Cerebrospinal Fluid Pulse Pressure Research Articles

Compromised Cranio-Spinal Suspension in Chiari Malformation Type 1: A Potential Role as Secondary Pathophysiology.

In Chiari Malformation Type I (CM1), low-lying tonsils obstruct the cisterna magna at the foramen magnum, thereby compromising the essential juncture between the cranial and spinal compartments. The anatomical obstruction of the cisterna magna inhibits bi-directional CSF flow as well as CSF pulse pressure equilibration between the intracranial compartment and the intraspinal compartment in response to instances of increased intracranial pressure. Less understood, however, are the roles of the spinal cord suspension structures at the craniocervical junction which lend viscoelastic support to the spinal cord and tonsils, as well as maintain the anatomical integrity of the cisterna magna and the dura. These include extradural ligaments including the myodural bridges (MDBs), as well as intradural dentate ligaments and the arachnoid framework. We propose that when these elements are disrupted by the cisterna magna obstruction, tonsillar pathology, and altered CSF dynamics, there may arise a secondary pathophysiology of compromised and dysfunctional cranio-spinal suspension in CM1. We present intraoperative images and videos captured during surgical exposure of the craniocervical junction in CM1 to illustrate this proposal.

The historic evolution of intracranial pressure and cerebrospinal fluid pulse pressure concepts: Two centuries of challenges.

Background: There is a consensus on the importance of monitoring intracranial pressure (ICP) during neurosurgery, and this monitoring reduces mortality during procedures. Current knowledge of ICP and cerebrospinal fluid pulse pressure has been built thanks to more than two centuries of research on brain dynamics.Methods: Articles and books were selected using the descriptors “ICP,” “cerebrospinal fluid pulse,” “monitoring,” “Monro-Kellie doctrine,” and “ICP waveform” in electronic databases PubMed, Lilacs, Science Direct, and EMBASE.Results: Several anatomists and physiologists have helped clarify the patterns of intracranial volumes under normal and pathological conditions. Monro-Kellie doctrine was an important step in a story that is reconstructed in this article. Through documentary research, we report the contribution of important medical figures, such as Monro, Kellie, Abercrombie, Burrows, Cushing, Langfitt, Marmarou, and other physiologists and anatomists who left their marks on the history of Medicine.Conclusion: Understanding intracranial dynamics is an unfinished historical construction. Current knowledge is the result of two centuries of research that began with the investigations of Alexander Monro secundus.

Characteristics of the cerebrospinal fluid pressure waveform and craniospinal compliance in idiopathic intracranial hypertension subjects

BackgroundIdiopathic intracranial hypertension (IIH) is a condition of abnormally high intracranial pressure with an unknown etiology. The objective of this study is to characterize craniospinal compliance and measure the cerebrospinal fluid (CSF) pressure waveform as CSF is passively drained during a diagnostic and therapeutic lumbar puncture (LP) in IIH.MethodsEighteen subjects who met the Modified Dandy Criteria, including papilledema and visual field loss, received an ultrasound guided LP where CSF pressure (CSFP) was recorded at each increment of CSF removal. Joinpoint regression models were used to calculate compliance from CSF pressure and the corresponding volume removed at each increment for each subject. Twelve subjects had their CSFP waveform recorded with an electronic transducer. Body mass index, mean CSFP, and cerebral perfusion pressure (CPP) were also calculated. T-tests were used to compare measurements, and correlations were performed between parameters.ResultsCerebrospinal fluid pressure, CSFP pulse amplitude (CPA), and CPP were found to be significantly different (p < 0.05) before and after the LP. CSFP and CPA decreased after the LP, while CPP increased. The craniospinal compliance significantly increased (p < 0.05) post-LP. CPA and CSFP were significantly positively correlated.ConclusionsBoth low craniospinal compliance (at high CSFP) and high craniospinal compliance (at low CSFP) regions were determined. The CSFP waveform morphology in IIH was characterized and CPA was found to be positively correlated to the magnitude of CSFP. Future studies will investigate how craniospinal compliance may correlate to symptoms and/or response to therapy in IIH subjects.

Is There a Link Between ICP-Derived Infusion Test Parameters and Outcome After Shunting in Normal Pressure Hydrocephalus?

The term "hydrocephalus" encompasses a range of disorders characterised by clinical symptoms, abnormal brain imaging and derangement of cerebrospinal fluid (CSF) dynamics. The ability to elucidate which patients would benefit from CSF diversion (a shunt or third ventriculostomy) is often unclear. Similar difficulties are encountered in shunted patients to predict the scope for improvement by shunt re-adjustment or revision. We compared retrospective pre-shunting infusion test results performed in 310 adult patients diagnosed with normal pressure hydrocephalus (NPH) and their improvement after shunting. Resistance to CSF outflow correlated significantly with improvement (p < 0.05). Other markers known from the literature, such as amplitude in CSF pulse pressure, the slope of the amplitude-pressure regression line, or elasticity did not show any correlation with outcome. Outcome following shunting in adult NPH is associated with resistance to CSF outflow; however, the latter cannot be taken as an absolute predictor of shunt response.

Retinal venous pulsation: Expanding our understanding and use of this enigmatic phenomenon.

Retinal vein pulsation was first noted soon after the invention of the ophthalmoscope 170 years ago and was seen to change with cerebrospinal fluid pressure (CSFP) variation in the 1920s. The classical explanation for vein pulsation was that the cardiac cycle induced systolic peak in intraocular pressure (IOP) tended to intermittently collapse the retinal vein close to its exit in the central optic disk, causing pulsation to be counter-phase to IOP. Recently, improved ophthalmodynamometry and video recording techniques have allowed us to explore the fundamentals of retinal vein pulsation. This demonstrates that retinal venous collapse is in phase with both IOP and CSFP diastole, indicating the dependence upon CSFP pulse. We describe in some detail the mathematical and physical models of Starling resistors and how their results can be applied to understand the physiology of retinal vein pulsation. We discuss various techniques for measuring retinal venous pulsation, including a novel modified photo-plethysmographic technique developed in our laboratory. With these techniques, non-invasive measurement of CSFP is beginning to look feasible. Venous pulsation properties also have significant prognostic value in predicting long-term outcomes for both glaucoma and central retinal vein occlusion, as well as utility in other retinal vasculopathies and orbital disease. We demonstrate the potential use of modified photo-plethysmographic images in assessing these various disorders. A revised understanding of retinal vein pulse wave transmission along with improved measurement techniques may generate useful clinical tools for assessing these disorders.

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

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. 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. 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. 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.

Intracranial pulsatility is associated with regional brain volume in elderly individuals

Excessive intracranial pulsatility is thought to damage the cerebral microcirculation, causing cognitive decline in elderly individuals. We investigated relationships between brain structure and measures related to intracranial pulsatility among healthy elderly. Thirty-seven stroke-free, non-demented individuals (62–82 years of age) were included. We assessed brain structure, invasively measured cerebrospinal fluid (CSF) pulse pressure, and magnetic resonance–quantified arterial and CSF flow pulsatility, as well as arterial pulse pressure. Using both multivariate partial least squares and ordinary regression analyses, we identified a significant pattern of negative relationships between the volume of several brain regions and measures of intracranial pulsatility. The strongest relationships concerned the temporal lobe cortex and hippocampus. These findings were also coherent with observations of positive relationships between intracranial pulsatility and ventricular volume. In conclusion, elderly subjects with high intracranial pulsatility display smaller brain volume and larger ventricles, supporting the notion that excessive cerebral arterial pulsatility harms the brain. This calls for research investigating altered intracranial cardiac-related pulsatile stress as a potential risk factor that may cause or worsen the prognosis in subjects developing cognitive impairment and dementia.

Syringomyelia and tethered cord in children

The presence of syringomyelia varies in patients with different forms of dysraphism; from 21 % to 67 %. Only around 60% of patients with syringomyelia is likely to experience symptoms related to it. Many theories have been outlined for the creation of syringomyelia. The one most applicable to tethered cord dictates that tensile radial stress may create a syrinx in a previously normal cord tissue and transiently lower pressure may draw in interstitial fluid, causing the syrinx to enlarge if fluid exit is inhibited. In addition, arachnoiditis increases flow resistance in the spinal subarachnoid space, altering temporal CSF pulse pressure dynamics, which promotes entry of CSF in to the spinal cord. There is a significant overlap between the symptoms that are due to tethered cord and syringomyelia, both in newly presenting patients with coexisting syringomyelia, and in previously treated patients who during follow-up present recurrent symptoms and a new syringomyelia cavity. The treatment of patients with tethered cord and syringomyelia is directed towards untethering the cord from its most caudal region upwards and restoring spinal anatomy with reestablishment of unobstructed CSF flow in the subarachnoid space. Only if complete untethering has been ensured and syringomyelia deteriorates, then surgical treatment can be directed against the syrinx. In patients with spinal dysraphism and coexisting hydrocephalus, radiological presentation of new syringomyelia or deterioration of previously known syringomyelia may signify shunt obstruction "until proven otherwise". In most occasions, satisfactory cord untethering addresses the development of syringomyelia.

The Pressure Distribution of Cerebrospinal Fluid Responds to Residual Compression and Decompression in an Animal Model of Acute Spinal Cord Injury

In vivo large animal (pig) model study of cerebrospinal fluid (CSF) pressures after acute experimental spinal cord injury (SCI). To determine how the CSF pressure (CSFP) and CSF pulse pressure amplitude (CSFPPA) cranial and caudal to the injury site change after an acute SCI with subsequent thecal occlusion and decompression. Lowering intrathecal pressure via CSF drainage is currently instituted to prevent ischemia-induced SCI during thoracoabdominal aortic aneurysm surgery and was recently investigated as a potential intervention for acute traumatic SCI. However, in SCI patients, persistent extradural compression commonly occludes the subarachnoid space. This may generate a CSFP differential across the injury site, which cannot be appreciated with lumbar catheter pressure measurements. Anesthetized pigs were subjected to an acute contusive SCI at T11 and 8 hours of sustained compression (n = 12), or sham surgery (n = 2). CSFP was measured cranial and caudal to the injury site, using miniature pressure transducers, during compression and for 6 hours after decompression. The cranial-caudal CSFP differential increased (mean, 0.39 mm Hg/h), predominantly due to increased cranial pressure. On decompression, cranial CSFP decreased (mean, -1.16 mm Hg) and caudal CSFP increased (mean, 0.65 mm Hg). The CSFP differential did not change significantly after decompression. Cranial CSFPPA was greater than caudal CSFPPA, but this differential did not change during compression. On decompression, the caudal CSFPPA increased in some but not all animals. Although extradural compression exists at the site of injury, lumbar CSFP may not accurately indicate CSFP cranial to the injury. Decompression may provide immediate, though perhaps partial, resolution of the pressure differential. CSFPPA was not a consistent indicator of decompression in this animal model. These findings may have implications for the design of future clinical protocols in which CSFP is monitored after acute SCI.

Non-invasive Estimation of Cerebrospinal Fluid Pressure Waveforms by Means of Retinal Venous Pulsatility and Central Aortic Blood Pressure

Current techniques used for cerebrospinal fluid pressure (CSFp) measurements are invasive. They require a surgical procedure for placement of a pressure catheter in the brain ventricles or in the brain tissue. The human eye provides direct visualisation of its physiological structures and due to its anatomical connection with CSF via the retrolaminar optic nerve it may provide accessible information about CSFp. A total of 25 subjects were included in this study. 15 subjects were used to characterise the relationship between intraocular pressure (IOP), spontaneous retinal venous pulsatility (SRVP), and CSFp. IOP was manipulated and SRVP amplitudes recorded dynamically using the dynamic vessel analyzer (DVA). The relationship between IOP and SRVP amplitude was established to estimate CSFp. Additionally Doppler blood flow velocity of the middle cerebral artery and arterial blood pressure (ABP) were acquired for all subjects. This was to compare and validate our findings with an alternative approach (ICM+) which uses these values to estimate CSFp. A CSFp waveform was extracted from central blood pressure (CBP) waveform by removing its cardiac component frequency. Furthermore to calibrate the CSFp to CBP waveform ratio, invasive CSFp, and ABP was measured from 10 subjects with brain tumours who had a range of normal to elevated CSFp (i.e., 0-30 mmHg). Results show good agreement between the two methods (correlation r (2) = 0.55) Mean estimated CSFp for the two techniques did not show any significant difference (p > 0.05). A significant correlation between CBP pulse (CBPp) and invasive CSFp pulse (CSFpp) was observed (i.e., CSFpp = 0.0654CBBp + 3.91, p < 0.01). Estimated CSFpp was calibrated to CBPp according to this relation. In conclusion, the study demonstrated a good correlation between two different methods of estimating CSFp non-invasively and may provide a novel method to estimate CSF waveforms non-invasively.

The presence of arachnoiditis affects the characteristics of CSF flow in the spinal subarachnoid space: A modelling study

Syringomyelia is a neurological disorder characterised by high pressure fluid-filled cysts within the spinal cord. As syringomyelia is associated with abnormalities of the central nervous system that obstruct cerebrospinal fluid (CSF) flow, it is thought that changes in CSF dynamics play an important role in its pathogenesis. Using three-dimensional computational models of the spinal subarachnoid space (SAS), this study aims to determine SAS obstructions, such as arachnoiditis, change in CSF dynamics in the SAS. The geometry of the SAS was reconstructed from a series of MRI images. CSF is modelled as an incompressible Newtonian fluid with a dynamic viscosity of 1mPas. Three computational models simulated CSF flow in either the unobstructed SAS, or with the SAS obstructed by a porous region simulating dorsal or circumferential arachnoiditis. The permeability of this porous obstruction was varied for the model with dorsal arachnoiditis. The results show that arachnoiditis increases flow resistance in the SAS and this is accompanied by a modest increase in magnitude and/or shift in timing (with respect to the cardiac cycle) of the CSF pressure drop across the region of arachnoiditis. This study suggests that syrinx formation may be related to a change in temporal CSF pulse pressure dynamics.

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

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). 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. 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. Our strategy based on the analysis of CSF pulse pressure parameters seems to have a great accuracy in predicting surgical outcome in clinical practice.

Cerebrospinal fluid pulse pressure amplitude during lumbar infusion in idiopathic normal pressure hydrocephalus can predict response to shunting

BackgroundWe have previously seen that idiopathic normal pressure hydrocephalus (iNPH) patients having elevated intracranial pressure (ICP) pulse amplitude consistently respond to shunt surgery. In this study we explored how the cerebrospinal fluid pressure (CSFP) pulse amplitude determined during lumbar infusion testing, correlates with ICP pulse amplitude determined during over-night ICP monitoring and with response to shunt surgery. Our goal was to establish a more reliable screening procedure for selecting iNPH patients for shunt surgery using lumbar intrathecal infusion.MethodsThe study population consisted of all iNPH patients undergoing both diagnostic lumbar infusion testing and continuous over-night ICP monitoring during the period 2002-2007. The severity of iNPH was assessed using our NPH grading scale before surgery and 12 months after shunting. The CSFP pulse was characterized from the amplitude of single pressure waves.ResultsTotally 62 iNPH patients were included, 45 of them underwent shunt surgery, in whom 78% were shunt responders. Among the 45 shunted patients, resistance to CSF outflow (Rout) was elevated (≥ 12 mmHg/ml/min) in 44. The ICP pulse amplitude recorded over-night was elevated (i.e. mean ICP wave amplitude ≥ 4 mmHg) in 68% of patients; 92% of these were shunt responders. In those with elevated overnight ICP pulse amplitude, we found also elevated CSFP pulse amplitude recorded during lumbar infusion testing, both during the opening phase following lumbar puncture and during a standardized period of lumbar infusion (15 ml Ringer over 10 min). The clinical response to shunting after 1 year strongly associated with the over-night ICP pulse amplitude, and also with the pulsatile CSFP during the period of lumbar infusion. Elevated CSFP pulse amplitude during lumbar infusion thus predicted shunt response with sensitivity of 88 and specificity of 60 (positive and negative predictive values of 89 and 60, respectively).ConclusionsIn iNPH patients, shunt response can be anticipated in 9/10 patients with elevated overnight ICP pulse amplitude, while in only 1/10 with low ICP pulse amplitude. Additionally, the CSFP pulse amplitude during lumbar infusion testing was elevated in patients with elevated over-night ICP pulse amplitude. In particular, measurement of CSFP pulse amplitude during a standardized infusion of 15 ml Ringer over 10 min was useful in predicting response to shunt surgery and can be used as a screening procedure for selection of iNPH patients for shunting.

Progressively worsening paraesthesia of the left leg, gait disturbances and constipation in a 63-year-old man: diagnosis and discussion

Cauda equina syndrome (CES) is a well-known but rare and poorly understood complication of ankylosing spondylitis (AS). CES manifests late in the course of AS, often at a time when the AS is no longer active [1]. MRI characteristically shows an enlarged caudal thecal sac and dorsal arachnoid diverticula that fill the erosions of the bony spinal canal [2, 3]. Our patient had the typical features of CES in AS, i.e. sensory changes in lumbosacral dermatomes, constipation and moderate motor deficits in the left lower limb. However, what made this case unique was the presence of ventral arachnoid diverticula. MRI of the lumbosacral spine demonstrated localised scalloping of the posterior aspect of the L1 and L2 vertebral bodies and ventral arachnoid diverticula without neural tissue herniation. Ventral shift and adhesion of the conus medullaris and the cauda equina were also seen (Figs. 1, 2 in the case presentation). To date, only three cases have been reported regarding ventral dural abnormalities associated with CES in AS (Table 1) [1, 4, 5]. Arachnoid diverticula formation in AS is thought to result from an inflammatory process affecting the vertebral column [6]. In our case, the L1/2 intervertebral disc showed a high signal, similar to that of bone marrow or perivertebral fat on T1and T2-weighted images (Figs. 1, 2 in the case presentation). These findings are thought to be a reflection of normal disc tissue being replaced by fatty bone marrow following an ossification process after severe discitis in the past [7]. This process was accompanied by destruction of cartilaginous endplates and subchondral bone plates, resulting in fusion of the L1 and L2 vertebral bodies. The direction of arachnoid diverticula formation is thought to be dependent on the direction of the force of increased CSF pulse pressure and the “give” of the structures surrounding the spinal canal [1]. If structures posterior to the canal are firm and there is a relatively “soft” spot in the posterior aspect of the vertebral body, erosion could occur anterior to the spinal canal. In our case, we speculate, severe enthesitis of the discovertebral junction at the posterior aspect of the L1/2 vertebral bodies occurred in the past and created a “soft” spot. After the inflammatory process ceased to be active, formation of arachnoid diverticula through a dural defect at this spot occurred over many years. Several possible mechanisms for nerve root damage have been proposed. These include inflammatory injury from arachnoiditis, gravitational traction injury resulting from the presence of arachnoid diverticula, and traumatic damage from excessive CSF pressure fluctuations caused by reduced elasticity and compliance of the caudal sac exposed to inflammatory changes [6, 8, 9]. In our case, we The case presentation can be found at doi:10.1007/s00256-009-0756-0. D. Hayashi (*) : T. Yonenaga :K. Fukuda Department of Radiology, Jikei University School of Medicine, 3-25-8 Nishi-Shimbashi, Minato-Ku, Tokyo 105-8461, Japan e-mail: daichi.hayashi@jikei.ac.jp

Hypothesis for lateral ventricular dilatation in communicating hydrocephalus: New understanding of the Monro-Kellie hypothesis in the aspect of cardiac energy transfer through arterial blood flow

Many theories have been postulated to date regarding mechanisms involved in non-enlargement of the subarachnoid space and enlargement of the ventricles in patients with communicating hydrocephalus, but none have been prove to be definite. Cerebrospinal fluid (CSF) movement is known not to bulk flow but rather pulsatile flow that develops from the energy of the blood flow ejected from the heart, in an isolated system of the intracranial cavity surrounded by a solid skull, as in the Monro-Kellie hypothesis. The authors attempt to explain the mechanisms involved in selective enlargement of the lateral ventricle in patients with communicating hydrocephalus by re-addressing the Monro-Kellie hypothesis with respect to cardiac energy transfer and dissipation by the Windkessel effect. The authors present a concept whereby the large energy of blood flow from the heart that is conveyed to the intracranial artery, arteriole, brain parenchyme, ventricle, and CSF within the confined cranial space as in the Monro-Kellie hypothesis, and which ultimately dissipates to maintain an intracranial energy equilibrium. In the same context, if, for some reason the intracranial equilibrium in the energy transfer and dissipation is changed or disrupted, then structural changes would have to occur to achieve and maintain a new intracranial equilibrium. We postulate that the above described mechanisms are those responsible for the development enlarged of lateral ventricles in patients with communicating hydrocephalus. Structural enlargement of the lateral ventricles in communicating hydrocephalus is a consequence of CSF pathway obstruction and resultantly increased CSF absorption function in the lateral ventricle which markedly increases the pulsatile CSF energy flow returning to the lateral ventricles, thus causing collision of pulsatile CSF flow with the brain parenchyme at the ventricular wall, which subsequently leads to structural enlargement of the lateral ventricles. Also, the collision between the CSF pulsation and brain parenchyme pulsation reduces the Windkessel effect of the brain parenchyme which increases the intracranial artery pulse pressure, which in turn is transmitted to the CSF and increases CSF pulse pressure. This vicious circle results in the high pulse pressure within the lateral ventricle structurally dilating the lateral ventricle. Our theory also explains the relationship between ventricle dilatation and idiopathic intracranial hypertension, venous sinus thrombosis, achondroplasia.

O.031 Morphological correlation between CBF velocity and CSF pulse pressure waveforms in NPH patients

Evaluar la utilidad del análisis del registro de la presión intracraneal (PIC) en el manejo de pacientes con marcada ventriculomegalia de larga evolución.Veintidós pacientes con ventriculomegalia radiológica y clínica neurológica. Se recogen los datos demográficos, clínicos y radiológicos, así como los datos de monitorización de PIC y las complicaciones relacionadas con el procedimiento. Se evalúan resultados clínicos a los 6 meses de la intervención.Las edades oscilaron entre los 20 y los 70 años, con una media de 44 años. El síntoma de consulta más frecuente fue la cefalea. Los índices de Evans oscilaron entre 0,35 y 0,66, con una media de 0,47. El 55% asociaban estenosis de acueducto de Silvio. La PIC media fue superior a 12 mmHg en solo el 9% de los pacientes, en tanto que el análisis morfológico de los trazados catalogó al 64% de los mismos como patológicos. El análisis morfológico del trazado evidencia ondas A premeseta en 7 pacientes y ondas B en 20 pacientes (14 de ellos con ondas B de alta amplitud). Se consideraron patológicos y por tanto candidatos a cirugía a 14 pacientes, de los que 12 aceptaron la intervención (derivación de líquido cefalorraquídeo o ventriculostomía). El 70% de ellos habían experimentado mejoría a los 6 meses. No hubo complicaciones relacionadas con la monitorización.La monitorización de la PIC es un método seguro y fiable, útil en el manejo de esta entidad, que permite seleccionar los pacientes candidatos a cirugía. Es imprescindible un análisis morfológico del trazado, ya que la PIC media es un dato de escasa utilidad, en tanto que la presencia de ondas A y B de alta amplitud se relaciona con una buena respuesta al shunt.To analyze the usefulness of intracranial pressure (ICP) monitoring in overt long-standing ventriculomegaly patients.There were 22 patients with ventriculomegaly and neurological symptoms. Demographic, clinical and radiological data were collected, as well as ICP monitoring data and complications related to the procedure. Results were evaluated 6 months after surgery.Mean age was 44 years (22-70). Mean Evans index was 0.47 (0.35-0.66). Aqueductal stenosis was present in more than half of the patients (55%). Mean ICP was higher than 12 mmHg in only 9% of patients. Morphological analysis of ICP recordings was abnormal in 64% of patients. “Pre-plateau” A waves were seen in 7 patients, with B waves seen in 20 patients (high amplitude B waves in 14). Twelve patients were operated on the basis of ICP recordings (CSF shunt or ventriculostomy). Seventy per cent of treated patients had improved at 6 months. There were no complications related to the monitoring technique.ICP monitoring is a valuable, safe tool, very useful in these cases. Selection of surgical candidates on the basis of ICP monitoring seems to be advisable. Mean ICP may be normal even with pathological recordings. Morphological analysis is essential to establish a correct diagnosis. The presence of A and B waves in the recording is highly related to good shunt response.

Unraveling the riddle of syringomyelia

The pathophysiology of syringomyelia development is not fully understood. Current prevailing theories suggest that increased pulse pressure in the subarachnoid space forces cerebrospinal fluid (CSF) through the spinal cord into the syrinx. It is generally accepted that the syrinx consists of CSF. The here-proposed intramedullary pulse pressure theory instead suggests that syringomyelia is caused by increased pulse pressure in the spinal cord and that the syrinx consists of extracellular fluid. A new principle is introduced implying that the distending force in the production of syringomyelia is a relative increase in pulse pressure in the spinal cord compared to that in the nearby subarachnoid space. The formation of a syrinx then occurs by the accumulation of extracellular fluid in the distended cord. A previously unrecognized mechanism for syrinx formation, the Bernoulli theorem, is also described. The Bernoulli theorem or the Venturi effect states that the regional increase in fluid velocity in a narrowed flow channel decreases fluid pressure. In Chiari I malformations, the systolic CSF pulse pressure and downward motion of the cerebellar tonsils are significantly increased. This leads to increased spinal CSF velocities and, as a consequence of the Bernoulli theorem, decreased fluid pressure in narrow regions of the spinal CSF pathways. The resulting relatively low CSF pressure in the narrowed CSF pathway causes a suction effect on the spinal cord that distends the cord during each systole. Syringomyelia develops by the accumulation of extracellular fluid in the distended cord. In posttraumatic syringomyelia, the downwards directed systolic CSF pulse pressure is transmitted and reflected into the spinal cord below and above the traumatic subarachnoid blockage, respectively. The ensuing increase in intramedullary pulse pressure distends the spinal cord and causes syringomyelia on both sides of the blockage. The here-proposed concept has the potential to unravel the riddle of syringomyelia and affords explanations to previously unanswered clinical and theoretical problems with syringomyelia. It also explains why syringomyelia associated with Chiari I malformations may develop in any part of the spinal cord including the medullary conus. Syringomyelia thus preferentially develops where the systolic CSF flow causes a suction effect on the spinal cord, i.e., at or immediately caudal to physiological or pathological encroachments of the spinal subarachnoid space.

Shunt-related craniocerebral disproportion: treatment with cranial vault expanding procedures

Two patients with intracranial arachnoid cysts, one with myelomeningocele-hydrocephalus and the other with a subdural fluid collection, were given a cerebrospinal (CSF) extracranial shunt. All four patients developed features of CSF overdrainage following shunting and were treated by cranial vault expanding procedures. Before undergoing decompressive craniotomy, the patients were treated by a variety of procedures, including changing of obstructed ventricular catheters (n=4), insertion or upgrading of programmable valves (n=3), and foramen magnum decompression (n=1). Clinical manifestations of these four patients were attributed to craniocerebral disproportion caused by chronic and progressive skull changes due to dampening of the CSF pulse pressure, which is necessary for maintaining normal cranial growth. On the basis of our previous experience with expanding craniotomies in cases of minimal forms of craniosynostosis, we treated these patients with bilateral parietal craniotomies, with satisfactory results. In conclusion, biparietal decompressive craniotomy constitutes a useful and safe procedure for relieving the clinical manifestations of some CSF overdrainage syndromes, especially in cases with slit-ventricle syndrome and craniocerebral disproportion that prove to be refractory to simpler management procedures.

Lumbar cerebrospinal fluid pressure waves versus intracranial pressure waves in idiopathic normal pressure hydrocephalus

The aim of this study was to explore how the lumbar cerebrospinal fluid pressure (CSFP) waves recorded during lumbar infusion compared with the intracranial pressure (ICP) waves recorded, either during lumbar infusion or during long-term, overnight monitoring. For this purpose, we assessed 27 simultaneous lumbar CSFP/ICP recordings made during lumbar infusion and 27 long-term, overnight ICP recordings in 27 consecutive idiopathic normal pressure hydrocephalus (iNPH) patients. Pressure waves during lumbar infusion were explored by computing pulse pressure amplitude and mean single wave pressure of every corresponding CSFP/ICP wave pair; among our 27 lumbar CSFP/ICP recordings a total of 35,532 CSFP/ICP wave pairs were available for analysis. We as well computed mean values of pulse pressure amplitude (i.e. mean CSFP wave amplitude or mean ICP wave amplitude) and mean values of mean single wave pressure (i.e. mean CSFP or mean ICP) during consecutive 6-s time windows, as well as average values for the individual recordings. During lumbar infusion, the cerebrospinal fluid pulse pressure amplitudes were about 2 mmHg smaller than the corresponding intracranial pulse pressure amplitudes. The mean CSFP wave amplitudes recorded during lumbar infusion correlated significantly with the mean ICP wave amplitudes recorded either during lumbar infusion or during long-term, overnight ICP monitoring. In 21 of 27 lumbar infusion tests (78%), the presence of elevated lumbar mean CSFP waves was related to presence of elevated mean ICP wave amplitudes during long-term, overnight ICP monitoring. Hence, the lumbar cerebrospinal fluid pulse pressure amplitudes recorded during lumbar infusion could be used to predict the intracranial pulse pressure amplitudes recorded during long-term, overnight ICP monitoring.