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Biomedical subjects

G Magram

Publications and source records attributed to G Magram.

16 recordsLinked to original sources
PubMed2000

Magnetic resonance cystography with gadopenetate dimeglumine of a cystic craniopharyngioma in a child - a technical note.

Large cystic craniopharyngiomas can be treated with chemotherapy injected directly into the cyst. Chemotherapy is toxic if it leaks from the cyst into the subarachnoid space. We present a child with a cystic craniopharyngioma following surgical placement of a catheter into the cystic component. Computed tomography following iodinated contrast injection into the cyst was inconclusive in determining the cyst wall integrity. Magnetic resonance following dilute gadopentetate dimeglumine injection into the cyst clearly defined a leak into the subarachnoid space. Coronal imaging was especially helpful. This technique is simple to perform and useful for clinical management.

Child, Preschool↗
PubMed2000

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.

Central Nervous System↗
PubMed2000

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.

Central Nervous System↗
PubMed2000

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.

Abortion, Spontaneous↗
PubMed1998

Intracranial pressure waveform analysis: computation of pressure transmission and waveform shape indicators.

We studied transmission of arterial blood pressure to intracranial pressure by observing how the two pressure waveforms varied from baseline conditions to after postural change or jugular compression. Such experiments may lead to pressure waveform-based estimates of intracranial compliance. Using a single database of arterial blood pressure, central venous pressure, and intracranial pressure waveforms collected during baseline, jugular compresison, and head-elevated conditions from six Yucatan minipigs, we computed several numerical indicators of waveform shape to find an estimator of intracranial compliance. Of these indicators, two were based on the Fourier-decomposition of all three waveforms, and one was based on a new method for approximating the systolic slope of the intracranial pressure waveform. We computed amplitude transfer functions for the first six harmonics of the Fourier spectrum, treating intracranial pressure as system output and independently treating arterial blood pressure and central venous pressure as system inputs. Using these same inputs and outputs, we computed a single quotient based on the Fourier coefficients of the first six harmonics of the input and output waveforms. Finally, applying a Gaussian high-pass filter, we computed systolic slope approximations for all intracranial pressure wave cycles contained in a single respiratory cycle. Our third indicator was the mean-normalized variation of the slope approximations over a respiratory cycle. We studied how each composite at baseline varied with baseline mean intracranial pressure and how each composite changed from baseline as a result of a physical manipulation. Our analysis suggests that the composite based on respiratory variation of systolic slope approximations was positively correlated with mean intracranial pressure during baseline. The quotient based on Fourier coefficients with arterial blood pressure input seemed to increase from baseline to jugular compression. Composites that treated central venous pressure as input were both less correlated with mean intracranial pressure during baseline and exhibited less predictable changes from baseline to a physical manipulation than their counterparts that used arterial blood pressure as input. However, none of these apparent trends was statistically significant. The lack of statistically significant results may be due to the nature of the composites and/or the small sample size (n = 6). However, we hope this study stimulates further investigation of both central venous pressure-to-intracranial pressure (in addition to arterial blood pressure-to-intracranial pressure) transfer and automated computation of intracranial pressure waveform systolic slope. Such research may lead to noninvasively determined estimators of intracranial compliance.

Animals↗
PubMed1998

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.

Adolescent↗
PubMed1997

Chiari malformation and tonsillar ectopia in twin brothers and father with autosomal dominant spondylo-epiphyseal dysplasia tarda.

We describe twin brothers and father with autosomal dominant spondylo-epiphyseal dysplasia (SED) tarda. The proband presented at 17 years with nystagmus and esotropia due to a severe Chiari malformation. A milder, asymptomatic Chiari I malformation was seen in his brother and tonsillar ectopia in his father. Although these malformations have not been described in patients with SED, they are relatively common in other bony abnormalities, particularly those involving the cranio-cervical junction. The concordance of the Chiari malformations or tonsillar ectopia in all three family members with SED suggests that this association is not coincidental. It seems possible that the downward displacement of the cerebellum occurs secondary to primary osseous abnormality, rather than due to a primary disturbance of embryological development. The lack of additional brain malformations in our patients is consistent with this theory.

Adolescent↗
PubMed1997

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.

Adult↗
PubMed1995

A cerebrospinal fluid shunt: a theoretical concept.

An innovative shunt design for the treatment of hydrocephalus is discussed. It is based on a two-tube configuration which restores accumulator function to suppress intracranial pressure fluctuations emanating from the brain and resulting from changes in the subject's postural position. Current shunt problems of overdrainage, occlusion, and infection are addressed and corrections inherent in the proposed design are described. Specific materials and characteristics for the construction of the proposed design are suggested.

Catheters, Indwelling↗
PubMed1994

Pediatric medication order error rates related to the mode of order transmission.

OBJECTIVE: This study was undertaken to measure the medication error rates associated with verbal orders compared with handwritten and computer-entered orders in an acute-care children's hospital. METHODS: All medication and intravenous fluid orders for a 3-month interval were entered into a computer database. For the same interval, all errors pertaining to the transmission of a medication or intravenous fluid order were also entered into the database. Errors were detected by the hospital pharmacy, which continuously reviews all inpatient medication and intravenous fluid orders for potential errors before dispensing. Errors were also detected by nurses on the floors, who submit incident reports when medication or intravenous fluid errors occur. RESULTS: Verbal orders were associated with significantly lower error rates than either handwritten orders or computer-entered orders (2.6, 8.5, and 6.3 per 1000, respectively), with transcription errors and dosage errors in particular being reduced. Total error rates did not differ between residents and attending physicians. Error rates did not differ between verbal, written, and computer orders for medications with a low frequency of verbal orders and therefore presumed greater complexity. However, the verbal order error rates seemed more sensitive to order complexity than order error rates in general. CONCLUSIONS: The hypothesis that verbal orders are more prone to transmission error than written or computer orders is not supported by the findings in this study. Identifying medications with high levels of order complexity for restriction of verbal order use seems justified. Suggested guidelines for verbal order transmission are presented.

Child↗