A Case with Brown-Vialetto-Van Laere Syndrome: A Sudden Onset Auditory Neuropathy Spectrum Disorder

Childhood fever and hearing loss associated with CAPOS syndrome

CAPOS (cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss) syndrome is a rare genetic disorder caused by the heterozygous mutation, c.2452G > A, in the ATP1A3 gene. CAPOS syndrome involves a characteristic episode in which neuropathy develops after a fever in childhood, and here, we describe the case of a patient with CAPOS syndrome. The patient had repeated episodes of a fever around 74 months of age. Although he could speak at 23 months of age, he presented with hearing difficulty after the fever. Pure-tone audiometry revealed moderate-to-severe bilateral sensorineural hearing loss, and auditory brainstem response (ABR) showed poor response in the both ears. Auditory stead-state response (ASSR) produced relatively consistent results compared to pure-tone audiometry. A mutation in the ATP1A3 gene was detected through genetic testing. In CAPOS syndrome, a genetic mutation leads to desynchronization during neural firing. We believe that this desynchronization in neural firing is responsible for the lack of response in the ABR and the presence of a response in the ASSR. In this patient, we attribute the response detection in ASSR to its greater tolerance for errors in the timing of neural firing compared to ABR.

Sudden Onset Auditory Neuropathy Spectrum Disorder: A Rare Case Report of Brown Vialetto Van Laere Syndrome

Brown Vialetto Van Laere syndrome is a rare disorder characterized by progressive pontobulbar palsy with bilateral sensorineural hearing loss and lower cranial nerve palsies. Fifty-eight cases have been reported in the last hundred years. As the most common presenting complaint of this disorder is hearing loss, audiological evaluation plays a vital role in pointing towards and narrowing its diagnosis. We present a case report of a 12-year male child affected by this disorder.

A Case Report of Riboflavin Treatment and Cochlear Implants in a 4-Year-Old Girl with Progressive Hearing Loss and Delayed Speech Development: Brown-Vialetto-Van Laere Syndrome

BACKGROUND Brown-Vialetto-Van Laere (BVVL) syndrome is a rare autosomal recessive disorder caused by mutations in intestinal riboflavin transporter genes, resulting in a motor neuron disorder of childhood, which can be associated with sensorineural deafness. This report describes a 4-year-old Polish girl with progressive hearing loss and delayed speech development diagnosed with Brown-Vialetto-Van Laere syndrome who was treated with riboflavin (vitamin B2) and cochlear implants. CASE REPORT The case report concerns a girl from Poland who, at the age of 2 years 10 months, developed progressive atypical neurological symptoms of unknown etiology: ataxia of the upper and lower limbs, gait abnormalities, generalized muscle weakness, visual and hearing problems, and regression of speech development. A karyotype study (whole-exome sequencing) revealed alterations within SLC52A2, leading to the diagnosis of Brown-Vialetto-Van Laere syndrome and initiation of high-dose riboflavin treatment. As a 4-year-old child, she presented to the Institute of Physiology and Pathology of Hearing - World Hearing Center in Poland with progressive hearing loss and speech regression. Hearing tests revealed bilateral profound sensorineural hearing loss with auditory neuropathy. Surgical treatment was applied in the form of bilateral cochlear implantation. CONCLUSIONS This report shows the importance of genetic testing in infants who present with atypical symptoms or signs. In this case, the diagnosis of Brown-Vialetto-Van Laere syndrome resulted in timely correction of the genetic riboflavin (vitamin B2) deficiency and improved hearing following the use of cochlear implants.

Benefit of high-dose oral riboflavin therapy in riboflavin transporter deficiency

Riboflavin transporter deficiency (RTD) is a progressive inherited neuropathy of childhood onset, characterised by pontobulbar palsy, sensorineural deafness, sensory ataxia, muscle weakness, optic atrophy and respiratory failure. Riboflavin supplementation is beneficial in short-term reports, but the quantum of benefit in various clinical domains is not well understood. A PubMed search was conducted, which identified 94 genetically confirmed cases of RTD who received riboflavin supplementation and had follow-up assessments. Information on the clinical and functional status before and after riboflavin supplementation was collected and analysed. Seventy-six of the 94 patients (80.9%) showed an overall improvement after riboflavin supplementation, and the remaining (19.1%) were stable, though some patients had deteriorations in individual domains with no reported deaths. The domains that had the highest rates of response to riboflavin supplementation were gross motor function (93.3% improved), bulbar palsy (91.3%) and ataxia (90.0%). Improvements were also seen in limb muscle weakness, audiology, facial nerve palsy and respiratory function. Despite treatment, many patients required assistance to ambulate and had severe or profound hearing loss and some remained gastrostomy or tracheostomy dependent. Riboflavin supplementation is a lifesaving intervention for patients with RTD and results in a profound improvement in several functional domains, with early diagnosis and treatment further improving outcomes. Despite treatment, patients are left with residual disability. There is a need to accurately measure functional outcomes in children with RTD and develop additional disease-modifying therapies.

Is auditory neuropathy an appropriate term? A systematic literature review on its aetiology and pathogenesis

To clarify the aetio-pathogenesis of Auditory Neuropathy Spectrum Disorder (ANSD), a total of 845 papers were divided into four categories: Review, Audiology, Treatment and Aetiology. Aetiology was the topic analysed categorising papers as: Genetics, Histopathology, Imaging and Medical diseases. Isolated ANs were in relation to Otoferlin, Pejvakin and DIAPH3 deficiency, and the syndromes were mainly Charcot Marie Tooth, Friedreich Ataxia, mitochondrial disorders and those associated with optic neuropathies. In histopathology papers, important information was available from analyses on human premature newborns and on some syndromic neuropathies. From cochlear dysmorphism to cerebral tumours associated with ANs, these are described in what is identified as the Imaging area. Finally, the prevalent clinical pathology was bilirubinopathy, followed by diabetes. In conclusion, AN/ANSDs do not refer to a clear pathological condition, but to an instrumental pattern without any evidence of auditory nerve involvement, except in a few conditions. The terms AN/ANSD are misleading and should be avoided, including terms such as “synaptopathy” or “dis-synchrony”.

Alteration of Flavin Cofactor Homeostasis in Human Neuromuscular Pathologies

The aim of this short review chapter is to provide a brief summary of the relevance of riboflavin (Rf or vitamin B2) and its derived cofactors flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) for human neuromuscular bioenergetics.Therefore, as a completion of this book we would like to summarize what kind of human pathologies could derive from genetic disturbances of Rf transport, flavin cofactor synthesis and delivery to nascent apoflavoproteins, as well as by alteration of vitamin recycling during protein turnover.

A case report of sudden-onset auditory neuropathy spectrum disorder associated with Brown-Vialetto-Van Laere syndrome (riboflavin transporter deficiency)

OBJECTIVE

The purpose of this paper is to describe a child with auditory neuropathy spectrum disorder (ANSD) associated with Brown-Vialetto-Van Laere (BVVL) syndrome, which is a rare, inherited, neurodegenerative disorder that is caused by defects in riboflavin transporter genes.

DESIGN

We report the audiological and clinical profile of a child who presented with a complaint of sudden loss of speech understanding associated with an atypical form of ANSD. He was later diagnosed with BVVL.

STUDY SAMPLE

An 11-year-old boy with ANSD associated with BVVL.

RESULTS

The patient's severe neurological symptoms improved within a year of supplementation with high doses of riboflavin. His fluctuating hearing loss and 0% WDS remained unchanged. The patient was able to use hearing aids without any discomfort after treatment initiation, but he stopped using them again due to a lack of benefit in speech understanding. Although cochlear implantation was recommended, the patient and his family decided not to consider it for another year since they still had hope for complete recovery.

CONCLUSIONS

Sudden-onset ANSD can be the earliest sign of undetected BVVL syndrome. Early detection of BVVL is crucial since all symptoms can be reversible with an early intervention of high doses of riboflavin supplementation.

Development of Novel Experimental Models to Study Flavoproteome Alterations in Human Neuromuscular Diseases: The Effect of Rf Therapy

Inborn errors of Riboflavin (Rf) transport and metabolism have been recently related to severe human neuromuscular disorders, as resulting in profound alteration of human flavoproteome and, therefore, of cellular bioenergetics. This explains why the interest in studying the “flavin world”, a topic which has not been intensively investigated before, has increased much over the last few years. This also prompts basic questions concerning how Rf transporters and FAD (flavin adenine dinucleotide) -forming enzymes work in humans, and how they can create a coordinated network ensuring the maintenance of intracellular flavoproteome. The concept of a coordinated cellular “flavin network”, introduced long ago studying humans suffering for Multiple Acyl-CoA Dehydrogenase Deficiency (MADD), has been, later on, addressed in model organisms and more recently in cell models. In the frame of the underlying relevance of a correct supply of Rf in humans and of a better understanding of the molecular rationale of Rf therapy in patients, this review wants to deal with theories and existing experimental models in the aim to potentiate possible therapeutic interventions in Rf-related neuromuscular diseases.