Cerebrospinal fluid dynamics in non-acute post-traumatic ventriculomegaly

Abstract

Background: Post-traumatic hydrocephalus (PTH) is potentially under-diagnosed and under-treated, generating the need for a more efficient diagnostic tool. We aim to report CSF dynamics of patients with post-traumatic ventriculomegaly.

Materials and methods: We retrospectively analysed post-traumatic brain injury (TBI) patients with ventriculomegaly who had undergone a CSF infusion test. We calculated the resistance to CSF outflow (Rout), AMP (pulse amplitude of intracranial pressure, ICP), dAMP (AMPplateau-AMPbaseline) and compensatory reserve index correlation coefficient between ICP and AMP (RAP). To avoid confounding factors, included patients had to be non-decompressed or with cranioplasty > 1 month previously and Rout > 6 mmHg/min/ml. Compliance was assessed using the elasticity coefficient. We also compared infusion-tested TBI patients selected for shunting versus those not selected for shunting (consultant decision based on clinical and radiological assessment and the infusion results). Finally, we used data from a group of shunted idiopathic Normal Pressure Hydrocephalus (iNPH) patients for comparison.

Results: Group A consisted of 36 patients with post-traumatic ventriculomegaly and Group B of 45 iNPH shunt responders. AMP and dAMP were significantly lower in Group A than B (0.55 ± 0.39 vs 1.02 ± 0.72; p < 0.01 and 1.58 ± 1.21 vs 2.76 ± 1.5; p < 0.01. RAP baseline was not significantly different between the two. Elasticity was higher than the normal limit in all groups (average 0.18 1/ml). Significantly higher Rout was present in those with probable PTH selected for shunting compared with unshunted. Mild/moderate hydrocephalus, ex-vacuo ventriculomegaly/encephalomalacia were inconsistently reported in PTH patients.

Conclusions: Rout and AMP were significantly lower in PTH compared to iNPH and did not always reflect the degree of hydrocephalus or atrophy reported on CT/MRI. Compliance appears reduced in PTH.

Keywords: CSF dynamics; CSF infusion test; Cerebrospinal fluid; Hydrocephalus; Traumatic brain injury; Ventriculomegaly.

Fig. 1

Representative example of CSF dynamics in a patient under investigation for possible Post Traumatic Hydrocephalus. ICP (monitored via Ommaya reservoir in this case) increased briskly after start of infusion, with an Rout around 11–13 mmHg/min/ml. AMP at baseline ~ 1 mmHg, also reacted briskly to infusion until a plateau of 5.6 mmHg. RAP at baseline ~ 0.6, clearly increased to almost 1 after infusion of only a few ml, indicating exhaustion of compensatory reserve. CSFp: CSF pressure (access to the CSF space via LP). AMP: fundamental amplitude of ICP. RAP: compensatory reserve index (moving correlation coefficient between ICP and AMP)