A schematic approach to hypotonia in infancy

Nemaline Myopathy in a Hypotonic Neonate: Diagnostic Approach for Early Detection and Management

Neonatal hypotonia presents with low muscle tone and an array of symptoms that vary depending on the etiology. The differential diagnosis for this condition is complex. It is crucial to exclude life-threatening causes before following a diagnostic algorithm and performing additional tests. Given the wide range of clinical symptoms and etiologies for neonatal hypotonia, rapid genetic testing has the potential to expedite diagnosis, reduce invasive testing such as muscle biopsy, reduce hospital stays, and guide condition management.  A four-week-old girl was admitted to the emergency department (ED) with a one-day history of lethargy, poor feeding, congestion, cough, and hypoxemia. Given positive rhino-enterovirus testing and high inflammatory markers, antibiotics were administered. Imaging, venous blood gas, and blood cultures were negative, and the patient was admitted to the pediatric intensive care unit (PICU) for hypoxemia. After speech-language pathology (SLP) and occupational therapy (OT) evaluation, weak orofacial muscles and feeding issues resulted in a nasogastric tube placement. A swallow study revealed decreased pharyngeal contraction and post-swallow liquid residue. Laryngoscopy showed mild laryngomalacia and dysphagia with aspiration. Genetic testing identified an ACTA1 mutation and confirmed nemaline myopathy (NM). The patient's oxygen levels dropped further during sleep, resulting in diagnoses of severe obstructive and moderate-severe central sleep apnea. Treatment included oxygen therapy, SLP, physical therapy, albuterol, and cough assists. After discharge, the patient was frequently re-admitted with chronic respiratory failure and bronchiolitis and later had gastrostomy and tracheostomy tubes inserted.  This specific case highlights the importance of implementing a diagnostic algorithm for neonatal hypotonia. It is also important for physicians, especially emergency medicine (EM) providers, to first exclude infection, sepsis, and cardiac and respiratory organ failure before looking into other tests. Then, physicians should evaluate for more rare etiologies. In this patient's case, the hypotonia was due to a rare genetic disease, nemaline myopathy, and a multidisciplinary approach was used for this patient's care.

Identifying and Evaluating Young Children with Developmental Central Hypotonia: An Overview of Systematic Reviews and Tools

Children with developmental central hypotonia have reduced muscle tone secondary to non-progressive damage to the brain or brainstem. Children may have transient delays, mild or global functional impairments, and the lack of a clear understanding of this diagnosis makes evaluating appropriate interventions challenging. This overview aimed to systematically describe the best available evidence for tools to identify and evaluate children with developmental central hypotonia aged 2 months to 6 years. A systematic review of systematic reviews or syntheses was conducted with electronic searches in PubMed, Medline, CINAHL, Scopus, Cochrane Database of Systematic Reviews, Google Scholar, and PEDro and supplemented with hand-searching. Methodological quality and risk-of-bias were evaluated, and included reviews and tools were compared and contrasted. Three systematic reviews, an evidence-based clinical assessment algorithm, three measurement protocols, and two additional measurement tools were identified. For children aged 2 months to 2 years, the Hammersmith Infant Neurological Examination has the strongest measurement properties and contains a subset of items that may be useful for quantifying the severity of hypotonia. For children aged 2-6 years, a clinical algorithm and individual tools provide guidance. Further research is required to develop and validate all evaluative tools for children with developmental central hypotonia.

Autosomal recessive congenital cataract is associated with a novel 4-bp splicing deletion mutation in a novel C10orf71 human gene

Congenital cataract is one of the most genetically heterogeneous ocular conditions with different genes involved in its etiology. Here, we describe the analysis of a new candidate gene of a congenital bilateral cataract associated with polymalformative syndrome, moderate global developmental delay, microcephaly, axial hypotonia, intrauterine growth restriction and facial dysmorphism for two affected siblings. Molecular analysis included exome sequencing and genome wide homozygosity mapping revealed a region of homozygosity shared by the two affected siblings at 10q11.23. The new C10orf71 gene was included in this interval and direct sequencing of this gene revealed an already described homozygous c. 2123T > G mutation (p. L708R) for the two affected subjects. Interestingly, we revealed in contrast a 4-bp deletion on the 3'-splicing acceptor site of intron 3-exon 4, namely defined as IVS3-5delGCAA. The C10Orf71 gene expression analysis using RT-PCR showed an expression pattern in different fetal organs and tissues as well as in leukocytes and confirmed that the IVS3-5delGCAA deletion of the C10orf71 gene is a splicing mutation responsible for the shortening of the C10orf71 protein in the two related patients. The C10orf71 gene has not been described to date as associated to the autosomal recessive phenotype.

A 43-Day-Old Male With Respiratory Distress and Acute-Onset Hypotonia

A 43-day-old, full-term, previously healthy male presented with decreased activity and oral intake. He was found to be grunting and hypoxemic on examination, and a respiratory pathogen panel was positive for rhinovirus. He was diagnosed with presumed bronchiolitis. His neurologic exam on admission was normal. Because of respiratory failure, he was escalated from high-flow nasal cannula to bilevel positive airway pressure upon admission and he was started on ceftriaxone and vancomycin while awaiting culture data. On hospital day 6, he required escalation of respiratory support. His examination at that time was notable for new hypotonia of his bilateral upper and lower extremities, sluggish pupils, bilateral exotropia, intermittent vertical nystagmus, and an absent Moro reflex. He developed a focal seizure and a computed tomography of the brain demonstrated simple right otomastoiditis. The seizure was attributed to a serum sodium of 113 mmol/L in the setting of syndrome of inappropriate antidiuretic hormone secretion, thought to be secondary to viral bronchiolitis. However, as the patient's sodium was corrected to a normal range, he continued to have neurologic deficits on examination. Given his persistent hypotonia and respiratory failure, atypical for the expected course of viral bronchiolitis, the patient underwent an extensive neurologic and infectious workup, which ultimately revealed a surprising diagnosis.

Child Neurology: Hypotonia and Delayed Teeth Eruption in a 2-Year-Old Female

POLR3- related disorders are rare hypo-myelinating leukodystrophies associated with hypodontia. We present a female patient, who was referred to pediatric neurology at 2 years of age for tremor, low tone, and motor delays. Additionally, she was noted to have a delay in her teeth eruption and myopia. Neurological examination was significant for ataxic features and global developmental delay. Laboratory workup was unrevealing. MRI imaging was significant for hypomyelination. Genetic testing confirmed a pathogenic variant of POLR3B. POLR3- related leukodystrophies should be considered in patients who present with hypotonia, ataxia and hypodontia. There are many different subtypes of POLR-related leukodystrophies each with distinguishing phenotypic and radiographic features. Although, MRI can be helpful in initial evaluation genetic testing is needed for confirmatory diagnosis and to guide prognosis.

Awareness screening and referral patterns among pediatricians in the United States related to early clinical features of spinal muscular atrophy (SMA)

BACKGROUND

Spinal Muscular Atrophy (SMA), a leading genetic cause of death in infants, is an autosomal recessive neuromuscular disease characterized by progressive muscle weakness and atrophy. While early diagnosis of SMA is critical to modifying disease progression and improving outcomes, serious diagnostic delays persist. There is a need to improve SMA awareness, screening, and referral patterns.

METHODS

Two online surveys, developed by Cure SMA for general pediatricians, were distributed by Medscape Education via email (September 2018, n = 300, December 2019, n = 600). The surveys asked about adherence to the American Academy of Pediatrics (AAP) developmental screening and surveillance guidelines, comfort with identification of early signs of neuromuscular disease (NMD), familiarity with SMA, and barriers to timely referral.

RESULTS

In 2018, 70.3% of survey respondents indicated comfort in identifying early signs of NMD and 67.3% noted familiarity with SMA. 52.7% correctly indicated the need for genetic testing to make a definitive diagnosis of SMA, 74.0% meet or exceed developmental screening recommendations, and 52.0% said they would immediately refer to a specialist. In 2019, with a larger sample, 73.0% adhere to developmental screening guidelines, and awareness of the genetic testing requirement for SMA was significantly lower by 7.7% (p < 0.03). Specialist wait times emerged as a barrier to referral, with 64.2% of respondents citing wait times of 1-6 months.

CONCLUSIONS

Many pediatricians underutilize developmental screening tools and lack familiarity with diagnostic requirements for SMA. Continuing efforts to expand awareness and remove barriers to timely referral to SMA specialists, including reducing appointment wait times, are needed.

The association of prenatal exposure to intensive traffic with early preterm infant neurobehavioral development as reflected by the NICU Network Neurobehavioral Scale (NNNS)

INTRODUCTION

Traffic-related air pollution has been shown to be neurotoxic to the developing fetus and in term-born infants during early childhood. It is unknown whether there is an increased risk of adverse neurobehavioral outcome in preterm infants exposed to higher levels of air pollution during the fetal period.

OBJECTIVE

To assess the association between prenatal exposure to traffic-related air pollution on early preterm infant neurobehavior.

METHODS

Air pollution exposure was estimated by two methods: density of major roads and density of vehicle-miles traveled (VMT), each at multiple buffering areas around residential addresses. We examined the association between prenatal exposure to traffic-related air pollution and performance on the Neonate Intensive Care Unit (NICU) Network Behavioral Scale (NNNS), a measure of neurobehavioral outcome in infancy for 240 preterm neonates enrolled in the NICU-Hospital Exposures and Long-Term Health cohort. Linear regression analysis was conducted for exposure and individual NNNS subscales. Latent profile analysis (LPA) was applied to classify infants into distinct NNNS phenotypes. Multinomial logistic regression analysis was conducted between exposure and LPA groups. Covariates included gestational age, birth weight z-score, post-menstrual age at NNNS assessment, socioeconomic status, race, delivery type, maternal smoking status, and medical morbidities during the NICU stay.

RESULTS

Among all 13 NNNS subscales, hypotonia was significantly associated with VMT (10⁴ vehicle-mile/km²) in 150 m (β = 0.01, P-value<0.001), 300 m (β = 0.01, P-value = 0.003), and 500 m (β = 0.01, P-value = 0.002) buffering areas, as well as with road density in a 500 m buffering area (β = 0.03, P-value = 0.03). We identified three NNNS phenotypes by LPA. Among them, high density of major roads within 150 m, 300 m, and 500 m buffers of the residential address was significantly associated with the same phenotype (P < 0.05).

CONCLUSION

Prenatal exposure to intensive air pollution emitted from major roads may impact early neurodevelopment of preterm infants. Motor development may be particularly sensitive to air pollution-related toxicity.

Muscle weakness and impaired motor coordination in hyperpolarization-activated cyclic nucleotide-gated potassium channel 1-deficient rats

Hyperpolarization-activated cyclic nucleotide-gated potassium channel 1 (HCN1) contribute to spontaneous rhythmic activity in different tissues, including the heart and brain. Deficiency in HCN1 function is associated with sick sinus syndrome in mice and epilepsy in humans. We recently developed Hcn1-deficient rats and found that they exhibit absence epilepsy. While rearing Hcn1-deficient rats, we noticed loose muscle tension and abnormal gait. We therefore evaluated the muscle strength and motor functions of Hcn1-deficient rats. When subjected to the wire hang test, Hcn1-deficient rats fell down more easily than control F344 rats. Grip strength of Hcn1-deficient rats was significantly smaller than F344 rats. In the inclined plane test, they exhibited a smaller maximum angle. In the rotarod test, the latency to fall was shorter for Hcn1-deficient rats than F344 rats. In the footprint analysis, Hcn1-deficient rats exhibited smaller step length and wider step width than F344 rats. Instead of poor motor coordination ability and muscle weakness, Hcn1-deficient rats exhibited normal electromyograms, muscle histology, and deep tendon reflex. These findings suggest that HCN1 channels contribute to motor coordination and muscle strength, and that the muscle weakness of Hcn1-deficient rats results from the involvement not of the peripheral but of the central nervous system.

Hypotonia and Lethargy in a Two-Day-Old Male Infant

A 2-day old term male infant was found to be hypotonic and minimally reactive during routine nursing care in the newborn nursery. At 40 hours of life, he was hypoglycemic and had intermittent desaturations to 70%. His mother had an unremarkable pregnancy and spontaneous vaginal delivery. The mother's prenatal serology results were negative for infectious risk factors. Apgar scores were 9 at 1 and 5 minutes of life. On day 1 of life, he fed, stooled, and voided well. Our expert panel discusses the differential diagnosis of hypotonia in a neonate, offers diagnostic and management recommendations, and discusses the final diagnosis.

Evidence-Based Clinical Algorithm for Hypotonia Assessment: To Pardon the Errs

Despite the many advances in diagnostics, the clinical assessment of children with hypotonia presents a diagnostic challenge for clinicians due to the current subjectivity of the initial clinical assessment. The aim of this paper is to report on an evidence-based clinical algorithm (EBCA) that was developed for the clinical assessment of hypotonia in children as part of the output of a multiphased study towards assisting clinicians in more accurate assessments. This study formed part of a larger advanced mixed methods design. The preceding phases of the study included a systematic review, a survey amongst clinicians, a consensus process (Delphi technique), and a qualitative critique with multiple focus groups. Samples were drawn from three professional groups (occupational therapists, physiotherapists, and paediatricians). Data were analysed at each stage and merged in the development of the EBCA. The EBCA followed a rigorous process of development and critique. The methods for formulating changes in the revision and development of the EBCA are presented together with a description and presentation of the final algorithm for practice. The overarching concepts that guided the development and refinement of the EBCA are described, taking into consideration knowledge translation, evidence-based practice, and the value of EBCAs in addition to recommendations for stakeholder uptake. The EBCA is envisaged to be useful in practice for clinicians who are faced with the assessment of a child that is suspected as having hypotonia via a systematic process in identifying specific characteristics that are associated with low muscle tone.

Congenital Hypotonia in Toddlerhood

David is a 22-month-old boy who is new to your practice. He recently moved from a rural area in the Midwest. His father is in the United States Air Force, and his mother works as a full-time homemaker. Their household includes 5 older siblings. The family moves every year because of the father's Air Force placement.David was born full-term in Virginia, with no reported pregnancy complications and no alcohol, tobacco, or drug exposure. He was delivered vaginally, with Apgar scores of 7 and 9, respectively and no respiratory issues. In the newborn nursery, his nurse noted that he was floppy, with generalized low muscle tone. Laboratory work performed included normal thyroid studies and a chromosomal microarray.Because of persistent hypotonia, he was seen by a pediatric neurologist at 9 months of age. A magnetic resonance imaging was performed and was normal, with no structural deficits noted. He was referred to Early Intervention at 6 months, when he was not yet rolling over. He received physical therapy for a few months before the family moved again for his father's next placement.David presents in your office as a sweet nondysmorphic toddler who maintains steady eye contact and smiles responsively. His height, head circumference, and weight are at the 50th percentile. His physical examination is notable for generalized hypotonia, with intact upper and lower deep tendon reflexes. He spontaneously says about 20 words. He turns his head when his name is called and can follow a simple command, such as "clap, clap." He reaches his whole hand toward desired objects and will look at his parents if they are out of reach. He can grasp a block, bang, and transfer objects. He demonstrates an immature pincer grasp. He can roll over and sit independently and is just beginning to pull to a stand. His parents report he has recently restarted Early Intervention, where he is receiving physical, speech, and occupational therapy. His audiology examination is normal.His parents' primary concern today is regarding feeding. David is a picky eater. He has difficulty with new foods and textures. The parents noticed a regression in his tolerance for new foods around the recent move. He eats baby puffs, stage 2 to 3 baby foods, and fruit and vegetable pouches. He does not like soft, sticky foods. He is also reported to have other sensory sensitivities. He does not tolerate loud noises and is bothered by tags in his clothing. You wonder, what further work-up would be helpful for David? How can his feeding issues be addressed?

'Toning' up hypotonia assessment: A proposal and critique

Background

Clinical assessment of hypotonia is challenging due to the subjective nature of the initial clinical evaluation. This poses dilemmas for practitioners in gaining accuracy, given that the presentation of hypotonia can be either a non-threatening or malevolent sign. The research question posed was how clinical assessment can be improved, given the current contentions expressed in the scientific literature.

Objectives

This paper describes the development and critique of a clinical algorithm to aid the assessment of hypotonia.

Methods

An initial exploratory sequential phase, consisting of a systematic review, a survey amongst clinicians and a Delphi process, assisted in the development of the algorithm, which is presented within the framework of the International Classification of Functioning, Disability and Health. The ensuing critique followed a qualitative emergent–systematic focus group design with a purposive sample of 59 clinicians. Data were analysed using semantical content analysis and are presented thematically with analytical considerations.

Results

This study culminated in the development of an evidence-based clinical algorithm for practice. The qualitative critique of the algorithm considered aspects such as inadequacies, misconceptions and omissions; strengths; clinical use; resource implications; and recommendations.

Conclusions

The first prototype and critique of a clinical algorithm to assist the clinical assessment of hypotonia in children has been described. Barriers highlighted include aspects related to knowledge gaps of clinicians, issues around user-friendliness and formatting concerns. Strengths identified by the critique included aspects related to the evidence-based nature of the criteria within the algorithm, the suitability of the algorithm in being merged or extending current practice, the potential of the algorithm in aiding more accurate decision-making, the suitability of the algorithm across age groups and the logical flow. These findings provide a starting point towards ascertaining the clinical utility of the algorithm as an essential step towards evidence-based praxis.

A structured approach to the assessment of a floppy neonate

Hypotonia in a newborn presents a diagnostic challenge for clinicians. It is an important clinical feature that may indicate an underlying systemic illness or neurological problem at the level of the central or peripheral nervous system. It is important to know the different presentations of hypotonia and to have the knowledge of the diagnostic work up which requires multidisciplinary assessment and input and the prognostic implications of these disorders. This review article presents a structured approach highlighting initial assessment, examination, and management of a neonate with generalized hypotonia.

Magnetic Resonance Imaging of Brain in Evaluation of Floppy Children: A Case Series

Objective Hypotonia is a common clinical entity well recognized in pediatric age group, which demands experienced clinical assessment and an extensive array of investigations to establish the underlying disease process. Neuroimaging comes as great help in diagnosing the disease process in rare cases of central hypotonia due to structural malformations of brain and metabolic disorders and should always be included as an important investigation in the assessment of a floppy child. In this article, we discuss the MRI features of eight cases of central and two cases of combined hypotonia and the importance of neuroimaging in understanding the underlying disease in a hypotonic child.

Development of an evidence-based clinical algorithm for practice in hypotonia assessment: a proposal

Background

Assessing muscle tone in children is essential during the neurological assessment and is often essential in ensuring a more accurate diagnosis for appropriate management. While there have been advances in child neurology, there remains much contention around the subjectivity of the clinical assessment of hypotonia, which is often the first step in the diagnostic process.

Objective

In response to this challenge, the objective of the study is to develop and validate a prototype of a decision making process in the form of a clinical algorithm that will guide clinicians during this assessment process.

Methods

Design research within a pragmatic stance will be employed in this study. Multi-phase stages of assessment, prototyping and evaluation will occur. These will include processes that include a systematic review, processes of reflection and action as well as validation methods. Given the mixed methods nature of this study, use of NVIVO or ATLAS-ti will be used in the analysis of qualitative data and SPSS for quantitative data.

Results

Initial results from the systematic review revealed a paucity of scientific literature that documented the objective assessment of hypotonia in children. The review identified the need for more studies with greater methodological rigor in order to determine best practice with respect to the methods used in the assessment of low muscle tone in the paediatric population.

Conclusions

It is envisaged that this proposal will contribute to a more accurate clinical diagnosis of children with low muscle tone in the absence of a gold standard. We anticipate that the use of this tool will ultimately assist clinicians towards moving to evidenced based practice whilst upholding best practice in the care of children with hypotonia.

Consensus on hypotonia via Delphi process

OBJECTIVES

To generate consensus on the assessment of hypotonia in the pediatric population, more specifically with respect to the clinical characteristics and first line tests and methods to be used to assess these characteristics.

METHODS

Consensus methodology was used. A sample of experts was recruited based on specific inclusion criteria. A two-round Delphi process was conducted electronically, which was based on a prior literature appraisal and survey amongst a cohort of clinicians. An a priori threshold margin error of 70 ± 5 % was pre-determined, with Cronbach's α measuring the level of internal consistency.

RESULTS

The 2-round iteration was useful in establishing consensus on clinical characteristics and tests /methods in the assessment of low muscle tone in the pediatric population (2-5 y age band). Twenty-four clinical characteristics, organized into 11 clusters were determined as relevant for inclusion. For each characteristic, one test (as a first line assessment method) had been identified with consensus after two rounds. Additionally, consensus on the importance of collateral sources was determined. The ranking order of importance of characteristics however revealed variations.

CONCLUSIONS

The results of this study have displayed that Delphi, if executed with available guidelines, may be a useful technique in moving towards consensus on issues that may be contentious and have assisted in providing initial data to move towards consensus on the assessment of hypotonia in children.