Differences in corpus callosum volume and diffusivity between temporal and frontal lobe epilepsy.

We analyzed volume and diffusivity measures of the corpus callosum (CC) in patients with temporal (TLE) and frontal (FLE) lobe epilepsy in comparison with healthy subjects. On high-resolution T1-weighted scans of 18 controls and 44 patients the volumes (cm(3)) of Witelson regions (WRs) and the entire CC were measured. The apparent diffusion coefficients (ADCs, 10(-5)mm(2)s(-1)) for the entire CC and three areas of interest were measured from co-registered ADC maps. The CC of patients with TLE and FLE, corrected for total brain volume, was smaller than that of controls. Patients' ADC values were higher than those of controls. Findings were significant for WR1, WR2, and WR6, the CC regions connecting the frontal and temporal lobes. Patients with FLE had smaller WR1 and higher ADC values; in patients with TLE, the findings were similar for WR6. Atrophy and increased diffusivity in subregions of the CC connecting homotopic contralateral cortical regions indicate anatomical abnormalities extending beyond the epileptogenic zone in FLE and TLE.

Diffusion tensor imaging in patients with focal epilepsy due to cortical dysplasia in the temporo-occipital region: electro-clinico-pathological correlations.

PURPOSE: Diffusion tensor imaging (DTI) provides information about magnitude (diffusivity) and directionality (anisotropy, FA) of water diffusion. We explored the characteristics of pathology-proven cortical dysplasia (CD) in the posterior quadrant in a case series of three patients using DTI measures, to assess associated alterations in subcortical connectivity and correlate with in situ epileptogenicity, seizure propagation and functional outcome. METHODS: The FA maps were visually inspected by a Neuroradiologist blinded to clinical data and conventional MRI (PR) and tractography was performed to assess connectivity of the dysplastic cortex and correlate with seizure propagation on invasive EEG. RESULTS: Analysis of FA maps revealed reduced connectivity with reduced arborization and thinning of the fiber bundles between the subcortical WM and the dysplastic cortex in patients 1 and 2, confirmed on tractography. Fiber tracts reconstructed from regions underlying the ictal onset help explain ictal propagation patterns. In the two patients without preexisting visual field deficit, resections spared the optic radiation visible on the FA map. CONCLUSIONS: Diffusivity measures and visualization of tracts provide complementary information on white matter changes accompanying CD and may assist to explain ictal spread patterns. Careful correlation with measures of function will allow the assessment of the functional significance of various dysplastic lesions and may help to design resective strategies.

Evidence for a basal temporal visual language center: cortical stimulation producing pure alexia.

BACKGROUND: Dejerine and Benson and Geschwind postulated disconnection of the dominant angular gyrus from both visual association cortices as the basis for pure alexia, emphasizing disruption of white matter tracts in the dominant temporooccipital region. Recently functional imaging studies provide evidence for direct participation of basal temporal and occipital cortices in the cognitive process of reading. The exact location and function of these areas remain a matter of debate. OBJECTIVE: To confirm the participation of the basal temporal region in reading. METHOD: Extraoperative electrical stimulation of the dominant hemisphere was performed in three subjects using subdural electrodes, as part of presurgical evaluation for refractory epilepsy. RESULTS: Pure alexia was reproduced during cortical stimulation of the dominant posterior fusiform and inferior temporal gyri in all three patients. Stimulation resulted in selective reading difficulty with intact auditory comprehension and writing. Reading difficulty involved sentences and words with intact letter by letter reading. Picture naming difficulties were also noted at some electrodes. This region is located posterior to and contiguous with the basal temporal language area (BTLA) where stimulation resulted in global language dysfunction in visual and auditory realms. The location corresponded with the visual word form area described on functional MRI. CONCLUSION: These observations support the existence of a visual language area in the dominant fusiform and occipitotemporal gyri, contiguous with basal temporal language area. A portion of visual language area was exclusively involved in lexical processing while the other part of this region processed both lexical and nonlexical symbols.

The value of interictal diffusion-weighted imaging in lateralizing temporal lobe epilepsy.

BACKGROUND: A subgroup of patients with nonlesional temporal lobe epilepsy (TLE) has no evidence of hippocampal sclerosis on standard temporal lobe protocol MRI. OBJECTIVE: To investigate whether interictal diffusion-weighted imaging adds lateralizing information in patients with TLE with and without lateralizing conventional MRI. METHODS: We studied 22 patients (9 right, 13 left TLE) who had undergone temporal lobectomy and 18 control subjects. We measured hippocampal volumes on high- resolution coronal magnetization-prepared rapid gradient echo scans. Apparent diffusion coefficients (ADCs) for the entire hippocampus and three arbitrarily defined areas of interest within the hippocampal head, body, and tail were measured from the coregistered ADC map. Pathology was reviewed and correlated with imaging findings. RESULTS: Fourteen of 22 patients had hippocampal atrophy on MRI (defined as volume asymmetry greater than 2 SDs compared with asymmetry in the control group). Overall, resected hippocampi (n = 22) were significantly smaller than contralateral hippocampi as well as ipsilateral hippocampi in controls. ADCs were significantly higher in resected hippocampi than contralateral hippocampi as well as ipsilateral hippocampi in controls. These differences were also observed within the three areas of interest. ADCs in the hippocampi contralateral to the epileptogenic zone (n = 22) were also higher than in ipsilateral hippocampi in controls. In the subgroup of eight patients with nonlateralizing conventional MRIs, ADCs of resected hippocampi were not significantly different compared with the contralateral side. Pathology in these patients revealed gliosis only without apparent neuron loss. CONCLUSION: Interictal apparent diffusion coefficients confirm lateralization in patients with hippocampal atrophy on standard temporal lobe protocol MRI. However, they do not provide lateralizing information in patients with nonlateralizing conventional MRI.

Temporal lobe volumes in patients with hippocampal sclerosis with or without cortical dysplasia.

BACKGROUND: Recent MRI-based volume reconstruction studies in intractable temporal lobe epilepsy (TLE) due to hippocampal sclerosis (HS) suggested atrophy that extends to the adjacent neocortical areas. OBJECTIVE: To study the extent of temporal lobe volume (TLV) abnormalities in patients with pathologically confirmed HS (with or without cortical dysplasia [CD]) who underwent anterior temporal lobectomy for the treatment of drug-resistant TLE. METHODS: Fifty patients (right TLE: n = 24; left TLE: n = 26) were found to have HS (hippocampal cell loss of >30%). Associated neocortical CD was seen in 20 patients (43%). MRI-based TLVs and hippocampal and hemispheric volume reconstructions in all patients were compared between pathologic groups and with volumes acquired from 10 age-matched control subjects. RESULTS: TLVs ipsilateral to the epileptogenic zone in patients with TLE were smaller than TLVs in control subjects (p < 0.01). In patients with left TLE, TLVs ipsilateral to the epileptogenic zone were smaller than contralateral TLVs (left: 66.6 +/- 8.3 cm3, right: 74.9 +/- 10.0 cm3; p < 0.001). In patients with right TLE, there were no significant asymmetries. The contralateral TLVs (regardless of the side of surgery) were smaller in the HS + CD group than the HS group (HS + CD group: 74.9 +/- 8.6 cm3, HS group: 79.7 +/- 6.6 cm3; p < 0.05). Patients with HS + CD had a tendency to have less hippocampal atrophy and slightly smaller TLVs ipsilateral to the epileptogenic zone, accounting for significantly smaller TLV/hippocampal volume ratios compared with patients with HS alone. CONCLUSIONS: Drug-resistant TLE due to HS is associated with extrahippocampal temporal lobe atrophy. The presence of bilateral temporal lobe atrophy is suggestive of a more widespread (bilateral) temporal lobe involvement in patients with HS and CD.

Evidence of cingulate motor representation in humans.

A 44-year-old man with a right frontal lobe tumor and intractable seizures underwent subdural grid evaluation before resection. The electrode locations were identified on a three-dimensional surface-reconstructed image of the brain after subdural grid placement. Electrical stimulation of electrodes placed over the right cingulate gyrus revealed evidence of tonic posturing of the left forearm and wrist and tonic extension of the left leg. This finding provides further evidence of a motor area in the cingulate gyrus in humans.

Epileptogenicity correlated with increased N-methyl-D-aspartate receptor subunit NR2A/B in human focal cortical dysplasia.

PURPOSE: Human cortical dysplasia (CD) is a frequent cause of medically intractable focal epilepsy. The neurotransmitter mechanisms of epileptogenicity in these lesions have been attributed to changes in various glutamate receptor subtypes. Increased N-methyl-D-aspartate (NMDA) receptor (NR) 2A/B coassembled with NR1 subunits has been shown in focal epileptic CD. The purpose of this study is to correlate in situ CD epileptogenicity and the expression of various glutamate receptor subtypes. METHODS: The histopathological, morphological, and immunocytochemical findings in cortical tissue resected from five patients with medically intractable epilepsy and CD were correlated with electroencephalographic data recorded from subdural grids. The NMDA antibodies identified subunits NR1 (splicing variants 1a, 1b, 2a, and 2b) and NR2A/B. RESULTS: Epileptogenic specimens displayed the following common features: (a) widespread histological abnormalities of horizontal and columnar dyslamination, neurons with inverted polarity, and more extensive dendritic changes; (b) significantly higher NR2A/B immunoreactivity in both the dysplastic somata and all their dendritic processes; and (c) no statistically significant change in NR1 subunit expression but a more pronounced staining of the apical dendrites in highly epileptogenic cortex. These abnormalities were either absent or minimal in resected specimens that did not show evidence of severe in vivo epileptogenicity. CONCLUSION: These studies provide direct evidence for a major contribution of the NR2A/B subunit in CD-induced epileptogenicity.

A low-cost PCI-bus-based ultrasound system for use in image-guided neurosurgery.

A low-cost PCI-bus-based ultrasound sub-system has been developed and integrated into the image-guided neurosurgery system currently in use at the Cleveland Clinic. Two software applications have been developed that integrate real-time ultrasound images with preoperative MR and CT data sets. By tracking the position of the ultrasound probe during surgery, it is possible to display a real time ultrasound image and the corresponding (preoperative) oblique CT or MR slice. This provides immediate positional feedback to the neurosurgeon during the surgical procedure.

Quantitative detection of outlet strut separations in Björk-Shiley convexo-concave mitral valves.

BACKGROUND: As of January 31, 1995, 564 outlet strut fractures (OSFs) of Björk-Shiley convexo-concave (BSCC) heart valves had been reported to the Shiley Heart Valve Research Center, of which approximately two thirds resulted in the death of the patient. Previous studies indicate that one leg of the outlet strut separates (single-leg separation, SLS) from the valve before the second leg breaks, which results in complete OSF. To identify those valves at risk of complete OSF, an in vivo radiographic imaging technique is being developed to evaluate the strut leg integrity. The goal of the present study was to develop an objective postprocessing technique to evaluate outlet strut leg integrity quantitatively in these cineradiographic images. METHODS AND RESULTS: Twenty-two sets (12 intact valves, 10 SLS valves) of cineangiographic images were obtained from individuals whose valve status was subsequently verified ex vivo. Several quantitative measures of SLS were evaluated to identify possible loss of metal or gaps in the SLS legs. Two of these measures, decrease in pixel intensity (DIPI) ratio and gap half-width, are diagnostic metrics of SLS: i.e., the maximum likelihood estimate of the area under the receiver operating characteristic curve was 0.892 (SD, 0.066) for a model based on DIPI ratio and 0.802 (SD, 0.093) for gap half-width. CONCLUSIONS: We have developed a postprocessing technique that can be used to objectively evaluate outlet strut integrity in cineradiographic images of BSCC heart valves. At an estimated specificity of 1.0, the estimated sensitivity of the objective review was comparable to that of a subjective expert review panel.

A medical workstation for the display and analysis of multi-frame digital cineradiographic data.

A medical workstation has been developed for the efficient display and analysis of large sets of digital cineradiographic images. Various features aid the clinician in quickly identifying and extracting the image information relevant for diagnosis: animated viewing of image frames, a digital magnifying glass for local image enlargement and enhancement, a special review queue for critical image frames, and task-oriented image processing. Double frame buffering and direct memory addressing ensure fast, artifact-free image display and transfer. Much freedom is provided for adapting the system to one's own preferences. A statistical analysis of extensive tests conducted by eight clinical expert reviewers is given.