Authors: Ariel Heller, MD, MPH, Medical University of South Carolina Sonika Agarwal, MBBS, MD, Children’s Hospital of Philadelphia Reviewed: June 2022 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: Hypotonia is most commonly detected during infancy or early childhood. 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 refers to decreased ability to voluntarily and actively move muscles against resistance. Weakness may arise from any portion of the motor unit including: Acute (sudden) weakness is often caused by: Chronic causes of weakness include: 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: Hypotonia comes in two forms: 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. 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: The first step is determining the cause of a child’s low muscle tone. Then, treatment and therapy can begin. The signs and symptoms of hypotonia can vary. They depend on the underlying cause of the problem. However, common symptoms include: General Causes Hypotonia is caused by problems with the nervous system. These problems can occur for different reasons. General causes can include: 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). 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: Central hypotonia could be related to: 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: Peripheral hypotonia could be related to: Diagnosing hypotonia can require assessing: Diagnostic tests may include: Genetic testing and metabolic testing can also be helpful. This might mean testing how an infant or child metabolizes: Diagnostic tests are usually selected based on: 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: This can help with motor control and overall body strength. This is used to help a child relearn how to carry out daily activities. This can be useful for difficulty with: Follow-ups with specialists may be needed. These specialists can include: 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. Conditions related to hypotonia include: Care Pathway for Therapeutic Interventions for Central Hypotonia 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. 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. 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-weaknessSUMMARY
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Disorder Overview
DESCRIPTION
Muscle weakness.
Muscle tone.
1. Benign congenital hypotonia.
2. Secondary hypotonia.
SIGNS AND SYMPTOMS
CAUSES
Central Hypotonia
Peripheral Hypotonia
LABORATORY INVESTIGATIONS
TREATMENT AND THERAPIES
Physical therapy.
Occupational therapy.
Speech and language therapy.
Feeding and nutrition support.
OUTLOOK
RELATED DISORDERS
Publications
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).Research
References
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