Focal cerebral magnetic resonance changes associated with partial status epilepticus

A comparison of anticonvulsant efficacy and action mechanism of Mannitol vs Phenytoin in adult rat neocortical slices

We show that, in adult rat neocortical slices, an anticonvulsant effect comparable to that of Phenytoin can be obtained through a Mannitol-induced increase in extracellular osmolarity of only 30 mOsm/L. The anticonvulsant action of extracellular hyperosmolarity has been known for decades but has not found a feasible therapeutic application, yet. A 30 mOsm/L increase in extracellular osmolarity is already utilized in neurocritical care though not as an anticonvulsant agent: the data suggest a possible effective anticonvulsant use, too, in this setting. We used multiple electrode arrays to characterize and compare the anticonvulsant mechanisms of Mannitol and Phenytoin. Phenytoin decreased the voltage, duration and spatial spread of rhythmic repetitive, ictal-like activity. In contrast, Mannitol did not significantly affect voltage, duration and spatial spread of rhythmic repetitive, ictal-like activity but rather it inhibited the rate of epileptiform discharges.

Recurrent Occipital Seizures with Transient MRI Changes

Peri-ictal magnetic resonance imaging (MRI) findings following seizure activity are a recognized phenomenon that is not well understood (Cole, 2004). Transient changes are not usually expected to be present in postictal MRI studies because of their rarity. Here, we present a unique case of peri-ictal MRI findings located in the occipital lobe, present in a 34-year-old female with recurrent occipital seizures occurring twice in four years. MRI changes completely resolved after both episodes with no residual focal damage. The peri-ictal occipital changes on MRI in this patient are unique because they have been captured on more than one occasion. Peri-ictal MRI findings are a known phenomenon with unknown pathophysiology, although attempts have been made to understand these findings. Though the MRI findings and presentation appear to be stroke-like or PRES-like, seizures should be kept in the differential for better treatment outcomes.

Stroke-like migraine attacks after radiation therapy (SMART) syndrome is not always completely reversible: a case series

We retrospectively reviewed clinical and imaging findings in 11 patients with stroke-like migraine attacks after radiation therapy (SMART) syndrome to better understand this disorder previously thought to be reversible. Six men and 5 women had complex bouts of neurologic impairment beginning, on average, 20 years after cerebral irradiation. All had characteristic, unilateral gyriform enhancement on MR imaging that developed within 2-7 days and typically resolved in 2-5 weeks. Unlike prior reports, 45% had incomplete neurologic recovery manifesting as dysphasia, cognitive impairment, or hemiparesis. The remaining 55% recovered completely over an average of 2 months. Three of 11 patients developed cortical laminar necrosis. Brain biopsies in 4 of 11 did not demonstrate a specific pathologic substrate. These additional 11 patients contribute to the understanding of variability in stroke-like migraine attacks after radiation therapy syndrome, which often but not uniformly manifests with headaches and seizures, demonstrates a typical evolution of imaging findings, and may result in permanent neurologic and imaging sequelae.

Identification of Disappearing Brain Lesions With Intraoperative Magnetic Resonance Imaging Prevents Surgery

BACKGROUND:

Typically, neurosurgery is performed several weeks after diagnostic imaging. In the majority of cases, histopathology confirms the diagnosis of neoplasia. In a small number of cases, a different diagnosis is established or histopathology is nondiagnostic. The frequency with which these outcomes occur has not been established.

OBJECTIVE:

To determine the frequency and outcome of disappearing brain lesions within a group of patients undergoing surgery for suspected brain tumor.

METHODS:

Over the past decade, 982 patients were managed in the intraoperative magnetic resonance imaging unit at the University of Calgary, Calgary, Alberta, Canada. These patients have been prospectively evaluated.

RESULTS:

In 652 patients, a brain tumor was suspected. In 6 of the 652 patients, histopathology indicated a nontumor diagnosis. In 5 patients, intraoperative images, acquired after induction of anesthesia, showed complete or nearly complete resolution of the suspected tumor identified on diagnostic magnetic resonance imaging acquired 6 ± 4 (mean ± SD) weeks previously. Anesthesia was reversed, and the surgical procedure aborted. The lesions have not progressed with 6 ± 2 years of follow-up.

CONCLUSION:

Intraoperative magnetic resonance imaging prevented surgery on 5 patients with disappearing lesions.

Thalamus lesions in chronic and acute seizure disorders

INTRODUCTION

Transient signal changes in the pulvinar have been described following status epilepticus. However, we observed persistent thalamus changes after seizures. The purpose of this study was to characterize thalamus changes in patients with seizure disorders and to correlate imaging findings with clinical features.

METHODS

We searched among 5,500 magnetic resonance imaging (MRI) exams performed in patients with seizures and identified 43 patients. The MRI scans of these patients were reviewed and correlated with clinical data.

RESULTS

We identified four patterns of thalamus lesions: (a) fluid attenuated inversion recovery-hyperintense pulvinar lesions (20 patients), as known from status epilepticus. Ten patients in this group had a status epilepticus. Among the remaining patients, three had frequent seizures and seven had sporadic seizures. Twelve patients had follow-up exams for a median of 11 months. The lesions had persisted in 11/12 cases in the last available exam and were reversible in one case only. In seven cases, cone-shaped thalamus atrophy resulted, (b) linear defects in the medial and anterior thalamus (five patients), accompanied by atrophy of the mamillary body and the fornix in patients with chronic epilepsy, (c) extensive bilateral thalamus lesions in two patients with a syndrome caused by mutation in the mitochondrial polymerase gamma, and (d) other thalamus lesions not associated with the seizure disorder (16 patients).

CONCLUSION

The spectrum of thalamus lesions in patients with seizure disorders is wider than previously reported. Postictal pulvinar lesions can persist and may result in thalamic atrophy. Linear defects in the anterior thalamus are associated with limbic system atrophy.

[Postictal MR-changes. A rare and important differential diagnosis]

BACKGROUND

Postictal MR findings are analyzed in the context of MR morphological differential diagnoses.

PATIENTS AND METHODS

Postictal MRI was performed in 11 patients. The patterns of MR changes and their differential diagnoses were analyzed.

RESULTS

Focal accentuation of signal increase in the cortex was found on T2-weighted images in 90% of these cases, pial enhancement in 70% and signal changes of the pulvinar/thalamus in 40%. The most common differential diagnoses were encephalitis, and in tumor patients carcinomatous involvement of the meninges.

CONCLUSION

Postictal MR changes vary widely and are difficult to differentiate from illnesses such as encephalitis and carcinomatosis involving the meninges. Nevertheless, knowledge of the typical pattern of postictal MR findings and the clinical course may help to avoid mistaken diagnoses.

Nonconvulsive status epilepticus manifesting as pure alexia (alexia without agraphia)

Pure alexia is a rare disorder usually caused by an ischemic or hemorrhagic stroke. We describe a case of pure alexia due to nonconvulsive status epilepticus (NCSE). This 57-year-old man presented in a hyperosmolar, nonketotic state with fluctuations in mental status and an inability to read. His EEG was diagnostic of NCSE originating from the left temporo-occipital region. MRI of the brain revealed increased FLAIR signal over the left occipitotemporal region. Following initiation of antiepileptic treatment, his neurological examination normalized concomitantly with resolution of the NCSE. A follow-up MRI scan of the brain obtained 1 month later was normal. NCSE can have unusual clinical manifestations, and a high index of suspicion is necessary to correctly diagnose these patients.

Transient postictal MRI changes in patients with brain tumors may mimic disease progression

BACKGROUND

Transient postictal imaging abnormalities in patients with non-tumor-related seizures are well documented and include fluid-attenuated inversion recovery/T2 hyperintensity and parenchymal and meningeal contrast enhancement. In contrast, transient postictal imaging abnormalities in patients with tumor-related seizures have been poorly described. Fifty percent of patients with brain tumors have a seizure during the course of their illness and are often imaged after a seizure or after a change in seizure character or frequency. Interval changes on repeat imaging can mimic disease progression or other pathologic processes.

METHODS

We describe 3 patients with brain tumors and transient postictal MRI changes that mimicked disease progression and infection.

RESULTS

Our patients demonstrated fluid-attenuated inversion recovery/T2 hyperintensity and gadolinium enhancement on MRI studies performed shortly after ictal events. These changes were suspicious for tumor progression in 2 cases and for recurrent infection in the third. Control of seizure activity resulted in resolution of these changes on scans obtained 10 to 21 days later.

CONCLUSIONS

Imaging shortly after an ictal event can potentially mislead the clinician to interpret changes as tumor or pathologic progression. Unnecessary intervention in these patients with new and suspicious imaging findings should be avoided. We recommend repeat imaging be performed in patients with brain tumors and seizures several weeks after seizure control if clinically feasible. Further research is needed to delineate the time course of seizure-induced MRI changes.

Anaplastic Astrocytoma Presenting as Reversible Posterior Leukoencephalopathy Syndrome

We report a 60-year-old man with grade III astrocytoma, who presented with status epilepticus. The initial MRI did not demonstrate typical findings of an astrocytoma but rather showed reversible posterior leukoencephalopathy syndrome (RPLS). N-Isopropil-p-[I] iodoamphetamine single photon emission computed tomography (SPECT) demonstrated hyperperfusion in this area. A brain tumor should be considered and the patient carefully followed by MRI, even if the MRI white matter lesion pattern suggests RPLS. This is especially relevant in the presence of atypical findings for RPLS on SPECT.

Focal transient lesion in the splenium of the corpus callosum in three non-epileptic patients

INTRODUCTION

We analyzed the imaging features of transient focal lesions in the splenium of the corpus callosum (SCC) in non-epileptic patients receiving antiepileptic drugs (AEDs).

METHODS

We identified signal abnormalities in the SCC in three non-epileptic patients, all of them receiving AEDs. We examined two of these patients with multiplanar magnetic resonance (MR) imaging using 1.0-T equipment including fluid-attenuated inversion recovery (FLAIR), T2-weighted (TSE) and T1-weighted (SE) sequences before and after injection of contrast agent. The third patient was studied using 1.5-T equipment with the same sequences. Additionally, a T1 SE sequence with a magnetization transfer contrast pulse off resonance (T1 SE/MTC), diffusion-weighted imaging (EPI-DWI) and apparent diffusion coefficient (ADC) maps were obtained.

RESULTS

We observed an identical pattern of imaging abnormalities in all patients characterized by round lesions, hyperintense on FLAIR and hypointense on T1 SE images, located in the central portion of the SCC. One lesion showed homogeneous gadolinium enhancement and perilesional vasogenic edema. This particular lesion showed restricted diffusion confirmed on the ADC map. This pattern was considered consistent with focal demyelination. Follow-up MR examinations showed complete disappearance or a clear reduction in lesion size. All patients had been treated with AEDs, but they did not show any clinical signs of toxicity, interhemispheric symptoms, or abnormal neurological findings (including seizures).

CONCLUSION

We believe that our MR findings might be interpreted as transient lesions related to AED toxicity. They presumably resulted from focal demyelination in the central portion of the SCC.

Prolonged postictal psychosis with forced normalization (Landolt) in temporal lobe epilepsy

We report two patients with temporal lobe epilepsy who developed prolonged episodes of postictal psychosis (12 weeks) following a bout of seizures and a lucid interval. No drug toxicity was noted, and no recurrent or continuous seizures were observed during their prolonged psychotic episodes. Repeated EEGs during the period of psychosis showed that their habitual focal epileptiform abnormalities had disappeared. Responses to neuroleptic treatments were not remarkable. Their psychotic symptoms gradually dispelled after their epileptiform abnormalities reappeared. These observations may suggest possible overlapping mechanisms between a prolongation of psychosis and suppression of epileptiform discharges on a scalp EEG.

Multimodal longitudinal imaging of focal status epilepticus

BACKGROUND

Little is understood about the evolution of structural and functional brain changes during the course of uncontrolled focal status epilepticus in humans.

METHODS

We serially evaluated and treated a nine-year-old girl with refractory focal status epilepticus. Long-term EEG monitoring, MRI, MRA, SPECT, intraoperative visualization of affected cortex, and neuropathological examination of a biopsy specimen were conducted over a three year time span. Imaging changes were correlated with simultaneous treatment and EEG findings.

RESULTS

The EEG monitoring showed almost continuous spike discharges emanating initially from the right frontocentral area. These EEG abnormalities were intermittently suppressed by treatment with anesthetics. Over time, additional brain areas developed epileptiform EEG abnormalities. Serial MRI studies demonstrated an evolution of changes from normal, through increased regional T2 signal to generalized atrophy. An MRA demonstrated dilatation of the middle cerebral artery stem on the right compared to the left with a broad distribution of flow-related enhancement. An 18FDG-PET scan showed a dramatically abnormal metabolic profile in the same right frontocentral areas, which modulated in response to treatment during the course of the illness. A right frontotemporal craniotomy revealed a markedly hyperemic cortical focus including vascular shunting. A sample of resected cortex showed severe gliosis and neuronal death.

CONCLUSIONS

The co-registration of structural and functional imaging and its correlation with operative and pathological findings in this case illustrates the relentless progression of regional and generalized abnormalities in intractable focal status epilepticus that were only transiently modified by exhaustive therapeutic interventions. Increased flow through large vessels appeared to be shunted and did not translate into increased microvascular perfusion.

Diffusion changes suggesting predominant vasogenic oedema during partial status epilepticus

Diffusion-weighted imaging (DWI) has demonstrated a focal area of cytotoxic oedema during partial status epilepticus (PSE). However, vasogenic oedema related to the breakdown of the blood-brain-barrier (BBB) and ictal hyperperfusion could be the predominant DWI findings in the epileptogenic area during PSE. We report a case of PSE with ictal aphasia, right hemiparesis, and repetitive focal motor seizure of the right side. T2-weighted image (T2WI) and apparent diffusion coefficient (ADC) maps obtained during PSE showed an increased signal in the left temporo-parietal area, indicative of vasogenic oedema. EEG documented the ictal activities and single photon emission tomography (SPECT) showed asymmetrically increased perfusion in the corresponding area. Follow-up T2WI, DWI, and ADC maps obtained 3 months later showed the disappearance of the previous abnormalities. However, T2WI showed cortical atrophy and newly developed white matter changes in the corresponding area. This case shows that DWI findings may be variable during PSE, dependent on the predominance of cytotoxic and vasogenic oedema.

Calcific neurocysticercosis and epileptogenesis

Neurocysticercosis is responsible for increased rates of seizures and epilepsy in endemic regions. The most common form of the disease, chronic calcific neurocysticercosis, is the end result of the host's inflammatory response to the larval cysticercus of Taenia solium. There is increasing evidence indicating that calcific cysticercosis is not clinically inactive but a cause of seizures or focal symptoms in this population. Perilesional edema is at times also present around implicated calcified foci. A better understanding of the natural history, frequency, epidemiology, and pathophysiology of calcific cysticercosis and associated disease manifestations is needed to define its importance, treatment, and prevention.

Transient cortical abnormalities on magnetic resonance imaging after status epilepticus

INTRODUCTION

Transient neuroimaging findings associated with seizure activity have received relatively little attention in the neurosurgical literature. These abnormalities may mimick neoplastic or ischemic changes on magnetic resonance imaging (MRI), possibly leading to additional studies and surgical treatment.

CASE DESCRIPTION

A 17-year-old right-handed male was transferred to emergency room in status epilepticus. A MRI obtained 5 months before admission was negative. On the day of admission, he had multiple intermittent upper-left extremity partial seizures and prolonged secondary generalized seizures. An electroencephalogram (EEG) showed frequent epileptiform discharges over the right hemisphere posteriorly. A MRI study performed 2 days after admission revealed non-hemorrhagic abnormalities involving the right occipital region that were hyperintense on fluid-attenuated inversion recovery (FLAIR) and T2 weighted sequences. The apparent diffusion coefficient map was unremarkable. Follow-up MRIs, 3 and 11 months after admission, showed complete resolution of these lesions.

CONCLUSION

Imaging findings after status epilepticus may raise suspicion of ischemic or neoplastic lesions. These findings may be reversible. Further follow-up imaging may prevent unnecessary intervention.

Long-term behavioral and morphological consequences of nonconvulsive status epilepticus in rats

The aims of the present study were to ascertain whether nonconvulsive status epilepticus (NCSE) could give rise to long-term behavioral deficits and permanent brain damage. Two months after NCSE was elicited with pilocarpine (15 mg/kg i.p.) in LiCl-pretreated adult male rats, animals were assigned to either behavioral (spontaneous behavior, social interaction, elevated plus-maze, rotorod, and bar-holding tests) or EEG studies. Another group of animals was sacrificed and their brains were processed for Nissl and Timm staining as well as for parvalbumin and calbindin immunohistochemistry. Behavioral analysis revealed motor deficits (shorter latencies to fall from rotorod as well as from bar) and disturbances in the social behavior of experimental animals (decreased interest in juvenile conspecific). EEGs showed no apparent abnormalities. Quantification of immunohistochemically stained sections revealed decreased amounts of parvalbumin- and calbindin-immunoreactive neurons in the motor cortex and of parvalbumin-positive neurons in the dentate gyrus. Despite relatively inconspicuous manifestations, NCSE may represent a risk for long-term deficits.

Changes on diffusion-weighted MRI with focal motor status epilepticus: case report

Transient imaging abnormalities, including changes on diffusion-weighted imaging (DWI), may be seen in focal status epilepticus. The changes on DWI provide am insight into the pathophysiology. We report a 53-year-old man with focal motor status epilepticus involving the left hand, arm and face with focal slowing on EEG. The apparent diffusion coefficients (ADC) were higher in the affected hemisphere than on the other side. At 10 days and 6 weeks after the end of the seizures, we saw normal ADCs and atrophy of the affected hemisphere. We conclude that the MRI findings indicate both cytotoxic and vasogenic oedema during seizure activity and subsequent loss of brain parenchyma.

Brain diffusion after single seizures

PURPOSE

Diffusion-weighted magnetic resonance imaging (DWI) after focal status epilepticus has demonstrated focal alterations of the apparent diffusion coefficient (ADC) in the epileptogenic zone. We hypothesized that localized dynamic alterations of brain diffusion during the immediate postictal state will be detectable by serial DWI and correlate with the epileptogenic zone.

METHODS

Nine adult patients (four men, five women) with medically intractable epilepsy were prospectively examined with a total of 25 DWI scans taken 2-210 min after a seizure.

RESULTS

The interictal ADC was significantly (p < 0.05) elevated in the ictogenic hippocampus in all patients with temporal lobe epilepsy. The following postictal changes of the ADC were seen: (a) decreases by maximally 25-31%, which were most pronounced in the epileptogenic zone (n = 2); (b) generalized ADC changes after generalized seizures (n = 1) or prolonged complex partial seizures (n = 2); (c) no major changes after short-lived seizures or if the time to first DWI scan was >15 min or both (n = 3); and (d) widespread bilateral ADC increases after a flumazenil-induced seizure (n = 1).

CONCLUSIONS

ADC changes seen during serial postictal DWI are complex and appear to reflect origin and spread of the preceding seizure. A delineation of the epileptogenic zone appears to be possible only in complex-partial seizures of >60 s duration that do not secondarily generalize.

Transient postictal magnetic resonance imaging abnormality of the corpus callosum in a patient with epilepsy. Case report and review of the literature

Transient neuroimaging abnormalities associated with seizure activity have received little attention in the literature. The authors report a focal magnetic resonance (MR) imaging abnormality of the corpus callosum in a patient following a secondary generalized seizure. A 27-year-old right-handed man presented with a history of medically refractory partial seizures since the age of 1 year. The results of an MR imaging study obtained 4 months prior to the patient undergoing video-electroencephalography monitoring were unremarkable. After the patient discontinued all antiepileptic medications, a secondary generalized seizure of right temporal origin was recorded. Five days later, repeated MR imaging revealed a nonenhancing 14 x 11-mm ovoid hyperintense lesion in the splenium of corpus callosum. The patient was asymptomatic, and his neurological and neurocognitive examinations remained unremarkable. Follow-up MR imaging 5 weeks and 1 year later demonstrated near-complete resolution of the lesion. Benign and transient abnormalities in the splenium can occur as a periictal phenomenon. A high index of suspicion and follow-up imaging may prevent further unwarranted intervention.

Unilateral striatal damage following status epilepticus of ipsilateral frontal lobe origin

A 35-year-old man with an old contusional haematoma in the right frontal lobe developed status epilepticus (SE) of right frontal origin. On magnetic resonance (MR) images 10 days after SE, the right striatum showed signal enhancement with Gd-DTPA administration. Subsequent MR imaging 1 month later indicated prolonged T1 and T2 relaxation times in the right striatum. Prolonged seizure activity in the frontal lobe may have induced excitatory neurotoxicity in the ipsilateral striatum, with occurrence of delayed neuronal damage as a result.

Seizures associated with calcifications and edema in neurocysticercosis

We describe eight cases of pediatric patients whose neuroimages performed after seizures revealed abnormalities that were compatible with edema surrounding calcified lesions and which disappeared in subsequent examinations.

Ketotic hyperglycemia and epilepsia partialis continua

Epilepsia partialis continua (EPC) may occur during nonketotic hyperglycemia but has not been described with diabetic ketoacidosis. The authors report a patient with EPC associated with ketotic hyperglycemia. Brain MRI showed two areas of abnormal signal intensity in the left precentral gyrus and in the right cerebellar hemisphere. Hyperglycemia may reduce seizure threshold because of the increase in gamma-aminobutyric acid metabolism and may trigger epileptic discharges.

Delayed, transient neurological deterioration after mild head injury--case report

A 16-year-old boy presented with delayed, transient neurological deterioration 18 days after mild head injury. Left hemiparesis and left homonymous hemianopsia appeared after right frontal contusional and mild subdural hematomas subsided. Neuroimaging examinations including cerebral angiography, magnetic resonance imaging, and single photon emission computed tomography showed vasodilation and hyperemia in the right cerebral hemisphere. The present case is not typical of acute "juvenile head trauma syndrome," but may represent a possible pathophysiology of the delayed type of transient neurological deterioration after mild head injury.

Transient MRI abnormalities associated with partial status epilepticus: a case report

We report the case of an 18-year-old woman who presented a long-lasting cluster of partial seizures, and MRI cortical abnormalities localized in the left parietal lobe. The MRI changes correlated with the site of the epileptogenic focus, and disappeared within 2 weeks. The recognition of these reversible MRI abnormalities, which are presumably due to a temporary alteration of blood-brain barrier in the epileptogenic zone with subsequent edema, and are not associated with any underlying organic conditions, is extremely useful in the medical management of the patient and allows to avoid other invasive diagnostic procedures.

Transient lesion in the splenium of the corpus callosum: three further cases in epileptic patients and a pathophysiological hypothesis

OBJECTIVE

Focal lesions limited to the splenium of the corpus callosum (SCC) are rare and little is known about their aetiology. Three patients were examined for presurgical evaluation in epilepsy with a transient lesion in the SCC and a pathophysiological hypothesis is presented.

METHODS

Three patients were identified with a circumscribed lesion in the centre of the corpus callosum. Follow up MRI was performed, the medical records examined retrospectively, and the literature reviewed.

RESULTS

The patients showed identical lesions in the SCC with reduced T1 and increased T2 signal intensity and an unaffected marginal hemline of a few mm. Patients were asymptomatic and control MRIs showed complete normalisation within 2 months. Patients had been treated with antiepileptic drugs (AEDs) without signs of toxicity. In all patients AEDs were rapidly reduced for diagnostic purposes, but only one had psychomotor seizures, 5 days before imaging.

CONCLUSIONS

A transient lesion in the SCC has so far only been described in 13 patients with epilepsy and has been interpreted either as reversible demyelination due to AED toxicity or transient oedema after secondary generalised seizures. The data confirm neither of these hypotheses. A transient lesion in the SCC seems to be a non-specific end point of different disease processes leading to a vasogenic oedema. This suggests, in these patients, a multifactorial pathology triggered by transient effects of AEDs on arginine vasopressin and its function in fluid balance systems in a condition of vitamin deficiency. The complete and rapid reversibility in all cases without specific intervention is emphasised and any invasive diagnostic or therapeutic approach is discouraged.

An animal model of nonconvulsive status epilepticus: a contribution to clinical controversies

PURPOSE

To characterize electroencephalographic and behavioral effects as well as electrophysiologic and morphologic consequences of a subconvulsive dose of pilocarpine in lithium chloride-pretreated rats.

METHODS

Pilocarpine (15 mg/kg) was administered intraperitoneally to adult rats pretreated with lithium chloride (3 mEq/kg, i.p.). Behavior was observed for 2 h and videotaped in three consecutive sessions. At the same time, EEG was recorded from the sensorimotor cortex and the dorsal hippocampus. Threshold intensities of currents necessary to elicit hippocampal afterdischarges were determined 24 h and 1 week after the pilocarpine administration. The brains were histologically examined 1 week after pilocarpine administration using Nissl stain.

RESULTS

Pilocarpine induced time-limited nonconvulsive status epilepticus (NCSE). Epileptic EEG activity concurrent with prominent behavioral features was observed both in the neocortex and, predominantly, in the hippocampus. No changes in afterdischarge thresholds were observed in the dorsal hippocampus 24 h and 1 week after NCSE. One week after NCSE, seizure-related brain damage was found mainly in the motor neocortical fields.

CONCLUSIONS

Pilocarpine-induced NCSE in rats strongly resembles a short-term human complex partial status epilepticus. Our animal model is suitable for studying the possible adverse effects of prolonged nonconvulsive seizures.

Nonconvulsive status epilepticus in rats: impaired responsiveness to exteroceptive stimuli

An animal model of human complex partial status epilepticus induced by lithium chloride and pilocarpine administration was developed in our laboratory. The objective of the study was to provide a detailed analysis of both ictal and postictal behavior and to quantify seizure-related morphological damage. In order to determine the animal's responsiveness to either visual or olfactory stimuli, adult male rats were submitted to the following behavioral paradigms: the object response test, the social interaction test, and the elevated plus-maze test. The rotorod test was used to evaluate motor performance. Two weeks after status epilepticus, brains were morphologically examined and quantification of the brain damage was performed. Profound impairment of behavior as well as responsiveness to exteroceptive stimuli correlated with the occurrence of epileptic EEG activity. When the epileptic EEG activity ceased, responsiveness of the pilocarpine-treated animals was renewed. However, remarkable morphological damage persisted in the cortical regions two weeks later. This experimental study provides support for the clinical evidence that even nonconvulsive epileptic activity may cause brain damage. We suggest that the model can be used for the study of both functional and morphological consequences of prolonged nonconvulsive seizures.

MRI volumetry of the hippocampus, amygdala, entorhinal cortex, and perirhinal cortex after status epilepticus

Neuronal damage has been observed in the medial temporal lobe of both humans and animals following status epilepticus. The aim of the present study was to investigate the occurrence of medial temporal lobe damage in status epilepticus patients treated in hospital with a predetermined protocol and to assess whether the changes progress in a long-term follow-up. The volumes of the hippocampus, amygdala, entorhinal and perirhinal cortices were measured using magnetic resonance imaging (MRI) in nine adult patients with status epilepticus 3 weeks, 6 and 12 months after the insult. The control group included 20 healthy subjects. The etiology of status epilepticus was an acute process in one patient and a chronic process in eight cases. The mean duration of secondarily generalized tonic-clonic status epilepticus episodes was 1 h and 44 min. Volumetric MRI indicated that none of the patients developed marked volume reduction in the hippocampus, amygdala, or the entorhinal and perirhinal cortices during the 1-year follow-up period. Status epilepticus does not invariably lead to a progressive volume reduction in the medial temporal lobe structures of adult patients treated promptly in hospital with a predetermined protocol for rapid cessation of seizure activity.

[Status epilepticus with confusional symptomatology]

Non-convulsive confusional status epilepticus (NCSE) is classically separated into two forms on the basis of the ictal EEG, i.e., absence status (AS) and complex partial status epilepticus (CPSE). The diagnosis is difficult on the basis of clinical semiology alone, and requires emergency EEG investigation. Absence status, or 'petit mal' status, is a polymorphic condition that can complicate many epileptic syndromes, and is the most frequently encountered form of NCSE. It is characterized by confusion of varying intensity, associated in 50% of cases with bilateral periocular myoclonias. The EEG shows ictal generalized paroximal activity; normalization is obtained after benzodiazepine injection. In AS, there is a significant nosographic heterogeneity. Four groups can be distinguished: i) typical AS occurs in the context of a generalized idiopathic epilepsy; ii) atypical AS occurs in patients with symptomatic or cryptogenic generalized epilepsies; iii) 'de novo' AS (of late onset) is characterized by toxic or metabolic precipitating factors in middle-aged subjects with no previous history of epilepsy; iv) AS with focal characteristics occurs in subjects with a pre-existing or newly diagnosed partial epilepsy, mostly of extra-temporal origin. The majority of cases are in fact transitional forms between these four groups. CPSE is characterized by continuous or rapidly recurring complex partial seizures which may involve temporal and/or extratemporal regions. Cyclic disturbance of consciousness is characteristic of CPSE of temporal lobe origin, which requires vigorous treatment to prevent recurrence or cognitive sequelae. CPSE of frontal lobe origin is a diagnostic challenge: it is rare, the symptoms are unusual, and the patients should be documented extensively. A focal frontal lesion is revealed in one-third of cases.

Reversible magnetic resonance imaging abnormalities in dogs following seizures

Reversible magnetic resonance (MR) imaging lesions have been described in humans following seizures. This condition has not yet been reported in animals. This paper describes reversible abnormalities identified in 3 dogs using MR imaging that was performed initially within 14 days of the last seizure and follow-up imaging that was performed after 10 to 16 weeks of anticonvulsant therapy. All three dogs had lesions in the piriform/temporal lobes, characterized by varying degrees of hyperintensity on T2-weighted images and hypointensity on T1-weighted images. In one dog, contrast enhancement was evident. On reevaluation, partial resolution occurred in all 3 dogs. In a fourth animal with an olfactory meningioma, similar appearing lesions in the temporal cortex and right and left piriform lobes were identified after seizure activity. A surgical biopsy of the temporal cortex and hippocampus was performed and edema, neovascularization, reactive astrocytosis, and acute neuronal necrosis were evident. These histologic findings are similar to those reported in humans with seizures. Recognizing the potential occurrence of reversible abnormalities in MR images is important in developing a diagnostic and therapeutic plan in canine patients with seizures. Repeat imaging after seizure control may help differentiate between seizure-induced changes and primary multifocal parenchymal abnormalities.

Edema associated with calcified lesions in neurocysticercosis

OBJECTIVE

To determine serial MRI and CT abnormalities around calcified cysts due to cysticercosis in previously treated patients during periods of seizure activity.

BACKGROUND

Some patients with calcified lesions due to cysticercosis have seizures. How and why seizures occur in this setting are unknown.

METHODS

Three patients with known, treated cysticercosis were studied prospectively by serial MRI and CT before, during, and after seizure activity.

RESULTS

All three patients demonstrated edema surrounding calcified lesions. Two of three patients had repeated episodes involving the same calcified lesions, and their symptoms corresponded to the location of the lesion. Enhancement was present in the lesions demonstrating edema, but was also present surrounding other nonsymptomatic calcified lesions.

CONCLUSIONS

Perilesional edema surrounding calcified lesions due to cysticercosis occurs in some patients at the time of seizure activity. Repeated seizure episodes tend to be associated with the same lesions. Although the mechanisms involved are unknown, long-term antiseizure medication is likely indicated in these patients. Current evidence does not support the use of specific antiparasitic treatment in these patients.

1H MR spectroscopy in patients with mesial temporal epilepsy

The study provides a review of the basic examination procedures and results of proton magnetic resonance spectroscopy (1H MRS) in patients suffering from mesial temporal lobe epilepsy (MTLE). The source of seizures in MTLE is most often an epileptogenic focus secondary to hippocampal sclerosis. 1H MRS currently plays an important role in the non-invasive diagnosis of this type of epileptogenic lesion. The decisive 1H MRS parameter characterizing an epileptogenic lesion is a statistically significantly decreased value of N-acetylaspartate levels compared with control values, most often associated with a decrease in the ratios of the intensities of NAA/Cr, NAA/Cho and NAA/(Cr + Cho) signals. Moreover, MRS makes it possible to distinguish bilateral involvement of mesial temporal structures typically associated with a bilateral decrease in the levels of metabolites and/or their ratios. As regards other metabolic compounds which play an important role in the pathobiochemistry of epilepsy, MRS is employed to study the action of gamma-aminobutyric acid (GABA), inositol, lactate, glutamine, and glutamate, the clinical function of which has not been fully clarified as yet. It is in this context that one should consider the application of 1H MRS in evaluating the action of some new anti-epileptic agents affecting excitatory and inhibitory amino acids. There is no doubt that in vivo 1H MRS, along with other imaging methods, has made a significant contribution to the clinical and biochemical description of epileptic seizures and has assumed a prominent position among the techniques of pre-operative examination in epileptic surgery.

Reversible focal MRI abnormalities due to status epilepticus. An EEG, single photon emission computed tomography, transcranial Doppler follow-up study

We demonstrate clinical data and findings of MRI, transcranial Doppler (TCD), single photon emission computed tomography (SPECT) and electroencephalography (EEG) in an 8 month follow-up study of a 15 year old girl who developed focal status epilepticus with sensory and visual illusions. EEG showed right temporal and occipital seizure activity and attenuation of the alpha activity with right predominance. MRI showed a right temporo-parietal hyper signal on the T2 weighted images involving the cortex with sulcal effacement. MRI-angiography suggested insufficient flow in the right transverse sinus. TCD detected an elevated flow velocity in the ipsilateral middle cerebral artery during status epilepticus, corresponding to an increased perfusion of the epileptic area revealed by SPECT. After normalization of the TCD finding, the MRI detected persistent cortical abnormality beyond the 70th day after admission. MRI normalized on the 103rd day of follow-up. Serial EEG frequency analysis demonstrated the recovery of alpha peak frequency on the left side, but the attenuation of rhythmic signals remained persistent on the right. In our case, the restitution of postictal EEG lag behind the consolidation of MRI signal abnormality.

Magnetic resonance imaging evidence of hippocampal injury after prolonged focal febrile convulsions

Magnetic resonance imaging (MRI) was performed after complex febrile convulsions (CFCs) in 27 infants. Definite MRI abnormalities were seen in 6 of the 15 infants with focal or lateralized CFCs and in none of the 12 infants with generalized CFCs. In 2 of the 6 infants with lateralized CFCs and abnormal MRIs, the MR images showed preexisting bilateral hippocampal atrophy consistent with the history of perinatal insults in these infants. However, the remaining 4 infants with MRI abnormalities and lateralized CFCs had significantly longer seizures than other infants and had MRI changes suggesting acute edema with increased hippocampal T2-weighted signal intensity and increased volume predominantly in the hippocampus in the hemisphere of seizure origin. Of those with acute edema, 1 had electrographical seizure activity recorded in the temporal region and another had a choroid fissure cyst displacing the affected hippocampus; both infants had follow-up MRIs showing that hippocampal atrophy had developed. These patients demonstrate that prolonged and focal CFCs can occasionally produce acute hippocampal injury that evolves to hippocampal atrophy. Finally, evidence of preexisting hippocampal abnormalities in several infants and electrographical temporal lobe seizure activity in 1 suggests the possibility that CFCs actually originated in the temporal lobes in some patients.

Neuroimaging in epilepsy

Neuroimaging techniques have improved the understanding, diagnosis, and management of epilepsy. By providing excellent structural information, MRI is the technique of choice in evaluating patients with epilepsy. Functional imaging techniques, including MR spectroscopy, functional MRI, positron emission tomography, and single photon emission CT, permit noninvasive assessment of the epileptic substrate, its functional status, and neuroreceptors. The MRI-based techniques will potentially assume a greater role in the cost-effective workup of the patient. Currently, newer techniques such as magnetoencephalography, magnetic source imaging, and optical imaging are research tools.

Structural consequences of status epilepticus demonstrated with serial magnetic resonance imaging

OBJECTIVES

To investigate MRI changes during tonic-clonic and focal motor status epilepticus.

MATERIAL AND METHODS

Serial MRI-investigations with saggital, coronal and axial spin-echo (SE) T1-weighted 500/15 (repetition time [TR] msec/echo time [TE] msec) with and without application of gadolinium-DTPA, proton-density-SE 2100/30 and SE T2-weighted 2100/90 images. Correlation with seizure frequency and general clinical state and by using constant EEG recordings as well as video-EEG monitoring.

RESULTS

Initially, images were normal but several days after onset of status epilepticus focal hyperintensive signal changes on T2-weighted images consistent with focal oedema were seen. The oedema produced a local mass effect as demonstrated with angiography. These changes occurred at a time when there were massive epileptic discharges registered by EEG monitoring in both cases. On subsequent images the oedema resolved but atrophy in combination with a high signal on T2-weighted images suggestive of gliosis were noted in identical regions. In the 1st case it could not completely be ruled out that the signal changes were caused by an encephalitis. However, the signal changes occurred in close time correlation with the epileptic seizure activity rendering the assumption less likely that the signal changes were caused by the encephalitis. In the 2nd case the signal changes could not be attributed to cortical dysplasia or any other condition than the epileptic activity itself.

CONCLUSION

Prolonged epileptic seizure activity may cause neuronal damage associated with a typical pattern of MRI signal changes.

Reversible MRI lesions after seizures

After generalized or partial seizures, transient lesions may appear on magnetic resonance (MR) images. The mechanisms of MR changes might be a defect in cerebral autoregulation and blood-brain permeability. We report a patient with partial and secondary generalized tonic-clonic seizures. After her first seizure which was generalized tonic-clonic in nature, we detected multiple high signal intensities over the frontal cortical area on proton density images which were enhanced with gadolinium on T1-weighted images. The first and repeated EEGs showed no abnormalities or epileptic discharges. We started carbamezapine (600 mg/d) and excluded systemic diseases like vasculitis, infections, aetiological factors causing cerebrovascular diseases. In the follow-up, she was seizure free under antiepileptic therapy and no other neurological deficit. Repeated MR scans after 24 months from her first seizure revealed no pathologic signal intensities. Although the pathophysiology is unknown, recognition of reversible lesions helps diagnostic and therapeutic approaches to abnormal MR findings after seizures.

Status epilepticus

Generalised convulsive status epilepticus is a medical emergency. Knowledge of the pathophysiology of status epilepticus and the pharmacology of the medications used to treat it allow one to devise a rational protocol for management. Anticipation of medical complications facilitates intervention when required. Prognosis depends largely on the underlying causes.

Severe transitory encephalopathy with reversible lesions of the claustrum

Reversible bilateral lesions of the claustrum and external capsule in a 12-year-old girl suffering from a severe, transitory encephalopathy are reported. After a prodromal stage of feeling uncomfortable a sudden onset of status epilepticus occurred, followed by recurrent complex partial and myoclonic seizures for 3 weeks, with psychotic symptoms and temporary loss of vision, speech and hearing. After treatment with phenytoin the patient became free of seizures and recovered completely without neurological deficit. The initial cranial CT was normal; however, cranial MRI 7 days later showed bilateral selective lesions of the claustrum and external capsule, which disappeared completely 5 weeks later. The aetiology of these lesions remains obscure; repeated cerebrospinal fluid and blood tests were negative for herpes simplex virus and other infectious agents. The clinical and radiological improvement were concomitant. This may indicate a functional disturbance of the claustrum grey matter, rather than lesions of the white matter of the external and extreme capsules.

Localized cerebellar hypometabolism in patients with complex partial seizures

PURPOSE

We sought to determine the cause of cerebellar dysfunction in epilepsy and whether this dysfunction was directly related to seizures.

METHODS

Cerebellar metabolism was evaluated in 48 patients with a well-defined region of seizure onset and with corresponding hypometabolism. Regions of interest (ROI) were drawn according to a standardized template. If the ROI/nonepileptogenic cortex count rate ratio was outside the 95% confidence interval (CI) of controls, the ROI was defined as abnormal. The ratios from cerebellar hemispheres (defined as ipsi- or contralateral to the seizure onset region), were compared among controls (n = 8); patients who had seizure onsets and corresponding hypometabolism mesially in a temporal lobe (patient group 1, n = 19); patients whose seizures had onset mesially in a temporal lobe but spread rapidly to the ipsilateral frontal lobe and who had hypometabolism both in the affected temporal lobe and frontal lobe (patient group 2, n = 23); and patients who had seizure onsets and corresponding hypometabolism in the frontal lobe (patient group 3, n = 6).

RESULTS

Significant hypometabolism was noted in the contralateral cerebellum of patients in group 2 and 3 [p = 0.007 and p = 0.008, respectively; two-way analysis of variance (ANOVA)]. In contrast, patients in group 1 tended to have lower values in the ipsilateral cerebellum (p = 0.057).

CONCLUSIONS

The observed cerebellar changes are consistent with animal data showing that cerebellar connections to frontal lobes are numerous and crossed, whereas the connections to mesial temporal lobes are less abundant, bilateral, with an ipsilateral predominance. The difference between the two groups of patients with mesial temporal seizures suggests that cerebellar dysfunction in partial epilepsy, at least to a certain extent, is related to mechanisms involved in seizure generation and spread.

Magnetic resonance imaging and spectroscopy findings after focal status epilepticus

The etiology of cerebral abnormalities after focal status epilepticus (SE) is unknown. Possible causes include hypoxia and the excessive release of excitatory amino acids. Magnetic resonance imaging (MRI) of a 21-year-old patient with "cryptogenic" continuous motor seizures showed swelling and signal hyperintensity of the contralateral parietotemporal cortex, the thalamus, and the ipsilateral cerebellum on T2-weighted images. These regions are connected by glutamatergic pathways. Proton magnetic resonance spectroscopy (MRS) of the cortical lesion yielded a signal peak at the resonance frequency of 2.29 ppm, suggesting a focal increase of glutamate or its degradation product glutamine. At 3-month follow-up, structural alterations had disappeared, but the N-acetyl-aspartate/choline ratio was still reduced in the previously abnormal area. These findings are the first to demonstrate the contribution of MRS to pathophysiologic studies of focal SE in humans and, in combination with the pattern of imaging abnormalities, support a major role of glutamate for seizure-related brain damage.

Neuron-specific enolase is increased after nonconvulsive status epilepticus

Serum neuron-specific enolase (s-NSE), a marker of brain injury and acute seizures, was increased in 2 patients with nonconvulsive SE. Neither patient had an acute neurologic insult other than nonconvulsive SE (NCSE) accounting for s-NSE changes. Increase in s-NSE provides further in vivo evidence of transient brain injury after NCSE.

Reversible MRI abnormalities following seizures

We describe eight patients with reversible MRI changes following seizures. The patients were mostly young with a serious underlying medical problem; MRI abnormalities were localized primarily in the posterior vascular boundary zones. A likely mechanism for these lesions is edema secondary to disruption in the blood-brain barrier. Recognition of the transient radiologic changes may aid in the diagnostic and therapeutic management of seizures.