- 1↑
Bellew M, , Liddington M, , Chumas P, & Russell J: Preoperative and postoperative developmental attainment in patients with sagittal synostosis: 5-year follow-up. J Neurosurg Pediatr 7:121–126, 2011
- 2↑
Kochanek PM, , Carney N, , Adelson PD, , Ashwal S, , Bell MJ, & Bratton S, et al.: Guidelines for the acute medical management of severe traumatic brain injury in infants, children, and adolescents-second edition. Pediatr Crit Care Med 13:Suppl 1 S1–82, 2012
- 3↑
Lundberg N: Continuous recording and control of ventricular fluid pressure in neurosurgical practice. Acta Psychiatr Scand Suppl 36:1–193, 1960
- 4
Lundberg N, , Troupp H, & Lorin H: Continuous recording of the ventricular-fluid pressure in patients with severe acute traumatic brain injury. A preliminary report J Neurosurg 22:581–590, 1965
- 5
Lundberg N, & West KA: Leakage as a source of error in measurement of the cerebrospinal fluid pressure by lumbar puncture. Acta Neurol Scand Suppl 13:115–121, 1965
- 7↑
Wall SA, , Thomas GPL, , Johnson D, , Byren JC, , Jayamohan J, & Magdum SA, et al.: The preoperative incidence of raised intracranial pressure in nonsyndromic sagittal craniosynostosis is underestimated in the literature. J Neurosurg Pediatr 14:674–681, 2014
- 8↑
Wiegand C, & Richards P: Measurement of intracranial pressure in children: a critical review of current methods. Dev Med Child Neurol 49:935–941, 2007
