Search PubMed⌕ Search

Biomedical subjects

C R Jack

Publications and source records attributed to C R Jack.

At least 109 records · Page 6Linked to original sources
PubMed1992

Identification of the epileptic focus: magnetic resonance imaging.

Magnetic resonance imaging (MRI) is the most sensitive and specific structural imaging technique available to demonstrate focal epileptogenic lesions in patients with intractable partial epilepsy. MRI may be useful in the selection of candidates for surgical treatment of epilepsy. The studies may also assist in the implantation of depth electrodes and in the stereotactic resection of epileptogenic lesions. More recent applications of this neuroimaging modality in the surgical treatment of epilepsy include pre-operative hippocampal formation of volume measurements and postoperative quantitative determinations of cortical resections.

Brain↗
PubMed1991

Early childhood diagnosis of acoustic neuromas in presymptomatic individuals at risk for neurofibromatosis 2.

We report on a family in which individuals at risk for NF 2 were investigated with the use of gadolinium-enhanced MRI. This technique has allowed the diagnosis of small (less than 8 mm) acoustic neuromas in two asymptomatic children (age 7 and 11), one of whom had normal audiometric and brainstem-evoked response testing. To our knowledge these are the youngest asymptomatic patients in whom the diagnosis of NF 2 has been demonstrated. It is possible that acoustic neuromas develop at an early age more commonly than recognized previously. The early diagnosis of acoustic neuromas with the use of gadolinium-enhanced MRI may lead to better outcome following surgery. This technique will provide the opportunity to better determine the natural course of this disease.

Adult↗
PubMed1991

Magnetic resonance imaging-based volume studies in temporal lobe epilepsy: pathological correlations.

We performed a prospective study correlating magnetic resonance imaging volume measurements of the hippocampal formation with histopathology in 24 patients with intractable partial epilepsy who subsequently underwent an anterior temporal lobectomy for their seizure disorder. Patients with mass lesions verified pathologically were excluded from this study. In 71% of patients, quantitative hippocampal formation atrophy correctly lateralized the temporal lobe of seizure origin; in 29%, the volume study was indeterminant. The severity of the pathological alterations in the hippocampus correlated with the hippocampal formation volume determination. Mesial temporal sclerosis was identified in the surgically excised temporal lobe in 15 patients. The magnetic resonance imaging volume studies indicated hippocampal atrophy in the temporal lobe resected in 14 of the 15 patients. Magnetic resonance imaging-based volume measurements of the hippocampal formation increase the diagnostic yield of magnetic resonance imaging scanning in patients with intractable partial epilepsy related to mesial temporal sclerosis.

Adolescent↗
PubMed1991

Sequential magnetic resonance imaging following stereotactic radiofrequency ventralis lateralis thalamotomy.

Serial postoperative magnetic resonance (MR) studies were obtained in 21 patients who underwent somatotopically placed stereotactic radiofrequency (rf) ventralis lateralis thalamotomy for the control of movement disorders. The MR studies were reviewed to determine the MR characteristics of early-phase (less than or equal to 7 days) and late-phase (8 days to 5 months) lesions. Surgery was performed for the control of parkinsonian tremor (14 cases), intention tremor (six cases), and essential tremor (one case). Single rf lesions were made with an electrode (1.6 mm in diameter, 3 mm in tip length) heated to 78 degrees C for 60 seconds. On MR images of the lesions, three distinct concentric zones were identified, described as follows (from the center outward). Zone 1 gives increased signal on long-relaxation time (TR) (T2-weighted) MR images in early- and late-phase lesions and decreased signal on short-TR (T1-weighted) MR images in early-phase lesions only. Zone 2 gives decreased signal on long-TR (T2-weighted) images in early- and late-phase lesions; it gives isointense signal on short-TR (T1-weighted) images in early-phase lesions only. Zone 3 gives increased signal on long-TR (T2-weighted) images in early-phase lesions only and decreased signal on short-TR (T1-weighted) MR images in early-phase lesions only. It is considered that in early-phase lesions, Zone 2, with a mean diameter of 7.3 mm on axial long-TR (T2-weighted) imaging, represents an area of hemorrhagic coagulation necrosis. In late-phase lesions, Zone 2, with a mean diameter of 5.0 mm on axial long-TR (T2-weighted) imaging, represents hemosiderin deposition. Zone 3 likely represents edema, and this zone disappears between the early and late periods. From regression analysis, lesion size began to stabilize at approximately 7 months with a mature lesion diameter of 3.3 mm. Long-term follow-up monitoring (median 16 months) showed good tremor control. Based on clinical and radiological findings, the authors conclude that forms of hemoglobin are suitable markers to assess the size of rf lesions. Serial MR imaging provides a noninvasive means of studying the evolution of rf thalamotomy lesions.

Humans↗
PubMed1990

Temporal lobe seizures: lateralization with MR volume measurements of the hippocampal formation.

A retrospective magnetic resonance (MR) imaging study was performed in 41 right-handed patients with presumed mesial sclerosis who underwent surgery for medically intractable, complex partial seizures of temporal lobe origin. The ability of each of five different MR imaging-based tests to lateralize the seizure disorder was determined. In order of decreasing usefulness the tests were (a) hippocampal formation (HF) volume measurements, (b) visual grading of MR images for unilateral HF atrophy, (c) anterior temporal lobe (ATL) volume measurements, (d) visual grading of MR images for unilateral ATL atrophy, and (e) evidence of unilateral medial temporal lobe signal intensity abnormalities on long repetition time MR images. A right-side minus left-side volume (designated DHF) was obtained to quantify unilateral HF atrophy with a single number. Patients with right-sided seizures had a median DHF of -0.4 cm3, while those with left-sided seizures had a median DHF of 0.8 cm3, consistent with atrophy of the HF ipsilateral to the seizure disorder. Conservative volumetric threshold values (-0.2 cm3 and 0.6 cm3), separating individual DHF measurements into right-side abnormal, indeterminate, and left-side abnormal, allowed DHF measurements to be 76% sensitive and 100% specific for correct seizure lateralization.

Adult↗
PubMed1990

MR imaging-based volume measurements of the hippocampal formation and anterior temporal lobe: validation studies.

An experiment was designed to compare the accuracy and reproducibility of three different techniques for in vivo magnetic resonance (MR) imaging-based volume measurements of brain structures. These techniques were tracing, thresholding, and random marking. Anterior temporal lobe (ATL) and hippocampal formation (HF) volumes in 10 volunteers were measured from MR images, as were four cylinders of known volume. The upper limit of accuracy of in vivo volume measurements is estimated to be within 0.1 cm3 of true volume for the HF and 0.9 cm3 for the ATL with a combined tracing-thresholding technique. Intra- and interobserver variations were estimated from the pooled standard deviations of HF and ATL measurements. With the combined tracing-thresholding technique, the coefficient of variation for HF measurement was 1.9%; for the ATL measurement, it was 0.7%. The results indicate that MR-based volume measurements of these brain structures can be made with high precision and reproducibility.

Hippocampus↗
PubMed1990

EEG scalp electrode projection onto three-dimensional surface rendered images of the brain.

A technique is described for generating magnetic resonance-based, surface rendered images of the brain with electroencephalographic (EEG) scalp electrode positions projected onto the cortical surface. This technique (EEG electrode projection) was used in 10 patients who subsequently underwent surgery for medically intractable frontal lobe epilepsy. In most cases of intractable epilepsy, successful surgery entails the resection of electrophysiologically abnormal cortical tissue rather than an identifiable mass lesion. EEG electrode projection is a unique and useful surgical tool because it provides images that spatially correlate the surface anatomy of the brain and the electrophysiologic abnormality recorded at the scalp. Excellent correlation was found between cortical topography delineated by the surface rendered images and cortical anatomy at surgery. Agreement between EEG electrode projection and electrocorticography as to the location of the electrophysiologic abnormality increases confidence that appropriate cortical areas have been identified for resection. The technique provides new and unique insight into important anatomic-electrophysiologic relationships and aids in formulation of surgical strategy.

Adult↗
PubMed1990

MR angiography with oblique gradient-recalled echo technique.

Magnetic resonance (MR) angiography with use of an oblique gradient-recalled echo sequence is discussed. The technique was developed for the efficient acquisition of angiographic data when the desired projection direction is already known. The raw data set is acquired directly at the projection angle; thus, a high-resolution projection is created, despite a decrease in the number of phase-encoding views acquired per axial image. Excessive reduction in the number of views acquired causes a loss of contrast in the projection images rather than a loss of resolution. High-resolution, high-contrast MR projection angiograms can be obtained in 2 1/2 minutes, with 50 3-mm sections and 48 phase encodings per section, a repetition time of 50 msec, an echo time of 15 msec, and a flip angle of 45 degrees. This represents one-fifth the time required for a conventional angiographic image. Venous blood is successfully saturated when the saturation band is placed at a fixed distance from the current imaging section. The method is demonstrated in the imaging of the carotid bifurcation in healthy volunteers and of a patient who had undergone carotid endarterectomy.

Carotid Arteries↗
PubMed1989

Selective posterior cerebral artery injection of amytal: new method of preoperative memory testing.

The carotid Amytal test (Wada test) was introduced, in 1948 by Wada, to localize speech function before temporal lobectomy in patients with medically refractory epilepsy, and it remains the standard for that purpose. The same test has also been used since 1962 to evaluate memory function; however, the adequacy of the test in this application has been viewed with increasing skepticism in recent years. Therefore, we developed an alternative to the Wada test. It consists of selective injection of Amytal into the posterior cerebral artery (PCA). This PCA Amytal test is designed to test only memory function (not language). We present several anatomic and functional reasons why this approach should be superior to the Wada test for this purpose. We also present preliminary data in support of this hypothesis. To date, we have had successful results of the PCA Amytal test in 38 of 45 patients (84%), and one major complication has occurred (2%).

Adolescent↗
PubMed1989

The management of intraosseous arteriovenous malformations in the head and neck area.

It is necessary that the treatment of arteriovenous malformations in general be undertaken by a team that consists of a radiologist who is experienced in angiography and embolization and a plastic surgeon. The latter should be well versed in angiographic techniques and should be able to comprehend the dynamics of these malformations. In this report, three patients with high-flow, high-shunt arteriovenous intraosseous malformations of the head are presented. Two of these presented as emergencies with almost uncontrollable bleeding and were initially treated with embolization and then mandibular resection and reconstruction within the first 48 hours. In one patient, a further reconstructive procedure using free vascularized tissue was carried out. A third patient with involvement of the maxilla, again presenting with bleeding, was treated with embolization and, because of the deformity that would be created by resection, was simply observed. However, this patient is to be reassessed in the future and may well come to maxillectomy. It is emphasized that the treatment of these patients requires careful assessment, embolization, and resection as indicated after discussion between radiologist and surgeon.

Adolescent↗
PubMed1989

Anterior temporal lobes and hippocampal formations: normative volumetric measurements from MR images in young adults.

Volumes of the right and left anterior temporal lobes and hippocampal formations were measured from magnetic resonance images in 52 healthy volunteers, aged 20-40 years. Subjects were selected by age, sex, and handedness to evaluate possible effect of these variables. Data were normalized for variation in total intracranial volume between individuals. Right-left asymmetry in the volumes of the anterior temporal lobes and hippocampal formations was a normal finding. The anterior temporal lobe of the non-dominant (right) hemisphere was larger than the left by a small (mean right-left difference, 2.3 cm3) but statistically significant amount (P less than .005) in right-handed subjects. No significant effect of age or sex was seen in normalized right or left anterior temporal lobe volume. The right hippocampal formation was larger than the left for all subjects by a small (mean right-left difference, 0.3 cm3) but statistically significant amount (P less than .001). No effect of age, sex, or handedness was seen in normalized hippocampal formation volumes.

Adult↗
PubMed1989

Gadolinium-DTPA-enhanced magnetic resonance imaging in intractable partial epilepsy.

We performed magnetic resonance imaging (MRI), before and after the administration of gadolinium-DTPA (Gd-DTPA), in 23 patients with medically refractory partial epilepsy who subsequently had surgical treatment for their seizure disorder. In most patients, 61%, unenhanced and enhanced MRI studies were negative. In 26% the unenhanced image was positive, and the abnormality enhanced with Gd-DTPA. In 13% the unenhanced MR image was positive, but the abnormality did not enhance with Gd-DTPA. Gd-DTPA does not appear to increase the diagnostic yield of MRI in the presurgical evaluation of patients with partial epilepsy if the unenhanced MRIs are normal.

Adolescent↗
PubMed1988

Central nervous system lymphoma: histologic types and CT appearance.

The distribution of histologic types of lymphoma according to the proposed working formulation was determined for 55 patients with primary central nervous system (CNS) non-Hodgkin lymphoma. Fifty-five percent of these patients had diffuse large-cell histologic features. When the relationship between histologic type and computed tomographic (CT) appearance was analyzed, the following trends were noted: A greater percentage of mixed cell tumors were multiple when compared with other types; noncleaved small-cell tumors were more commonly located in the central gray matter or corpus callosum than were other types; all immunoblastic tumors were enhanced homogeneously, unlike other types; and smaller tumors appeared to be associated with an increased histologic grade. Eleven patients had CT confirmation of a CNS recurrence; in eight patients, the recurrent tumor was in a different location than the original lesion. Eleven patients had associated intraocular lymphoma, and four were immunosuppressed.

Brain Neoplasms↗
PubMed1988

Selective posterior cerebral artery Amytal test for evaluating memory function before surgery for temporal lobe seizure.

Selective testing for memory function with Amytal (amobarbital) in the posterior cerebral artery (PCA) is a promising modification of that test in the internal carotid artery (ICA). This new technique, performed with a Tracker catheter system, was completed successfully in 17 of 20 patients being examined before planned surgery for refractory temporal lobe seizure. The PCA test overcomes three major problems with the ICA technique. First, with the PCA technique, memory testing is begun immediately after injection, when the drug has its peak effect. Second, when the speech-dominant hemisphere is being tested with the PCA test, patients do not become aphasic. Third, injection into the PCA delivers the drug more effectively to the target, the ipsilateral hippocampal formation.

Adolescent↗
PubMed1988

Use of MR imaging for quantitative evaluation of resection for temporal lobe epilepsy.

The postoperative magnetic resonance imaging studies of 40 patients who underwent surgery for medically refractory temporal lobe epilepsy were reviewed. A method for quantifying the resection of four specific medial temporal lobe structures--amygdala, uncus, hippocampal formation, and parahippocampal gyrus--was used to correlate postoperative seizure control with the degree to which those structures had been resected. Satisfactory postoperative seizure control was found to be strongly dependent (P less than .01) on the performance of at least partial resection of all four medial temporal lobe structures. The total amount of tissue removed did not necessarily correlate with the clinical outcome in individual cases, however, as long as some portion of all four medial structures had been resected. Two complicating factors--the presence of posterior or bilateral independent electroencephalographic foci and a history of meningoencephalitis--each negatively influenced surgical outcome (P less than .01). In cases with a complicating factor and inadequate medial resection, the outcome was invariably poor.

Adult↗
PubMed1988

Complications of spinal cord arteriography: prospective assessment of risk for diagnostic procedures.

A prospective study was done of complications associated with 134 consecutive diagnostic spinal cord arteriograms in 96 patients (63 men and 33 women aged 17-78 years). Patients were examined for either arteriovenous malformation (n = 88) or tumor (n = 8), as indicated by myelography. Among the complications, 11 (8.2%) were local, five (3.7%) were systemic nonneurologic, and three (2.2%) were neurologic (two were associated with full recovery in less than 24 hours, and one was associated with full recovery in less than 1 week). No specific clinical or technical factors were significantly associated with the development of neurologic complications. Details of the clinical profile, angiographic technique, and pathologic findings for each patient were recorded and analyzed with respect to the potential risk for arteriographic complications. Diagnostic spinal cord arteriography had an acceptable risk within the range of other neuroangiographic diagnostic procedures.

Adult↗