Intracranial pressure wave morphological classification: automated analysis and clinical validation.

BACKGROUND: Recently, different software has been developed to automatically analyze multiple intracranial pressure (ICP) parameters, but the suggested methods are frequently complex and have no clinical correlation. The objective of this study was to assess the clinical value of a new morphological classification of the cerebrospinal fluid pulse pressure waveform (CSFPPW), comparing it to the elastance index (EI) and CSF-outflow resistance (Rout), and to test the efficacy of an automatic ICP analysis. METHODS: An artificial neural network (ANN) was trained to classify 60 CSFPPWs in four different classes, according to their morphology, and its efficacy was compared to an expert examiner's classification. The morphology of CSFPPW, recorded in 60 patients at baseline, was compared to EI and Rout calculated at the end of an intraventricular infusion test to validate the utility of the proposed classification in patients' clinical evaluation. RESULTS: The overall concordance in CSFPPW classification between the expert examiner and the ANN was 88.3 %. An elevation of EI was statistically related to morphological class' progression. All patients showing pathological baseline CSFPPW (class IV) revealed an alteration of CSF hydrodynamics at the end of their infusion test. CONCLUSIONS: The proposed morphological classification estimates the global ICP wave and its ability to reflect or predict an alteration in CSF hydrodynamics. An ANN can be trained to efficiently recognize four different CSF wave morphologies. This classification seems helpful and accurate for diagnostic use.

Blood flow velocities during experimental intracranial hypertension in pigs.

OBJECTIVES: A purely hydraulic mechanism consisting in the pulsatile cuff-compression effect, by the cerebrospinal fluid displacement induced by the arterial pulsation, on the final portion of the bridging veins, has recently been hypothesized. This mechanism is able to maintain the constancy of cerebral blood flow (CBF) within the autoregulatory range, thus implying an exact balance between arterial inflow and venous outflow. In this study, we correlated arterial inflow and venous outflow during an experimentally induced condition of intracranial hypertension in pigs. METHODS: Mock cerebrospinal fluid (CSF) was progressively infused until a condition of brain tamponade was reached. Blood flow velocities at middle cerebral artery and sagittal sinus sites were evaluated simultaneously. RESULTS: Mean intracranial arterial blood flow velocity (IABFV), mean sagittal sinus blood flow velocity (SSBFV), and pulsatile-IABFV remained almost constant until cerebral perfusion pressure (CPP) dropped below 60-70 mmHg; then, a progressive decrease in mean IABFV and SSBFV, together with an increase in pulsatile-IABFV, was evident. CONCLUSION: The strict similarity between mean IABFV and SSBFV patterns suggests that CBF decrement is mainly due to a decrease in the venous outflow, which, in turn, produces an obstacle to the arterial inflow. The correspondent increase in pulsatile-IABFV confirms the presence of a distal outflow obstruction. All these findings point towards a purely hydraulic mechanism underlying the cerebral autoregulation which acts at the level of the so-called Starling resistor.

An experimental study on artificially induced CSF pulse waveform morphological modifications.

OBJECTIVE: The analysis of cerebrospinal fluid (CSF) pulse pressure waveform has been considered as a reliable method to investigate the intracranial system (ICS) dynamics. We have examined the morphological changes of the CSF pulse wave and of the sagittal sinus pressure (SSP) wave during a progressive increase in intracranial pressure (ICP) in order to investigate the ICS dynamics. METHODS: Four dogs were anesthetized. Blood pressure, ICP, and SSP were simultaneously recorded. Two vertical tubes were inserted inside one lateral ventricle, thus allowing the half-opening (one tube open) and opening (both tubes open) of the ICS. ICP was modified by varying the height of the liquid column into the tubes. Pressures were analyzed by applying the fast Fourier transformation on each pulse pressure wave. We distinguished two peaks (first and second peaks) and a notch in each pulse pressure wave. The pressure was raised from resting pressure up to 50 mmHg. RESULTS: A progressive and distinct change in the CSF pulse pressure shape was evident when opening the ICS to the atmosphere: a reduction in the height of the dicrotic notch and in the amplitude of the second peak and a corresponding positive shift of the first harmonic with respect to the onset of the CSF pulse pressure wave. DISCUSSION: A decrease in the amplitude of the CSF pulse waveform second peak and a positive phase shift of its first harmonic indicate an opening of the ICS to the atmosphere, i.e. an increase in the intracranial compliance.

Selection of patients with idiopathic normal-pressure hydrocephalus for shunt placement: a single-institution experience.

OBJECT: The ability to predict outcome after shunt placement in patients with idiopathic normal-pressure hydrocephalus (NPH) represents a challenge. To date, no single diagnostic tool or combination of tools has proved capable of reliably predicting whether the condition of a patient with suspected NPH will improve after a shunting procedure. In this paper, the authors report their experience with 120 patients with the goal of identifying CSF hydrodynamics criteria capable of selecting patients with idiopathic NPH. Specifically, they focused on the comparison between CSF-outflow resistance (R-out) and intracranial elastance (IE). METHODS: Between January 1977 and December 2005, 120 patients in whom idiopathic NPH had been diagnosed (on the basis of clinical findings and imaging) underwent CSF hydrodynamics evaluation based on an intraventricular infusion test. Ninety-six patients underwent CSF shunt placement: 32 between 1977 and 1989 (Group I) on the basis of purely clinical and radiological criteria; 44 between 1990 and 2002 (Group II) on the basis of the same criteria as Group I and because they had an IE slope > 0.25; and 20 between 2003 and 2005 (Group III) on the basis of the same criteria as Group II but with an IE slope > or = 0.30. Outcomes were evaluated by means of both Stein-Langfitt and Larsson scores. Patients' conditions were considered improved when there was a stable decrease (at 6- and 12-month follow-up) of at least 1 point in the Stein-Langfitt score and 2 points in the Larsson score. RESULTS: Group I: while no statistically significant difference in mean R-out value between improved and unimproved cases was observed, a clear-cut IE slope value of 0.25 differentiated very sharply between unimproved and improved cases. Group II: R-out values in the 2 unimproved cases were 20 and 47 mm Hg/ml/min, respectively. The mean IE slope in the improved cases was 0.56 (range 0.30-1.4), while the IE slopes in the 2 unimproved cases were 0.26 and 0.27. Group III: the mean IE slope was 0.51 (range 0.31-0.7). The conditions of all patients improved after shunting. A significant reduction of the Evans ratio was observed in 34 (40.5%) of the 84 improved cases and in none of the unimproved cases. CONCLUSIONS: Our strategy based on the analysis of CSF pulse pressure parameters seems to have a great accuracy in predicting surgical outcome in clinical practice.

Prolonged intracranial pressure (ICP) monitoring in non-traumatic pediatric neurosurgical diseases.

BACKGROUND: A limited number of studies have addressed the methods, indications and particular problems that may occur when programming prolonged intracranial pressure (ICP) monitoring in pediatric patients. Parenchymal fiberoptic transducers have been shown to give reliable ICP readings; moreover, they present a relatively low rate of complications, are easily placed and, as they are solid state, they are not subject to obstruction. MATERIAL/METHODS: A recently developed fiberoptic ICP transducer (Codman intraparenchymal sensor) was used to continuously monitor intracranial pressure in seventy children with non-traumatic neurosurgical diseases. The admitting diagnoses were hydrocephalus or shunt-related problems in 33 cases, single-suture (5 cases) or complex (16 cases) craniosynostosis in 21 patients, and sylvian scissure arachnoid cyst (SAC) in 16 cases. A software (ICP monitoring release) designed in our department was used for ICP recording storage and analysis. RESULTS: Raised ICP values were found in six of the seventeen patients with a suspected active hydyrocephalus, 24% of children with non-syndromic craniosynostosis, 52.8% of syndromic craniosynostosis patients, 50% or the children with a Type 11 SAC and two of the three patients with Type II SAC. CONCLUSIONS: Overall, prolonged ICP monitoring proved to be extremely useful in guiding surgical indications. The fiberoptic device used in our unit was shown to be reliable and associated with a relatively low rate of complications. Finally, the software allowed easy review and analysis of the obtained data.

Prolonged ICP monitoring in Sylvian arachnoid cysts.

BACKGROUND: The decision making process for patients with Sylvian fissure arachnoid cysts still represents a challenge for the neurosurgeon. A high percentage of patients are indeed asymptomatic, despite neuroimaging signs of apparently increased intracranial pressure (ICP). The present study was conducted to evaluate the usefulness of prolonged ICP recording in the preoperative work-up. METHODS: Eleven children (10 M/1 F) harboring temporal arachnoid cysts were investigated (mean age: 5.9 years). According to Galassi classification they were subdivided in three groups. Group I was made up of three patients with Type I cysts; Group II comprised six children with Type II cysts; Group III consisted of two children with Type III cysts. An extensible silicone microprocessor (Codman), developed for continuous ICP recording, was implanted intraparenchymally, adjacent to the major extension of the cyst. The collected information was cable unloaded to a PC and stored. All the patients underwent a minimum of 48 hours to a maximum of 72 hours of ICP continuous check. In resting conditions, 10 mm Hg was arbitrarily chosen as the upper normal limit of ICP, and the patients were classified according to the percentile distribution of their ICP daily and nightly pressure values. RESULTS: ICP recordings were in the normal range in all the three children with Type I cysts (49-86%< 10 mm Hg during the entire recording), despite the fact that two of them were apparently symptomatic. Three of the six children with a Type II temporal cyst had elevated ICP values (69-99%> 10 mm Hg), even though they had an incidental (1 case) or prenatal (2 cases) diagnosis. The remaining three patients had normal ICP values for more than 70% of the recording time period. The two patients with type III temporal arachnoid cysts had almost constantly abnormal ICP values (95-99%> 10 mm Hg). Five patients were operated; in four of them the surgical indication was based on ICP recordings (two of the three children with a Type II cyst and increased ICP and the two patients with a Type III cyst). The last child, harboring a Type I cyst, was operated upon parents' request, as a preventive measure. At a mean follow-up of 9.3 months all the patients operated on are in excellent clinical condition; one of them (Type II cyst) initially undergoing a craniotomy and cystic membrane excision required a subduro-peritoneal shunt implant 3 months after surgery for a symptomatic subdural hygroma on the side of the cyst. Postoperative computed tomography showed signs of brain expansion in the two patients operated on for a Type III cyst, and in the patient operated on for a Type I cyst. CONCLUSIONS: With the limit of the relatively small series presented here, prolonged ICP recording appeared to be an important preoperative tool to rule out the necessity of operating on children with Type I cysts. Furthermore, the study confirmed that an increase of the ICP is almost constantly present in children with Type III cysts. In cases of Type II lesions, the study results were less discriminating, though the ICP monitoring contributed in identifying those patients in whom surgery was indicated despite the absence of symptoms.