Reversible periictal MRI abnormalities: Clinical correlates and long-term outcome in 12 patients

Status epilepticus in BRAF-related cardio-facio-cutaneous syndrome: Focus on neuroimaging clues to physiopathology

OBJECTIVE

Cardio-facio-cutaneous syndrome (CFC) is a genetic disorder due to variants affecting genes coding key proteins of the Ras/MAPK signaling pathway. Among the different features of CFC, neurological involvement, including cerebral malformations and epilepsy, represents a common and clinically relevant aspect. Status epilepticus (SE) is a recurrent feature, especially in a specific subgroup of CFC patients with developmental and epileptic encephalopathy (DEE) and history of severe pharmacoresistant epilepsy. Here we dissect the features of SE in CFC patients with a particular focus on longitudinal magnetic resonance imaging (MRI) findings to identify clinical-radiological patterns and discuss the underlying physiopathology.

METHODS

We retrospectively analyzed clinical, electroencephalogram (EEG), and MRI data collected in a single center from a cohort of 23 patients with CFC carrying pathogenic BRAF variants who experienced SE during a 5-year period.

RESULTS

Seven episodes of SE were documented in 5 CFC patients who underwent EEG and MRI at baseline. MRI was performed during SE/within 72 hours from SE termination in 5/7 events. Acute/early post-ictal MRI findings showed heterogenous abnormalities: restricted diffusion in 2/7, focal area of pcASL perfusion change in 2/7, focal cortical T2/FLAIR hyperintensity in 2/7. Follow-up images were available for 4/7 SE. No acute changes were detected in 2/7 (MRI performed 4 days after SE termination).

SIGNIFICANCE

Acute focal neuroimaging changes concomitant with ictal EEG focus were present in 5/7 episodes, though with different findings. The heterogeneous patterns suggest different contributing factors, possibly including the presence of focal cortical malformations and autoinflammation. When cytotoxic edema is revealed by MRI, it can be followed by permanent structural damage, as already observed in other genetic conditions. A better understanding of the physiopathology will provide access to targeted treatments allowing to prevent long-term adverse neurological outcome.

PLAIN LANGUAGE SUMMARY

Cardio-facio-cutaneous syndrome is a genetic disorder that often causes prolonged seizures known as status epilepticus. This study has a focus on electroclinical and neuroimaging patterns in patients with cardio-facio-cutaneous syndrome. During these status epilepticus episodes, we found different abnormal brain imaging patterns in patients, indicating various causes like brain malformations and inflammation. Understanding these patterns could help doctors find specific treatments, protecting cardio-facio-cutaneous syndrome patients from long-term brain damage.

Restricted diffusion of the callosal splenium is highly specific for seizures in neonates

BACKGROUND

To determine whether restricted diffusion of the callosal splenium is specific for seizure activity in neonates.

METHODS

We performed a retrospective chart review of 123 neonates who had a diagnosis of hypoxic ischemic encephalopathy (HIE) who underwent therapeutic cooling and had magnetic resonance imaging (MRI) within the first 10 days of life. The regions examined for injury include the callosal splenium, cortex, deep gray matter, and subcortical white matter. Neurodevelopmental outcomes were secondarily assessed using the Bayley Scales of Infant Development at 12 to 18 months of age and > 18 months of age. APGAR scores and pH, two important markers of hypoxia/ischemia and encephalopathy, were also analyzed in relation to these outcomes.

RESULTS

Approximately 41% of the neonates had at least one abnormal region on brain MRI, and 21% had abnormal signal in the splenium. Clinical and/or electrographic seizures were documented in 32%. Changes in the splenium had a sensitivity of 54%, specificity of 94%, and positive predictive value of 81% for seizure presence. The presence of seizures and splenium lesion was associated poor developmental outcomes at 12 to 18 months of age. APGAR scores at 10 minutes, but not lowest pH was associated with splenial changes.

CONCLUSIONS

Restricted diffusion of the callosal splenium is specific for recent seizures in neonates with HIE. Seizures and splenial lesion represent risk factors for poor neurodevelopmental outcomes. Child neurologists and neonatologists should consider splenial signal abnormality in their assessment of neonates at risk for seizures and counsel families about likely outcomes accordingly.

Increased volume of cerebral oedema is associated with risk of acute seizure activity and adverse neurological outcomes in encephalitis - regional and volumetric analysis in a multi-centre cohort

BACKGROUND

Seizures can occur unpredictably in patients with acute encephalitis syndrome (AES), and many suffer from poor long-term neurological sequelae. Establishing factors associated with acute seizures risk and poor outcomes could support clinical care. We aimed to conduct regional and volumetric analysis of cerebral oedema on magnetic resonance imaging (MRI) in patients with AES. We assessed the relationship of brain oedema with acute seizure activity and long-term neurological outcome.

METHODS

In a multi-centre cohort study, adults and children presenting with an AES were recruited in the UK. The clinical and brain MRI data were retrospectively reviewed. The outcomes variables were inpatient acute seizure activity and neurological disability at six-months post-discharge. A poor outcome was defined as a Glasgow outcome score (GOS) of 1-3. We quantified regional brain oedema on MRI through stereological examination of T2-weighted images using established methodology by independent and blinded assessors. Clinical and neuroimaging variables were analysed by multivariate logistic regression to assess for correlation with acute seizure activity and outcome.

RESULTS

The study cohort comprised 69 patients (mean age 31.8 years; 53.6% female), of whom 41 (59.4%) had acute seizures as inpatients. A higher Glasgow coma scale (GCS) score on admission was a negative predictor of seizures (OR 0.61 [0.46-0.83], p = 0.001). Even correcting for GCS on admission, the presence of cortical oedema was a significant risk factor for acute seizure activity (OR 5.48 [1.62-18.51], p = 0.006) and greater volume of cerebral oedema in these cortical structures increased the risk of acute seizures (OR 1.90 [1.12-3.21], p = 0.017). At six-month post-discharge, 21 (30.4%) had a poor neurological outcome. Herpes simplex virus encephalitis was associated with higher risk of poor outcomes in univariate analysis (OR 3.92 [1.08-14.20], p = 0.038). When controlling for aetiology, increased volume of cerebral oedema was an independent risk factor for adverse neurological outcome at 6 months (OR 1.73 [1.06-2.83], p = 0.027).

CONCLUSIONS

Both the presence and degree of cerebral oedema on MRIs of patients with AES may help identify patients at risk of acute seizure activity and subsequent long-term morbidity.

Association of ictal imaging changes in status epilepticus and neurological deterioration

OBJECTIVE

In patients with status epilepticus (SE), the clinical significance of ictal changes on magnetic resonance imaging (MRI) is insufficiently understood. We here studied whether the presence of ictal MRI changes was associated with neurological deterioration at discharge.

METHODS

The retrospective cohort comprised all identifiable patients treated at Odense University Hospital in the period 2008-2017. All amenable MRIs were systemically screened for ictal changes. Patient demographics, electroencephalography, seizure characteristics, treatment, and SE duration were assessed. Neurological status was estimated before and after SE. The predefined endpoint was the association of neurological deterioration and ictal MRI changes.

RESULTS

Of 261 eligible patients, 101 received at least one MRI during SE or within 7 days after cessation; 43.6% (44/101) had SE due to non- or less brain-damaging etiologies. Patients who received MRI had a longer duration of SE, less frequently had a history of epilepsy, and were more likely to have SE due to unknown causes. Basic characteristics (including electroencephalographic features defined by the Salzburg criteria) did not differ between patients with (n = 20) and without (n = 81) ictal MRI changes. Timing of MRI was important; postictal changes were rare within the first 24 h and hardly seen >5 days after cessation of SE. Ictal MRI changes were associated with a higher risk of neurological deterioration at discharge irrespective of etiology. Furthermore, they were associated with a longer duration of SE and higher long-term mortality that reached statistical significance in patients with non- or less brain-damaging etiologies.

SIGNIFICANCE

In this retrospective cohort, ictal changes on MRI were associated with a higher risk of neurological deterioration at discharge and, possibly, with a longer duration of SE and poorer survival.

Brain Imaging in Epilepsy-Focus on Diffusion-Weighted Imaging

Epilepsy is a common neurological disorder; 1% of people worldwide have epilepsy. Differentiating epileptic seizures from other acute neurological disorders in a clinical setting can be challenging. Approximately one-third of patients have drug-resistant epilepsy that is not well controlled by current antiepileptic drug therapy. Surgical treatment is potentially curative if the epileptogenic focus is accurately localized. Diffusion-weighted imaging (DWI) is an advanced magnetic resonance imaging technique that is sensitive to the diffusion of water molecules and provides additional information on the microstructure of tissue. Qualitative and quantitative analysis of peri-ictal, postictal, and interictal diffusion images can aid the differential diagnosis of seizures and seizure foci localization. This review focused on the fundamentals of DWI and its associated techniques, such as apparent diffusion coefficient, diffusion tensor imaging, and tractography, as well as their impact on epilepsy in terms of differential diagnosis, epileptic foci determination, and prognosis prediction.

Prevalence, distribution, and clinical associations of suspected postictal changes on brain magnetic resonance imaging in epileptic dogs

OBJECTIVE

To determine the prevalence of presumed postictal changes (PC) on brain MRI in epileptic dogs, describe their distribution, and recognize possible correlations with different epilepsy features.

ANIMALS

540 client-owned dogs with epilepsy and a complete medical record that underwent brain MRI at 4 veterinary referral hospitals between 2016 and 2019.

PROCEDURES

Data were collected regarding signalment, seizure type, seizure severity, time between last seizure and MRI, and etiological classification of epilepsy. Postictal changes were considered when solitary or multiple intraparenchymal hyperintense lesions were observed on T2-weighted and fluid-attenuated inversion recovery images and were hypointense or isointense on T1-weighted sequences, which were not confined to a vascular territory and showed no to mild mass effect and no to mild contrast enhancement.

RESULTS

Sixty-seven dogs (12.4%) showed MRI features consistent with PC. The most common brain sites affected were the piriform lobe, hippocampus, temporal neocortex, and cingulate gyrus. Dogs having suffered cluster seizures or status epilepticus were associated with a higher probability of occurrence of PC, compared to dogs with self-limiting seizures (OR 2.39; 95% confidence interval, 1.33 to 4.30). Suspected PC were detected both in dogs with idiopathic epilepsy and in those with structural epilepsy. Dogs with unknown-origin epilepsy were more likely to have presumed PC than were dogs with structural (OR 0.15; 95% confidence interval, 0.06 to 0.33) or idiopathic epilepsy (OR 0.42; 95% confidence interval, 0.20 to 0.87). Time between last seizure and MRI was significantly shorter in dogs with PC.

CLINICAL RELEVANCE

MRI lesions consistent with PC were common in epileptic dogs, and the brain distribution of these lesions varied. Occurrence of cluster seizures or status epilepticus, diagnosis of unknown origin epilepsy, and lower time from last seizure to MRI are predictors of suspected PC.

Magnetic resonance imaging findings in focal-onset status epilepticus

BACKGROUND AND PURPOSE

Magnetic resonance imaging (MRI) is commonly used in the diagnostic work-up for status epilepticus (SE). The purpose of this study was to characterize MRI features in SE patients and determine their association with clinical and electroencephalography (EEG) findings. The mid-term consequences of baseline MRI features were also analysed.

METHODS

This is a prospective study including consecutive patients with SE who underwent brain MRI within 240 h after SE onset. The MRI protocol included T1-weighted (T1WI), T2-weighted (T2W), fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging (DWI) sequences. Follow-up MRI was performed after SE resolution in some patients.

RESULTS

Sixty patients (56.7% men, mean age 58.3 years) were included. SE-related MRI abnormalities were seen in 31 (51.7%), manifesting as hyperintensities on T2W/FLAIR imaging (58.1%) and DWI (74.2%) sequences. Hippocampal and pulvinar involvement was seen in 58.0% and 25.8% of patients, respectively. MRI abnormalities were associated with a longer SE duration (p = 0.013) and the presence of lateralized periodic discharges (LPDs) on EEG (p < 0.001). Amongst the 33 follow-up MRIs, nine (27.3%) showed mesial temporal sclerosis (MTS), which was associated with severe clinical status (p = 0.031), hippocampal oedema (p = 0.001) and LPDs (p = 0.001) at baseline. A poorer clinical outcome was associated with baseline T2W/FLAIR imaging hyperintensities (p = 0.003).

CONCLUSION

MRI showed abnormalities in more than half of SE patients. A longer SE duration and LPDs on EEG were associated with SE-related MRI abnormalities and the development of MTS.

Seizure-induced reversible MRI abnormalities in patients with single seizures: a systematic review

Differentiating seizure-induced reversible MRI abnormalities from MRI changes secondary to underlying cerebral pathologies can be challenging for clinicians in the investigation of seizures. The aim of this study was to delineate the characteristic features of reversible seizure-induced MRI abnormalities. A systematic search of the databases Medline (1946-2020), PubMed (1996-2020), and Embase (1947-2020) was performed in keeping with the Preferred Items Reporting for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. All publications in English, including case reports, of single unprovoked seizure patients with seizure-induced MRI abnormalities demonstrating complete resolution, were included. Two authors extracted data using a predefined template and evaluated the quality of the included studies. MRI data were additionally reviewed by a neuroradiologist. All data were synthesised qualitatively. There were 11 publications altogether, yielding a total of 27 cases that were pertinent to our research question. Abnormalities were most commonly observed on T2-weighted sequences. The most commonly observed constellations of MRI features ("composite pattern") included the following: cortical or subcortical signal change with or without leptomeningeal enhancement, signal abnormality in the splenium of the corpus callosum, and hippocampal signal abnormality. Seizure-induced reversible MRI abnormalities were observed as early as six hours from seizure onset and resolved completely as early as five days from seizure onset. A key limitation of this systematic review was the variability and incomplete reporting of clinical data, especially with regards to seizure semiology and MRI sequences performed, which may have limited our ability to make more definitive conclusions. Seizure-induced reversible MRI changes may appear within hours of seizure onset and resolve within a variable time frame, ranging from days to weeks. Bilateral seizure-induced reversible MRI abnormalities tend to be associated with generalised seizures while unilateral seizure-induced reversible MRI abnormalities may be associated with focal seizures, usually ipsilateral to the seizure focus.

Hyperglycemia-induced seizures - Understanding the clinico- radiological association

Objectives:

To highlight the typical magnetic resonance imaging (MRI) findings in hyperglycemia-induced seizures and compare the results with similar previous studies with a brief mention of pathophysiological mechanisms.

Materials and Methods:

This retrospective study included medical and imaging records of six consecutive patients with hyperglycemia-induced seizures. The data analysis included a clinical presentation and biochemical parameters at admission. The MRI sequences were evaluated for region involved, presence of subcortical T2 hypo-intensity, cortical hyper-intensity, and restricted diffusion. Similar previous studies from the National Library of Medicine (NLM) were analyzed and compared with our study.

Results:

Twenty-four patients were included from four studies in previous literature for comparison. In our study, on imaging, posterior cerebral region was predominantly involved, with parietal involvement in 83.3%, followed by occipital, frontal, and temporal involvement in 33.3% patients compared with occipital in 58.3%, parietal in 45.8%, and frontal and temporal in 16.6% of patients in previous literature. The subcortical T2 hypo-intensity was present in 83.3% of the patients, cortical hyper-intensity in all patients, and restricted diffusion in 66.6% of the patients in our study compared with subcortical T2 hypo-intensity in 95.8% of the patients, cortical hyper-intensity in 62.5%, and restricted diffusion in 58.3% of the patients in previous literature.

Conclusion:

Although many etiologies present with subcortical T2 hypointensity, cortical hyperintensity, restricted diffusion, and postcontrast enhancement on MRI, the clinical setting of seizures in a patient with uncontrolled hyperglycemia, hyperosmolar state, and absence of ketones should suggest hyperglycemia-induced seizures to avoid misdiagnosis, unnecessary invasive investigations, and initiate timely management.

Advances in Knowledge:

Our study highlights the presence of posterior predominant subcortical T2, fluid-attenuated inversion recovery (FLAIR), and susceptibility-weighted angiography (SWAN) hypointensity; cortical hyperintensity; and restricted diffusion in hyperglycemia-induced seizures. The presence of T2 and SWAN hypointensity could support the hypothesis of possible deposition of free radicals and iron in the subcortical white matter.

Peri-ictal magnetic resonance imaging in status epilepticus: Temporal relationship and prognostic value in 60 patients

PURPOSE

Magnetic resonance imaging (MRI) changes associated with status epilepticus (SE) have been described in recent studies. Our aim was to evaluate the diagnosis and prognosis of the peri-ictal MRI changes detected in SE patients.

METHOD

All adults diagnosed with SE and examined by MRI within 240 h after SE onset were enrolled (2011-2017). Demographic, clinical and electroencephalography data, and functional status at admission and discharge were collected. MRI findings were recorded and relationships between clinical and MRI data, and between these data and functional outcome were analyzed.

RESULTS

Sixty patients included, 50% women, mean age 57.5 years. Median duration of SE was 51.46 h and median time from SE onset to MRI was 86.5 h. Of the total, 41.7% had a restricted diffusion pattern on diffusion-weighted imaging (DWI) and 63.3% had hyperintensities suggestive of edema on T2-weighted (T2WI)/FLAIR sequences. The factors independently associated with T2WI hyperintensities were the presence of acute cerebral lesions (p = 0.023), baseline STESS (p = 0.007), and MRI performed within 84 h (p = 0.007). Variables independently associated with diffusion restriction were a potentially fatal cause (p = 0.020), SE duration >24 h (p = 0.022), and MRI performed within the first 84 h (p = 0.045). In patients undergoing MRI within 84 h, the DWI and T2WI abnormalities were both highly associated with an unfavorable outcome.

CONCLUSIONS

Characteristic signal changes on DWI and T2WI sequences were seen in approximately half our SE patients undergoing early (<84 h) brain MRI studies, and were independently related to the patients' functional status at discharge.

The spectrum of peri-ictal MRI changes; four illustrative cases

PURPOSE

Seizure induced neuronal hyperexcitability and increased unmet metabolic neuronal demand results in failure of the sodium/potassium ATP pump. Sodium and water accumulates intracellularly with cellular swelling and reduced extracellular volume demonstrating hyperintensity on DWI and reduced ADC. The aim of this study was to describe 4 clinical cases where we identified abnormalities in diffusion restriction in the acute peri-ictal period and followed them longitudinally.

METHODS

Patients were recruited from the emergency department, clinical consultation service and epilepsy monitoring unit of two tertiary referral centres. Patients underwent either 1.5T or 3.0T MRI with DWI, ADC, T2-weighted and post contrast studies during their acute admission and again after a period of follow up.

RESULTS

Four patients were identified as having visible diffusion restriction and reduced ADC in one or both hippocampi and the splenium of the corpus callosum. These lesions either completely resolved, showed interval improvement or demonstrated atrophy on follow up imaging. The two patients with persisting abnormalities had presented with status epilepticus.

CONCLUSIONS

These acute ictal imaging changes give clinicians an important in-vivo look at the dynamic neuronal metabolic environment in the peri-ictal period. Areas that appear most susceptible include the mesial temporal structures and corpus callosum. Close imaging follow up to document resolution or evolution of long lasting sequelae is vital. There is no clear consensus as to why some patients develop ictal related imaging changes and others do not. Seizure length and time interval from ictus to scan appear to play a role but larger prospective studies are needed to confirm this.

Epileptic seizures with reversible lesions in bilateral frontoparietal lobes: A case report and literature review

Magnetic resonance imaging (MRI) is recommended for patients with epileptic seizures to rule out an underlying focal lesion. However, the radiological characteristics of epilepsy are not well elucidated. Transient periictal MRI abnormality (TPMA) refers to reversible MRI signal changes observed in epileptic patients. A 32-year-old man presented with a 2-week history of epileptic seizures, which initially manifested as focal aware seizures and progressed to a generalized tonic-clonic seizure on the third day. Electroencephalography showed sharp waves, sharp and slow wave complexes, and irregular δ waves over bilateral temporal lobes. After admission, brain MRI showed abnormal signals in the bilateral frontoparietal lobes. He was administered oral oxcarbazepine (75  mg twice daily). During follow-up he was seizure-free; the abnormal MRI signals persisted at 2 weeks, but were completely resolved at 4 months. The possibility of TPMA should be considered in patients with epileptic disorders, and differentiated from a potential epileptogenic lesion.

An exploration of the spectrum of peri-ictal MRI change; a comprehensive literature review

PURPOSE

The aim of this review was to identify published studies in the literature relating to ictal induced MRI change and to identify certain common themes, practical points for clinicians and areas for future research.

METHODS

We identified 96 articles that satisfied our inclusion criteria yielding 575 cases. All articles were analysed; number of subjects, spectrum of MRI and EEG change, aetiology, and follow-up (both clinical and imaging) were noted.

RESULTS

The most frequent imaging changes were restricted diffusion, T2-hyperintensity and reduced ADC values. The mesial temporal structures and neocortex were most commonly affected locations though subcortical structures like the thalamus and pulvinar were also described. Practical clinical points included; the development of PLEDS concordant with ictal imaging change was associated with worse clinical prognosis, patients with seizures due to symptomatic aetiology may be more likely to develop ictal related imaging change and follow up is vitally important to ensure that ictal related oedema is not misidentified as a mass lesion or conversely that a mass lesion is not misidentified as ictal related change.

CONCLUSION

Qualitative MRI studies have provided clinicians with useful in-vivo insights into the dynamic ictal neuronal environment. Changes are not only localised to the ictal focus but can be remote and irreversible. Small patient numbers varying study design and high numbers of symptomatic seizures makes comparison between studies problematic. Also there is possible microstructural quantitative MRI changes that are missed on qualitative MRI. There is a need for prospective quantitative MRI studies in patients with epilepsy peri-icatlly with a uniform period of follow up and comparison to control data.

Characteristics of seizure-induced signal changes on MRI in patients with first seizures

PURPOSE

The aim of this study was to investigate the predictive factors and identify the characteristics of the seizure-induced signal changes on MRI (SCM) in patients with first seizures.

METHODS

We conducted a retrospective study of patients with first seizures from March 2010 to August 2014. The inclusion criteria for this study were patients with 1) first seizures, and 2) MRI and EEG performed within 24h of the first seizures. The definition of SCM was hyper-intensities in the brain not applying to cerebral arterial territories. Multivariate logistic regression was performed with or without SCM as a dependent variable.

RESULTS

Of 431 patients with seizures visiting the ER, 69 patients met the inclusion criteria. Of 69 patients, 11 patients (15.9%) had SCM. Epileptiform discharge on EEG (OR 29.7, 95% CI 1.79-493.37, p=0.018) was an independently significant variable predicting the presence of SCM in patients with first seizures. In addition, the topography of SCM was as follows; i) ipsilateral hippocampus, thalamus and cerebral cortex (5/11), ii) unilateral cortex (4/11), iii) ipsilateral thalamus and cerebral cortex (1/11), iv) bilateral hippocampus (1/11). Moreover, 6 out of 7 patients who underwent both perfusion CT and MRI exhibited unilateral cortical hyperperfusion with ipsilateral thalamic involvement reflecting unrestricted vascular territories.

CONCLUSION

There is an association between epileptiform discharges and SCM. Additionally, the involvement of the unilateral cortex and ipsilateral thalamus in SCM and its hyperperfusion state could be helpful in differentiating the consequences of epileptic seizures from other pathologies.

Clinical implications of the cortical hyperintensity belt sign in fluid-attenuated inversion recovery images after bypass surgery for moyamoya disease

OBJECTIVE Transient neurological symptoms are frequently observed during the early postoperative period after direct bypass surgery for moyamoya disease. Abnormal signal changes in the cerebral cortex can be seen in postoperative MR images. The purpose of this study was to reveal the radiological features of the "cortical hyperintensity belt (CHB) sign" in postoperative FLAIR images and to verify its relationship to transient neurological events (TNEs) and regional cerebral blood flow (rCBF). METHODS A total of 141 hemispheres in 107 consecutive patients with moyamoya disease who had undergone direct bypass surgery were analyzed. In all cases, FLAIR images were obtained during postoperative days (PODs) 1-3 and during the chronic period (3.2 ± 1.13 months after surgery). The CHB sign was defined as an intraparenchymal high-intensity signal within the cortex of the surgically treated hemisphere with no infarction or hemorrhage present. The territory of the middle cerebral artery was divided into anterior and posterior parts, with the extent of the CHB sign in each part scored as 0 for none; 1 for presence in less than half of the part; and 2 for presence in more than half of the part. The sum of these scores provided the CHB score (0-4). TNEs were defined as reversible neurological deficits detected both objectively and subjectively. The rCBF was measured with SPECT using N-isopropyl-p-[¹²³I]iodoamphetamine before surgery and during PODs 1-3. The rCBF increase ratio was calculated by comparing the pre- and postoperative count activity. RESULTS Cortical hyperintensity belt signs were detected in 112 cases (79.4%) and all disappeared during the chronic period. Although all bypass grafts were anastomosed to the anterior part of the middle cerebral artery territory, CHB signs were much more pronounced in the posterior part (p < 0.0001). TNEs were observed in 86 cases (61.0%). Patients with TNEs showed significantly higher CHB scores than those without (2.31 ± 0.13 vs 1.24 ± 0.16, p < 0.0001). The CHB score, on the other hand, showed no relationship with the rCBF increase ratio (p = 0.775). In addition, the rCBF increase ratio did not differ between those patients with TNEs and those without (1.15 ± 0.033 vs 1.16 ± 0.037, p = 0.978). CONCLUSIONS The findings strongly suggest that the presence of the CHB sign during PODs 1-3 can be a predictor of TNEs after bypass surgery for moyamoya disease. On the other hand, presence of this sign appears to have no direct relationship with the postoperative local hyperperfusion phenomenon. Vasogenic edema can be hypothesized as the pathophysiology of the CHB sign, because the sign was transient and never accompanied by infarction in the present series.

MR screening of candidates for thrombolysis: How to identify stroke mimics?

Stroke mimics account for up to a third of suspected strokes. The main causes are epileptic deficit, migraine aura, hypoglycemia, and functional disorders. Accurate recognition of stroke mimics is important for adequate identification of candidates for thrombolysis. This decreases the number of unnecessary treatments and invasive vascular investigations. Correctly identifying the cause of symptoms also avoids delaying proper care. Therefore, this pictorial review focuses on what the radiologist should know about the most common MRI patterns of stroke mimics in the first hours after onset of symptoms. The issues linked to the accurate diagnosis of stroke mimics in the management of candidates for thrombolysis will be discussed.

A wide spectrum of variably periictal MRI abnormalities induced by a single or a cluster of seizures

BACKGROUND

Although predominantly reported in patients with status epilepticus, periictal MRI abnormalities have been reported in patients with a single or a cluster of seizures. Clinicians are often presented with a dilemma concerning the features of MRI abnormalities induced by a single or a cluster of seizures, as they may represent the effect of seizure activity rather than its structural cause.

METHODS

A retrospective review of clinical and neuroimaging charts of 14 patients diagnosed with a single or a cluster of seizure-related MR-signal changes from the database of our unit (approximately 300 patients diagnosed with a single or a cluster of seizures underwent brain-MRI within 14 days from a seizure) was conducted. Extensive clinical work-up and follow-up, ranging from 3 months to 5 years, ruled out infection or other possible causes of brain damage. Site, characteristics and reversibility of MRI changes, and association with characteristics of seizures were determined.

RESULTS

MRI showed unilateral abnormalities in 14 patients, with hyperintensities on T2-signal (12/14), fluid-attenuated inversion-recovery (FLAIR) (12/14), and restricted diffusion (6/8). Location of abnormality was cortical (4/14), subcortical (6/14), thalamus (2/14), corpus callosum (1/14), and bordering an old encephaloclastic lesion (1/14). Periictal MRI abnormalities and electroclinical findings in 10 patients showed an almost complete topographic concordance, which was not consistent in 4 patients. Reversibility of MRI changes was complete in 11 patients, partially disappeared in 1 patient, and irreversible on MRI in 2 patients.

CONCLUSIONS

A single or a cluster of seizures cannot only induce transient, variably reversible MRI brain abnormalities, but also irreversible changes. These seizure-induced MRI abnormalities pose a broad differential diagnosis; increased awareness may reduce the risk of misdiagnosis and unnecessary intervention.

Pilomotor seizures in temporal lobe epilepsy: A case report with sequential changes in magnetic resonance imaging

Piloerection is a rare ictal manifestation of temporal lobe epilepsy. The case is a 38-year-old man with acute onset of repetitive pilomotor seizures. Lacking other symptoms implicating epileptic seizures, a month passed before he was diagnosed with epilepsy. Ictal electroencephalography revealed rhythmic waves in the right temporal area. Reversible magnetic resonance imaging (MRI) abnormalities were visible in the right hippocampus, right uncus, and right amygdala. The appropriate antiepileptic drug therapy made him seizure-free, but following MRI, he showed right hippocampal atrophy one year after seizure cessation. This case is significant in that we can follow sequential MRI from onset, and it is meaningful for considering the mesial temporal area as involved with piloerection.

Corticosteroid withdrawal precipitates perilesional edema around calcified Taenia solium cysts

Calcified Taenia solium granulomas are the focus of repeated episodes of perilesional edema and seizures in 50% of persons with calcifications, history of seizures, and a positive serology for cysticercosis. The pathophysiology is unclear but recent studies suggest the edema is caused by inflammation. We report two new cases and four other published cases where cessation of corticosteroids appeared to result in recurrence or new appearance of perilesional edema around calcifications. This suggests that perilesional edema is an immune-mediated phenomenon.

Edema surrounding calcified intracranial cysticerci: clinical manifestations, natural history, and treatment

Calcified granulomas are the most common radiological finding in neurocysticercosis (10-20% of endemic populations). A small proportion serves as foci of seizure activity, which results in large numbers of persons with epilepsy. Calcified granulomas are not all the same. Some demonstrate blood-brain barrier dysfunction (magnetic resonance imaging enhancement) most likely due to the presence of inflammation, visualizable scolices, and/or gliosis. About half the patients with a recent history of seizures, positive serology, and only calcified lesions develop perilesional edema at the time of a seizure recurrence. The natural history, treatment, and pathophysiology of this phenomenon are not well studied. Episodes are usually associated with seizures or other neurological manifestations, resolve by 4-6 weeks, sometimes occur repeatedly, and usually involve a subset of the same calcifications. Treatment is supportive. Histopathological examination of one calcification associated with multiple perilesional edema episodes revealed significant inflammation and supports the concept that perilesional edema is inflammatory in nature. This most likely is due to host responses to released or newly recognized parasite antigen and/or upregulation of the host immune response. Immunosuppressive and anti-inflammatory agents may be useful in prevention and/or treatment of this phenomenon.

Boomerang sign: Clinical significance of transient lesion in splenium of corpus callosum

Transient signal abnormality in the splenium of corpus callosum on magnetic resonance imaging (MRI) is occasionally encountered in clinical practice. It has been reported in various clinical conditions apart from patients with epilepsy. We describe 4 patients with different etiologies presenting with signal changes in the splenium of corpus callosum. They were diagnosed as having progressive myoclonic epilepsy (case 1), localization-related epilepsy (case 2), hemicrania continua (case 3), and postinfectious parkinsonism (case 4). While three patients had complete involvement of the splenium on diffusion-weighted image (“boomerang sign”), the patient having hemicrania continua showed semilunar involvement (“mini-boomerang”) on T2-weighted and FLAIR image. All the cases had noncontiguous involvement of the splenium. We herein, discuss these cases with transient splenial involvement and stress that such patients do not need aggressive diagnostic and therapeutic interventions. An attempt has been made to review the literature regarding the pathophysiology, etiology, and outcome of such lesions.

Peri-ictal pseudoprogression in patients with brain tumor

Recent advances in the treatment of malignant gliomas have highlighted the fact that the appearance of new contrast-enhancing lesions on magnetic resonance imaging (MRI) is not always indicative of tumor recurrence. It has been suggested that transient seizure-related MRI changes could mimic disease progression (peri-ictal pseudoprogression [PIPG]). However, the clinical and MRI features associated with this situation have not been well described. Here, we consulted the databases of 6 institutions to identify patients with brain tumor who presented during the follow-up period transient MRI lesions wrongly suggesting tumor progression in a context of epileptic seizures. Ten patients were identified. All patients but 1 were long-term survivors who had initially been treated with radiotherapy. The PIPG episode occurred after a median interval of 11 years after radiotherapy. MRI features were highly similar across patients and consisted of transient focal cortical and/or leptomeningeal enhancing lesions that erroneously suggested tumor progression. All patients improved after adjustment of their antiepileptic drugs and transient oral corticosteroids, and MRI findings were normalized 3 months after the PIPG episode. Two patients demonstrated several seizure relapses with the same clinicoradiological pattern. After a median follow-up period of 3.5 years after the initial PIPG episode, only 1 patient presented with a tumor recurrence. In conclusion, in patients with brain tumor, especially in long-term survivors of radiotherapy, the appearance of new cortical and/or leptomeningeal contrast-enhancing lesions in a context of frequent seizures should raise the suspicion of PIPG. This phenomenon is important to recognize in order to avoid futile therapeutic escalation.

Spontaneous radiographic resolution and subsequent redemonstration of an untreated glioblastoma

The authors present the first case of spontaneous radiographic resolution and subsequent redemonstration of Gd enhancement of an untreated glioblastoma. They also review the literature on MR imaging enhancement patterns of high-grade gliomas and speculate that this phenomenon could be attributed to the dynamic biology of glioblastomas but could also represent pseudoregression following successful control of seizure activity. A 57-year-old woman presented with left-sided paresthesias and numbness. Initial Gd-enhanced MR images exhibited T2 and FLAIR signal changes in the right insular region without mass effect or contrast enhancement. Electroencephalography revealed intermittent sharp wave activity in this area. Antiepileptic medication was started, and the patient's symptoms resolved. Follow-up MR imaging 6 weeks later revealed enlargement of the lesion and contrast enhancement in the superior temporal gyrus. Consequently, the patient was scheduled for a brain biopsy. However, surgical planning MR images obtained on the day of surgery 4 weeks later showed that the enhancement had spontaneously resolved, and so the operation was cancelled. Repeat MR imaging performed 2 weeks later as a result of increased seizure frequency redemonstrated contrast enhancement. The patient then underwent a craniotomy, and final histopathology was consistent with glioblastoma.

The electroclinical-imagiological spectrum and long-term outcome of transient periictal MRI abnormalities

The electroclinical-imagiological spectrum and long-term outcome of transient periictal MRI abnormalities (TPMA) remains largely unclear. This prompted us to perform a prospective observational cohort study, including electroencephalography (EEG) and multi-sequence MRI, in 19 consecutive patients (8 female, mean age 51.7 years) with TPMA induced by convulsive and non-convulsive status epilepticus (n=14) or isolated seizures. TPMA were associated with focal, lateralized or diffuse EEG abnormalities, and were mostly focal unilateral and cortico-subcortical (n=11), less frequently cortically restricted, bilateral, hemispheric and with remote lesions (pulvinar, cerebellum); 66.7% had cortico-pial contrast enhancement and 93.7% restriction on diffusion-weighted imaging, with cortical cytotoxic edema on apparent-diffusion coefficient, only tumor-like TPMA (n=5) presenting noticeable subcortical vasogenic edema. The heterogeneity of clinical, EEG and MRI findings contributed to a 38.6% strict focal topographic concordance between them, with the more widespread findings also attributable to the time lag between studies, seizure dynamics/etiologies and cerebral reserve. At follow-up (mean duration 29.6 months, 3-120), the brain damage induced by TPMA was responsible for a high incidence of clinical and MRI sequelae (63.2%), only tumor-like/small TPMA induced by acute symptomatic seizures presenting good clinical outcomes. Our findings may contribute to a better definition and comprehension of the TPMA electroclinical-imagiological spectrum, pathophysiology and long-term outcome.