Hypotonia
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Hypotonia
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Authors: Ariel Heller, MD, MPH, Medical University of South Carolina 

Sonika Agarwal, MBBS, MD, Children’s Hospital of Philadelphia 

 Reviewed: June 2022

SUMMARY

Hypotonia is defined as decreased muscle tone. Muscle tone refers to the way muscles resist when another person (or force) stretches or pushes on them. High tone means there is a lot of resistance against this force. Low tone (hypotonia) means there is little resistance. Hypotonia can cause a floppy or “rag doll” appearance in infants. 

A hypotonic infant may:

  • Have a delay in gross motor skill development (milestones): 
    • Holding the head up  
    • Rolling over 
    • Sitting 
    • Pulling to stand 
    • Cruising and walking 
    • Balance and coordination 
  • Have trouble with feeding, speech, or breathing 

Hypotonia is most commonly detected during infancy or early childhood.

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Disorder Overview

DESCRIPTION

Muscle tone indicates how much muscles resist outside forces (passive movement). “Hypo-” means low, so “hypotonia” translates to low tone. It is a medical term meaning decreased muscle tone.  

Even when relaxed, muscles have a small amount of contraction. This gives them a springy feel. It means they have some resistance to passive movement. In hypotonia, this resistance is lower than normal. 

Low muscle tone is not the same as muscle weakness. However, the two conditions can coexist. 

Muscle weakness.

Muscle weakness refers to decreased ability to voluntarily and actively move muscles against resistance. Weakness may arise from any portion of the motor unit including: 

  • Brain 
  • Spinal cord 
  • Peripheral nerves 
  • Muscles 

Acute (sudden) weakness is often caused by: 

  • Severe brain or spinal cord trauma 
  • Brain tumors 
  • Seizures 
  • Infections 
  • Autoimmune processes  

Chronic causes of weakness include:  

  • Neurodegenerative disorders  
  • Cerebral palsy 
  • Endocrine abnormalities 
  • Brain tumors 
  • Congenital skeletal muscle disorders 

Muscle tone.

Muscle tone is regulated by special signals. These travel from the brain to the muscles through the nerves. These signals tell the muscles to contract. Hypotonia is caused by problems with signals in any of the following: 

  • Brain 
  • Spinal cord 
  • Nerves 
  • Muscles

Hypotonia comes in two forms:

1. Benign congenital hypotonia.

This condition is present from birth. It stands alone. It is caused by differences in how the fetus developed. Infants with this form of the disorder are hypotonic at birth or shortly after. Later on, they have normal tone. They also have no other signs of brain dysfunction.

2. Secondary hypotonia.

This occurs when hypotonia is associated with another condition. That condition usually causes progressive loss of muscle tone. For instance, it can be associated with: 

  • A central nervous system (brain and spinal cord) disorder 
  • A primary neuromuscular disorder 
  • A genetic disorder

The first step is determining the cause of a child’s low muscle tone. Then, treatment and therapy can begin.

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SIGNS AND SYMPTOMS

The signs and symptoms of hypotonia can vary. They depend on the underlying cause of the problem. However, common symptoms include: 

  • A floppy or “rag doll” appearance in infants (arms and legs hang down and there is little or no head control) 
  • Difficulty with mobility and posture 
  • Difficulty breathing 
  • Delays in: 
    • Holding the head up 
    • Rolling over 
    • Sitting up without support 
    • Walking 
  • Speech and language disorders 
  • Problems with ligaments and joints 
  • Poor reflexes

CAUSES

General Causes 

Hypotonia is caused by problems with the nervous system. These problems can occur for different reasons. General causes can include:

  • Trauma 
  • Environmental factors 
  • Genetics 
  • Muscle diseases 
  • Central nervous system disorders 
  • Metabolic diseases

More than half of all cases in infants and children are due to genetic variations or metabolic diseases.

Specific Causes 

The nervous system is important to maintaining normal muscle tone. The specific causes of hypotonia tend to affect either the central nervous system (CNS) or the peripheral nervous system (PNS). 

Central Hypotonia

The CNS is made up of the brain and spinal cord. Problems with the CNS cause 60% to 80% of all hypotonia cases in infants and children. These cases are known as central hypotonia. 

Doctors might suspect central hypotonia if they spot certain clues, such as: 

  • Malformations of the organs 
  • Normal or brisk reflexes 
  • Fisting of the hands 

Central hypotonia could be related to:  

Peripheral Hypotonia

The PNS is made up of nerves that travel to the muscles. Problems with the PNS cause 15% to 30% of all hypotonia cases in infants and children. These cases are known as peripheral (or motor unit) hypotonia.  

Doctors might suspect peripheral hypotonia if they spot certain clues, such as: 

  • Absent or slow reflexes 
  • Muscle twitches

Peripheral hypotonia could be related to: 

  • Muscular diseases, such as Duchenne muscular dystrophy and Becker muscular dystrophy 
  • Metabolic disorders 
  • Neuromuscular junction disorders, such as congenital myasthenia and infantile botulism 
  • Disorders of the skeleton 
  • Spinal cord disorders 
Lissencephaly 2

LABORATORY INVESTIGATIONS

Diagnosing hypotonia can require assessing:

  • Motor and sensory skills 
  • Balance and coordination 
  • Mental status 
  • Reflexes 
  • Nerve function 

Diagnostic tests may include:

  • Magnetic resonance imaging (MRI) of the brain or spinal cord 
  • Electromyography (EMG) to evaluate nerve and muscle function 
  • Electroencephalogram (EEG) to measure electrical activity in the brain (if there is concern about seizures) 

Genetic testing and metabolic testing can also be helpful. This might mean testing how an infant or child metabolizes: 

  • Sugars 
  • Fats 
  • Proteins 

Diagnostic tests are usually selected based on:

  • A child’s clinical history 
  • Neurologic exams 
  • Systemic diseases, such as heart or lung diseases 
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TREATMENT AND THERAPIES

Treatment can begin after a diagnosis. Once a diagnosis has been made, the underlying condition is treated first. Then, the child is offered therapies for their symptoms. 

Useful therapies and treatments include: 

Physical therapy.

This can help with motor control and overall body strength.

Occupational therapy.

This is used to help a child relearn how to carry out daily activities.

Speech and language therapy.

This can be useful for difficulty with: 

  • Breathing 
  • Speech 
  • Swallowing 

Feeding and nutrition support.

Follow-ups with specialists may be needed. These specialists can include: 

  • Child neurologists 
  • Geneticists 
  • Neuromuscular specialists 
  • Specialists that understand related parts of the body, such as the heart and lungs 
  • Physical Medicine and Rehabilitation  

OUTLOOK

The outlook for an infant or child with hypotonia varies. It is usually based on the underlying cause.  

On the one hand, hypotonia can get better over time. Treatment, such as physical, occupational, and speech therapies, can help. On the other hand, children that are diagnosed with an underlying genetic condition may worsen overtime.  

Hypotonia is often a lifelong condition.

Publications

Care Pathway for Therapeutic Interventions for Central Hypotonia
Comprehensive information and practical tools for children with hypotonia, ages 0 to 6 years. Compiled by The American Academy for Cerebral Palsy and Developmental Medicine (AACPDM).

Childhood Stroke 1

Child Neurology Foundation (CNF) solicits resources from the community to be included on this webpage through an application process. CNF reserves the right to remove entities at any time if information is deemed inappropriate or inconsistent with the mission, vision, and values of CNF. 

Research 

ClinicalTrials.gov for Hypotonia (birth to 17 years).

These are clinical trials that are recruiting or will be recruiting. Updates are made daily, so you are encouraged to check back frequently. 

ClinicalTrials.gov is a database of privately and publicly funded clinical studies conducted around the world. This is a resource provided by the U.S. National Library of Medicine (NLM), which is an institute within the National Institutes of Health (NIH). Listing a study does not mean it has been evaluated by the U.S. Federal Government. Please read the NLM disclaimer for details.    

Before participating in a study, you are encouraged to talk to your health care provider and learn about the risks and potential benefits.

The information in the CNF Child Neurology Disorder Directory is not intended to provide diagnosis, treatment, or medical advice and should not be considered a substitute for advice from a healthcare professional. Content provided is for informational purposes only.  CNF is not responsible for actions taken based on the information included on this webpage. Please consult with a physician or other healthcare professional regarding any medical or health related diagnosis or treatment options. 

References

Bodensteiner JB. The evaluation of the hypotonic infant. Semin Pediatr Neurol. 2008 Mar;15(1):10-20. PMID: 18342256. https://doi.org/10.1016/j.spen.2008.01.003 

Facts about craniosynostosis [Internet]. Centers for Disease Control and Prevention. Centers for Disease Control and Prevention; 2020 [cited 2022 Mar 21]. Available from: https://www.cdc.gov/ncbddd/birthdefects/craniosynostosis.html 

Hypotonia in babies: Symptoms, causes & treatment [Internet]. Cleveland Clinic [cited 2022 Mar 28]. Available from: https://my.clevelandclinic.org/health/diseases/22223-hypotonia-in-babies#management-and-treatment  

Leyenaar J, Camfield P, Camfield C. A schematic approach to hypotonia in infancy. Paediatr Child Health. 2005 Sep;10(7):397-400. PMID: 19668647; PMCID: PMC2722561. https://doi.org/10.1093/pch/10.7.397 

Muscle weakness (hypotonia) [Internet]. Muscle Weakness Hypotonia. Boston Children’s Hospital [cited 2022 Mar 15]. Available from: https://www.childrenshospital.org/conditions/muscle-weakness-hypotonia   

Piña-Garza JE, James KC. The Hypotonic Infant. In: Fenichel’s clinical pediatric neurology [Internet]. 8th edition. 2019 [cited 2022 Apr 14]. p. 150–71. Available from: https://www.elsevier.com/books/fenichel%27s-clinical-pediatric-neurology/978-0-323-48528-9  

Hypotonia information page [Internet]. U.S. Department of Health and Human Services  National Institute of Neurological Disorders and Stroke [cited 2022 Mar 28]. Available from: https://www.ninds.nih.gov/Disorders/All-Disorders/Hypotonia-Information-Page  

Bodamer O. Approach to the infant with hypotonia and weakness. In: UpToDate [Internet]. 2021 [cited 2022 Apr 14]. Available from: https://www.uptodate.com/contents/approach-to-the-infant-with-hypotonia-and-weakness

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