Neuroimaging findings in children with benign focal epileptiform discharges

PURPOSE

To determine reasons for neuroimaging and neuroimaging findings in children with benign focal epileptiform discharges (BFEDs).

METHODS

We performed a retrospective chart review of children who had BFEDs on routine EEG and underwent brain MRI.

RESULTS

We identified 97 patients with BFEDs and MRI. Forty-five of these 97 patients also had seizures consistent with benign focal epilepsy of childhood with centrotemporal spikes (BECTS). Rationale for imaging in the 45 BECTS patients included historical features such as headaches (14), increase in seizure frequency (5), and new events (5). Nine MRIs were obtained prior to referral and 12 for unspecified reasons. MRI findings were not significantly different between BECTS and BFEDs patients. Fourty-one patients (42%) had abnormal findings on MRI, including T2 hyperintensities (10), hippocampal atrophy (6), malformation of cortical development (4), volume loss (5), Chiari malformation (4), and others (18).

CONCLUSION

MRIs are not routinely recommended in patients with BECTS unless atypical features are present. Atypical features which may prompt MRI include change in clinical seizure types or frequency, historical features such as headaches, abnormal neurological exam, and atypical EEG features. 42% of our selected patients had intracranial abnormalities, most of which were of unclear clinical significance. Remote infarcts and early lesions accounted for most MRI findings suggesting they may be related to BFEDs.

Childhood absence epilepsy in patients with benign focal epileptiform discharges

Few reports are available of ictal recordings in patients with benign focal epileptiform discharges. The study objective was to estimate the frequency of such recordings and to describe their clinical and electrophysiologic presentation. We performed a retrospective chart review of all patients undergoing routine electroencephalography (EEG) with video during a 10-year period. Among 214 patients with benign focal epileptiform discharges, 5 patients were identified with recorded EEG seizures (2.3%). Epilepsy syndromes included one case of benign focal epilepsy of childhood, three cases of childhood absence epilepsy, and in one case the patient presented with both. Only 1 of the 214 patients (0.4%) had a seizure characteristic of benign focal epilepsy of childhood. A literature review revealed the coexistence of childhood absence and benign focal epilepsy of childhood or benign focal epileptiform discharges within the same patient. These findings suggest that benign focal epilepsy of childhood seizures are rarely recorded during routine EEG, probably because seizures occur during the early morning part of the sleep cycle, which may differ from the brief nap during routine EEG. There was concurrence of generalized spike and wave discharges in these patients. It is unclear whether this is related to a common pathophysiologic factor.

Anoxia-ischemia: a mechanism of seizure termination in ictal asystole

Cerebral anoxia-ischemia (CAI) is a potent inhibitor of cerebral hyperactivity and a potential mechanism of seizure self-termination. Prolonged ictal asystole (IA) invariably leads to CAI and has been implicated as a potential cause of sudden unexplained death in epilepsy (SUDEP). IA was seen in eight consecutive patients (0.12% of all patients monitored). Ten of their seizures with IA had evidence of CAI on electroencephalography (EEG), manifested by bilateral hypersynchronous slowing (BHS), and were compared to 18 seizures without signs of CAI. The ictal EEG pattern resolved in all 10 CAI events with onset of the BHS. The period from IA onset to seizure end was reduced in events with BHS compared to events without BHS (10.5 s vs. 28.3 s, respectively; p = 0.005), and the total seizure duration tended to be shorter. Anoxia-ischemia as a result of IA may represent an effective endogenous mechanism for seizure termination and may explain why the hearts of patients with ictal asystole reported to date in the literature resumed beating spontaneously.

GENERALIZED SIDELOBE CANCELLER FOR MAGNETOENCEPHALOGRAPHY ARRAYS

In the last decade, large arrays of sensors for magnetoencephalography (MEG) (and electroencephalography (EEG)) have become more commonplace, allowing new opportunities for the application of beamforming techniques to the joint problems of signal estimation and noise reduction. We introduce a new approach to noise cancellation, the generalized sidelobe canceller (GSC), itself an alternative to the linearly constrained minimum variance (LCMV) algorithm. The GSC framework naturally fits within the other noise reduction techniques that employ real or virtual reference arrays. Using expository human subject data with strong environmental and biological artifacts, we demonstrate a straightforward sequence of steps for practical noise filtering, applicable to any large array sensor design.

Lateralization of Interictal EEG Findings

Several reports indicate that interictal epileptiform discharges (IED) may be more likely to occur over the left cerebral hemisphere than over the right. The objective of our study was to determine the frequency and type of IED on routine and multihour EEGs in a tertiary epilepsy center to estimate the frequency of left-sided versus right-sided IED and to determine interictal spike distribution pattern differences between adult and pediatric epilepsy patients. The current study retrospectively reviewed 31,207 EEGs (25,793 routine EEGs and 5414 multihour EEGs) recorded on 24,003 patients during the period from 1993 to 2003. All EEGs were read according to a systematic EEG classification system. Every patient was considered only once by including the first abnormal EEG. Regional unilateral or bilateral IEDs were recorded in 1707 patients (7%). Regional unilateral or bilateral slow was recorded in 2297 patients (9.6%). Left-sided regional IED were seen in 828 patients and accounted for 58% of all unilateral IED. Left-sided slow was seen in 1389 patients and accounted for 65% of all unilateral slow. Lateralization of slow was due to intermittent slow, whereas continuous slow involved both hemispheres equally. There was no lateralization difference in benign focal epileptiform discharges of childhood. Lateralization shows a tendency toward greater left-sided lateralization of interictal findings with aging. Benign focal epileptiform discharges were only seen under the age of 20 years old. Regional IEDs were seen in approximately 7% of patients and slowing occurs in 10% of patients. Both abnormalities were seen more frequently in the left hemisphere. Age adjusted analysis of the data revealed that this left-sided predominance was mildly increased in adults as compared with pediatric patients.

Ictal asystole: a benign condition?

Ictal asystole (IA) has been implicated as a preventable cause of sudden unexplained death in epilepsy presumably provoked by a direct autonomic effect of the electrical stimulus on the heart. An electronic database search of patients with IA was performed comparing heart rate (HR) characteristics to a group of patients with vasovagal asystole. IA was seen in eight patients, all with temporal lobe epilepsy. No statistical difference was found in duration of asystole, bradycardia, and baseline HR characteristics except of a higher HR acceleration postasystole in the controls. None of the six patients with IA who underwent pacemaker implantation had recurrence of asystolic events during mean follow-up of 5 years. This study in a small group of patients suggests that the epileptic activation leading to IA is possibly mediated through a transient increase in vagal tone and not by a direct autonomic effect on the heart.

Video-electrographic and clinical features in patients with ictal asystole

OBJECTIVE

Ictal asystole (IA) is a rare event mostly seen in patients with temporal lobe epilepsy (TLE) and a potential contributor to sudden unexplained death in epilepsy (SUDEP). Clinical and video-electroencephalographic findings associated with IA have not been described, and may be helpful in screening for high risk patients.

METHODS

A database search was performed of 6,825 patients undergoing long-term video-EEG monitoring for episodes of IA.

RESULTS

IA was recorded in 0.27% of all patients with epilepsy, eight with temporal (TLE), two with extratemporal (XTLE), and none with generalized epilepsy. In 8 out of 16 recorded events, all occurring in patients with TLE, seizures were associated with a sudden atonia on average 42 seconds into the typical semiology of a complex partial seizure. The loss of tone followed after a period of asystole usually lasting longer than 8 seconds and was associated with typical EEG changes seen otherwise with cerebral hypoperfusion. Clinical predisposing factors for IA including cardiovascular risk factors or baseline ECG abnormalities were not identified.

CONCLUSION

Ictal asystole is a rare feature of patients with focal epilepsy. Delayed loss of tone is distinctly uncommon in patients with temporal lobe seizures, but may inevitably occur in patients with ictal asystole after a critical duration of cardiac arrest and cerebral hypoperfusion. Further cardiac monitoring in patients with temporal lobe epilepsy and a history of unexpected collapse and falls late in the course of a typical seizure may be warranted and can potentially help to prevent sudden unexplained death in epilepsy.

Neuroimaging and Neurophysiology of Periodic Lateralized Epileptiform Discharges: Observations and Hypotheses

PURPOSE

We assessed neuroimaging lesion type and distribution in patients with periodic lateralized epileptiform discharges (PLEDs), with a view to identifying electrographic differences between PLEDs associated with differing lesion locations. Our observations led us to consider a conceptual synthesis between PLEDs and periodic complexes (PCs).

METHODS

Retrospective review of acute neuroimaging results (CT/MRI) on patients identified to have EEG PLEDs, for the period 1999-2003 (n=106). Blinded classification of original EEG recordings.

RESULTS

Neuroimaging abnormalities were classified as acute or chronic cortical, or acute or chronic subcortical. Seven out of 106 scans were classified nonlesional. Overall approximately 70% of scans had cortical abnormalities, whether acute or chronic; approximately 23% had subcortical abnormalities. "Cortical" PLEDs were significantly longer in duration (p<0.05) and more variable in morphology (p<0.01) than "subcortical" PLEDs.

CONCLUSIONS

Structural brain disease commonly, but not invariably, underlies PLEDs; lesion type is spatiotemporally variable. Cortical and subcortical PLEDs have distinct EEG signatures. There is evidence that these may relate to mechanisms for other pathological large-scale oscillatory brain synchronies (e.g., PCs).

Lateralizing significance of quantitative analysis of head movements before secondary generalization of seizures of patients with temporal lobe epilepsy

PURPOSE

To quantitatively evaluate the lateralizing significance of ictal head movements of patients with temporal lobe epilepsy (TLE).

METHODS

We investigated EEG-video recorded seizures of patients with TLE, in which the camera position was perpendicular to the head facing the camera in an upright position and bilateral head movement was recorded. Thirty-eight seizures (31 patients) with head movement in both directions were investigated. Ipsilateral and contralateral head movements were defined according to ictal EEG. Head movements were quantified by selecting the movement of the nose in relation to a defined point on the thorax (25/s) in a defined plane facing the camera. The duration of the head version was determined independently of the camera angle. The angle, duration, and angular speed of the head movements were computed and inter and intrasubject analyses were performed (Wilcoxon rank sum).

RESULTS

Ipsilateral movement always preceded contralateral movement. The positive predictive value was 100% for movement in both directions. The duration of contralateral head version was significantly longer than ipsilateral head movement (6.4 +/- 4.1 s vs. 3.9 +/- 3.1 s, p<0.001). The angular speed of both movements was similar (15.5 +/- 12.1 deg/s vs. 17.3 +/- 13.0 deg/s).

CONCLUSION

The quantitative analysis shows the importance of sequence in the seizure's evolution and duration, but not angular speed for correct lateralization of versive head movement. This quantitative method shows the high lateralizing value of ictal lateral head movements in TLE.

An artificial neural network approach to predicting arm movements from ECoG

There are three specific aims. First, demonstrate the practicality of using an artificial neural network based approach to correlate these cortical signals with actual and imagined arm movements. Second, to identify areas of the cortical surface that provide the most useful command information. Third, quantify the information content and information transfer rate of the signals obtained from the subdural grids relative to a set of relevant arm movements. This work presents progress toward these aims.

Coexistence of focal and idiopathic generalized epilepsy in the same patient population

PURPOSE

To review the clinical, electrographic, radiological, and pathological findings of patients with coexistent idiopathic generalized and partial epilepsy syndromes.

METHODS

We performed a medical record review and a phone interview with all patients hospitalized to the Cleveland Clinic epilepsy monitoring unit (EMU) between 1992 and 2002 who fulfilled clinical and EEG criteria of coexistent partial and generalized epilepsy syndromes.

RESULTS

Seven patients were identified. Two (29%) were men with a mean age of 26 years. Four had a history of febrile seizures. Family history was positive in five. Mean duration of the generalized epilepsy syndrome was 11 years, and of the focal epilepsy 18 years. An equal number of patients developed focal versus generalized epilepsy first. Interictal EEG activity was predominantly generalized. Four had video-EEG documentation of both types of seizures. In the rest, only focal seizures were recorded but interictal activity strongly suggested a coexistent generalized epilepsy. MRI showed hippocampal atrophy in all, and hippocampal dysplasia in three. Five patients had PET imaging, all with hypometabolism in areas corresponding to the ictal onset on EEG. Four patients underwent epilepsy surgery with good surgical outcome and pathological confirmation of hippocampal sclerosis in all.

CONCLUSION

We found a 0.2% incidence of coexistent focal and primary generalized epilepsy. Febrile seizures and a positive family history were common. Good seizure control was achieved after temporal lobectomy, even when interictal generalized activity predominated.

Detection of epileptiform activity by human interpreters: blinded comparison between electroencephalography and magnetoencephalography

PURPOSE

Objectively to evaluate whether independent spike detection by human interpreters is clinically valid in magnetoencephalography (MEG) and to characterize detection differences between MEG and scalp electroencephalography (EEG).

METHODS

We simultaneously recorded scalp EEG and MEG data from 43 patients with intractable focal epilepsy. Raw EEG and MEG waveforms were reviewed independently by two experienced epileptologists, one for EEG and one for MEG, blinded to the other modality and to the clinical information. The number and localization of spikes detected by EEG and/or MEG were compared in relation to clinical diagnosis based on postoperative seizure freedom.

RESULTS

Interictal spikes were captured in both EEG and MEG in 31, in MEG alone in eight, in EEG alone in one, and in neither modality in three patients. The number of detections ranged widely with no statistical difference between modalities. A median of 25.7% of total spikes was detectable by both modalities. Spike localization was similarly consistent with the epilepsy diagnosis in 85.2% (EEG) and 78.1% (MEG) of the patients. Inaccurate localization occurred only in those cases with very few spikes detected, especially when the detections were in one modality alone.

CONCLUSIONS

Interictal epileptiform discharges are easily perceived in MEG. Independent spike identification in MEG can provide clinical results comparable, but not superior, to EEG. Many spikes were seen in only one modality or the other; therefore the use of both EEG and MEG may provide additional information.

Effects of eyelid closure, blinks, and eye movements on the electroencephalogram

OBJECTIVE

To characterize the effects of the eyeball and eyelid positions during eyeblinks on electroencephalographic (EEG) potentials.

METHODS

Movements of the upper eyelids and eyes were measured in two healthy subjects using the magnetic search coil technique during horizontal and vertical eye rotations, eyeblinks, and lid closure. Corresponding signal changes were recorded simultaneously on the electroencephalogram (EEG).

RESULTS

Spontaneous blinks produced small eye movements directed down and inward, whereas slow or forced blinks were associated with delayed upward eye rotations (i.e. Bell's phenomenon); both types of blinks caused positive EEG potentials with bifrontal distribution maximum at Fp1 and Fp2.

CONCLUSIONS

In prior reports, these positive EEG artifacts have been attributed to upward eyeball rotation during blinks-Bell's phenomenon. By contrast, our findings indicate that movements of the eyelid contribute to a greater extent to these EEG potentials than do upward eyeball rotations.

SIGNIFICANCE

Care is required in attributing EEG artifacts to movements of either eyeball or eyelid, since our findings suggest that they both contribute to these potentials.

Diagnosis of sleep-related breathing disorders by visual analysis of transthoracic impedance signals in pacemakers

BACKGROUND

Minute ventilation sensors of cardiac pacemakers measure ventilation by means of transthoracic impedance changes between the pacemaker case and the electrode tip. We investigated whether this technique might detect sleep-related breathing disorders.

METHODS AND RESULTS

In 22 patients, analog waveforms of the transthoracic impedance signal measured by the pacemaker minute ventilation sensor over the course of a night were visualized, scored for apnea/hypopnea events, and compared with simultaneous polysomnography. Analysis of transthoracic impedance signals correctly identified the presence or absence of moderate to severe sleep apnea (apnea/hypopnea index, AHI >20 h(-1)) in all patients (receiver operating characteristics, ROC=1.0). The ROC for AHI scores of > or =5 h(-1) and > or =10 h(-1) showed an area under the curve of 0.95, P<0.005, and 0.97, P<0.0001, respectively. Accuracy over time assessed by comparing events per 5-minute epochs was high (Cronbach alpha reliability coefficient, 0.85; intraclass correlation, 0.73). Event-by-event comparison within +/-15 seconds revealed agreement in 81% (kappa, 0.77; P<0.001).

CONCLUSIONS

Detection of apnea/hypopnea events by pacemaker minute ventilation sensors is feasible and accurate compared with laboratory polysomnography. This technique might be useful to screen and monitor sleep-related breathing disorders in pacemaker patients.

Neurointensive care unit system for continuous electrophysiological monitoring with remote web-based review

There is a need in the neurological intensive care unit for a single integrated bedside monitor for continuously monitoring the function of the patient's central nervous system. In this paper, we demonstrate the feasibility of building such a system and operating it in the intensive care environment. We have developed a fully automated system that samples electrophysiological waveforms of various modalities according to a schedule of predefined intervals along with routinely monitored cardiac and respiratory parameters. The system provides stimulation and acquires responses without requiring supervision. The electrophysiological data include brainstem auditory and somatosensory evoked potentials and epochs of the electroencephalogram. The system applies peak detection and spectral analysis to extract salient parameters from the raw waveforms. The results are made available immediately in real time on the local network for local review and further analysis. A web-based interface makes review by a qualified neurologist possible anywhere within the hospital's secure intranet during and after monitoring. This system could potentially give an early warning of impending herniation, subclinical seizures, and brain or spinal cord ischemia. We demonstrate its application in a few diverse neurological intensive care cases and a case in the interventional neuroradiology suite.

Complications of invasive video-EEG monitoring with subdural grid electrodes

OBJECTIVE

To evaluate the risk factors, type, and frequency of complications during video-EEG monitoring with subdural grid electrodes.

METHODS

The authors retrospectively reviewed the records of all patients who underwent invasive monitoring with subdural grid electrodes (n = 198 monitoring sessions on 187 patients; median age: 24 years; range: 1 to 50 years) at the Cleveland Clinic Foundation from 1980 to 1997.

RESULTS

From 1980 to 1997, the complication rate decreased (p = 0.003). In the last 5 years, 19/99 patients (19%) had complications, including two patients (2%) with permanent sequelae. In the last 3 years, the complication rate was 13.5% (n = 5/37) without permanent deficits. Overall, complications occurred during 52 monitoring sessions (26.3%): infection (n = 24; 12.1%), transient neurologic deficit (n = 22; 11.1%), epidural hematoma (n = 5; 2.5%), increased intracranial pressure (n = 5; 2.5%), and infarction (n = 3; 1.5%). One patient (0.5%) died during grid insertion. Complication occurrence was associated with greater number of grids/electrodes (p = 0.021/p = 0.052; especially >60 electrodes), longer duration of monitoring (p = 0.004; especially >10 days), older age of the patient (p = 0.005), left-sided grid insertion (p = 0.01), and burr holes in addition to the craniotomy (p = 0.022). No association with complications was found for number of seizures, IQ, anticonvulsants, or grid localization.

CONCLUSIONS

Invasive monitoring with grid electrodes was associated with significant complications. Most of them were transient. Increased complication rates were related to left-sided grid insertion and longer monitoring with a greater number of electrodes (especially more than 60 electrodes). Improvements in grid technology, surgical technique, and postoperative care resulted in significant reductions in the complication rate.

Design and evolution of a system for long-term electroencephalographic and video monitoring of epilepsy patients

The impact of technology, especially computer technology, on clinical neurophysiology instrumentation has yielded more than automation of paper-based electroencephalography. The new features now available as standard components of digital EEG/video have actually transformed practice (e.g., post hoc remontaging or filtering). At the same time, however, the fact that the signals are digital has led to a panoply of "tools in search of a problem." To incorporate appropriate tools in a practical and cost-effective fashion is a challenge that requires detailed, interdisciplinary knowledge, as well as concentrated effort. Although it is in the nature of research and development to follow a few blind alleys, too many projects are never productively implemented because excessive attention is focused on the obscure and not enough on whether and how the technique can actually help patients. In addition, a long-term view requires making the correct technology choices, to benefit from the consumer cost cycle and to ensure a continuous migration pathway. The lessons learned and principles established while bringing together the space, the people, and the equipment into an efficient, high-volume epilepsy monitoring unit are instructive.

An arrhythmia detector and heart rate estimator for overnight polysomnography studies

We present an algorithm for automatic on-line analysis of the electrocardiography (ECG) channel acquired during overnight polysomnography (PSG) studies. The system is independent of ECG morphology, requires no manual initialization, and operates automatically throughout the night. It highlights likely occurrences of arrhythmias and intervals of bad signal quality while outputting a continual estimate of heart rate. Algorithm performance is validated against standard ECG databases and PSG data. Results demonstrate a minimal false negative rate and a low false positive rate for arrhythmia detection, and robustness over a wide range of noise contamination.

Use of Ilizarov external fixator to treat joint pterygia

Joint pterygia are rare conditions characterized by joint-flexion contractures and webbing of the overlying skin and subcutaneous structures. Treatment is difficult because the neurovascular bundle is often displaced into the web, and only moderate success has been reported with past treatment options. A retrospective review was performed on five patients with six involved joints: two antecubital pterygia and four popliteal pterygia. The Ilizarov technique was used for gradual correction of pterygia through the joint (arthrodiastasis). Primary treatment goals included improvement in functional extension, hygiene independence, and cosmesis. Ambulation was also an objective in the patients with popliteal pterygia. For inclusion in this study, a minimum of 2 years' follow-up was required after the device was removed. Preoperative goals were met in four of the six joints. Initial improvement in total arc of motion was noted; however, some regression was common. Complications were frequent, and there was a learning curve for proficiency with the Ilizarov technique. We believe that the Ilizarov technique provides a treatment option for antecubital and popliteal pterygia.

Brachydactyly type C

Brachydactyly type C is an autosomal dominant disorder with markedly variable penetrance. A patient with limited gene expression has shortening limited to the middle phalanges and the first metacarpal and an elongation of the radial side of the base of the second proximal phalanx. When completely expressed the characteristic radiographic findings are shortening of all the metacarpals, greatest in the thumb, followed by the little, ring, middle, and index fingers; brachymesophalangy (shortening of the middle phalanges); shortening of the proximal phalanges of the index and middle fingers, with the proximal phalanges of the ring and small fingers of normal length; elongation of the radial side of the base of the second proximal phalanx resulting in a trapezoidal shaped epiphysis; ulnar deviation at the second and third metacarpophalangeal joints; and hypersegmentation (extra phalanx) of the index and middle fingers. The ulnar deviation of the index and middle fingers may result in scissoring and require surgical correction. The hand deformities of 10 patients with brachydactyly type C are presented to characterize the hand abnormalities in the syndrome and its variable presentation.

The polysomnogram assay: a method to represent the overnight polysomnogram in a condensed format

We present the polysomnogram assay (PSGA), a new representation format for the polysomnogram (PSG), designed to assist in the interpretation of overnight PSG studies. The technique condenses the PSG record by a factor of 30 while preserving the ability to portray PSG features of diagnostic relevance, including sleep architecture, arousals, movement, leg jerks, cyclic alternating pattern, and increased breathing effort. The PSGA patterns associated with these events are described and illustrated by examples. The new format considerably reduces the effort required to evaluate sleep quality and continuity, making it more practicable for the polysomnographer to interpret the entire overnight PSG study. The compressed time scale also facilitates analysis of relatively long PSG episodes and allows assessment of signal activity surrounding critical PSG events. The PSGA appears capable of improving identification of arousals, leg jerks, and upper airway resistance, and may be especially amenable for automatic analysis of PSG data.

How competent do our graduates feel?

As part of a review of the undergraduate curriculum to assess its relevance for a future general practitioner, a survey of self-perceived competency at graduation based on the competency list developed by the Association of Canadian Faculties of Dentistry was circulated to recent graduates and the graduating class. The overall response was 67.5 percent, and revealed that approximately 70 percent of the respondents felt well prepared in approximately 69 percent of the competencies. These were the common "bread and butter" items of dentistry, such as basic restorative dentistry, examination, diagnosis, treatment planning, local anaesthesia, and scaling. Those areas reported as less well-prepared for included financial and personnel management, performance of soft-tissue biopsies, and management of chronic orofacial pain. Clarification of the raw survey results in focus groups was needed to uncover specific details that could lead to remedial action in problem areas.