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Biomedical subjects

Arun Paul Amar

Publications and source records attributed to Arun Paul Amar.

9 recordsLinked to original sources
PubMed2005

Percutaneous spinal interventions.

Interventional neuroradiology procedures of the spine are being performed with increasing frequency. These therapies complement and, in some cases, replace more conventional operations of the vertebral column and its contents. This article surveys the background, present application, and future horizons of several minimally invasive spinal interventions, including vertebroplasty and kyphoplasty, microcatheterization of the cervical epidural space via lumbar puncture for drug delivery, percutaneous intraspinal navigation, and percutaneous spinal fixation.

Diskectomy, Percutaneous↗
PubMed2004

Vagus nerve stimulation therapy after failed cranial surgery for intractable epilepsy: results from the vagus nerve stimulation therapy patient outcome registry.

OBJECTIVE: To determine the effectiveness of vagus nerve stimulation (VNS) therapy among patients with persistent or recurrent seizures after lobar resection, callosotomy, and other cranial operations for intractable epilepsy. METHODS: Data were obtained from the VNS therapy patient outcome registry, which was established after United States Food and Drug Administration approval of the VNS device in 1997 as a means of capturing open-label clinical data outside of protocol. The integrity of the systems for collecting and processing registry data was authenticated by an independent auditing agency. The effect of potential selection bias, however, remains uncertain. RESULTS: Two nonconsecutive cohorts were compared: patients tracked in the registry who had previously undergone cranial surgery for epilepsy (CS group, n = 921) and those who had not (non-CS group, n = 3822). For the CS group, the median reduction in seizure frequency was 42.5% after 3 months of VNS therapy, 42.9% at 6 months, 45.7% at 12 months, 52.0% at 18 months, and 50.5% at 24 months. For the non-CS group, analogous rates were 47.0%, 52.9%, 60.0%, 62.7%, and 66.7%, respectively. In the CS group, seizures were reduced by at least 50% in 55.1% of patients, at least 75% in 31.4% of patients, at least 90% in 17.3% of patients, and 100% in 5.1% of patients after 24 months of VNS therapy. Response rates were more pronounced in the non-CS group: at least 50% in 62.2% of patients, at least 75% in 43.7% of patients, at least 90% in 26.8% of patients, and 100% in 8.3% of patients. Patients in both groups experienced marked improvements in quality of life parameters. CONCLUSION: The effectiveness of VNS is maintained during prolonged stimulation, and overall seizure control continues to improve with time. Patients in whom prior cranial surgery had failed did not respond as favorably as all other patients receiving VNS therapy. Nonetheless, many of the former group improved substantially. Thus, on the basis of these open-label data, VNS therapy represents a potentially palliative treatment option for patients with refractory seizures after failed cranial surgery.

Adolescent↗
PubMed2004

Hydrocephalus in children with middle fossa arachnoid cysts.

OBJECT: The optimal management of children with middle fossa arachnoid cysts (MFACs) remains controversial. In this study the authors evaluated the relationship between two preoperative variables, hydrocephalus and nonspecific macrocephaly, in children undergoing fenestration of temporal arachnoid cysts and hydrocephalus-related shunt placement. METHODS: During a 16-year period, 40 children (30 boys and 10 girls) underwent treatment of MFACs. All but one patient experienced either worsening symptoms or progressive serial imaging-documented cyst enlargement. Hydrocephalus was present in six patients and nonspecific macrocephaly in another nine. The mean age at surgery was 66 months (range 1-201 months, median 36 months), and the mean follow-up duration was 54 months (range 6-83 months, median 39 months). All patients presenting with hydrocephalus required placement of a ventriculoperitoneal (VP) shunt as well as cyst fenestration, regardless of which procedure was performed first. Five patients with macroencephaly undergoing initial fenestration required subsequent VP shunt insertion. Complications of cerebrospinal fluid (CSF) diversion were typical. CONCLUSIONS: Patients with hydrocephalus or macrocephaly are likely to require VP shunt placement in addition to cyst fenestration. Children with nonspecific macrocephaly may harbor a latent derangement of CSF circulation.

Adolescent↗
PubMed2003

Pituitary anatomy and physiology.

The pituitary has been called the master gland of the body because of its central role in governing homeostasis, maintaining the reproductive cycle, and directing the activity of other glands. Housed in the sella turcica of the sphenoid bone at the base of the skull, it has important anatomic relations with the hypothalamus, visual pathways, cavernous sinus, carotid artery, and cranial nerves. The gland originates from two discrete parts of the developing embryo. Rathke's pouch, a dorsal evagination of the stomodeum, forms the anterior and intermediate lobes. The infundibulum, a ventral extension of the diencephalon, forms the posterior lobe. The anterior, intermediate, and posterior lobes of the pituitary gland function as three separate endocrine organs, each characterized by distinct cell populations, secretory products, and regulatory mechanisms. The anterior lobe secretes thyroid stimulating hormone, corticotropin, luteinizing hormone, follicle stimulating hormone, growth hormone, and prolactin. It is regulated by the hypothalamus via the portal vascular system. The posterior lobe releases oxytocin and vasopressin from axon terminals that originate in cell bodies located in the hypothalamus. The intermediate lobe is rudimentary in human beings but produces several hormones whose physiologic significance is only now being established.

Adrenocorticotropic Hormone↗
PubMed2003

Vagus nerve stimulation therapy for patients with persistent seizures after epilepsy surgery.

BACKGROUND: This study reports the effectiveness of vagus nerve stimulation (VNS) among patients who failed cranial surgery for intractable epilepsy. METHODS: Data were obtained from the Cyberonics VNS therapy patient outcome registry. The integrity of the systems for collecting and processing registry data was authenticated by an independent auditing agency. RESULTS: Two nonconsecutive cohorts were compared: patients who had had prior cranial surgery (CS group, n = 921) and those who had not (non-CS group, n = 3,822). For the CS group, the median reduction in seizure frequency was 42.5% after 3 months of VNS therapy, 42.9% at 6 months, 45.7% at 12 months, 52.0% at 18 months and 50.5% at 24 months. For the non-CS group, analogous rates were 47.0, 52.9, 60.0, 62.7 and 66.7%, respectively. CONCLUSION: The effectiveness of VNS is maintained during prolonged stimulation. Patients who failed prior cranial surgery did not respond quite as favorably as all other patients receiving VNS therapy.

Electric Stimulation Therapy↗
PubMed2003

Endovascular restorative neurosurgery: a novel concept for molecular and cellular therapy of the nervous system.

The amalgam of molecular biology and neurosurgery offers immense promise for neurorestoration and the management of neurodegenerative deficiencies, developmental disorders, neoplasms, stroke, and trauma. This article summarizes present strategies for and impediments to gene therapy and stem cell therapy of the central nervous system and advances the concept of a potential new approach, namely endovascular restorative neurosurgery. The objectives of gene transfer to the central nervous system are efficient transfection of host cells, selective sustained expression of the transgene, and lack of toxicity or immune excitation. The requisite elements of this process are the identification of candidate diseases, the construction of vehicles for gene transfer, regulated expression, and physical delivery. In the selection of target disorders, the underlying genetic events to be overcome, as well as their spatial and temporal distributions, must be considered. These factors determine the requirements for the physical dispersal of the transgene, the duration of transgene expression, and the quantity of transgene product needed to abrogate the disease phenotype. Vehicles for conveying the transgene to the central nervous system include viral vectors (retroviruses, lentiviruses, adenoviruses, adeno-associated viruses, and herpes simplex virus), liposomes, and genetically engineered cells, including neural stem cells. Delivery of the transgene into the brain presents several challenges, including limited and potentially risky access through the cranium, sensitivity to volumetric changes, restricted diffusion, and the blood-brain barrier. Genetic or cellular therapeutic agents may be injected directly into the brain parenchyma (via stereotaxy or craniotomy), into the cerebrospinal fluid (in the ventricles or cisterns), or into the bloodstream (intravenously or intra-arterially). The advantages of the endovascular route include the potential for widespread distribution, the ability to deliver large volumes, limited perturbation of neural tissue, and the feasibility of repeated administration.

Animals↗
PubMed2003

Use of a screw-syringe injector for cement delivery during kyphoplasty: technical report.

OBJECTIVE: Percutaneous kyphoplasty is postulated to have several advantages over percutaneous vertebroplasty for the treatment of vertebral compression fractures and is gaining increased popularity. However, cement delivery with the KyphX kit (Kyphon, Inc., Santa Clara, CA), the only commercially available device for percutaneous kyphoplasty, is relatively problematic. This kit uses a series of "bone filler device" (BFD) tubes. Each BFD must be loaded manually with cement, which is then injected into the kyphoplasty cavity by manually depressing an inner stylet. The high profile of the BFD cannulas and their stylets requires frequent repositioning of the image intensifier tube and table. Because each accommodates only a small volume, the BFDs must be exchanged frequently. This delivery method also places the operator's hands directly in the field of radiation. We sought to overcome these limitations. METHODS: Dissatisfied with the shortcomings of the BFDs, we substituted the EZflow screw-syringe injector (Parallax Medical, Mountain View, CA) we use to deliver cement during conventional percutaneous vertebroplasty. This amalgam of the KyphX kit and the screw-syringe injector has been used for kyphoplasty treatment of 26 thoracolumbar compression fractures in 17 patients. RESULTS: The screw-syringe injector allows controlled volumetric delivery of large boluses of high-viscosity cement without having to refill the reservoir. It minimizes radiation exposure and does not require repositioning of the x-ray tubes. It may theoretically allow decompression should cement extrusion occur. Also, it delivers cement to the interstices of bony trabeculae outside the kyphoplasty cavity, thus combining the mechanical benefits of percutaneous kyphoplasty and percutaneous vertebroplasty. CONCLUSION: The use of a screw-syringe injector has several merits over the customary means of cement delivery during kyphoplasty.

Bone Cements↗
PubMed2002

Covered stent-graft repair of the brachiocephalic arteries: technical note.

OBJECTIVE: The use of a covered stent-graft to repair disruptions of the cervical carotid and vertebral arteries is described. This device maintains vessel patency while effectively excluding pseudoaneurysms, arteriovenous fistulae, and other breaches in the integrity of the arterial wall. METHODS: Patient 1 bled from a large rent in the proximal common carotid artery as a result of tumor invasion. Patient 2 developed a vertebral arteriovenous fistula after a stab injury to the neck. Patient 3 developed cerebral infarction and an enlarging pseudoaneurysm of the internal carotid artery, also after a stab wound to the neck. RESULTS: All three patients were treated with the Wallgraft endoprosthesis (Boston Scientific, Watertown, MA). In each case, the vessel wall defect was repaired while antegrade flow through the artery was preserved or restored. No neurological complications occurred as a result of stent-graft deployment. CONCLUSION: Covered stent-grafts offer an alternative to endovascular occlusion of the parent vessel, thereby expanding the therapeutic options for patients with extracranial cerebrovascular disease. These three cases highlight the usefulness and versatility of these devices for endoluminal reconstruction of the brachiocephalic vasculature.

Adult↗