Immune-mediated polyarthritis and anterior uveitis secondary to zonisamide administration in a dog with refractory epilepsy

The objective of this article is to describe a case of suspected zonisamide-induced immune-mediated polyarthritis (IMPA) and anterior uveitis in a dog. A 7-year-old male neutered Siberian Husky with a history of refractory idiopathic epilepsy was presented for cluster seizures. Following the addition of zonisamide to the antiepileptic regime, the dog developed new IMPA and anterior uveitis. Within a few weeks of discontinuation of the zonisamide, the dog's IMPA and anterior uveitis resolved. These immune-mediated conditions were thus presumed to be an idiosyncratic reaction to zonisamide. To our knowledge, this is the first report of IMPA and anterior uveitis in dogs associated with zonisamide administration at its recommended dose.

The role of neuroinflammation in canine epilepsy

The lack of therapeutics that prevent the development of epilepsy, improve disease prognosis or overcome drug resistance represents an unmet clinical need in veterinary as well as in human medicine. Over the past decade, experimental studies and studies in human epilepsy patients have demonstrated that neuroinflammatory processes are involved in epilepsy development and play a key role in neuronal hyperexcitability that underlies seizure generation. Targeting neuroinflammatory signaling pathways may provide a basis for clinically relevant disease-modification strategies in general, and moreover, could open up new therapeutic avenues for human and veterinary patients with drug-resistant epilepsy. A sound understanding of the neuroinflammatory mechanisms underlying seizure pathogenesis in canine patients is therefore essential for mechanism-based discovery of selective epilepsy therapies that may enable the development of new disease-modifying treatments. In particular, subgroups of canine patients in urgent needs, e.g. dogs with drug-resistant epilepsy, might benefit from more intensive research in this area. Moreover, canine epilepsy shares remarkable similarities in etiology, disease manifestation, and disease progression with human epilepsy. Thus, canine epilepsy is discussed as a translational model for the human disease and epileptic dogs could provide a complementary species for the evaluation of antiepileptic and antiseizure drugs. This review reports key preclinical and clinical findings from experimental research and human medicine supporting the role of neuroinflammation in the pathogenesis of epilepsy. Moreover, the article provides an overview of the current state of knowledge regarding neuroinflammatory processes in canine epilepsy emphasizing the urgent need for further research in this specific field. It also highlights possible functional impact, translational potential and future perspectives of targeting specific inflammatory pathways as disease-modifying and multi-target treatment options for canine epilepsy.

Pathophysiology of drug-resistant canine epilepsy

Drug resistance continues to be a major clinical problem in the therapeutic management of canine epilepsies with substantial implications for quality of life and survival times. Experimental and clinical data from human medicine provided evidence for relevant contributions of intrinsic severity of the disease as well as alterations in pharmacokinetics and -dynamics to failure to respond to antiseizure medications. In addition, several modulatory factors have been identified that can be associated with the level of therapeutic responses. Among others, the list of potential modulatory factors comprises genetic and epigenetic factors, inflammatory mediators, and metabolites. Regarding data from dogs, there are obvious gaps in knowledge when it comes to our understanding of the clinical patterns and the mechanisms of drug-resistant canine epilepsy. So far, seizure density and the occurrence of cluster seizures have been linked with a poor response to antiseizure medications. Moreover, evidence exists that the genetic background and alterations in epigenetic mechanisms might influence the efficacy of antiseizure medications in dogs with epilepsy. Further molecular, cellular, and network alterations that may affect intrinsic severity, pharmacokinetics, and -dynamics have been reported. However, the association with drug responsiveness has not yet been studied in detail. In summary, there is an urgent need to strengthen clinical and experimental research efforts exploring the mechanisms of resistance as well as their association with different etiologies, epilepsy types, and clinical courses.

Translational veterinary epilepsy: A win-win situation for human and veterinary neurology

Epilepsy is a challenging multifactorial disorder with a complex genetic background. Our current understanding of the pathophysiology and treatment of epilepsy has substantially increased due to animal model studies, including canine studies, but additional basic and clinical research is required. Drug-resistant epilepsy is an important problem in both dogs and humans, since seizure freedom is not achieved with the available antiseizure medications. The evaluation and exploration of pharmacological and particularly non-pharmacological therapeutic options need to remain a priority in epilepsy research. Combined efforts and sharing knowledge and expertise between human medical and veterinary neurologists are important for improving the treatment outcomes or even curing epilepsy in dogs. Such interactions could offer an exciting approach to translate the knowledge gained from people and rodents to dogs and vice versa. In this article, a panel of experts discusses the similarities and knowledge gaps in human and animal epileptology, with the aim of establishing a common framework and the basis for future translational epilepsy research.

Cannabidiol in canine epilepsy

The anticonvulsant effect of cannabidiol (CBD), which has been confirmed by findings from animal models and human trials, has attracted the interest of veterinary practitioners and dog owners. Moreover, social media and public pressure has sparked a renewed awareness of cannabinoids, which have been used for epilepsy since ancient times. Unfortunately, at this moment veterinarians and veterinary neurologists have difficulty prescribing cannabinoids because of the paucity of sound scientific studies. Pharmacokinetic studies in dogs have demonstrated a low oral bioavailability of CBD and a high first-pass effect through the liver. Administering CBD in oil-based formulations and/or with food has been shown to enhance the bioavailability in dogs, rats and humans. Tolerability studies in healthy dogs and dogs with epilepsy have demonstrated that CBD was safe and well tolerated with only mild to moderate adverse effects. In this context, it should be noted that the quality of available CBD varies widely, underscoring the importance of pharmaceutical quality and its control. One clinical trial in dogs with drug-resistant idiopathic epilepsy failed to confirm a difference in response rates between the CBD group and the placebo group, while in another cross-over trial a ≥ 50 % reduction in epileptic seizure frequency was found in six of 14 dogs in the treatment phase, a reduction that was not observed during the placebo phase. Based on the current state of knowledge it is not possible to provide clear-cut recommendations for the use of CBD in canine epilepsy. Randomized controlled canine trials with large sample sizes are needed to determine the range of therapeutic plasma concentrations, develop evidence-based dosing regimens, determine the efficacy of cannabidiol in drug-refractory epilepsy, and explore potential associations between treatment effects and different etiologies, epilepsy types, and drug combinations.

Neurosurgery in feline epilepsy, including clinicopathology of feline epilepsy syndromes

Feline epilepsy is treated with antiseizure medications, which achieves fair to good seizure control. However, a small subset of feline patients with drug-resistant epilepsy requires alternative therapies. Furthermore, approximately 50 % of cats with epileptic seizures are diagnosed with structural epilepsy with or without hippocampal abnormality and may respond to surgical intervention. The presence of hippocampal pathology and intracranial tumors is a key point to consider for surgical treatment. This review describes feline epilepsy syndrome and epilepsy-related pathology, and discusses the indications for and availability of neurosurgery, including lesionectomy, temporal lobectomy with hippocampectomy, and corpus callosotomy, for cats with different epilepsy types.

Neurosurgery in canine epilepsy

Epilepsy surgery is functional neurosurgery applied to drug-resistant epilepsy. Although epilepsy surgery has been established and achieves fair to good outcomes in human medicine, it is still an underdeveloped area in veterinary medicine. With the spread of advanced imaging and neurosurgical modalities, intracranial surgery has become commonplace in the veterinary field, and, therefore, it is natural that expectations for epilepsy surgery increase. This review summarizes current standards of intracranial epilepsy surgery in human medicine and describes its current status and expectation in veterinary medicine. Intracranial epilepsy surgery is classified generally into resection surgery, represented by cortical resection, lobectomy, and lesionectomy, and disconnection surgery, such as corpus callosotomy and multiple subpial transection. In dogs with drug-resistant epilepsy, corpus callosotomy is available as a disconnection surgery for generalized epilepsy. However, other types of disconnection and resection surgeries for focal epilepsy are limited to experimental studies in laboratory dogs and/or anecdotal case reports of lesionectomy, such as tumor or encephalocele removal, without epileptogenic evidence. Veterinary epilepsy surgery is a new and challenging neurosurgery field; with the development of presurgical evaluations such as advanced electroencephalography and neuroimaging, it may become more readily practiced.

Closed-Loop Neurostimulators: A Survey and A Seizure-Predicting Design Example for Intractable Epilepsy Treatment

First, existing commercially available open-loop and closed-loop implantable neurostimulators are reviewed and compared in terms of their targeted application, physical size, system-level features, and performance as a medical device. Next, signal processing algorithms as the primary strength point of the closed-loop neurostimulators are reviewed, and various design and implementation requirements and trade-offs are discussed in details along with quantitative examples. The review results in a set of guidelines for algorithm selection and evaluation. Second, the implementation of an inductively-powered seizure-predicting microsystem for monitoring and treatment of intractable epilepsy is presented. The miniaturized system is comprised of two miniboards and a power receiver coil. The first board hosts a 24-channel neurostimulator system on chip fabricated in a [Formula: see text] CMOS technology and performs neural recording, on-chip digital signal processing, and electrical stimulation. The second board communicates recorded brain signals as well as signal processing results wirelessly. The multilayer flexible coil receives inductively-transmitted power. The system is sized at 2 × 2 × 0.7 [Formula: see text] and weighs 6 g. The approach is validated in the control of chronic seizures in vivo in freely moving rats.