Hereditary distal muscular atrophy with vocal cord paralysis and sensorineural hearing loss: a dominant form of spinal muscular atrophy?

Intrafamilial Variable Hearing Loss in TRPV4 Induced Spinal Muscular Atrophy

Objective:

Mutations in the transient receptor potential vanilloid 4 gene ( TRPV4) can induce a great diversity of neuropathies. Together with these neuropathies, hearing loss can occur. This study is focused on providing an audiometric phenotype description of a Dutch family with spinal muscular atrophy caused by a mutation in TRPV4.

Methods:

A neurological examination was repeated and pure tone and speech audiometry were performed.

Results:

A large variety in neurological symptoms as well as variation in audiometric characteristics was observed. The severity of hearing loss is mild to moderate and the audiogram configuration is highly variable. The hearing loss of these patients has a progressive nature in general. The frequencies that deteriorate significantly differ between family members. When compared to presbyacusis patients, speech recognition scores of patients with a TRPV4 mutation are not clearly different.

Conclusion:

The function of TRPV4 in the inner ear is still elusive but it is suggested that TRPV4 is required for maintenance of cochlear function in stress conditions, like acoustic injury. We can neither confirm nor reject this based on the results obtained in this family. Therefore, one might consider advising patients with a TRPV4 mutation to avoid exposure to environmental influences such as noise exposure.

Madras motor neuron disease (MMND) is distinct from the riboflavin transporter genetic defects that cause Brown-Vialetto-Van Laere syndrome

Introduction

Madras motor neuron disease (MMND), MMND variant (MMNDV) and Familial MMND (FMMND) have a unique geographic distribution predominantly reported from Southern India. The characteristic features are onset in young, weakness and wasting of limbs, multiple lower cranial nerve palsies and sensorineural hearing loss. There is a considerable overlap in the phenotype of MMND with Brown–Vialetto–Van Laere syndrome (BVVL) Boltshauser syndrome, Nathalie syndrome and Fazio–Londe syndrome. Recently a number of BVVL cases and families have been described with mutations in two riboflavin transporter genes SLC52A2 and SLC52A3 (solute carrier family 52, riboflavin transporter, member 2 and 3 respectively).

Methods and results

We describe six families and four sporadic MMND cases that have been clinically characterized in detail with history, examination, imaging and electrophysiological investigations. We sequenced the SLC52A1, SLC52A2 and SLC52A3 in affected probands and sporadic individuals from the MMND series as well as the C9ORF72 expansion. No genetic defects were identified and the C9ORF72 repeats were all less than 10.

Conclusions

These data suggest that MMND is a distinct clinical subgroup of childhood onset MND patients where the known genetic defects are so far negative. The clinico-genetic features of MMND in comparison with the BVVL group of childhood motor neuron diseases suggest that these diseases are likely to share a common defective biological pathway that may be a combination of genetic and environmental factors.

Reduced penetrance in hereditary motor neuropathy caused by TRPV4 Arg269Cys mutation

Incomplete penetrance has rarely been reported in Charcot-Marie-Tooth disease. Our aim is to describe reduced penetrance in a hereditary motor neuropathy pedigree due to mutation in the transient receptor potential vallinoid 4 (TRPV4) gene. The pedigree comprised two affected members, the proband aged 44 years and her affected daughter aged 7 years, and seven additional related subjects, three of whom were subclinical gene mutation carriers aged 9, 40 and 70 years. Clinico-electrophysiological studies, MRI of lower-limb musculature and genetic testing of the TRPV4 were performed. The proband presented with a moderate facio-scapulo-peroneal syndrome, whereas her symptomatic daughter suffered from severe congenital spinal muscular atrophy with arthrogryposis, laryngomalacia, and vocal cord paresis. Electrophysiological evaluation revealed a pure motor axonal neuropathy. In the proband, MRI showed extensive and widespread fatty atrophy of lower-leg musculature, whereas in thigh musculature there was just mild distal fatty infiltration of vastus lateralis. Genetic testing revealed a heterozygous Arg269Cys mutation in the TPRV4 gene. In all three mutation carriers results from clinical and electrophysiological examination, and MRI of foot and lower-leg musculature were normal. We conclude that non-penetrance may be an integral feature of neuropathic syndromes associated with TRPV4 gene mutation.

Dominant mutations in the cation channel gene transient receptor potential vanilloid 4 cause an unusual spectrum of neuropathies

Hereditary neuropathies form a heterogeneous group of disorders for which over 40 causal genes have been identified to date. Recently, dominant mutations in the transient receptor potential vanilloid 4 gene were found to be associated with three distinct neuromuscular phenotypes: hereditary motor and sensory neuropathy 2C, scapuloperoneal spinal muscular atrophy and congenital distal spinal muscular atrophy. Transient receptor potential vanilloid 4 encodes a cation channel previously implicated in several types of dominantly inherited bone dysplasia syndromes. We performed DNA sequencing of the coding regions of transient receptor potential vanilloid 4 in a cohort of 145 patients with various types of hereditary neuropathy and identified five different heterozygous missense mutations in eight unrelated families. One mutation arose de novo in an isolated patient, and the remainder segregated in families. Two of the mutations were recurrent in unrelated families. Four mutations in transient receptor potential vanilloid 4 targeted conserved arginine residues in the ankyrin repeat domain, which is believed to be important in protein-protein interactions. Striking phenotypic variability between and within families was observed. The majority of patients displayed a predominantly, or pure, motor neuropathy with axonal characteristics observed on electrophysiological testing. The age of onset varied widely, ranging from congenital to late adulthood onset. Various combinations of additional features were present in most patients including vocal fold paralysis, scapular weakness, contractures and hearing loss. We identified six asymptomatic mutation carriers, indicating reduced penetrance of the transient receptor potential vanilloid 4 defects. This finding is relatively unusual in the context of hereditary neuropathies and has important implications for diagnostic testing and genetic counselling.

Brown-Vialetto-Van Laere syndrome

The Brown-Vialetto-Van Laere syndrome (BVVL) is a rare neurological disorder characterized by progressive pontobulbar palsy associated with sensorineural deafness. Fifty-eight cases have been reported in just over 100 years. The female to male ratio is approximately 3:1. The age of onset of the initial symptom varies from infancy to the third decade. The syndrome most frequently presents with sensorineural deafness, which is usually progressive and severe. Lower cranial nerve involvement and lower and upper motor neuron limb signs are common neurological features. Other features include respiratory compromise (the most frequent non-neurological finding), limb weakness, slurring of speech, facial weakness, and neck and shoulder weakness. Optic atrophy, retinitis pigmentosa, macular hyperpigmentation, autonomic dysfunction, epilepsy may occur. The etiopathogenesis of the condition remains elusive. Approximately 50% of cases are familial, of which autosomal recessive is suggested. The remaining cases are sporadic. The diagnosis is usually based on the clinical presentation. Investigations (neurophysiological studies, magnetic resonance imaging of the brain, muscle biopsy, cerebrospinal fluid examination) are done to exclude other causes or to confirm the clinical findings. The differential diagnoses include the Fazio-Londe syndrome, amyotrophic lateral sclerosis, Nathalie syndrome, Boltshauser syndrome and Madras motor neuron disease. Treatment with steroids or intravenous immunoglobulin may result in temporary stabilization of the syndrome. However, the mainstays of management are supportive and symptomatic treatment, in particular assisted ventilation and maintenance of nutrition via gastrostomy. The clinical course of BVVL is variable and includes gradual deterioration (almost half of cases), gradual deterioration with stable periods in between (a third of cases) and deterioration with abrupt periods of worsening (just under a fifth of cases). After the initial presentation, one third of patients survive for ten years or longer.

A Brazilian family with Brown-Vialetto-van Laere syndrome with autosomal recessive inheritance

We report the first Brazilian family with Brown-Vialetto-van Laere syndrome. The presence of consanguineous marriages and illness affecting three sisters and one niece support an autosomal recessive transmission. The age at onset of the illness ranged from 12 to 20 years old. The time interval between hearing loss and involvement of other cranial nerves varied from 3 to 12 years. MRI demonstrated bulbar atrophy and also high intensity signal at T2 weighted and fluid attenuated inversion recovery (FLAIR) sequences.

Recent advances in laryngeal sensorimotor control for voice, speech and swallowing

PURPOSE OF REVIEW

This article reviews advances in knowledge on laryngeal sensorimotor control affecting the assessment, understanding, and treatment of laryngeal motor control disorders in voice, speech, and swallowing. Three topics are covered: new knowledge on laryngeal innervation and central nervous system control from basic research studies, the role of laryngeal sensation in normal swallowing and dysphagia in patients, and new approaches to the restoration of laryngeal motor control after recurrent laryngeal nerve disorders.

RECENT FINDINGS

A significant advance this year was tracing the efferent pathways from the cortex to the brainstem in monkeys. This provided new information on subcortical and brainstem connections in the laryngeal efferent pathways. Laryngeal sensory feedback continued to receive attention, and the role of sensory feedback in the control of the pharyngeal phase of swallowing is now well established. Further developments in neuromotor monitoring of the recurrent laryngeal nerve during thyroidectomy were seen, and a large case series recommended that these techniques become standard practice for surgery for thyroid benign recurrence or malignancy. Finally, the first tissue engineering papers in the field of vocal fold tissue and nerve restoration were published this year, beginning an exciting new approach to restoration of laryngeal motor control.

SUMMARY

Considerable attention has been given to laryngeal muscle physiology, denervation, and sensation in neurolaryngology. Relatively limited understanding is available regarding the central nervous system integrative control of laryngeal function for speech, respiration, and swallowing.

Vialetto-Van Laere syndrome in two sisters born to consanguineous parents

Vialetto-Van Laere syndrome is a rare anterior horn cell disease affecting young persons. Bulbar palsy with deafness is the characteristic feature. Of the total 35 cases reported in the literature, only one case was from India. This article presents the second case report from India.

Hereditary vocal cord palsy

Hereditary vocal cord palsy is an uncommon cause of neonatal stridor that has significant implications for patients, their families, and their future progeny.

Anticipation in a unique family with Charcot-Marie-Tooth syndrome and deafness: delineation of the clinical features and review of the literature

Charcot-Marie-Tooth disease (CMT) is a clinically and genetically heterogeneous group of polyneuropathies characterized by degeneration of peripheral nerves, resulting in distal muscle atrophy, sensory loss, and deformities of hands and feet. We have studied 34 individuals in a large 84-member four-generation central Illinois family with autosomal dominant Charcot-Marie-Tooth and deafness. Nerve conduction velocities are consistent with type 1 CMT. Audiological evaluation revealed both auditory neuropathy and cochlear involvement in affected individuals. There is increasing clinical severity and younger age of onset of CMT and deafness with each progressive generation, suggestive of anticipation (P < 0.05). The proband, a female diagnosed at birth with hypotonia, bilateral vocal cord palsy, swallowing incoordination, and hearing impairment, died at age 18 months. Another individual died at the age of 3 months from hypotonia later attributed to CMT. Genetic analysis indicated that affected individuals in this family do not have the common 1.4 Mb duplication associated with type 1A CMT; however, all affected individuals have a unique G to C transversion at position 248 in coding exon 3 of the peripheral myelin PMP22 gene located on chromosome 17p11.2-p12. This mutation is predicted to cause an Ala67Pro substitution in the second transmembrane domain of PMP22, consistent with the molecular cause of the CMT phenotype. However, it does not explain the cochlear component of the deafness, the clinical observation of anticipation, and other features in this family.

Localization of the gene for distal hereditary motor neuronopathy VII (dHMN-VII) to chromosome 2q14

Distal hereditary motor neuronopathy type VII (dHMN-VII) is an autosomal dominant disorder characterized by distal muscular atrophy and vocal cord paralysis. We performed a genomewide linkage search in a large Welsh pedigree with dHMN-VII and established linkage to chromosome 2q14. Analyses of a second family with dHMN-VII confirmed the location of the gene and provided evidence for a founder mutation segregating in both pedigrees. The maximum three-point LOD score in the combined pedigree was 7.49 at D2S274. Expansion of a polyalanine tract in Engrailed-1, a transcription factor strongly expressed in the spinal cord, was excluded as the cause of dHMN-VII.

Brown-Vialetto-Van Laere syndrome in a large inbred Lebanese family: confirmation of autosomal recessive inheritance?

Brown-Vialetto-Van Laere syndrome or pontobulbar palsy with deafness is a rare disorder characterized by bilateral nerve deafness, a variety of cranial nerve disorders usually involving the motor components of the 7th and 9th to 12th cranial nerves, and less commonly an involvement of spinal motor nerves and upper motor neurons. Familial and sporadic cases have been reported. Based on particular evidence, autosomal recessive, autosomal dominant, and X-linked inheritance, as well as autoimmune origin have been considered. We report on a large inbred Lebanese family with four patients of both sexes, strongly suggesting autosomal recessive inheritance.

Hereditary neuropathy and vocal cord paralysis in a man with childhood diphtheria

We present the case of a 37-year-old Afghani man with a history of childhood diphtheria, who was diagnosed with bilateral vocal cord paralysis at age 15 years. At about this time he developed progressive muscular wasting and distally predominant weakness, and subsequently developed respiratory insufficiency, necessitating nocturnal ventilatory support. His examination suggested a distal symmetric sensorimotor neuropathy, and his brother was similarly affected, although to a lesser degree. Electromyography (EMG) and nerve conduction studies revealed this process to be purely axonal. A diagnosis of possible hereditary motor and sensory neuropathy (HMSN) type IIc, hereditary axonal polyneuropathy with vocal cord paralysis, is proposed, although the question of early diphtheritic involvement of the vocal cords and peripheral nerves is also considered.

A unique point mutation in the PMP22 gene is associated with Charcot-Marie-Tooth disease and deafness

Charcot-Marie-Tooth disease (CMT) with deafness is clinically distinct among the genetically heterogeneous group of CMT disorders. Molecular studies in a large family with autosomal dominant CMT and deafness have not been reported. The present molecular study involves a family with progressive features of CMT and deafness, originally reported by Kousseff et al. Genetic analysis of 70 individuals (31 affected, 28 unaffected, and 11 spouses) revealed linkage to markers on chromosome 17p11.2-p12, with a maximum LOD score of 9.01 for marker D17S1357 at a recombination fraction of .03. Haplotype analysis placed the CMT-deafness locus between markers D17S839 and D17S122, a approximately 0.6-Mb interval. This critical region lies within the CMT type 1A duplication region and excludes MYO15, a gene coding an unconventional myosin that causes a form of autosomal recessive deafness called DFNB3. Affected individuals from this family do not have the common 1.5-Mb duplication of CMT type 1A. Direct sequencing of the candidate peripheral myelin protein 22 (PMP22) gene detected a unique G-->C transversion in the heterozygous state in all affected individuals, at position 248 in coding exon 3, predicted to result in an Ala67Pro substitution in the second transmembrane domain of PMP22.

Familial laryngeal paralysis

Vocal fold paralysis (VFP) is the second most frequent cause of congenital stridor. Although often due to birth trauma, infection, and brainstem abnormalities, most cases are idiopathic. Infrequently, a family history of VFP is elicited, identifying a role for genetic factors in laryngeal function. This study describes a family in which an autosomal dominant form of familial laryngeal abductor paralysis segregates. The typical physical findings, diagnostic and therapeutic considerations, and possible molecular mechanisms of this disorder are discussed in detail.

Chromosome 12-linked autosomal dominant scapuloperoneal muscular dystrophy

Scapuloperoneal syndromes are characterized by their distribution of muscle weakness and wasting. The reported pattern of inheritance has been variable. Both neurogenic and myopathic forms of autosomally dominantly inherited scapuloperoneal syndrome have been described. It has been suggested that these are variants of other neuromuscular diseases. We examined 44 members from a family with 14 members affected with a scapuloperoneal syndrome. Physiological and histological analysis implied that this condition is predominantly myopathic. Linkage analysis was done to confirm the genetic etiology of the disease in this family and to evaluate the possibility that it is a allelic variant of other neuromuscular diseases. Genetic analysis demonstrated linkage of the disease to chromosome 12, which makes it genetically distinct from other loci known to cause neuromuscular disease. Muscle fibers with hyaline desmin-containing cytoplasmic inclusions in combination with focal myopathic changes may be a disease-specific morphological marker of the disease.