A retrospective case series of clinical signs in 28 Beagles with Lafora disease

Characteristics and clinical course of myoclonus in Cavalier King Charles Spaniels

BACKGROUND

Myoclonus has been described in aging Cavalier King Charles Spaniels (CKCS), but the natural course of the disease and response to treatment have not been described.

OBJECTIVES

Report the clinical features and course of myoclonus in CKCS.

ANIMALS

Twenty-seven caregivers provided questionnaire responses at a median of 24 months after the onset of myoclonus in their CKCS. Fifteen caregivers completed a second follow-up questionnaire at a median of 17 months after submission of the first questionnaire.

METHODS

The caregivers of affected CKCS were invited to provide video footage for review. Owners of CKCS with videos demonstrating myoclonus then completed the online questionnaire for further evaluation. A second shortened questionnaire was sent to participants at least 6 months after completion of the first.

RESULTS

Most CKCS displayed spontaneous myoclonus affecting predominantly the head (25/27). Overall, the majority had episodes that increased in frequency (20/27) and severity (17/27). Eighteen dogs had developed changes in behavior since the onset of myoclonus. These dogs were typically older and had experienced myoclonic episodes for longer than dogs without behavioral changes. Generalized epileptic seizures were reported in 4/27 dogs. Ten dogs received medical treatment. Eight were prescribed levetiracetam; all had an initial decrease in episode frequency, but a subsequent increase in both frequency and severity of episodes was common.

CONCLUSIONS AND CLINICAL IMPORTANCE

Myoclonus in CKCS tends to progress in frequency and severity regardless of treatment. Progressive behavioral changes suggestive of cognitive decline are common. These findings support the possibility of an underlying neurodegenerative process.

Electroencephalography: electrode arrays in dogs

Electroencephalography (EEG) is the gold standard for confirming epileptic seizures in both human and veterinary patients. Despite idiopathic epilepsy being one of the most common neurological conditions in dogs, our understanding of it in veterinary medicine lags that in human medicine. The relative underuse of EEG in dogs with seizures has potential causes including practical issues, financial concerns, lack of training/equipment, and questions of clinical value. This technological underuse may lead to, or result from, major gaps in our understanding of EEG in veterinary patients. This underutilization of EEG is of significant clinical relevance because the diagnosis of specific epilepsy syndromes in humans guides the treatment, namely pharmacological, dietary, or surgical. These epilepsy syndromes are diagnosed based on several factors, one of which is the characteristic electrical brain activity on EEG. The aim of this narrative literature review was to highlight the study of cortical brain activity to improve our understanding of EEG in veterinary medicine. Specifically, the utility of EEG with focus on the existing proposed electrode arrays and their current supporting evidence. A recent survey study confirmed that a variety of canine EEG protocols are concurrently in use, including diverse electrode arrays. By comparison, in humans there is a standardized 10-20 electrode array, with average localization error of 13-17 mm depending on the number of placed electrodes on the scalp. We offer a review of the factors that would contribute to the ideal canine EEG electrode array highlighting areas for improvement and future validation. This proposed level of understanding will facilitate the identification of cortical seizure foci with a known degree of error, paving the way for non-pharmaceutical interventions like epilepsy surgeries.

A diffusion tensor imaging white matter atlas of the domestic canine brain

There is increasing reliance on magnetic resonance imaging (MRI) techniques in both research and clinical settings. However, few standardized methods exist to permit comparative studies of brain pathology and function. To help facilitate these studies, we have created a detailed, MRI-based white matter atlas of the canine brain using diffusion tensor imaging. This technique, which relies on the movement properties of water, permits the creation of a three-dimensional diffusivity map of white matter brain regions that can be used to predict major axonal tracts. To generate an atlas of white matter tracts, thirty neurologically and clinically normal dogs underwent MRI imaging under anesthesia. High-resolution, three-dimensional T1-weighted sequences were collected and averaged to create a population average template. Diffusion-weighted imaging sequences were collected and used to generate diffusivity maps, which were then registered to the T1-weighted template. Using these diffusivity maps, individual white matter tracts-including association, projection, commissural, brainstem, olfactory, and cerebellar tracts-were identified with reference to previous canine brain atlas sources. To enable the use of this atlas, we created downloadable overlay files for each white matter tract identified using manual segmentation software. In addition, using diffusion tensor imaging tractography, we created tract files to delineate major projection pathways. This comprehensive white matter atlas serves as a standard reference to aid in the interpretation of quantitative changes in brain structure and function in clinical and research settings.

Magnetic resonance imaging pattern recognition of metabolic and neurodegenerative encephalopathies in dogs and cats

Metabolic/neurodegenerative encephalopathies encompass a wide list of conditions that share similar clinical and magnetic resonance imaging (MRI) characteristics, challenging the diagnostic process and resulting in numerous tests performed in order to reach a definitive diagnosis. The aims of this multicentric, retrospective and descriptive study are: (I) to describe the MRI features of dogs and cats with metabolic/neurodegenerative encephalopathies; (II) to attempt an MRI recognition pattern classifying these conditions according to the involvement of grey matter, white matter or both; and (III) to correlate the MRI findings with previous literature. A total of 100 cases were recruited, comprising 81 dogs and 19 cats. These included hepatic encephalopathy (20 dogs and three cats), myelinolysis (five dogs), intoxications (seven dogs and one cat), thiamine deficiency (two dogs and seven cats), hypertensive encephalopathy (three dogs and two cats), neuronal ceroid lipofuscinosis (11 dogs and one cat), gangliosidosis (three dogs and two cats), fucosidosis (one dog), L-2-hydroxyglutaric aciduria (13 dogs and one cat), Lafora disease (11 dogs), spongiform leukoencephalomyelopathy (one dog) and cerebellar cortical degeneration (four dogs and two cats). None of the hepatic encephalopathies showed the previously described T1-weighted hyperintensity of the lentiform nuclei. Instead, there was involvement of the cerebellar nuclei (8/23), which is a feature not previously described. Dogs with myelinolysis showed novel involvement of a specific white matter structure, the superior longitudinal fasciculus (5/5). Thiamine deficiency affected numerous deep grey nuclei with novel involvement of the oculomotor nuclei (3/9), thalamic nuclei, subthalamus and cerebellar nuclei (1/9). Cats with hypertensive encephalopathy had a more extensive distribution of the white matter changes when compared to dogs, extending from the parietal and occipital lobes into the frontal lobes with associated mass effect and increased brain volume. Lysosomal storage disease showed white matter involvement only, with neuronal ceroid lipofuscinosis characterised by severe brain atrophy when compared to gangliosidosis and fucosidosis. All patients with L-2-hydroxyglutaric aciduria had a characteristic T2-weighted hyperintense swelling of the cerebral and cerebellar cortical grey matter, resulting in increased brain volume. Lafora disease cases showed either normal brain morphology (5/11) or mild brain atrophy (6/11). Dogs with cerebellar cortical degeneration had more marked cerebellar atrophy when compared to cats. This study shows the important role of MRI in distinguishing different metabolic/neurodegenerative encephalopathies according to specific imaging characteristics.

Use of levetiracetam for the successful treatment of suspected myoclonic seizures: five dogs (2016-2022)

OBJECTIVES

Myoclonic seizures are considered a type of generalised seizure characterised by brief, jerking movements of the body. The aim of this study is to describe cases of suspected canine myoclonic seizure of idiopathic aetiology and to discuss the successful use of the anticonvulsant levetiracetam as treatment in each of these cases.

MATERIALS AND METHODS

Dogs with epileptic myoclonus suspected to be idiopathic in aetiology were considered for inclusion. Medical records were reviewed for physical and neurologic examination findings, clinicopathologic results, and diagnostic imaging results. All included dogs were treated with levetiracetam, and their response was reported.

RESULTS

Five dogs were included, all of which had suspected myoclonic seizures either observed in-person or on video recording by a board-certified veterinary neurologist. The duration of myoclonic seizures preceding treatment ranged from one day to one year. One dog also experienced a generalised tonic-clonic seizure. All dogs were treated with levetiracetam. Two dogs experienced long-term myoclonic seizure freedom (duration seizure-free of at least 1 year), and two dogs experienced marked decreased myoclonic seizure frequency. One dog experienced immediate abatement of myoclonic seizures, although levetiracetam was only utilised for 1 month following onset of myoclonic seizures in this patient.

CLINICAL SIGNIFICANCE

Myoclonic seizures can be idiopathic in aetiology. Levetiracetam can be used effectively to rapidly stop myoclonic seizures and to decrease the frequency of myoclonic seizures.

Clinical Signs in 166 Beagles with Different Genotypes of Lafora

Lafora disease (LD) is a genetic disease affecting beagles, resulting in seizures in combination with other signs. The aim of this study was to describe the clinical signs of LD in beagles with different NHLRC1 genotypes. One hundred and sixty-six beagles were tested for an NHLRC1 gene defect: L/L (n = 67), N/L (n = 32), N/N (n = 67). Owners were asked to participate in a survey about the clinical signs of LD in their dogs. These were recorded for the three possible genotypes in the two age groups, <6 years and ≥6 years. In all genotypes, nearly all the signs of LD were described. In the age group ≥ 6 years, however, they were significantly more frequent in beagles with the L/L genotype. If the following three clinical signs occur together in a beagle ≥ 6 years-jerking of the head, photosensitivity and forgetting things he/she used to be able to do-98.2% of these dogs are correctly assigned to the L/L genotype. If one or two of these signs are missing, the correct classification decreases to 92.1% and 13.2%, respectively. Only the combination of certain signs truly indicates the L/L genotype. Yet, for many dogs, only genetic testing will provide confirmation of the disease.

Polyglucosan body disease in an aged chimpanzee (Pan troglodytes)

A 57-year-old female chimpanzee presented with a brief history of increasing lethargy and rapidly progressive lower-limb weakness that culminated in loss of use. Postmortem examination revealed no significant gross lesions in the nervous system or other organ systems. Histological analysis revealed round, basophilic to amphophilic polyglucosan bodies (PGBs) in the white and gray matter of the cervical, thoracic, lumbar, and coccygeal regions of spinal cord. Only rare PGBs were observed in forebrain samples. The lesions in the spinal cord were polymorphic, and they were positively stained with hematoxylin, periodic acid Schiff, Alcian blue, toluidine blue, Bielschowsky silver, and Grocott-Gomori methenamine-silver methods, and they were negative for von Kossa and Congo Red stains. Immunohistochemical evaluation revealed reactivity with antibodies to ubiquitin, but they were negative for glial fibrillary acidic protein, neuron-specific enolase, neurofilaments, tau protein, and Aβ protein. Electron microscopy revealed non-membrane-bound deposits composed of densely packed filaments within axons and in the extracellular space. Intra-axonal PGBs were associated with disruption of the axonal fine structure and disintegration of the surrounding myelin sheath. These findings are the first description of PGBs linked to neurological dysfunction in a chimpanzee. Clinicopathologically, the disorder resembled adult PGB disease in humans.

An Overview of Canine Inherited Neurological Disorders with Known Causal Variants

Hereditary neurological conditions documented in dogs encompass congenital, neonatal, and late-onset disorders, along with both progressive and non-progressive forms. In order to identify the causal variant of a disease, the main two approaches are genome-wide investigations and candidate gene investigation. Online Mendelian Inheritance in Animals currently lists 418 Mendelian disorders specific to dogs, of which 355 have their likely causal genetic variant identified. This review aims to summarize the current knowledge on the canine nervous system phenes and their genetic causal variant. It has been noted that the majority of these diseases have an autosomal recessive pattern of inheritance. Additionally, the dog breeds that are more prone to develop such diseases are the Golden Retriever, in which six inherited neurological disorders with a known causal variant have been documented, and the Belgian Shepherd, in which five such disorders have been documented. DNA tests can play a vital role in effectively managing and ultimately eradicating inherited diseases.

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.

Dogs as a Natural Animal Model of Epilepsy

Epilepsy is a common neurological disease in both humans and domestic dogs, making dogs an ideal translational model of epilepsy. In both species, epilepsy is a complex brain disease characterized by an enduring predisposition to generate spontaneous recurrent epileptic seizures. Furthermore, as in humans, status epilepticus is one of the more common neurological emergencies in dogs with epilepsy. In both species, epilepsy is not a single disease but a group of disorders characterized by a broad array of clinical signs, age of onset, and underlying causes. Brain imaging suggests that the limbic system, including the hippocampus and cingulate gyrus, is often affected in canine epilepsy, which could explain the high incidence of comorbid behavioral problems such as anxiety and cognitive alterations. Resistance to antiseizure medications is a significant problem in both canine and human epilepsy, so dogs can be used to study mechanisms of drug resistance and develop novel therapeutic strategies to benefit both species. Importantly, dogs are large enough to accommodate intracranial EEG and responsive neurostimulation devices designed for humans. Studies in epileptic dogs with such devices have reported ictal and interictal events that are remarkably similar to those occurring in human epilepsy. Continuous (24/7) EEG recordings in a select group of epileptic dogs for >1 year have provided a rich dataset of unprecedented length for studying seizure periodicities and developing new methods for seizure forecasting. The data presented in this review substantiate that canine epilepsy is an excellent translational model for several facets of epilepsy research. Furthermore, several techniques of inducing seizures in laboratory dogs are discussed as related to therapeutic advances. Importantly, the development of vagus nerve stimulation as a novel therapy for drug-resistant epilepsy in people was based on a series of studies in dogs with induced seizures. Dogs with naturally occurring or induced seizures provide excellent large-animal models to bridge the translational gap between rodents and humans in the development of novel therapies. Furthermore, because the dog is not only a preclinical species for human medicine but also a potential patient and pet, research on this species serves both veterinary and human medicine.

A retrospective case series of clinical signs in 28 Beagles with Lafora disease

BACKGROUND

Clinical signs and their progression in Beagles with Lafora disease are poorly described.

OBJECTIVES

To describe clinical signs in Beagles with Lafora disease.

ANIMALS

Twenty-eight Beagles with Lafora disease confirmed by genetic testing or histopathology.

METHODS

Retrospective multicenter case series. Data regarding signalment, clinical signs, diagnostic tests and treatment were retrieved from hospital data files. A questionnaire was sent to owners asking about neurological deficits, changes in cognitive functions, behavioral changes, response to treatment and survival time.

RESULTS

Onset of clinical signs was 8.3 years (mean; range, 6.3-13.3). All dogs had myoclonic episodes as an initial clinical sign with tonic-clonic seizures in n = 11/28 (39%) and n = 12/28 (43%) later developing tonic-clonic seizures. Deficits of coordination (n = 21/25; 84%), impaired vision (n = 15/26; 58%), and impaired hearing (n = 13/26; 50%) developed later. Mental decline was observed as loss of house training (urination; n = 8/25; 32%), difficulties performing learned tasks (n = 9/25; 36%), and difficulties learning new tasks (n = 7/23; 30%). Common behavioral changes were: increased photosensitivity (n = 20/26; 77%), staring into space (n = 16/25; 64%), reduced stress resistance (n = 15/26; 58%), increased noise sensitivity (n = 14/26; 54%), and separation anxiety (n = 11/25; 44%). Twenty-one dogs were alive (median age 11.9 years; range, 9.8-18.6), and 7 dogs were dead (mean age 12.1 years; SD: 1.3; range, 10.5-12.6) at time of writing.

CONCLUSIONS AND CLINICAL IMPORTANCE

Lafora disease in Beagles causes significant behavioral changes, and mental decline as well as neurological deficits in addition to myoclonic episodes and generalized tonic-clonic seizures. Nevertheless, a relatively normal life span can be expected.