Piotr W. Olejniczak

Long-term treatment with responsive brain stimulation in adults with refractory partial seizures.

Objective: The long-term efficacy and safety of responsive direct neurostimulation was assessed in adults with medically refractory partial onset seizures. Methods: All participants were treated with a cranially implanted responsive neurostimulator that delivers stimulation to 1 or 2 seizure foci via chronically implanted electrodes when specific electrocorticographic patterns are detected (RNS System). Participants had completed a 2-year primarily open-label safety study (n = 65) or a 2-year randomized blinded controlled safety and efficacy study (n = 191); 230 participants transitioned into an ongoing 7-year study to assess safety and efficacy. Results: The average participant was 34 (±11.4) years old with epilepsy for 19.6 (±11.4) years. The median preimplant frequency of disabling partial or generalized tonic-clonic seizures was 10.2 seizures a month. The median percent seizure reduction in the randomized blinded controlled trial was 44% at 1 year and 53% at 2 years (p < 0.0001, generalized estimating equation) and ranged from 48% to 66% over postimplant years 3 through 6 in the long-term study. Improvements in quality of life were maintained (p < 0.05). The most common serious device-related adverse events over the mean 5.4 years of follow-up were implant site infection (9.0%) involving soft tissue and neurostimulator explantation (4.7%). Conclusions: The RNS System is the first direct brain responsive neurostimulator. Acute and sustained efficacy and safety were demonstrated in adults with medically refractory partial onset seizures arising from 1 or 2 foci over a mean follow-up of 5.4 years. This experience supports the RNS System as a treatment option for refractory partial seizures. Classification of evidence: This study provides Class IV evidence that for adults with medically refractory partial onset seizures, responsive direct cortical stimulation reduces seizures and improves quality of life over a mean follow-up of 5.4 years.

Neurophysiologic Basis of EEG

Summary: This review article introduces the reader to the very basics of electroencephalography (EEG). It tries to explain in simple terms the physiologic principles of EEG generation and organization at the cellular, cortical and subcortical levels. It also introduces the basic EEG terminology (see the key words).

Vagus nerve stimulation for epilepsy: Randomized comparison of three stimulation paradigms

Vagus nerve stimulation (VNS) is an effective adjunctive treatment for intractable epilepsy. However, the optimal range of device duty-cycles [on/(on + off times)] is poorly understood. The authors performed a multicenter, randomized trial of three unique modes of VNS, which varied primarily by duty-cycle. The results indicate that the three duty-cycles were equally effective. The data support the use of standard duty-cycles as initial therapy.

Vagus nerve stimulation for epilepsy: is output current correlated with acute response?

Objectives –  Vagus nerve stimulation (VNS) is an effective treatment for intractable epilepsy. It is unknown whether acute response is correlated with the amplitude of output current. The purpose of this study was to determine if the output current of VNS is correlated with percent reductions in seizure frequency and response.

Epilepsia partialis continua in Creutzfeldt–Jakob disease

Objectives– We describe a patient with Creutzfeldt–Jakob disease (CJD) with epilepsia partialis continua (EPC) and complex partial seizures. Material, methods and results– The patient presented with semi‐rhythmic jerking movements of the right upper extremity. Serial EEG findings showed progressive changes with initial periodic lateralizing epileptiform discharges (PLEDs) on the left hemisphere which evolved into more generalized periodic sharp wave complexes (PSWCs) at later stage. Video‐EEG monitoring recorded complex partial seizures originating from the left hemisphere in addition to EPC. Conclusions– A diagnosis of CJD should be considered when a rapidly progressive dementia is accompanied by abnormal movements. EPC, although rare, may present as an initial manifestation of CJD.

Lateralization of temporal lobe epilepsy and learning disabilities, as defined by disability-related civil rights law.

Summary:  Purpose: Epilepsy research has identified higher rates of learning disorders in patients with temporal lobe epilepsy (TLE). However, most studies have not adequately assessed complex functional adult learning skills, such as reading comprehension and written language. We designed this study to evaluate our predictions that higher rates of reading comprehension, written language, and calculation disabilities would be associated with left TLE versus right TLE.

Sporadic Creutzfeldt-Jakob disease with focal findings: caveats to current diagnostic criteria

The clinical diagnosis of Creutzfeldt-Jakob disease (CJD) is largely based on the 1998 World Health Organization diagnostic criteria. Unfortunately, rigid compliance with these criteria may result in failure to recognize sporadic CJD (sCJD), especially early in its course when focal findings predominate and traditional red flags are not yet present. A 61-year-old man presented with a 3-week history of epilepsia partialis continua (jerking of the left upper extremity) and a 2-week history of forgetfulness and left hemiparesis; left hemisensory neglect was also detected on admission. Repeated brain magnetic resonance imaging (MRI) showed areas of restricted diffusion in the cerebral cortex, initially on the right but later spreading to the left. Electroence-phalography (EEG) on hospital days 7, 10, and 14 showed right-sided periodic lateralized epileptiform discharges. On day 20, the EEG showed periodic sharp wave complexes leading to a diagnosis of probable sCJD and subsequently to definite sCJD with brain biopsy. Neurological decline was relatively fast with generalized myoclonus and akinetic mutism developing within 7 weeks from the onset of illness. CJD was not immediately recognized because of the patients focal/lateralized manifestations. Focal/lateralized clinical, EEG, and MRI findings are not uncommon in sCJD and EEG/MRI results may not be diagnostic in the early stages of sCJD. Familiarity with these caveats and with the most current criteria for diagnosing probable sCJD (University of California San Francisco 2007, MRI-CJD Consortium 2009) will enhance the ability to recognize sCJD and implement early safety measures.

Postictal EEG suppression and hippocampal atrophy in temporal lobe epilepsy.

Summary Postictal EEG suppression and slowing recorded with scalp electrodes in patients with partial epilepsy is often maximal over the cortical area of ictal onset. The aim of this study was to determine whether a quantitative relationship exists between immediate postictal EEG suppression and hippocampal atrophy. Immediate postictal EEG was analyzed in 31 scalp-recorded seizures obtained from 8 patients who underwent temporal lobectomy with seizure-free outcomes (2 left, 6 right). Quantitative EEG analysis was performed using a temporal power asymmetry index for each frequency band. The hippocampal asymmetry (left-to-right ratio) based on T1- and T2-weighted MR images was determined by hippocampal volumetric analysis. The relationship between the average temporal power asymmetry index and either T1 or T2 hippocampal asymmetry ratio was assessed for each frequency band using Pearson’s correlation coefficient. Only correlations of the temporal power asymmetry index with T1 hippocampal asymmetry were significant for the total bands (r = 0.768, P < 0.026) and &dgr;-bands (r = 0.728, P < 0.041). The findings suggest that a quantitative relationship exists between postictal EEG suppression in the &dgr;-frequency band and hippocampal atrophy in temporal lobe epilepsy.

Experimental seizures in the frog (Rana pipiens)

We investigated the effects of chemical convulsants in the leopard frog. Systemic kainic acid (5-20 mg/kg) caused limbic-like seizures, with staring, catatonia, fasciculations, and severe motor seizures, which were almost always lethal. Intracerebral electroencephalographic (EEG) recordings showed spike or spike-and-wave patterns at 6-8 Hz that decreased in frequency and increased in amplitude, maximal at an electrode in the midline olfactory/telencephalic (OLF-M) region. With time, an interictal pattern of 100-200 microV periodic spikes developed, followed by diffuse suppression of all brain activity. Seizures induced by pentylenetetrazole (150-450 mg/kg) and bicuculline (5-10 mg/kg) were characterized by the abrupt onset of motor activity, which continued intermittently for several hours, followed by recovery. EEG recordings in animals treated with pentylenetetrazole showed rhythmic spike-and-wave bursts at 1.5-3 Hz that were maximal at OLF-M. Recordings from frogs treated with bicuculline showed repetitive 3-6 Hz spike-and-wave discharges maximal at OLF-M that were nearly constant in amplitude and at times became continuous. Strychnine (1-5 mg/kg) caused reversible seizures characterized by tonic extensions of the extremities, that seemed to originate in the spinal cord. Frogs with recurrent seizures from systemic cis-diamminedichloroplatinum II showed 4-8 Hz rhythmic spike-and-wave activity that gradually slowed in frequency and increased in amplitude. Thus, the frogs reactivity to convulsive agents is similar to that of mammals.

Unihemispheric burst suppression

Burst suppression (BS) consists of bursts of high-voltage slow and sharp wave activity alternating with periods of background suppression in the electroencephalogram (EEG). When induced by deep anesthesia or encephalopathy, BS is bihemispheric and is often viewed as a non-epileptic phenomenon. In contrast, unihemispheric BS is rare and its clinical significance is poorly understood. We describe here two cases of unihemispheric BS. The first patient is a 56-year-old woman with a left temporoparietal tumor who presented in convulsive status epilepticus. EEG showed left hemispheric BS after clinical seizure termination with lorazepam and propofol. The second patient is a 39-year-old woman with multiple medical problems and a vague history of seizures. After abdominal surgery, she experienced a convulsive seizure prompting treatment with propofol. Her EEG also showed left hemispheric BS. In both cases, increasing the propofol infusion rate resulted in disappearance of unihemispheric BS and clinical improvement. The prevailing view that typical bihemispheric BS is non-epileptic should not be extrapolated automatically to unihemispheric BS. The fact that unihemispheric BS was associated with clinical seizure and resolved with propofol suggests that, in both cases, an epileptic mechanism was responsible for unihemispheric BS.