Three-dimensional time-of-flight MR angiography with a surface coil: evaluation in 12 subjects.

We compared three-dimensional time-of-flight MR angiograms obtained with head coils and then with surface coils in five patients with intracranial vascular lesions and in seven normal volunteers to determine if imaging of intracranial vascular anatomy could be improved with the use of a surface coil. Visualization of small peripheral vessels was consistently better with a surface coil than with a head coil at identical small fields of view (FOVs). The surface-coil technique allowed small-FOV imaging of peripheral vascular lesions with higher spatial resolution and signal-to-noise ratio similar to that of large-FOV head-coil images. The use of a surface coil introduced the problem of signal falloff; centrally located vessels were visualized as well or better when a standard head coil was used. We conclude that surface-coil MR angiography can serve as a useful adjunct to routine head-coil MR angiography in the evaluation of peripheral vascular abnormalities.     

Efficacy of MR vs CT in epilepsy

We studied 59 seizure patients with CT, MR, and EEG to determine the efficacy of each in the detection of an epileptogenic focus. EEG was most sensitive (67%), MR was next (53%), and CT was least sensitive (42%). MR detected an abnormality in five patients (8%) in whom CT was negative. EEG was positive in each of these patients. CT failed to demonstrate any focal lesion not detected by MR. MR and CT detected focal abnormalities in seven patients (12%) who had negative EEGs. Five of the seven patients had brain tumors. Eighteen of the 26 patients who underwent surgery had positive CT and MR; 14 of these patients had tumors. The remaining eight patients who had surgery all had temporal lobectomies for intractable seizures; none had tumors. In the complex partial seizure subgroup of 34 patients, MR was positive in 44%, CT was positive in 29%, and EEG was positive in 80%. We consider MR to be the imaging procedure of choice for the detection of an epileptogenic focus in seizure patients. When indicated, CT may be performed as a second procedure to try to distinguish neoplasm from thrombosed vascular malformations and other lesions.     

Hypometabolic cortical lesions in tuberous sclerosis with epilepsy: demonstration by positron emission tomography

Four patients with a well-established diagnosis of tuberous sclerosis and grand mal type epileptic seizures as their principal clinical symptom were examined by conventional surface electroencephalography (EEG), X-ray computed tomography, and positron emission tomography (PET) using the [18F]-2-fluoro-2-deoxyglucose method. The interictal EEG showed various abnormalities of poor localizing value, but no focal epileptic discharges. X-ray computed tomography demonstrated subependymal calcifications in all cases, although cortical lesions were found only twice. However, in the PET images of each patient one or two localized cortical foci with a metabolic rate for glucose more than 40% lower than in the respective contralateral region were clearly delineated. It may be assumed that those hypometabolic areas represent the epileptogenic cortical tubers, which are characteristic of the disease but usually cannot be detected in vivo by other methods.     

18 F-FDG PET显像对致痫灶的定位诊断价值

目的　探讨 18F -脱氧葡萄糖 (FDG)PET显像对癫痫灶的定位诊断价值。方法　难治性癫痫患者 2 2例 ,男 15例 ,女 7例 ,平均年龄 19.0岁 ,平均病程 8.2年。所有患者均进行常规 18F -FDGPET显像 ,结合脑电图 (EEG)及MRI、CT对 2 1例患者进行开颅手术 ,术中在皮层脑电图 (EcoG)监测下行致痫灶切除术 ,并送病理学检查 ;另 1例进行立体定向杏仁、海马损毁术。所有患者术后随访疗效。结果　 2 2例癫痫患者中 ,2 1例 18F -FDGPET显像阳性 (95 .5 % ) ,2 0例表现为发作间期低代谢灶 ,1例为发作期高代谢灶 ;EEG检查阳性 17例 (77.3 % ) ,其中 8例无定位意义 ;CT、MRI阳性者 5例 (2 2 .7% ) ;18F -FDGPET定位的致痫灶与EcoG一致的有 18例 (85 .7% ) ,不完全一致的 2例 ,不一致的 1例 ;18F -FDGPET显像阳性 19例中 ,18例手术病理异常 (94.7% ) ,PET阴性的 1例手术病理为正常脑组织 ;开颅手术治疗后 ,癫痫发作完全消失者 9例 (4 2 .9% ) ,癫痫发作次数减少 5 0 %以上者 9例 (4 2 .9% ) ,发作次数无明显变化 3例 (14 .3 % ) ;另 1例进行立体定向杏仁海马损毁术的患者癫痫发作次数无明显变化。结论　18F -FDGPET显像对致痫灶的定位诊断灵敏、准确 ,对指导癫痫外科手术有重要的临床价值     

Cortical dysplasia localized by [11C]methionine positron emission tomography: case report

Numerous functional neuroimaging techniques have progressively been added to the presurgical evaluation of refractory partial epilepsies. These investigations can help confirm the origin of seizure onset previously suggested by MR imaging and electro-clinical data, provide independent prognostic information, and provide critical diagnostic value when MR imaging results are strictly normal or show multifocal abnormalities. Of the various functional neuroimaging modalities, [11C]methionine positron emission tomography for methionine uptake into seizure foci is still in the preliminary stages of investigation. A single case of medically intractable epilepsy with focal cortical dysplasia documented by [11C]methionine positron emission tomography and possible hypotheses to explain the methionine uptake into the seizure focus are described below.     

1H MR spectroscopic imaging in patients with MRI-negative extratemporal epilepsy: correlation with ictal onset zone and histopathology

Proton magnetic resonance spectroscopy (¹H MRS) is beneficial in the lateralization of the epileptogenic zone in temporal lobe epilepsy; however, its role in extratemporal and, especially, MRI-negative epilepsy has not been established. This study seeks to verify how ¹H MRS could help in localizing the epileptogenic zone in patients with MRI-negative extratemporal epilepsy. Seven patients (8–23 years) with MRI-negative refractory focal epilepsy were studied using ¹H MRS on a 1.5T MR system. Chemical shift imaging sequence in the transversal plane was directed towards the suspected epileptogenic zone localized by seizure semiology, scalp video/EEG, ictal SPECT and ¹⁸FDG-PET. Spectra were evaluated using the program CULICH, and the coefficient of asymmetry was used for quantitative lateralization. MRS detected lateralization in all patients and was able to localize pathology in five. The most frequent findings were decreased ratios of N-acetylaspartate to choline compounds characterized by increasing choline concentration. The localization of the ¹H MRS abnormality correlated well with ictal SPECT and subdural mapping. In all cases, histopathological analysis revealed MRI-undetected focal cortical dysplasias. ¹H MRS could be more sensitive for the detection of discrete malformations of cortical development than conventional MRI. It is valuable in the presurgical evaluation of patients without MRI-apparent lesions. Pavel Krsek and Milan Hajek contributed equally to this work.     

White matter abnormalities in the anterior temporal lobe suggest the side of the seizure foci in temporal lobe epilepsy

Introduction White matter abnormalities in the anterior temporal lobe (WAATL) are sometimes observed on magnetic resonance (MR) images of patients with temporal lobe epilepsy (TLE). Our purpose was to determine whether WAATL could indicate if the seizure foci are ipsilateral on electroencephalograms (EEG) in TLE patients.Methods We reviewed 112 consecutive patients with medically intractable TLE. We compared the side of seizure foci on EEG (preoperative and intraoperative) and MR images.Results Both loss of gray–white matter demarcation and increased signal intensity changes in the anterior white matter (positive WAATL) were observed in 54 of 112 patients (48.2%) with TLE. WAATL were present on the same side as the seizure foci on preoperative intracranial EEG with subdural electrodes (iEEG) and on intraoperative electrocorticography (ECG) in all the patients. In 47 patients, MR images showed WAATL and focal lesions that were possibly epileptogenic for TLE. In 2 of the 47 patients, the seizure foci on iEEG and ECG were contralateral to the focal lesion; in the remaining 45 patients, the seizure foci on surface EEG (sEEG) and ECG and the focal lesion were on the same side. In three patients, no focal lesions were seen but WAATL were present on the same side as the seizure foci on sEEG and ECG. In four patients, MR images showed focal lesions for which epileptogenicity was questionable, and WAATL on the same side as the seizure foci on EEG.Conclusion WAATL are clinically useful because they indicate the side of the seizure foci.     

Imaging of the epilepsies

Imaging of epilepsy patients is challenging, since epileptogenic lesions (defined as structural lesions causally related to the epilepsy syndrome) may be small and often do not change during life. Prior clinical information about the epilepsy syndrome and the semiology of the seizures is needed in order to plan the examination properly. The effort to detect an epileptogenic lesion is directed to partial (focal) epilepsy syndromes whereas—by definition—no lesion is identified in idiopathic epilepsies. Most patients with partial epilepsies suffer from mesial temporal lobe epilepsies. In these patients, 2- to 3-mm-thick T2-weighted and fluid-attenuated inversion-recovery (FLAIR) fast spin echo slices along or perpendicular to the temporal lobe length axis have the highest diagnostic efficacy. In contrast, in patients with extratemporal lobe epilepsies perpendicular FLAIR slices through the anatomic region, from which, due to clinical and EEG criteria, the seizures are likely to originate, are preferred. The imaging features of common epileptogenic lesions (hippocampal sclerosis, long-term epilepsy-associated tumours, focal cortical dysplasias, vascular malformations, encephalitis including limbic and Rasmussens encephalitis, gyral scarring including ulegyria) are detailed in the second section of this paper.     

Surface-coil MR of orbital pseudotumor

Fifteen patients with clinical presentations compatible with idiopathic inflammatory orbital pseudotumor were examined by CT and MR imaging to determine if MR could add specificity to the CT appearance of this entity. MR was performed on a 1.5 T system, using surface-coil and head-coil techniques. Idiopathic pseudotumor was confirmed in nine patients on the basis of response to steroid therapy in the absence of local cause or systemic illness. One other patient had biopsy-proven idiopathic pseudotumor. Five patients proved to have other orbital entities, including metastases, infectious myositis, hemorrhage, and orbital sarcoid. In all 10 patients with confirmed pseudotumor, CT and MR were abnormal. MR abnormalities in 10 of 10 patients with pseudotumor were hypointense to fat and isointense to muscle on T1-weighted images. On T2-weighted images the lesions of pseudotumor were isointense or only minimally hyperintense to fat in nine of 10 cases; in one case, the enlarged muscle was markedly hyperintense to fat. The MR signal intensity of pseudotumor was similar to that found in infectious myositis and sarcoid. These findings contrasted to the MR appearance of the other disease entities examined. Metastases appeared markedly hyperintense to fat on T2-weighted images, while hematoma was hyperintense to muscle and isointense to fat on T1-weighted images and markedly hyperintense to fat on T2-weighted images. In our preliminary series, surface-coil MR appears to add specificity to the CT appearance of orbital pseudotumor.     

Brain single-photon emission tomography with99mTc-HMPAO in neuropsychiatric systemic lupus erythematosus: relations with EEG and MRI findings and clinical manifestations

Central nervous system (CNS) involvement in patients with systemic lupus erythematosus (SLE) is often difficult to evaluate because of protean neuropsychiatric (NP) manifestations and lack of reliable diagnostic markers. In the reported study the role of single-photon emission tomography (SPET) with technetium-99m hexamethylpropylene amine oxime (HMPAO) in the evaluation of CNS involvement in SLE was assessed and the relations between SPET perfusion defects, EEG examination, magnetic resonance imaging (MRI) findings and clinical presentation were examined. Twenty SLE patients with different NP manifestations were studied. Multiple areas of hypoperfusion, especially in the territory of the middle cerebral artery, were demonstrated by SPET analysis in all 20 patients. The number of hypoperfused areas and the degree of were more marked in patients with multiple NP manifestations. MRI and EEG evaluations were positive for 14 of 18 and for 12 of 20 patients, respectively. In the patients with positive SPET and MRI, 87 MRI focal lesions and 63 hypoperfused areas were found, and for 51 of these 63 at least one MRI lesion was found in the same anatomical region. SPET examination of patients with a normal EEG showed fewer hypoperfused areas and a lower degree of asymmetry compared to patients with an abnormal EEG. SPET of patients with focal EEG abnormalities showed more hypoperfused areas (difference not statistically significant) and a higher AI than did SPET of the patients with diffuse EEG abnormalities. Seven of 11 anatomical regions with focal EEG abnormalities. Seven of 11 anatomical regions with focal EEG abnormalities had co-localized hypoperfused areas and in two of these seven no detectable MRI lesions were found. The analysis of SPET and NP manifestations showed that 12 of 20 patients had at least one positive correlation, always involving the areas with the highest AI. In total, 51/88 (58%) hypoperfused areas correlated with the MRI findings and 31/88 (35%) with NP manifestations; for seven of the latter no concurrent MRI lesions were detected in the same anatomical region. It is concluded that SPET study of brain perfusion is a sensitive method for the evaluation of CNS involvement in SLE; furthermore, it is able to reveal disease progression and the lesions most relevant at the time of evaluation, and can objectify those NP manifestations without detectable MRI abnormalities. Nevertheless, because of the sensitivity of MRI in detecting morphological lesions, a complete evaluation of CNS involvement should be performed, combining SPET with MRI.     

Scintigraphic aspect of infantile cortical hyperostosis (Caffey's disease)

Two patients with infantile cortical hyperostosis (Caffey's disease) are presented in whom radionuclide imaging with 99mTc-MDP and 67Gallium-citrate was performed to eliminate multifocal osteomyelitis as a diagnosis. The scintigraphic appearance of this relatively uncommon disease of children was similar to that obtained in multifocal osteomyelitis; all osseous lesions showed a marked uptake of both radiotracers. However, the distribution of abnormalities (mandible, scapulae) and the degree of extension (mainly diaphyseal) of the lesions are important characteristics in the scintigraphic differential diagnosis but bone radiographs are best used in making the diagnosis.     

Comparison of MR imaging with PET and ictal SPECT in 118 patients with intractable epilepsy.

BACKGROUND AND PURPOSE: MR imaging, PET, and ictal SPECT have been studied extensively as individual techniques in the localization of epileptogenic foci, but only a few comparative studies have been done. We evaluated the concordance rates of ictal video/EEG, MR imaging, PET, and ictal SPECT to compare the sensitivities of these imaging methods in the lateralization of epileptogenic foci. METHODS: The study included 118 consecutive patients who underwent surgery for medically intractable epilepsy and who were followed up for 12 months or more. MR imaging was compared retrospectively with ictal video/EEG, FDG-PET, ictal 99mTc-HMPAO SPECT, and invasive EEG as to their ability to localize the epileptogenic focus; the pathologic findings served as the standard of reference. RESULTS: MR imaging was concordant with video/EEG, PET, and ictal SPECT in 58%, 68%, and 58% of patients, respectively. With the pathologic diagnosis as the standard of reference, MR imaging, PET, and ictal SPECT correctly lateralized the lesion in 72%, 85%, and 73% of patients, respectively. Of the patients with good outcomes, MR imaging, PET, and ictal SPECT were correct in 77%, 86%, and 78%, respectively. In the good outcome group, MR imaging was concordant with PET and ictal SPECT in 73% and 62% of patients, respectively. Of 45 patients who underwent invasive EEG, MR imaging was concordant with the invasive study in 47%; PET in 58%; and ictal SPECT in 56%. Of 26 patients with normal MR findings, PET and ictal SPECT correctly lateralized the lesion in 80% and 55%, respectively. CONCLUSION: Overall concordance among the techniques is approximately two thirds or less in lateralizing epileptogenic foci. PET is the most sensitive, even though it provides a broad approximate nature of the epileptogenic zone, which is not adequate for precise surgical localization of epilepsy. PET and/or ictal SPECT may be used as complementary tools in cases of inconclusive lateralization with ictal video/EEG and MR imaging.     

Comparison of a conventional cardiac-triggered dual spin-echo and a fast STIR sequence in detection of spinal cord lesions in multiple sclerosis

The current optimal imaging protocol in spinal cord MR imaging in patients with multiple sclerosis includes a long TR conventional spin-echo (CSE) sequence, requiring long acquisition times. Using short tau inversion recovery fast spin-echo (fast STIR) sequences both acquisition time can be shortened and sensitivity in the detection of multiple sclerosis (MS) abnormalities can be increased. This study compares both sequences for the potential to detect both focal and diffuse spinal abnormalities. Spinal cords of 5 volunteers and 20 MS patients were studied at 1.0 T. Magnetic resonance imaging included cardiac-gated sagittal dual-echo CSE and a cardiac-gated fast STIR sequence. Images were scored regarding number, size, and location of focal lesions, diffuse abnormalities and presence/hindrance of artifacts by two experienced radiologists. Examinations were scored as being definitely normal, indeterminate, or definitely abnormal. Interobserver agreement regarding focal lesions was higher for CSE (ϰ = 0.67) than for fast STIR (ϰ = 0.57) but did not differ significantly. Of all focal lesions scored in consensus, 47 % were scored on both sequences, 31 % were only detected by fast STIR, and 22 % only by dual-echo CSE (n. s.). Interobserver agreement for diffuse abnormalities was lower with fast STIR (ϰ = 0.48) than dual-echo CSE (ϰ = 0.65; n. s.). After consensus, fast STIR showed in 10 patients diffuse abnormalities and dual-echo CSE in 3. After consensus, in 19 of 20 patients dual-echo CSE scans were considered as definitely abnormal compared with 17 for fast STIR. The fast STIR sequence is a useful adjunct to dual-echo CSE in detecting focal abnormalities and is helpful in detecting diffuse MS abnormalities in the spinal cord. Due to the frequent occurrence of artifacts and the lower observer concordance, fast STIR cannot be used alone. Received: 9 September 1999; Revised: 14 December 1999; Accepted: 16 December 1999     

Comparative analysis of MR imaging, positron emission tomography, and ictal single-photon emission CT in patients with neocortical epilepsy

BACKGROUND AND PURPOSE: MR imaging, positron emission tomography (PET), and single-photon emission CT (SPECT) play important roles in presurgical localization of epileptic foci. However, comparative study of these imaging methods for cases of neocortical epilepsy has been limited. The purpose of this study was to compare the sensitivities of these three imaging methods for presurgical localization of neocortical epileptogenic foci. METHODS: We studied 117 consecutive patients who underwent surgery for intractable neocortical epilepsy. The pathologic substrates were neuronal migration disorder (n = 77), tumor (n = 15), and others (n = 25). MR imaging was compared retrospectively with (18)F-fluorodeoxyglucose PET and ictal technetium-99m hexamethylpropyleneamine oxime SPECT regarding their capability to correctly localize the epileptogenic foci. The pathologic findings were used as the standard of reference. RESULTS: Overall, MR imaging, PET, and ictal SPECT correctly localized the lesions for 59.8%, 77.7%, and 70.3% of the patients, respectively, with a 38% concordance rate among the three methods. PET was most sensitive (71-100%) in detecting all substrates. MR imaging was as sensitive (100%) as PET in detecting tumor but was least sensitive (48.1%) in detecting neuronal migration disorder. Ictal SPECT was more sensitive (75.8%) than MR imaging in detecting neuronal migration disorder. Patients with imaging abnormalities achieved good outcomes in 81.4% of the cases, in contrast to 59.5% for those without imaging abnormalities (P <.05). CONCLUSION: PET and ictal SPECT were overall more sensitive than was MR imaging, despite the low concordance rate and variable sensitivity depending on substrates. The detection of abnormalities by MR imaging was associated with good outcome. PET or ictal SPECT can be well used as complementary tools, particularly in cases of negative MR imaging findings.     

Neurologic,MR imaging,and MR spectroscopic findings in eosinophilia myalgia syndrome.

BACKGROUND AND PURPOSEEosinophilia myalgia syndrome (EMS), a multisystemic disease induced by exposure to L-tryptophan, may result in serious CNS abnormalities. The purpose of this study was to determine the pattern of neurologic characteristics, MR imaging abnormalities, and brain neurometabolites in EMS.METHODSSixteen patients with EMS and CNS abnormalities (CNS-EMS) and 12 control subjects underwent evaluation, including medical and neurologic examination, proton MR spectroscopy, and MR imaging.RESULTSNeurologic findings that were increased in CNS-EMS included minor depression (100%), amnesia (88%), and intermittent confusion (38%), although fatigue (31%), motor disorders (31%), recurrent headache (19%), major depression (13%), and dementia (6%) also occurred, but at a lesser significance. Self-reported disability was markedly increased in CNS-EMS. MR imaging findings included subcortical focal lesions, focal lesions in deep white matter, cortical atrophy, ventricular dilatation, and diffuse and periventricular white matter abnormalities. MR spectroscopic findings established two distinct spectral patterns: 1) increased choline-containing compounds, decreased N-acetylaspartate, and increased lipid-macromolecules, consistent with inflammatory cerebrovascular disease; and 2) increased glutamine, decreased myo-inositol, and decreased choline, consistent with acute CNS injury or metabolic encephalopathy.CONCLUSIONNeurologic abnormalities, self-reported disability, brain lesions, and MR spectroscopic abnormalities are common in CNS-EMS. The pattern of cerebral lesions and neurometabolites is consistent with widespread inflammatory cerebrovascular disease. However, a subgroup of patients with CNS-EMS have neurometabolic changes consistent with a metabolic encephalopathy identical or similar to hepatic encephalopathy. The neurologic abnormalities in EMS and related hypereosinophilic syndromes should be interpreted cautiously, with the recognition that both cerebrovascular injury and secondary metabolic encephalopathies may be involved.     

Renal sonography in American Burkitt lymphoma

Renal involvement is a common finding at necropsy in patients with American Burkitt lymphoma, but its in vivo sonographic features have received little attention in the literature. Of 29 patients with American Burkitt lymphoma who underwent sonography, 10 were found to have renal involvement. The 10 patients demonstrated a range of abnormalities, notably renomegaly (nine patients), diffuse increase in cortical echogenicity (six), and focal renal masses (three). The focal infiltrations were, unexplicably, hypoechoic in two patients and hyperechoic in one. Hydronephrosis was seen in five patients. One patient had evidence of calcium phosphate renal stones. Response to therapy can be assessed by changes in renal size and cortical echogenicity, as well as disappearance of focal lesions.     

Renal neoplasms amenable to partial nephrectomy: MR imaging.

PURPOSE: To determine the magnetic resonance (MR) imaging characteristics of renal lesions in patients who undergo technically successful partial nephrectomy. MATERIALS AND METHODS: Between February 1991 and September 1997, 38 patients (41 lesions) who underwent partial nephrectomy at a single institution were preoperatively evaluated with contrast material-enhanced, multiplanar, surface-coil MR imaging. Imaging findings that could affect the decision to perform partial nephrectomy were retrospectively evaluated: tumor size; tumor location; presence of pseudocapsule; suspected tumor invasion of renal sinus fat, renal collecting system, renal vein, or perinephric fat; and morphologic and physiologic status of the contralateral kidney. Correlation was made with surgical and pathologic findings. RESULTS: Thirty-three of 41 lesions (80%) were renal cell carcinomas, five were oncocytic neoplasms (12%), two were hemorrhagic cysts (5%), and one was an angiomyolipoma (2%). Twenty-four of 41 (59%) lesions had pseudocapsules. In most cases, the perinephric fat (n = 38 [93%]), the renal sinus fat (n = 31 [76%]), and the renal collecting system (n = 39 [95%]) were correctly interpreted as being uninvolved by tumor. CONCLUSION: Renal neoplasms amenable to partial nephrectomy can be identified and characterized with contrast-enhanced, multiplanar, surface-coil MR imaging.     

Magnetoencephalographically directed review of high-spatial-resolution surface-coil MR images improves lesion detection in patients with extratemporal epilepsy

PURPOSE: To determine whether (a) interictal magnetoencephalographic (MEG) epileptiform activity corresponds to anatomic abnormalities at magnetic resonance (MR) imaging, (b) high-spatial-resolution MR imaging depicts lesions in regions without MEG spike activity, (c) MEG-directed review of high-spatial-resolution MR images enables detection of abnormalities not apparent on conventional MR images, and (d) MEG information results in a greater number of diagnosed lesions at re-review of conventional MR images. MATERIALS AND METHODS: Twenty patients with neocortical epilepsy were evaluated with MEG, conventional brain MR imaging with a head coil, and high-spatial-resolution MR imaging with either a surface coil (n = 17) or a high-spatial-resolution birdcage coil (n = 3). Abnormal MEG foci were compared with corresponding anatomic areas on conventional and high-spatial-resolution MR images to determine the presence (concordance) or absence (discordance) of anatomic lesions corresponding to foci of abnormal MEG activity. RESULTS: Forty-four epileptiform MEG foci were identified. Twelve foci (27%) were concordant with an anatomic abnormality at high-spatial-resolution MR imaging, and 32 foci (73%) were discordant. Results of high-spatial-resolution MR imaging were normal in eight patients, and 23 lesions were detected in the remaining 12 patients. Twelve lesions (52%) were concordant with abnormal MEG epileptiform activity, and 11 (48%) were discordant (ie, there was normal MEG activity in the region of the anatomic abnormality). At retrospective reevaluation of conventional MR images with MEG guidance, four occult gray matter migration lesions that had initially been missed were observed. An additional patient with MEG-concordant postoperative gliosis was readily identified with high-spatial-resolution MR images but not with conventional MR images. CONCLUSION: Review of MEG-localized epileptiform areas on high-spatial-resolution MR images enables detection of epileptogenic neocortical lesions, some of which are occult on conventional MR images.     

Reversible signal abnormalities in the hippocampus and neocortex after prolonged seizures.

PURPOSETo investigate the phenomenon of reversible increased signal intensity of medial temporal lobe structures and cerebral neocortex seen on MR images of six patients with recent prolonged seizure activity.METHODSAfter excluding patients with known causes of reversible signal abnormalities (such as hypertensive encephalopathy), we retrospectively reviewed the clinical findings and MR studies of six patients whose MR studies showed reversible signal abnormalities. MR pulse sequences included T2-weighted spin-echo coronal views or conventional short-tau inversion-recovery coronal images of the temporal lobes.RESULTSAll six MR studies showed increased signal intensity within the medial temporal lobe, including the hippocampus in five studies. All follow-up MR examinations showed partial or complete resolution of the hyperintensity within the medial temporal lobe and the neocortex. In one patient, results of a brain biopsy revealed severe cerebral cortical gliosis. Temporal lobectomy performed 4 years later showed moderate cortical gliosis and nonspecific hippocampal cell loss and gliosis.CONCLUSIONSignificant hyperintensity within the temporal lobe is demonstrable on MR images after prolonged seizure activity, suggestive of seizure-induced edema or gliosis. Damage to medial temporal lobe structures by prolonged seizure activity indicates a possible mechanism of epileptogenic disorders.     

Focal neuronal loss, reversible subcortical focal T2 hypointensity in seizures with a nonketotic hyperglycemic hyperosmolar state

Introduction Neuroimaging in seizures associated with nonketotic hyperglycemia (NKH) is considered normal. We report magnetic resonance imaging (MRI) abnormalities in four patients with NKH and seizures. Methods We prospectively evaluated clinical and radiological abnormalities in four patients with NKH during the period March 2004 to December 2005. Results All patients presented with seizures, either simple or complex partial seizures or epilepsia partialis continua. Two of them had transient hemianopia. MRI showed subcortical T2 hypointensity in the occipital white matter and in or around the central sulcus (two patients each), T2 hyperintensity of the overlying cortex (two patients), focal overlying cortical enhancement (three patients) and bilateral striatal hyperintensity (one patient). Diffusion-weighted imaging (DWI) performed in three patients showed restricted diffusion. The ictal semiology and electroencephalographic (EEG) findings correlated with the MRI abnormalities. On clinical recovery, the subcortical T2 hypointensity and striatal hyperintensity reversed in all patients. The initial cortical change evolved to FLAIR hyperintensity suggestive of focal cortical gliosis. The radiological differential diagnosis considered initially included encephalitis, malignancy and hemorrhagic infarct rendering a diagnostic dilemma. Conclusion We identified subcortical T2 hypointensity rather than hyperintensity as a characteristic feature of seizures associated with NKH. Only very few similar reports exist in literature. Reversible bilateral striatal T2 hyperintensity in NKH has not been reported to the best of our knowledge.