Age-dependent neurological phenotypes in a mouse model of PRRT2-related diseases.

Paroxysmal kinesigenic dyskinesia is an episodic movement disorder caused by dominant mutations in the proline-rich transmembrane protein PRRT2, with onset in childhood and typically with improvement or resolution by middle age. Mutations in the same gene may also cause benign infantile seizures, which begin in the first year of life and typically remit by the age of 2 years. Many details of PRRT2 function at the synapse, and the effects of mutations on neuronal excitability in the pathophysiology of epilepsy and dyskinesia, have emerged through the work of several groups over the last decade. However, the age dependence of the phenotypes has not been explored in detail in transgenic models. Here, we report our findings in heterozygous and homozygous Prrt2 knockout mice that recapitulate the age dependence of dyskinesia seen in the human disease. We show that Prrt2 deletion reduces the levels of synaptic proteins in a dose-dependent manner that is most pronounced at postnatal day 5 (P5), attenuates at P60, and disappears by P180. In a test for foot slippage while crossing a balance beam, transient loss of coordination was most pronounced at P60 and less prominent at age extremes. Slower traverse time was noted in homozygous knockout mice only, consistent with the ataxia seen in rare individuals with biallelic loss of function mutations in Prrt2. We thus identify three age-dependent phenotypic windows in the mouse model, which recapitulate the pattern seen in humans with PRRT2-related diseases.

[Epilepsy or functional neurological disorder. Diagnostic strategies]. / Epilepsia o trastorno neurológico funcional. Estrategias para el diagnóstico.

A seizure is the manifestation of symptoms or signs produced by excessive or synchronous neuronal activity in the brain. It usually presents as brief, self-limited episodes of involuntary movements that can affect a part or the entire body and that are sometimes accompanied by loss of consciousness and sphincter control. Epilepsy may be considered after a single unprovoked seizure in a patient with a high risk of recurrence. Paroxysmal non-epileptic disorders are defined as episodes of sudden onset and short duration that imitate an epileptic seizure, caused by a brain dysfunction of diverse origin that, unlike epilepsy, is not due to excessive neuronal discharge. Its incidence is much higher than epilepsy and it can appear at any age. It is important for diagnosis to analyze the triggering factors, the details of each episode, physical examination and only proceed to basic complementary tests such as video-electroencephalogram in case of doubt or for diagnostic confirmation. There is a tendency to overdiagnose epilepsy and excessive use of anticonvulsant drugs. Those that can most frequently be confused are syncope, "daydreams" and pseudoseizures.

Una convulsión es la manifestación de signos o síntomas producidos por una actividad neuronal excesiva o sincrónica en el cerebro. Suele presentarse como episodios breves, autolimitados, de movimientos involuntarios que pueden afectar a una parte del cuerpo o su totalidad y que, en ocasiones, se acompañan de pérdida de la conciencia y control de esfínteres. Puede considerarse epilepsia una sola crisis no provocada en un paciente con un elevado riesgo de recurrencia. Los trastornos paroxísticos no epilépticos se definen como episodios de aparición brusca y de breve duración que imitan a una crisis epiléptica, originados por una disfunción cerebral de origen diverso que a diferencia de la epilepsia no obedecen a una descarga neuronal excesiva. Su incidencia es mucho más elevada que la epilepsia y pueden aparecer a cualquier edad. Es importante para el diagnóstico analizar los factores desencadenantes, los pormenores de cada episodio, examen físico y solamente proceder a los exámenes complementarios básicos como video-electroencefalograma en caso de duda o para confirmación diagnóstica. Existe la tendencia a sobrediagnosticar epilepsia y al uso excesivo de fármacos anticonvulsivos. Los que con mayor frecuencia se pueden confundir son los síncopes, ensoñaciones y las pseudocrisis.

Exploring epileptic phenotypes in PRRT2-related disorders: A report of two cases and literature appraisal.

BACKGROUND: The proline-rich transmembrane protein 2 (PRRT2) is a synaptic protein involved in neurotransmitter vesicle release. PRRT2 protein is highly expressed in the cerebellum, cerebral cortex, basal ganglia, and hippocampus. Variants in PRRT2 have been identified as a cause of several neurological disorders, including epilepsy, movement disorders, and headache. METHODS: We report two families carrying two distinct PRRT2 mutations showing childhood onset of movement disorders, headache, and epilepsy. Demographics, clinical, EEG, neuroimaging, and genetic sequencing study data were collected. A systematic review of the literature was also performed to dissect the most frequently reported PRRT2-associated epileptic phenotypes. RESULTS: two variants in PRRT2 gene (NM_145239.3:c718C>T, p.Arg240Ter; c.649dupC, p.Arg217Profs*8) were identified. The two variants altered the same extracellular domain of PRRT2. The de novo PRRT2 mutation (c718C>T, p.Arg240Ter) was related to multi-drug-resistant epilepsy. According to the literature, homozygous, biallelic variants and 16p11.2 deletions lead to PRRT2 haploinsufficiency and a more severe phenotype. CONCLUSIONS: PRRT2 mutations can be associated with several epileptic phenotypes ranging from benign ASM-responsive form to more severe epileptic encephalopathies. Identifying PRRT2 variants in epilepsy patients may help achieve more personalized treatment approaches. However, phenotype-genotype correlations remain a challenge.

Rare Earth Element Content in Hair Samples of Children Living in the Vicinity of the Kola Peninsula Mining Site and Nervous System Diseases.

The aim of this study is to assess the rare earth element (REE) content in hair samples of children living in Lovozero village, near an REE mining site, and the possible effects of REEs on the prevalence of nervous system diseases in Lovozersky District (Murmansk region, Kola Peninsula). Fifty-three school-age children were recruited for the analysis of REE content in hair samples. REE (Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) content was estimated by means of inductively coupled plasma mass spectrometry (ICP-MS). The analysis of REE content in the hair of children living in Russia, Kazakhstan, and China indicated REE intake from the environment. The possible contribution of REEs to nervous system disorders is supported by the link between the REE content in hair samples of children living near REE mining areas (China) and the manifestation of cognitive disorders in these children. It is also found that the prevalence of nervous system diseases in children aged 15-17 years is higher in Lovozersky District compared to the other districts of the Murmansk region. In this paper, the possible contribution of REEs to the prevalence of episodic paroxysmal disorders (G40-G47), cerebral palsy (G80-G83), and epilepsy and status epilepticus (G40-G41) is discussed.

Head atonic attacks: a new type of benign non-epileptic attack in infancy strongly mimicking epilepsy.

Non-epileptic attacks (NEAs) are a heterogeneous group of clinical entities which often complicate the differential diagnosis of epilepsy. NEAs usually have a benign course and are limited to a specific period of life. If motor manifestations are strongly suggestive of an epileptic phenomenon, the risk of misdiagnosis is greater. Here, we describe a novel NEA with infantile onset, characterised by repeated head drops, mimicking epileptic negative myoclonus of the neck. The frequency of the episodes was very high, at hundreds or thousands per day. The episodes appeared in the second semester of the first year of life and spontaneously disappeared within a few months. [Published with video sequences].

Non-Motor Symptoms and Quality of Life in Patients with PRRT2-Related Paroxysmal Kinesigenic Dyskinesia.

Background: Monoallelic pathogenic variants of PRRT2 often result in paroxysmal kinesigenic dyskinesia (PKD). Little is known about health-related quality of life (HrQoL), non-motor manifestations, self-esteem, and stigma in patients with PKD. Objectives: We investigated non-motor symptoms and how they related to HrQoL in a genetically homogeneous group of PRRT2-PKD patients. We paid special attention to perceived stigmatization and self-esteem. Methods: We prospectively enrolled 21 consecutive PKD patients with a pathogenic variant of PRRT2, and 21 healthy controls matched for age and sex. They were evaluated with dedicated standardized tests for non-motor symptoms, HrQoL, anxiety, depression, stigma, self-esteem, sleep, fatigue, pain, and psychological well-being. Results: Patients reported an alteration of the physical aspects of HrQoL, regardless of the presence of residual paroxysmal episodes. Non-motor manifestations were frequent, and were an important determinant of the alteration of HrQoL. In addition, patients perceived a higher level of stigmatization which positively correlated with a delay in diagnosis (ρ = 0.615, P = 0.003) and the fear of being judged (ρ = 0.452, P = 0.04), but not with the presence of paroxysmal episodes (ρ = 0.203, P = 0.379). Conclusions: Our findings have important implications for care givers concerning patient management and medical education about paroxysmal dyskinesia. PRRT2-PKD patients should be screened for non-motor disorders in routine care. A long history of misdiagnosis may play a role in the high level of perceived stigmatization. Improving knowledge about diagnostic clues suggestive of PKD is mandatory.

Clinical phenotypes of infantile onset CACNA1A-related disorder.

BACKGROUND: CACNA1A-related disorders present with persistent progressive and non-progressive cerebellar ataxia and paroxysmal events: epileptic seizures and non-epileptic attacks. These phenotypes overlap and co-exist in the majority of patients. OBJECTIVE: To describe phenotypes in infantile onset CACNA1A-related disorder and to explore intra-familial variations and genotype-phenotype correlations. MATERIAL AND METHODS: This study was a multicenter international collaboration. A retrospective chart review of CACNA1A patients was performed. Clinical, radiological, and genetic data were collected and analyzed in 47 patients with infantile-onset disorder. RESULTS: Paroxysmal non-epileptic events (PNEE) were observed in 68% of infants, with paroxysmal tonic upward gaze (PTU) noticed in 47% of infants. Congenital cerebellar ataxia (CCA) was diagnosed in 51% of patients including four patients with developmental delay and only one neurological sign. PNEEs were found in 63% of patients at follow-up, with episodic ataxia (EA) in 40% of the sample. Cerebellar ataxia was found in 58% of the patients at follow-up. Four patients had epilepsy in infancy and nine in childhood. Seven infants had febrile convulsions, three of which developed epilepsy later; all three patients had CCA. Cognitive difficulties were demonstrated in 70% of the children. Cerebellar atrophy was found in only one infant but was depicted in 64% of MRIs after age two. CONCLUSIONS: Nearly all of the infants had CCA, PNEE or both. Cognitive difficulties were frequent and appeared to be associated with CCA. Epilepsy was more frequent after age two. Febrile convulsions in association with CCA may indicate risk of epilepsy in later childhood. Brain MRI was normal in infancy. There were no genotype-phenotype correlations found.

PRRT2 modulates presynaptic Ca2+ influx by interacting with P/Q-type channels.

Loss-of-function mutations in proline-rich transmembrane protein-2 (PRRT2) cause paroxysmal disorders associated with defective Ca2+ dependence of glutamatergic transmission. We find that either acute or constitutive PRRT2 deletion induces a significant decrease in the amplitude of evoked excitatory postsynaptic currents (eEPSCs) that is insensitive to extracellular Ca2+ and associated with a reduced contribution of P/Q-type Ca2+ channels to the EPSC amplitude. This synaptic phenotype parallels a decrease in somatic P/Q-type Ca2+ currents due to a decreased membrane targeting of the channel with unchanged total expression levels. Co-immunoprecipitation, pull-down assays, and proteomics reveal a specific and direct interaction of PRRT2 with P/Q-type Ca2+ channels. At presynaptic terminals lacking PRRT2, P/Q-type Ca2+ channels reduce their clustering at the active zone, with a corresponding decrease in the P/Q-dependent presynaptic Ca2+ signal. The data highlight the central role of PRRT2 in ensuring the physiological Ca2+ sensitivity of the release machinery at glutamatergic synapses.

Paroxysmal eyelid movements in patients with visual-sensitive reflex seizures.

AIM: Paroxysmal eyelid movements (PEM) are non-epileptic episodes characterized by eyelid closure, upturning of the eyes, and rapid eyelid flutter. The aim of this study was to report clinical and EEG data of patients with PEM and its relationship with visual sensitivity. METHODS: We studied 26 patients with epilepsy (12 males and 14 females; mean age: 14.0±6.9 years) who presented PEM. The epilepsy was idiopathic generalized (eight cases), idiopathic focal (six cases), symptomatic focal (five cases), and reflex epilepsy (seven cases). PEM and blinking were analysed by video-EEG recordings at rest and during intermittent photic stimulation, pattern stimulation, and TV watching. Blink rate was evaluated during three different conditions: at rest, during a TV-viewing period, and at the occurrence of PEM. Analysis of variance (ANOVA) was used for statistical comparisons. RESULTS: Repeated episodes of PEM were recorded in all patients. The frequency of PEM ranged from 8 to 12.5 Hz (average: 9.6±1.5). PEM were accompanied by a significant increase in blinking compared to the rest condition and TV watching (blink rate: 56.5±21.1 vs 25.0±16.2 vs 11.3±11.8, respectively; p<0.0001). Photoparoxysmal EEG responses (measured as sensitivity to photic stimulation) were found in 25 cases, associated with pattern sensitivity in 22; only one patient was sensitive to pattern but not photic stimulation. Visually-induced seizures were recorded in 20 cases, triggered by both stimuli (photic and pattern stimulation) in 11 patients; seizures were triggered by pattern stimulation (but not photic stimulation) in five, photic stimulation (but not pattern stimulation) in three, and TV watching (but not photic or pattern stimulation) in one. Epileptic eyelid myoclonia was noted in 17 patients. CONCLUSION: The coexistence of PEM, photoparoxysmal EEG responses, increased blinking, and epileptic eyelid myoclonia suggests an underlying dysfunction involving cortical-subcortical neural networks, according to the recent concept of system epilepsies. [Published with video sequences].

Nonepileptic paroxysmal disorders in childhood / 소아과

Epilepsy is the most common paroxysmal disorders seen in the childhood. But other nonepileptic paroxysmal events are confused with epileptic seizures or have unusual clinical features. Nonepileptic paroxysmal disorders tend to recur episodically. So differential diagnosis between epileptic and nonepileptic disorders in fundamental not only to allow correct management of patients and but also avoid of unnecessary antiepileptic medications. To accurate diagnosis of nonepileptic paroxysmal disorders, the patients' age and accurate description of the events are need.