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David C Reutens

Publications and source records attributed to David C Reutens.

18 recordsLinked to original sources
PubMed2006

Neurological control of human sexual behaviour: insights from lesion studies.

We review the human literature examining the effects of neurological insult on human sexual behaviour. We provide a synthesis of the findings to date, and identify key brain regions associated with specific aspects of human sexual behaviour. These include subcortical and cortical regions, with the mesial temporal lobe and the amygdala in particular being a crucial structure in the mediation of human sexual drive.

Amygdala↗
PubMed2006

A GABAA receptor mutation causing generalized epilepsy reduces benzodiazepine receptor binding.

Understanding the consequences of newly discovered single gene mutations causing human epilepsy has the potential to yield new insights into the underlying mechanisms of this disorder. A mutation of the gamma2 subunit of the GABA(A) receptor, which substitutes glutamine for arginine at position 43 (R43Q) has been found in a familial generalized epilepsy. We tested the hypothesis that individuals affected by the GABRG2(R43Q) mutation have reduced binding to the GABA(A) receptor complex using positron emission tomography (PET) and the benzodiazepine receptor ligand [(11)C]-flumazenil. Fourteen subjects with the GABRG2(R43Q) mutation and 20 controls were studied. Benzodiazepine receptor binding was reduced in subjects with the mutation (mean whole brain binding potential for [(11)C]-flumazenil: GABA(A) mutation 0.66+/-0.1; controls 0.89+/-0.1; P<0.003). The greatest change in benzodiazepine binding occurred anteriorly, with peak differences in insular and anterior cingulate cortices revealed by statistical parametric mapping. Our findings provide in vivo evidence of reduced benzodiazepine receptor binding in subjects with the mutation. As synaptic inhibition in the human brain is largely mediated by the GABA(A) receptor, these findings are likely to represent an important clue to the mechanisms linking this gene defect and the epilepsy phenotype.

Adult↗
PubMed2006

Ischemic thresholds for gray and white matter: a diffusion and perfusion magnetic resonance study.

BACKGROUND AND PURPOSE: Although gray matter (GM) and white matter (WM) have differing neurochemical responses to ischemia in animal models, it is unclear whether this translates into differing thresholds for infarction. We studied this issue in ischemic stroke patients using magnetic resonance (MR) techniques. METHODS: MR studies were performed in patients with acute hemispheric ischemic stroke occurring within 24 hours and at 3 months. Cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and apparent diffusion coefficient (ADC) were calculated. After segmentation based on a probabilistic map of GM and WM, tissue-specific diffusion and perfusion thresholds for infarction were established. RESULTS: Twenty-one patients were studied. Infarction thresholds for CBF were significantly higher in GM (median 34.6 mL/100 g per minute, interquartile range 26.0 to 38.8) than in WM (20.8 mL/100 g per minute; interquartile range 18.0 to 25.9; P<0.0001). Thresholds were also significantly higher in GM than WM for CBV (GM: 1.67 mL/100 g; interquartile range 1.39 to 2.17; WM: 1.19 mL/100 g; interquartile range 0.94 to 1.53; P<0.0001), ADC (GM: 918x10(-6) mm2/s; 868 to 975x10(-6); WM: 805x10(-6); 747 to 870x10(-6); P<0.001), and there was a trend toward a shorter MTT in GM (GM 4.94 s, 4.44 to 5.38; WM 5.15, 4.11 to 5.68; P=0.11). CONCLUSIONS: GM has a higher infarction threshold for CBF, CBV, and ADC than WM in patients within 24 hours of ischemic stroke onset. Hence, when assessing patients for potential therapies, tissue-specific rather than whole-brain thresholds may be a more precise measure of predicting the likelihood of infarction.

Aged↗
PubMed2006

The ASPECTS template is weighted in favor of the striatocapsular region.

The extent of cerebral infarction correlates with increased risk of intracerebral hemorrhage (ICH) following recombinant tissue plasminogen activator (rt-PA) administration. The Alberta Stroke Program Early CT Score (ASPECTS) is a widely used, validated method which assesses involvement of 10 selected regions of the MCA territory. An ASPECTS score >7 is associated with a higher risk of ICH following thrombolysis than lower scores. To understand the internal structure of the ASPECTS template better, we estimated the infarct volume corresponding to each region. We hypothesized that, in the ASPECTS scoring system, the striatocapsular region is weighted disproportionally. Four experienced radiologists rated individual ASPECTS regions on subacute CT images (day 5-day 10) of 19 patients with MCA territory stroke. Infarct volume was determined from manual segmentation of infarcts on CT images. Linear regression was used to estimate the regional volume associated with each ASPECTS region. The ASPECTS regions are weighted unequally with the striatocapsular region accounting for 21% of the MCA territory infarct volume. Together, the 10 ASPECTS regions account for approximately 51% of the maximum MCA infarct territory volume. These findings should provide impetus for research to develop a scoring system explicitly based on regional hemorrhage risk as an aid to selecting patients for thrombolysis.

Aged↗
PubMed2005

Is white matter involved in patients entered into typical trials of neuroprotection?

BACKGROUND AND PURPOSE: One of the reasons for the failure of trials of neuroprotection in stroke may be the lack of white matter (WM) protection. However, whether patients entered into typical neuroprotection trials have WM involved in the ischemic process is unknown. We studied patients who were enrolled in neuroprotection trials at our center and used a neuroimaging coregistration approach to determine whether final infarcts involved WM and, if so, in what proportion. We also aimed to provide the first in vivo volume distribution of gray matter (GM) and WM in normal stroke-aged brains. METHODS: Patients enrolled in trials of neuroprotection had late computed tomography or magnetic resonance scans coregistered in standard stereotaxic coordinate space after segmentation of symptomatic cerebral infarcts. These were then superimposed on a probabilistic map of GM and WM, which was developed from age-matched normal controls in whom GM and WM volumes were assessed. RESULTS: Forty-two patients (mean age, 73.7+/-10.5 years) were studied from 6 trials of neuroprotection. WM formed 41.7% of the brain volume in 37 control subjects (mean age, 73.5+/-8.4 years). In the segmented infarcts, WM comprised a median of 49% (interquartile range, 36.5 to 77.9) of the infarct volume. Ninety-five percent of infarcts had some involvement of WM tracts. CONCLUSIONS: WM occupies approximately 42% by volume of the normal stroke-aged brain. Patients entered into typical trials of neuroprotection may have significant WM volumes involved in the ischemic process, thus providing a rationale for the development of neuroprotectants for this compartment.

Aged↗
PubMed2005

The existence and evolution of diffusion-perfusion mismatched tissue in white and gray matter after acute stroke.

BACKGROUND AND PURPOSE: Although white matter is a potential target of acute stroke therapy, there is uncertainty about its relative resistance to ischemia and whether it is capable of mounting a penumbral response. To explore these issues further, we examined the differential effects of ischemia on gray and white matter using magnetic resonance (MR) perfusion-diffusion mismatch after acute stroke. METHODS: MR imaging studies were performed within 12 hours in patients with initial hemispheric ischemic stroke. "At-risk" tissue was defined as tissue with abnormal diffusion-weighted imaging/perfusion-weight imaging or infarction on follow-up image. Tissue was segmented using a probabilistic atlas generated from age-matched controls. The proportions of "at-risk" tissue, which was penumbral at the time of imaging, were compared between gray and white matter. RESULTS: Thirty-two patients had diffusion-perfusion mismatched penumbral tissue present in both gray and white matter compartments. Although the absolute mismatch volumes were greater in gray (median 42 cm3, interquartile range 18 to 70 cm3) than in white matter (39 cm3, 17 to 49 cm3; P<0.001), the proportion of "at-risk" tissue, which was penumbral at the time of imaging (median 3.7 hours, range 1.5 to 9.9 hours) was greater in white (69%, 49% to 86%) than gray matter (62%, 52% to 75%; P=0.026). However, the proportions spontaneously salvaged by 3 months were similar in both compartments. CONCLUSIONS: These findings are consistent with white matter being able to mount an ischemic penumbral response in humans and being more resistant to cerebral ischemia than gray matter. They also raise the possibility that the therapeutic window is longer for white matter and may require alternative therapeutic strategies.

Aged↗
PubMed2005

Assessment of the role of FDG PET in the diagnosis and management of children with refractory epilepsy.

PURPOSE: We performed a retrospective analysis of the results of FDG PET scans in children with refractory epilepsy referred to our centre over an 8-year period, with a view to ascertaining the impact of FDG PET on subsequent patient management. METHODS: A questionnaire was used to assess the impact of FDG PET scan on diagnosis, management and clinical decision-making processes for epilepsy surgery from the managing clinician's perspective. FDG PET scan results were also compared with MRI, EEG and SPECT results and coded according to whether the FDG PET scan provided independent information and localisation of epileptogenic regions. RESULTS: A total of 118 eligible patients under the age of 14 years were identified, with questionnaires being completed on 113 evaluable patients (96%). The pre-PET management plan consisted of consideration for surgery in 92 patients (81%) and medical therapy for the remaining 21 patients (19%). Managing physicians rated FDG PET as providing information additional to that obtained with other investigations regarding epileptogenic sites in 88 patients (77%). FDG PET had either a minor or a major impact on clinical management in 58 patients (51%), principally with regard to surgical candidacy. CONCLUSION: FDG PET has a definite role in the assessment of paediatric patients with refractory epilepsy who are being considered for surgery. In the future, analysis of FDG PET data in specific subpopulations of children with refractory epilepsy may lead to novel insights regarding aetiology.

Anticonvulsants↗
PubMed2005

A digital map of middle cerebral artery infarcts associated with middle cerebral artery trunk and branch occlusion.

BACKGROUND AND PURPOSE: Knowledge of the topographic distribution of infarcts of the middle cerebral artery (MCA) may give insight into the limits of the arterial territory and infarct mechanism and may influence the decision to use thrombolytic therapy. We describe the creation of a digital atlas of MCA (DA-MCA) infarction associated with MCA branch and trunk occlusion using magnetic resonance (MR) techniques. METHODS: Hemispheric infarcts, with evidence of MCA trunk or branch occlusion, were manually segmented into binary images, linearly registered into a common stereotaxic coordinate space, and averaged to yield the probability of involvement by infarction at each voxel. Comparisons were made with existing maps of the MCA territory. RESULTS: Twenty-eight patients with median age of 74 years (range, 26 to 87 years) were studied. On the DA-MCA, the highest frequency of infarction was within the striatocapsular region, centrum semiovale, and the insula. The mean and maximal MCA infarct volumes were 195.5 cm3 and 366.3 cm3, respectively. Comparison with published maps showed that the most common difference from the DA-MCA was in the superomedial extent of the MCA territory. Some maps showed the MCA territory reaching the interhemispheric fissure, whereas in the DA-MCA it did not. There was a lower variability in the anterior boundary of the MCA territory compared with its posterior counterpart. CONCLUSIONS: We have created a digital atlas of MCA infarction using MR imaging techniques. This approach may be useful to establish the distribution of the MCA and other arterial territories and the border zones between them with greater certainty.

Adult↗
PubMed2004

The amygdala and sexual drive: insights from temporal lobe epilepsy surgery.

The aim of this study was to explore the relationship between the amygdala and human sex drive. We compared amygdalar volume in groups of patients with or without sexual changes after temporal lobe resection and in age-matched neurologically normal subjects. Forty-five patients with intractable temporal lobe epilepsy who underwent surgical resection in the Comprehensive Epilepsy Program at the Austin and Repatriation Medical Centre completed a semistructured interview and questionnaire relating to sexual outcome after surgery. Volumetric analyses of both amygdalae were conducted on the patients' preoperative T(1)-weighted magnetic resonance imaging scans and those of 46 neurologically normal controls. Patients who reported a postoperative sexual increase had a significantly larger amygdalar volume contralateral to the site of their resective surgery than patients with a sexual decrease or no change than control subjects. There was a significant positive relationship between contralateral amygdalar volume and the maximum degree of sexual change. We have demonstrated a relationship between contralateral amygdalar volume and sexual outcome in patients undergoing temporal lobe resection. This finding provides evidence for an important role of the amygdala in regulating human sexual behavior. A larger contralateral amygdala may contribute to the expression of increased or improved sexuality after temporal lobe resection.

Adult↗
PubMed2004

The resistance to ischemia of white and gray matter after stroke.

A contributing factor to the failure of trials of neuroprotectants in acute ischemic stroke may be the differing vulnerability to ischemia of white compared with gray matter. To address this issue, we determined to establish the existence of potentially viable tissue in white matter and its evolution to infarction or salvage in both gray and white matter compartments in patients with ischemic stroke. Twenty-seven patients (mean age, 73.4 years) at a median of 16.5 hours after symptom onset were studied using the hypoxic marker 18F-misonidazole with positron emission tomography (PET). Tissue was segmented using an magnetic resonance probabilistic map. Although there was a greater volume of initially "at-risk tissue" in gray matter (58.3 cm3, 29.9-93.0 cm3 than white matter (42.0 cm3, 15.8-74.0 cm3; p <0.001) at the time of PET imaging, a higher proportion of this was still potentially viable in white matter (41.4%, 4.6-74.5%) than in gray matter (23.6%, 3.2-61.1%; p <0.05). However, a similar proportion in each compartment spontaneously survived. These data provide evidence for the existence of potentially salvageable tissue in human white matter and is consistent with it having a similar or even greater resistance to ischemia than gray matter. For the latter possibility, alternative therapeutic strategies may be required for its salvage.

Adult↗
PubMed2003

alpha-[11C]-Methyl-L-tryptophan PET identifies the epileptogenic tuber and correlates with interictal spike frequency.

Epilepsy surgery has been successfully performed in patients with tuberous sclerosis complex (TSC) and seizures arising from a restricted epileptogenic area. The outcome of cortical excision depends on accurate pre-surgical identification of the epileptogenic tuber. [11C] alpha-methyl-L-tryptophan (alpha-MTrp) was originally developed to measure serotonin synthesis in vivo with positron emission tomography (PET). However in pathologic conditions its uptake may also depend on the synthesis of quinolinic or kynurenic acid via the kynurenine pathway. Increased levels of serotonin and quinolinic acid have been observed in epileptogenic lesions, raising the possibility that alpha-MTrp PET may localize the epileptogenic area. The aim of this study was to correlate alpha-MTrp PET uptake with the localization of the epileptogenic area and with interictal spike frequency in patients with TSC. alpha-MTrp uptake was measured in 8 patients (2 males, mean age 29.6+/-14.9 years, range 3-50 years) with intractable partial epilepsy due to TSC. All patients underwent scalp EEG monitoring during the PET scan. In four (50%), increased uptake of alpha-MTrp occurred in the epileptogenic area alone. Two (25%) patients showed multifocal abnormalities and the remaining two (25%) did not show focal changes. PET localization was mostly seen in patients with frequent interictal abnormalities on the EEG. Furthermore, there was a significant correlation between alpha-MTrp uptake and the frequency of interictal spikes (r=0.6; P<0.05). alpha-MTrp PET is a promising diagnostic tool in the localization of the epileptogenic area in patients with TSC.

Adolescent↗
PubMed2003

Sexual outcome after epilepsy surgery.

The aim of this study was to provide a description of patient-perceived sexual change after temporal lobe resection (TLR) and extratemporal resection (ETR). Fifty-eight TLR and sixteen ETR patients completed a semistructured interview and questionnaire assessing sexual change after epilepsy surgery. Five areas of sexual functioning were addressed: sexual drive, thoughts/fantasies, interest, masturbation, and activity. Each patient's perception of sexual changes relative to perceived levels of normal functioning was assessed. Characteristically, the onset of sexual change occurred in the first three postoperative months and persisted to the time of interview. A postoperative sexual change was significantly more likely to be reported by patients who had undergone TLR (64%) than ETR (25%). In the TLR group, sexual change was significantly more frequent following right-sided resections. Marked sexual change occurred more frequently in females than males. Postoperative sexual change is an important outcome feature after epilepsy surgery. The predisposition of TLR patients to postoperative change provides further evidence for a temporal lobe contribution to sexual function.

Adolescent↗
PubMed2002

Exercise-induced temporal lobe epilepsy.

Although precipitation of seizures by exercise has been described, the reproducible induction of temporal lobe seizures by exercise is unusual. The authors report two patients with left temporal lobe seizures induced by exercise. In one patient the family history suggested autosomal-dominant inheritance. Prolonged hyperventilation, simple movements, and visualization of a competitive game did not produce epileptiform discharges on the interictal EEG.

Adolescent↗
PubMed2002

Verbal memory in left temporal lobe epilepsy: evidence for task-related localization.

We explored the hypothesis that components of verbal memory are subserved by separate temporal lobe structures in patients with temporal lobe structures in patients with temporal lobe epilepsy [correction]. Uptake of 18F-fluorodeoxyglucose (FDG) measured by positron emission tomography, hippocampal volume, and memory for arbitrarily and semantically related verbal paired associates were examined in 27 patients with left temporary lobe epilepsy. Scores from memory tests performed outside the scanner were regressed against normalized resting FDG uptake at each voxel. Significant regression was seen in the left perirhinal cortex (Talaraich coordinates x, y, z: -29, 10, -34; p < 0.05) for arbitrarily related word pairs. For semantically related paired associates, significant regression was present in the left inferior temporal gyrus (x, y, z: -48, -18, -24; p < 0.05). In subsequent analyses, mean FDG uptake within a spherical region of interest centered on the perirhinal peak predicted performance on both tasks. Mean FDG uptake in a region of interest centered on the inferior temporal peak made an additional, independent contribution to memory for semantically related pairs. Hippocampal volumes did not explain any additional variance in memory scores. Our findings indicate that heterogeneity in the left temporal lobe structures mediating verbal memory function, and support the view that the perirhinal cortex is an important mnemonic substrate.

Adolescent↗
PubMed2002

Functional topography of the low postcentral area.

OBJECT: The goal of this study was to establish a reliable method for identification of face and tongue sensory function in the lower central area. METHODS: All positron emission tomography (PET) clinical activation studies performed over a 3-year period at the Montreal Neurological Institute and Hospital were evaluated by coregistering the PET images with three-dimensional reconstructions of magnetic resonance images obtained in the same patients. In addition to stereotactic coordinates and measurements based on distance from the sylvian fissure, gyral and sulcal landmarks were analyzed to determine their reliability in localizing the sensory areas of the tongue and lower face. The convolutional anatomy of the central area is an important guide to the identification of function. The sensory area of the tongue is recognized as a triangular region at the base of the postcentral gyrus; the sensory area of the lower face resides in the narrowed portion of the postcentral gyrus, immediately above the tongue area. CONCLUSIONS: Cortical landmarks such as the substrata of tongue and face sensory impressions are more reliable guides than stereotactic coordinates or measurements for localizing function.

Adolescent↗
PubMedDate not supplied

Inhomogeneity correction for brain magnetic resonance images by rank leveling.

OBJECTIVE: A postprocessing method of rank filtering inhomogeneity correction using nonlinear rank filtering of magnetic resonance imaging (MRI) scans is described. The method addresses some of the problems of homomorphic unsharp masking (HUM) using mean or median filtering. METHODS: Maximum rank filtering was used to estimate the bias image, which was then smoothed and used to normalize the original image. The coefficient of variation within and between tissue classes before and after inhomogeneity correction was calculated in simulated brain phantom images and clinical T1-weighted MRI images. Comparison was made with mean filter-based and median filter-based HUM. RESULTS: Maximum rank filtering reduced within and between class coefficients of variation. Performance of median filtering was inferior to that of mean filtering, and both were inferior to performance of maximum rank filtering. CONCLUSION: The method is easy to implement and is effective against different bias types. It is less prone to edge effects than mean and median filtering.

Algorithms↗