Hydrocephalus

Incidence and Risk Factors for Post-traumatic Hydrocephalous Following Decompressive Craniectomy for Intractable Intracranial Hypertension and Evacuation of Mass Lesions

Authors: Honeybul S, Ho KM.

There continues to be a considerable amount of interest in decompressive craniectomy in the management of severe traumatic brain injury (TBI). Whilst technically straightforward the procedure is not without significant complications. This study assessed the incidence and risk factors for the development of subdural hygroma and hydrocephalus after decompressive craniectomy. A total of 195 patients who had had a decompressive craniectomy for severe TBI between 2004 and 2010 at the two major trauma centres in Western Australia were considered. Of the 166 patients who survived after the acute hospital stay, 93 (56%, 95% confidence interval 48-63%) developed subdural hygroma; 45 patients (48%) had unilateral and 48 patients (52%) had bilateral subdural hygroma. Of the 159 patients who survived more than 6 months after surgery, 72 (45%, 95% CI 38-53%) developed radiological evidence of ventriculomegaly and 26 of these 72 patients (36%, 95%CI 26-48%) developed clinical evidence of hydrocephalus and required a ventriculoperitoneal (VP) shunt. Maximum intracranial pressure prior to decompression (p=0.005), subdural hygroma (p=0.012) and a lower admission Glasgow Coma Scale (p=0.009) were significant risk factors for hydrocephalus after decompressive craniectomy. Hydrocephalus requiring a VP shunt was associated with a higher risk of unfavorable neurological outcome at 18-months (odds ratio 7.46, 95%CI 1.17-47.4; 0.033 ), after adjusting for other factors. Our results showed a clear association between injury severity, subdural hygroma and hydrocephalus, suggesting that damage to the cerebrospinal fluid drainage pathways as part of the primary brain injury rather than surgery itself is more likely to be responsible for these complications.

Morphological characterization of cardiac induced intracranial pressure (ICP) waves in patients with overdrainage of cerebrospinal fluid and negative ICP

Authors: Eide PK, Sroka M, Wozniak A, Sæhle T.

Symptomatic overdrainage of cerebrospinal fluid (CSF) can be seen in shunted hydrocephalus patients and in non-shunted patients with spontaneous intracranial hypotension (SIH). In these patients, intracranial pressure (ICP) monitoring often reveals negative static ICP, while it is less understood how the pulsatile ICP (cardiac induced ICP waves) is affected. This latter aspect is addressed in the present study. A set of 40 ICP recordings from paediatric and adult hydrocephalus patients were randomly selected. Each cardiac induced ICP wave was automatically identified and manually verified by the beginning and ending diastolic minimum pressures and the systolic maximum pressure. The ICP wave parameters (static pressure, amplitude, rise time, rise time coefficient, downward coefficient, wave duration, and area-under-curve) were then automatically computed. The material of 40 ICP recordings provided a total of 3,192,166 cardiac induced ICP waves (1,292,522 in paediatric patients and 1,899,644 in adult patients). No apparent changes in ICP wave parameters were seen when mean ICP became negative, except that the parameters amplitude, rise time coefficient, downward coefficient and area under curve somewhat increased when mean ICP was below -15mmHg.

Estimation of cerebrospinal fluid compensation parameters in hydrocephalus using short-lasting constant rate lumbar infusion tests

Authors: Piechnik SK, Ferreira VM, Cieslicki K.

Abstract Objectives. The lumbar infusion test is an invasive technique for quantifying cerebrospinal dynamics in patients with hydrocephalus. However, some patients have difficulty tolerating the duration of this procedure. Therefore, we investigated the limits of shortening the test by examining the reliability of cerebrospinal fluid (CSF) compensatory parameters as a function of time. Methods. We analysed recordings of the intracranial cerebral pressure (ICP) response to a constant, high-rate infusion of saline (2 ml/min) lasting 5.7-20 (12 ± 10) min in 30 patients with a preliminary diagnosis of hydrocephalus (13 men, aged 37-81 years). We performed computerised identification of CSF outflow resistance (R(out)), intracranial compliance parameters: elastance index (E) and reference pressure (P(0)), based on the truncated ICP response (20-100% of the available test length), estimating either all three parameters (3p method) or only R(out) and E (2p method) assuming P(0) as the regression between the ICP and its amplitude. Results. Following considerable variation during the initial rise of ICP, R(out) typically converged within ± 10% of their final values within 10-15 min. Final R(out) values were 4-40 (12 ± 6) mmHg/ml/min, and were method independent (R(2) = 0.97). Compliance parameters (E, typically 0.1-0.5/ml; P(0): - 10 to + 20 mmHg) agreed poorly between methods (R(2) = 0.3-0.7) and varied considerably within the observed infusion periods. Conclusion. The lumbar infusion test may be shortened to 10-15 min using a rapid infusion rate of 2 ml/min that fulfils the primary objective of obtaining reliable estimates of R(out). This may benefit patients who do not tolerate the full procedure.

Cognitive, biochemical, and imaging profile of patients suffering from idiopathic normal pressure hydrocephalus

Authors: Tarnaris A, Toma AK, Pullen E, Chapman MD, Petzold A, Cipolotti L, Kitchen ND, Keir G, Lemieux L, Watkins LD.

INTRODUCTION: It has still not been clearly established whether the cognitive deficits of idiopathic normal pressure hydrocephalus (iNPH) are caused by a disturbance in cerebrospinal fluid (CSF) dynamics or an underlying metabolic disturbance.

OBJECTIVE: To identify the possible associations between biochemical markers, the neuroimaging characteristics, and cognitive deficits of patients undergoing investigations for possible iNPH.

METHODS: A CSF sample obtained during a lumbar puncture from 10 patients with iNPH was analyzed for several biochemical markers (lactate, 8-isoprostane, vascular endothelial growth factor , neurofilament heavy protein, glial fibrillary acidic protein, amyloid beta 1-42, and total tau). All patients underwent a battery of neuropsychological testing and imaging as part of their selection process for their suitability for CSF diversion surgical procedure. Volumetric analysis of imaging was carried out measuring the ventricular volume (VV), intracranial volume (ICV), periventricular lucencies, deep white matter hyperintensities, and white matter (WM) volume, as well as their ratios.

RESULTS: A significant negative correlation of preoperative symptom duration and total tau levels (R = -0.841, P = .002) was found. There was a significant positive correlation (R = 0.648, P = .043) between the levels of VEGF and the VV/ICV ratio. There was a significant positive correlation of the levels of glial fibrillary acidic protein and the VV/deep white matter hyperintensities ratio (R = 0.828, P = .006). A significant negative correlation was observed between the levels of neurofilament heavy protein and the VV/ICV ratio (R = -0.657, P = .039) and the WM volume (R = -0.778, P = .023). Lactate levels were lower for patients performing in the normal range on the Recognition Memory Test for faces. Patients who performed better in the Recognition Memory Test words test had higher ICV volumes. All the patients in this study showed below normal performance when the subcortical function was assessed.

CONCLUSION: The positive correlation of VEGF with the severity of ventriculomegaly may indicate that this is because of the transmantle pressure gradient; this response may not be because of hypoxia but represents an attempt at neuroregeneration. The degree of reactive gliosis correlates inversely with the severity of WM lesions. Neuronal degeneration is negatively correlated with the volume of the WM in these patients. The small association of volumetry and the cognitive profile of these patients may be consistent with a direct biochemical disturbance being responsible for the cognitive deficit observed. Ongoing studies with set protocols for neuropsychological assessment and volumetric analysis are warranted to further elucidate on the preliminary results of the current study.

Resonant and notch behavior in intracranial pressure dynamics

Authors: Mark E. Wagshul, Ph.D.1,2,3, Erin J. Kelly, Ph.D.4, Hui Jing Yu, M.S.3, Barbara Garlick, Ph.D.5, Tom Zimmerman, D.V.M.6, and Michael R. Egnor, M.D.2

Object. The intracranial pulse pressure is often increased when neuropathology is present, particularly in cases of increased intracranial pressure (ICP) such as occurs in hydrocephalus. This pulse pressure is assumed to originate from arterial blood pressure oscillations entering the cranium; the fact that there is a coupling between the arterial blood pressure and the ICP is undisputed. In this study, the nature of this coupling and how it changes under conditions of increased ICP are investigated.

Methods. In 12 normal dogs, intracarotid and parenchymal pulse pressure were measured and their coupling was characterized using amplitude and phase transfer function analysis. Mean intracranial ICP was manipulated via infusions of isotonic saline into the spinal subarachnoid space, and changes in transfer function were monitored.

Results. Under normal conditions, the ICP wave led the arterial wave, and there was a minimum in the pulse pressure amplitude near the frequency of the heart rate. Under conditions of decreased intracranial compliance, the ICP wave began to lag behind the arterial wave and increased significantly in amplitude. Most interestingly, in many animals the pulse pressure exhibited a minimum in amplitude at a mean pressure that coincided with the transition from a leading to lagging ICP wave.

Conclusions. This transfer function behavior is characteristic of a resonant notch system. This may represent a component of the intracranial Windkessel mechanism, which protects the microvasculature from arterial pulsatility. The impairment of this resonant notch system may play a role in the altered pulse pressure in conditions such as hydrocephalus and traumatic brain swelling. New models of intracranial dynamics are needed for understanding the frequency-sensitive behavior elucidated in these studies and could open a path for development of new therapies that are geared toward addressing the pulsation dysfunction in pathological conditions, such as hydrocephalus and traumatic brain injury, affecting ICP and flow dynamics.

Monitoring and interpretation of intracranial pressure

Authors: M Czosnyka and J Pickard

Although there is no "Class I" evidence, ICP monitoring is useful, if not essential, in head injury, poor grade subarachnoid haemorrhage, stroke, intracerebral haematoma, meningitis, acute liver failure, hydrocephalus, benign intracranial hypertension, craniosynostosis etc. Information which can be derived from ICP and its waveforms includes cerebral perfusion pressure (CPP), regulation of cerebral blood flow and volume, CSF absorption capacity, brain compensatory reserve, and content of vasogenic events. Some of these parameters allow prediction of prognosis of survival following head injury and optimisation of "CPP-guided therapy". In hydrocephalus CSF dynamic tests aid diagnosis and subsequent monitoring of shunt function.

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