Clinical management and diagnosis of CLN2 disease: consensus of the Brazilian experts group.

Neuronal ceroid lipofuscinosis type 2 (CLN2) is a rare neurodegenerative genetic disease that affects children in early life. Its classic form is rapidly progressive, leading to death within the first 10 years. The urge for earlier diagnosis increases with the availability of enzyme replacement therapy. A panel of nine Brazilian child neurologists combined their expertise in CLN2 with evidence from the medical literature to establish a consensus to manage this disease in Brazil. They voted 92 questions including diagnosis, clinical manifestations, and treatment of the disease, considering the access to healthcare in this country. Clinicians should suspect CLN2 disease in any child, from 2 to 4 years old, with language delay and epilepsy. Even though the classic form is the most prevalent, atypical cases with different phenotypes can be found. Electroencephalogram, magnetic resonance imaging, molecular and biochemical testing are the main tools to investigate and confirm the diagnosis. However, we have limited access to molecular testing in Brazil, and rely on the support from the pharmaceutical industry. The management of CLN2 should involve a multidisciplinary team and focus on the quality of life of patients and on family support. Enzyme replacement therapy with Cerliponase α is an innovative treatment approved in Brazil since 2018; it delays functional decline and provides quality of life. Given the difficulties for the diagnosis and treatment of rare diseases in our public health system, the early diagnosis of CLN2 needs improvement as enzyme replacement therapy is available and modifies the prognosis of patients.

Lipofuscinose ceróide neuronal (CLN2) é uma doença genética neurodegenerativa rara que afeta crianças nos primeiros anos de vida. A sua forma clássica é rapidamente progressiva, levando à morte nos primeiros 10 anos. A necessidade de um diagnóstico precoce aumenta com a disponibilidade do tratamento de terapia enzimática. Um painel de nove neurologistas infantis brasileiros combinou sua experiência em CLN2 com evidências da literatura médica para estabelecer um consenso no manejo desta doença no Brasil. Eles votaram 92 questões abordando diagnóstico, manifestações clínicas e tratamento, considerando o acesso à saúde no Brasil. Deve-se suspeitar de CLN2 em qualquer criança de 2 a 4 anos de idade que apresente atraso de linguagem e epilepsia. Apesar da forma clássica ser a mais prevalente, podem ser encontrados casos atípicos com diferentes fenótipos. Eletroencefalograma, ressonância magnética, testes moleculares e bioquímicos são as principais ferramentas para investigar e confirmar o diagnóstico. No entanto, o acesso aos testes moleculares é limitado no Brasil, necessitando contar com o apoio da indústria farmacêutica. O manejo da CLN2 deve envolver uma equipe multidisciplinar e focar na qualidade de vida dos pacientes e no apoio familiar. A terapia de reposição enzimática com Cerliponase alfa é um tratamento inovador aprovado no Brasil desde 2018; ele retarda o declínio funcional e proporciona qualidade de vida. Diante das dificuldades para o diagnóstico e tratamento de doenças raras em nosso sistema público de saúde, o diagnóstico precoce de CLN2 precisa de melhorias pois a terapia de reposição enzimática está disponível e modifica o prognóstico dos pacientes.

Heterozygosity for neuronal ceroid lipofuscinosis predisposes to bipolar disorder.

OBJECTIVE: Bipolar disorder is a heritable chronic mental disorder that causes psychosocial impairment through depressive/manic episodes. Familial transmission of bipolar disorder does not follow simple Mendelian patterns of inheritance. The aim of this study was to describe a large family with 12 members affected by bipolar disorder. Whole-exome sequencing was performed for eight members, three of whom were diagnosed with bipolar disorder, and another reported as "borderline." METHODS: Whole-exome sequencing data allowed us to select variants that the affected members had in common, including and excluding the "borderline" individual with moderate anxiety and obsessive-compulsive traits. RESULTS: The results favored designating certain genes as predispositional to bipolar disorder: a heterozygous missense variant in CLN6 resulted in a "borderline" phenotype that, if combined with a heterozygous missense variant in ZNF92, is responsible for the more severe bipolar disorder phenotype. Both rare missense changes are predicted to disrupt protein function. CONCLUSIONS: Loss of both alleles in CLN6 causes neuronal ceroid lipofuscinosis, a severe progressive childhood neurological disorder. Our results indicate that heterozygous CLN6 carriers, previously reported as healthy, may be susceptible to bipolar disorder later in life if associated with additional variants in ZNF92.

Neuronal Ceroid Lipofuscinosis Type 6 (CLN6) clinical findings and molecular diagnosis: Costa Rica's experience.

BACKGROUND: Commonly known as Batten disease, the neuronal ceroid lipofuscinoses (NCLs) are a genetically heterogeneous group of rare pediatric lysosomal storage disorders characterized by the intracellular accumulation of autofluorescent material (known as lipofuscin), progressive neurodegeneration, and neurological symptoms. In 2002, a disease-causing NCL mutation in the CLN6 gene was identified (c.214G > T) in the Costa Rican population, but the frequency of this mutation among local Batten disease patients remains incompletely characterized, as do clinical and demographic attributes for this rare patient population. OBJECTIVE: To describe the main sociodemographic and clinical characteristics of patients with a clinical diagnosis for Batten Disease treated at the National Children's Hospital in Costa Rica and to characterize via molecular testing their causative mutations. METHODS: DNA extracted from buccal swabs was used for CLN6 gene sequencing. Participants' sociodemographic and clinical characteristics were also obtained from their medical records. RESULTS: Nine patients with a clinical diagnosis of Batten disease were identified. Genetic sequencing determined the presence of the previously described Costa Rican homozygous mutation in 8 of 9 cases. One patient did not have mutations in the CLN6 gene. In all cases where the Costa Rican CLN6 mutation was present, it was accompanied by a substitution in intron 2. Patients were born in 4 of the 7 Costa Rican provinces, with an average onset of symptoms close to 4 years of age. No parental consanguinity was present in pedigrees. Initial clinical manifestations varied between patients but generally included: gait disturbances, language problems, visual impairment, seizures and psychomotor regression. Cortical and cerebellar atrophy was a constant finding when neuroimaging was performed. Seizure medication was a common element of treatment regimens. CONCLUSIONS: This investigation supports that the previously characterized c.214G > T mutation is the most common causative NCL mutation in the Costa Rican population. This mutation is geographically widespread among Costa Rican NCL patients and yields a clinical presentation similar to that observed for CLN6 NCL patients in other geographies.

Revealing the clinical phenotype of atypical neuronal ceroid lipofuscinosis type 2 disease: Insights from the largest cohort in the world.

AIM: Neuronal ceroid lipofuscinosis type 2 (CLN2) disease is an autosomal recessive inherited neurodegenerative lysosomal storage disorder caused by deficient tripeptidyl peptidase 1 (TPP1) enzyme, leading to progressive deterioration of neurological functions commonly occurring in children aged 2-4 years and culminating in early death. Atypical cases associated with earlier or later symptom onset, or even protracted course, have already been reported. Such variable manifestations may constitute an additional challenge to early diagnosis and initiation of appropriate treatment. The present work aimed to analyse clinical data from a cohort of Latin American CLN2 patients with atypical phenotypes. METHODS: Experts in inborn errors of metabolism from Latin America selected patients from their centres who were deemed by the clinicians to have atypical forms of CLN2, according to the current literature on this topic and their practical experience. Clinical and genetic data from the medical records were retrospectively revised. All cases were presented and analysed by these experts at an Advisory Board Meeting in São Paulo, Brazil, in October 2018. RESULTS: Seizures, language abnormalities and behavioural disorders were found as the first manifestations, appearing at the median age of 6 years, an older age than classically described for the late infantile form. Three novel mutations were also identified. CONCLUSION: Our findings reinforce the inclusion of CLN2 in the differential diagnosis of children presenting with seizures, behavioural disorders and language abnormalities. Early diagnosis will allow early initiation of specific therapy.

Late-onset childhood neuronal ceroid lipofuscinosis: Early clinical and electroencephalographic markers.

PURPOSE: The objective of the study was to describe the initial clinical and electroencephalographic findings in children with late-infantile neuronal ceroid lipofuscinosis (LINCL). METHOD: The clinical charts of 35 patients seen between 1990 and 2016 were reviewed. The patients were divided into two groups: Group 1 (G1) consisting of 12 patients with NCL type 2 (CLN2) disease confirmed by enzymatic activity in dried blood spots on filter paper and/or genetic studies, and Group 2 (G2) consisting of 23 patients with a diagnosis of LINCL based on pathology studies by muscle biopsy. RESULTS: Mean age at symptom onset was 3 years in G1 and 3.4 years in G2. Symptoms at onset were epilepsy in 58%, language delay in 34%, and gait disturbances in 8% of patients in G1 and epilepsy in 52.1%, language delay in 26%, gait disturbances in 17.4%, and loss of visual acuity in 4.5% in G2. The most common seizure types in G1 patients were myoclonic in 3/7, generalized tonic-clonic in 2/7, focal motor in 1/7, and febrile seizures in 1/7; in G2 patients they were myoclonic in 5/12, generalized tonic-clonic in 3/12, myoclonic-atonic in 2/12, and febrile seizures in 2/12. A photoparoxysmal response to intermittent photic stimulation (IPS) was found in the initial EEG in 9/12 patients in G1 (mean age 3.8 years) and in 10/13 patients in G2 (mean age 3.9 years). CONCLUSIONS: There were no significant differences between both groups. Seizures, especially myoclonic, are the most common symptom at onset followed by language delay and gait disturbances. Low-frequency IPS is a useful study that may help facilitate the diagnosis of the disease.

Retinal function in patients with the neuronal ceroid lipofuscinosis phenotype.

PURPOSE:: To analyze the clinical features, visual acuity, and full-field electroretinogram (ERG) findings of 15 patients with the neuronal ceroid lipofuscinosis (NCL) phenotype and to establish the role of ERG testing in NCL diagnosis. METHODS:: The medical records of five patients with infantile NCL, five with Jansky-Bielschowsky disease, and five with juvenile NCL who underwent full-field ERG testing were retrospectively analyzed. RESULTS:: Progressive vision loss was the initial symptom in 66.7% of patients and was isolated or associated with ataxia, epilepsy, and neurodevelopmental involution. Epilepsy was present in 93.3% of patients, of whom 86.6% presented with neurodevelopmental involution. Fundus findings ranged from normal to pigmentary/atrophic abnormalities. Cone-rod, rod-cone, and both types of dysfunction were observed in six, one, and eight patients, respectively. CONCLUSION:: In our study, all patients with the NCL phenotype had abnormal ERG findings, and the majority exhibited both cone-rod and rod-cone dysfunction. We conclude that ERG is a valuable tool for the characterization of visual dysfunction in patients with the NCL phenotype and is useful for diagnosis.

Retinal function in patients with the neuronal ceroid lipofuscinosis phenotype / Estudo da função retiniana em pacientes com o fenótipo da lipofuscinose ceróide neuronal

ABSTRACT Purpose: To analyze the clinical features, visual acuity, and full-field electroretinogram (ERG) findings of 15 patients with the neuronal ceroid lipofuscinosis (NCL) phenotype and to establish the role of ERG testing in NCL diagnosis. Methods: The medical records of five patients with infantile NCL, five with Jansky-Bielschowsky disease, and five with juvenile NCL who underwent full-field ERG testing were retrospectively analyzed. Results: Progressive vision loss was the initial symptom in 66.7% of patients and was isolated or associated with ataxia, epilepsy, and neurodevelopmental involution. Epilepsy was present in 93.3% of patients, of whom 86.6% presented with neurodevelopmental involution. Fundus findings ranged from normal to pigmentary/atrophic abnormalities. Cone-rod, rod-cone, and both types of dysfunction were observed in six, one, and eight patients, respectively. Conclusion: In our study, all patients with the NCL phenotype had abnormal ERG findings, and the majority exhibited both cone-rod and rod-cone dysfunction. We conclude that ERG is a valuable tool for the characterization of visual dysfunction in patients with the NCL phenotype and is useful for diagnosis.

RESUMO Objetivo: Analisar o quadro clínico, a acuidade visual e o eletrorretinograma de campo total (ERG) de 15 pacientes com o fenótipo da lipofuscinose ceróide neuronal (LCN), estabelecendo o papel do eletrorretinograma no seu diagnóstico. Métodos: Eletrorretinograma foi realizado em 5 pacientes com lipofuscinose ceróide neuronal infantil, 5 com doença de Jansky-Bielschowsky e 5 com lipofuscinose ceróide neuronal juvenil sendo feita uma análise retrospectiva dos registros médicos. Resultados: A perda progressiva da acuidade visual foi o sintoma inicial em 66,7%; isolada ou associada à ataxia, epilepsia e involução do desenvolvimento neuropsico motor. Epilepsia foi o sintoma inicial em 93,3% e 86,6% apresentaram involução do desenvolvimento neuropsicomotor. Achados fundoscópicos variaram de normal a alterações pigmentares/atróficas. Disfunção de cone-bastonete foi constatada em 6 pacientes, bastonete-cone em 1 e em 8 pacientes observou-se disfunção proporcional de ambos os sistemas. Conclusão: O eletrorretinograma foi alterado em todos os pacientes, e o achado mais frequente foi o comprometimento de cones e bastonetes. O eletrorretinograma constitui, portanto, uma ferramenta valiosa para caracterizar a disfunção visual em pacientes com o fenótipo da lipofuscinose ceróide neuronal, contribuindo para seu diagnóstico.

Exome sequencing is an efficient tool for variant late-infantile neuronal ceroid lipofuscinosis molecular diagnosis.

The neuronal ceroid-lipofuscinoses (NCL) is a group of neurodegenerative disorders characterized by epilepsy, visual failure, progressive mental and motor deterioration, myoclonus, dementia and reduced life expectancy. Classically, NCL-affected individuals have been classified into six categories, which have been mainly defined regarding the clinical onset of symptoms. However, some patients cannot be easily included in a specific group because of significant variation in the age of onset and disease progression. Molecular genetics has emerged in recent years as a useful tool for enhancing NCL subtype classification. Fourteen NCL genetic forms (CLN1 to CLN14) have been described to date. The variant late-infantile form of the disease has been linked to CLN5, CLN6, CLN7 (MFSD8) and CLN8 mutations. Despite advances in the diagnosis of neurodegenerative disorders mutations in these genes may cause similar phenotypes, which rends difficult accurate candidate gene selection for direct sequencing. Three siblings who were affected by variant late-infantile NCL are reported in the present study. We used whole-exome sequencing, direct sequencing and in silico approaches to identify the molecular basis of the disease. We identified the novel c.1219T>C (p.Trp407Arg) and c.1361T>C (p.Met454Thr) MFSD8 pathogenic mutations. Our results highlighted next generation sequencing as a novel and powerful methodological approach for the rapid determination of the molecular diagnosis of NCL. They also provide information regarding the phenotypic and molecular spectrum of CLN7 disease.

[Tripeptidyl peptidase 1 in patients with late infantile neuronal ceroid lipofuscinosis]. / Tripeptidil peptidasa 1 en pacientes con ceroidolipofuscinosis neuronal infantil tardía.

INTRODUCTION: Neuronal ceroid lipofuscinoses are a group of inherited autosomal recessive lysosomal diseases, most commonly found in infancy. These are neuropathologically characterised by accumulation of an autofluorescent lipopigment in neurons and other cells. This condition is clinically characterised by loss of motor and cognitive skills, lack of motor coordination, ataxia, progressive visual impairment, behavioural changes; seizures of difficult to manage seizures, particularly myoclonic, and premature death. Ten clinical forms have been described, one of which is late infantile where clinical signs begin between two and four years. The gene responsible for this disease is located at 11p15 locus, and the enzyme encoded by this gene is the tripeptidyl peptidase 1. PATIENTS AND METHODS: We standardised the technique for the enzymatic diagnosis of late infantile neuronal ceroid lipofuscinoses from dried blood on filter paper card in 76 healthy individuals adults and children in order to establish a normal range in the Venezuelan population. The tripeptidyl peptidase activity was also determined in 9 patients with a clinical diagnosis of late infantile neuronal ceroid lipofuscinoses. RESULTS: Six of the samples showed activity lower than the lowest control value (0.11 to 0.45 nmol/spot) from healthy controls of infantile age, confirming the enzymatic diagnosis. Three of the 14 parent samples analysed showed values in the heterozygote ranges. CONCLUSIONS: The enzymatic diagnosis of late infantile neuronal ceroid lipofuscinoses from dried blood on filter paper card is a rapid, easier, less expensive and accurate molecular diagnosis tool.

[Pitfalls in the clinical and electroencephalographic diagnosis of ceroid lipofuscinosis]. / Dificuldades no diagnóstico clínico e eletrencefalográfico de lipofuscinose ceróide neuronal.

Neuronal ceroid lipofuscinosis (NCL) were traditionally classified according to age of onset and clinical features in four main groups. Recently, a combination of clinical, ultra structural and genetics data led to the recognition of eight forms of NCL, providing a more precise framework to classify atypical cases. By the other hand, it was shown that mutations in the same gene could be responsible for a large variety of clinical phenotypes. The objective of this study is to describe two brothers with clinical and electroencephalographic abnormalities characteristic of juvenile NCL, but with ultra structural abnormalities suggestive of late infantile NCL. Electroencephalogram is useful for clinical diagnosis of NCL but it is not helpful in its classification.

[Clinical and electroencephalographic aspects of late infantile neuronal ceroid lipofuscinosis]. / Lipofuscinosis neuronal ceroidea infantil tardía: aspectos clínicos y electroencefalográficos.

AIMS: In this paper we describe the clinical characteristics, and particularly the epileptic seizures and electroencephalographic findings, in 15 patients with a pathology diagnosis of late infantile neuronal ceroid lipofuscinosis (NCL). PATIENTS AND METHODS: Nine female and six male patients were studied and their clinical records covering the period February 1990 to June 2003 were analysed. Neuroimaging, neurometabolic studies, ERG, PE and repeated EEG were carried out in all cases. RESULTS: The mean age on onset of the disease was 3 years (range: 1-5 years). The initial symptom was epilepsy in all cases. Massive myoclonias and myoclonic-atonic seizures were the most frequent kinds of attacks. Focal myoclonias were observed in six patients. Other types of epileptic seizures observed included generalised tonic-clonic, absence, motor focal and complex focal. The epileptic seizures were resistant to therapy. Progressive neurological and visual impairment, pyramidal and cerebellar signs, as well as mental retardation were present in all cases. Intercritical EEG recordings showed diffuse paroxysms with spike and polyspike waves, multifocal spikes and, less often, focal spikes that were predominant in posterior regions. Photostimulation showed high amplitude (300-450) occipital spikes during the application of light stimulation between 1 and 8 Hz. ERG, VEP and SSEP results were pathological. Images showed signs of brain and cerebellar atrophy. Seven of the patients died between 8.5 and 11 years of age. CONCLUSIONS: Late infantile NCL must be considered in the case of a child aged between 1 and 5 years who presents seizures that are predominantly generalised myoclonias and myoclonic-atonic, in association with progressive neurological deterioration including pyramidal, cerebellar and visual signs and an EEG trace showing occipital paroxysms triggered by low frequency photostimulation.

Dificuldades no diagnóstico clínico e eletrencefalográfico de lipofuscinose ceróide neuronal / Pitfalls in the clinical and electroencephalographic diagnosis of ceroid lipofuscinosis

Tradicionalmente, as lipofuscinoses ceróides neuronais (LCN) eram classificadas de acordo com a idade de início e características clínicas em quatro grandes grupos. Recentemente, os estudos genéticos possibilitaram uma classificação mais pormenorizada dessa entidade em oito formas, permitindo o diagnóstico mais preciso de casos previamente considerados atípicos. Por outro lado, foi demonstrado que mutações de um mesmo gene poderiam ser responsáveis por grande variedade de fenótipos clínicos. O objetivo deste estudo é apresentar dois irmãos com achados clínicos e eletrencefalográficos compatíveis com a forma juvenil de LCN mas com alterações ultra-estruturais características da forma infantil tardia dessa doença. Os achados eletrencefalográficos auxiliam no diagnóstico da LCN, mas pouco contribuem na sua classificação.

[Characterization of neuronal ceroid lipofuscinosis in Venezuelan children]. / Caracterización de la ceroidolipofuscinosis en niños venezolanos.

INTRODUCTION: Neuronal ceroid lipofuscinosis (NCL), represents a group of inherited neurodegenerative disorders. Based on the age of the patient at onset, clinical course and ultrastructural morphology it has been identified three clinical types for the pediatric group: 1) Infantile NCL (INCL); 2) Late infantile NCL (LINCL); and 3) Juvenile NCL (JNCL). Other variants or atypical forms represent around 20% of the NCL in different populations. Genetic advances have made possible a better characterization, diagnostic and classification of these disorders. CASE REPORTS: We present the clinical, neurophysiological, neuroradiological, and morphological data from 6 patients with NCL, who were assessed at the pediatric neurology department of the Hospital Universitario de Maracaibo during a ten years period (1993 2003). All 6 cases corresponded with the late infantile form. Age of onset ranged form 2 to 5 years. For most of the patients initial symptoms included seizures, psychomotor delay, accompanied by macular degeneration and optic atrophy. The EEG was characterized by high voltage spikes elicited by low frequency photic stimulation, in 5 cases. Neuroimaging findings were characteristic of the late infantile form of the NCL. In three patients a decreased intensity of signal was seen in the thalami and putamen on T2-weighted images. The ultrastructural examination of the samples obtained through a biopsy showed curvilinear bodies in all patients. CONCLUSION: There is not epidemiological data of the NCL in Venezuela; it is presumed the presence of clinical forms and variants in the pediatric group. This first study could contribute to the knowledge and a better research of this group of disorders in our population.

Serial MRI findings in the Costa Rican variant of neuronal ceroid-lipofuscinosis.

Widespread cerebral atrophy and basal ganglia involvement are highly suggestive imaging features of the variants of late infantile type neuronal ceroid-lipofuscinosis. In the presence of clinical findings indicative of neuronal ceroid-lipofuscinosis, neuroimaging procedures are highly recommended to differentiate the variants from classic late infantile neuronal ceroid-lipofuscinosis. The clinical features and follow-up magnetic resonance imaging studies in a patient with the Costa Rican variant of late infantile neuronal ceroid-lipofuscinosis is presented. These procedures were of the utmost importance to observe the progression of the neurologic ailment and the extent of the cerebral and cerebellar abnormalities.

[Neurological aspects of ceroid-lipofuscinoses]. / Aspectos neurológicos de la ceroidolipofuscinosis.

OBJECTIVE: We discuss the historical, epidemiological, clinical, complementary tests and neuropathological details of ceroid-lipofuscinoses in children. DEVELOPMENT: Initially, we review the basic concepts and historical details of the disorders, and the frequency and distribution of the different clinical forms. Subsequently, we review the subtypes and variants most commonly found in children, together with the elements necessary for diagnosis. Finally we analyze the neuropathological studies and their clinical correlation. CONCLUSIONS: The clinical diagnosis of ceroid-lipofuscinoses should be based on a clinical history showing disorders of vision, convulsions and regression of psychomotor functions. Neuroimaging findings, neurophysiological changes and ultrastructural studies confirm the diagnosis.

Lipofuscinose ceróide neuronal: relato de quatro casos com estudo por histoquímica retal, microscopia eletrônica de conjuntiva e necrópsia / Neuronal ceroid-lipofuscinosis: report of 4 cases with study by rectal histochemistry, conjunctiva electron mycroscopy and necropsy

Os autores relatam os achados neuropatológicos e clínicos de quatro casos de lipofuscinose ceróide ou doença de Batten. Dois casos foram estudados por necrópsia: o encéfalo mostrou atrofia e neurônios contendo pigmento citoplasmático com características tintoriais de lipofuscina. Um caso foi diagnosticado por estudo histoquímico citoplasmático com características tintoriais de lipofuscina. Um caso foi diagnosticado por estudo histoquímico de biópsia retal, em material congelado em nitrogênio líquido demonstrando-se células ganglionares mioentéricas contendo acúmulo citoplasmático de material granular fosfatase ácida positivo, bem como em grande número de macrófagos do córion. O quarto caso foi diagnosticado por microscopia eletrônica e biópsia de conjuntiva, com identificaçäo de inclusöes curvelíneas membranáceas e tipo impressäo digital

Ceroidolipofuscionosis neural: presentación de 4 pacientes / Neural ceroid-lipofuscionosis: discussion of four cases

Se describen por primera vez en nuestro medio 4 pacientes del sexo femenino, provenientes de 3 familias no emparentadas entre sí, que presentan una enfermedad degenerativa del sistema nervioso central del tipo ceroidolipofuscinosis neuronal forma juvenil o enfermedad de Spielmeyer-Vogt. En una de las familias el cuadro fue de aparición esporádica y en las 3 restantes el modo de herencia fue compatible con el autosómico recesivo. En todos los casos el diagnóstico definitivo se basó en los hallazgos clínicos, electrofisiológicos y ultraestructurales. Se hace énfasis en el estudio morfológico ultraestructural como criterio confirmatorio y para la clasificación de estas entidades