161 Two-centre audit of cannabidiol use in adults with Dravet syndrome

Background

Cannabidiol is a newly-available treatment option for seizures in Dravet syndrome (DS).

Methods

Adults in a cannabidiol early access programme at two epilepsy centres were included. Can- nabidiol was titrated up to 20mg/kg, as tolerated. The primary outcome measure was >30% reduction in convulsive seizures assessed at three months of treatment. Secondary outcome measures included later reduction in seizures and incidence of adverse drug reactions (ADRs).

Results

Eighteen individuals (seven female; median age 27.5 years) with SCN1A mutation-positive DS took part. Median follow-up was 166 days; nine individuals continued on maintenance treatment. Median maximum dose was 18.6mg/kg/day. Four individuals (22.2%) had a >30% reduction in convulsive seizures by three months; in two, this became evident after three months. ADRs occurred in 14 (77.8%). Commonest ADRs were somnolence and derangement of LFTs (all 18 took concomitant valproate), occurring in eight and seven individuals, respectively. ADRs led to discontinuation in three, including a seizure-free individual. Twelve people (66.7%) required dosage changes to other antiepileptic drugs.

Conclusion

Cannabidiol was effective in a fifth of patients. Two additional patients showed later reduction in seizure frequency, suggesting longer follow-up is warranted. Treatment was complicated by ADRs. Dose adjustments of other antiepileptic drugs may be needed.

k.silvennoinen@ucl.ac.uk

Activity-Dependent Gating of Parvalbumin Interneuron Function by the Perineuronal Net Protein Brevican

Activity-dependent neuronal plasticity is a fundamental mechanism through which the nervous system adapts to sensory experience. Several lines of evidence suggest that parvalbumin (PV+) interneurons are essential in this process, but the molecular mechanisms underlying the influence of experience on interneuron plasticity remain poorly understood. Perineuronal nets (PNNs) enwrapping PV+ cells are long-standing candidates for playing such a role, yet their precise contribution has remained elusive. We show that the PNN protein Brevican is a critical regulator of interneuron plasticity. We find that Brevican simultaneously controls cellular and synaptic forms of plasticity in PV+ cells by regulating the localization of potassium channels and AMPA receptors, respectively. By modulating Brevican levels, experience introduces precise molecular and cellular modifications in PV+ cells that are required for learning and memory. These findings uncover a molecular program through which a PNN protein facilitates appropriate behavioral responses to experience by dynamically gating PV+ interneuron function.

Gene therapy in status epilepticus

Gene therapy in human disease has expanded rapidly in recent years with the development of safer and more effective viral vectors, and presents a novel approach to the treatment of epilepsy. Studies in animals models have demonstrated that overexpression of inhibitory peptides can modify seizure threshold, prevent the development of epilepsy, and modify established epilepsy. More recently there has been a flurry of studies using optogenetics in which light-activated channels expressed in neurons can transiently change neuronal excitability on exposure to light, thereby enabling the development of closed loop systems to detect and stop seizure activity. The treatment of status epilepticus presents its own challenges. Because of both the delay in gene expression following transfection and also the necessity of using focal transfection, there are a limited number of situations in which gene therapy can be used in status epilepticus. One such condition is epilepsia partialis continua (EPC). We have used gene therapy in a model of EPC and have shown that we can "cure" the condition. Recent evidence suggesting that gene therapy targeting subcortical regions can modify generalized or more diffuse epilepsies, indicates that the range of situations in status epilepticus in which gene therapy could be used will expand.

Adult-onset NREM parasomnia with hypnopompic hallucinatory pain: a case report

We report the case of a 43-year-old woman presenting with nocturnal episodes of pain and screaming during sleep starting at age 30. There was no childhood or family history of parasomnia. The events had gradually become more frequent over the years, occurring in the first half of the night within 2 h of sleep onset. There were no triggers, and she had partial amnesia for the events. A diagnosis of adult-onset sleep terrors was made on clinical grounds and supported polysomnographically. Seizures and periodic limb movements were excluded as triggering factors. There was some mild sleep disordered breathing (predominantly non-desaturating hypopnea with a propensity for REM sleep of debatable significance). Imaging of the brain and spine and neurophysiological investigations ruled out lesions, entrapments, or neuropathies as possible causes of pain. Treatment (clonazepam, paroxetine, or gabapentin) was poorly tolerated and made no difference to the nocturnal episodes, while trazodone worsened them. This is the first report of hypnopompic psychic pain in association with a NREM parasomnia. We hypothesize that the pain may represent a sensory hallucination analogous to the more commonly recognized visual NREM parasomnia-associated hypnopompic visual hallucinations and that, as such, it may arise during arousal of the sensory neocortex as confabulatory response.

Optogenetic and potassium channel gene therapy in a rodent model of focal neocortical epilepsy

Neocortical epilepsy is frequently drug-resistant. Surgery to remove the epileptogenic zone is only feasible in a minority of cases, leaving many patients without an effective treatment. We report the potential efficacy of gene therapy in focal neocortical epilepsy using a rodent model in which epilepsy is induced by tetanus toxin injection in the motor cortex. By applying several complementary methods that use continuous wireless electroencephalographic monitoring to quantify epileptic activity, we observed increases in high frequency activity and in the occurrence of epileptiform events. Pyramidal neurons in the epileptic focus showed enhanced intrinsic excitability consistent with seizure generation. Optogenetic inhibition of a subset of principal neurons transduced with halorhodopsin targeted to the epileptic focus by lentiviral delivery was sufficient to attenuate electroencephalographic seizures. Local lentiviral overexpression of the potassium channel Kv1.1 reduced the intrinsic excitability of transduced pyramidal neurons. Coinjection of this Kv1.1 lentivirus with tetanus toxin fully prevented the occurrence of electroencephalographic seizures. Finally, administration of the Kv1.1 lentivirus to an established epileptic focus progressively suppressed epileptic activity over several weeks without detectable behavioral side effects. Thus, gene therapy in a rodent model can be used to suppress seizures acutely, prevent their occurrence after an epileptogenic stimulus, and successfully treat established focal epilepsy.

Oscillatory dynamics in the hippocampus support dentate gyrus–CA3 coupling

Gamma oscillations in the dentate gyrus and hippocampal CA3 show variable coherence in vivo, but the mechanisms and relevance for information flow are unknown. We found that carbachol-induced oscillations in rat CA3 have biphasic phase-response curves, consistent with the ability to couple with oscillations in afferent projections. Differences in response to stimulation of either the intrinsic feedback circuit or the dentate gyrus were well described by varying an impulse vector in a two-dimensional dynamical system, representing the relative input to excitatory and inhibitory neurons. Responses to sinusoidally modulated optogenetic stimulation confirmed that the CA3 network oscillation can entrain to periodic inputs, with a steep dependence of entrainment phase on input frequency. CA3 oscillations are therefore suited to coupling with oscillations in the dentate gyrus over a broad range of frequencies.

Evaluating first seizures in adults in primary care

A seizure is defined as the clinical manifestation resulting from an excessive and abnormal discharge of a population of neurones. The individual lifetime risk of developing a non-febrile seizure is about 5% and around a third of patients will experience further seizures and be diagnosed as having epilepsy. When assessing a possible first seizure, assuming that the patient has recovered and is not in an emergency situation, the first question is whether the paroxysmal event was a seizure. There are many seizure imitators, some of which can be fatal if missed. These include cardiac syncope due to arrhythmias, valvular abnormalities or ischaemia, hypotension, hypoglycaemia and TIAs. Ultimately, the diagnosis of a seizure is clinical and is best established by taking an accurate history. An accurate description of the paroxysmal event is paramount. So the patient should ideally bring a witness to the consultation, allow the clinician to contact a witness by phone, or provide a written description of the paroxysm. Further features to be established include type of seizure (generalised or partial) and timing (early morning or nocturnal). The past medical history should be probed for previous syncopal events or possible seizures. Once a putative diagnosis of a seizure has been made, the second question is whether the seizure was provoked or not. Examination should include assessment of the level of consciousness and orientation, and the cardiovascular and nervous systems. In the patient who has fully recovered from a first seizure NICE recommends measuring plasma glucose, and electrolytes including calcium, and a 12-lead ECG. Referral to an emergency department for urgent neuroimaging and lumbar puncture should be considered if the patient has not fully recovered, and/or if risk factors are present. If the patient has fully recovered, guidelines recommend referral to a first seizure clinic for review by an epilepsy specialist.

Failure of caspase inhibition in the double-lesion rat model of striatonigral degeneration (multiple system atrophy)

In the present study we assessed the neuroprotective effects of the pan-caspase inhibitor z-VAD.fmk [N-benzyloxycarbony-valine-alanine-aspartate-(OMe)-fluoromethylketone], and the caspase-3 inhibitor Ac-DEVD.CHO (acetyl-aspartate-chloromethylketone) in the double-lesion rat model of striatonigral degeneration (SND), the core pathology underlying levodopa-unresponsive parkinsonism associated with multiple system atrophy (MSA). Male Wistar rats were divided into three groups, receiving either Ac-DEVD.CHO, z-VAD.fmk or normal saline before lesion surgery, comprising a sequential unilateral quinolinic acid (QA) lesion of the striatum followed by a 6-hydroxydopamine (6-OHDA) lesion of the ipsilateral medial forebrain bundle. At 2 weeks post lesion, all rats underwent testing of spontaneous nocturnal locomotor behavior in an automated Photobeam Activity System (FlexField). Immunohistochemistry was performed with tyrosine hydroxylase, dopamine and cyclic adenosine 3',5'-monophosphate-regulated phosphoprotein and glial fibrillary acidic protein antibodies. Morphometry was performed using computerized image analysis. Behavioral and morphological analysis failed to show striatal or nigral protection in caspase inhibitor-treated animals. Our findings suggest that anti-apoptotic strategies are unrewarding in the SND rat model and, therefore, alternative neuroprotective interventions such as anti-glutamatergic agents or inhibitors of microglial activation should be explored instead.