Pharmacokinetics and systemic effect on calcium homeostasis of 1 alpha,24-dihydroxyvitamin D2 in rats. Comparison with 1 alpha,25-dihydroxyvitamin D2, calcitriol, and calcipotriol

The purpose of this study was to compare 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET), hippocampal volumetry (HV), T2 relaxometry, and proton magnetic resonance spectroscopic imaging (1H-MRSI) in the presurgical neuroimaging lateralization of patients with nonlesional, electroencephalogram (EEG)-defined unilateral temporal lobe epilepsy (TLE). Twenty-five patients were prospectively studied, along with age-matched controls. T2 relaxometry examinations were performed in 13 patients. Comparison of FDG-PET, HV, and 1H-MRSI was possible in 23 patients. FDG-PET lateralized 87% of patients, HV 65%, N-acetyl aspartate (NAA)/(choline [Cho] + creatine [Cr]) 61%, and [NAA] 57%. Combined HV and NAA/(Cho + Cr) results lateralized 83% of the patients, a value similar to PET. Of 10 patients with normal magnetic resonance imaging (MRI) scans, 2 were lateralized with HV, 6 with FDG-PET, 4 with NAA/(Cho + Cr), and 3 with [NAA]. T2 relaxometry lateralized no patients without hippocampal atrophy. Bilateral abnormality was present in 29 to 33% of patients with 1H-MRSI measures and 17% with HV. Only hippocampal atrophy correlated with postoperative seizure-free outcome. FDG-PET remains the most sensitive imaging method to correlate with EEG-lateralized TLE. Both FDG-PET and 1H-MRSI can lateralize patients with normal MRI, but only the presence of relative unilateral hippocampal atrophy is predictive of seizure-free outcome. Bilaterally abnormal MRI and 1H-MRSI measures do not preclude good surgical outcome.     

Clinical correlations with hippocampal atrophy

There is now a consensus that magnetic resonance imaging (MRI) is a sensitive and specific indicator of mesial temporal sclerosis (MTS) in patients with partial epilepsy. MTS is the most common pathological finding underlying the epileptogenic zone in patients undergoing temporal lobe surgery for medically refractory partial seizures. MRI-based hippocampal volumetric studies (i.e., quantitative MRI), has been shown to provide objective evidence for hippocampal atrophy in patients with MTS. The hippocampal volume in the epileptic temporal lobe has correlated with the neuronal cell densities in selected hippocampal subfields. A history of febrile seizures in childhood and age of unprovoked seizure onset have been associated with MRI-based hippocampal volumetry. There is conflicting evidence regarding the relationship between the duration of the seizure disorder and volumetry. Quantitative MRI has compared favorably to other noninvasive techniques (e.g., scalp-recorded EEG), in indicating the diagnosis of medical temporal lobe epilepsy (MTLE). MRI-identified hippocampal atrophy has also been a favorable prognostic indicator of seizure outcome after temporal lobe surgery. The presence of hippocampal atrophy appears to serve an in vivo surrogate for the presence of MTS.     

Magnetoencephalography in partial epilepsy: clinical yield and localization accuracy

The goals of this study were to determine (1) the yield of magnetoencephalography (MEG) according to epilepsy type, (2) if MEG spike sources colocalize with focal epileptogenic pathology, and (3) if MEG can identify the epileptogenic zone when scalp ictal electroencephalogram (EEG) or magnetic resonance imaging (MRI) fail to localize it. Twenty-two patients with mesial temporal (10 patients), neocortical temporal (3 patients), and extratemporal lobe epilepsy (9 patients) were studied. A 37-channel biomagnetometer was used for simultaneously recording MEG with EEG. During the typical 2-3-hour MEG recording session, interictal epileptiform activity was observed in 16 of 22 patients. MEG localization yield was greater in patients with neocortical epilepsy (92%) than in those with mesial temporal lobe epilepsy (50%). In 5 of 6 patients with focal epileptogenic pathology, MEG spike sources were colocalized with the lesions. In 11 of 12 patients with nonlocalizing (ambiguous abnormalities or normal) MRI, MEG spike sources were localized in the region of the epileptogenic zone as ultimately defined by all clinical and EEG information (including intracranial EEG). In conclusion, MEG can reliably localize sources of spike discharges in patients with temporal and extratemporal lobe epilepsy. MEG sometimes provides noninvasive localization data that are not otherwise available with MRI or conventional scalp ictal EEG.     

Periventricular nodular heterotopia and intractable temporal lobe epilepsy: poor outcome after temporal lobe resection

We describe 5 women and 5 men with periventricular nodular heterotopia and electroclinical features suggestive of temporal lobe epilepsy, who were surgically treated for control of medically refractory seizures. Magnetic resonance imaging revealed bilateral periventricular nodular heterotopia in 7 of the 10 patients. Because of the lack of clear localization, 6 patients were studied with intracranial depth electrode recordings. Seizures were of hippocampal onset (3 patients), regional temporal lobe onset (2 patients), or occipital-temporal onset (1 patient). Anterior temporal lobectomy was performed in 6 patients; selective amygdalohippocampectomy, in 1; and anterior temporal lobectomy plus resection of the heterotopic tissue, in 3. None of the 9 patients followed for more than 12 months postoperatively were seizure free. Two patients were initially seizure free for approximately 18 months, but then seizures recurred. One patient had a major reduction in seizure frequency at a 39-month follow-up after most of the unilateral heterotopic tissue was included in the temporal resection. Temporal resection did not lead to a long-term favorable outcome in this group of patients with periventricular nodular heterotopia and epileptogenic discharges involving the temporal lobe. This suggests a more widespread disorder with epileptogenic activity possibly originating in or near the heterotopic tissue. The clinical and electrographic features of periventricular nodular heterotopia pointing to temporal lobe origin are misleading and temporal resection does not result in long-term cessation of seizures.     

Regionally specific pattern of neurochemical pathology in schizophrenia as assessed by multislice proton magnetic resonance spectroscopic imaging

OBJECTIVE: Several single-voxel proton magnetic resonance spectroscopy (1H-MRS) studies of patients with schizophrenia have found evidence of reductions of N-acetyl-aspartate (NAA) concentrations in the temporal lobes. Multislice proton magnetic resonance spectroscopy imaging (1H-MRSI) permits simultaneous acquisition and mapping of NAA, choline-containing compounds (CHO), and creatine/phosphocreatine (CRE) signal intensities from multiple whole brain slices consisting of 1.4-ml single-volume elements. We have used 1H-MRSI to assess the regional specificity of previously reported changes of metabolite signal intensities in schizophrenia. Hippocampal volume was also measured to test the relationship between 1H-MRSI findings and tissue volume in this region. METHOD: Ratios of areas under the metabolite peaks of the proton spectra were determined (i.e., NAA/CRE, NAA/CHO, CHO/CRE) for multiple cortical and subcortical regions in 10 inpatients with schizophrenia. RESULTS: Patients showed significant reductions of NAA/CRE and NAA/CHO bilaterally in the hippocampal region and in the dorsolateral prefrontal cortex. There were no significant changes in CHO/CRE or in NAA ratios in any other area sampled. No significant correlation was found between metabolite ratios in the hippocampal region and its volume. CONCLUSIONS: NAA-relative signal intensity reductions in schizophrenia appear to be remarkably localized, involving primarily the hippocampal region and the dorsolateral prefrontal cortex, two regions implicated prominently in the pathophysiology of this disorder.     

Multichannel magnetoencephalography in ablative seizure surgery outside the anteromesial temporal lobe

Magnetoencephalography (MEG) was used to evaluate 40 candidates for seizure surgery thought to have foci outside the anteromesial temporal lobe. Of 29 cases with electrographic data suggesting a convexity focus, MEG spikes were recorded from 28. In 21, MEG and electrographic data were localized to the same area. Invasive studies were, or could have been, avoided in 13 cases based on MEG and other noninvasive data. MEG was not localizing value in 4 orbitofrontal or 7-depth-nonlocalized cases. Seventeen patients with MEG epileptiform data have had postoperative follow-up. Eight of 13 with electrographic and MEG data localized to the same area are seizure free. None of 4 with spatial discordance of MEG electrographic data are seizure free.     

Incidence of lesions described by magnetic resonance imaging in the clarification of focal epilepsy of frontal and temporal origin

AIM: Today, MRI is an integral part of the presurgical evaluation of patients suffering from partial epilepsy. These patients frequently show focal morphological abnormalities with potential epileptogenic character and surgical resection of these lesions is associated with superior postsurgical outcome as to seizure frequency. Apart from easily detectable defects, such as post-traumatic lesions or cerebral infarction, as wide variety of mainly small abnormalities can be detected using MRI. METHODS: In this study, 484 patients suffering from partial epilepsy of temporal or frontal onset were evaluated for the incidence of different lesions in this population. RESULTS: All lesions found were included without evaluating their potential epileptogenicity, which remains to be proven using other procedures (EEG, SPECT, PET, etc.). Involvement of the hippocampal formation was a major finding in temporal lobe epilepsy, which could be detected as sclerosis (T2w-images), atrophy (T2w-TSE or T1w-IR-images) or both (15%). In addition and in declining frequency various tumors (14%), post-traumatic lesion (-5%), and focal cortical dysplasia or other disturbances of cortical integrity (-4%) were found. These lesions are detectable with best contrast on different sequences. As a consequence it is suggested to acquire sequences in 3 dimensions including a T1w-SE, two (coronal and axial) double-echo-SE sequences and similarly two T1w-IR-sequences. The application of contrast media can be restricted to special questions, derived either from the first imaging results or from the patients history. CONCLUSION: Using qualitative data for interpretation, the sensitivity as to the detection of any focal pathology of a recent-generation MRI in this population was 75%, with 79% for temporal lobe epilepsies and 67% for frontal lobe epilepsies. Quantitative measurements of hippocampal volume or signal seem to be able to increase the sensitivity of the method.     

Lateralization of human temporal lobe epilepsy by 31P NMR spectroscopic imaging at 4.1 T

OBJECTIVE: To compare the phosphorous metabolite ratios in the mesial temporal lobe of healthy volunteers (n = 20) with the corresponding ratios in patients with temporal lobe epilepsy (n = 30) using 31P NMR spectroscopic imaging and to lateralize the seizure focus in temporal lobe epilepsy patients using various phosphorous metabolite ratios-phosphocreatine to inorganic phosphate (PCr/Pi), PCr to adenosine triphosphate (PCr/gamma-ATP), and (gamma-ATP/Pi)--and to compare with clinical lateralization results. METHODS: All 31P NMR spectroscopic imaging studies were performed on a high-field, 4.1 T, whole-body NMR spectroscopic imaging system using a 31P/1H double-tuned volume coil. RESULTS: We found an average reduction of 15% in the PCr/Pi and gamma-ATP/Pi ratios compared with the corresponding ratios in healthy volunteers in the entire mesial temporal lobe, and more than a 30% reduction in these two ratios in the anterior region of the epileptogenic mesial temporal lobe. These ratios were also reduced significantly in the ipsilateral lobe when compared with their corresponding values in the contralateral lobe. In patients we lateralized the seizure focus, based on these 31P NMR data, and compared the results with the clinical lateralization. The lateralization based on either the PCr/Pi or the gamma-ATP/Pi ratio yielded a correspondence of 70 to 73% with the final clinical lateralization. In the subgroup of patients (n = 9) that needed intracranial EEG for the presurgical lateralization because of inconclusive results from the noninvasive methods, a 78% correspondence was found with the 31P NMR-based lateralization, whereas MRI provided a correspondence of only 33%, and scalp EEG provided a correspondence of only 56%. CONCLUSIONS: These results suggest the utility of adding the 31P NMR method to the group of noninvasive modalities used for presurgical decision making in temporal lobe epilepsy patients.     

Relationship between anatomic lesions of the temporal lobe and temporal lobe epilepsy

A structural lesion of the brain is a frequent finding in intractable partial epileptic patients. We analyse anatomo-electro-clinical characteristics of 58 patients in which MR showed a lesion inside the temporal lobe. They are 29 males and 29 females with a mean age at surgery of 23.5 +/- 10.7 years (2.6-45.9). The mean epilepsy duration is of 13.4 +/- 8 years (1.3-35.5), with a mean seizure frequency of 28.7 +/- 43.6 per month, with a great inter-individual variability (from 3 per month to 15 a day). The minimum follow-up is 3.5 years. A video-EEG monitoring was performed in 21 cases, while a stereo-EEG investigation was judged mandatory in 26. On the basis of anatomo-electro-clinical correlations and of the results of presurgical investigations, the epileptogenic area was proved to be temporal in 49 cases, temporal but controlateral to the lesion in 1, and at least bilobar in 8 patients.     

Decreased left frontal lobe N-acetylaspartate in schizophrenia

OBJECTIVE: The authors measured N-acetylaspartate (a putative neuronal marker), using in vivo proton magnetic resonance spectroscopic imaging (1H-MRSI), in the frontal lobes of schizophrenic patients and normal subjects. METHOD: Frontal lobe 1H-MRSI was performed bilaterally on 24 medicated schizophrenic patients and 15 healthy comparison subjects. Levels of N-acetylaspartate, creatine, and choline were determined. RESULTS: Relative to the comparison group, the patients with schizophrenia demonstrated significantly lower levels of N-acetylaspartate in the left frontal lobe. There was no association between level of N-acetylaspartate and duration of illness or medication dosage. No differences between groups or lateralized asymmetries in choline or creatine were noted. CONCLUSIONS: This preliminary study provides support for decreased N-acetylaspartate in the left frontal lobe in schizophrenia and neuronal dysfunction in this brain region.     

Single photon emission tomography in temporal epilepsy: interictal and ictal studies with visual and semi quantitative analysis

Single photon emission tomography (SPECT) was performed in 27 patients with refractory complex partial seizures from the temporal lobes due to mesial temporal sclerosis. Independent blinded observers assessed the 28 interictal studies and 9 ictal/postictal studies. Visual analysis of interictal studies detected hypoperfusion in 22, ipsilateral to the epileptogenic zone in 19 (67%) and contralateral in 3 (10.7%). Quantified temporal lobe asymmetry, greater than a previously derived normal range, correctly identified the epileptogenic zone in 16 (61.5%) with false lateralization in 4 (15.3%). In all 9 cases in which they were performed, ictal/postictal studies showed hyperperfusion at the region of epileptic focus. In 3 patients with complex partial seizures followed by symmetric generalized tonic-clonic seizures, hyperperfusion restricted to the temporal lobe was demonstrated. In 5 of these patients the interical studies were unable to demonstrate localized changes. There were no significant correlations between SPECT findings and clinical parameters or EEG slowing in the temporal lobes.     

Malignant lesions presenting as symptoms of craniomandibular dysfunction

We compared the findings of scalp electroencephalogram with subdural electrode array (SEA) recordings in 19 patients with refractory frontal lobe epilepsy. Prolonged scalp interictal recordings localized the epileptogenic zone in 12 patients; seven had no interictal sharp waves. The SEAs showed multifocal interictal sharp waves in all patients. Seven patients with localized seizure onset on scalp recording showed extensive ictal onset on the SEA recording. Five patients with lateralized seizure onset to one hemisphere on scalp recording were found to have ictal onset on SEA restricted to a smaller area. Because of the large epileptogenic zone found on SEA recordings, a complete resection was possible in only five (33%) of the 15 patients who had resections. Eight (53%) of the 15 patients benefited from surgery (mean follow-up, 4.6 years). The SEAs also allowed functional localization in most patients. From these data, we suggest that a localizing scalp electroencephalogram in patients with frontal lobe epilepsy may be misleading because SEA recordings show larger epileptogenic zones than anticipated. Furthermore, we postulate that the larger extensive epileptogenic zone may account for the poorer surgical outcome in patients with frontal lobe epilepsy compared with patients with temporal lobe epilepsy.     

Surgical management of intractable epilepsy in patients with ganglioglioma

Long-standing intractable seizures are common manifestation of cerebral gangliogliomas. There is much controversy regarding the most appropriate surgical treatment (lesionectomy vs resection of the epileptogenic cortex with the lesion) for patients with intractable epilepsy associated with gangliogliomas. We reported 2 cases, in which the favorable seizure outcome was obtained following lesionectomy alone. (Case 1) Nine-year-old female developed attack of abnormal sensation in her left upper limb followed by motor seizure in her left limbs since 5 years old. MRI revealed hyperintense tumor in the right medial frontal lobe. Chronic invasive subdural recording showed that ictal onset zone was located in the hand motor area. Following lesionectomy alone, she became free from seizures. (Case 2) Eight-year-old girl had intractable generalized seizure since 6 years old. MRI revealed a cystic tumor in the right parietal lobe. She had multiple spike foci on electroencephalography and magnetoencephalography, and intraoperative electrocorticography failed to reveal the paroxysm. Following lesionectomy, she had good relief with less than one minor seizure per 1-3 months. Thus, lesionectomy, even without resection of the epileptogenic cortex, may improve seizure outcome in patients with ganglioglioma-associated epilepsy.     

Application of high field spectroscopic imaging in the evaluation of temporal lobe epilepsy

Previous spectroscopic imaging studies of temporal lobe epilepsy have used comparisons of metabolite content or ratios to lateralize the seizure focus. Although highly successful, these studies have shown significant variations within each of the groups of healthy subjects and patients. This variation may arise from the natural differences seen in metabolite concentration in gray and white matter, the complex anatomy seen about the hippocampus, and the large voxels typically employed at 1.5 T. Using a 4.1 T whole body system, we have acquired spectroscopic images with 0.5 cc nominal voxels (1 cc after filtering) to evaluate the regional variation in metabolite content of the hippocampus, temporal gray and white matter, midbrain, and cerebellar vermis. Using a threshold value of 0.90 for CR/NAA, a value 90% of all normal hippocampal voxels lay below, we have correctly identified the presence of epileptogenic tissue in patients with unilateral as well as bilateral seizures. By using comparisons to healthy values of the CR/NAA ratio, this method enables the visualization of bilateral disease and provides information on the extent of gray matter involvement.     

Severe amnesia: an usual late complication after temporal lobectomy

A patient developed the severe amnesic syndrome 8 years after temporal lobe surgery for epilepsy. He underwent left temporal lobectomy (6 cm, 43.5 g; hippocampal sclerosis) aged 19, and remained seizure free for 8 years until a convulsion followed a head injury. He became severely amnesic after a fourth convulsion 16 months later. He was right-handed, pre-operative IQ was average, verbal memory poor and non-verbal memory normal. Post-operatively, these were unchanged. After the first post-operative seizure he began professional training. After onset of amnesia IQ was unchanged, anterograde memory severely impaired and retrograde amnesia dense for at least 16 months. He died 2 years later. Magnetic resonance imaging before amnesia showed absence of anterior left temporal lobe, atrophy of left fornix and mamillary body, and normal right temporal lobe. Four months after onset of amnesia, right hippocampal volume had reduced by 36%. Autopsy showed: previous left temporal lobectomy with absence of left amygdala and hippocampus, atrophy of fornix and mamillary body; neuronal loss in the right hippocampus, severe in CA1 and CA4; intact right amygdala and parahippocampal gyrus; recent diffuse damage associated with cause of death. A convulsion can cause severe hippocampal damage in adult life. Hippocampal zones CA1 and/or CA4 are critical for maintaining memory and the amygdala and parahippocampal gyrus cortex alone cannot support acquisition of new memories.     

Reversible signal abnormalities in the hippocampus and neocortex after prolonged seizures

PURPOSE: To 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. METHODS: After 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. RESULTS: All 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. CONCLUSION: Significant 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.     

Cortical and hippocampal volume deficits in temporal lobe epilepsy

PURPOSE: To use quantitative magnetic resonance imaging (MRI) methods to examine the extent of volume abnormalities in the hippocampus and in extrahippocampal brain regions in localization-related epilepsy of temporal lobe origin (TLE). METHODS: Hippocampal, temporal lobe, and extratemporal lobe volumes were examined with 3-mm spin-echo coronal MRI scans in patients with unilateral TLE who were candidates for temporal lobe resection. Measures were adjusted for normal variation due to intracranial volume and age based on 72 healthy male controls. Group differences between 14 male TLE [7 left TLE (LTLE), 7 right TLE (RTLE)] patients and a subset of 49 age range-matched controls were examined with analysis of variance (ANOVA). RESULTS: As compared with controls, patients with TLE had smaller temporal lobe and frontoparietal region gray matter volumes, bilaterally, smaller temporal lobe white matter volumes bilaterally, and larger ventricular volumes. In contrast to these bilateral tissue volume deficits, hippocampal volume deficits in TLE were ipsilateral to the epileptogenic temporal lobe. CONCLUSIONS: Extrahippocampal volume abnormalities were bilateral and occurred in both temporal and extra-temporal cortical regions in TLE, whereas hippocampal deficits were related to the side of the epileptogenic focus. These data suggest that brain abnormalities in TLE are not limited to the epileptogenic region.     

Routine microbiological testing in sudden and unexpected infant death

We reviewed 187 depth recorded seizures in 33 patients with non-lesional temporal lobe complex partial seizures. All patients had a minimum of 1 year follow-up following temporal lobectomy. We classified seizure onset pattern as rhythmic activity, attenuation, or repetitive spikes or spike wave complexes. The most common pattern of seizure onset was rhythmic activity and the next most common pattern was repetitive spikes. Seventy-five seizures (49%) had only one seizure onset pattern, and 79 seizures (51%) had a combination of seizure onset patterns. The degree of hippocampal gliosis strongly predicted the type of seizure onset pattern (Chi square = 24.07, 2 d.f., P < 0.01). The rhythmic activity pattern was associated with mild gliosis, and the repetitive spike pattern was associated with severe gliosis. We classified seizure onset as focal or regional based on the number of electrode contacts that were involved by the ictal EEG. A focal seizure onset was associated with an excellent outcome following temporal lobectomy.     

EEG findings in frontal lobe epilepsies

As a group, epilepsies of frontal lobe origin are thought to be poorly localized using surface EEG recordings. This finding may depend on the specific areas of frontal lobe from which the seizures originate or the pathologic substrate. We reviewed the presurgical surface EEGs of patients with frontal lobe epilepsy who underwent epilepsy surgery. The specific area of the frontal lobe where seizures originated was determined by 1) intracranial ictal EEG recordings, or 2) the presence of a structural lesion, identified by imaging studies in patients who achieved complete seizure control following surgery. We differentiated patients whose seizures began in the dorsolateral frontal convexity from those whose seizures began in the medial frontal region, and we correlated EEG findings in the interictal, postictal, and ictal states with seizure semiology, pathologic substrate, and surgical outcome. Four of nine patients had seizures originating in the dorsolateral frontal convexity and five had medial frontal onset seizures. Patients whose seizures originated from the dorsolateral convexity had focal interictal epileptiform abnormalities that localized to the region of seizure onset. Patients whose seizures began in the medial frontal region had either no interictal epileptiform abnormality or had multifocal epileptiform discharges. Patients whose seizures began in the dorsolateral convexity showed focal electrographic seizure activity that was localizing. This rhythmic fast activity did not appear to be substrate-specific. Patients whose seizure onset localized to the medial frontal region did not show focal electrographic seizure at clinical onset. We conclude that the scalp EEG recordings of frontal lobe epilepsies contain features that enable differentiation of seizures originating from two different regions of the frontal lobe.     

A genetic propensity to high factor VII is not associated with the risk of myocardial infarction in men

Interictal brain SPECT is useful for the localization of a seizure focus. Concomitant hypoperfusion of the ipsilateral thalamus on interictal SPECT has been noted for temporal lobe epilepsy. In this study, we aimed to evaluate the prevalence of thalamic hypoperfusion ipsilateral to temporal hypoperfusion (ipsilateral thalamic hypoperfusion) and to assess the usefulness of this finding for the lateralization of epileptic foci on interictal SPECT for temporal lobe epilepsy patients. METHODS: Forty-six patients with refractory temporal lobe epilepsy underwent interictal brain SPECT after intravenous injection of 555-740 MBq of 99mTc-ECD. Perfusion impairments in the brain, especially the temporal lobe and thalamus, were evaluated. The localization of seizure foci was determined in conjunction with scalp, ictal and cortical electroencephalography, MRI and clinical outcomes. Ictal SPECT was performed for 5 of the 12 patients. RESULTS: Concomitant decreased perfusion in both the temporal lobe and the ipsilateral thalamus was observed for 12 (26%) of 46 temporal lobe epilepsy patients on interictal brain SPECT. Seven patients showed hypoperfusion in the left temporal lobe and ipsilateral thalamus. Five patients showed hypoperfusion in the right temporal lobe and ipsilateral thalamus. In addition, hypoperfusion in the ipsilateral basal ganglia (ten patients) or contralateral cerebellum (four patients) was observed. CONCLUSION: Ipsilateral thalamic hypoperfusion is not uncommon in temporal lobe epilepsy. The exact mechanism causing ipsilateral thalamic hypoperfusion is uncertain; however, corticothalamic diaschisis may be an important factor. This finding may aid in the lateralization of seizure foci on interictal brain SPECT.