Intracranial pressure monitoring in craniosynostosis

The incidence of raised ICP is low (approximately 17%) in single suture synostosis and is seen more frequently in midline sutures, namely, sagittal and metopic.^[1] It has been reported to be 15–20% in multisutural (non-syndromic) going up to 30–40% in syndromic craniosynostosis.^[2] The cause of raised ICP in craniosynostosis is obviously the smaller cranial volume. In addition, venous congestion due to anomalous venous drainage, hydrocephalus, and upper airway obstruction also contribute.

The need for ICP Monitoring in craniosynostosis cases depends on the following factors:

1. Clinical parameters may be unreliable. Tuite et al. studied ICP and ophthalmoscopic findings prospectively in 122 pts. Papilloedema had high sensitivity (87% pts with Papilloedema had ICP>15 mm Hg) but low specificity (68% pts with ICP> 15 did not have papilloedema). Papilloedema was 100% sensitive in children older than 8 years old but only 22% in younger subjects.^[1]

   Eide et al. in two large series of pediatric patients with craniosynostosis, hydrocephalus, shunt failure, or idiopathic ICP found that symptoms classically associated with raised ICP (headache, irritability, sleep disturbance, nausea, psychomotor delay, and seizures) did not correlate with or predict raised ICP in children.^[3] The Oxford group had similar inferences in 284 patients with sagittal craniosynostosis.^[4]

2. Radiology parameters can also be unreliable. Copper beaten appearance is common in craniosynostosis and its incidence increases with age, therefore, unreliable as a sign of raised ICP.^[5]

3. Electrophysiological parameters such as VEPs hold promise but the high incidence of abnormal responses in craniosynostosis children and its variability is well known in normal subjects.^[6]

   Indications for ICP monitoring in craniosynostosis may be categorized as below:

   1. When a non-operative line of management is proposed: The Oxford group recommends using it in all cases of sagittal craniosynostosis irrespective of the severity of the deformity as the incidence of raised ICP is almost 44%^[4]

   2. Delayed diagnosis of Craniosynostosis: Scott and colleagues (2009) reported alleviation of symptoms after vault expansion was done in response to raised ICP in their cohort of children older than 2 years.^[7] Iyengar et al. reported a similar experience in a 17 years old, where invasive intraparenchymal monitoring was used to make the decision for vault expansion.^[8]

   3. To choose between a posterior expansive cranioplasty versus anterior frontal-orbital advancement: Tamburrini reported the use of ICP values to devise a surgical plan for their patients with craniosynostosis. Out of 12 children with syndromic craniosynostosis, 11 had abnormal ICP values. Two out of the 11 had relatively low ICP values and only underwent an anterior bifrontal-orbital advancement as a delayed definitive procedure. The remaining nine underwent an early occipital expansive cranioplasty followed by multiple procedures including, namely, VP shunt before definitive bifrontal-orbital advancement.^[2]

   4. Post-operative evaluation of operated patients. As clinical and radiological parameters are not reliable, ICP monitoring can be employed for the early detection of raised ICP to prevent irreversible changes. Christian et al. did a meta-analysis of seven studies that employed invasive ICP monitoring postoperatively after various remodeling procedures. Intracranial hypertension (IH) was reported to be present in 5% of patients postoperatively with sagittal synostosis and 4% of patients with all forms of non-syndromic craniosynostosis. Cranial remodeling procedures without orbital involvement (including strip craniectomies) were compared to craniofacial procedures that included advancement of the orbital rim. The incidence of IH was found to be 5% in cranial remodeling procedures versus 1% in craniofacial procedures.^[9]