PubMed Health⌕ Search

Biomedical subjects

Gerald A Grant

Publications and source records attributed to Gerald A Grant.

9 recordsLinked to original sources
PubMed2026

Chiari I malformation.

Chiari I malformation (CM1), the most common structural hindbrain disorder in humans, is traditionally characterized by the downward displacement of the cerebellar tonsils through the foramen magnum. However, this definition does not reflect the variability in clinical presentation, natural history and treatment response of this disorder. Some individuals with minimal tonsillar descent have severe neurological symptoms and syringomyelia, whereas others with extensive descent remain asymptomatic. Emerging evidence from neuroimaging, developmental biology and human genetics indicates that CM1 is not a single anatomical entity but a spectrum of disorders resulting from disruptions in coordinated growth and homeostasis across the cerebellum, posterior fossa, craniocervical junction, cerebrospinal fluid and neurovascular systems. CM1 may be best understood as a disorder of disrupted developmental scaling, in which the tightly regulated relationships between cerebellar growth and cranial accommodation are altered within a dynamic neurovascular and cerebrospinal fluid environment. In this context, tonsillar herniation is a geometric consequence rather than the primary disease process. This Primer synthesizes current knowledge on the epidemiology, mechanisms, diagnosis and management of CM1 across the lifespan. We highlight advances in neuroimaging, genomics and phenomics that support a shift from anatomy-based definitions towards an integrated genomic-phenomic classification.

Humans↗
PubMed2004

MR neurography: diagnostic utility in the surgical treatment of peripheral nerve disorders.

Advances in MR imaging have improved the visualization of normal and pathologic peripheral nerve structures in various clinical settings. Peripheral nerve imaging has the potential to dramatically change the diagnosis and treatment of peripheral nerve pathology and lead to an improved understanding of peripheral nerve pathophysiology. Currently, MR imaging serves as a problem-solving tool when additional anatomic information is needed to clarify ambiguous electrodiagnostic and clinical examinations. The next major advance in MR imaging of peripheral nerves will likely be the transition from anatomic to physiologic imaging with higher resolution as better phased-array surface coils and higher-field-strength magnets become available. Finally, MR neurography should remain complementary to the clinical examination and electrodiagnostic studies in the evaluation of peripheral nerve disorders.

Electrodiagnosis↗
PubMed2004

Failure of autologous bone-assisted cranioplasty following decompressive craniectomy in children and adolescents.

OBJECT: The authors have routinely performed primary autologous cranioplasty to repair skull defects after decompressive craniectomy. The high rates of subsequent bone resorption occurring in children prompted this study. METHODS: In an institutional review, the authors identified 40 (32 male and eight female) children and adolescents ranging from 4 months to 19 years of age in whom autologous cranioplasty was performed after decompressive craniectomy. The defect surface area ranged from 14 to 147 cm2. In all cases, the bone was fresh frozen at the time of the decompression. Symptomatic bone resorption subsequently occurred in 20 children (50%) in all of whom reoperation was required. The incidence of bone resorption significantly correlated with an increased skull defect area (p < 0.025). No significant correlation was found with age, sex, or anatomical location of the skull defect, number of fractured bone fragments, presence of a shunt, cause for decompressive craniectomy, method of duraplasty, or interval between the craniectomy and the cranioplasty. Reoperation to repair the resorbed autologous bone was performed 2 to 76 months after the initial procedure. CONCLUSIONS: The use of autologous bone to reconstruct skull defects in pediatric patients after decompressive craniectomy is associated with a high incidence of bone resorption. The use of autologous bone should be reevaluated in light of the high rate of reoperation in this pediatric population.

Adolescent↗
PubMed2003

Adenosine-induced modulation of excitatory amino acid transport across isolated brain arterioles.

OBJECT: Excitatory amino acid (EAA) uptake by neurons and glia acts synergistically with stereoselective transport across the blood-brain barrier (BBB) to maintain EAA homeostasis in the brain. The endogenous neuroprotectant adenosine counteracts many aspects of excitotoxicity by increasing cerebral blood flow and by producing pre- and postsynaptic actions on neurons. In the present study, the authors explored the effect of adenosine on EAA transport across the BBB. METHODS: The effects of adenosine on the permeability of the BBB and transport of aspartate and glutamate across the BBB were studied in a well-characterized isolated penetrating cerebral arteriole preparation suitable for simultaneous investigations of changes in diameter and permeability. At concentrations within the physiological to low pathophysiological range (10(-7)-10(-6) M), the net vectorial transport of [3H]L-glutamate or [3H]L-aspartate from blood to brain was significantly attenuated, whereas there was no effect of adenosine on paracellular BBB permeability to [14C]sucrose or [3H]D-aspartate. With higher concentrations of adenosine (10(-4) M and 10(-3) M) the net vectorial transport of [3H]L-glutamate and [3H]Laspartate returned toward baseline. At 10(-3) M, the permeability to [14C]sucrose was significantly altered, indicating a breakdown in the BBB. The effect of adenosine (10(-6) M) was blocked by theophylline, a blocker of the A1 and A2 receptors of adenosine. CONCLUSIONS: Adenosine-mediated modulation of glutamate and aspartate transport across the BBB is a novel physiological finding.

Adenosine↗
PubMed2002

The utility of magnetic resonance imaging in evaluating peripheral nerve disorders.

The evaluation of peripheral nerve injuries has traditionally relied primarily on information gained from the clinical history, physical examination, and electrodiagnostic testing. Taken together, all of this clinical and diagnostic information often allows one to determine the location and severity of the underlying peripheral nerve problem. However, it may not be sufficient in diagnosing a focal entrapment neuropathy superimposed upon a more generalized peripheral neuropathy; localizing a focal lesion along a long segment of nerve which may be difficult to assess accurately with electrodiagnostic studies; distinguishing early between an axonotmetic grade of injury, which can recover through axonal regeneration, and a neurotmetic grade which cannot and therefore may benefit from a surgical exploration and repair procedure; and noninvasively diagnosing and determining the surgical resectability of peripheral nerve mass lesions such as tumors. The goal of this review is to illustrate how standard and evolving magnetic resonance imaging techniques can provide additional information in dealing with some of these problems.

Humans↗
PubMed2002

Long-term safety and efficacy of continuous intrathecal baclofen.

Long-term continuous intrathecal baclofen (CITB) infusion is a treatment option used to manage otherwise intractable spasticity and is delivered via an implantable pump. The purpose of this single-center multidisciplinary review was to report on the long-term safety and efficacy of CITB in the treatment of 21 children with intractable severe spasticity of cerebral origin. Nineteen recipients had spastic quadriplegia and two had spastic diplegia. Seven recipients had level IV severity on the Gross Motor Functional Classification System and 14 had level V. Median age at implantation was 12 years (range 4 to 20). Fifteen recipients were male, 6 were female. Seventeen recipients were alive at the end of the follow-up period (31 to 78 months; mean 53, SD 4). The Ashworth scale showed a substantial decrease in spasticity in the upper and lower extremities at 6 months and at the most recent follow-up. The Gross Motor Function Measure and Pediatric Evaluation of Disability Inventory showed no functional change. Most treatment goals were at least partly achieved. Caregivers reported a reduction in use of oral medication for spasticity, and improvements in comfort, function, and ease of care. Caregiver satisfaction was high. During 80 recipient-years of pump operation, 153 treatment-associated adverse events occurred: 27 of these were device-related. There were four deaths unrelated to CITE, including one from acute pancreatitis. Our findings might assist in establishing patient selection criteria and treatment goals, improving patient follow-up, and monitoring adverse events.

Adolescent↗
PubMed2002

Delayed facial palsy after resection of vestibular schwannoma.

OBJECT: In this study the authors investigate delayed facial palsy (DFP), which is an underreported phenomenon after surgery for vestibular schwannoma (VS). The authors identified 15 (4.8%) patients from a consecutive series of 314 who underwent surgery for VS between 1988 and 2000, and in whom DFP developed. Delayed facial palsy was defined as a deterioration of facial nerve function from House-Brackmann Grades 1 or 2 more than 3 days postoperatively. METHODS: All patients underwent intraoperative neurophysiological monitoring of facial nerve function. The average latency of DFP was 10.9 days (range 4-30 days). In six patients (40%) minor deterioration (< or = two House-Brackmann grades) had occurred at a mean of 10.2 days postsurgery, whereas in nine patients (60%) moderate deterioration (> or = three House-Brackmann grades) had occurred at a mean of 11.8 days postoperatively. Five (33%) of 15 patients recovered to Grade 1 of 2 function within 6 weeks of DFP onset. Of the 15 patients with DFP, 14 had completed 1 year of follow up at the time of this study. Twelve (80%) of these 15 patients recovered to Grade 1 or 2 function within 3 months, and 13 (93%) of 14 patients recovered within 1 year. In all cases, stimulation of the seventh cranial nerve on completion of tumor resection revealed the nerve to be intact, both anatomically and functionally, to proximal and distal stimulation at 0.1 mA. A smaller tumor diameter correlated with greater recovery of facial nerve function. There was no correlation between the latency or severity of or recovery from DFP, and the patient's age or sex, the surgical approach, frequency of neurotonic seventh nerve discharges, anatomical relationship of the facial nerve to the tumor, patient's history of tobacco use, or cardiovascular disease. CONCLUSIONS: It appears that DFP is an uncommon consequence of surgery for VS. Although excellent recovery of facial nerve function to its original postoperative status nearly always occurs after DFP, the magnitude and time course of the disorder were not predictors for subsequent recovery of facial nerve function.

Adolescent↗
PubMed2002

Continuous somatosensory evoked potential monitoring during brain tumor resection. Report of four cases and review of the literature.

The neurosurgical management of intrinsic brain tumors and brain metastases mandates maximum resection with preservation of functional cortex. There have been previous reports on the use of cortical somatosensory evoked potentials (SSEPs) for localization of functional cortex prior to resection. The identification of rolandic cortex with the use of intraoperative SSEP monitoring enables the neurosurgeon to tailor the surgery to achieve a greater extent of resection while minimizing the risk of morbidity. The use of continuous SSEP monitoring during resection to provide an ongoing functional assessment of somatosensory cortex has not been reported. This powerful technique is illustrated using four case examples.

Adenomatous Polyposis Coli↗