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.

Various methodologies to assess cerebral autoregulation (CA) have been developed, including model - based methods (e.g. autoregulation index, ARI), correlation coefficient - based methods (e.g. mean flow index, Mx), and frequency domain - based methods (e.g. transfer function analysis, TF). Our understanding of relationships among CA indices remains limited, partly due to disagreement of different studies by using real physiological signals, which introduce confounding factors. The influence of exogenous noise on CA parameters needs further investigation. Using a set of artificial cerebral blood flow velocities (CBFV) generated from a well-known CA model, this study aims to cross-validate the relationship among CA indices in a more controlled environment. Real arterial blood pressure (ABP) measurements from 34 traumatic brain injury patients were applied to create artificial CBFVs. Each ABP recording was used to create 10 CBFVs corresponding to 10 CA levels (ARI from 0 to 9). Mx, TF phase, gain and coherence in low frequency (LF) and very low frequency (VLF) were calculated. The influence of exogenous noise was investigated by adding three levels of colored noise to the artificial CBFVs. The result showed a significant negative relationship between Mx and ARI (r = −0.95, p < 0.001), and it became almost purely linear when ARI is between 3 to 6. For transfer function parameters, ARI positively related with phase (r = 0.99 at VLF and 0.93 at LF, p < 0.001) and negatively related with gain_VLF(r = −0.98, p < 0.001). Exogenous noise changed the actual values of the CA parameters and increased the standard deviation. Our results show that different methods can lead to poor correlation between some of the autoregulation parameters even under well controlled situations, undisturbed by unknown confounding factors. They also highlighted the importance of exogenous noise, showing that even the same CA value might correspond to different CA levels under different ‘noise’ conditions.

Purpose: To determine the outcome of ventriculo-peritoneal shunts as a treatment for idiopathic intracranial hypertension (IIH) Materials and Methods: Retrospective case series of 28 patients with IIH and evidence of raised intracranial pressure (ICP) who underwent shunt insertion. Patients were identified from a prospectively updated operative database. A case-notes review was performed and data on type of shunt, pre- and post-operative symptoms, ophthalmological findings and post-operative complications were recorded. Results: All patients had symptoms of IIH that had failed medical management. Twelve patients had previous lumbo-peritoneal shunts and 2 patients had previous venous sinus stents. All patients had evidence of raised ICP as papilloedema and raised CSF pressure on lumbar puncture. Twenty-seven patients received a ventriculo-peritoneal shunt and 1 patient a ventriculo-atrial shunt. Twenty-six patients received Orbis Sigma Valves and 2 patients Strata valves. At follow-up all patients (100%) had improvement/resolution of papilloedema, 93% had improved visual acuity and 84% had improved headaches. Mean time to last follow-up was 15 (range 4–96) months. Complications occurred in 3 patients (11%): 2 patients required revision of their peritoneal catheters and 1 patient had an anti-siphon device inserted. Conclusions: Previous literature reported a ventricular shunt revision rate of 22–42% in the management of IIH. We demonstrate ventriculo-peritoneal shunts to be an effective treatment with a revision rate of 11% compared to the previously reported 22–42%.

Objective: Pseudotumour cerebri syndrome (PTCS including idiopathic intracranial hypertension) is characterised by the symptoms and signs of raised cerebrospinal fluid pressure (CSFp) in the absence of ventricular dilatation or an intracranial mass lesion. Its aetiology is unknown in the majority of cases but there is much evidence for impaired CSF absorption. Traditionally, sagittal sinus pressure has been considered to be independent of CSF pressure in adults. However, the discovery of stenoses of intracranial venous sinuses and introduction of venous sinus stenting has highlighted the importance of the venous drainage in PTCS. In this study, we have explored the relationship between CSFp and SSp before and during a CSF infusion test and during CSF drainage. Materials and methods: Ten patients (9 females:1 male) with PTCS underwent infusion studies in parallel with direct retrograde cerebral venography. Both SSp and CSFp were recorded at a baseline and during CSFp elevation in a course of a CSF infusion test. The drainage of CSF after the CSF infusion was performed in 7 patients. In 5 cases, jugular venous pressure was also measured. Results: CSFp and SSp including their amplitudes correlated significantly and strongly both at baseline (R = 0.96; p = 0.001) and during infusion (R = 0.92; p = 0.0026). During drainage, this correlation was maintained until SSp reached a stable value, whereas CSFp continued to decrease. Conclusions: In this series of ten patients with PTCS, CSFp and SSp were coupled, both at baseline and during infusion. The implications of such coupling for the calculation of CSF outflow resistance are discussed.

OBJECTIVE: Normal pressure hydrocephalus is not simply the result of a disturbance in CSF circulation, but often includes cardiovascular comorbidity and abnormalities within the cerebral mantle. In this study, the authors have examined the relationship between the global autoregulation pressure reactivity index (PRx), the profile of disturbed CSF circulation and pressure-volume compensation, and their possible effects on outcome after surgery.METHODS: The authors studied a cohort of 131 patients in whom a clinical suspicion of normal pressure hydrocephalus was investigated. Parameters describing CSF compensation and circulation were calculated during the CSF infusion test, and PRx was calculated from CSF pressure and mean arterial blood pressure (MAP) recordings. A simple scale was used to mark the patients’ outcome 6 months after surgery (improvement, temporary improvement, and no improvement).RESULTS: The PRx was negatively correlated with resistance to CSF outflow (R = −0.18; p = 0.044); patients with normal CSF circulation tended to have worse autoregulation. The correlation for patients who were surgically treated (n = 83) was R = −0.28; p = 0.01, and it was stronger in patients who experienced sustained improvement after surgery (n = 48, R = −0.43; p = 0.002). In patients who did not improve, the correlation was not significantly different from zero (n = 19, R = −0.07; p = 0.97). There was a trend toward higher values for PRx in nonresponders than in responders (0.16 ± 0.04 vs 0.09 ± 0.02, respectively; p = 0.061), associated with higher MAP values (107.2 ± 8.2 in nonresponders vs 89.5 ± 3.5 in responders; p = 0.195). The product of MAP × (1 + PRx), which was proposed as a measure of combined arterial hypertension and deranged autoregulation, showed a significant association with outcome (greater value in nonresponders; p = 0.013).CONCLUSIONS: Autoregulation proves to associate with CSF circulation and appears strongest in shunt responders. Outcome following CSF diversion is possibly most favorable when CSF outflow resistance is increased and global cerebral autoregulation is intact, in combination with arterial normotension.

Background: Despite the quantitative information derived from testing of the CSF circulation, there is still no consensus on what the best approach could be in defining criteria for shunting and predicting response to CSF diversion in normal pressure hydrocephalus (NPH). Objective: We aimed to review the lessons learned from assessment of CSF dynamics in our center and summarize our findings to date. We have focused on reporting the objective perspective of CSF dynamics testing, without further inferences to individual patient management. Discussion: No single parameter from the CSF infusion study has so far been able to serve as an unquestionable outcome predictor. Resistance to CSF outflow (Rout) is an important biological marker of CSF circulation. It should not, however, be used as a single predictor for improvement after shunting. Testing of CSF dynamics provides information on hydrodynamic properties of the cerebrospinal compartment: the system which is being modified by a shunt. Our experience of nearly 30 years of studying CSF dynamics in patients requiring shunting and/or shunt revision, combined with all the recent progress made in producing evidence on the clinical utility of CSF dynamics, has led to reconsidering the relationship between CSF circulation testing and clinical improvement. Conclusions: Despite many open questions and limitations, testing of CSF dynamics provides unique perspectives for the clinician. We have found value in understanding shunt function and potentially shunt response through shunt testing in vivo. In the absence of infusion tests, further methods that provide a clear description of the pre and post-shunting CSF circulation, and potentially cerebral blood flow, should be developed and adapted to the bed-space.