Is High-Frequency Activity at Seizure Onset Inhibitory? A Stereoelectroencephalographic Study of Motor Cortex Seizures

OBJECTIVE

In the era of stereoelectroencephalography (SEEG), many studies have been devoted to understanding the role of interictal high-frequency oscillations. High-frequency activity (HFA) at seizure onset has been identified as a marker of epileptogenic zone. We address the physiological significance of ictal HFAs and their relation to clinical semiology.

METHODS

We retrospectively identified patients with pure focal primary motor epilepsy. We selected only patients in whom SEEG electrodes were optimally placed in the motor cortex as confirmed by electrical stimulation. Based on these narrow inclusion criteria, we extensively studied 5 patients (3 males and 2 females, mean age = 22.4 years) using time-frequency analysis and time correlation with motor signs onset.

RESULTS

A total of 157 analyzable seizures were recorded in 5 subjects. The first 2 subjects had tonic or clonic semiology with rare secondary generalization. Subject 3 had atonic onset followed by clonic hand/arm flexion. Subject 4 had clusters of tonic and atonic facial movements. Subject 5 had upper extremity tonic movements. The median frequency of the fast activity extracted from the Epileptogenic Zone Fingerprint pipeline in the first 4 subjects was 76 Hz (interquartile range = 21.9Hz). Positive motor signs did not occur concomitantly with high gamma activity developing in the motor cortex. Motor signs began at the end of HFAs.

INTERPRETATION

This study supports the hypothesis of an inhibitory effect of ictal HFAs. The frequency range in the gamma band was associated with the direction of the clinical output effect. Changes from inhibitory to excitatory effect occurred when discharge frequency dropped to low gamma or beta. ANN NEUROL 2024;95:1127-1137.

[FOCAL MOTOR SEIZURES AND STATUS EPILEPTICUS PROVOKED BY MIRTAZAPINE]

The seizure-provoking effect of the tetracyclic antidepressant mirtazapine is not a well-known adverse effect of the drug. The authors report on a 39-year-old non-epileptic patient who had been treated for depression with the usual daily dose of mirtazapine. Having increased the daily dose of the drug from 30 to 45 milligrams he experienced a few clonic seizures of the right lower limb. This symptom and insomnia erroneously intended the patient to further increase the daily dose of mirtazapine, which immediately resulted in the evolution of focal clonic status epilepticus in the same limb. After admission, this condition was recorded by video-EEG and abolished by intravenous administration of levetiracetam after the intravenous clonazepam had been ineffective. Discontinuation of mirtazapine and administration of carbamazepine resulted in completely seizure-free state that persisted even after carbamazepine treatment was terminated. The clinical and laboratory data indicate the seizure-provoking effect of mirtazapine in the reported case.

Applicability of nTMS in locating the motor cortical representation areas in patients with epilepsy

BACKGROUND

Transcranial magnetic stimulation (TMS) is increasingly used for non-invasive functional mapping in preoperative evaluation for brain surgery, and the reliability of navigated TMS (nTMS) motor representation maps has been studied in the healthy population and in brain tumor patients. The lesions behind intractable epilepsy differ from typical brain tumors, ranging from developmental cortical malformations to injuries early in development, and may influence the functional organization of the cortical areas. Moreover, the interictal cortical epileptic activity and antiepileptic medication may affect the nTMS motor threshold. The reliability of the nTMS motor representation localization in epilepsy patients has not been addressed.

METHODS

We compared the nTMS motor cortical representation maps of hand and arm muscles with the results of invasive electrical cortical stimulation (ECS) in 13 patients with focal epilepsy. The nTMS maps were projected to the cortical surface segmented from preoperative magnetic resonance images (MRI), and the positions of the subdural electrodes were extracted from the postoperative low-dose computed tomography (CT) images registered with preoperative MRI.

RESULTS

The 3D distance between the average nTMS site and average ECS electrode location was 11 ± 4 mm for the hand and 16 ± 7 mm for arm muscle representation areas. In all patients the representation areas defined with nTMS and ECS were located on the same gyrus, also in patients with abundant interictal epileptic activity on the motor gyrus.

CONCLUSIONS

nTMS can reliably locate the hand motor cortical representation area with the accuracy needed for pre-surgical evaluation in patients with epilepsy.

Psychotic disorder and focal epilepsy in a left-handed patient with chromosome XYY abnormality

OBJECTIVE

To discuss the relationship between XYY chromosome abnormality, psychiatric disorders and epilepsy.

METHOD

Single case report.

RESULTS

A 34-year-old man with 47, XYY karyotype and normal intelligence was followed-up at a neuropsychiatric clinic for over 30 years. He was first seen at age 3 years with a history of delayed motor and language development and an immunodeficiency syndrome. At age 8 years he developed refractory focal epilepsy, and in late adolescence he started to exhibit increasingly prominent obsessive thoughts, paranoid ideation, and aggressive sexual fantasies and behaviour.

CONCLUSIONS

When interpreted within the context of previous literature reports, this case suggests a pathophysiological link between XYY chromosome abnormality, characteristic psychiatric symptoms and epilepsy disorder.

Motor representation areas in epileptic patients with focal motor seizures: A TMS study

PURPOSE

This study used TMS mapping to investigate the motor representation of the abductor pollicis brevis (APB) muscles in a group of patients with focal epilepsy originating in central or pre-central region.

METHODS

Eight epileptic patients and eight control subjects participated in the study. The coil was moved in 1.5-cm steps along a grid drawn on the subject's skull over the motor cortex of both hemispheres. At each site, six APB motor responses (evoked by TMS at 1.2 times the resting motor threshold) were recorded and averaged. The peak-to-peak amplitude was measured and plotted against the mediolateral and anteroposterior coil positions. The area of each APB muscle representation was measured and the position of the optimal point was calculated.

RESULTS

The resting motor threshold was increased bilaterally in epileptic patients. The maps were distorted in most patients (but not in control subjects), as evidenced by an off-centre optimal point. Interhemispheric differences in APB map areas were greater in patients than in control subjects. However, whether these increases in map area were on the epileptic side or on healthy side depended on the given subject.

CONCLUSIONS

The changes in APB representation observed in epileptic patients demonstrate that reorganization occurs within the motor cortex. The heterogeneity of the present results is probably related to different locations of the epileptogenic and/or lesional areas and to a variety of compensatory phenomena that may occur, notably with respect to the disease duration.

Antiepileptic effects of low-frequency repetitive transcranial magnetic stimulation by different stimulation durations and locations

OBJECTIVE

To evaluate the antiepileptic effect of low-frequency rTMS (repetitive transcranial magnetic stimulation) in the patients with intractable epilepsy.

METHODS

We enrolled 35 patients with localization-related epilepsy who had experienced at least one complex partial seizure or a secondarily generalized seizure per week on a constant antiepileptic drug regimen over an 8-week period. rTMS was administered using a Rapid(2) magnetic stimulator with an air-cooled coil at 0.5Hz for 5 consecutive days at 100% of rMT (resting motor threshold). Patients were divided into a focal stimulation group with a localized epileptic focus, or a non-focal stimulation group with a non-localized or multifocal epileptic focus. These two groups were then randomly subdivided into four subgroups depending on the total number of stimulations administered, i.e., 3000 pulse and 1500 pulse subgroups. Weekly seizure frequencies were determined for 8 weeks before and after rTMS. To compare the number of interictal spikes before and after rTMS, EEG was recorded twice before (1st day) and after rTMS (5th day).

RESULTS

Mean weekly seizure frequency was non-significantly decreased after rTMS (8.4-->6.8/week, -13.9%). Longer stimulation subgroups (3000 pulses, -23.0%) tended to have fewer seizures than shorter stimulation subgroups (1500 pulses, -3.0%), without statistical significance. TMS stimulation site and structural brain lesions did not influence seizure outcome. However, interictal spikes significantly decreased (-54.9%, P=0.012) after rTMS and they totally disappeared in 6 patients (17.1%, 6/35).

CONCLUSIONS

Low-frequency rTMS reduced interictal spikes, but its effect on seizure outcome was not significant. Focal stimulation for a longer duration tended to further reduce seizure frequency.

SIGNIFICANCE

These findings may help clinicians to further investigate the therapeutic potential of the rTMS for patients with intractable epilepsy.

Quantification of Unidirectional Nonlinear Associations Between Multidimensional Signals

In this paper, we present a rigorous, general definition of the nonlinear association index, known as h2. Proving equivalence between different definitions we show that the index measures the best dynamic range of any nonlinear map between signals. We present also a construction for removing the influence of one signal from another, providing, thus, the basis of an independent component analysis. Our definition applies to arbitrary multidimensional vector-valued signals and depends on an aperture function. In this way, the bin-related classic definition of h2 can be generalized. We show that upon choosing suitable aperture functions the bin-related intuitive definition can be deduced. Special attention is dedicated to the direction of the association index that in general is taken in only one sense. We show that for linearly coupled signals high associations are always bidirectional. As a consequence, high asymmetric nonlinear associations are indicators of nonlinear relations, possibly critical, between the dynamic systems underlying the measured signals. We give a simple simulated example to illustrate this property. As a potential clinical application, we show that unidirectional associations between electroencephalogram (EEG) and electromyogram (EMG) recorded from patient with pharmacologically intractable epilepsy can be used to study the cortical involvement in the generation of motor seizures.

Prolonged Focal Negative Motor Seizures: A Video-EEG Study

PURPOSE

Focal negative motor (akinetic) seizures are rare ictal events that are diagnostically challenging because they are difficult to differentiate from postictal Todd paresis, transient ischemic attacks, migraine events, and psychogenic episodes.

METHODS

We describe a 45-year-old man in whom, after surgical drainage of a right frontoparietal subdural hematoma, prolonged episodes developed with flaccid paralysis of the left arm.

RESULTS

A video-EEG recording demonstrated a close relation between the focal motor impairment and a clear-cut epileptic ictal discharge involving the right perirolandic cortical areas.

CONCLUSIONS

On the basis of the electroclinical data, we hypothesize the involvement of the primary motor area in the genesis of the epileptic discharge triggering focal negative seizures.

Functional connectivity in human cortical motor system: a cortico-cortical evoked potential study

In order to understand the complex functional organization of the motor system, it is essential to know the anatomical and functional connectivity among individual motor areas. Clinically, knowledge of these cortico-cortical connections is important to understand the rapid spread of epileptic discharges through the network underlying ictal motor manifestation. In humans, however, knowledge of neuronal in vivo connectivity has been limited. We recently reported a new method, 'cortico-cortical evoked potential (CCEP)', to electrically track the cortico-cortical connections by stimulating a part of the brain through subdural electrodes and recording the cortical evoked potentials that emanate from a distant region of the cortex via neuronal projections. We applied the CCEP methodology to investigate in vivo cortico-cortical connections between the lateral motor cortex [LMCx; sensorimotor (SM) and lateral premotor areas] and the medial motor cortex [MMCx; supplementary motor area proper (SMA), pre-SMA and foot SM]. Seven patients with intractable partial epilepsy were studied. These patients had chronic implantation of subdural electrodes covering part of the lateral and medial frontal areas. As a part of the routine pre-surgical evaluation, comprehensive cortical mapping was performed by electrical stimulation of the subdural electrodes, and the precise localization of the subdural electrodes was defined by MRI co-registration. Single-pulse electrical stimuli were delivered to MMCx (7 patients) and LMCx (4), and CCEPs time-locked to the stimuli were recorded by averaging electrocorticograms from LMCx and MMCx, respectively. Short-latency CCEPs were observed when stimulating MMCx and recording from LMCx (mean latency: 21.6 ms, range: 9-47 ms) and vice versa when stimulating LMCx and recording from MMCx (mean latency: 29.4 ms, range: 11-57 ms). In terms of the location of these stimulus sites and CCEP responses along the rostrocaudal axis, regression analysis revealed a consistent correlation between the sites of stimulation and maximum CCEP for stimulation of both MMCx and LMCx. Functionally, stimulation of the positive motor areas in MMCx elicited CCEPs at the somatotopically homologous regions in LMCx (71%). The same findings were observed in MMCx (82%) upon stimulation of LMCx. In four subjects in whom bi-directional connectivity was investigated by stimulating both MMCx and LMCx, reciprocality was observed in the majority of connections (78-94%). In conclusion, the present study demonstrated a human motor cortico-cortical network connecting (i) anatomically homologous areas of LMCx and MMCx along the rostrocaudal cognitive-motor gradient; and (ii) somatotopically homologous regions in LMCx and MMCx in a reciprocal manner.

[Supplementary sensory-motor seizures--symptomatology, etiology, and surgical management with illustrative case reports]

In the past decade, owing to the advance of epilepsy surgery, growing knowledge has accumulated on the role of the supplementary motor area, described by Penfield and coworkers in the early fifties, in movement regulation and on the characteristics of seizures involving this area. In the Hungarian neurological literature this topic--despite its neurophysiological and practical clinical importance--has been hardly touched. The authors, based on their own experience obtained from surgeries performed within the framework of the "Co-operative Epilepsy Surgery Program", describe the electrophysiological features of this area, its role in movement regulation and the symptoms of epileptic seizures stemmed from or spread onto this area. Using cases as illustrations, they demonstrate the reasoning and various algorithms of the multidisciplinary examination necessary to explore the seizure onset zone and the pathways of seizure spread. Details of the surgical solution are also described.

Prolonged Deficits After Focal Inhibitory Seizures

INTRODUCTION

Seizures are most commonly associated with positive phenomena such as tonic, clonic or myoclonic movements, automatisms, paresthesias and hallucinations. Negative phenomena, however, are not an uncommon manifestation of seizure activity. Examples of negative seizure phenomena include speech arrest, aphasia, amaurosis, amnesia, numbness, deafness, neglect and atonic seizures. Less commonly described in the literature are focal inhibitory motor seizures.

METHODS AND RESULTS

Two patients presenting with rapidly progressive, prolonged hemiparesis, sensory neglect and hemi-visual field obscuration are described. Computed tomography (CT) and magnetic resonance imaging (MRI) of the brain did not reveal progression of known structural lesions or new lesions. The superficial cortex of the hemisphere contralateral to the hemiparesis and sensory neglect enhanced diffusely with gadolinium on T1-weighted MRI images. Electroencephalography demonstrated periodic lateralized epileptiform discharges (PLEDs) in one patient and lateralized suppression and slowing in the other patient. Single photon emission computed tomography (SPECT) revealed hyperperfusion in the hemisphere contralateral to the hemiparesis and sensory neglect. The changes seen on MRI and SPECT resolved with resolution of the symptoms.

CONCLUSION

Taken together with the clinical history, the results from these investigations suggest focal inhibitory seizure as the underlying etiology. A review of the literature and investigations helpful in making this difficult diagnosis are provided.

The predictive localizing value of tonic limb posturing in supplementary sensorimotor seizures

OBJECTIVE

To determine whether early tonic limb posturing is reliable in lateralizing or localizing of the seizure generator in 14 patients with pharmacoresistent supplementary sensorimotor area (SSMA) seizures.

METHODS

All patients underwent high-quality MRI scans and stereo-EEG recordings.

RESULTS

The SSMA seizure semiology predicted focal or regional ictal onset in the SSMA in six (43%) patients: Three had a focal SSMA seizure onset, and three had a regional seizure onset with involvement of one SSMA plus adjacent neocortex. The eight remaining patients had diffuse uni- or bilateral seizure onset. Eight of 14 patients underwent a frontal or central cortical resection, but a good outcome was seen in only 3: 2 with no SSMA resection and 1 with an extensive central removal.

CONCLUSIONS

SSMA semiology is suggestive of early involvement of this region but is by no means a reliable indicator that the primary SSMA contains the seizure focus.

Alternating hemiplegia of childhood: presentation of two cases regarding the extent of variability

Alternating hemiplegia of childhood is an episodic neurological disorder, the diagnosis of which is solely clinical. In this report, two patients with alternating hemiplegia, one as a representative of the classical picture and the other with unusual features, are presented by video display. Some clinical manifestations and the variability of symptoms are discussed with regard to their place in the diagnosis of the disease. (Published with videosequences).

MRI and EEG findings in surgically treated patients with partial seizures due to neuronal migration disorders, their relations to each other and to surgery outcome

OBJECTIVES

To evaluate magnetic resonance imaging (MRI) and electro-encephalogram (EEG) findings of patients with therapy-resistant partial seizures due to neuronal migration disorders (NMD), and compare them with each other and with surgery outcome.

MATERIAL AND METHODS

The MRI, interictal and ictal EEG findings, and their relations to each other in 41 patients with NMD were compared with class IA surgery outcome.

RESULTS

The patients showed an MRI lesion in decreasing frequency from the frontal to the occipital areas. A predominantly extratemporal location of the interictal EEG foci (73.3%) and ictal patterns (82.4%) was therefore apparent, also showing a diminishing frequency from the anterior to the posterior areas. Comparing the EEG foci with the MRI lesions, the same location of the interictal foci was found in 68.4% and of the ictal foci in 52.7%, including several cases with a more widespread EEG focus or MRI lesion. The same location of interictal as well as ictal foci was evident in 85.7%. The most favourable surgery outcome (class IA) was, on average, apparent in patients with an MRI lesion (28.6% vs 25%), a main interictal EEG focus (50% vs 18%) and an ictal seizure pattern (37.5% vs 16.7%) located in the temporal area; likewise, if the interictal focus (30.8% vs 18.2%) and the ictal pattern (31.8% vs 12.5%) showed the same location as the MRI lesion, as well as when the interictal and ictal EEG changes had an equal location (30% vs 20%).

CONCLUSION

MRI and EEG recordings show relatively close relations to each other and might be important methods to predict surgery outcome in NMD patients.

Rasmussen syndrome: multifocal spread of inflammation suggested from MRI and PET findings

BACKGROUND

A 6-year-old girl with Rasmussen syndrome (RS) showed multiple small high-signal-intensity areas independently in the right hemisphere by fluid-attenuated inversion recovery (FLAIR) imaging on magnetic resonance imaging (MRI) 1 year after the onset of epilepsy.

METHODS

MRI performed 4 months later demonstrated a further increase in the number of these foci and enlargement in the size of the previous FLAIR lesions.

RESULTS

An [18F]-fluorodeoxyglucose-positron emission tomography (FDG-PET) study showed a strong, spotty uptake in the right temporooccipital regions, corresponding to the sites of continuous EEG seizure discharges. In contrast, [11C]methionine PET demonstrated multifocal uptake regions, which corresponded anatomically to the FLAIR lesions, suggesting sites of underlying chronic inflammation.

CONCLUSIONS

These neuroimaging findings suggested that the inflammatory process in RS spreads either multifocally at the same time, as seen in this case, or from one discrete area to the adjacent region, as reported previously.

Reduced inhibition within primary motor cortex in patients with poststroke focal motor seizures

BACKGROUND

Following an ischemic brain lesion, the affected cortex undergoes structural and functional changes that may lead to increased cortical excitability or decreased inhibitory neuronal activity, resulting in the occurrence of poststroke epileptic seizures in 6 to 10% of patients with stroke.

METHODS

To assess motor cortical excitability, transcranial magnetic stimulation (TMS) was used to determine the silent period (SP) duration in 84 consecutive patients with ischemic stroke.

RESULTS

In a subpopulation of six patients (38 to 72 years old) a significant decrease of the SP duration (mean 116 +/- 14 msec) was detected in either the arm or the leg on the affected side as compared to the corresponding unaffected limb (mean 231 +/- 32 msec). This electrophysiologic abnormality was clinically associated with focal motor seizures in five of the six patients, whereas none of the other 76 patients with normal or prolonged SP durations developed seizures or epilepsy.

CONCLUSIONS

Silent period shortening in this group reflects decreased inhibitory activity that may partly be related to functional or structural impairment of GABAergic interneurons. TMS may be of value for determining patients with stroke at risk for developing poststroke seizures.

Focal clonus elicited by electrical stimulation of the motor cortex in humans

Focal clonic seizures are a frequent epileptic phenomenon. However, there are little data about their pathomechanism. In four patients with focal epilepsy and subdural electrodes, focal clonus was elicited by electrical stimulation of the motor cortex. Three additional patients underwent intraoperative stimulation of the spinal cord. Rhythmic clonic muscle responses were elicited by cortical stimulation with 20-50 Hz. The clonus consisted of simultaneous trains of compound muscle action potentials (CMAP) in agonistic and antagonistic muscles alternating with periods of muscular silence despite continuous stimulation. Clonus frequency decreased from 4.0-8.0 Hz at 50 Hz stimulation to 3.0-3.5 Hz at 20 Hz paralleled by a prolongation of the trains of CMAP. The stimulation frequency correlated with the number of stimuli blocked during relaxation. During the stable stimulation periods, the clonus frequency decreased over time. The number of stimuli which formed a train of CMAP and which were blocked during relaxation increased towards the end of the stimulation periods. Increasing intensity of stimulation at the same frequency converted a clonic to a tonic response. There was always an 1:1 relationship between stimulus and CMAP during spinal cord stimulation. We hypothesize that during cortical stimulation, clonus is elicited by synchronous activation of pyramidal tract (PT) neurons which results in excitation of intracortical GABA(B)ergic interneurons by recurrent axon-collaterals. This leads to stepwise hyperpolarization of PT neurons intermittently suppressing the output of PT neurons despite continuous stimulation. This mechanism can explain our finding that temporal and spatial summation of the stimuli were needed for clonus generation.

Electroencephalographic dipoles of spikes with and without myoclonic jerks caused by epilepsia partialis continua

We used electroencephalographic (EEG) dipole analysis to investigate the generators of spikes with and without myoclonic jerks in a 12-year-old patient with epilepsia partialis continua secondary to left parietal cortical dysplasia. We recorded EEG and right wrist extensor electromyography (EMG) and collected 42 spikes with jerks (jerking spikes) and 42 spikes without jerks (nonjerking spikes). We applied a single moving dipole model to the individual and averaged spikes. Dipoles at the negative peak of individual jerking and nonjerking spikes were localized in the dysplastic area. At the onset of the averaged jerking spike that preceded the EMG discharges by 20 ms, the dipole was in the motor cortex, whereas for the averaged nonjerking spike, the dipole was in the sensory cortex. The dipole moment at averaged jerking spike onset was twice that of the averaged nonjerking spike. Electroencephalographic dipole analysis of averaged spikes differentiated the generator of jerking and nonjerking spikes in epilepsia partialis continua. Individual dipoles demonstrated the area of epileptogenic cortical dysplasia.

Periodic lateralized epileptiform discharges in influenza B-associated encephalopathy

An 18-year-old woman presented with coma, hemicomvulsions, and transient periodic lateralized epileptiform discharges (PLEDs). Serological tests were positive for influenza B, and cerebrospinal fluid PCR for herpes simplex virus DNA was negative. Magnetic resonance imaging later showed abnormal signal intensity in the temporal lobe ipsilateral to the PLEDs. Influenza-associated encephalopathy may cause hemiconvulsions and PLEDs, and can mimic herpes simplex encephalitis.

Ictal brain hemodynamics in the epileptic focus caused by a brain tumor using functional magnetic resonance imaging (fMRI)

Using functional magnetic resonance imaging (fMRI) we were able to observe, in detail, ictal brain hemodynamics during epileptic seizure caused by a brain tumor. A 53-year-old man was experencing partial motor seizures of the left side of his face and neck. In a brain MR image a mass lesion was found in the subcortical area of the right frontal lobe. We found focal spikes in his right hemisphere, though dominantly in C4 and T4 regions. fMRI investigations were carried out at 1.5 T (GE Signa Horizon) using gradient-echo echo-planar neuroimaging. We were able to perform the ictal examination twice. The activated regions were focalized and clearly found only on the lateral side of the tumor base. The region was in agreement with the epileptic focus examined using an electrocorticogram (ECOG). The signal intensity in the seizure focus rapidly increased 30 seconds before the convulsion was observed. After the end of the convulsion it also took 30 seconds to restore the signal intensity to the baseline value. fMRI is a very useful tool for various studies such as the identification of the epileptic focus, the mechanism of epileptic seizure, and so on.

Changes in cerebral hemodynamics during simple partial motor seizures

Changes in cerebral perfusion were studied during nine short-lasting simple partial motor seizures (SPS) in an 11-year-old girl. Blood flow velocity changes in both middle cerebral arteries (MCAs) were assessed by transcranial Doppler sonography during simultaneous EEG monitoring. Within 7.4 +/- 1.4 s after electroencephalographic seizure onset, flow velocity in the MCA ipsilateral to the electrical discharges started to increase and then gradually rose up to 70% above baseline values. Spread of the epileptic activity to the other hemisphere in the late stage of seizure was associated with a slight increase in blood flow velocity (<30%) in the contralateral MCA. After the end of the seizure, flow velocities returned to baseline within 47 +/- 7 s. Our findings indicate that focal epileptic seizures evoke asymmetric perfusion increases which are closely related to the onset and cessation of the electroencephalographic seizure activity.

Repetitive sleep starts in neurologically impaired children: an unusual non-epileptic manifestation in otherwise epileptic subjects

Sleep starts, also called hypnagogic or hypnic jerks, are bilateral, sometimes asymmetric, usually single, brief body jerks that coincide with sleep onset. We describe sleep starts occurring repetitively in three epileptic children with spastic-dystonic diplegia and mental retardation. Repetitive sleep starts began at age 18 months in two children and at 9 months in the third. All three children had had feto-neonatal asphyxia; two presented with spastic and one with dystonic tetraparesis. One had West syndrome and two had partial motor seizures in the first year of life. Seizures were controlled in all three patients by antiepileptic drug therapy. Video/EEG recordings of all the children during the afternoon nap revealed clusters of sleep starts during the transition between wakefulness and sleep. Cluster lasted 4-15 min and comprised from twenty to twenty-nine contractions. The EEG counterpart of the event sometimes showed an arousal response, at times inducing complete awakening. Repetitive sleep starts should be recognized and clearly differentiated from epileptic seizures, especially if they appear in epileptic subjects. In neurologically compromised patients, they could represent an intensification of an otherwise normal event, due to the lack of strong inhibitory influence of the pyramidal tract resulting from the pyramidal lesion.

Epilepsy and perisylvian lipoma/cortical dysplasia complex

Intracranial lipomas are congenital malformations composed of mature adipocytes. They are usually located in the midline, particularly in the pericallosal region, a hemispheric location accounting for only 3 to 7% of cases. Review of the literature found 21 previous cases of hemispheric lipoma. Although hemispheric cerebral lipomas are rare, association with epilepsy appears to be frequent. We have recently studied two patients in whom epilepsy was the first clinical manifestation of hemispheric cerebral lipoma in the sylvian region. The patients presented with simple motor partial seizures as the first manifestation of the lesion. Neurological examination was normal. MRI disclosed in both cases a lesion involving the sylvian fissure with characteristics of the lipid signal. MRI also demonstrated abnormalities involving the cerebral cortex in the vicinity of the lesion (pachygyria-like aspect). Partial excision of the lesion was achieved in one patient but was followed by a worsening of seizures and neurological condition (hemiparesis). According to the literature, the prognosis for epilepsy in patients with hemispheric lipoma appears good. Several other arguments support non-surgical management: the lesion is benign and can be identified with a high degree of certainty by imaging; surgery is technically difficult due to adherence to adjacent vascular and cerebral structures and hypervascularity; location near functional brain tissue increases the risk of postoperative sequelae. In addition, mechanisms of epilepsy probably involve vascular and cortical dysplasic abnormalities. In consideration of the complexity of the lesion, hemispheric lipomas are more appropriately classified with localized cortical malformations rather than as simple extracerebral malformations.

[Palinopsia associated with partial seizures secondary to right parietal hemorrhage]

Palinopsia and motor partial seizures were associated in a 51-year-old man. The manifestation appeared six months after a right parietal hemorrhage. The relationship between the hallucinatory phenomena and epilepsy is discussed.

Asymmetry of cortical excitability revealed by transcranial stimulation in a patient with focal motor epilepsy and cortical myoclonus

Motor cortex excitability was analyzed with transcranial stimulation in a patient with motor focal epilepsy and cortical myoclonus originating from the right motor cortex. The motor threshold to single transcranial magnetic shocks, but not to electric stimuli, was higher in the epileptic motor cortex than the normal left motor cortex. Single magnetic shocks elicited a short cortical silent period (50 ms) in the epileptic motor cortex. Paired magnetic stimuli also showed reduced cortico-cortical inhibition. These findings reveal an asymmetry in cortical excitability presumably due to impaired inhibition in the epileptic motor cortex.