A physical framework for implementing virtual models of intracranial pressure and cerebrospinal fluid dynamics in hydrocephalus shunt testing

A preliminary exploration of acute intracranial pressure-cerebrospinal fluid production relationships in experimental hydrocephalus

CONTEXT

By occluding the fourth ventricle simultaneously obtaining telemetric data on intracranial pressure (ICP) and cerebrospinal fluid (CSF) production, the authors of this study investigate a variety of physiologic parameters in cases of experimental hydrocephalus.

AIMS

The aim of this study is to provide a new context on the disrupted homeostasis in hydrocephalus and guide toward improved treatment based on multiple physiological parameters.

MATERIALS AND METHODS

Hydrocephalus was induced in ten 21-day-old Sprague-Dawley rats by blocking the flow of CSF to the fourth ventricle with kaolin. Ten days post induction, when physical signs of ventriculomegaly reached Evan's ratio (ER) of ≥0.46, CSF flow and ICP were measured while manipulating body position (0°, 45°, 90°) and heart rate.

RESULTS

In hydrocephalic animals (ER ≥0.46), we found a near-steady average acute ICP (13.638 ± 2.331) compared to age-matched controls (ER <0.30) (13.068 ± 8.781), whose ICP fluctuated with the position. Hydrocephalic and controls exhibited an insignificant degree of parabolic shifts in CSF production when body position was changed from prone to 90° and again when moved back to the prone position, a trend more noteworthy in controls (P = 0.1322 and 0.2772). A Pearson's Correlation found CSF production and ICP to be correlated at baseline 0° posture (P = 0.05) in the control group, but not the hydrocephalic group. Weight appeared to play a role when animals were held at 90°. No significant changes in ICP or CSF flow patterns were observed when the heart rate was increased within either group.

CONCLUSIONS

These preliminary findings suggest that our standard assumptions of posture-dependent changes in ICP created using data from physiologic data may be inaccurate in the hydrocephalic patient, and thus describe a need to further explore these relationships.

Complications in Patients Undergoing Microsurgical Clipping of Intracranial Aneurysms with Pre-existing Ventriculoperitoneal Shunts Following a Cranial Procedure

INTRODUCTION

Patients with ventriculoperitoneal/pleural (VP) shunts occasionally must undergo subsequent craniotomy, craniectomy, or cranioplasty. Due to changes in pressure dynamics following shunt placement, we hypothesized that such patients may have an increased risk of developing symptomatic collections of extra-axial blood, fluid, and/or air postoperatively, leading to longer stays and worse outcomes compared to those undergoing cranial operations without a VP shunt.

METHODS

From a retrospective cohort of patients who underwent cranial operations for management of cerebral aneurysms in 2005-2014, we identified patients who previously had a VP shunt placed, determined the temporal relationship between shunt placement and cranial operation, and investigated outcomes in those with and without a shunt.

RESULTS

Of 818 patients who underwent cranial operations, 28 (3.4%) had a VP shunt. Four of these 28 (14.3%, 95% confidence interval [CI] 4.0%-32.7%) developed postoperative complications, compared to 42 of 790 (5.3%, 95% CI 4.0%-7.1%) without a history of VP shunt (P = .07). In addition, patients with a shunt were more likely to have longer cranial procedures (P = .04), longer hospital stays (P = .05), and more computed tomography scans during their craniotomy-associated admission (P = .002). Multivariate analysis, though not significant, demonstrated that the presence of a shunt contributed to the development of complications (odds ratio [OR] 2.24, 95% CI .70-7.13, P = .17). Length of surgery (OR 1.17, 95% CI 1.04-1.31, P = .01) and length of stay (OR 1.04, 95% CI 1.01-1.07, P = .01) were significantly longer in those with a postoperative complication.

CONCLUSION

We found a nonsignificant trend toward increased postoperative complications in patients with a VP shunt who underwent a subsequent cranial operation.