MR imaging in patients with intractable complex partial epileptic seizures

Detailed neurologic studies, high-field-strength MR imaging, and CT scanning were performed preoperatively in 53 patients with intractable complex partial seizures who underwent surgical treatment for epilepsy. Macroscopic structural (tumoral or vascular) lesions were found in 28% of patients. The remainder had pathologic findings consistent with mesial temporal gliosis. Tumors were found in 22% of the patients and were benign or of low-grade malignancy in every case. MR was accurate in the preoperative diagnosis of structural lesions, including very small occult tumors and cryptic vascular malformations. In patients with mesial temporal gliosis, there was correlation between the MR observation of a unilaterally dilated anterior temporal horn and the EEG-identified seizure focus and side of temporal lobectomy. However, MR demonstrated T2-weighted signal abnormalities correlating with the epileptogenic focus in only 8% of cases of mesial temporal gliosis. MR provided useful information in 28% of patients who underwent surgery for refractory complex partial epilepsy. MR obviated invasive EEG monitoring in 93% of the patients with structural lesions. MR was useful in only 8% of the patients with pathologic changes of mesial temporal gliosis.     

MR imaging in patients with temporal lobe seizures: correlation of results with pathologic findings

Thirty-nine consecutive patients with medically intractable complex partial seizures were studied with electroencephalography and MR imaging to localize an epileptogenic focus for temporal lobectomy. The patients were divided into three groups on the basis of pathologic findings after lobectomy: Group 1 comprised 13 patients with neoplasms, hamartomas, or cysts; group 2 comprised 13 patients with moderate and severe mesial temporal sclerosis (one patient was included in both groups 1 and 2); and group 3 comprised 14 patients who underwent aspiration lobectomy, which yielded limited tissue for pathologic study so no pathologic diagnosis was made. The majority of the patients in group 3 were assumed to have mesial temporal sclerosis. Abnormal MR signal in the temporal lobe on T2-weighted images was graded as minimal increase (1+), intermediate or moderate increase (2+), and very significant increase (3+). An abnormal signal was demonstrated in 26 (67%) of the 39 patients. In group 1, the tumor/cyst subgroup, an abnormal signal was seen in all 13 patients. Most had 3+ signal. There was increased signal in eight (62%) of 13 patients in group 2 and in six (43%) of 14 patients in group 3. This study suggests that MR can detect almost all tumors and a significant number of mesial temporal sclerosis lesions in individuals with complex partial seizures. On the basis of this small series, individuals who exhibit significant signal (3+) can be expected to have neoplasms, hamartomas, or cysts, and patients who exhibit minimal signal (1+) will usually have mesial temporal sclerosis.     

MR imaging in patients with temporal lobe seizures: correlation of results with pathologic findings

Thirty-nine consecutive patients with medically intractable complex partial seizures were studied with electroencephalography and MR imaging to localize an epileptogenic focus for temporal lobectomy. The patients were divided into three groups on the basis of pathologic findings after lobectomy: Group 1 comprised 13 patients with neoplasms, hamartomas, or cysts; group 2 comprised 13 patients with moderate and severe mesial temporal sclerosis (one patient was included in both groups 1 and 2); and group 3 comprised 14 patients who underwent aspiration lobectomy, which yielded limited tissue for pathologic study so no pathologic diagnosis was made. The majority of the patients in group 3 were assumed to have mesial temporal sclerosis. Abnormal MR signal in the temporal lobe on T2-weighted images was graded as minimal increase (1+), intermediate or moderate increase (2+), and very significant increase (3+). An abnormal signal was demonstrated in 26 (67%) of the 39 patients. In group 1, the tumor/cyst subgroup, an abnormal signal was seen in all 13 patients. Most had 3+ signal. There was increased signal in eight (62%) of 13 patients in group 2 and in six (43%) of 14 patients in group 3. This study suggests that MR can detect almost all tumors and a significant number of mesial temporal sclerosis lesions in individuals with complex partial seizures. On the basis of this small series, individuals who exhibit significant signal (3+) can be expected to have neoplasms, hamartomas, or cysts, and patients who exhibit minimal signal (1+) will usually have mesial temporal sclerosis.     

Cryptic structural lesions in refractory partial epilepsy: MR imaging and CT studies

Results of contrast material-enhanced computed tomography (CT) and T2-weighted spin-echo magnetic resonance (MR) imaging were correlated with pathologic findings in 25 patients treated surgically for refractory partial epilepsy. Of 12 lesions present, ten (83%) were detected by MR imaging and seven (58%) by CT scanning. Of nine low-grade gliomas, eight were detected by MR imaging and four by CT scanning. One posttraumatic scar and one case of temporal lobe atrophy were better demonstrated by MR imaging. A small, thrombosed arteriovenous malformation was the only lesion detected by CT scanning but not by MR imaging. No lesions were detected in 13 patients with mild gliosis and one patient with a 1.2-cm grade 1 astrocytoma. Although more sensitive than CT for detection of structural lesions in patients with refractory partial epilepsy, MR imaging resulted in a 25% false-negative diagnostic rate when a repetition time of 2,000 msec and echo time of 60 msec were used. Multi-echo imaging with at least one long echo time may be needed to increase the sensitivity of MR imaging in these patients.     

MR contribution in surgery of epilepsy

The contribution of MR imaging in patients with drug-resistant epilepsy considered for surgical therapy is discussed. In this review we focus on: (a) focal abnormalities (mesial temporal sclerosis, focal migration disorders, hamartomatous lesions and low-grade tumours, phakomatosis and vascular malformations) associated with therapy-resistant partial epilepsy, requiring resective surgery; (b) abnormalities leading to generalized seizures that require more drastic surgical procedures, such as callosotomy and functional hemispherectomy; and (c) localisation of implanted depth-electrodes. Received: 6 April 1998; Revision received: 2 June 1998; Accepted: 3 June 1998     

MR in temporal lobe epilepsy: analysis with pathologic confirmation.

PURPOSEWe evaluated the MR findings in patients with temporal lobe epilepsy to determine the predictive value of MR imaging in assessing patient outcome.METHODSMR studies from 186 of 274 consecutive patients who underwent temporal lobectomy for intractable epilepsy were reviewed retrospectively. Images were interpreted by an experienced neuroradiologist, who was blinded to the side of seizure activity and to pathologic findings.RESULTSMR imaging exhibited 93% sensitivity and 83% specificity in detecting hippocampal/amygdalar abnormalities (n = 121), and 97% sensitivity and 97% specificity in detecting abnormalities in the rest of the temporal lobe (n = 60). Abnormal high signal of the hippocampus on T2-weighted images had a sensitivity of 93% and specificity of 74% in predicting mesial temporal sclerosis (n = 115). The presence of hippocampal atrophy on MR correlated with the duration of seizures. Sensitivity and specificity of MR imaging in detecting temporal lobe tumors (n = 42) were 83% and 97%, respectively, based on abnormal signal and mass effect. After surgery, 63% of patients were seizure free and 28% had a significant reduction of seizure frequency at an average of 24 months (range, 12 to 78 months) after surgery. Patients with a single lesion in the anterior temporal lobe or hippocampus/amygdala had a better outcome than patients with multiple lesions (n = 22). Interrater agreement varied from 0.4 to 0.93, with best agreement for tumors or abnormal hippocampal signal on T2-weighted images.CONCLUSIONMR imaging is highly sensitive in detecting and locating abnormalities in the temporal lobe and the hippocampus/amygdala in patients with temporal lobe epilepsy. Hippocampal atrophy appears to correspond to the duration of seizure disorder.     

Detection of mesial temporal lobe hypoperfusion in patients with temporal lobe epilepsy by use of arterial spin labeled perfusion MR imaging

BACKGROUND AND PURPOSE: Interictal hypometabolism has lateralizing value in cases of temporal lobe epilepsy and positive predictive value for seizure-free outcome after surgery to treat epilepsy. Alterations in regional cerebral metabolism can also be inferred from measurements of regional cerebral perfusion. The purpose of this study was to determine the feasibility of detecting cerebral blood flow (CBF) asymmetries in the mesial temporal lobes using continuous arterial spin labeling perfusion MR imaging, which is a noninvasive method for calculating regional CBF. METHODS: Twelve patients with medically refractory temporal lobe epilepsy who underwent preoperative evaluation for temporal lobectomy and 12 normal control participants were studied retrospectively. Absolute and normalized mesial temporal CBF measurements were compared between the patient and control groups. Lateralization based on a perfusion asymmetry index was compared with metabolic ((18)[F]-fluorodeoxyglucose positron emission tomography) and hippocampal volumetric asymmetry indices and with clinical lateralization. RESULTS: Mesial temporal CBF was more asymmetric in patients with temporal lobe epilepsy than in normal control participants, although asymmetric mesial temporal CBF was also found in normal participants, with the left side dominant. Ipsilateral mesial temporal CBF was significantly decreased compared with contralateral mesial temporal CBF in patients with temporal lobe epilepsy. Global CBF measurements were significantly decreased in patients compared with control participants. Asymmetry in mesial temporal blood flow in patients persisted after normalization to global CBF. Lateralization using continuous arterial spin labeling perfusion MR imaging asymmetry index significantly correlated with lateralization based on (18)[F]-fluorodeoxyglucose positron emission tomography hypometabolism, hippocampal volumes, and clinical evaluation. CONCLUSION: Continuous arterial spin labeling perfusion MR imaging can detect interictal asymmetries in mesial temporal lobe perfusion in patients with temporal lobe epilepsy. This technique is readily combined with routine structural assessment and potentially offers an inexpensive and noninvasive means of screening for asymmetries in interictal mesial temporal lobe function.     

Imaging findings in hippocampal sclerosis: correlation with pathology

We evaluated the ability of preoperative radiologic imaging to detect hippocampal sclerosis in 31 patients who underwent surgery for intractable epilepsy. Hippocampal sclerosis is commonly associated with surgically treatable temporal lobe epilepsy. It is pathologically described as neuronal cell loss with associated gliosis in the hippocampus. While previous reports have correlated imaging results with clinical or qualitative histologic findings, this study used quantitative pathologic criteria (neuronal cell density) to diagnosis hippocampal sclerosis. We focused our study on the 11 patients with cryptogenic temporal lobe epilepsy. Of these, nine had hippocampal sclerosis by pathologic criteria. MR findings included unilateral hippocampal atrophy, an increased signal in the hippocampus on long TR scans, and atrophy in the adjacent white matter and temporal lobe. Hippocampal atrophy was most frequently seen in the red nucleus plane on coronal scans, corresponding to the body of the hippocampus. We also compared hippocampal size on MR with neuronal density in surgical specimens of the 11 patients with cryptogenic temporal lobe epilepsy. A statistically significant correlation was found between MR size and neuronal density in CA3 and CA4 of the cornu ammonis and the granular cell layer of the hippocampus. Since temporal lobectomy eliminated seizures in seven of nine patients with hippocampal sclerosis, preoperative diagnosis by MR has important therapeutic consequences.     

MR in temporal lobe epilepsy: early childhood onset versus later onset.

PURPOSETo study the relationship between the MR findings and the clinical features in temporal lobe epilepsy in childhood (less than 10 years of age).METHODSMR studies were performed with a 1.5-T imager on 38 temporal lobe epilepsy patients receiving drug therapy at the psychiatric department. These patients were divided into two groups according to their age at onset (10 years or less, 11 years or more). The two groups were compared in terms of the MR findings and clinical features.RESULTSThe 11 younger-onset patients included 5 with a high-signal area attributed to mesial temporal sclerosis. Clinically, all of these 5 patients had a history of "complex" febrile convulsions, which sharply distinguished them from the older-onset group.CONCLUSIONThe analysis suggests that complex febrile convulsions in infancy can be associated with high-signal areas on MR attributed to mesial temporal sclerosis.     

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.     

Imaging of central nervous system tumors

Magnetic resonance imaging has been used increasingly in the staging and evaluation of neoplasia of the brain and leptomeninges. In the classification of gliomas, the MR accuracy rate approaches that of pathologic diagnosis. Contrast-enhanced MR imaging has improved specificity in evaluating brain tumors in children and is now the preferred modality for evaluating leptomeningeal metastases of the brain and spine. MR imaging in children has also increased the specificity of histologic diagnosis in hypothalamic hamartoma and juvenile pilocytic astrocytoma. Gadolinium enhancement is most useful in patients older than 35 years of age who have focal neurologic complaints and certain disease histories. The expense of gadolinium contrast material is the major drawback to its routine use. In patients with seizure disorder, MR imaging is more sensitive than CT for detecting abnormalities such as mesial temporal sclerosis, tumors, and vascular malformations. Gadolinium enhancement may be useful in differentiating tumors from mesial temporal sclerosis. Recent reports on the use of MR spectroscopy for evaluating brain metabolism and tumors demonstrate that differences in metabolites exist. A correlation was found in epidermoid tumors between high signal on T1-weighted images and high lipid content, and several studies have shown a positive correlation between glioma grade and glycolytic activity as determined on 18F-2-fluoro-2-deoxy-D-glucose positron emission tomography.     

MR imaging evaluation of seizures

It is imperative for a radiologist to determine the type of seizure a patient has prior to magnetic resonance (MR) imaging to optimally provide the clinician with the information he or she requires. Specifically, complex partial seizures require evaluation of the frontal lobes and the hippocampus (for mesial temporal sclerosis). These are best evaluated with fluid-attenuated inversion recovery (FLAIR) imaging; the use of intravenously administered contrast material is not required. Other types of chronic seizures are best evaluated with nonenhanced FLAIR or T2-weighted imaging for low-grade tumors, vascular malformations, gliosis after infarction, inflammation, or trauma. The presence of new-onset seizures in an adult or the worsening of chronic seizures warrants T2-weighted or FLAIR imaging and gadolinium-enhanced T1-weighted imaging (to look for primary or metastatic tumors, infections, or inflammatory lesions). If available, echo-planar diffusion imaging should be used also (to look for acute infarcts).     

Modified CT techniques in the evaluation of temporal lobe epilepsy prior to lobectomy

The outcome of temporal lobectomy performed for seizure control is improved by preoperative identification of structural lesions. We used cranial CT, modified to improve visualization of mesial temporal structures, as a means of preoperative evaluation in 48 patients with partial complex seizures. The axial views, parallel to the temporal fossa, improved visualization of five lesions, including two that were not diagnosed by routine cranial CT. In 12 patients, intrathecal metrizamide was used; the rest received intravenous contrast. These modified techniques could not reliably predict mesial temporal herniation; however, modified axial CT with intravenous contrast is recommended for evaluation of suspected temporal lobe pathology.     

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.     

MR and positron emission tomography in the diagnosis of surgically correctable temporal lobe epilepsy.

PURPOSETo determine the association of an MR abnormality and a positron emission tomography (PET) abnormality with a good outcome in patients with temporal lobe epilepsy after lobectomy, the association of combined PET and MR findings with good outcomes after lobectomy, and MR and PET pathologic correlation.METHODSMR and PET were performed on 27 patients in a blinded study. Histologic studies were correlated with foci of increased T2 signal.RESULTSIncreased signal or decreased volume of the hippocampus was noted in 13 of 15 patients with mesial temporal sclerosis. Twelve of 15 had positive PET findings. MR identified 20 (83%) of the 24 patients with good outcomes. PET identified 71%. When MR and PET were combined, they detected 95% of the patients with good outcome. Region of interest measurements of the hippocampus in 11 study patients and 7 control subjects documented a significant increase in signal in the patients with seizures. Histologic correlative studies demonstrated that increased T2 signals related to astrocytosis in the hippocampus and adjacent white matter.CONCLUSIONSMR (increased signal and decreased volume of the hippocampus) significantly improved the capability to identify those persons who would be helped by lobectomy. MR sensitivity exceeded that of PET.     

18F-FDG PET studies in patients with extratemporal and temporal epilepsy: evaluation of an observer-independent analysis.

The aim of this study was to evaluate an observer-independent analysis of 18F-fluorodeoxyglucose (FDG) PET studies in patients with temporal or extratemporal epilepsy. METHODS: Twenty-seven patients with temporal epilepsy and 22 patients with extratemporal epilepsy were included in the study. All patients with temporal epilepsy and 7 patients with extratemporal epilepsy underwent surgical treatment. In patients who showed significant postoperative improvement (temporal, n = 23; extratemporal, n = 6), the epileptogenic focus was assumed to be located in the area of surgical resection. In extratemporal epilepsy patients who did not undergo surgery, the focus localization was determined using a combination of semiology, ictal and interictal electroencephalography, [99mTc]ethyl cysteinate dimer SPECT, MRI and [11C]flumazenil PET. Visual analysis was performed by two experienced and two less experienced blinded observers using sagittal, axial and coronal images. In the automated analysis after anatomic standardization and generation of three-dimensional stereotactic surface projections (SSPs), a pixelwise comparison of 18F-FDG uptake with an age-matched reference database (n = 20) was performed, resulting in z score images. Pixels with the maximum deviation were detected, summarized and attached to one of 20 predefined surface regions of interest. For comparison with 18F-FDG PET and MR images, three-dimensional overlay images were generated. RESULTS: In patients with temporal epilepsy, the sensitivity was comparable for visual and observer-independent analysis (three-dimensional SSP 86%, experienced observers 86%-90%, less experienced observers 77%-86%). In patients with extratemporal epilepsy, three-dimensional SSP showed a significantly higher sensitivity in detecting the epileptogenic focus (67%) than did visual analysis (experienced 33%-38%, each less experienced 19%). In temporal lobe epilepsy, there was moderate to good agreement between the localization found with three-dimensional SSP and the different observers. In patients with extratemporal epilepsy, there was a high interobserver variability and only a weak agreement between the localization found with three-dimensional SSP and the different observers. Although three-dimensional SSP detected multiple lesions more often than visual analysis, the determination of the highest deviation from the reference database allowed the identification of the epileptogenic focus with a higher accuracy than subjective criteria, especially in extratemporal epilepsy. CONCLUSION: Three-dimensional SSP increases sensitivity and reduces observer variability of the analysis of 18F-FDG PET images in patients with extratemporal epilepsy and is, therefore, a useful tool in the evaluation of this patient group. The benefit of this analytical approach in patients with temporal epilepsy is less apparent.     

Prevalence of asymmetry of mamillary body and fornix size on MR imaging

BACKGROUND AND PURPOSE: Mamillary body and fornix asymmetry are frequent findings on MR imaging of the brain. We sought to determine the prevalence of asymmetry of the fornix and mamillary body on MR imaging in patients with or without seizures.MATERIALS AND METHODS: MR images were retrospectively evaluated for asymmetry of the mamillary body and fornix in 178 patients who had a history of seizures, of whom 35 had suspected mesial temporal sclerosis (MTS). Additionally, 353 patients who had no limbic system pathology were reviewed. All patients were examined with spin-echo MR imaging, consisting of contiguous axial and/or coronal fluid-attenuated inversion recovery (FLAIR), T2-weighted, and sagittal T1-weighted imaging. Additionally, the patients with seizures had oblique coronal 3-mm T2-weighted, FLAIR, and 1.5-mm magnetization-preparation rapid gradient echo scanning through their temporal lobes.RESULTS: In the patients who had no limbic system pathology or seizure history, 6.5% (23/353) had MR imaging evidence of asymmetric mamillary bodies and 7.9% (28/353) had asymmetric fornix size. Asymmetry of the mamillary body and fornix size was found in 37.1% (13/35) and 34.3% (12/35), respectively, of subjects with suggested hippocampal sclerosis. The prevalence of asymmetry of the mamillary body and fornix was statistically significantly higher in the patients with MTS (χ² test, P <.0001).CONCLUSION: Although asymmetry of the mamillary bodies and fornices is highly associated with MTS, this could also be seen as a normal variation or congenital abnormality.

In the examination for the source of seizures, many tools and methods have been used. The greatest consideration has been given to the study of the focal epilepsies. As a diagnostic or research tool for generalized epilepsy, radiologic imaging has not been extremely useful other than to exclude mass lesions. Temporal lobe epilepsy is a relatively well-defined epileptic syndrome with localized electroencephalographic abnormalities, memory dysfunction, and hippocampal atrophy or mesial temporal sclerosis (MTS) on MR imaging.^1–3 MTS is the most common cause of temporal lobe epilepsy found at surgery. Several studies have confirmed that MR imaging is a reliable technique for locating the origin of temporal lobe epilepsy.^4–9 It has been previously suggested that neuronal damage in the hippocampus may cause atrophy of the ipsilateral limbic system as a result of transneuronal degeneration.¹⁰The purpose of this study was to determine the prevalence of asymmetry of the fornix and mamillary body on MR imaging in patients with or without seizures. These structures may be diminished in size in a greater proportion of patients with MTS.^11–13 We hypothesized that asymmetry of the fornix and mamillary body is not only related to MTS but also could be present as a normal variation or other cause of epilepsy.     

Intractable temporal lobe epilepsy: comparison of positron emission tomography with qualitative and quantitative MR.

PURPOSETo compare the ability of qualitative fludeoxyglucose F 18 positron emission tomography (QPET), qualitative MR imaging (QMR), and quantitative MR imaging with hippocampal formation volumetric assessment (HV MR) to lateralize the seizure focus in patients with temporal lobe epilepsy.METHODSSixteen consecutive patients undergoing presurgical examination for temporal lobe seizures had QPET, QMR, and HV MR. The presence of temporal lobe epilepsy was confirmed by Engel class I or II outcomes at 1-year postoperative follow-up examinations. A QPET, QMR, or HV MR study was considered to be lateralizing if it matched the side of the seizure focus, nonlateralizing if it did not lateralize the seizure focus to either temporal lobe, or incorrectly lateralizing if it lateralized the seizure focus to the incorrect side.RESULTSOf 16 patients with proved temporal lobe seizures, QPET was correctly lateralizing in nine (56%), nonlateralizing in six (37.5%), and incorrectly lateralizing in one (6%). QMR was correctly lateralizing in six (37.5%), nonlateralizing in six (37.5%), and incorrectly lateralizing in four (25%). HV MR was correctly lateralizing in all 16 patients (100%). Age at onset, seizure duration, and total number of seizures did not correlate with QPET, QMR, and HV MR lateralization.CONCLUSIONSOur results show that each imaging technique yields useful information for seizure lateralization in temporal lobe epilepsy and that HV MR yields considerably more information that QPET or QMR.     

Brain damage from perinatal asphyxia: correlation of MR findings with gestational age

MR scans of 25 patients who suffered asphyxia at known gestational ages were reviewed retrospectively. The gestational ages of the patients at the time of asphyxia ranged from 24 to 46 weeks. The MR pattern of brain damage in patients with prolonged partial asphyxia was seen to evolve in a predictable manner corresponding to the known maturation of the brain and its vascular supply. Patients at 24- and 26-weeks gestational age had irregularly enlarged ventricular trigones with minimal periventricular gliosis. Patients at 28-34 weeks had variably dilated ventricles with periventricular gliosis. The 36-week neonate had mild cortical and subcortical atrophy and gliosis superimposed on deep white matter and periventricular gliosis. Term neonates had significant cortical and subcortical gliosis and atrophy in the parasagittal watershed areas. Postterm neonates (44-46 weeks) showed cortical and subcortical watershed gliosis and atrophy with sparing of the immediate periventricular region. Two children suffered cardiocirculatory arrest; their scans revealed a different pattern of brain damage, demonstrating primarily brainstem, thalamic, and basal ganglia involvement. MR appears to be a powerful tool in the assessment of brain damage resulting from perinatal asphyxia that gives important clues to the time and nature of the asphyxia.     

Choroid plexus changes after temporal lobectomy

BACKGROUND AND PURPOSE: Postoperative contrast-enhanced MR imaging of the brain is routinely used when evaluating for residual or recurrent brain tumor. It is imperative to be aware of morphologic changes and imaging features that typically occur in response to surgical manipulation at the postoperative site to avoid misinterpretation of imaging findings. Our purpose was to determine normal postoperative changes and alterations in the choroid plexus among patients who had undergone temporal lobectomy in order to distinguish this appearance from pathologic changes that may be seen in the presence of infection or recurrent tumors. METHODS: We reviewed 159 MR scans from 95 patients with hippocampal sclerosis or gliosis who underwent temporal lobectomy for treatment of intractable epilepsy. Choroid plexus location and size were assessed on contrast-enhanced T1-weighted images. RESULTS: After temporal lobectomy, the choroid plexus enlarged and sagged into the resection site. Increase in the size of the choroid plexus occurred in 58% of cases overall. The degree of enhancement also increased after surgery, sometimes resulting in a nodular pattern of enhancement. The changes were most marked during the 1st week after temporal lobectomy, and showed an enlarged, markedly enhancing choroid plexus on 86% of the scans. CONCLUSION: Postoperative changes of the choroid plexus after temporal lobectomy include sagging into the resection site, an increased size, and an increased degree of enhancement. Normal postoperative morphologic characteristics may mimic neoplastic enhancement pattern. Familiarity with this appearance is important to avoid a pitfall in diagnosis of recurrent postoperative temporal lobe neoplasms.