Diagnostic utility of prolonged ambulatory video-electroencephalography monitoring

OBJECTIVES

Ambulatory video-electroencephalography (video-EEG) represents a low-cost, convenient and accessible alternative to inpatient video-EEG monitoring, however few studies have examined their diagnostic yield. In this large-scale retrospective study conducted in Australia, we evaluated the efficacy of prolonged ambulatory video-EEG recordings in capturing diagnostic events and resolving the referring question.

METHODS

Sequential adult and paediatric ambulatory video-EEG reports from April 2020 to June 2021 were reviewed retrospectively. Data collection included patient demographics, clinical information, and details of events and EEG abnormalities. Clinical utility was assessed by examining i) time to first diagnostic event, and ii) ability to resolve the referring questions - seizure localisation, quantification, classification, and differentiation (differentiating seizures from non-epileptic events).

RESULTS

Of the 600 reports analysed, 49 % captured at least one event, and 45 % captured interictal abnormalities (epileptiform or non-epileptiform). Seizures, probable psychogenic events (mostly non-convulsive), and other non-epileptic events occurred in 13 %, 23 % and 21 % of recordings respectively, with overlap. Unreported events were captured in 53 (9 %) recordings, and unreported seizures represented more than half of all seizures captured (51 %, 392/773). Nine percent of events were missing clinical, video or electrographic data. A diagnostic event occurred in 244 (41 %) recordings, of which 14 % were captured between the fifth and eighth day of recording. Reported event frequency ≥ 1/week was the only significant predictor of diagnostic event capture. In recordings with both seizures and psychogenic events, unrecognized seizures were frequent, and seizures may be missed if recording is terminated early. The referring question was resolved in 85 % of reports with at least one event, and 53 % of all reports. Specifically, this represented 46 % of reports (235/512) for differentiation of events, and 75 % of reports (27/36) for classification of seizures.

CONCLUSION

Ambulatory video-EEG recordings are of high diagnostic value in capturing clinically relevant events and resolving the referring clinical questions.

The efficacy and tolerability of adjunctive brivaracetam for the treatment of adult epilepsy: An Australian multi-center retrospective real-world observational cohort study

OBJECTIVE

Assess the efficacy and tolerability of add-on therapy brivaracetam (BRV) in adult patients with epilepsy in a real-world setting.

METHODS

This multi-center retrospective observational cohort study examined all adult patients who commenced on BRV at 11 Australian epilepsy centers between 2017 and 2020. Primary outcomes were seizure response (≥50% reduction in frequency) and seizure freedom 12 months post BRV commencement, and tolerability. We report three approaches to missing data (complete case analysis, CCA; last observation carried forward, LOCF; and intention to treat, ITT). Secondary outcomes included the durability of early BRV response and continuous seizure freedom from BRV initiation. Subgroup analysis examined patients with focal and generalized epilepsy and patients with refractory (≥4 prior ASMs) and highly refractory (≥7 prior ASMs) epilepsy. Outcomes were also assessed at 'personalized' seizure outcome time points based on baseline seizure frequency.

RESULTS

Baseline and follow-up data were available for 228 patients. The mean age was 41.5 years (IQR 30, 50). Most had focal epilepsy (188/228, 82.5%). Median number of previous ASMs was 4 (2, 7), and concomitant ASMs 2 (2, 3). Twelve-month responder rate was: 46.3% using CCA (95% CI 34.0, 58.9); 39.5% using LOCF (33.1, 46.1); and 15.4% using ITT (10.9, 20.7). Twelve-month seizure freedom was: 23.9% using CCA (14.3, 35.9); 24.6% using LOCF (19.1, 30.7); and 7.9% using ITT (4.7, 12.1). The most frequent adverse effects were sedation or cognitive slowing (33/228, 14.5%), irritability or aggression (16/228, 7.0%), and low mood (14/228, 6.1%). Outcomes were similar using continuous outcome definitions and 'personalized' outcome assessment time points. Early responses were highly durable, with 3-month response maintained at all subsequent time points at 83%, and seizure freedom maintained at 85%. Outcomes were similar in focal (n = 187) and generalizsed (n = 25) subgroups. Outcomes were similar in refractory patients (n = 129), but lower in the highly refractory group (n = 62), however improvement with BRV was still observed with 12-month seizure freedom of 8.3% using CCA (1.0, 27), 6.5% using LOCF (1.8, 15.7); and 3.2% using ITT (0.4, 11.2).

CONCLUSIONS

Meaningful real-world responder and seizure freedom rates can be still observed in a refractory epilepsy population. Brivaracetam response can occur early and appears to be maintained with minimal later relapse. The results should be interpreted with caution given the retrospective nature of the study and the quantities of missing data at later time points.

Pre-hospital benzodiazepines associated with improved outcomes in out-of-hospital status epilepticus: A 10-year retrospective cohort study

Outcomes of status epilepticus have not substantially changed over the last decade. Given onset is most often in the community, early termination strategies that are implementable outside of hospitals are of public health importance. This 10-year retrospective single-centre cohort study aimed to determine whether pre-hospital benzodiazepine administration is associated with improved health outcomes in patients with out-of-hospital onset status epilepticus.

METHODS

We reviewed the medical records of all patients admitted with status epilepticus between 2008 and 2018 at St Vincent's Hospital Melbourne. Data regarding onset setting, medical history, management and outcomes were extracted.

RESULTS

72 patients meeting inclusion criteria were identified. Onset of status epilepticus was out-of-hospital for 74% (53/72) of patients, 66% (35/53) of whom were administered a benzodiazepine before reaching hospital, most often by ambulance officers (30/35, 86%). Pre-hospital benzodiazepine administration was associated with a 90% reduction in duration time to seizure cessation (0.65 vs 5.8 days, p = 0.012) and 50% reduction in length of hospital stay (7.6 vs 15.8 days, p = 0.045). In-hospital onset status epilepticus was associated with higher mortality than out-of-hospital onset (26% vs 4%, RR 6.5, p = 0.004).

CONCLUSION

Pre-hospital benzodiazepines shorten the time to seizure control and length of hospital stay in patients with out-of-hospital status epilepticus, although is under-utilised by both ambulance staff and home carers. Health policy measures to improve ambulance officer and home carer administration skills and confidence may address these issues.

Multiday cycles of heart rate are associated with seizure likelihood: An observational cohort study

Background

Circadian and multiday rhythms are found across many biological systems, including cardiology, endocrinology, neurology, and immunology. In people with epilepsy, epileptic brain activity and seizure occurrence have been found to follow circadian, weekly, and monthly rhythms. Understanding the relationship between these cycles of brain excitability and other physiological systems can provide new insight into the causes of multiday cycles. The brain-heart link has previously been considered in epilepsy research, with potential implications for seizure forecasting, therapy, and mortality (i.e., sudden unexpected death in epilepsy).

Methods

We report the results from a non-interventional, observational cohort study, Tracking Seizure Cycles. This study sought to examine multiday cycles of heart rate and seizures in adults with diagnosed uncontrolled epilepsy (N=31) and healthy adult controls (N=15) using wearable smartwatches and mobile seizure diaries over at least four months (M=12.0, SD=5.9; control M=10.6, SD=6.4). Cycles in heart rate were detected using a continuous wavelet transform. Relationships between heart rate cycles and seizure occurrence were measured from the distributions of seizure likelihood with respect to underlying cycle phase.

Findings

Heart rate cycles were found in all 46 participants (people with epilepsy and healthy controls), with circadian (N=46), about-weekly (N=25) and about-monthly (N=13) rhythms being the most prevalent. Of the participants with epilepsy, 19 people had at least 20 reported seizures, and 10 of these had seizures significantly phase locked to their multiday heart rate cycles.

Interpretation

Heart rate cycles showed similarities to multiday epileptic rhythms and may be comodulated with seizure likelihood. The relationship between heart rate and seizures is relevant for epilepsy therapy, including seizure forecasting, and may also have implications for cardiovascular disease. More broadly, understanding the link between multiday cycles in the heart and brain can shed new light on endogenous physiological rhythms in humans.

Funding

This research received funding from the Australian Government National Health and Medical Research Council (investigator grant 1178220), the Australian Government BioMedTech Horizons program, and the Epilepsy Foundation of America's ‘My Seizure Gauge’ grant.

Evaluation of the Biocompatibility of Polypyrrole Implanted Subdurally in GAERS

This blinded controlled prospective randomized study investigates the biocompatibility of polypyrrole (PPy) polymer that will be used for intracranial triggered release of anti-epileptic drugs (AEDs). Three by three millimeters PPy are implanted subdurally in six adult female genetic absence epilepsy rats from Strasbourg. Each rat has a polymer implanted on one side of the cortex and a sham craniotomy performed on the other side. After a period of seven weeks, rats are euthanized and parallel series of coronal sections are cut throughout the implant site. Four series of 15 sections are histological (hematoxylin and eosin) and immunohistochemically (neuron-specific nuclear protein, glial fibrillary acidic protein, and anti-CD68 antibody) stained and evaluated by three investigators. The results show that implanted PPy mats do not induce obvious inflammation, trauma, gliosis, and neuronal toxicity. Therefore the authors conclude the PPy used offer good histocompatibility with central nervous system cells and that PPy sheets can be used as intracranial, AED delivery implant.

Injectable phenytoin loaded polymeric microspheres for the control of temporal lobe epilepsy in rats

PURPOSE

Epilepsy is a prevalent neurological disorder with a high frequency of drug resistance. While significant advancements have been made in drug delivery systems to overcome anti-epileptic drug resistance, efficacies of materials in biological systems have been poorly studied. The purpose of the study was to evaluate the anti-epileptic effects of injectable poly(epsilon-caprolactone) (PCL) microspheres for controlled release of an anticonvulsant, phenytoin (PHT), in an animal model of epilepsy.

METHODS

PHT-PCL and Blank-PCL microspheres formulated using an oil-in-water (O/W) emulsion solvent evaporation method were evaluated for particle size, encapsulation efficiency, surface morphology and in-vitro drug release profile. Microspheres with the most suitable morphology and release characteristics weresubsequently injected into the hippocampus of a rat tetanus toxin model of temporal lobe epilepsy. Electrocorticography (ECoG)from the cerebral cortex were recorded for all animals. The number of seizure events, severity of seizures, and seizure duration were then compared between the two treatment groups.

RESULTS

We have shown that small injections of drug-loaded microspheres are biologically tolerated and released PHT can control seizures for the expected period of time that is in accord with in-vitro release data.

CONCLUSION

The study demonstrated the feasibility of polymer-based delivery systems incontrolling focal seizures.

Novel methods of antiepileptic drug delivery -- polymer-based implants

Epilepsy is a neurological disorder characterised by spontaneous seizures. Over one third of patients receive insufficient benefit from oral anti-epileptic drug (AED) therapy, and continue to experience seizures whilst on medication. Epilepsy researchers are consequently seeking new ways to deliver AEDs directly to the seizure focus in the brain in order to deliver higher, more effective doses to the seizure focus whilst bypassing the remainder of the brain and body to prevent side effects. The focus of this review will be polymer-based implants, which are polymeric devices loaded with AED that are designed for implantation at the seizure focus in order to achieve gradual, continuous release of AED direct into the region of the brain responsible for seizures. Polymer-based implants produced for epilepsy to date are based on a range of polymers, both biodegradable and non-biodegradable, and range from simple materials development studies through to investigations of implants in animal models of seizures and epilepsy, with varying degrees of success. This review describes the range of methods employed to manufacture polymer-based implants and compares their advantages and potential appeal to industry, and describes and compares the results and successes of polymer-based materials and devices produced to date for the treatment of epilepsy. We also discuss disadvantages and hurdles to be overcome in the field, and describe our predictions for advances to be made in the field in the coming decade.

Exploring the tolerability of spatiotemporally complex electrical stimulation paradigms

A modified cortical stimulation model was used to investigate the effects of varying the synchronicity and periodicity of electrical stimuli delivered to multiple pairs of electrodes on seizure initiation. In this model, electrical stimulation of the motor cortex of rats, along four pairs of a microwire electrode array, results in an observable seizure with quantifiable electrographic duration and behavioural severity. Periodic stimuli had a constant inter-stimulus intervals across the two-second stimulus duration, whilst synchronous stimuli consisted of singular biphasic, bipolar pulses delivered to the four pairs of electrodes at precisely the same time for the entire two second stimulation period. In this way four combinations of stimulation were possible; periodic/synchronous (P/S), periodic/asynchronous (P/As), aperiodic/synchronous (Ap/S) and aperiodic/asynchronous (Ap/As). All stimulation types were designed with equal pulse width, current intensity and mean frequency of stimulation (60 Hz), standardizing net charge transfer. It was expected that the periodicity of the stimulus would be the primary determinant of seizure initiation and therefore severity and electrographic duration. However, the results showed that significant differences in both severity and duration only occurred when the synchronicity was altered. For periodic stimuli, synchronous delivery increased median seizure duration from 5 s to 13 s and increased median Racine severity from 1 to 3. In the aperiodic case, synchronous stimulus delivery increased median duration from 5.5 s to 11s and resulted in seizures of median severity 3 vs. 0 in the asynchronous case. These findings may have implications for the design of future neurostimulation waveform designs as higher numbers of electrodes and stimulator output channels become available in next generation implants.

Seizure severity and duration in the cortical stimulation model of experimental epilepsy in rats: a longitudinal study

The aim of this study was to determine the current intensities necessary to elicit three levels of varying EEG and behavioural phenomena with electrical stimulation, and also to determine the consistency of the EEG and behavioural components of the triggered seizures over time. Electrical stimulation of the primary motor/somatosensory cortex was performed in 16 adult rats with multichannel microwire electrode arrays. Stimulation was delivered at a frequency of 60 Hz (1 ms pulse width), for 2 s duration, as biphasic rectangular pulses over four of the eight available electrode pairs. Current intensity thresholds for interruption of normal behaviour, epileptiform afterdischarge (EAD) longer than 5 s and motor seizures with Racine severity greater than 3 were not correlated to time post-surgery. The Racine threshold was shown to be negatively correlated to the EAD duration and Racine severity of seizures elicited in the following sessions. Seizures were reliably generated in rats through cortical stimulation with microwire electrode arrays and these seizures were not shown to be subject to any kindling type effects up to 53 days post-implantation. Both the electrographic duration and behavioural severity of stimulated seizures remained, on average, constant during this experimental period. Approximately one-third of stimulations did not cause observable motor seizures and of those that did result in seizures, forelimb clonus was the most common manifestation and the mean EAD duration was 18.5 s. No damage beyond that caused by surgical implantation of electrodes was observed in the histological analyses of stimulated and non-stimulated tissue. The consistency, duration and severity of seizures within this timeframe make this cortical stimulation model suitable for investigations into novel therapeutic interventions for epilepsy that require a known seizure focus.

Brain region-specific studies of the excitatory behavioral effects of morphine-3-glucuronide

This study was designed to determine in rats whether morphine-3-glucuronide (M3G) produces its neuro-excitatory effects most potently in the ventral hippocampus (as has been reported previously for subanalgesic doses of opioid peptides). Guide cannulae were implanted into one of seven regions of the rat brain: lateral ventricle; ventral, CA1 and CA2-CA3 regions of the hippocampus; amygdala; striatum or cortex. After a 7 day recovery period, rats received intracerebral injections of (i) M3G (1.1 or 11 nmol) (ii) DADLE ([D-Ala2,D-Leu5]enkephalin), (45 nmol, positive controls) or (iii) vehicle (deionised water), and behavioral excitation was quantified over 80 min. High-dose M3G (11 nmol) evoked behavioral excitation in all brain regions but the onset, severity and duration of these effects varied considerably among brain regions. By contrast, low-dose M3G (1.1 nmol) evoked excitatory behaviors only when administered into the ventral hippocampus and the amygdala, with the most potent effects being observed in the ventral hippocampus. Prior administration of the nonselective opioid antagonists, naloxone and beta-funaltrexamine into the ventral hippocampus, markedly attenuated low-dose M3G's excitatory effects but did not significantly alter levels of excitation evoked by high-dose M3G. Naloxone given 10 min after M3G (1.1 or 11 nmol) did not significantly attenuate behavioral excitation. Thus, M3G's excitatory behavioral effects occur most potently in the ventral hippocampus as reported previously for subanalgesic doses of opioid peptides, and appear to be mediated through at least two mechanisms, one possibly involving excitatory opioid receptors and the other, non-opioid receptors.

Evaluation of the immunogenicity of attenuated feline calicivirus vaccines by ELISA

An ELISA test was developed to measure the levels of IgG antibody in specific-pathogen-free (SPF) cats immunised with two doses of an attenuated feline calicivirus (FCV) vaccine. All eight vaccinates were protected from virus challenge, but four out of five non-vaccinates were not. There was a significant difference in respect of protection from virus challenge between SPF cats with and without three-fold or greater increase in antibody units (P = 0.01). Each serum absorbance was standardised against the reference positive which has an arbitrary value of 100 antibody units. In SPF cats, the 99% confidence level for seropositivity to FCV was determined as greater than or equal to 2.5 antibody units. The results suggest that the sensitive ELISA test can be used to monitor the antibody status of SPF cat colonies prior to FCV vaccine trials, and to measure the immunogenicity of attenuated FCV vaccines. Thus, the ELISA test may replace the need for virus challenge, with consequent reduction in animals used in future FCV vaccine trials.