Complications of brain tissue pressure monitoring with a fiberoptic device

Seventy-five patients with intracranial hypertension whose Glasgow Coma Score (GCS) was 8 or below and in whom intracranial pressure (ICP) was monitored were examined for complications of this procedure. In 20 of the 75 patients we used only an intraparenchymal fiberoptic ICP monitoring transducer, while, in the remaining 55 patients, who required CSF drainage, a ventricular drainage set (VDS) was used in addition to ICP monitoring. The duration of monitoring with the ICP transducer alone was approximately 5.1 ± 2.6 das (min. 1, max. 13) and that of ICP monitoring with VDS was 6.2 ± 3.1 days (min. 1, max. 13). In 8 cases a total of 9 complications were experienced (12 %). These complications were infection in 3 cases (4 %), epidural hematoma in 2 cases (2.7 %), disconnection in 2 cases (2.7 %) and contusion in 2 cases (2.7 %). Although none of the 44 patients who were monitored for less than 5 days experienced infection, 3 of the 31 patients monitored for longer than 5 days did experience infection (9.7 %) (p < 0.05). None of the 20 patients who underwent ICP monitoring only experienced infection. However, 3 of the 55 patients in whom the ventricular drainage set was implanted in addition to the transducer for ICP monitoring experienced infection (p < 0.05).Owing to its minimally invasive nature, low complication rate, and accuracy in monitoring the parenchyma pressure, the Camino fiberoptic intraparenchymal monitor has become the system of choice in our clinic.     

Analysis of the ICP pulse-pressure relationship as a function of arterial blood pressure clinical validation of a mathematical model

Summary The influence of arterial blood pressure (ABP) on the intracranial pulse pressure relationship (PPR) was studied in 17 patients in 29 recordings, with a total period of registration of 71.5 hours. The relationship between ICP and ABP was analysed by sampling the data every 15 seconds during spontaneous fluctuations of both these variables, and the analysis was performed on the basis of a mathematical model which includes pulsatory components. MABP and ABP amplitude had an opposite effect on the slope of PPR. Flattening of the PPR slope was caused by a MABP increase or an ABP amplitude decrease. The slope became steeper with decreasing MABP or increasing ABP amplitude. In accordance with the theoretical assumptions the quotient MABP/ABP-AMP was found to be suitable to express these opposite effects on PPR. Qualitatively, the same pattern of reaction was found in all patients. Rapid changes in PPR occurring during monitoring can be explained by a change in MABP/ABP-AMP relationship, regardless whether ABP changes influence intracranial elastance or not. The breakpoint of the PPR was recorded only on two occasions and could be explained in one by the influence of ABP. Monitoring of PPR as a measure of intracranial elastance and correlation of PPR with the patient's condition it not permitted unless at least the influence of ABP is analysed in each individual case.Definitions of Abbreviations and Symbols ABP Arterial blood pressure - ABP-AMP Arterial blood pressure amplitude - c_a Elastance coefficient of intracranial arterial vessels - CSF Cerebrospinal fluid - C_v Compliance of the venous part of the vascular bed - CVP Central venous pressure - E_art Volume elasticity of intracranial arterial vessels - HR Heart rate - ICP Intracranial pressure - ICP-AMP Intracranial pressure amplitude - K_a Absorption rate of cerebrospinal fluid - K_s Secretion rate of cerebrospinal fluid - K_v Intracranial pressure volume curve determining parameter - MABP Mean arterial pressure - MICP Mean intracranial pressure - P_art Systemic arterial blood pressure - P_csf Cerebrospinal fluid pressure - P_ven Systemic venous pressure - ¯P ... Mean pressure - P Pressure amplitude or change in pressure - PPR Intracranial pulse pressure relationship - PVI Pressure volume index - RR Respiration rate - V Injected volume during a volume pressure test or the transient intracranial volume increase per cardiac cycle - VPR Volume pressure response - VPT Volume pressure test     

The role of the pulsatile pressure variations in intracranial pressure monitoring

Summary The magnitude of the pulsatile intracranial pressure variations (CSF pulse pressure) is determined by the elastance of the craniospinal system and by the magnitude of the pulsatile variations in cerebral blood volume (CBV). The pulsatile change in CBV is, among other factors, determined by the compliance of the cerebral vascular bed which, in its turn, is dependent on the cerebral vasomotor tone. This concept has led the authors to devise a method for the assessment of both the elastance and the state of the cerebral vasomotor tone based on the relationship between CSF pulse pressure and intracranial pressure. This relationship was found to be of a linear nature both in clinical patients and in experimental animals. A significant, positive correlation was found between the slope of this relationship and the value of the craniospinal volume-pressure relationship: the elastance coefficient. During elevation of the intracranial pressure a breakpoint was observed in the relationship between CSF pulse pressure and the intracranial pressure above which the pulse pressure increased more rapidly. The elastance remained constant above this breakpoint. The same phenomenon was observed during plateau waves in clinical patients. Induced changes in systemic arterial pressure produced opposite effects on CSF pulse pressure and elastance coefficient. In these cases the discrepancy between pulse pressure and elastance was attributed to the pulsatile changes in CBV and this could be verified by means of electromagnetic flowmetry. The advantage of this method is that all the information is contained within the intracranial pressure signal itself, from which it can be extracted by simple means without the use of invasive tests.     

The CAMINO Intracranial Pressure Device in Clinical Practice: Reliability, Handling Characteristics and Complications

Summary  Intracranial pressure monitoring has a key role in the management of patients developing increased intracranial pressure (ICP). We adopted the Camino fiberoptic system for intracranial pressure measurement in 1993 in our neurosurgical department. The aim of this study was to investigate reliability, handling characteristics and complication rate of the Camino intracranial pressure device.  In an eighteen month period, we prospectively investigated 118 patients with intracranial pathology undergoing Camino fiberoptic intraparenchymal or intraventricular ICP monitoring. The assessment of reliability of ICP monitoring according to patients clinical condition, to cranial computed tomography (CCT) findings and ICP waveform was carried out. Position of the probe and intracranial bleeding complications related to probe insertion were confirmed by CCT. Technical complications, as well as infections due to the device, were documented. In vivo recalibration was performed in 22 patients. At the end of the measuring period the drift of the probe was evaluated and the accuracy of the fiberoptic device was measured by performing a two point calibration.  Recordings of intracranial pressure were carried out with 136 Camino devices (104 parenchymal, 32 ventricular) in 118 patients with an average measuring time of 94.1±79.1 hrs. One hundred and fifteen Camino intracranial pressure devices (85.2%) demonstrated reliability according to the predetermined clinical parameters. The actual mean drift after removal of the devices was 3.4 mmHg±3.2 with an actual daily drift of 3.2±17.2 mmHg. Recorded complications included infection (0.7%), intraparenchymal haematoma (5.1%), and a high complication rate (23.5%) with regard to technical aspects. The Camino intracranial pressure system offers reliable ICP measurements in an acceptable percentage of devices, and the advantage of in vivo recalibration. The high incidence of technical complications identifies a need for improvement in the fiberoptic cable and the fixation system.     

A computer-based method for comparisons of continuous intracranial pressure recordings within individual cases

Summary ?Background. This study assessed two strategies of comparing continuous intracranial pressure (ICP) recordings within individual cases, namely either by calculation of differences in mean ICP or by calculation of differences in numbers of ICP elevations. Methods. Continuous ICP recordings before and after cranial surgery were both presented as mean ICP and as numbers of ICP elevations of different levels (20 and 25 mmHg lasting either 0.5 or 1 minute). Since the length of pressure recordings differed somewhat between individuals, the numbers of ICP elevations were standardised by computing the numbers of elevations during a 10 hours period. The ICP recordings were analysed by the Sensometrics^™ Pressure Analyser software. The ICP curves included here were selected from a group of 15 children undergoing calvarial expansion surgery for craniosynostosis, in whom continuous ICP monitoring was performed both before and after surgery as part of the diagnostic workout to rule out lasting intracranial hypertension. Findings. After surgery, mean ICP during sleep was reduced by 5 mmHg or more in 5 cases, minimally changed (i.e. 2 mmHg or less) in 6 cases, and variably increased in the other 4 cases. In one of these 4 latter cases, numbers of ICP elevations were increased after surgery, but in all other 14 cases the numbers of ICP elevations were significantly reduced. Reduction of mean ICP by more than 2 mmHg associated with good outcome was observed in 3 of 15 cases (20%), whereas marked and significant reductions in numbers of ICP elevations during sleep combined with good outcome was observed in 12 of 15 cases (80%). Interpretation. Outcome after the 2^nd ICP monitoring was more reliably predicted by computing differences in numbers of ICP elevations than by calculation of mean ICP. Published online June 4, 2003     

Predicting the response of intracranial pressure to moderate hyperventilation

Summary Background. Hyperventilation may cause brain ischaemia after traumatic brain injury. However, moderate reductions in PaCO₂ are still an option in the management of raised intracranial pressure (ICP) under some circumstances. Being able to predict the ICP-response to such an intervention would be advantageous. We investigated the ability of pre-hyperventilation ICP and cerebrospinal compensatory reserve to predict the reduction in ICP achievable with moderate hyperventilation in head injured patients.Methods. Thirty head injured patients requiring sedation and mechanical ventilation were investigated. ICP was monitored via an intraparenchymal probe and intracranial cerebrospinal compensatory reserve was assessed using an index (R_ap) based on the relationship between mean ICP and its pulse amplitude. Measurements were made at a constant level of PaCO₂ during a 20-minute baseline period. The patients were then subjected to an acute decrease in PaCO₂ of approximately 1kPa and, after an equilibration period of 10 minutes, measurements were again made at a constant level of PaCO₂ for a further 20 minutes. A multiple linear regression model, incorporating baseline PaCO₂, ICP, and R_ap was used to identify the relevant predictors of ICP reduction.Findings. Baseline ICP and R_ap were both significant predictors of ICP-reduction (p=0.02 and 0.001 respectively) with R_ap being the more powerful parameter.Conclusions. A model based on cerebrospinal compensatory reserve and ICP can predict the achievable ICP-reduction and may potentially be used to optimise patient selection and intensity of hyperventilation.     

Long-term measurement of intracranial pressure. Technical problems and indications

Summary Long-term monitoring of epidural pressure with coplanar devices has not fulfilled the expectations, because the insertion of the transducer membrane is not possible with sufficient accuracy. Miniaturized, drift free epidural pressure transducers often provide too high values corresponding to the changing local tissue resistance, especially during the first hours of monitoring. If one keeps this peculiarity in mind, stable and representative values can be expected after this initial period of brain tissue relaxation. With normal or enlarged ventricles VFP measurement is at present the safest method of obtaining reliable pressure values.From the point of view of treatment long-term measurement of ICP should be preferred, when coma or clouding of consciousness with severe neurologic deficits or rapid alterations of fluid dynamics must be taken into account.     

Raised intracranial pressure and seizures in the neurological intensive care unit

Background. The relationship between changes in intracranialpressure and incidence of subclinical seizures in patients requiringneurological intensive care is not fully understood. The aimof this study was to investigate if acute increases in intracranialpressure were accompanied by subclinical seizures. Methods. We prospectively studied 17 intensive care patients(11 male, aged 3–66 yr) who were selected from 85 patientsrequiring intracranial pressure measurement. Patients were selectedto have a 30 min, 16-channel electroencephalogram (EEG) recordedwhen intracranial pressure remained increased despite preliminarytreatments. Results. Diagnoses included head injury, intracranial haemorrhage,subarachnoid haemorrhage and sagittal sinus thrombosis. Allpatients had at least one acute episode of intracranial pressureincrease. Pressures ranged from 90 to 440 mm H₂O. Encephalopathicfeatures (delta/theta rhythms and burst suppression) were notedon all EEGs. No seizure activity was recorded. Conclusions. We conclude from this pilot study that seizuresare an uncommon cause of acute raised intracranial pressure.To determine whether raised intracranial pressure causes seizures,long-term monitoring in a large cohort of intensive care patientswould be necessary, studying patients with similar diagnosesand ages. Br J Anaesth 2003; 90: 39–42     

The relationship between intracranial pressure and size of cerebral ventricles assessed by computed tomography

Summary.  Background: This study explored whether assessment of the cerebral ventricular size (or changes in size) by cranial computed tomography (CT) is a reliable way to predict the intracranial pressure (ICP).  Methods: A total of 224 cranial CT scans and continuous 24 hours ICP recordings in 184 patients were examined and compared. In these cases examinations were undertaken on the basis of suspected craniosynostosis, hydrocephalus or extracranial shunt failure. Simultaneous CT scanning and ICP monitoring was performed twice in 31 cases. Various measures of cerebral ventricular size were computed on the basis of CT, including Evan's index, third ventricular index, cella media index and ventricular score. Various measures of ICP were computed by means of the software Sensometrics^TM Pressure Analyser, including computation of mean ICP, numbers of ICP elevations (20–30 mmHg lasting either 0.5, 1, 5 or 10 minutes), and numbers of ICP depressions (−5 or −10 mmHg lasting either 0.5, 1, 5 or 10 minutes) during a standardized recording time of 10 hours. The relationships between the various measures of ventricular size and the various measures of ICP were explored.  Findings: There was a weak and non-significant relationship between the various measures of ventricular size and the measures of ICP in the 184 cases. There was a weak relationship between changes in size of cerebral ventricles and changes in ICP in the 31 cases examined twice.  Interpretation: The present results suggest that actual size or changes in size of the cerebral ventricles were no reliable predictors of ICP or changes in ICP, suggesting that great caution should be exercised when predicting ICP on the basis of the size of the cerebral ventricles on cranial CT scanning. Published online March 3, 2003 Acknowledgments  The author thanks Professor Thore Egeland, Section of Medical Statistics, University of Oslo for help during the statistical evaluation of the data.  Correspondence: Per Kristian Eide M.D., Ph.D., Department of Neurosurgery, The National Hospital, Sognvannsveien 20, N-0027 Oslo, Norway.     

The effect of increased intracranial pressure on pressure in the superior sagittal sinus

Summary It is difficult to explain why rises in ICP provoke different types of response in superior sagittal sinus pressure. In most of our experimental animals there was close correlation between rises in ICP and SSSP. In the remainder, SSSP showed little increase when ICP rose. The animals with marked increase in SSSP showed a greater capacity for compensation for increased amounts of intracranial fluid.     

Head injury,subarachnoid hemorrhage and intracranial pressure monitoring in Italy

Background. Intracranial pressure monitoring is recommended for the management of severe head injury and is increasingly used during intensive care for other pathologies, such as subarachnoid hemorrhage. However, it is still not uniformly applied in different centers. The objectives of this paper are to summarize the frequency and the modalities of intracranial pressure (ICP) monitoring in different centers in Italy; to describe its use in traumatic brain injury (TBI) and in subarachnoid hemorrhage (SAH); and to identify areas for improvement. Method. The medical directors of either the neurosurgical department or the intensive care unit, or both, of every Italian neurosurgical center were personally interviewed. They answered specific questions about TBI and SAH patients admitted, and ICP monitoring used, in their units. Data were cleared of any obvious inconsistencies and entered in a database for analysis. All analyses were based simply on the data declared. Findings. The clinical information was obtained from 9137 TBI cases, of whom 4240 severe, and 3151 SAH patients. Among the 106 participating centers, 15 did not use ICP monitoring at all. The remaining 91 had used 3293 ICP devices during the year 2001; 146 were used in tumor cases, 2009 in TBI, and 1138 in SAH. Twenty-two percent of TBI cases admitted to centers with ICP equipment were monitored. Restricting this analysis to severe cases, 47% of TBI with a GCS <8 had ICP. On average, 36% of SAH underwent ICP monitoring. The proportions of head injury and SAH cases who underwent ICP monitoring varied widely in the different centers. Dividing the country into three main areas (north, center and south), there were considerable differences both in the rate of admissions per million inhabitants and in the frequency of ICP monitoring. Interpretation. ICP monitoring in Italy is used in most, but not all, centers. ICP is measured fairly extensively in head injury cases, but a significant proportion of SAH patients is monitored as well. There are substantial differences in the frequency of ICP monitoring in different parts of the country. The use of ICP for both these indications, and the rates of admission to specialized centers, could be improved.Published online July 31, 2003     

The relation of intracranial pressure B-waves to different sleep stages in patients with suspected normal pressure hydrocephalus

Summary The interpretation of data from continuous monitoring of intra-cranial pressure (ICP) in patients with suspected normal pressure hydrocephalus (NPH) is the subject of controversy. Despite the fact that overnight ICP monitoring is widely used for the diagnosis of NPH, normative criteria are poorly defined. The present study demonstrates that there is a relationship between the relative frequency, the absolute amplitude, the wavelength and the morphology of B-waves and different sleep stages.Intraventricular intracranial pressure was recorded continuously overnight in 16 patients with suspected normal pressure hydrocephalus. Simultaneous polysomnography was performed to investigate the relation of spontaneous ICP oscillations to different sleep stages. A correlative analysis was done with the data of 13 patients. Three patients were excluded, one who was awake throughout the night and two in whom polysomnography was incomplete due to technicai reasons. The mean resting cerebrospinal fluid (CSF) pressure was 12.87 cm CSF. B-waves were observed in the ICP recordings of all patients. They were present for a mean of 72% of the total recording time. The relative frequency of B-waves was higher during REM sleep and sleep stage 2 as compared to wakefulness (87.8% and 83.2% vs. 56, p < 0.05). The absolute amplitude was higher during REM sleep than in wakefulness (9.56 vs. 3.44 cm CSF, p < 0.05). Wavelengths were longer in REM sleep than in wakefulness and stages 1 and 2 (62.4 vs. 42, 40.7 and 44.8 sec, p < 0.05). The morphology of B-waves was also related to different sleep stages. Ramp-type B-waves were associated with REM sleep in six patients, however, were also present in sleep stage 2 in three of them.Knowledge of the relation of spontaneous ICP oscillations to different sleep stages may help to establish physiological foundations and alterations. Furthermore, polysomnography may be useful to avoid erroneous interpretation of ICP recordings due to sleep stage related variability.     

Metabolic failure precedes intracranial pressure rises in traumatic brain injury: a microdialysis study

Summary Background: Cerebral microdialysis (MD) is able to detect markers of tissue damage and cerebral ischaemia and can be used to monitor the biochemical changes subsequent to head injury. In this prospective, observational study we analysed the correlation between microdialysis markers of metabolic impairment and intracranial pressure (ICP) and investigated whether changes in biomarker concentration precede rises in ICP. Methods: MD and ICP monitoring was carried out in twenty-five patients with severe TBI in Neurointensive care. MD samples were analysed hourly for lactate:pyruvate (LP) ratio, glutamate and glycerol. Abnormal values of microdialysis variables in presence of normal ICP were used to calculate the risk of intracranial hypertension developing within the next 3 h. Findings: An LP ratio >25 and glycerol >100 μmol/L, but not glutamate >12 μmol/L, were associated with significantly higher risk of imminent intracranial hypertension (odds ratio: 9.8, CI 5.8–16.1; 2.2, CI 1.6–3.8; 1.7, CI 0.6–3, respectively). An abnormal LP ratio could predict an ICP rise above normal levels in 89% of cases, whereas glycerol and glutamate had a poorer predictive value. Conclusions: Changes in the compound concentrations in microdialysate are a useful tool to describe molecular events triggered by TBI. These changes can occur before the onset of intracranial hypertension, suggesting that biochemical impairment can be present before low cerebral perfusion pressure is detectable. This early warning could be exploited to expand the window for therapeutic intervention. Correspondence: Antonio Belli, FRCS (Gla), FRCS (SN), MD, Division of Clinical Neurosciences, Southampton University Hospital, Tremona Road, Southampton SO16 6YD, UK.     

The relationship of intracranial pressure Lundberg waves to electroencephalograph fluctuations in patients with severe head trauma

Summary Lundberg (or B) waves, defined as repetitive changes in intracranial pressure (ICP) occurring at frequencies of 0.5 to 2 waves/min, have been attributed to cerebral blood flow fluctuations induced by central nervous system pace-makers or cerebral pressure autoregulation. We prospectively recorded and digitalized at a frequency rate of 10Hz (AcqKnowledge^TM software) the following parameters in 6 brain injured patients: mean arterial pressure, heart rate, ICP, mean flow velocity of the middle cerebral artery (MFV_MCA) (transcranial Doppler WAKI^TM) and left and right spectral edge frequency (SEFl, SEFr) of continuous electroencephalogram (EEG) recordings (Philips^TM technologies). All patients were sedated using a combination of sufentanil and midazolam and mechanically ventilated. Cerebral electrical activity (oscillations of SEF at a mean frequency of 26±9mHz) and MFV_MCA fluctuations were found strongly correlated with the intracranial Lundberg B waves (mean frequency 23±7mHz). These result support the existence of a neuropacemaker at the origin of the Lundberg B waves. The change in cerebral electrical activity, resulting from cerebral pacemakers, could increase cerebral metabolic rate of oxygen (CMRO₂) and thus lead to an increase in cerebral blood flow and secondarily of ICP through a change in cerebral blood volume.     

Five-year outcome of normal pressure hydrocephalus with or without a shunt: predictive value of the clinical signs,neuropsychological evaluation and infusion test

Summary. Summary.   Background: Between 1993–1995, 51 patients under 75 years of age with clinical symptoms and CT-based diagnosis of normal pressure hydrocephalus were investigated prospectively in order to clarify the value of neuropsychological tests, clinical symptoms and signs and infusion test in the differential diagnosis and prediction of outcome in normal pressure hydrocephalus.   Methods: Patients had a thorough neurological examination, and neuropsychological evaluation. A 24-hour intraventricular ICP-measurement, infusion test, neurophysiological investigations and MRI study were performed, and a cortical biopsy was obtained. The ICP measurement defined the need for a shunt. All 51 patients were re-examined three and twelve months later. The final follow-up was accomplished five years postoperatively.   Findings: 25 of the patients needed a shunt operation. One year after a shunt placement 72% of these patients had a good recovery concerning activities of daily living, 58% benefited in their urinary incontinence and 57% walked better. During the 5 years of follow-up 8 patients with shunt and 9 without shunt had died. Positive effect of shunting remained. Only one neuropsychological test, recognition of words test, distinguishes the patients with the need for a shunt. Simple mini mental examination test was not different in those who improved. In the postoperative follow-up patients with shunt showed no change in neuropsychological tests even if they were subjectively better. The infusion test was of no value in diagnosing NPH. The 16 patients with Alzheimer's disease did worse after one year than those without pathological changes, but the mortality was not increased.   Interpretation: Specific neuropsychological tests are of little value in diagnosing NPH. Mini-Mental status examination was neither of value in diagnosing NPH nor in prediction of the outcome. In this study the infusion test did not improve diagnostic accuracy of NPH, but shunt placement relieves urinary incontinence and walking disability in patients with increased ICP. The patients with positive Alzheimer diagnosis on biopsy did not improve. Published online June 20, 2002     

The use of a fiberoptic intracranial pressure monitor in clinical practice

Four years of clinical experience with a fiberoptic intracranial pressure monitor are presented. One hundred forty patients were monitored, of whom 80 had increased intracranial pressure. Of the patients with nontraumatic intracerebral hematoma and subarachnoid hemorrhage, 100% had increased pressure. Forty-seven of 69 patients with head injuries had elevated pressure; of these, 28 had pressure significant enough to require therapy. Both the patients with head injuries and those with nontraumatic hemorrhage were more effectively treated by using the results of pressure monitoring to determine when therapy was required and to indicate the response of the patient to that therapy. Despite the evidence, monitoring of intracranial pressure is not routine due to a lack of acceptance and effectiveness. To overcome such problems, a system must meet the criteria of ease of insertion, reliability, and lack of complications. These criteria are fulfilled by the fiberoptic system presented.     

Continuous cerebral compliance monitoring in severe head injury: its relationship with intracranial pressure and cerebral perfusion pressure

Summary Background. Cerebral compliance expresses the capability to buffer an intracranial volume increase while avoiding a rise in intracranial pressure (ICP). The autoregulatory response to Cerebral Perfusion Pressure (CPP) variation influences cerebral blood volume which is an important determinant of compliance. The direction of compliance change in relation to CPP variation is still under debate. The aim of the study was to investigate the relationship between CPP and compliance in traumatic brain injured (TBI) patients by a new method for continuous monitoring of intracranial compliance as used in neuro-intensive care (NICU).Method. Three European NICU’s standardised collection of CPP, compliance and ICP data to a joint database. Data were analyzed using an unpaired student t-test and a multi-level statistical model.Results. For each variable 108,263 minutes of data were recorded from 21 TBI patients (19 patients GCS≤8; 90% male; age 10–77 y). The average value for the following parameters were: ICP 15.1±8.9 mmHg, CPP 74.3±14 mmHg and compliance 0.68±0.3 ml/mmHg. ICP was ≥20 mmHg in 20% and CPP<60 mmHg for 10.7% of the time. Compliance was lower (0.51±0.34 ml/mmHg) at ICP≥20 than at ICP<20 mmHg (0.73±0.37 ml/mmHg) (p<0.0001). Compliance was significantly lower at CPP<60 than at CPP≥60 mmHg: 0.56±0.36 and 0.70±0.37 ml/mmHg respectively (p<0.0001). The CPP – compliance relationship was different when ICP was above 20 mmHg compared with below 20 mmHg. At ICP<20 mmHg compliance rose as CPP rose. At ICP≥20 mmHg, the relation curve was convexly shaped. At low CPP, the compliance was between 0.20 and 0.30 ml/mmHg. As the CPP reach 80 mmHg average compliance was 0.55 ml/mmHg., but compliance fell to 0.40 ml/mmHg when CPP was 100 mmHg.Conclusions. Low CPP levels are confirmed to be detrimental for intracranial compliance. Moreover, when ICP was pathological, indicating unstable intracranial equilibrium, a high CPP level was also associated with a low volume-buffering capacity.     

Intracranial pressure patterns after endoscopic third ventriculostomy. Preliminary experience

Summary. Background. Endoscopic Third Ventriculostomy (ETV) has become the treatment of choice for non-communicating hydrocephalus as it is able to couple high success rate (60–80%) with rare complications (about 5%). Nevertheless, which is the best postoperative care standard and whether or not it is possible to predict the success of the procedure is still discussed. Traditional neuro-imaging techniques show several limitations in the early postoperative period. Indeed, a decrease of the ventricular size is often minimal and not visible before three weeks, while, MRI visualization of a flow void signal through the third ventricle floor, seems to have a significant incidence of false positives. The use of postoperative ICP measurement after ETV has been suggested as a valid monitoring method, mostly in the early postoperative period. In previously unpublished data the authors observed the existence of different ICP patterns following ETV. This finding prompted the authors to search for a relationship among ICP patterns, stoma functioning and prediction of success.Method. At our institution 26 consecutive patients affected by obstructive triventricular hydrocephalus underwent ETV. Among them there were 11 primitive aqueductal stenosis (AS), 5 shunt malfunctions, 2 third ventricle mass, 3 intraventricular cysts, and 5 patients with different lesions (1 quadrigeminal cistern arachnoidal cyst, 1 pineal region mass, 2 tectal tumours, and 1 supracerebellar abscess) compressing the aqueduct of Sylvius from outside named ab estrinseco aqueductal stenosis. All patients underwent postoperative Intra Cranial Pressure (ICP) monitoring by means of a ventricular catheter.Findings. Transient ICP rises of any grade, mostly responsive to periodical liquoral subtractions, occurred shortly after ETV in as many as 50% of our patients. No major complications occurred. The effect of ETV on ICP trend was found to be variable among groups of patients thus identifying different ICP patterns. Patients with ab estrinseco Sylvian aqueduct compression showed the best effect on ICP, whilst, patients with intraventricular mass lesions causing triventricular hydrocephalus and shunt-dependent patients, revealed a clear trend to develop a more severe intracranial hypertension after ETV.Conclusions. Patients with shunt malfunction and patients with intraventricular mass lesions, showing a more pronounced trend to develop severe intracranial hypertension after ETV, should always be considered for postoperative ICP monitoring in order to detect and, eventually, treat any ICP rises which may occur. Unfortunately, it is still difficult to assign a predictive value to the different postoperative ICP patterns. The authors encourage postoperative ICP monitoring in all patients in order to define all the possible ICP patterns following ETV.