Continuous Intracranial Pressure Recordings Research Articles

Effects of caffeine on intracranial pressure and pain perception in freely moving rats.

Caffeine, a non-selective adenosine receptor (AR) antagonist, is the most consumed psychostimulant in the world. Caffeine has been suggested to regulate cerebrospinal fluid secretion and is known both to alleviate and to trigger headache; however, its effect on the regulation of intracranial pressure (ICP) is not known. Therefore, we aimed to investigate the effects of caffeine on ICP and nociceptive responses. Female Sprague-Dawley rats were implanted with a novel telemetric device for continuous ICP recordings, which allowed for continuous recordings in freely moving rats. A single dose of caffeine (30 or 120 mg/kg intraperitoneally) was given. In a second group (non-implanted), the acute effects of 30 mg/kg caffeine on periorbital threshold using Von Frey testing and spontaneous behavior were utilized using an automated behavioral registration platform (Laboratory, Animal, Behavior, Observation, Registration and Analysis System) in a randomized cross-over study. Quantitative polymerase chain reaction and immunofluorescence were used to localize ARs in the choroid plexus. A single dose of 30 mg/kg caffeine lowered the ICP by 35% at 165 min after administration (saline: 0.16 ± 0.9 vs caffeine: -1.18 ± 0.9 ΔmmHg, p = 0.0098) and lasted up to 12 h. Administration of 120 mg/kg caffeine showed a faster onset of decrease in ICP within 15 min by 50% (p = 0.0018) and lasted up to 12 h. The periorbital pain thresholds were higher after 1 h (saline: 224.6 ± 15.1 vs caffeine: 289.5 ± 8.7 g, p = 0.005) and lasted up to 5 h. Caffeine-treated rats had increased locomotor activity, speed, and changed grooming behavior. Expression of AR1 was found in the choroid plexus. This study demonstrates that caffeine has a lowering effect on ICP as an acute treatment. Interestingly, caffeine acutely caused an increased response in cephalic thresholds supporting hypoalgesic effects. Future studies investigating the beneficial effects of caffeine for elevated ICP are warranted.

Glucocorticoids modify intracranial pressure in freely moving rats

BackgroundGlucocorticoids (GCs) are widely prescribed for a variety of inflammatory diseases, but they are also used to treat raised intracranial pressure (ICP) caused by trauma or oedema. However, it is unclear if GCs independently modulate ICP and if GCs are involved in normal ICP regulation. In this study, we aimed to assess the ICP modulatory effects of GCs and their molecular consequences on choroid plexus (CP).MethodsAdult female rats were implanted with telemetric ICP probes for physiological, continuous ICP recordings in a freely moving setup. Rats received prednisolone or vehicle via oral gavage in a randomized acute (24 h) ICP study. In a subsequent study rats received corticosterone or vehicle in drinking water for a 4-week chronic ICP study. CP were removed, and the expression of genes associated with cerebrospinal fluid secretion were assessed.ResultsA single prednisolone dose reduced ICP by up to 48% (P < 0.0001), where ICP was reduced within 7 h and was maintained for at least 14 h. Prednisolone increases ICP spiking (P = 0.0075) while not altering ICP waveforms. Chronic corticosterone reduces ICP by up to 44%, where ICP was lower for the entirety of the 4-week ICP recording period (P = 0.0064). ICP daily periodicity was not altered by corticosterone. Corticosterone ICP reduction was not accompanied by ICP spike differences or alteration in ICP spike periodicity. Chronic corticosterone treatment had modest effects on CP gene expression, lowering the expression of Car2 at CP (P = 0.047).ConclusionsGCs reduce ICP in both the acute and chronic setting to a similar degree. Moreover, GCs did not modify the diurnal rhythm of ICP, suggesting the diurnal variation of ICP periodicity is not under explicit control of GCs. ICP disturbances should be considered a consequence of GC therapy. Based on these experiments, GCs may have broader ICP therapeutic uses, but side effects must be taken into consideration.

Long-term monitoring of intracranial pressure in freely-moving rats; impact of different physiological states

BackgroundElevated intracranial pressure (ICP) is observed in association with a range of brain disorders. There is limited insight into the regulatory mechanisms of ICP under physiological conditions, and consequently also under pathological conditions. Thereby, to understand the mechanisms underlying ICP dynamics, precise, valid and long-term ICP recordings are of importance in the preclinical setting. Herein, we used a novel telemetric system for ICP recordings which allowed for long-term recordings in freely-moving rats. The aim was to investigate ICP dynamics under different physiological states and investigate how factors such as surgery/recovery, body position, light–dark, co-housing, weight and anesthesia may influence ICP and its waveforms.MethodsA telemetric device was implanted epidurally in rats and signals were recorded continuously for up to 50 days (n = 14). Recording was divided into three experimental periods: a surgical recovery period (RP), a physiological period (PP) and an experimental period (EP). Histology was performed to study the morphology of implanted rats and non-implanted rats (n = 17).ResultsFor the first time, we can demonstrate continuous ICP recordings in freely-moving and co-housed rats for up to 50 days with a high degree of stability. The mean ICP in the recording periods were; RP: 3.2 ± 0.6 mmHg, PP: 5.0 ± 0.6 mmHg and EP: 4.7 ± 0.6 mmHg. In the RP, the ICP was significantly lower compared to the PP (P = 0.0034). Significant light–dark difference in ICP with 21% increase in respiratory slow-wave amplitude was observed in the co-housed animals but not in single-housed animals. The ICP signal was raised during the dark period relative to the light (Δ0.3 ± 0.07 mmHg, P = 0.0043). Administration of anesthesia gave a short-term increase in ICP followed by a significant decrease in ICP. No signs of tissue damage or inflammation were found in the implanted brains.ConclusionsICP dynamics were influenced by several factors such as, use of anesthesia, light–dark difference and housing conditions. Our study demonstrates the importance of performing ICP physiological measurements in freely-moving animals. This has significant implications for moving the preclinical research field forward in order to properly study ICP physiology during disease development and to explore drug targets for alleviating increased ICP.

Identifying causal relationships between EEG activity and intracranial pressure changes in neurocritical care patients

Objective. To explore and assess the relationship between electroencephalography (EEG) activity and intracranial pressure (ICP) in patients suffering from traumatic brain injury (TBI) and subarachnoid hemorrhage (SAH) during their stay in an intensive care unit. Approach. We performed an observational prospective cohort study of adult patients suffering from TBI or SAH. Continuous EEG-ECG was performed during ICP monitoring. In every patient, variables derived from the EEG were calculated and the Granger causality (GC) methodology was employed to assess whether, and in which direction, there is any relationship between EEG and ICP. Main results. One-thousand fifty-five hours of continuous multimodal monitoring were analyzed in 21 patients using the GC test. During 37.88% of the analyzed time, significant GC statistic was found in the direction from the EEG activity to the ICP, with typical lags of 25–50 s between them. When recordings were adjusted by sedation—perfusion and/or bolus—and handling, these percentages hardly changed. Significance. Long-lasting, continuous and simultaneous EEG and ICP recordings from TBI and SAH patients provide highly rich and useful information, which has allowed for uncovering a strong relationship between both signals. The use of this relationship could lead to developing a medical device to measure ICP in a non-invasive way.

Techniques and strategies in neurocritical care originating from Southern Scandinavia

To describe innovations in neurocritical care originating from university hospitals in southern Scandinavia over a period of 50 years. Several techniques and strategies that are now included in clinical routine were initially developed in southern Scandinavia: continuous recording of intracranial pressure, monitoring of cerebral blood flow, analyses of cerebral energy metabolism under physiological and pathological conditions, and intracerebral microdialysis with bedside biochemical analysis and display of data. This background and, in particular, knowledge of the physiological prerequisites for water transport across the blood-brain barrier and the regulation of brain volume constituted the basis for the "Lund Concept" for treatment of increased intracranial pressure. The development of neurocritical care has resulted in a dramatic decrease in mortality for patients with severe traumatic brain injury. The focus in the future may be on improved biochemical supervision at the bedside to avoid secondary episodes of ischaemia and to identify and treat secondary non-ischaemic mitochondrial dysfunction. As mortality has decreased, demand for qualified post-traumatic rehabilitation has increased. Further improvements will necessitate close cooperation between critical care physicians, neurosurgeons and specialists in rehabilitation medicine.

Steady-state indicators of the intracranial pressure dynamic system using geodesic distance of the ICP pulse waveform

Normal functioning of the brain depends on the homeostasis (∼ steady state) of its various physiological sub-systems, one of which is the intracranial pressure (ICP) dynamic system. The ICP dynamic system of an injured brain is susceptible to various acute changes that should ideally be detected by ICP monitoring even for comatose patients. However, the status quo of ICP monitoring solely targets mean ICP. We aimed to demonstrate a novel approach to detect acute deviation from steady state of an ICP dynamic system in an absence of significant mean ICP changes. We hypothesized that steady state of ICP dynamic systems is reflected as ICP pulses of similar mean ICP levels resembling each other for a given subject. A general framework was used to derive such a steady-state indicator that can accommodate different metrics of inter-pulse distance and different statistics of the distance histograms. In addition to conventional Euclidean distance and Pearson correlation, geodesic distance between pulses was introduced as a novel metric. These different ways of calculating steady-state indicators under the proposed framework were evaluated on three types of continuous ICP recordings: (1) those between two consecutive brain imaging studies that demonstrated acute ventricular enlargement for slit ventricle syndrome (SVS) patients undergoing a trial of shunt externalization and clamping (SVS+); (2) those between consecutive brain imaging studies from the SVS patients under the same trial but without ventricular enlargement (SVS−); (3) overnight recordings from normal pressure hydrocephalus (NPH) patients. It was observed that only the standard deviation of geodesic distance correctly differentiated between SVS+ and SVS− and between SVS+ and NPH while avoiding discriminating between SVS− and NPH. It was also found that 45% SVS+ cases had a multimodal geodesic distance histogram while none of SVS− and 3.8% of NPH cases had such a multimodal histogram. Pulses with a large number of distant pulses for the five multimodal-histogram SVS+ cases fell in short time windows indicating that acute ventricular changes may have occurred in these confined time windows during which no significant changes of mean ICP were observed. In contrast, the pulses with a large number of distant pulses for the two multimodal-histogram NPH cases did not cluster temporally. In conclusion, the geodesic inter-pulse distance is a promising metric to quantify distance intrinsic to the underneath geometric structure of ICP signals and hence is a more suitable way to derive a steady-state indicator of an ICP dynamic system.

Hypertonic saline more efficacious than mannitol in lethal intracranial hypertension model

Background: Medical management of brain edema and elevated intracranial pressure (ICP) is a crucial challenge in neurosurgical practice. Depending on the cause, the treatments for brain edema fall into three categories: stabilization of the blood-brain barrier, depletion of brain water and surgical decompression. Although mannitol is the mainstay of hyperosmolar therapy, hypertonic saline (HS) is emerging as an effective alternative to traditional osmotic agents.Methods: Experimental elevated ICP (50 mmHg) was induced in rabbits using an intracranial balloon. The effects of mannitol and HS (10% NaCl) were compared in this specific physiopathological model. Twelve animals were divided into three groups (control, HS and mannitol) according to intravenous administration of 0·9% NaCl, 10% NaCl or 20% mannitol 5 minutes after the elevation of ICP. The doses of 10% NaCl and 20% mannitol were iso-osmolar. During 90 minutes, continuous recording of ICP, mean arterial pressure (MAP) and cerebral perfusion pressure (CPP) was realized.Results: The control group had a median survival of only 53 minutes, significantly lower than the treated groups (p = 0·0002). There was statistical difference between mannitol and HS; the 10% NaCl group had lower values of ICP (p = 0·0116) and higher values of MAP (p<0·0001) and CPP (p<0·0001).Conclusion: The findings demonstrate higher efficacy of the 10% NaCl treatment in this comparison with 20% mannitol. Further efforts should be directed toward development of clinical studies using iso-osmotic doses of mannitol and HS in specific etiologies of intracranial hypertension.

Reactivity of Brain Tissue Oxygen to Change in Cerebral Perfusion Pressure in Head Injured Patients

It has been reported recently that correlation between brain tissue oxygen (PbtO2) and cerebral perfusion pressure (CPP) may serve as an indicator of cerebral autoregulation after subarachnoid hemorrhage. We aimed to compare similar indices describing interaction between changes in intracranial pressure (ICP), arterial blood pressure (ABP), and brain tissue oxygen to verify their clinical utility in patients after traumatic brain injury. Retrospective analysis of multimodal monitoring of 32 patients suffering from head injury, admitted in the Neurosciences Critical Care Unit, Addenbrooke's Hospital, Cambridge, UK. Initial 24 h intervals of continuous ABP, ICP, and PbtO2 recordings were analyzed. Index of tissue oxygen reactivity ORx was evaluated as the correlation coefficient between PbtO2 and CPP over a period of 60 min and compared to the index of pressure reactivity PRx. "Optimal CPP" and a hypothetical "optimal PbtO2" were defined as the ranges of CPP and PbtO2 at which PRx or ORx were indicating best cerebrovascular milieu. PRx and ORx mean values did not show any correlation with each other (R = 0.012; P = 0.95) between patients. There was also no correlation between ORx and PbtO2 (R = 0.098; P = 0.61) and between PRx and PbtO2 (R = 0.019; P = 0.923). No clear and consistent value of "optimal CPP" minimizing ORx or of hypothetical "optimal PbtO2" were found analyzing PbtO2 or ORx trend over the 24 h of monitoring. However, in most of patients 'optimal CPP' has been found for PRx index. The same has been confirmed when the data from whole monitoring period were analyzed. There was no correlation between values of 'optimal CPP' assessed using ORx and 'optimal CPP' assessed with PRx. The relationships between PbtO2, ORx, and CPP in head injury appear less useful than reported before for patients after subarachnoid hemorrhage.

Morphological Clustering and Analysis of Continuous Intracranial Pressure

The continuous measurement of intracranial pressure (ICP) is an important and established clinical tool that is used in the management of many neurosurgical disorders such as traumatic brain injury. Only mean ICP information is used currently in the prevailing clinical practice, ignoring the useful information in ICP pulse waveform that can be continuously acquired and is potentially useful for forecasting intracranial and cerebrovascular pathophysiological changes. The present study introduces and validates an algorithm of performing automated analysis of continuous ICP pulse waveform. This algorithm is capable of enhancing ICP signal quality, recognizing nonartifactual ICP pulses, and optimally designating the three well-established subcomponents in an ICP pulse. Validation of the proposed algorithm is done by comparing nonartifactual pulse recognition and peak designation results from a human observer with those from automated analysis based on a large signal database built from 700 h of recordings from 66 neurosurgical patients. An accuracy of 97.84% is achieved in recognizing nonartifactual ICP pulses. An accuracy of 90.17%, 87.56%, and 86.53% was obtained for designating each of the three established ICP subpeaks. These results show that the proposed algorithm can be reliably applied to process continuous ICP recordings from real clinical environment to extract useful morphological features of ICP pulses.

Assessment of Quality of Continuous Intracranial Pressure Recordings in Children

Background: Bad quality of continuous intracranial pressure (ICP) recordings may potentially give wrong diagnostic information. Method: This study examined the ICP recordings of 33 children undergoing ICP monitoring during a 12-month period. Their ICP recordings were stored as raw data files and analyzed retrospectively. An automatic algorithm applied to every subsequent 6-second time window of each recording assessed the quality of ICP recordings. Time windows containing 4–18 cardiac beat-induced single ICP waves were accepted; time windows containing artifact-induced pressure waves due to noise in the signal were rejected. For every ICP recording, the number of accepted and rejected time windows were determined. In addition, the raw data ICP signal was assessed by visual inspection to verify the automatic algorithm. Two methods of computing mean pressure of a time window are compared; mean ICP was either computed according to current practice independent of the presence or absence of single ICP waves or computed only for single ICP waves within the time window (mean_SW ICP). Results:In 4 of the 33 patients (12%), more than 70% of the time windows of their ICP recordings were rejected; in 3 patients 95–100% of time windows were rejected. Visual inspection of the raw ICP signals confirmed the absence of single ICP waves. In these cases, computing mean_SW ICP, not by mean ICP, revealed the bad signal quality. Conclusions: This retrospective study showed that in 3 of 33 patients (9%) the quality of the ICP recordings was so bad that they gave wrong diagnostic information. One way of obtaining quality control is to compute mean_SW ICP, determined only for cardiac beat-induced single ICP waves within a time window.

Normal pressure hydrocephalus: survey on contemporary diagnostic algorithms and therapeutic decision-making in clinical practice.

There is no agreement on the best diagnostic criteria for selecting patients with normal pressure hydrocephalus (NPH) for CSF shunting. The primary objective of the present study was to provide a contemporary survey on diagnostic algorithms and therapeutic decision-making in clinical practice. The secondary objective was to estimate the incidence of NPH. Standardized questionnaires with sections on the incidence of NPH and the frequency of shunting, evaluation of clinical symptoms, and signs, diagnostic studies, therapeutic decision-making and operative techniques, postoperative outcome and complications, and the profiles of different centers, were sent to 82 neurosurgical centers in Germany known to participate in the care of patients with NPH. Data were analyzed from 49 of 53 centers which responded to the survey (65%). The estimated annual incidence of NPH was 1.8 cases/100.000 inhabitants. Gait disturbance was defined as the most important sign of NPH (61%). There was a wide variety in the choice of diagnostic tests. Cisternography was performed routinely only in single centers. Diagnostic CSF removal was used with varying frequency by all centers except one, but the amount of CSF removed by lumbar puncture differed markedly between centers. There was poor agreement on criteria for evaluation of continuous intracranial pressure recordings regarding both the amplitude and the relative frequency of B-waves. Both periventricular and deep white matter lesions were present in about 50% of patients being shunted, indicating that vascular comorbidity in NPH patients has gained more acceptance. Programmable shunts were used by more than half of the centers, and newer valve types such as gravitational valves have become more popular. According to the present survey, new diagnostic and therapeutic concepts on NPH have penetrated daily routine to a certain extent. Wide variability, however, still exists among different neurosurgical centers.

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

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. 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. 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%). Outcome after the 2nd ICP monitoring was more reliably predicted by computing differences in numbers of ICP elevations than by calculation of mean ICP.

Quantitative analysis of continuous intracranial pressure recordings in symptomatic patients with extracranial shunts

Objectives: To explore the outcome of management of possible shunt related symptoms using intracranial pressure (ICP) monitoring, and to identify potential methodological limitations with the current strategies of ICP assessment....

Assessment of Continuous Intracranial Pressure Recordings in Childhood Craniosynostosis

In this study, we explored two strategies of assessing continuous intracranial pressure (ICP) recordings in children with craniosynostosis, namely either by computation of the mean ICP or by computation of the accurate numbers of ICP elevations of different durations. The ICP recordings of 121 consecutive patients with a tentative diagnosis of craniosynostosis who underwent continuous ICP monitoring were examined. The relationship between mean ICP and numbers of ICP elevations was defined. The distribution of numbers of ICP elevations between patients either undergoing surgery or conservative treatment was also compared, since the choice of treatment was heavily dependent on the results of ICP monitoring. At the time of ICP monitoring, calculation of mean ICP was the main parameter for assessment of ICP curves. After a median observation period of 16 months, the ICP curves were reexamined by means of the software Sensometrics^TM Pressure Analyser, which presents the ICP curve as a matrix of numbers of ICP elevations of different levels (20–40 mm Hg) and durations (0.5– 20 min). Since the recording period differed between the cases, the numbers were standardized to a given recording time of 10 h, to allow for comparisons between patients. Cases with a borderline mean ICP during sleep (mean ICP 10–15 mm Hg) constituted 40.5% of the 121 patients. In this group, a rather weak relationship between mean ICP and the number of ICP elevations above 20 mm Hg was found, as well as a relatively high number of ICP elevations above 20 mm Hg of various durations. As compared to the patients undergoing surgery, a rather high number of ICP elevations above 20 mm Hg of various durations was found in patients undergoing conservative treatment. The study confirmed our hypothesis that in children with craniosynostosis, calculation of mean ICP does not describe the ICP curve in a reliable way. Decision-making should also include the computation of the distribution of numbers of ICP elevations, since this procedure represents a more sensitive strategy of detecting intracranial hypertension.

A Ventricular Infusion Technique for the Evaluation of Treated and Untreated Hydrocephalus

Abstract Patients considered to have a possible disorder of the circulation of the cerebrospinal fluid (CSF) were prospectively randomized on clinical and computed tomographic grounds into one of four categories: low probability of a disorder of circulation of the CSF (n = 14); high probability of a disorder of the circulation of the CSF (n = 10); low probability of shunt malfunction (n = 10); and high probability of shunt malfunction (n = 9). Patients with possible disorders of the circulation of the CSF who did not meet the entry criteria for each of these categories were excluded from this study. A ventricular catheter connected to a subgaleal Rickham reservoir not in continuity with a shunt system (if this was present) either was inserted into each patient or was in place from previous surgery. Infusion studies were conducted by the infusion of 1 ml/min of normal saline through a 25-gauge needle inserted through the skin into the Rickham reservoir. A separate 25-gage needle was inserted into the Rickham reservoir for continuous recording of intracranial pressure. There were 43 infusion studies that were included in the four categories. Recordings of baseline intracranial pressure for a high probability of a disorder of the circulation of the CSF did not differ significantly from a low probability of a disorder of the circulation of the CSF. Baseline intracranial pressure for a high probability of shunt malfunction was significantly higher than the low probability of a disorder of the circulation of the CSF group and the low probability of shunt malfunction group; there was, however, marked overlap in values between these groups. On the other hand, resistance to infusion was no greater than 12 mm Hg ml-1/min-1for all patients with a low probability of a disorder of the circulation of the CSF and no less than 14 mm Hg ml-1/min-1in both the high probability of a disorder of the circulation of the CSF and the high probability of shunt malfunction. This result was significant. The results indicate that this test, which may be applied in an outpatient setting, could be a practical and useful addition to the current methods of the assessment of the circulation of the CSF.

PLATEAU-WAVE PHENOMENON (II)

From 1980 to 1989, during intracranial pressure (ICP) recording, brain herniation (central transtentorial herniation associated with uncal herniation) developed in 15 patients as a result of aneurysmal rebleeding, uncontrollable brain swelling and/or oedema in spite of attempts at treating increased ICP. The relationship between the ICP level at which herniation occurred and the ICP fluctuation patterns in continuous ICP recordings prior to the development of the herniation was studied retrospectively. As for the ICP fluctuation patterns, the patients were assigned to 2 groups on the basis of the presence or abscence of plateau waves of Lundberg: group I comprising 8 patients without plateau waves but with a high ICP, and group II comprising 7 patients with both plateau waves and a high ICP. In the group I patients the herniation occurred as a result of aneurysmal rebleeding or brain swelling after subarachnoid haemorrhage, and in the group II patients the herniation resulted from brain tumour, meningitis carcinomatosa and superior sagittal sinus thrombosis. In the group I patients the herniation developed at a mean ICP level of 70-98 mmHg, and in the group II patients it occurred at a mean ICP level of 120-150 mmHg, far higher than the ICP level causing herniation in the group I patients. It has been shown that patients with a plateau-wave phenomenon in continuous ICP recordings have a marked impairment of cerebrospinal fluid (CSF) absorption and a delayed CSF flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Benign Intracranial Hypertension treated with Ventriculoperitoneal Shunting

A 59-year-old woman complained of headaches and vomiting. On admission, neurological examination revealed bilateral choked disc and tendon hyper-reflexia. Lumbar puncture showed a high opening cerebrospinal fluid (CSF) pressure (195 mmH2O) ; however, protein and sugar levels were normal. The CSF was clear and watery. Computed tomography showed that the bilateral white matter was of low density and the ventricles were compressed bilaterally. Intracranial pressure (ICP), measured continuously by means of a ventricular tube, ranged from 20 to 40 mmHg. The ICP record showed typical A waves and, when an A wave was observed, the patient simultaneously lost consciousness. From these data, the diagnosis of benign intracranial hypertension was established. Intravenous glycerol administration during ICP recording produced only a temporary decrease in ICP. Ventricular external drainage, however, was continuously effective. After a ventriculoperitoneal shunt had been emplaced, the patient recovered. In this case, continuous ICP recording was very useful in both the diagnosis of benign intracranial hypertension and evaluation of its treatment. Shunting is an effective treatment for this disease.

Brain blood volume and blood flow in patients with plateau waves.

Plateau waves, characterized by acute transient rises of the intracranial pressure (ICP), are accompanied by a marked decrease of the cerebral perfusion pressure. Patients with plateau waves, however, often show no clinical symptoms of ischemia of the brain stem, such as vasopressor response or impairment of consciousness during the waves. The authors studied brain blood volume and blood flow with dynamic computerized tomography using rapid-sequence scanning in patients with plateau waves identified during continuous ICP recording. Following an intravenous bolus injection of contrast medium, density-versus-time curves were obtained for the regions of interest; that is, the frontal lobe, the temporal lobe, the caudate nucleus, the putamen, and the pons. The dynamic studies were undertaken when the ICP was high during a plateau-wave phase and when it was low during an interval phase between two plateau waves. The results indicate that, in the cerebral hemisphere (frontal lobe, temporal lobe, caudate nucleus, and putamen), plateau waves were accompanied by an increase in blood volume and, at the same time, a decrease in blood flow. In the pons, however, both the blood volume and blood flow showed little change during plateau waves as compared with the intervals between two plateau waves. These observations may explain why there is no rise in the systemic blood pressure and why patients are often alert during plateau waves.

ICP patterns and isotope cisternography in patients with communicating hydrocephalus following rupture of intracranial aneurysm

Intracranial pressure (ICP) was continuously recorded, isotope cisternography was performed, and the ventricular system size was evaluated on serial computerized tomography scans in 39 patients. All of these patients had communicating hydrocephalus after subarachnoid hemorrhage (SAH) from rupture of an intracranial aneurysm. The studies were carried out in both the acute stage (within 7 days after SAH) and the communicating hydrocephalus stage. In patients in the acute stage who had no ventricular dilatation, but who later developed communicating hydrocephalus, the resting ICP was high, and an ICP pattern of B-wave activity was seen; there was no delay in cerebrospinal fluid (CSF) absorption on isotope cisternography. Patients with communicating hydrocephalus in whom ICP recordings were started within 63 days after SAH had a pattern of plateau waves in conjunction with B-waves, and there was a marked delay in CSF circulation. In general, patients with higher resting ICP's had more frequent ICP irregularities. Patients with communicating hydrocephalus in whom recordings were begun more than 6 months after SAH had a low and flat ICP pattern, and there was no delay in CSF absorption in spite of bilateral convexity blocks on isotope cisternography. The results suggest that the ICP pattern of plateau waves in conjunction with B-waves can be regarded as a sign of delayed CSF absorption; hence, shunting procedures may be indicated in patients with plateau waves in conjunction with B-waves visualized on continuous ICP recordings.

Changes in intracranial pressure associated with delayed cerebral radionecrosis

Continuous recording of intracranial pressure (ICP) from one lateral ventricle in a case of histologically proven delayed temporal radionecrosis due to previous irradiation of the pituitary gland for the treatment of an adiposity of the Cushing type has revealed the occurrence of B-waves and ramplike waves despite the absence of raised intracranial pressure. Ventriculo-atrial shunting failed to relieve the severe psychic symptomatology, which was due to direct tissue damage. These observations indicate that B-waves may have a neurogenic origin.