Influence of shunt type on ventricular volume changes in children with hydrocephalus

2003 ◽  
Vol 98 (2) ◽  
pp. 277-283 ◽  
Author(s):  
Chris Xenos ◽  
Spiros Sgouros ◽  
Kalyan Natarajan ◽  
A. Richard Walsh ◽  
Anthony Hockley
Keyword(s):  
Statistical Significance ◽  
Ventricular Volume ◽  
Magnetic Resonance Images ◽  
Healthy Children ◽  
Content Type ◽  
Shunt Placement ◽  
Age Related ◽  
The Mean ◽  
The Difference ◽  
Fine Print

Object. The goal of this study was twofold: to investigate the change in ventricular volume in children with hydrocephalus in response to shunt placement and to assess the effects of two different valve types (Medium Pressure [MP] cylindrical valve and Delta [model 1.5] valve). Methods. Ventricular volume was measured using segmentation techniques on computerized tomography scans and magnetic resonance images obtained in 40 children with hydrocephalus who ranged in age from 4 days to 16 years. Imaging was performed preoperatively and at 5 days and 3, 6, and 12 months postoperatively. The results were compared with measurements obtained in 71 healthy children ranging in age from 1 month to 15 years. Each ventricular volume that was measured was divided by the corresponding sex and age—related mean normal volume to calculate the “× normal” ventricular volume, indicating how many times larger than normal the ventricle was. The mean preoperative ventricular volume was 232 cm3 (range 50–992 cm3). The mean postoperative volumes were 147, 102, 68, and 61 cm3 at 5 days and at 3, 6, and 12 months posttreatment, respectively. The mean preoperative × normal ventricular volume was 14.5 (range 2.2–141.7), and the mean postoperative × normal volumes were 7.9, 5.6, 3.5, and 2.9 at 5 days and 3, 6, and 12 months postimplantation, respectively. The rate of volume reduction was consistently higher in patients who received the MP valve in comparison with those who received the Delta valve, both for new shunt insertions and for shunt revisions. The difference between the two valve groups did not reach statistical significance. Two patients in whom ventricular volumes increased during the study period experienced shunt obstruction at a later time. Conclusions. Preoperative ventricular volume in children with hydrocephalus can be up to 14 times greater than normal. In response to shunt placement, the ventricular volume continues to fall during the first 6 months after operation. The effect is more profound in children who receive the MP valve than in those who receive the Delta valve, although in this study the authors did not demonstrate statistical significance in the difference between the two valves. Nevertheless, this may indicate that the MP valve produces overdrainage in comparison with the Delta valve, even within the first few months after insertion. There is some indication that sequential ventricular volume measurement may be used to identify impending shunt failure.

Normal changes in orbital volume during childhood

2002 ◽  
Vol 96 (4) ◽  
pp. 742-746 ◽  
Author(s):  
Robert P. Bentley ◽  
Spyros Sgouros ◽  
Kalyan Natarajan ◽  
M. Stephen Dover ◽  
Anthony D. Hockley
Keyword(s):  
Statistical Significance ◽  
Significant Proportion ◽  
Magnetic Resonance Images ◽  
Healthy Children ◽  
Content Type ◽  
Linear Pattern ◽  
Orbital Volume ◽  
Disease States ◽  
The Difference ◽  
Fine Print

Object. The aim of this study was to construct a model of changes in orbital volume that occur throughout childhood from the age of 1 month to 15 years, which could be used for comparative studies of disease states affecting orbital growth. Methods. Using the procedure of segmentation on magnetic resonance images obtained in 67 healthy children, orbital volume was measured and plotted against age. During the first few months of life left orbital volume is on average 15 cm3 in male and 13 cm3 in female infants; these volumes increase to 26 cm3 and 24 cm3, respectively, by the time the child reaches 15 years of age. During the first few months of life right orbital volume is on average 16 cm3 in male and 13 cm3 in female infants; these volumes increase to 27 cm3 and 25 cm3, respectively, by the time the child is 15 years old. This represents an overall increase in orbital volume by a factor of 1.7 in boys and 1.8 in girls. By the time the child has reached 5 years of age, the orbital volume for both right and left sides has reached on average 77% of the volume seen at 15 years in both sexes. The differences between the two sides are not statistically significant for either sex. The change in orbital volume that is associated with age in general displays a linear pattern. Throughout childhood, orbital volumes are larger in boys than in girls, but share a similar growth pattern. The difference between the two sexes tends toward statistical significance during the first 5 years of life (left orbit p = 0.1, right orbit p = 0.04). Conclusions. During early childhood, orbital volume increases in a linear fashion, achieving a significant proportion of its final growth by the time the child is 5 years old.

Biomechanical and hydrodynamic characterization of the hydrocephalic infant

1985 ◽  
Vol 63 (1) ◽  
pp. 69-75 ◽  
Author(s):  
Kenneth Shapiro ◽  
Arno Fried ◽  
Anthony Marmarou
Keyword(s):  
Steady State ◽  
Ventricular Volume ◽  
Volume Index ◽  
Injection Technique ◽  
Infantile Hydrocephalus ◽  
Content Type ◽  
Two Factors ◽  
The Mean ◽  
Fine Print

✓ The pressure-volume index (PVI) technique of bolus manipulation of cerebrospinal fluid (CSF) was used to measure neural axis volume-buffering capacity and resistance to the absorption of CSF in 16 hydrocephalic infants prior to shunting. The mean steady-state intracranial pressure (ICP) was 11.7 ± 5.7 mm Hg (± standard deviation (SD)), representing a modest elevation of ICP in infants. The mean measured PVI was 28.1 ± 1.5 ml (± standard error of the mean (SEM)) compared to the predicted normal level for these infants of 12.1 ± 2.7 ml (± SD) (p < 0.001). This resulted from an enhanced volume storage capacity in the hydrocephalic infants. The PVI was not related to ventricular size in these hydrocephalic infants. Although absorption of the additional bolus of fluid did not occur at steady-state ICP, it was readily absorbed once ICP was raised above a mean threshold pressure of 16.0 ± 5.0 mm Hg (± SD) in 13 of the 16 infants. Above this pressure, the mean CSF absorption resistance was 7.2 ± 1.3 mm Hg/ml/min (± SEM) which is twice the normal values as measured by the bolus injection technique. The biomechanical profile of infantile hydrocephalus described in this study indicates that two factors are required for progression of ventricular volume. While an absorptive defect may initiate the hydrocephalic process, progressive volume storage requires an alteration in the mechanical properties of the intracranial compartment.

Ventricular volume change in childhood

2002 ◽  
Vol 97 (3) ◽  
pp. 584-590 ◽  
Author(s):  
Chris Xenos ◽  
Spyros Sgouros ◽  
Kalyan Natarajan
Keyword(s):  
Statistical Difference ◽  
Linear Regression Analysis ◽  
Ventricular Volume ◽  
Intracranial Volume ◽  
Normal Children ◽  
Content Type ◽  
Ventricular Volumes ◽  
Significant Difference ◽  
The Mean ◽  
Fine Print

Object. The aim of this study was to construct a model of age-related changes in ventricular volume in a group of normal children ages 1 month to 15 years, which could be used for comparative studies of cerebrospinal fluid circulation disorders and cerebral atrophy developmental syndromes. Methods. A magnetic resonance imaging—based segmentation technique was used to measure ventricular volumes in normal children; each volume was then plotted against the child's age. In addition, intracranial volumes were measured and the ratio of ventricular to intracranial volume was calculated and plotted against age. The study group included 71 normal children, 39 boys and 32 girls, whose ages ranged from 1 month to 15.3 years (mean 84.9 months, median 79 months). The mean ventricular volume was 21.3 cm3 for the whole group, 22.7 cm3 in boys and 19.6 cm3 in girls (p = 0.062, according to t-tests). The mean ventricular volume at 12 months for the whole group was 17 cm3 (20 cm3 in boys and 15 cm3 in girls), representing 65% of the volume achieved by 15 years of age (87% in boys and 53% in girls). The volume increased by a factor of 1.53, to 26 cm3 (23 cm3 in males and 28 cm3 in females, increase factors of 1.15 and 1.86, respectively) at 15 years of age. The change in ventricular volume with age is not linear, but follows a segmental pattern. These age periods were defined as: 0 to 3, 4 to 6, 7 to 10, and 11 to 16 years. A statistical difference based on sex was only demonstrated in the first 6 years of life. The mean ventricular volume for the first 6-year period was 22.4 cm3 in boys and 15.7 cm3 in girls, and the difference was significant for the two sexes (linear regression analysis for age and sex, significant according to analysis of variance regression at 0.007, p = 0.108 for age, p = 0.012 for sex). Thereafter, there was no significant difference in ventricular volume between boys and girls with further growth. The ratio of ventricular volume to intracranial volume was 0.0175 for the whole group, 0.017 in boys and 0.018 in girls (p = 0.272, according to t-tests). At 12 months of age the ratio was 0.019; it stabilized to 0.015 at 8 years of age, and increased to 0.018 at 15 years of age. No statistical difference based on sex was demonstrated with growth. Conclusions. The ventricular volume in normal children increases with age by a factor of 1.5; the increase is in a nonlinear segmental pattern. Boys have significantly higher ventricular volumes only in the first 6 years of life. The ventricular/intracranial volume ratio remains stable throughout childhood.

Age-related changes in intracranial compartment volumes in normal adults assessed by magnetic resonance imaging

1996 ◽  
Vol 84 (6) ◽  
pp. 982-991 ◽  
Author(s):  
Mitsunori Matsumae ◽  
Ron Kikinis ◽  
István A. Mórocz ◽  
Antonio V. Lorenzo ◽  
Tamás Sándor ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Brain Volume ◽  
Intracranial Volume ◽  
Mr Image ◽  
Content Type ◽  
Age Related ◽  
The Difference ◽  
Normal Adults ◽  
Fine Print ◽  
Age Related Changes

✓ Magnetic resonance (MR) image—based computerized segmentation was used to measure various intracranial compartments in 49 normal volunteers ranging in age from 24 to 80 years to determine age-related changes in brain, ventricular, and extraventricular cerebrospinal fluid (CSF) volumes. The total intracranial volume (sum of brain, ventricular, and extraventricular CSF) averaged 1469 ± 102 cm3 in men and 1289 ± 111 cm3 in women. The difference was attributable primarily to brain volume, which accounted for 88.6% of the respective intracranial volumes in both sexes, but was significantly larger in men (1302 ± 112 cm3) than in women (1143 ± 105 cm3). In both, the cranial CSF volume averaged 11.4%. Total intracranial volume did not change with age, although the normalized brain volume of both men and women began to decrease after the age of 40 years. This decrease was best reflected by expansion of the extraventricular CSF volume which, after the age of 50 years, was more marked in men than in women. The volume of the cranial CSF, as determined by MR image-based computerized segmentation, is considerably larger than traditionally accepted and resides mostly extraventricularly. Expansion of CSF volume with age provides a good index of brain shrinkage although evolving changes and growth of the head with age tend to confound the results.

Height of cervical foramina after anterior discectomy and implantation of a carbon fiber cage

2001 ◽  
Vol 95 (1) ◽  
pp. 40-42 ◽  
Author(s):  
Ronald H. M. A. Bartels ◽  
Roland Donk ◽  
Roel van Dijk Azn
Keyword(s):  
Carbon Fiber ◽  
Statistical Significance ◽  
Mean Value ◽  
Disc Space ◽  
Content Type ◽  
Wedge Shape ◽  
The Mean ◽  
Foraminal Height ◽  
Tomography Scanning ◽  
Fine Print

Object. The authors evaluate the effects of implantation of a carbon fiber cage after anterior cervical discectomy (ACD) on the height of the foramen and the angulation between endplates of the disc space. Methods. Thirteen consecutive patients who were scheduled for standard microscopic ACD and interbody fusion underwent thin-slice (1.5 mm) spiral computerized tomography scanning 1 day preoperatively, 1 day postoperatively, and 1 year postoperatively. Oblique sagittal reconstructions were made through both foramina; the height of each foramen and the angle between the endplates were measured. Because 16 cages were implanted, 32 foramina were investigated. Preoperatively, the mean height of the foramina (± standard deviation) was 8.1 ± 1.5 mm (range 5.7–12 mm), and at 1 day postoperatively it was 9.7 ± 1.4 mm (range 7.5–12.8 mm). This difference reached statistical significance (p < 0.0005). The mean foraminal height after 1 year was 9.4 ± 1.4 mm (range 6.9–12.7 mm). In terms of the preoperative value, the 1-year measurement still reached statistical difference (p < 0.005) but not with the direct postoperative mean foraminal height. Preoperatively the mean value of the angle between the two adjacent endplates was 1.3 ± 2.4° (range 0–8°), and postoperatively it was 7.8 ± 2.9° (range 2–12°), which was statistically significant (p < 0.0005). Conclusions. The cervical carbon fiber cage effectively increased the height of the foramen even after 1 year, which contributed to decompression of the nerve root. The wedge shape of the device may contribute to restoration of lordosis.

Preservation of hearing in patients undergoing microsurgery for vestibular schwannoma: degree of meatal filling

2005 ◽  
Vol 102 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Gérard Mohr ◽  
Burak Sade ◽  
Jean-Jacques Dufour ◽  
Jamie M. Rappaport
Keyword(s):  
Vestibular Schwannoma ◽  
Tumor Size ◽  
Intraoperative Monitoring ◽  
Statistical Significance ◽  
Multivariable Analysis ◽  
Internal Auditory Canal ◽  
Magnetic Resonance Images ◽  
Content Type ◽  
Incomplete Filling ◽  
Fine Print

Object. Preservation of hearing has become a standard goal in selected patients undergoing surgery for a vestibular schwannoma (VS). This study was aimed at analyzing the role played by filling of the internal auditory canal (IAC) as well as those played by preoperative hearing quality, and tumor size in the postoperative preservation of serviceable hearing (SH). Methods. Three hundred eighty-six patients with VS were treated. Hearing preservation was attempted in 128 cases (33.2%) by using intraoperative monitoring and following a retrosigmoid approach. The maximal extrameatal size of the tumor, its extension within the IAC, and pre- and postoperative hearing quality, according to the Gardner—Robertson classification, were evaluated. Preservation of SH was achieved in 24.2% of the 128 patients. With respect to tumor size, SH was preserved in 39% of 77 patients harboring a tumor 15 mm wide or smaller and in 2% of 51 patients with lesions 16 mm wide or larger (p < 0.001). With regard to filling of the IAC, among 63 patients harboring a tumor 15 mm or smaller, in whom magnetic resonance images were available, SH was preserved in 52.8% of 36 patients with partial filling and in 25.9% of 27 patients with complete filling (p = 0.032). Concerning preoperative hearing quality, in the patients with tumors 15 mm or smaller, SH was preserved in 46.5% of 43 patients with Gardner—Robertson Class I hearing and 29.4% of 34 patients with Class II hearing (p = 0.126). Both tumor size and the extent of IAC filling proved statistically significant in a multivariable analysis (p < 0.001 and p = 0.026, respectively). Conclusions. Incomplete filling of the IAC and a tumor size of 15 mm or smaller are independent favorable factors in SH preservation. Excellent preoperative hearing appears to have a positive impact but does not have statistical significance. Intraoperative monitoring is useful in guiding the dissection; however, the surgeon's knowledge of topographical landmarks and meticulous surgical technique remain the essential factors of success.

Correlation between decreased ventricular size and positive clinical outcome following shunt placement in patients with normal-pressure hydrocephalus

2004 ◽  
Vol 100 (6) ◽  
pp. 1036-1040 ◽  
Author(s):  
Ullrich Meier ◽  
Sven Mutze
Keyword(s):  
Clinical Outcome ◽  
Normal Pressure Hydrocephalus ◽  
Normal Pressure ◽  
Ventricular Volume ◽  
Communicating Hydrocephalus ◽  
Ventricular Size ◽  
Content Type ◽  
Shunt Placement ◽  
Postoperative Change ◽  
Fine Print

Object. It is well known that in patients with communicating hydrocephalus or normal-pressure hydrocephalus (NPH), ventricular size decreases following implantation of shunts with differential pressure valves. The aim of this study was to determine whether ventricular size correlates with a positive clinical outcome following shunt placement. Methods. Hydrostatic valves (dual-switch valves) were implanted in 80 patients with NPH at Unfallkrankenhaus, Berlin, between September 1997 and January 2002. One year postoperatively, these patients underwent computerized tomography scanning, and their ventricular size was ascertained using the Evans Index. Among 80% of the patients who showed no postoperative change in ventricular volume, 59% nonetheless had good to excellent clinical improvements, 17% satisfactory improvement, and 24% no improvement. Furthermore, a moderate reduction in ventricular size was observed in 14% of patients in this cohort. Among these, 36% experienced good to excellent clinical improvements, 28% satisfactory improvement, and 36% unsatisfactory improvement. A marked reduction in ventricular size was observed in 6% of the patients. Of this latter group, 60% demonstrated good to excellent outcomes, whereas 40% had unsatisfactory outcomes. Conclusions. Favorable outcomes following the implantation of a hydrostatic shunt in patients with NPH did not correlate with decreased ventricular volume 1 year after surgery. In fact, better clinical outcomes were observed in patients with little or no alteration in ventricular size, compared with those in patients with a marked decrease in ventricular size. A postoperative change in ventricular volume should be assessed differently in patients with NPH compared with those suffering from hypertensive hydrocephalus.

Volumetric measurements in the detection of reduced ventricular volume in patients with normal-pressure hydrocephalus whose clinical condition improved after ventriculoperitoneal shunt placement

2002 ◽  
Vol 97 (1) ◽  
pp. 73-79 ◽  
Author(s):  
Richard C. Anderson ◽  
Jessica J. Grant ◽  
Robert de la Paz ◽  
Steven Frucht ◽  
Robert R. Goodman
Keyword(s):  
Clinical Improvement ◽  
Normal Pressure Hydrocephalus ◽  
Normal Pressure ◽  
Ventricular Volume ◽  
Ventricular Size ◽  
Content Type ◽  
Shunt Placement ◽  
Lateral Ventricles ◽  
Fine Print ◽  
Volumetric Measurements

Object. The syndrome of normal-pressure hydrocephalus (NPH) refers to the clinical triad of gait disturbance, dementia, and urinary incontinence in association with idiopathic ventriculomegaly and normal intracranial pressure. Ventriculoperitoneal (VP) shunt placement often yields significant clinical improvements, sometimes without apparent reduction of ventricular size. The authors hypothesized that careful volumetric measurements would show a decrease in ventricular volume in these patients. Methods. Twenty consecutive patients with NPH underwent placement of VP shunts equipped with programmable valves. In 11 patients pre- and postoperative neuroimaging was performed, which allowed volumetric analysis. Volumetric measurements of the lateral ventricles were calculated in triplicate by National Institutes of Health image-processing software to assess standard computerized tomography (CT) scans (eight patients) or magnetic resonance (MR) images (three patients) obtained before and after shunt placement. Ventricular volumes were also assessed by an independent neuroradiologist. Postoperative studies were performed at a time of clinical improvement, between 1 and 9 months postsurgery (mean 5 months). Preoperative and postoperative Unified Parkinson's Disease Rating Scale evaluations were performed in four patients. Significant clinical improvement occurred in all patients after shunt placement (mean follow-up period 17.5 months). Although 10 (91%) of 11 patients demonstrated a calculable decrease in volume in the lateral ventricles (mean decrease 39%), formal interpretation of neuroimages indicated a definite decrease in lateral ventricular volume in only three (27%) of 11 patients. Conclusions. Volumetric measurements obtained to compare preoperative and postoperative CT or MR studies obtained in patients with NPH in whom clinical improvement was seen after shunt placement surgery show a demonstrable decrease in ventricular size. Volumetric measurements may be helpful in clinical assessment postoperatively and in guiding programmable valve pressure settings.

Intracranial volume change in craniosynostosis

1999 ◽  
Vol 91 (4) ◽  
pp. 617-625 ◽  
Author(s):  
Spiros Sgouros ◽  
Anthony D. Hockley ◽  
J. Henry Goldin ◽  
Michael J. C. Wake ◽  
Kalyan Natarajan
Keyword(s):  
Volume Growth ◽  
Underlying Mechanism ◽  
Intracranial Volume ◽  
Healthy Children ◽  
Optimum Time ◽  
Content Type ◽  
Head Growth ◽  
The Difference ◽  
Cranial Expansion ◽  
Fine Print

Object. There is still controversy regarding the optimum time to perform surgery for craniosynostosis. Some recommend surgery soon after birth and others delay until the age of 12 months. Intracranial pressure has been measured in an attempt to provide a scientific rationale, but many questions remain unanswered. To date, little attention has been given to intracranial volume and its changes during the first few years of life in children with craniosynostosis. The authors' goal was to focus on intracranial volume during this period and to compare measurements obtained in patients with craniosynostosis with measurements obtained in healthy individuals.Methods. Using the technique of segmentation, the intracranial volume of 84 children with various forms of craniosynostosis was measured on preoperative computerized tomography scans. The change in average volume that occurs with increasing age was calculated and compared with a model of normal intracranial volume growth. The age at presentation for children with craniosynostosis was 1 to 39 months; 76% of the patients were younger than 12 months. In eight patients in whom only one cranial expansion procedure was performed, postoperative intracranial volumes were measured as well. Several interesting observations emerged. 1) There was little difference in head growth between boys and girls with craniosynostosis during the first few months of life. After the age of 12 months, however, the difference in intracranial volume normally seen between the two genders was observed in the craniosynostosis group as well. 2) Excluding children with complex pansynostosis, who have smaller heads, children with all other types of craniosynostosis have similar head growth after the 1st year of life, with no difference between the number of and type of suture affected. Children with Apert's syndrome develop greater than normal intracranial volumes after the 1st year of life. 3) Although children with craniosynostosis are born with a smaller intracranial volume, by the age of 6 months volume has reached normal levels, and from that point on volume follows the pattern of normal head growth. 4) Children who presented after the age of 6 months and later developed recurrent craniosynostosis after initial successful treatment had a small intracranial volume at their initial presentation. 5) Of the patients whose postoperative intracranial volumes were measured, all but one had preoperative volumes at or above normal values, and their postoperative volumes were considerably higher than normal for their age. These children all followed a growth curve parallel to that of healthy children but at higher volume value. One patient with a smaller-than-normal initial intracranial volume was surgically treated at a very young age and, despite cranial expansion surgery, postoperative volume did not reach normal levels. It is postulated that this was due to the fact that the operation was performed at a time when craniosynostosis was still active.Conclusions. The results of this study indicate that the underlying mechanism leading to craniosynostosis and constriction of head volume “exhausts” its effect during the first few months of life. Measurement of intracranial volume in clinical practice could be used to “fine tune” the optimum time for surgery. In late-presenting children, this may be useful in predicting possible recurrence.

A laboratory model of shunt-dependent hydrocephalus

1987 ◽  
Vol 66 (5) ◽  
pp. 734-740 ◽  
Author(s):  
Arno Fried ◽  
Kenneth Shapiro ◽  
Futoshi Takei ◽  
Ira Kohn
Keyword(s):  
Volume Index ◽  
Laboratory Model ◽  
Content Type ◽  
Shunt Placement ◽  
Shunt Occlusion ◽  
Shunt Dependency ◽  
Biomechanical Changes ◽  
The Mean ◽  
Fine Print

✓ This study was designed to determine whether implanting shunts in hydrocephalic cats produced the same biomechanical changes as have previously been found in children with shunts. Neuraxis volume-buffering capacity (pressure-volume index: PVI) and the resistance to the absorption of cerebrospinal fluid (CSF) were determined before and 3 weeks after placing shunts in 16 hydrocephalic cats. Intracranial pressure (ICP) was monitored for at least 6 hours after the shunts were occluded. The brains were perfused in vivo and removed to assess the size of the ventricles. The mean PVI of the hydrocephalic cats was 3.6 ± 0.2 ml (± standard error of the mean) before the shunts were placed. Three weeks after adequate shunt function was first established, the mean PVI decreased to 1.1 ± 0.1 ml and was similar to values determined in control animals. Prior to shunt placement, the resistance to the absorption of CSF was 28.4 ± 4.5 mm Hg/ml/min and did not vary with ICP. This parameter changed after shunting and increased as a function of ICP (r = 0.87, p < 0.001). At ICP's below 20 mm Hg, the resistance to the absorption of CSF was 65.0 ± 18.0 mm Hg/ml/min but increased to 220.0 ± 40.5 mm Hg/ml/min when determined at ICP's above 20 mm Hg. Corroborating evidence for this linkage of resistance to the absorption of CSF to ICP was found in the inexorable rise of ICP during the 6 hours of monitoring after the shunts were occluded. After shunt placement, the ventricles were normal in size in 12 cats and slightly enlarged in four. The biomechanical profile and pressure response to shunt occlusion in this laboratory model resembles that previously described in shunt-dependent children. As in humans, shunt placement in hydrocephalic cats results in normalization of the PVI and a linkage of the resistance to the absorption of CSF to ICP. The significance of these changes as they relate to shunt dependency is discussed.

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