Epilepsy or paroxysmal kinesigenic choreoathetosis?

Phenotypic characterisation of paroxysmal dyskinesia in Sphynx cats

OBJECTIVES

The aim of this study was to identify the phenotypic features of a paroxysmal dyskinesia observed in Sphynx cats.

METHODS

The owners of affected Sphynx cats were invited to provide video footage of abnormal episodes for review. Those that demonstrated episodes consistent with paroxysmal dyskinesia were then invited to complete an online questionnaire designed to allow further characterisation.

RESULTS

Ten Sphynx cats were included in the study. All affected cats were <4 years of age at the onset of the episodes (range 0.5-4.0). The episodes had a duration of <5 mins in 9/10 cats (range 0.5-10), while episode frequency was variable between and within individual cats. The episodes were characterised by impaired ambulation due to muscle hypertonicity, most commonly affecting the hips and pelvic limbs (9/10) and shoulders and thoracic limbs (8/10). The head and neck (6/10), tail (5/10), and back and abdomen (3/10) were also involved in some cats. Sudden movement, excitement and stress were identified as possible triggers for the episodes in three cats. Therapeutic intervention was not attempted in 7/10 cases, although two cats were reported to become free of the episodes while receiving acetazolamide. The two cats that were followed beyond 2 years from onset entered spontaneous remission. None of the owners believed that the abnormal episodes had affected the quality of life of their cat.

CONCLUSIONS AND RELEVANCE

The phenotype of paroxysmal dyskinesia in Sphynx cats presented in this study appears to share similarities with paroxysmal kinesigenic dyskinesia described in human classification systems. Some cats appear to achieve episode freedom spontaneously. Subsequent research should focus on evaluating response to treatment and determining an underlying genetic cause.

Epileptic seizures triggered by eating in dogs

Background

Seizures triggered by eating (STE) behavior are very rare in humans and have not been documented previously in dogs.

Objectives

To document the occurrence of STE in dogs and describe their clinical features.

Animals

Ten client‐owned dogs with STE diagnosed at 5 European referral centers.

Methods

A call for suspected cases of STE was made online. This call was followed by a retrospective review of medical records, combined with a questionnaire to be completed by both the owner and the board‐certified neurologist who made the diagnosis. Cases were included if >50% of the seizures that occurred were related to eating and if a minimum diagnostic evaluation for seizures had been performed.

Results

Four cases only had STE and 6 cases had both STE and spontaneous seizures. Four of the dogs were retrievers. The most common seizure type was focal epileptic seizures evolving to become generalized. Nine dogs were diagnosed with idiopathic epilepsy. One dog had a presumptive diagnosis of glioma involving the margins of the parietal, temporal, and frontal cortex (the perisylvian region), an area known to have a key role in eating‐associated epilepsy in people. Treatment strategies included a combination of pharmacological management and eating habit changes.

Conclusions and Clinical Importance

We have identified a form of reflex epilepsy in dogs, with STE behavior. Further studies are warranted to improve the characterization and management of STE.

Novel Locus for Paroxysmal Kinesigenic Dyskinesia Mapped to Chromosome 3q28-29

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by recurrent and brief attacks of dystonia or chorea precipitated by sudden movements. It can be sporadic or familial. Proline-Rich Transmembrane Protein 2 (PRRT2) has been shown to be a common causative gene of PKD. However, less than 50% of patients with primary PKD harbor mutations in PRRT2. The aim of this study is to use eight families with PKD to identify the pathogenic PRRT2 mutations, or possible novel genetic cause of PKD phenotypes. After extensive clinical investigation, direct sequencing and mutation analysis of PRRT2 were performed on patients from eight PKD families. A genome-wide STR and SNP based linkage analysis was performed in one large family that is negative for pathogenic PRRT2 mutations. Using additional polymorphic markers, we identified a novel gene locus on chromosome 3q in this PRRT2-mutation-negative PKD family. The LOD score for the region between markers D3S1314 and D3S1256 is 3.02 and we proposed to designate this locus as Episodic Kinesigenic Dyskinesia (EKD3). Further studies are needed to identify the causative gene within this locus.

Benign infantile seizures and paroxysmal dyskinesia caused by an SCN8A mutation

OBJECTIVE

Benign familial infantile seizures (BFIS), paroxysmal kinesigenic dyskinesia (PKD), and their combination-known as infantile convulsions and paroxysmal choreoathetosis (ICCA)-are related autosomal dominant diseases. PRRT2 (proline-rich transmembrane protein 2 gene) has been identified as the major gene in all 3 conditions, found to be mutated in 80 to 90% of familial and 30 to 35% of sporadic cases.

METHODS

We searched for the genetic defect in PRRT2-negative, unrelated families with BFIS or ICCA using whole exome or targeted gene panel sequencing, and performed a detailed cliniconeurophysiological workup.

RESULTS

In 3 families with a total of 16 affected members, we identified the same, cosegregating heterozygous missense mutation (c.4447G>A; p.E1483K) in SCN8A, encoding a voltage-gated sodium channel. A founder effect was excluded by linkage analysis. All individuals except 1 had normal cognitive and motor milestones, neuroimaging, and interictal neurological status. Fifteen affected members presented with afebrile focal or generalized tonic-clonic seizures during the first to second year of life; 5 of them experienced single unprovoked seizures later on. One patient had seizures only at school age. All patients stayed otherwise seizure-free, most without medication. Interictal electroencephalogram (EEG) was normal in all cases but 2. Five of 16 patients developed additional brief paroxysmal episodes in puberty, either dystonic/dyskinetic or "shivering" attacks, triggered by stretching, motor initiation, or emotional stimuli. In 1 case, we recorded typical PKD spells by video-EEG-polygraphy, documenting a cortical involvement.

INTERPRETATION

Our study establishes SCN8A as a novel gene in which a recurrent mutation causes BFIS/ICCA, expanding the clinical-genetic spectrum of combined epileptic and dyskinetic syndromes.

Phenotypic characterisation of canine epileptoid cramping syndrome in the Border terrier

OBJECTIVES

To characterise the phenotype of Border terriers suspected to be affected by canine epileptoid cramping syndrome and to identify possible contributing factors.

METHODS

Owners of Border terriers with suspected canine epileptoid cramping syndrome were invited to complete an online questionnaire. The results of these responses were collated and analysed.

RESULTS

Twenty-nine Border terriers were included. Most affected dogs had their first episode before 3 years of age (range: 0·2 to 7·0 years). The majority of episodes lasted between 2 and 30 minutes (range: 0·5 to 150 minutes). The most frequent observations during the episodes were difficulty in walking (27 of 29), mild tremor (21 of 29) and dystonia (22 of 29). Episodes most frequently affected all four limbs (25 of 29) and the head and neck (21 of 29). Borborygmi were reported during episodes in 11 of 29 dogs. Episodes of vomiting and diarrhoea occurred in 14 of 29, with 50% of these being immediately before or after episodes of canine epileptoid cramping syndrome (7 of 14). Most owners (26 of 29) had changed their dog's diet, with approximately 50% (14 of 26) reporting a subsequent reduction in the frequency of episodes.

CLINICAL SIGNIFICANCE

This study demonstrates similarities in the phenotype of canine epileptoid cramping syndrome to paroxysmal dystonic choreoathetosis, a paroxysmal dyskinesia reported in humans. This disorder appears to be associated with gastrointestinal signs in some dogs and appears at least partially responsive to dietary adjustments.

Paroxysmal kinesigenic dyskinesia: cortical or non-cortical origin

Paroxysmal kinesigenic dyskinesia (PKD) is characterized by involuntary dystonia and/or chorea triggered by a sudden movement. Cases are usually familial with an autosomal dominant inheritance. Hypotheses regarding the pathogenesis of PKD focus on the controversy whether PKD has a cortical or non-cortical origin. A combined familial trait of PKD and benign familial infantile seizures has been reported as the infantile convulsions and paroxysmal choreoathetosis (ICCA) syndrome. Here, we report a family diagnosed with ICCA syndrome with an Arg217STOP mutation. The index patient showed interictal EEG focal changes compatible with paroxysmal dystonic movements of his contralateral leg. This might support cortical involvement in PKD.

Anticonvulsant responsive, episodic movement disorder in a German shorthaired pointer

An episodic movement disorder is described in a young German shorthaired pointer. Movement disorders are rare, but well-described, neurological conditions in human beings. An attempt is made to classify this disorder using current human guidelines. Unlike previously described movement disorders in dogs, this case responded very well to two commonly used anticonvulsant therapies, suggesting that trial therapy with these drugs is worthwhile in similar cases.

Paroxysmal kinesigenic choreoathetosis: from first discovery in 1892 to genetic linkage with benign familial infantile convulsions

Paroxysmal kinesigenic choreoathetosis (PKC) is presently clearly designated as a familial movement disorder with autosomal dominant inheritance. We identified a family of PKC, in which 6 out of 23 members were affected, and 4 of the affected members had a history of infantile convulsions. Thus, this family was also considered as a case of infantile convulsions with paroxysmal choreoathetosis (ICCA). Video-EEG monitoring of two affected members suggested that PKC is less likely to be a form of reflex epilepsy, despite the existence of a history of infantile convulsions. Linkage analysis on eight Japanese families, including this family, defined the locus of PKC within the pericentromeric region of chromosome 16. ICCA and a form of autosomal dominant benign familial infantile convulsions (BFIC) were both mapped to the same or nearby region for PKC on chromosome 16. Additionally and quite unexpectedly, the locus of wet/dry ear wax (cerumen) was found to be located in the same region. Lastly, it was pointed out that the priority of the first discovery of PKC in the world should go to a Japanese psychiatrist, Shuzo Kure (1865-1932), who published the first detailed and almost complete description of a male patient with PKC in a Japanese medical journal in 1892.

Kinesigenic attacks with ictal electroencephalographic abnormalities

We report on a 14-year 5-month-old male who had attacks similar to those of paroxysmal kinesigenic choreoathetosis. The attacks were elicited exclusively by sudden movements. On several occasions, these attacks were immediately followed by loss of consciousness or a seizure. Ictal electroencephalograms of his attacks without loss of consciousness or a seizure indicated 1.5-3.0 Hz activity in the left hemisphere. A small dosage of carbamazepine was remarkably effective in stopping the attacks. This case demonstrates that a thorough ictal electroencephalographic examination is indispensable for clarifying the pathophysiology of kinesigenic attacks. The relationship between paroxysmal kinesigenic choreoathetosis and supplementary motor area seizures is also discussed.

Carbamazepine, clonazepam and focal reflex proprioceptive seizures

We studied a 34-year-old man with focal tonic-clonic seizures sometimes elicited by some active postures of the right hand and evolving at times to secondary generalization. Treatment with carbamazepine (CBZ) in combination with parenteral diazepam induced both a dramatic increase of focal reflex proprioceptive seizures and choreoathetoid dyskinesias in the affected hand. CBZ was withdrawn and clonazepam (CZP) given 2 mg daily, with complete relief of seizures and choreoathetoid dyskinesias. CZP had a suppressive effect on seizures for over 15 years, without development of tolerance.

Paroxysmal dyskinesias in the lethargic mouse mutant

Lethargic mutant mice carry a mutation in the CCHB4 gene, which encodes the beta4 subunit of voltage-regulated calcium channels. These mutants have been shown to display a complex neurobehavioral phenotype that includes EEG discharges suggestive of absence epilepsy, chronic ataxia, and hypoactivity. The current studies demonstrate a fourth element of their phenotype, consisting of transient attacks of severe dyskinetic motor behavior. These attacks can be triggered by specific environmental and chemical influences, particularly those that stimulate locomotor activity. Behavioral and EEG analyses indicate that the attacks do not reflect motor epilepsy, but instead resemble a paroxysmal dyskinesia. The lethargic mutants provide additional evidence that calcium channelopathies can produce paroxysmal dyskinesias and provide a novel model for studying this unusual movement disorder.

Genetic and clinical heterogeneity in paroxysmal kinesigenic dyskinesia: evidence for a third EKD gene

Paroxysmal kinesigenic dyskinesia (PKD) is characterised by paroxysms of choreic, dystonic, ballistic, or athetoid movements. The attacks typically last seconds to minutes in duration and are induced by sudden voluntary movement. PKD loci have been identified on chromosome 16. We present the clinical and genetic details of two British and an Indian family with PKD. Linkage to the PKD loci on chromosome 16 has been excluded in one of these families, providing evidence for a third loci for PKD. Detailed clinical descriptions highlight the presence of both adolescent and infantile seizures in some of the PKD families. This study attempts to clarify the relationship of adolescent and infantile seizures to PKD and provides evidence that PKD is both genetically and clinically heterogeneous.

Gait epilepsy. A case report of gait-induced seizures

Reflex epilepsy includes a group of epileptic syndromes in which seizures are induced by a stimulus, either simple (visual, somatosensory, olfactory, auditory) or more complex (e.g., eating, thinking, reading). We document a case of reflex epilepsy in which focal seizures are triggered exclusively by gait. The patient is a young boy whose walking was impaired by abnormal motor phenomena on the left side. These phenomena were elicited by gait and were accompanied by a distinctive ictal pattern with centro-temporal discharges. After comparing this patient with others reported in the literature, we determined that he has an unusual type of reflex epilepsy for which we coined the term "gait epilepsy." This disorder must be considered when physicians are making a differential diagnosis in patients who have symptoms that suggest paroxysmal kinesigenic dystonia (PKD) or selective epileptic gait disorder.

Familial paroxysmal exercise-induced dyskinesia, epilepsy, and mental retardation in a family with autosomal dominant inheritance

Only few sporadic and familial cases of paroxysmal exercise-induced dyskinesia (PED) have been described in literature. PED associated with familial epilepsy has been rarely reported. We describe a family in which six members in different generations were affected by a long-lasting PED, with childhood onset in five cases. Fasting and stress were also precipitating factors. All the subjects, moreover, showed epileptic seizures during childhood and adolescence. In addition, in all cases a condition of mild mental retardation was also documented, associated in some cases, with irritable and impulsive behaviour. Clinical, neurophysiological, neuroimaging and neuropsychological findings were reported. The homogeneous recurrence of this particular clinical picture in members of three generations emphasised a common genetic basis. In our patients, PED is transmitted as an autosomal dominant trait, with age-dependent penetrance, without evidence of genetic anticipation. The neurophysiological findings suggest a condition of hyperexcitability in the muscular and brain membrane, due to a ion channels disorder.

Dyskinesia in an adult bichon frise

Dyskinesias are disorders of the central nervous system that result in involuntary movements in a fully conscious individual. This report describes a disorder in a five-year-old male neutered bichon frise characterised by episodic involuntary skeletal muscle activity with normal levels of consciousness that bears some similarity to the previously described movement disorder in boxer puppies and to the human condition descriptively referred to as paroxysmal dystonic choreoathetosis. The disorder was differentiated from partial motor seizure activity by the character of the episodes, absence of identifiable preceding aura, absence of autonomic signs and the fact that multiple limbs were affected in a varying pattern without generalisation and loss of consciousness. Movement disorders are a well documented group of disorders in human neurology, but only rarely described in the veterinary literature. The purpose of this report is to contribute to an increased awareness of movement disorders within veterinary practice.

A 16-year-old with episodic hemisdystonia

The paroxysmal dyskinesias are a subset of the hyperkinetic movement disorders characterized by their episodic nature. Classification based on precipitating factors is helpful in considering treatment and prognosis. The clinical similarities with partial seizures are discussed. An approach to differential diagnosis, diagnostic evaluation, and treatment options are presented.

Familial infantile convulsions and paroxysmal choreoathetosis: a new neurological syndrome linked to the pericentromeric region of human chromosome 16

Benign infantile familial convulsions is an autosomal dominant disorder characterized by nonfebrile seizures, with the first attack occurring at age 3-12 mo. It is one of the rare forms of epilepsy that are inherited as monogenic Mendelian traits, thus providing a powerful tool for mapping genes involved in epileptic syndromes. Paroxysmal choreoathetosis is an involuntary-movement disorder characterized by attacks that occur spontaneously or are induced by a variety of stimuli. Classification is still elusive, and the epileptic nature of this movement disorder has long been discussed and remains controversial. We have studied four families from northwestern France in which benign infantile convulsions was inherited as an autosomal dominant trait together with variably expressed paroxysmal choreoathetosis. The human genome was screened with microsatellite markers regularly spaced, and strong evidence of linkage for the disease gene was obtained in the pericentromeric region of chromosome 16, with a maximum two-point LOD score, for D16S3133, of 6.76 at a recombination fraction of 0. Critical recombinants narrowed the region of interest to a 10-cM interval around the centromere. Our study provides the first genetic evidence for a common basis of convulsive and choreoathetotic disorders and will help in the understanding and classification of paroxysmal neurological syndromes.