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.

Subtle deterioration in shunted childhood hydrocephalus

1986 ◽  
Vol 65 (2) ◽  
pp. 211-216 ◽  
Author(s):  
Arno Fried ◽  
Kenneth Shapiro
Keyword(s):  
Buffering Capacity ◽  
Volume Index ◽  
Shunt Revision ◽  
Pressure Waves ◽  
Ventricular Size ◽  
Csf Shunts ◽  
Content Type ◽  
The Mean ◽  
Childhood Hydrocephalus ◽  
Fine Print

✓ Eighteen hydrocephalic children who presented with subtle deterioration when their shunts malfunctioned were studied during shunt revision by means of the pressure-volume index (PVI) technique. Bolus manipulation of cerebrospinal fluid (CSF) was used to determine the PVI and the resistance to the absorption of CSF (Ro). Ventricular size was moderately to severely enlarged in all the children. Steady-state intracranial pressure (ICP) at the time of shunt revision was 17.5 ± 7.3 mm Hg (range 8 to 35 mm Hg). Pressure waves could not be induced by bolus injections in the 8- to 35-mm Hg range of ICP tested. The mean ± standard deviation (SD) of the predicted normal PVI for this group was 18.5 ± 2.7 ml. The mean ± standard error of the mean of the measured PVI was 35.5 ± 2.1 ml, which represented a 187% ± 33% (± SD) increase in volume-buffering capacity (p < 0.001). The ICP did not fall after bolus injections in three children, so that the Ro could not be measured. In the remaining 15 patients, Ro increased linearly as a function of ICP (r = 0.74, p < 0.001). At ICP's below 20 mm Hg, Ro ranged from 2.0 to 5.0 mm Hg/ml/min, but increased to as high as 21 mm Hg/ml/min when ICP was above 20 mm Hg. This study documents that subtle deterioration in shunted hydrocephalic children is accompanied by abnormally compliant pressure-volume curves. These children develop ventricular enlargement and neurological deterioration without acute episodic pressure waves. The biomechanical profile of this group differs from other children with CSF shunts.

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.

In vivo assessment of the window of barrier opening after osmotic blood—brain barrier disruption in humans

2000 ◽  
Vol 92 (4) ◽  
pp. 599-605 ◽  
Author(s):  
Tali Siegal ◽  
Rina Rubinstein ◽  
Felix Bokstein ◽  
Allan Schwartz ◽  
Alexander Lossos ◽  
...  
Keyword(s):  
Blood Brain Barrier ◽  
Time Course ◽  
Photon Emission ◽  
Brain Barrier ◽  
Therapeutic Window ◽  
Content Type ◽  
Blood Brain ◽  
The Mean ◽  
Fine Print

Object. Osmotic blood—brain barrier (BBB) disruption induced by intraarterial infusion of mannitol is used in conjunction with chemotherapy to treat human brain tumors. The time course to barrier closure, or the so-called therapeutic window, has been examined in animals but little information is available in humans. The authors, therefore assessed the time course to barrier closure after osmotic BBB disruption in humans.Methods. Disruption of the BBB was demonstrated using 99mTc-glucoheptonate (TcGH) single-photon emission computerized tomography (SPECT) scanning in 12 patients who were treated monthly with combination chemotherapy in conjunction with BBB disruption. The primary diagnosis was primary central nervous system lymphoma in seven patients and primitive neuroectodermal tumors in five. The TcGH (20 mCi) was injected at 1- to 480-minute intervals after osmotic BBB disruption, and patients underwent SPECT scanning after 4 hours. A total of 38 studies was performed. Good-to-excellent BBB disruption was obtained in 29 procedures and poor-to-moderate disruption was seen in the other nine studies.The TcGH indices correlated with the degree of BBB disruption as measured postprocedure on contrast-enhanced CT scans (r = 0.852). Mean baseline TcGH indices were 1.02 ± 0.07. For the group of patients with good-to-excellent disruptions the mean indices at 1 minute postdisruption measured 2.19 ± 0.18. After 40 minutes no significant change was noted (mean index 2.13 ± 0.2). Then the indices declined more steeply and at 120 minutes after the disruption the index was 1.36 ± 0.02. A very slow decline was noted between 120 and 240 minutes after mannitol infusion. At 240 minutes the barrier was still open for all good-to-excellent disruptions (index 1.33 ± 0.08) but at 480 minutes the mean indices had returned to the baseline level.Conclusions. Results of these in vivo human studies indicate that the time course to closure of the disrupted BBB for low-molecular-weight complexes is longer than previously estimated. The barrier is widely open during the first 40 minutes after osmotic BBB disruption and returns to baseline levels only after 6 to 8 hours following the induction of good or excellent disruption. These findings have important clinical implications for the design of therapeutic protocols.

In vivo model of intracranial stent implantation: a pilot study to examine the histological response of cerebral vessels after randomized implantation of heparin-coated and uncoated endoluminal stents in a blinded fashion

2003 ◽  
Vol 98 (3) ◽  
pp. 544-553 ◽  
Author(s):  
Elad I. Levy ◽  
Alan S. Boulos ◽  
Ricardo A. Hanel ◽  
Fermin O. Tio ◽  
Ronald A. Alberico ◽  
...  
Keyword(s):  
Stent Implantation ◽  
In Vivo Model ◽  
Content Type ◽  
Intracranial Stent ◽  
Neointimal Thickness ◽  
Neointimal Proliferation ◽  
The Mean ◽  
Endoluminal Stent ◽  
Fine Print

Object. No animal model currently exists for the examination of time-dependent histological changes occurring in intracranial vessels after endoluminal stent placement. The authors' goal was to develop a reproducible in vivo model of stent implantation in intracranial vessels in dogs that was capable of demonstrating stent-related vascular changes after the implantation of coated and uncoated devices. Methods. The authors implanted heparin-coated or uncoated stents in the basilar arteries (BAs) of 11 mongrel dogs. In a 12th animal, one coated stent was implanted in the BA and a second uncoated one was implanted in the distal anterior spinal artery. All the devices were oversized to induce intimal injury. Surviving animals were observed for 12 weeks, after which they underwent repeated angiography before planned death and removal of the brain. Histological studies and computer-assisted morphometric analyses were conducted on stent-treated and untreated sections of the BAs to assess the percentage of stenosis, neointimal proliferation, vessel injury, and inflammation. Perforating vessels partially covered by stent struts (“jailing”) were studied for evidence of stenosis or occlusion. The pathologist, interventionists, histopathologist, histopathology technicians, and radiologist were blinded to the stent type. Seven stents (three uncoated and four coated) were removed from the six animals that were observed during the follow-up period. The mean neointimal proliferation was 0.42 mm2 in the group treated with uncoated stents and 0.18 mm2 in the group treated with heparin-coated devices (p = 0.04). Neointimal thickness was significantly increased in the group with uncoated stents (p = 0.04). The mean percentage of occlusion was less (12%) in the group with heparin-coated stents, compared with 22% in the group with uncoated devices (p = 0.07). When comparing results between the heparin-coated and uncoated devices implanted in the five animals that received a single stent only, greater differences (indicating a benefit from heparin-coated stents) were observed in neointimal area (p = 0.009), neointima/media ratio (p = 0.001), neointimal thickness (p = 0.002), and percentage of occlusion (p = 0.009). All brainstem perforating vessels covered by stent struts remained patent. Conclusions. This in vivo intracranial stent model was developed to assess proliferative and inflammatory responses to endoluminal stent implantation in the cerebrovasculature. The results indicate that a lower percentage of occlusion occurs 12 weeks after implantation of heparin-coated compared with uncoated stents.

Experimental feline hydrocephalus

1985 ◽  
Vol 63 (1) ◽  
pp. 82-87 ◽  
Author(s):  
Kenneth Shapiro ◽  
Futoshi Takei ◽  
Arno Fried ◽  
Ira Kohn
Keyword(s):  
Steady State ◽  
Volume Index ◽  
Control Group ◽  
Moderate Increase ◽  
Content Type ◽  
The Mean ◽  
Dural Opening ◽  
Container Model ◽  
Csf Absorption ◽  
Fine Print

✓ In a craniectomy-durectomy model of kaolin-induced feline hydrocephalus, the pressure-volume index (PVI) technique of bolus manipulations of cerebrospinal fluid (CSF) was used to study the biomechanical changes associated with hydrocephalus. Steady-state intracranial pressure (ICP), PVI, and the resistance to the absorption of CSF were determined acutely and 3 to 5 weeks later in hydrocephalic cats and time-matched control cats. Steady-state ICP was 11.0 ± 2.1 mm Hg (± standard deviation) in the hydrocephalic cats, compared to 10.8 ± 2.2 mm Hg in the chronic control group (p > 0.1). The ICP in both the chronic hydrocephalic and chronic control groups was significantly higher (p < 0.001) than after acute durectomy (mean ICP 8.5 ± 1.2 mm Hg). Immediately after dural opening, the mean PVI was 3.6 ± 0.2 ml (± standard error of the mean); over time, it decreased to 1.3 ± 0.1 ml in the chronic control group (p < 0.001), but remained elevated in the hydrocephalic group at 3.5 ± 0.4 ml (p < 0.001). Resistance to CSF absorption was 9.1 ± 1.4 mm Hg/ml/min immediately after dural opening and increased to 28.8 ± 4.5 mm Hg/ml/min (p < 0.001) in the hydrocephalic cats; it increased even further in the chronic measurements in control cats, to 82.3 ± 9.2 mm Hg/ml/min (p < 0.001). Ventricular size was moderate to severely enlarged in all hydrocephalic cats, and normal in the control group. These results indicate that the biomechanical profile of the altered brain container model of kaolin-induced feline hydrocephalus resembles that described in hydrocephalic infants. As shown in the control subjects, an absorptive defect alone is not sufficient to cause progressive ventricular enlargement. Increased volume-buffering capacity coupled with a moderate increase of CSF absorption resistance facilitates volume storage in the ventricles.

Antitumor activity of the growth hormone receptor antagonist pegvisomant against human meningiomas in nude mice

2001 ◽  
Vol 94 (3) ◽  
pp. 487-492 ◽  
Author(s):  
Ian E. McCutcheon ◽  
Allan Flyvbjerg ◽  
Holly Hill ◽  
Jessica Li ◽  
William F. Bennett ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Receptor Antagonist ◽  
Tumor Volume ◽  
Vehicle Group ◽  
Content Type ◽  
Gh Receptor ◽  
Igf I ◽  
The Mean ◽  
Fine Print

Object. The authors have previously demonstrated that modulation of the growth hormone (GH)/insulin-like growth factor-I (IGF-I) axis can significantly affect meningioma growth in vitro. These studies were performed to evaluate the efficacy of GH receptor blockade in vivo. Methods. Primary cultures from 15 meningioma tumors obtained in humans were xenografted into athymic mice. Approximately 1.5 million cells from each of the 15 tumors were implanted into the flanks of two female mice, one pair for each tumor. One animal from each of the 15 pairs was then treated with the GH receptor antagonist pegvisomant and the other with vehicle alone for 8 weeks. The tumor volume was measured using digital calipers three times per week. The mean tumor volume at the initiation of injections was 284 ± 18.8 mm3 in the vehicle group and 291.1 ± 20 mm3 in the pegvisomant group. After 8 weeks of treatment, the mean volume of tumors in the pegvisomant group was 198.3 ± 18.9 mm3 compared with 350.1 ± 23.5 mm3 for the vehicle group (p < 0.001). The serum IGF-I concentration in the vehicle group was 319 ± 12.9 µg/L compared with 257 ± 9.7 in the pegvisomant group (p < 0.02). A small but significant decrease was observed in circulating IGF binding protein (IGFBP)—3 levels, whereas slight increases occurred with respect to serum IGFBP-1 and IGFBP-4 levels. In the placebo group the tumor weight was 0.092 ± 0.01 g compared with 0.057 ± 0.01 g in the pegvisomant group (p < 0.02). The IGF-I and IGF-II concentrations were measured in the tumors by using a tissue extraction method. These human-specific immunoassays demonstrated that there was no autocrine production of IGF-I in any of the tumors, either in the pegvisomant or vehicle group. The IGF-II levels were highly variable (0–38.2 ng/g tissue) and did not differ significantly between treatment groups. Conclusions. In an in vivo tumor model, downregulation of the GH/IGF-I axis significantly reduces meningioma growth and, in some instances, causes tumor regression. Because the concentrations of IGF-II in tumor did not vary with pegvisomant treatment and there was no autocrine IGF-I production by the tumors, the mechanism of the antitumor effect is most likely a decrease of IGF-I in the circulation and/or surrounding host tissues. Because the authors have previously demonstrated that the GH receptor is ubiquitously expressed in meningiomas, direct blockade of the GH receptor on the tumors may also be contributing to inhibitory actions.

Management of cerebellar ptosis following craniovertebral decompression for Chiari I malformation

2001 ◽  
Vol 94 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Langston T. Holly ◽  
Ulrich Batzdorf
Keyword(s):  
Symptom Relief ◽  
Chiari I Malformation ◽  
Neurological Deficits ◽  
Specific Patient ◽  
Content Type ◽  
Shunt Placement ◽  
Suboccipital Craniectomy ◽  
Chiari I ◽  
The Mean ◽  
Fine Print

Object. In this report the authors review their experience in the treatment of seven patients with symptomatic cerebellar ptosis following craniovertebral decompression (CVD) for Chiari I malformation. Methods. The mean age of the patients was 37 years and the average amount of time between the initial suboccipital craniectomy and evaluation for cerebellar ptosis was 6.8 years. Five patients presented primarily with intractable headache and the remaining two patients with neurological deficits caused by recurrent syringomyelia. Three different surgical modalities were used to treat these patients: ventriculoperitoneal shunt placement (one patient), syringoperitoneal shunt placement (two patients), and partial suboccipital cranioplasty with or without intradural exploration (four patients). The mean follow-up period was 51 months. The three patients who underwent shunt placement procedures experienced poor results, with no evidence of symptom relief and continued neurological deterioration. In contrast, all four patients who underwent cranioplasty experienced good or excellent clinical outcomes. Postoperative magnetic resonance imaging studies revealed a reduction in the size of the syrinx cavity in patients who simultaneously underwent intradural exploration. Conclusions. The emergence of symptomatic cerebellar ptosis following CVD for Chiari I malformation is primarily caused when the suboccipital craniectomy is too large for the specific patient. The cerebellar ptosis usually presents with severe headache and/or neurological deficit due to persistent or recurrent syringomyelia. Partial suboccipital cranioplasty, with or without intradural exploration, is effective in treating this condition.

Quantification of in vivo Photofrin uptake by human pituitary adenoma tissue

2004 ◽  
Vol 101 (2) ◽  
pp. 272-277 ◽  
Author(s):  
Usiakimi Igbaseimokumo
Keyword(s):  
Photodynamic Therapy ◽  
Pituitary Adenoma ◽  
The Body ◽  
Human Pituitary ◽  
Human Pituitary Adenoma ◽  
Content Type ◽  
The Mean ◽  
Adenoma Tissue ◽  
Fine Print

Object. Photofrin is widely distributed in the body after intravenous injection. This study was designed to quantify the preferential uptake of Photofrin by pituitary adenoma tissue for intraoperative photodynamic therapy. Methods. Eight patients (seven men) with recurrent pituitary adenomas who had undergone previous surgery and radiation therapy were recruited for a Phase I/II feasibility study of the application of photodynamic therapy to pituitary tumors. Photofrin was administered intravenously at a dose of 2 mg/kg body weight 48 hours before repeated transsphenoidal hypophysectomy was performed. At the time of the operation, pituitary adenoma tissue, muscle, fat, skin, and plasma were obtained for measurement of Photofrin content by fluorometric assay. The mean Photofrin level in pituitary adenoma tissue was 6.87 ng/mg (95% confidence interval [CI] 3.99–9.75), which was significantly higher than the uptake by skeletal muscle (2.24 ng/mg, 95% CI 1.28–3.2; p = 0.008), or fat (2.54 ng/mg, 95% CI 0.66–4.42; p = 0.007). Nevertheless, the mean drug concentration in pituitary adenoma tissue was not significantly different from the level in plasma (7.65 µg/ml, 95% CI 5.38–9.90; p = 0.558). Skin specimens were available in four patients, and these showed a mean uptake of 2.19 ng/mg. Conclusions. Photofrin is preferentially retained by pituitary adenoma tissue to levels both adequate for intraoperative photodynamic therapy and approximately 50% higher than those reported for gliomas.

Pressure-volume relationships in shunt-dependent childhood hydrocephalus

1986 ◽  
Vol 64 (3) ◽  
pp. 390-396 ◽  
Author(s):  
Kenneth Shapiro ◽  
Arno Fried
Keyword(s):  
Normal Pressure ◽  
Buffering Capacity ◽  
Volume Index ◽  
Content Type ◽  
Proximate Cause ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Neural Axis ◽  
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 absorption of CSF (Ro) in 20 shunt-dependent hydrocephalic children acutely ill from shunt malfunction. All children had had ventricles that were near normal or subnormal in size when the shunts were functioning. The mean intracranial pressure (ICP, ± standard deviation (SD)) at the time of revision was 10.6 ± 6.4 mm Hg. The mean measured PVI (± standard error of the mean) was 18.4 ± 1.1 ml compared to the normal PVI of 17.5 ± 4.4 ml (± SD) predicted for these children. According to paired t-tests, these measured values were similar to those predicted on the basis of neural axis volume for each child, indicating that these children had normal neural axis volume buffering capacity. While the study was in progress, abrupt increases of ICP were documented in all children. These waves were observed spontaneously as well as in response to the addition of volume to the neural axis. In each child a specific threshold pressure along the pressure-volume curve corresponded to the appearance of unstable ICP. The threshold pressures at which this occurred corresponded to a mean neural axis compliance of 0.32 ± 0.07 ml/mm Hg (± SD). The Ro varied as a function of ICP. The Ro measured at ICP's below 15 mm Hg ranged from 2 to 7.5 mm Hg/ml/min and rose to 12 to 30 mm Hg/ml/min at pressures in the 20 to 25 mm Hg range. The results of this study indicate that neural axis volume buffering capacity is normal in shunt-dependent children who respond to shunting by reconstitution of the cortical mantle. This study indicates that the proximate cause of their abrupt clinical deterioration is unstable ICP, which occurred at a similar point on the pressure-volume curve of all children studied. The correlation of Ro to ICP suggests that CSF absorption does not increase in these children as ICP rises, resulting in movement along relatively normal pressure-volume curves. The functional implications of these parameters are discussed.

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.

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