Late postictal residual perfusion abnormality in epileptogenic zone found on 6-hour postictal SPECT

Arterial Spin Labeling Changes Parallel Asymmetric Perisylvian and Perirolandic Symptoms in 3 Pediatric Cases of Anti-NMDAR Encephalitis

BACKGROUND AND OBJECTIVES

Anti-NMDA receptor autoimmune encephalitis (NMDAR AE) is an autoantibody-mediated disorder characterized by seizures, neuropsychiatric symptoms, movement disorder, and focal neurologic deficits. Conventionally defined broadly as an inflammatory brain disease, the heterotopic localization is rarely discussed in children. Imaging findings are often nonspecific, and there are no early biomarkers of disease other than the presence of anti-NMDAR antibodies.

METHODS

We conducted a retrospective analysis of our pediatric NMDAR AE cases (as determined by either positive serum or CSF antibodies or both) at Texas Children's Hospital between 2020-2021 and extracted medical record data of those patients who had arterial spin labeling (ASL) as part of their imaging workup for encephalitis. The ASL findings were described in the context of their symptoms and disease courses.

RESULTS

We identified 3 children on our inpatient floor, intensive care unit (ICU), and emergency department (ED) settings who were diagnosed with NMDAR AE and had ASL performed as part of their focal neurologic symptom workup. All 3 patients presented with focal neurologic deficits, expressive aphasia, and focal seizures before the onset of other well-characterized NMDAR AE symptoms. Their initial MRI revealed no diffusion abnormalities but uncovered asymmetric and predominantly unilateral multifocal hyperperfusion of perisylvian/perirolandic regions on ASL that correlated with focal EEG abnormalities and their focal examination findings. All 3 patients were treated with first-line and second-line therapies, and their symptoms improved.

DISCUSSION

We found that ASL may be a suitable early imaging biomarker to highlight perfusion changes corresponding to the functional localization of NMDAR AE in pediatric patients. We briefly highlight the neuroanatomic parallels between working models of schizophrenia, chronic NMDAR antagonist administration (ketamine abuse), and NMDAR AE affecting primarily language centers. The regional specificity seen in NMDAR hypofunction may make ASL a reasonable early and specific biomarker of NMDAR AE disease activity. Future studies are necessary to evaluate regional changes in those patients who present with primarily psychiatric phenotypes rather than classical focal neurologic deficits.

Diagnostic Accuracy of Arterial Spin-Labeling MR Imaging in Detecting the Epileptogenic Zone: Systematic Review and Meta-analysis

BACKGROUND

A noninvasive, safe, and economic imaging technique is required to identify epileptogenic lesions in the brain.

PURPOSE

Our aim was to perform a meta-analysis evaluating the accuracy of arterial spin-labeling in localizing the epileptic focus in the brain and the changes in the blood perfusion in these regions.

DATA SOURCES

Our sources were the PubMed and EMBASE data bases.

STUDY SELECTION

English language studies that assessed the diagnostic accuracy of arterial spin-labeling for detecting the epileptogenic zone up to July 2019 were included.

DATA ANALYSIS

The symptomatogenic foci of seizures in the brain were determined and used as the references. The relevant studies were evaluated using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. The outcomes were evaluated using the pooled sensitivity, pooled specificity, pooled accuracy, diagnostic odds ratio, area under the summary receiver operating characteristic curve, and likelihood ratio.

DATA SYNTHESIS

Six studies that included 174 patients qualified for this meta-analysis. The pooled sensitivity, pooled specificity, and area under the summary receiver operating characteristic curve were 0.74 (95% CI, 0.65-0.82), 0.35 (95% CI, 0.03-0.90), and 0.73 (95% CI, 0.69-0.76), respectively. The accuracy of arterial spin-labeling for localizing the epileptic focus was 0.88 (accuracy in arterial spin-labeling/all perfusion changes in arterial spin-labeling) in cases of a positive arterial spin-labeling result. The epileptogenic zone exhibited hyperperfusion or hypoperfusion.

LIMITATIONS

Only a few studies were enrolled due to the strict inclusion criteria.

CONCLUSIONS

Arterial spin-labeling can be used for assessing, monitoring, and reviewing, postoperatively, patients with epilepsy. Blood perfusion changes in the brain may be closely related to the seizure time and pattern.

Arterial spin labeling hyperperfusion in seizures associated with non-ketotic hyperglycaemia: is it merely a post-ictal phenomenon?

A 53-year-old chronic uncontrolled diabetic patient presented with one episode of generalized seizures followed by drowsiness and post-ictal confusion. MR imaging at admission revealed left temporal subcortical T2/FLAIR hypointensities with overlying cortical T2/FLAIR hyperintensities and increased perfusion on arterial spin labeling (ASL). Follow-up imaging at 4- and 8-week interval revealed persistent ASL hyperperfusion with significant resolution of conventional MR imaging findings. Delayed persistent ASL hyperperfusion suggests that hyperglycemia-induced increased blood-brain barrier permeability rather than a mere post-ictal phenomenon in non-ketotic hyperglycemia (NKH) and may result in long-term cognitive disturbances.

Hemodynamic state of periictal hyperperfusion revealed by arterial spin-labeling perfusion MR images with dual postlabeling delay

Background

Magnetic resonance imaging (MRI), including perfusion MRI with arterial spin labeling (ASL) and diffusion-weighted imaging (DWI), are applied in the periictal detection of circulatory and metabolic consequences associated with epilepsy. Although previous report revealed that prolonged ictal hyperperfusion on ASL can be firstly detected and cortical hyperintensity of cytotoxic edema on DWI secondarily obtained from an epileptically activated cortex, the hemodynamic state of the periictal hyperperfusion has not been fully demonstrated.

Methods study-1

We retrospectively analyzed the relationship between seizure manifestations and the development of periictal MRI findings, in Case 1 with symptomatic partial epilepsy, who underwent repeated periictal ASL/DWI examination for three epileptic ictuses (one examination for each ictus). Study-2: We evaluated the hemodynamic state of periictal hyperperfusion with the ASL technique using a dual postlabeling delay (PLD) of 1.5 and 2.5 s in nine patients, according to the presence or absence of the localized epileptogenic lesion (EL) on conventional 3 T-MRI, who were divided into Group EL+ (six patients) and Group EL- (three patients).

Results

Study-1 confirmed that the stratified representation of the periictal MRI findings depends on the time interval between the ictal cessation and MRI examination in addition to the magnitude and duration of the epileptic activity. In Study-2, two types of periictal hyperperfusion were noted. In all six Group EL+ patients, periictal ASL findings showed "fast flow type". Markedly increased ASL signals were noted at the epileptically activated cortex, having a tight topographical relationship with EL, on ASL with a PLD of 1.5 s, which is decreased on ASL with a PLD of 2.5 s. In all three Group EL- patients, periictal ASL findings showed "gradual flow type", which is characterized by gradual signal increase of the epileptically activated cortex on ASL with a PLD of 1.5 and 2.5 s.

Conclusion

We confirmed that ASL hyperperfusion is superior to DWI in the periictal detection of epileptic events. ASL with dual PLD offers the ability to document two types of hemodynamics of periictal hyperperfusion.

The initial use of arterial spin labeling perfusion and diffusion-weighted magnetic resonance images in the diagnosis of nonconvulsive partial status epileptics

BACKGROUND

In the diagnosis of nonconvulsive status epilepticus (NCSE), capture of ongoing ictal electroencephalographic (EEG) findings is the gold standard; however, this is practically difficult without continuous EEG monitoring facilities. Magnetic resonance imaging (MRI), including diffusion-weighted imaging (DWI) and perfusion MRI with arterial spin labeling (ASL), have been applied mainly in emergency situations. Recent reports have described that ictal MRI findings, including ictal hyperperfusion on ASL and cortical hyperintensity of cytotoxic edema on DWI, can be obtained from epileptically activated cortex. We demonstrate the characteristics and clinical value of ictal MRI findings.

METHODS

Fifteen patients diagnosed as having NCSE (eight had complex partial status epilepticus (SE) and seven subtle SE) who underwent an initial MRI and subsequent EEG confrmation, participated in this study. Follow-up MRI and repeated routine EEG were performed.

RESULTS

In 11 patients (73%), ictal MRI findings were obtained on both DWI and ASL, while in four (27%) patients, ictal hyperperfusion was found on ASL without any DWI findings being obtained. In all 10 patients with an epileptogenic lesion, there was a tight topographical relationship between the lesion and the localization of ictal MRI findings. In the other five patients, ictal MRI findings were useful to demonstrate the pathophysiological mechanism of NCSE of non-lesional elderly epilepsy, or 'de novo' NCSE of frontal origin as situation-related NCSE. Ictal MRI findings are generally transient; however, in three cases they still persisted, even though ictal EEG findings had completely improved.

CONCLUSION

The present study clearly demonstrates that the initial use of ASL and DWI could help to diagnose partial NCSE and also combined use of the MRI and EEG allows documentation of the pathophysiological mechanism in each patient.

Capability of arterial spin labeling MR imaging in localizing seizure focus in clinical seizure activity

PURPOSE

The purpose of this study was to evaluate cerebral blood flow using arterial spin labeling (ASL) perfusion magnetic resonance (MR) imaging in patients with clinical seizure activity and determine its diagnostic performance in identifying seizure focus.

MATERIALS AND METHODS

Institutional Review Board of our hospital approved this retrospective study. Informed consent was waived. Clinical seizure focus was determined by a neurologist based on seizure semiology, electroencephalography, and conventional imaging modalities. The diagnostic performance of ASL perfusion MR imaging to identifying seizure focus compared to clinical seizure focus was analyzed.

RESULTS

Clinical seizure focus was localized in 95% (42/44) of patients. The sensitivity and specificity of ASL perfusion MR imaging for identifying seizure focus were 74% (95% CI: 58%, 86%) (clinical seizure focus was localizable in 31 of 42 patients, including complete concordance in 10 patients and partial concordance in 21 patients) and 0% (95% CI: 0%, 84%) (for the two patients whose clinical seizure foci were not localizable, they were identified by ASL perfusion MR imaging), respectively. Thus, the overall accuracy of ASL perfusion MR imaging for localizing seizure focus was 70% (33/44). For 4 patients who had abnormal perfusion on ASL, their seizure foci based on ASL perfusion MR imaging were discordant with clinical seizure foci.

CONCLUSION

ASL perfusion MR imaging can provide information about perfusion status and important diagnostic clue in localizing seizure focus in patients with clinical seizure activity. It has the potential as a non-invasive complementary diagnostic tool for patients with clinical seizure activity.

Nonconvulsive partial status epilepticus mimicking recurrent infarction revealed by diffusion-weighted and arterial spin labeling perfusion magnetic resonance images

"Non-convulsive" partial status epilepticus (SE) is an important pathologic condition that should be differentiated from cerebral infarction. Herein, we reported 2 patients who had partial SE associated with old infarction in the right parietal lobe. Each patient had 2 episodes of left hemiparesis and hemisensory disturbance without convulsion. On diffusion-weighted magnetic resonance images (DW-MRI), a hyperintense lesion was noted in the cortex around the old infarction lesion, and recurrent infarction was suspected. Although electroencephalography (EEG) failed to reveal ictal discharges or interictal paroxysmal activities in 3 of 4 episodes, perfusion images with arterial spin labeling (ASL) clearly demonstrated ictal hyperperfusion in the area corresponding to the cortical hyperintense lesion on DW-MRI. After appropriate anticonvulsant treatment based on the diagnosis of partial SE, clinical symptoms were completely improved. These data stress the importance of cortical hyperintensity on DW-MRI and ictal ASL hyperperfusion, even when SE cannot be determined from EEG.

Cerebral perfusion alterations in epileptic patients during peri-ictal and post-ictal phase: PASL vs DSC-MRI

Non-invasive pulsed arterial spin labeling (PASL) MRI is a method to study brain perfusion that does not require the administration of a contrast agent, which makes it a valuable diagnostic tool as it reduces cost and side effects. The purpose of the present study was to establish the viability of PASL as an alternative to dynamic susceptibility contrast (DSC-MRI) and other perfusion imaging methods in characterizing changes in perfusion patterns caused by seizures in epileptic patients. We evaluated 19 patients with PASL. Of these, the 9 affected by high-frequency seizures were observed during the peri-ictal period (within 5hours since the last seizure), while the 10 patients affected by low-frequency seizures were observed in the post-ictal period. For comparison, 17/19 patients were also evaluated with DSC-MRI and CBF/CBV. PASL imaging showed focal vascular changes, which allowed the classification of patients in three categories: 8 patients characterized by increased perfusion, 4 patients with normal perfusion and 7 patients with decreased perfusion. PASL perfusion imaging findings were comparable to those obtained by DSC-MRI. Since PASL is a) sensitive to vascular alterations induced by epileptic seizures, b) comparable to DSC-MRI for detecting perfusion asymmetries, c) potentially capable of detecting time-related perfusion changes, it can be recommended for repeated evaluations, to identify the epileptic focus, and in follow-up and/or therapy-response assessment.

Arterial spin-labeled magnetic resonance imaging in hyperperfused seizure focus: a case report

We present a case of a clinically suspected cerebral infarction that was diagnosed as a seizure focus on pulsed arterial spin labeling. The finding of hyperperfusion with perfusion imaging significantly impacted clinical management of the patient.

Surgery for medically intractable temporal lobe epilepsy during early life

PURPOSE

Temporal lobe epilepsy (TLE) in early life is often a catastrophic disorder with pharmacoresistant seizures and secondary neurological deterioration. there is little data available regarding epilepsy surgery performed in infants and young children and no prior study has focused on tle.

METHODS

We analyzed the results of temporal resection for epilepsy as the primary indication in children less than age 5 years who had at least 2 years of follow-up.

RESULTS

20 children (14 males) were identified with a mean age at surgery of 26 months and a mean age at seizure onset of 12 months. Clinical presentation was diverse. Typical psychomotor seizures (n = 4; mean age at surgery 37 months) were followed by prominent motor changes (n = 7; 30 months) and were occasionally isolated (n = 3; 23 months). Epileptic spasms were noted in six patients and were frequently associated with lateralizing features. The interictal EEG was lateralizing in 15 patients and the ictal EEG was lateralizing in 18 patients. Brain MRI provided localizing value in 16 patients, ictal SPECT was concordant in 4/8 cases. Invasive EEG was employed in six cases. At mean follow-up of 5.5 years, 65% of the children were seizure-free and 15% had >90% seizure reduction. Morbidity included infection and hydrocephalus in one case and stroke-related hemiparesis in two cases. Cortical dysplasia was identified in eight children, tumors in eight including two DNET, two ganglioglioma, and four malignant tumors. Hippocampal sclerosis was present in four cases, always as dual pathology.

CONCLUSION

TLE presents in early life with varied and severe manifestations. Excisional procedures in this age group are associated with favorable seizure reduction similar to older children and in adults.

Ictal SPECT in neocortical epilepsies: clinical usefulness and factors affecting the pattern of hyperperfusion

INTRODUCTION

The aims of this analysis were to: (1) determine the value of ictal SPECT in the localization of neocortical epileptogenic foci, (2) evaluate the relationships between the results of ictal SPECT and other potential affecting factors, and (3) compare traditional visual analysis and the subtraction method.

METHODS

We retrospectively analyzed 81 consecutive patients with neocortical epilepsy who underwent epilepsy surgery and achieved a favourable surgical outcome, including 36 patients with normal MRI. Side-by-side visual analysis and subtraction images were classified as correctly localizing,correctly lateralizing, or non-localizing/non-lateralizing images according to the resected lobe.

RESULTS

Side-by-side visual analysis and subtraction SPECT correctly localized the epileptogenic lobe in 58.9% and 63.0% of patients, respectively. The two methods were complementary and the diagnostic sensitivity of ictal SPECT using the two methods was 79.0%. Ictal SPECT using the visual method correctly localized the epileptogenic lobe more frequently in patients with a localizing pattern of ictal scalp EEG at the time of radioligand injection. When using subtraction images, an injection delay of less than 20 s after seizure onset was significantly correlated with correct localization. The subtraction method was superior to the visual method for localizing frontal lobe epilepsy (FLE) and parietal lobe epilepsy (PLE), and in patients with non-localizing/non-lateralizing EEG at onset.

CONCLUSIONS

Ictal SPECT analyses using visual and subtraction methods are useful and complementary for the localization of the epileptogenic foci of neocortical epilepsy. Early radioligand injection and ictal EEG patterns are related to ictal SPECT localization. The subtraction method may be more useful in some epileptic syndromes.

Prognostic Factors in Neocortical Epilepsy Surgery: Multivariate Analysis

PURPOSE

Defining prognostic factors for neocortical epilepsy surgery is important for the identification of ideal candidates and for predicting the prognosis of individual patients. We use multivariate analysis to identify favorable prognostic factors for neocortical epilepsy surgery.

METHODS

One hundred ninety-three neocortical epilepsy patients, including 91 without focal lesions on MRI, were included. Sixty-one had frontal lobe epilepsy (FLE), 80 had neocortical temporal lobe epilepsy (nTLE), 21 had parietal lobe epilepsy (PLE), and 22 had occipital lobe epilepsy (OLE). The primary outcome variable was patient status >or=2 years after surgery (i.e., seizure free or not). Clinical characteristics and the recent presurgical diagnostic modalities were considered as probable prognostic factors. Univariate and standard multiple logistic regression analyses were used to identify favorable prognostic factors.

RESULTS

The seizure-free rate was 57.5%. By univariate analysis, a focal lesion on MRI, localized ictal onset on surface EEG, epilepsies other than FLE, localized hypometabolism on fluorodeoxyglucose-positron emission tomography (FDG-PET), and pathologies other than cortical dysplasia were significantly associated with a seizure-free outcome (p<0.05). Multivariate analysis revealed that a focal lesion on MRI (p=0.003), correct localization by FDG-PET (p=0.007), and localized ictal onset on EEG (p=0.01) were independent predictors of a good outcome.

CONCLUSIONS

The presence of a focal lesion on MRI, correct localized hypometabolism on FDG-PET, or localized ictal rhythms on EEG were identified as predictors of a seizure-free outcome. Our results suggest that these findings allow the selection of better candidates for neocortical epilepsy surgery.

Disparity of perfusion and glucose metabolism of epileptogenic zones in temporal lobe epilepsy demonstrated by SPM/SPAM analysis on 15O water PET, [18F]FDG-PET, and [99mTc]-HMPAO SPECT

PURPOSE

To elucidate uncoupling of perfusion and metabolism and its significance in epilepsy, 15O water and 18F fluorodeoxyglucose (FDG) positron emission tomography (PET) and Tc-99m hexamethyl-propyleneamine-oxime (HMPAO) single-photon emission computed tomography (SPECT) were examined by SPM (statistical parametric mapping) and quantitation by using SPAM (statistical probabilistic anatomic map).

METHODS

[15O]water and [18F]FDG-PET, and [99mTc]-HMPAO SPECT were performed in 25 patients (SPECT in 17 of 25) with medial temporal lobe epilepsy. For volume of interest (VOI) count analysis, the normalized counts using VOI based on SPAM templates of PET and SPECT were compared with those of the normal controls. Perfusion or metabolism was found abnormal if the Z score was >2 for each VOI. For SPM analysis, the differences between each patient's image and a group of normal control images (t statistic for p < 0.01) on a voxel-by-voxel basis were examined to find significant decreases in perfusion or metabolism.

RESULTS

With SPAM VOI count analysis, areas of hypoperfusion were found in 13 patients in the epileptogenic temporal lobes by [15O]water PET and areas of hypometabolism in 21 patients by [18F]FDG-PET. With voxel-based SPM analysis, the epileptogenic zones were localized in 15 by [15O]water PET and in 23 patients by [18F]FDG-PET. The localization by [15O]water PET was concordant with that of [18F]FDG-PET. The areas of hypoperfusion on [15O]water PET were absent or smaller than the areas of hypometabolism on [18F]FDG-PET. Interictal [99mTc]-HMPAO SPECT revealed the hypoperfused zones in seven of 17 patients on visual assessment.

CONCLUSIONS

SPAM VOI count and SPM analysis of [15O]water and [18F]FDG-PET and [99mTc]-HMPAO SPECT revealed that in the same patients, the areas of hypoperfusion were concordant with but smaller than the areas of hypometabolism. Discordance of perfusion and metabolic abnormalities represents an uncoupling of perfusion and metabolism in the epileptogenic zones, and this might explain the lower diagnostic accuracy of perfusion imaging in temporal lobe epilepsy.

EEG coherence in post-LSD visual hallucinations

LSD use in certain individuals may result in chronic visual hallucinations, a DSM-IV syndrome known as hallucinogen persisting perception disorder (HPPD). We studied 38 HPPD subjects with a mean of 9.7 years of persistent visual hallucinations and 33 control subjects. Measures of local and medium distance EEG spectral coherence were calculated from all subjects. Coherence, a measure of spectral similarity over time, may estimate cortical coupling. In the eyes-open state in HPPD subjects, widespread reduction of coherence was noted. However, upon eye closure, the occipital region demonstrated augmented regional coherence over many frequencies but with reduced coherence of the occipital region to more distant regions. This occipital coherence increase correlated with previously reported shortened occipital visual evoked potential latency for HPPD subjects. We speculate from coherence and known clinical and psychophysical data that, in HPPD, there is widespread cortical inhibition in the eyes-opened state, but localized and isolated occipital disinhibition upon eye closure, a state known to facilitate hallucinatory experiences. An analogy is drawn to findings in the interictal and ictal epileptic focus. In HPPD, we speculate that occipital EEG hypersynchrony resulting from increased regional coherence, when coupled with relative isolation of visual cortex, especially upon eye closure, facilitates hallucinations and illusions.