Intracranial Pressure Monitoring and Lumbar Puncture after Endoscopic Third Ventriculostomy in Children

Abstract

The high ICP observed in a group of patients in the early postoperative days is probably related to the slow permeation of the subarachnoid spaces by the cerebrospinal fluid flowing out of the third ventriculostomy. Management of intracranial hypertension after ETV remains a matter of controversy. The role of the lumbar puncture in the faster normalization of the ICP is examined in this article. By increasing the compliance and the buffering capacities of the spinal subarachnoid spaces, it probably decreases the cerebrospinal fluid outflow resistance from the ventricular system, facilitating the decrease of the ventricular volume and allowing faster permeation of the intracranial subarachnoid spaces. High postoperative ICP can account for persistent symptoms of intracranial hypertension and ventricular dilatation on computed tomographic scans after third ventriculostomy. A cycle of one to three lumbar punctures should always be performed in patients who remain symptomatic and who show increasing ventricular dilatation after ETV, before ETV is assumed to have failed and an extracranial cerebrospinal fluid shunt is implanted.

Childhood hydrocephalus secondary to posterior fossa tumor is both an intra- and extraaxial process

“…Given that the normal pressure drop from the sagittal sinus to the jugular bulb is 4.5 mm Hg in children, 2 even if the average reduction in the size of the sinuses were only 50% from the sagittal sinus to the jugular bulb (the current study measures the maximal stenosis, not the average stenosis), the pressure increase in the sinuses would be 10 mm Hg. This correlates with the findings of Cinalli et al, who found the average initial CSF pressure to be 10 mm Hg higher than normal in children with posterior fossa tumor 6 (CSF pressure correlates directly with sinus pressure in idiopathic intracranial hypertension with venous stenosis 10 ). In a study undertaken in children with hydrocephalus by Shulman and Ransohoff, in the 8 patients with hydrocephalus secondary to benign aqueduct stenosis, the sagittal sinus pressures averaged 16.1 mm Hg and the CSF pressure averaged 13.6 mm Hg.…”

“…In most cases, the ICP values remained normal or normalized after several lumbar punctures. 6 Thus, the length of the adaptation period does not correlate with the opening of the subarachnoid space. In addition, it is hard to conceive how a lumbar puncture could improve the permeability of the pacchionian granulations or the absorption into the subdural space because reducing the CSF pressure should have the opposite effect.…”

“…6 This period of delay has been termed the adaptation period. The cause of the adaptation period has been hypothesized to be progressive reopening of the subarachnoid spaces at the convexity, a slow increase in permeability of the pacchionian granulations, or possibly effusion of the CSF into the spinal subdural space.…”

“…A review of the literature has suggested that the ventricles often remain enlarged in the initial period following surgery even in those who will improve. 6 Due to the delay in improvement in most patients and the complete failure of hydrocephalus amelioration in some patients, endoscopic third ventriculostomy (ETV) has been advocated as a means of bypassing the blockage before tumor surgery. To further characterize the delayed improvement in hydrocephalus following surgery, Cinalli et al monitored CSF pressure following ETV.…”

“…In 29% of the children, there was an initial fall but subsequent rise in pressure, signaling failure of the procedure. 6 This delay in improvement of the CSF pressure following the unblocking of the system has been called the adaptation period. It is thought that obstruction of the ventricular system may somehow cause a secondary reversible obstruction somewhere within the subarachnoid space 15 -i.e., there is an extraaxial component to the intraaxial obstructed hydrocephalus.…”