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P W Carmel

Publications and source records attributed to P W Carmel.

At least 19 recordsLinked to original sources
PubMed2003

Cranial surgery and navigation with a compact intraoperative MRI system.

Experience with a compact unit for intraoperative magnetic resonance imaging (iMRI) and integrated surgical navigation is presented. The system, commercially known as the PoleStar N-10 (Odin Medical Technologies, Yokne'am, Israel) includes a 0.12 Tesla permanent magnet that docks under a regular OR table. A passive infrared-based optical navigation system is included and the device can be controlled by the operating neurosurgeon and staff. We have operated on 93 patients using the PoleStar N-10. Diagnoses included glioma in 27, pituitary adenoma in 19, meningioma in 15, and others in 40. Lesions were removed from the skull base in 35 patients of whom 8 had posterior fossa masses. Surgery was affected by imaging in 51% of operations. Additional lesion, not otherwise apparent, was removed in 21; in 14 other patients unnecessary dissection was avoided when the new image confirmed that the surgical goals had been achieved. Additional time incurred with use of the PoleStar diminished with increasing experience. Testing of the navigation tool confirmed its accuracy to be comparable to other "frameless stereotactic" devices, on the order of 2 mm; likewise accuracy was increased by using T1 weighted imaging with thin slices. The introduction of new, faster imaging sequences and targeting tools has helped to make the PoleStar N-10 a routine tool for intracranial surgical navigation, with the added benefit of updated imaging during the procedure.

Adenoma↗
PubMed2001

Intraoperative MRI and adjuvant radiosurgery.

INTRODUCTION: For many patients with brain tumors, the ideal management strategy may be a planned subtotal resection followed by stereotactic radiosurgery (SRS). However, intraoperative visual inspection may be an inadequate measure of the amount of residual lesion. Intraoperative MRI (IMRI) may help to ensure that the goals of surgery have been achieved and that the best possible target for SRS remains. PATIENTS AND METHODS: We have operated on 68 patients using the PoleStar N-10 IMRI system (Odin Medical Technologies, Yokne'am, Israel). Benign extraaxial lesions were present in 34 patients. In 12 patients subtotal resection and adjuvant SRS were planned. Diagnoses included 5 pituitary adenomas, 4 meningiomas, 2 vestibular schwannomas, and 1 trigeminal schwannoma. Tumor resection was performed until critical structures (e.g. superior sagittal sinus) were being approached and IMRI demonstrated that the lesion was as small as possible. RESULTS: In 1 patient a surgical resection was completed, while in 11 others the plan for subtotal resection was carried out. One patient with an extensive meningioma was treated with fractionated 3-dimensional conformal fractionated radiation therapy, as her tumor remained too large for SRS. In the remaining 10 patients an ideally small target remained for SRS; 3 patients have been treated so far. CONCLUSIONS: Adjuvant SRS after subtotal tumor resection is an excellent management strategy for many patients with intracranial tumors. IMRI can ensure that the surgical goals have been reached. Future comparison of target volumes, integral volume doses, and patient outcomes are planned.

Adult↗
PubMed2001

Cranial surgery navigation aided by a compact intraoperative magnetic resonance imager.

OBJECT: In this article the authors report on a novel, compact device for magnetic resonance (MR) imaging that has been developed for use in a standard neurosurgical operating room. METHODS: The device includes a permanent magnet with a field strength of 0.12 tesla. The poles of the magnet are vertically aligned, with a gap of 25 cm. When not in use the magnet is stored in a shielded cage in a corner of the operating room; it is easily moved into position and attaches to a regular operating table. The magnet is raised for imaging when needed and may be lowered to allow surgery to proceed unencumbered. Surgical navigation with optical and/or magnetic probes is incorporated into the system. Twenty-five patients have undergone removal of intracranial lesions with the aid of this device. Operations included craniotomy for tumor or other lesion in 18 patients and transsphenoidal resection of tumor in seven. The number of scans ranged from two to five per surgery (average 3.4); image quality was excellent in 45%, adequate in 43%, and poor in 12%. In four patients MR imaging revealed additional tumor that was then resected; in five others visual examination of the operative field was inconclusive but complete tumor removal was confirmed on MR imaging. In 21 patients early postoperative diagnostic MR studies corroborated the findings on the final intraoperative MR image. Using a water-covered phantom, the accuracy of the navigational tools was assessed; 120 data points were measured. The accuracy of the magnetic probe averaged 1.3 mm and 2.1 mm in the coronal and axial planes, respectively; the optical probe accuracy was 2.1 mm and 1.8 mm in those planes. CONCLUSIONS: This device provides high-quality intraoperative imaging and accurate surgical navigation with minimal disruption in a standard neurosurgical operating room.

Adult↗
PubMed1999

Incidence and management of subdural hematoma/hygroma with variable- and fixed-pressure differential valves: a randomized, controlled study of programmable compared with conventional valves.

Shunt systems with differential pressure valves are prone to the complications of overdrainage. A programmable valve permits adjustment of the opening pressure of the valve. In this paper the authors report the incidence of subdural fluid collections in a randomized trial of programmable compared with conventional valves, and they describe methodologies used in management of this complication. A multiinstitutional, prospective, randomized trial of the Codman Hakim programmable valve and conventional fixed-pressure valves was undertaken. Two classes were defined: "new" and "replacement" valves. Randomization of the type of valve in each group was performed at each study site. Clinical and radiological studies were required at fixed intervals over a 104-week period. All complications were reported. The experimental valves were required to be reprogrammed after magnetic resonance imaging studies, but all other decisions regarding pressure setting were left to each investigator. Three hundred seventy-seven patients were randomized; 194 were treated with a programmable valve and 183 with a fixed-pressure valve. The two groups were statistically similar in demographic composition, as were the "new" and "replacement" categories. The investigators made 540 valve pressure changes (five per patient; range one-41 changes). More than half of the reprogramming adjustments were made in the first 3 months postplacement; 70% were made within 6 months. More than half of all reprogramming adjustments were required in a group of 30 patients. Four treatment modalities were observed: 1) 30% of the fluid collections resolved spontaneously (25% in the patients with programmable valves and 36.3% in those with conventional valves) and were largely found to be hygromas in infants and children; 2) four subdural fluid collections were unresolved and under observation; 3) the subdural hematoma was drained and the shunt removed (in 8.3% of patients with the programmable valve and 36.3% of those with the control valve); 4) the pressure of programmable valve was raised in 58% of patients (seven of 12), and this increase in opening pressure was a feature used by investigators to affect treatment. There was no significant difference in the incidence of subdural fluid collections between the programmable and fixed-pressure valve treatment groups. The programmable feature provided a considerable advantage in treatment when subdural collections occurred.

Journal Article↗
PubMed1999

The relationship of imaging techniques to the accuracy of frameless stereotaxy.

OBJECTIVE: We analyzed the accuracy of a frameless stereotactic system using computed tomographic (CT) and magnetic resonance imaging (MRI) scans of different slice thickness and T(1) versus T(2) weighting of MRI. METHODS: An open skull with graphite pegs fixed to its base was used for all scans. CT scans were done with slice thicknesses of 1, 2 and 3 mm. MRI-visible markers were placed on top of pegs for T(1)-weighted and T(2)-weighted MRI scans, which were acquired at thicknesses of 1.5, 3 and 5 mm. For each scan, 3 separate registrations of a probe were performed; the distance between the actual probe location and that displayed on the registered image was noted. Each measurements was repeated 3 times for each registration. RESULTS: Greatest accuracy was achieved with 3-mm-slice CT scans; this was not improved by using thinner slices. T(1)-weighted 1.5-mm MRI scans were 23% less accurate and T(2)-weighted 3-mm scans 37% less accurate. CONCLUSIONS: Frameless stereotaxy should be done using CT scans when the greatest possible accuracy is desired. There appears to be no advantage to using slice thicknesses less than 3 mm. For most craniotomy applications, T(1)-weighted MRI using 3-mm slices provides sufficient accuracy. Lesions imaged only on T(2)-weighted MRI also can be approached with adequate precision using 3-mm scans.

Cephalometry↗
PubMed1999

Functional magnetic resonance image-guided surgery of tumors in or near the primary visual cortex.

OBJECTIVE: To assess the accuracy of functional magnetic resonance imaging (fMRI) of the primary visual cortex in patients undergoing surgery for tumors in the occipital lobe. METHODS: Two patients with nondominant occipital lobe tumors were studied, one with a solitary lung metastasis and another with radiation necrosis after radiosurgery for a low-grade astrocytoma. At surgery, visual evoked potentials (VEPs) were stimulated using Light-emitting-diode goggles and recorded using cortical grids placed immediately after brain exposure. The location of the peak VEP was compared to that predicted by the registered functional scan. RESULTS: In each case, the epicenter of visual activation as represented on the registered fMRI corresponded to the site of peak VEP recording. Prediction error for the visual cortex, measured in patient 1, was 1.0 mm. Visual confirmation showed the registration in the second patient to be accurate as well. CONCLUSION: As previously demonstrated for sensorimotor fMRI, visual fMRI accurately predicts the location of the primary visual cortex. Additional confirmation is expected with more clinical experience.

Adult↗
PubMed1998

Psychopharmacologic treatment of acquired attention disorders in children with brain injury.

This investigation examined the efficacy of psychostimulant therapy in alleviating neurobehavioral dysfunction attendant to pediatric brain injury. The most commonly reported neurobehavioral sequelae associated with head injury in the pediatric population involve deficits along the attentional matrix. This is also the most common objectively documented neurobehavioral finding among children as well as adults. There are several investigations in the adult literature which have employed the use of psychostimulants in treating both psychiatric and neuropsychological residua associated with head injury. Overall, the results of these studies are equivocal, but suggest a beneficial impact on general functioning. The present prospective investigation utilized a double-blind, placebo-controlled, cross-over experimental design to examine the efficacy of methylphenidate in treating children with acquired attentional disorders secondary to brain injury. A cohort of 14 children with varying degrees of head injury were recruited for participation. As expected, differences between drug and placebo conditions uniformly achieved statistical significance. Additionally, there were no differences in performance between baseline and placebo conditions on neurobehavioral tasks of attention and concentration. Current findings suggest that methylphenidate (and probably other psychostimulants such as Cylert, Adderal, Wellbutrin and dextroamphetamine sulfate) is an extremely effective agent in treating attentional disorders secondary to brain injury in children.

Adolescent↗
PubMed1998

Functional image-guided surgery of intracranial tumors located in or near the sensorimotor cortex.

OBJECT: The purpose of this study was to evaluate the efficacy of noninvasive preoperative functional imaging data used in an interactive fashion in the operating room. The authors describe a method of registering preoperative functional magnetic resonance (fMR) imaging localization of sensorimotor cortex with a frameless stereotactic surgical navigation device. METHODS: The day before surgery, patients underwent blood oxygen level-dependent fMR imaging while performing a finger-tapping motor paradigm. Immediately afterward an anatomical stereotactic MR image was acquired. Raw fMR imaging data were analyzed offline at a separate workstation, and the resulting functional maps were registered to a high-resolution anatomical scan. The fused functional-anatomical images were then downloaded onto a surgical navigation computer via an ethernet connection. At surgery, the brain was exposed in the standard fashion, and the sensorimotor cortex was identified by direct cortical stimulation, the use of somatosensory evoked potentials, or both. This localization was then compared with that predicted by the registered fMR study. Thirteen procedures were performed in 12 patients. The mean registration error was 2.2 mm. The predicted location of motor and/or sensory cortex matched that found on intraoperative mapping in all 12 patients tested. Maximal tumor resection was accomplished in each case and no new permanent neurological deficits resulted. CONCLUSIONS: Compared with conventional brain mapping techniques, fMR image-guided surgery may allow for smaller brain exposures, localization of the language cortex with the patient under general anesthesia, and the mapping of multiple functional sites. The scanning equipment used in this method may be more readily available than for other functional imaging techniques such as positron emission tomography or magnetoencephalography.

Adult↗
PubMed1997

Giant posterior fossa cystic craniopharyngiomas presenting with hearing loss. Report of three cases and review of the literature.

BACKGROUND: Autopsy studies and recent reviews report that 4% of craniopharyngiomas have posterior fossa extension at initial operation, and 12% subsequently develop this extension during their course. However, only two patients in the literature have been shown to present with deafness, which preceded the more typical suprasellar signs and symptoms of increased intracranial pressure, endocrine disturbance, altered mentation, and visual deterioration. METHODS: The authors report three cases of giant cystic posterior fossa craniopharyngioma initially presenting in childhood with either unilateral or bilateral deafness. These cases are presented, the literature on posterior fossa craniopharyngioma is reviewed, and staged operative management is discussed. RESULTS: Despite being rarely reported, 10% to 20% of giant cystic craniopharyngiomas with posterior fossa extension at presentation may have unilateral or bilateral deafness as their first symptom. Deafness as a presenting symptom is much less common in patients presenting with recurrent tumors in this location than with primary tumors. Pterional or bifrontal craniotomy is appropriate for management of the parasellar component and should be undertaken first when visual symptoms are present. Suboccipital craniectomy is appropriate for management of the posterior fossa component and should be undertaken first when brain stem compressive symptoms make it necessary. Skull-base techniques may have value in certain settings, but patient's morbidity when using these techniques must be carefully considered. CONCLUSIONS: Our results indicate that staged operations with the goal of achieving gross total resection can yield excellent results. Adjuvant radiation is indicated for those with residual tumor seen on magnetic resonance imaging (MRI), but in young children without residual tumors by MRI, we prefer to follow carefully with serial scans. Since the loss of hearing in children can compromise language development, we suggest referral of these children to a specialist in language rehabilitation.

Child↗
PubMed1997

Functional MRI-guided surgery of intracranial tumors.

We describe a technique of registering functional magnetic resonance image (fMRI) data sets with the anatomical images used for intraoperative navigation. Three patients with supratentorial tumors were studied, 2 with astrocytomas and 1 with a meningioma. The day before surgery, a functional blood-oxygen-level-dependent MR scan was done. During the same imaging session, an anatomic stereotactic MR scan was performed. The raw data were reconstructed off line on a workstation, and the fMR maps were then registered to the anatomic studies using image header information. Fused images were then transferred to the navigational workstation over an Ethernet connection. At surgery, brain exposure was performed in a standard manner. In each case, the registered scans accurately localized the motor and/or sensory cortex. No new permanent neurological deficits resulted from surgery. The potential advantages of fMRI-guided surgery include: (1) smaller brain exposures; (2) localization of language cortex under general anesthesia; (3) mapping of multiple functional sites, with decreased time and increased case of surgery.

Adult↗
PubMed1996

Recurrent cerebral arteriovenous malformations after negative postoperative angiograms.

Angiography has been considered to be the gold standard to judge the success of treatment for cerebral arteriovenous malformations (AVMs). Patients without residual nidus or early draining veins on postoperative angiograms are considered cured, with the risk of hemorrhage eliminated. A series of five patients with recurrent AVMs after negative postoperative angiography is described. All patients had hemispheric AVMs, presented initially with hemorrhage, and were between 5 and 13 years of age. Recurrence was noted 1 to 9 years later (at 12-16 years of age); after a hemorrhage in three patients, seizures in one, and on follow-up magnetic resonance imaging in one. Four patients underwent angiography that showed recurrence of the AVM at or adjacent to the original site. Three years postsurgery, the fifth patient died from a large intracerebral and intraventricular hemorrhage originating in the previous location of the AVM; however, the patient did not undergo angiography at the time of recurrence. The initial negative angiograms obtained postoperatively in these patients may be explained by postoperative spasm or thrombosis of a small residual malformation. However, in the authors' cumulative experience with 808 patients who have undergone complete surgical removal of AVMs (of whom 667 were older than 18 years of age), no case of recurrent AVM has been observed in an adult. Therefore, actual regrowth of an AVM may occur in children and could be a consequence of their relatively immature cerebral vasculature and may involve active angiogenesis mediated by humoral factors. The present findings argue against the assumption that AVMs are strictly congenital lesions resulting from failure of capillary formation during early embryogenesis. It is concluded that delayed imaging studies should be considered in children at least 1 year after their initial negative postoperative arteriogram to exclude a recurrent AVM.

Adolescent↗
PubMed1995

Internal brain herniation in a patient with Apert's syndrome.

Patients with Apert's syndrome typically exhibit craniosynostosis, exorbitism, midface hypoplasia, and symmetric syndactyly. There have also been occasional descriptions of the variable dysmorphology of the inner surface of the calvarium. We present a patient with Apert's syndrome who had an intracranial herniation of a portion of the frontal lobe through a ridge of ossified dura. The ridge and the gliotic cortical tissue were removed when the patient underwent repair of the hypertelorism at age six. Bone grafts for this repair were fashioned in part from the resected ridge. We believe this finding may be the result of a small dural tear that occurred during prior surgery.

Acrocephalosyndactylia↗
PubMed1993

Monitoring of intraoperative motor-evoked potentials under conditions of controlled neuromuscular blockade.

Motor-evoked potentials were recorded after electrical spinal cord stimulation in 19 patients undergoing neurosurgical or orthopedic procedures. Anesthesia was maintained with nitrous oxide, opioids, and inhaled anesthetics. Vecuronium was infused sufficient to eliminate 90% of twitch tension. The spinal cord was stimulated using either epidural or subarachnoid electrodes. Compound muscle action potentials were recorded from quadriceps and tibialis anterior muscles. Well-formed, stable motor-evoked potentials were recorded in all but one patient, in whom a preexisting myelopathy was felt to preclude recording. Intraoperative deterioration of motor-evoked potentials occurred in one patient who had a postoperative neurologic deficit. This study demonstrates the feasibility and utility of intraoperative motor tract monitoring using direct spinal cord stimulation. Controlled neuromuscular blockade permits recording of compound muscle action potentials while eliminating patient motor activity that could interfere with surgery.

Action Potentials↗
PubMed1991

Myelination of the rat retina by transplantation of oligodendrocytes into 4-day-old hosts.

Oligodendrocyte transplantation into the retina enables us to investigate the early events in myelin formation in a new in vivo system. The axons of rat retinal ganglion cells are unmyelinated in the eye but should express a myelination initiation signal since they acquire myelin posterior to the globe. The lamina cribrosa may block the migration of oligodendrocytes from the optic nerve into the retina. Animals that lack a lamina cribosa such as the rabbit have myelinated retinas. We have bypassed the lamina cribrosa by using transplantation techniques and inserted freshly isolated syngeneic 3-week-old rat oligodendrocytes into the unmyelinated 4-day-old rat retina during the period of active optic nerve myelination. The animals are sacrificed at 1-week intervals for 8 weeks. The retinas are examined immunocytochemically for myelin with an antibody to myelin basic protein (MBP). MBP-positive cells are seen extending processes at 1 and 2 weeks. Three and four week retinas show the formation of thicker and longer myelin sheaths oriented along the same radial path as the retinal ganglion axons with maximal MBP staining intensity seen by 5 weeks. Transplanted retinas are negative when stained for P0, a Schwann cell antigen, ruling out Schwann cell myelination of our retinas. We have shown that rat cerebral oligodendrocytes survive, mature, and express a myelin-specific protein in the retinal environment in a pattern consistent with myelination of ganglion cell axons. Retinal transplantation provides a new in vivo model to study oligodendrocyte development and axonal-glial interactions, free from the difficulties inherent in culture systems.

Animals↗
PubMed1990

Congenital intradural pathology.

Congenital spinal malformations discussed include myelomeningocele, tethered cord, diastematomyelia, diplomyelia, neuroenteric cysts, anterior meningocele, and Chiari malformations. The authors discuss the clinical presentation, radiologic evaluation, and treatment of these congenital anomalies.

Diagnostic Imaging↗