Diffusion tensor imaging and ventricle volume quantification in patients with chronic shunt-treated hydrocephalus: a matched case-control study

OBJECTIVEThe object of this study was to use diffusion tensor imaging (DTI) and tract-based spatial statistics (TBSS) to characterize the long-term effects of hydrocephalus and shunting on white matter integrity and to investigate the relationship of ventricular size and alterations in white matter integrity with headache and quality-of-life outcome measures.METHODSPatients with shunt-treated hydrocephalus and age- and sex-matched healthy controls were recruited into the study and underwent anatomical and DTI imaging on a 3-T MRI scanner. All patients were clinically stable, had undergone CSF shunt placement before 2 years of age, and had a documented history of complaints of headaches. Outcome was scored based on the Headache Disability Inventory and the Hydrocephalus Outcome Questionnaire. Fractional anisotropy (FA) and other DTI-based measures (axial, radial, and mean diffusivity; AD, RD, and MD, respectively) were extracted in the corpus callosum and internal capsule with manual region-of-interest delineation and in other regions with TBSS. Paired t-tests, corrected with a 5% false discovery rate, were used to identify regions with significant differences between patients and controls. Within the patient group, linear regression models were used to investigate the relationship between FA or ventricular volume and outcome, as well as the effect of shunt-related covariates.RESULTSTwenty-one hydrocephalus patients and 21 matched controls completed the study, and their data were used in the final analysis. The authors found significantly lower FA for patients than for controls in 20 of the 48 regions, mostly posterior white matter structures, in periventricular as well as more distal tracts. Of these 20 regions, 17 demonstrated increased RD, while only 5 showed increased MD and 3 showed decreased AD. No areas of increased FA were observed. Higher FA in specific periventricular white matter tracts, tending toward FA in controls, was associated with increased ventricular size, as well as improved clinical outcome.CONCLUSIONSThe study shows that TBSS-based DTI is a sensitive technique for elucidating changes in white matter structures due to hydrocephalus and chronic CSF shunting and provides preliminary evidence that DTI may be a valuable tool for tailoring shunt procedures to monitor ventricular size following shunting and achieve optimal outcome, as well as for guiding the development of alternate therapies for hydrocephalus.

Use of a customized 3D "basket" to create a solitary split-thickness cranial graft from numerous split fragments in an infant

While autologous split calvaria remains the preferred material for use in pediatric cranioplasty, it may be difficult to split the bone neatly into two distinct pieces, especially in infants and young children. In this paper, the authors present a technique in which numerous split pieces of bone can be readily joined together and conformed to the shape of the specific defect using a customized template and 3D trellis-like basket.

The Reverend Russell H. Conwell, W. Wayne Babcock, and the “soup bone” cranioplasties of 1915

In 1915, faced with 2 patients with large skull defects, W. Wayne Babcock, an obstetrician-gynecologist-turned-general surgeon, operating in a modest North Philadelphia hospital, did something extraordinary: he went to the hospital kitchen to look for a cranial graft. Based heavily on archival and other primary sources, the authors tell the remarkable tale of the “soup bone” cranioplasties of the Samaritan Hospital and place these operations within the context of the early modern American hospital.

Successful treatment of post-shunt craniocerebral disproportion by coupling gradual external cranial vault distraction with continuous intracranial pressure monitoring

A subset of hydrocephalic patients in whom shunts are placed at an early age will develop craniocerebral disproportion (CCD), an iatrogenic mismatch between the fixed intracranial volume and the growing brain. The lack of a reliable, reproducible method to diagnose this condition, however, has hampered attempts to treat it appropriately. For those practitioners who acknowledge the need to create more intracranial space in these patients, the lack of agreed-upon therapeutic end points for cranial vault expansion has limited the use of such techniques and has sometimes led to problems of underexpansion. Here, the authors present a definition of CCD based primarily on the temporal correlation of plateau waves on intracranial pressure (ICP) monitoring and headache exacerbation. The authors describe a technique of exploiting continued ICP monitoring during progressive cranial expansion in which the goal of distraction is the cessation of plateau waves. Previously encountered problems of underexpansion may be mitigated through the simultaneous use of ICP monitors and gradual cranial expansion over time.

Infections of the spinal subdural space in children: a series of 11 contemporary cases and review of all published reports. A multinational collaborative effort

INTRODUCTION

Positioned anatomically between the spinal epidural space and the intramedullary compartment, the spinal subdural space remains the least common area of localized infection in the central nervous system. Infectious processes of the subdural spinal space include subdural spinal empyema, subdural spinal abscess, infected spinal subdural cyst, and infectious spinal subdural cyst. To date, there has been no systematic review of these entities in children, with the cumulative knowledge of the pathophysiologic, microbiologic, and demographic characteristics of these infections relegated solely to few small series and case reports.

METHODS

A series of 11 recent cases culled from the collaboration of international authors are presented. In addition, an exhaustive MEDLINE search and manual review of the international literature was performed, identifying a total of 73 cases of spinal subdural infections in patients under the age of 21. Data of interest include the age, sex, signs, and symptoms at presentation, spinal location of infection, presence of spinal dysraphism, and other comorbidities, offending organism, treatment, outcome, and follow-up.

RESULTS

Patients ages ranged from 4 weeks to 20 years (mean, 6.5 years). Males outnumbered females by a ratio of 2:1. Over half (53 %) of spinal subdural infections in children were associated with spinal dysraphism or other congenital abnormalities of the spine. The commonest organism to infect the spinal subdural space in children is mycobacterium tuberculosis and the thoracic spinal region was most commonly infected.

CONCLUSIONS

The disease is usually treated surgically, although a more expectant approach consisting of antibiotics and observation has also been proposed.

A review of reconstructive materials for use in craniofacial surgery bone fixation materials, bone substitutes, and distractors

Over the last 40 years, craniofacial surgery, in general, and surgery for craniosynostosis, in particular, has witnessed the introduction of a number of new materials for use in operations involving the cranial vault. Some of these materials have proven quite useful over time, while others have failed to meet their stated objectives. In this review, the more popular implant materials are analyzed, and their relative merits and drawbacks are discussed. Craniofacial surgery in the pediatric population has its own unique limitations, quite different from the adult population and those issues are reviewed as well.

Marvelous medicine: the untold story of the Wade-Dahl-Till valve

On December 5, 1960, 4-month-old Theo Dahl, the only son of best-selling author Roald Dahl (1916-1990), had his skull shattered in a horrific traffic accident. What began as a personal tragedy for the Dahl family would soon evolve into a dogged crusade by Dahl to expand upon preexisting valve technology with the goal of developing a shunt that would not become obstructed. Based upon exclusive access to private archives of the Dahl estate, as well as interviews with those involved, this article tells the intricate tale of one famous father's drive to significantly alter the natural history of pediatric hydrocephalus. Dahl's collaboration with British toymaker Stanley Wade and pioneering pediatric neurosurgeons Joseph Ransohoff, Kenneth Shulman, and Kenneth Till to create the Wade-Dahl-Till (WDT) valve is examined in detail. The ensuing rift between the American and British contingents, the valve's multiple design revisions, and the goal of creating an affordable shunt for children in developing countries are among the issues addressed. The development of the WDT valve marked a significant turning point in the surgical management of pediatric hydrocephalus in general and in shunt valve technology in particular.

The role of adenosine in hypercarbic hyperemia: in vivo and in vitro studies in adenosine 2(A) receptor knockout and wild-type mice

OBJECT

The authors tested the hypothesis that adenosine, acting through the A(2A) receptor, is not involved in hypercarbic hyperemia by assessing the effects of increased PaCO(2) on cerebral blood flow (CBF) in vivo in wild-type and A(2A) receptor knockout mice. In addition, they evaluated the effect of abluminal pH changes in vitro on the diameter of isolated perfused penetrating arterioles harvested from wild-type and A(2A) receptor knockout mice.

METHODS

The authors evaluated in a blinded fashion the CBF response during transient (60-second) hypercapnic (7% CO(2)) hypercarbia in anesthetized, ventilated C57Bl/6 wild-type and adenosine A(2A) receptor knockout mice. They also evaluated the hypercarbic response in the absence and presence of the nonselective and selective adenosine antagonists.

RESULTS

Cerebral blood flow was measured using laser Doppler flowmetry. There were no differences between the CBF responses to hypercarbia in the wild-type and the knockout mice. Moreover, the hypercarbic hyperemia response was not affected by the adenosine receptor antagonists. The authors also tested the response to alteration in abluminal pH in isolated perfused, pressurized, penetrating arterioles (average diameter 63.3 +/- 3.6 microm) harvested from wild-type (6 mice) and knockout (5 mice) animals. Arteriolar dilation in response to a decrease in abluminal pH, simulating the change in vivo during hypercarbia, was similar in wild-type (15.9 +/- 2.6%) and A(2A) receptor knockout (17.7 +/- 1.3%) mice. With abluminal application of CGS 21680 (10(-6) M), an A(2A) receptor agonist, wild-type arterioles dilated in an expected manner (9.8 +/- 0.7%), whereas A(2A) receptor knockout vessels had minimal response.

CONCLUSIONS

The results of the in vivo and in vitro studies in wild-type and A(2A) receptor knockout mice support the authors' hypothesis that hypercarbic vasodilation does not involve an adenosine A(2A) receptor-related mechanism.

Regulation of cerebral vasculature in normal and ischemic brain

We outline the mechanisms currently thought to be responsible for controlling cerebral blood flow (CBF) in the physiologic state and during ischemia, focusing on the arterial pial and penetrating microcirculation. Initially, we categorize the cerebral circulation and then review the vascular anatomy. We draw attention to a number of unique features of the cerebral vasculature, which are relevant to the microcirculatory response during ischemia: arterial histology, species differences, collateral flow, the venous drainage, the blood-brain barrier, astrocytes and vascular nerves. The physiology of the arterial microcirculation is then assessed. Lastly, we review the changes during ischemia which impact on the microcirculation. Further understanding of the normal cerebrovascular anatomy and physiology as well as the pathophysiology of ischemia will allow the rational development of a pharmacologic therapy for human stroke and brain injury.