The CSF accumulator.

The ability of the central nervous system (CNS) to store and release fluid energy plays an important role in both health and disease. The stored fluid energy is the product of the fluid volume and pressure. How changes in CNS fluid (CSF, blood, or extracellular fluid) energy are distributed is determined by the compliance of the fluid containers and their arrangement. Hydrocephalus and related diseases not only interfere with the absorption of CSF but also interfere with the exchange of CSF in response to positional changes, cardiorespiratory and intraperitoneal energy changes. While shunts allow for the diversion of CSF when the intracranial energy exceeds the absorbing receptacle energy, they do not normalize the return of CSF to the intracranial compartment as needed with the intracranial blood volume or pressure decreases (the accumulator function of the CNS's CSF). A CSF shunt that has an artificial accumulator proximal to the valve can potentially restore the accumulator function towards normal and prevent some of the complications associated with CSF overdrainage.

Cerebrospinal fluid flow through an implanted shunt.

Although the circulation of cerebrospinal fluid enjoys an apparent simplicity, its underlying basis is amazingly complex. Many factors influence how CSF flows through the human central nervous system. In the presence of hydrocephalus and subsequent shunt placement, this system is further complicated. The challenge before us then is to advance our understanding of the mechanisms that underlie CSF circulation, to place within that context the implications of shunt dependency, and to design a shunt system capable of simultaneous redirection of CSF and restoration of the CNS toward normal. Such a new shunt system would have to overcome not only those complications that result from hydrocephalus, but also those that result from the shunt's very placement. The purpose of this publication is 1. to provide an overview of the CSF circulatory system in the context of hydrocephalus and shunt dependency; 2. to explore resultant complications within the framework of those factors that influence CSF circulation within the human biological system as well as those that arise from the factors that influence CSF flow through a shunt; and 3. to propose in brief an alternative shunt valve designed to restore the accumulator function of the CNS toward normal.

Hydrocephalus and the reproductive health of women: the medical implications of maternal shunt dependency in 70 women and 138 pregnancies.

An increasing number of women with cerebrospinal fluid shunts are surviving to child-bearing age, and are making independent decisions in regard to planning their families. As a result, a broad range of interdisciplinary health care professionals will require information about the management of these patients, especially during pregnancy and delivery. The purpose of this ongoing study is to gather comprehensive data from shunted women regarding their clinical history during pregnancy and within the six-month post-partum period. As part of this study, the following questions were addressed: 1. How does maternal shunt dependency influence the course of pregnancy and pregnancy outcomes? 2. What neurosurgical complications characterize this population of patients? 3. What complications of shunt dependency influence obstetrical management including pre-natal testing and delivery? 4. What are the implications of shunt dependency with respect to general reproductive health concerns within this population? A total of 70 respondents, 18-41 years old and accounting for 138 pregnancies, completed a questionnaire providing information on maternal background, medical history, shunt performance during pregnancy, management of delivery, pregnancy outcomes, and unusual complications. One hundred three (103) pregnancies resulted in 105 live births including two surviving sets of twins; of these, 84 occurred in women with ventriculoperitoneal shunts (including both mothers who gave birth to live twins). Four women underwent therapeutic abortions, five delivered pre-term, one mother delivered a stillborn infant, and 16 experienced 32 miscarriages (including two ectopic pregnancies, and 33 fetal losses). Three women had seizures during pregnancy. Nine mothers reported an increase in headache activity during pregnancy. Twelve described abdominal pains during the course of pregnancy with anecdotal reports of increased frequency of painful episodes during the first and third trimesters. Twelve babies were diagnosed with congenital defects, including one pair of fraternal twins individually diagnosed with symmetric parietal foramina. Seven additional children were diagnosed with developmental disabilities including attention deficit disorder (ADD), attention deficit hyperactivity disorder (ADHD), pervasive developmental delay (PDD), and autism. Shunt malfunctions and revisions occurred seven times (four women) during pregnancy, and in 24 pregnancies (13 women) within six months of delivery. One malfunction and revision followed the miscarriage of twins at 12 gestational weeks. No acute malfunctions requiring immediate revision occurred during delivery, although two women reported severe headaches during labor. Transient signs of raised intracranial pressure occurred in 15 mothers over the course of 19 pregnancies which did not require surgical revision of the shunt following delivery or termination of pregnancy. No signs of shunt malfunction were identified in 100 of the pregnancies described in this series; 31 of these resulting in miscarriage and 69 resulting in live births. This study extends observations made previously to a larger population of shunt dependent mothers, and nearly doubles the amount of data available in our last publication. The results suggest that maternal shunt dependency carries a relatively high incidence of complications for some patients, but that proper management of these patients can lead to normal pregnancy and delivery.

Maternal shunt dependency: implications for obstetric care, neurosurgical management, and pregnancy outcomes and a review of selected literature.

OBJECTIVE: Because more women with cerebrospinal fluid shunts are surviving to child-bearing age, neurosurgeons, obstetricians, and other health care professionals require information about the care of these patients, especially during pregnancy and delivery. The purpose of this study was to gather comprehensive data from women with shunts regarding their clinical histories during and immediately after pregnancy. The following questions were addressed. 1) How does maternal shunt dependency influence the course of pregnancies and pregnancy outcomes? 2) What neurosurgical complications characterize this population of patients? 3) What complications of shunt dependency influence obstetric management, including prenatal testing and delivery? METHODS: A total of 37 respondents (age, 18-41 yr), accounting for 77 pregnancies, completed a questionnaire providing information on maternal background and medical history, shunt performance during pregnancy, management of delivery, pregnancy outcomes, and unusual complications. RESULTS: Fifty-six pregnancies resulted in live births; of these, 47 occurred in women with ventriculoperitoneal shunts. Three women underwent therapeutic abortions, 1 experienced preterm delivery, and 8 experienced 17 miscarriages. Four women experienced seizures during pregnancy, five reported third-trimester headaches, and eight described abdominal pains during the first and third trimesters. Four babies were diagnosed as having congenital defects. Shunt malfunctions and revisions occurred 10 times in 7 women, either during pregnancy or within 6 months after delivery. No acute malfunctions occurred during delivery. Forty-seven cases, representing 84% of all pregnancies, exhibited no shunt malfunctions or revisions. CONCLUSION: This study extends previous observations to a larger population of shunt-dependent mothers. The results suggest that maternal shunt dependency entails a relatively high incidence of complications but that proper care of these patients can lead to normal pregnancies and deliveries.

The CSF accumulator: its role in the central nervous system and implications for advancing hydrocephalus shunt technology.

The 'cerebrospinal fluid (CSF) accumulator' plays an important physiological role in the healthy central nervous system as both a shock absorber and regulator of drainage. In the presence of hydrocephalus, this function is compromised by resistance to the flow of CSF. It is further compromised by the placement of a standard shunt which allows only for one-way directional diversion of the fluid. Complications associated with shunt dependency may be a direct consequence of both the condition, and a failure of existing systems to restore the normal accumulator function. This article reviews the pathophysiology of the 'CSF accumulator' as it relates to hydrocephalus and its management, and proposes a biomimetic shunt designed to restore the 'CSF accumulator' toward normal. It is hoped that such a device will support normalization of intracranial pressure and restore an appropriate level of CSF volume in the shunted patient.