Prospective study of methodological issues in intracranial pressure monitoring in patients with hydrocephalus

Clinical Outcomes of Shunting in Normal Pressure Hydrocephalus: A Multicenter Prospective Observational Study

Background: Normal pressure hydrocephalus (NPH) is characterized by the triad of dementia, gait disturbance and urinary incontinence, all potentially reversible following a ventriculoperitoneal shunt (VPS). This study aims to evaluate the clinical outcomes of shunting in normal pressure hydrocephalus following a new standardized protocol. Methods: This study is designed according to the STROBE guidelines. Demographical, clinical, surgical and radiological data were collected from May 2015 to November 2019. Gait, balance and incontinence data based on the NPH European scale were collected before and after one, six and twelve months of treatment with a VPS. Clinical symptoms and changes of the stoke volume, measured on phase-contrast MRI, were used to evaluate improvement after VPS surgery. Results: One hundred and eighty-one consecutive patients met the inclusion criteria. The mean age was 73.1 years (59−86) and mean follow-up was 38.3 months (13−50). The gait (58.5 ± 14.3 to 70.1 ± 13.4, p < 0.001), the balance (66.7 ± 21.5 to 71.7 ± 22.1, p = 0.001), continence domain (69.9 ± 20.5 to 76 ± 20, p = 0.002) scores and neuropsychological scales showed a statistically significant improvement over the follow-up. The overall improvement after 12 months was present in 91.2% of patients. An overall complication rate of 8.8% and a reoperation rate of 9.4% were recorded, respectively. Conclusions: Surgical treatment by VPS for NPH improves symptoms in most patients, when accurately selected. A standardized protocol and a multidisciplinary team dedicated to this disorder is needed to achieve an early and correct diagnosis of NPH. Follow-up with stroke volume measurement is a valuable tool for the early diagnosis of shunt malfunction or the need for valve adjustment.

[Long-term prognosis of idiopathic chronic adult hydrocephalus: I. The University Hospital Marqués de Valdecilla diagnostic and therapeutic protocol]

INTRODUCTION

Despite the existence of published guidelines for more than a decade, there is still a substantial variation in the management of idiopathic normal pressure hydrocephalus due to its diagnostic and therapeutic complexity.

DEVELOPMENT

The diagnostic and therapeutic protocol for the management of idiopathic normal pressure hydrocephalus in use at the Department of Neurosurgery of the University Hospital Marqués de Valdecilla is presented. The diagnostic process includes neuropsychological testing, phase contrast cine MRI, urodynamic evaluation, continuous intracranial pressure monitoring, cerebrospinal fluid hydrodynamics by means of lumbar infusion testing, and intra-abdominal pressure measurement. A patient is considered a surgical candidate if any of the following criteria is met: mean intracranial pressure >15mmHg, or B-waves present in >10% of overnight recording; pressure-volume index <15ml, or resistance to cerebrospinal fluid outflow (R_OUT) >4.5mmHg/ml/min in bolus infusion test; R_OUT >12mmHg/ml/min, intracranial pressure >22mmHg, or high amplitude B-waves in the steady-state of the continuous rate infusion test; or a clinical response to high-volume cerebrospinal fluid withdrawal.

CONCLUSIONS

The implementation of a diagnostic and therapeutic protocol for idiopathic normal pressure hydrocephalus management could improve various aspects of patient care. It could reduce variability in clinical practice, optimise the use of health resources, and help in identifying scientific uncertainty areas, in order to direct research efforts in a more appropriate way.

Cognitive disturbances and neuropsychological changes after surgical treatment in a cohort of 185 patients with idiopathic normal pressure hydrocephalus

Although idiopathic normal pressure hydrocephalus (iNPH) is considered a treatable dementia, there is still some controversy regarding the cognitive improvement in these patients. The main aims of this study were to analyze baseline cognitive status and to study the neuropsychological changes after surgical treatment in a sample of 185 consecutive iNPH patients. An additional aim was to identify the variables that influenced the cognitive outcome. Specific tests assessing memory, attention, visual scanning, executive functions (EFs), and motor speed were used before and 6 months after shunting. The cognitive domains most affected at baseline were memory, EFs, attention, and psychomotor speed. After shunting, significant differences in the group as a whole were found in all tests except Digits Forward and Trail Making Part B. However, less than 50% of patients showed a significant improvement when analyzed individually. Previous global cognitive status assessed by Mini-Mental State Examination baseline scores was the best predictor for the cognitive outcome.

Intracranial pressure monitoring with the Neurodur-P epidural sensor: a prospective study in patients with adult hydrocephalus or idiopathic intracranial hypertension

OBJECT

Continuous intracranial pressure (ICP) monitoring using an epidural sensor is a common technique used in selected neurosurgical patients. The aim of this study was to assess the safety and accuracy of the Neurodur-P epidural sensor in the clinical setting.

METHODS

The zero drift, as well as the medical and technical complications, of using the Neurodur-P sensor placed in the epidural space was evaluated in 106 patients with hydrocephalus of varying causes or with suspected intracranial hypertension.

RESULTS

The median duration of ICP monitoring was 8 days (interquartile range [IQR] 6-12 days). In 78 (73.6%) of the 106 patients the pressure reading was recorded at sensor removal. No zero drift was observed in 28 sensors. The median drift was 0 mm Hg with an IQR of -1 to 1 mm Hg. No significant differences were found between patients monitored for < or = 5 days and those monitored for > 5 days (t = 535, p = 0.100). No correlation was found between zero drift and monitoring time (r = 0.153, p = 0.181). Of the 83 patients with a follow-up computed tomography scan, 3 showed a < 1 ml collection of blood at the catheter tip. No clinical infections could be attributed to the devices. Only 1 sensor malfunctioned.

CONCLUSIONS

Continuous ICP monitoring using the Neurodur-P sensor is safe, reliable, and easy to perform. At present, using this device is the authors' standard method for the long-term monitoring of patients with alterations in complex cerebrospinal fluid dynamics or with implanted shunts.

Intra-abdominal pressure: the neglected variable in selecting the ventriculoperitoneal shunt for treating hydrocephalus

OBJECTIVE

In the selection of a ventriculoperitoneal cerebrospinal fluid shunt, the intra-abdominal pressure (IAP) is traditionally neglected as a result of the idea that its value is close to 0 mmHg. Our aim was to explore the relationship between body mass index (BMI) and IAP with the goal of providing clinically relevant data that could help neurosurgeons to estimate IAP and select the appropriate shunt for patients with hydrocephalus and especially those with normal-pressure hydrocephalus syndrome.

METHODS

Sixty patients requiring the placement of a ventriculoperitoneal shunt were included in the study. We determined weight, BMI, and IAP. IAP was measured through an intraperitoneal catheter during the shunt surgery. To determine whether a linear relationship existed between quantitative variables, linear regression analysis was used.

RESULTS

BMI was 28.1 +/- 4.8 kg/m2. Eighteen patients (30%) had normal weight, 21 (35%) were moderately overweight, and 21 (35%) were obese. IAP was related to patient BMI. A significant positive linear correlation was identified between BMI and IAP (r = 0.52; P = 0.018) with a slope of 0.31 (P < 0.001) and an intercept of -5.5.

CONCLUSION

In our study, we determined that IAP had a strong positive linear relationship with BMI. This correlation was independent of sex. An IAP of 0 mmHg can, therefore, only be assumed for patients with a normal BMI who are recumbent. In obese or overweight patients, neurosurgeons should take IAP into account when selecting both the most adequate differential pressure valve to be implanted and in which distal cavity to place the distal catheter to avoid shunt underdrainage induced by high IAP.

Monitoring intracranial pressure in traumatic brain injury

Increased intracranial pressure (ICP) is an important cause of secondary brain injury, and ICP monitoring has become an established component of brain monitoring after traumatic brain injury. ICP cannot be reliably estimated from any specific clinical feature or computed tomography finding and must actually be measured. Different methods of monitoring ICP have been described but intraventricular catheters and microtransducer systems are most widely used in clinical practice. ICP is a complex variable that links ICP and cerebral perfusion pressure and provides additional information from identification and analysis of pathologic ICP wave forms. ICP monitoring can also be augmented by measurement of indices describing cerebrovascular pressure reactivity and pressure-volume compensatory reserve. There is considerable variability in the use of ICP monitoring and treatment modalities among head injury centers. However, there is a large body of clinical evidence supporting the use of ICP monitoring to detect intracranial mass lesions early, guide therapeutic interventions, and assess prognosis, and it is recommended by consensus guidelines for head injury management. There remains a need for a prospective, randomized, controlled trial to identify the value of ICP monitoring and management after head injury.

Brain metabolism during a decrease in cerebral perfusion pressure caused by an elevated intracranial pressure in the porcine neocortex

BACKGROUND

Cranial hypertension coincides with a reduction in cerebral blood flow as well as in oxygen delivery and influences outcome. In this study, we monitored changes in energy-related metabolites in the porcine cortex during an increase of intracranial pressure (ICP) and to determine the level at which damage occurs.

METHODS

Male domestic pigs (32-40 kg) were anesthetized, mechanically ventilated, and randomly assigned to either the experimental (n = 6) or control groups (n = 5). A microdialysis probe (CMA 70) was inserted into the cortex to measure extracellular dialysate concentrations of lactate, pyruvate, glucose, glutamate, and glycerol. Every hour an increase of 10 mm Hg in ICP was preformed in the experimental group by infusion of artificial cerebrospinal fluid into the ventricular system of the brain until a maximum ICP of 50 mm Hg was reached.

RESULTS

We demonstrated a significant increase of lactate and glycerol compared with control at ICP values > or =30 mm Hg and cerebral perfusion pressure (CPP) below 50 mm Hg. The increase of ICP to > or =40 mm Hg in conjunction with a reduction in CPP below 40 mm Hg led to a significant increase in the lactate/pyruvate-ratio and glutamate, as well as a decrease of glucose in relation to control.

CONCLUSIONS

Our data strongly suggest that, during a defined ICP increase, lower CPP values may be tolerable until severe damage occurs. Borderline ICP and CPP values of 30 and 40 mm Hg, respectively, could be advised.

Is intracranial pressure monitoring in the epidural space reliable? Fact and fiction

Object

Epidural pressures have been reported as being systematically higher than ventricular fluid pressures. These discrepancies have been attributed both to the characteristics of the sensor and to the particular anatomy of the epidural space. To determine which of these two possible causes better explains higher epidural readings, the authors compared pressure values obtained during simultaneous epidural and lumbar pressure monitoring in 53 patients and during simultaneous subdural and lumbar pressure monitoring in 22 patients. The same nonfluid coupled sensor device was used in all compartments.

Methods

All 75 patients had normal craniospinal communication. Simultaneous intracranial and lumbar readings were performed every 30 seconds. The epidural–lumbar and subdural–lumbar pressure values were compared using correlation analysis and the Bland–Altman method.

The median differences in initial epidural–lumbar and subdural–lumbar pressure values were 11 mm Hg (interquartile range 2–24 mm Hg) and 0 mm Hg (interquartile range −2 to 1 mm Hg), respectively. The correlation coefficients of the mean epidural–lumbar and subdural–lumbar intracranial pressure (ICP) values were ρ = 0.48 (p < 0.001) and ρ = 0.88 (p < 0.001), respectively. Using the Bland–Altman analysis, epidural–lumbar methods showed a mean difference of −20.93 mm Hg; epidural pressure values were systematically higher than lumbar values, and these discrepancies were greater with higher ICP values. Subdural–lumbar methods showed a mean difference of 0.35 mm Hg and both were equally valid with all mean ICP values.

Conclusions

Epidural ICP monitoring produces artifactually high values. These values are not related to the type of sensor used but to the specific characteristics of the epidural intracranial space.

Posture-induced Changes in Intracranial Pressure: A Comparative Study in Patients with and without a Cerebrospinal Fluid Block at the Craniovertebral Junction

OBJECTIVE

The aim of this study was to determine posture-induced changes in intracranial pressure (ICP) when patients with hydrocephalus or idiopathic intracranial hypertension remained supine for 1 hour and then sat up and remained sitting for 3 hours.

METHODS

Continuous ICP was monitored using a fiberoptic extradural sensor in: 1) 259 patients with hydrocephalus or idiopathic intracranial hypertension with free cerebrospinal fluid (CSF) flow through the craniovertebral junction and Sylvian aqueduct, 2) 20 patients with hydrocephalus secondary to aqueductal stenosis with free CSF flow through the craniovertebral junction, and 3) 97 patients with hydrocephalus associated with Chiari malformation. The maximum ICP difference (DeltaICP) was calculated as the difference between mean ICP in the supine position and minimum ICP value after changing body position. The mean ICP difference (DeltaICPmean) was calculated as the difference between the mean ICP in the supine position and the mean ICP while the patient was in a sitting position.

RESULTS

In the complete sample, the median of DeltaICP was 13 mm Hg (interquartile range 10-17). The median of DeltaICPmean was 8 mm Hg (interquartile range 5-11). Both DeltaICP and DeltaICPmean were significantly greater in patients without obstruction in the craniospinal junction than in those with Chiari malformation (P = 0.005 and P = 0.014, respectively). No differences were found in DeltaICP or DeltaICPmean between patients with Sylvian aqueduct stenosis and those without (P = 0.777 and P = 0.346, respectively).

CONCLUSION

ICP reduction after a change in body position is significantly greater in patients with free CSF flow through the craniospinal junction than in those with Chiari malformation, indicating the difficulty or impossibility of CSF displacement into the spinal canal in the latter.

Ventricular enlargement after moderate or severe head injury: a frequent and neglected problem

The primary goal of this study was to determine the incidence of post-traumatic ventriculomegaly (Evans' index > or = 0.30) in 95 head-injured patients with a Glasgow Coma Scale (GCS) score of < or =13 at admission. Additional objectives were to determine the relationship between an increase in ventricular size and several clinical and radiological features and outcome. A planimetric study was carried out in the sequential control computed tomography (CT) scans of 34 moderately head-injured (GCS 9-13) and 61 severely head-injured (GCS 3-8) patients with a minimum follow-up of 2 months. Between two and six CT scans were evaluated in each patient. The presence of subarachnoid hemorrhage (SAH) was registered. Evans' index was determined in all CT scans. In the final CT scan of each patient, ventricular size was related to the admission GCS score, age, the presence of SAH in the initial CT scans, type of brain lesion (classified according to the final diagnosis in the Traumatic Coma Data Bank classification), and outcome. Ventriculomegaly was found in 39.3% of patients with severe head injury and in 27.3% of those with a moderate head injury. Increased ventricular size was evident 4 weeks after injury in 57.6% and 2 months after injury in 69.7%. No relationship was found between post-traumatic ventriculomegaly and age, initial GCS score, the presence of SAH, or type of lesion (focal or diffuse). Post-traumatic ventriculomegaly was significantly correlated with outcome. Post-traumatic ventriculomegaly is a frequent and early finding in patients with moderate or severe traumatic brain injury.

Good outcome in patients with normal-pressure hydrocephalus and factors indicating poor prognosis

OBJECT

The authors set out to describe the outcome in a subgroup of patients with normal-pressure hydrocephalus (NPH) in whom prognostic factors were poor. This subgroup of patients who had received shunts was selected according to strict criteria.

METHODS

From a cohort of 56 patients with NPH in whom shunts were placed, the authors selected a subgroup with four of the factors traditionally considered to indicate poor prognosis: idiopathic type, cortical atrophy, longstanding symptoms, and presence of dementia in addition to old age. Twelve patients met the inclusion criteria. After receiving shunts, 92% of the patients showed clinical improvement on the NPH scale; gait improved in 100% of patients, sphincter control in 90%, and dementia in 33%. Improvement was significant for gait and sphincter control, general NPH score, and most daily life activity scales. No significant differences regarding clinical, cognitive, or functional changes following surgery were found in comparison with the rest of patients (the good prognosis subgroup).

CONCLUSIONS

The clinical condition of patients with NPH who present with traditionally accepted markers of poor prognosis can improve after surgery, especially as regards gait and sphincter control. The authors assert that the presence of these markers should not be considered to be an absolute criterion for ruling out shunt surgery in cases of NPH syndrome.

Monitoring of head injured patients

PURPOSE OF REVIEW

This article reviews recent advances in multimodality monitoring of patients following severe head injury during the period of 2004-2005.

RECENT FINDINGS

Whilst intracranial pressure measurement remains the cornerstone of neuromonitoring, analysis of the intracranial pressure waveform provides additional information, which may help guide treatment and predict outcome. Non-invasive detection of intracranial hypertension and assessment of cerebral perfusion pressure and autoregulation is the focus of ongoing research. Although jugular venous saturation monitoring remains a useful method for detecting global hypoperfusion its sensitivity to regional ischaemia is low. Brain tissue oxygen monitoring overcomes this deficiency and sheds new light on the pathophysiology of cerebral ischaemia following brain injury. Further studies are required to define ischaemic thresholds and their association with outcome. Extracellular brain pH has been recently linked to outcome and further studies are required to establish the role of pH regulation. Monitoring of brain metabolism using a cerebral microdialysis continues to develop its niche in clinical neuromonitoring, although it currently remains a research tool.

SUMMARY

Multimodality neuromonitoring plays an important role in managing patients with severe head injury. It helps guide treatment, provides prognostic information and explores the pathophysiology of evolving brain injury.