Hypotonia
Hypotonia | |
---|---|
Specialty | Pediatrics |
Symptoms | Muscle weakness |
Hypotonia is a state of low
Hypotonia is thought to be associated with the disruption of
Signs and symptoms
Central hypotonia accounts for 60 to 80% of all hypotonia in infants.[4] Hypotonic patients may display a variety of objective manifestations that indicate decreased muscle tone. Motor skills delay is often observed, along with hypermobile or hyperflexible joints, drooling and speech difficulties, poor reflexes, decreased strength, decreased activity tolerance, rounded shoulder posture, with leaning onto supports, and poor attention. The extent and occurrence of specific objective manifestations depends upon the age of the patient, the severity of the hypotonia, the specific muscles affected, and sometimes the underlying cause. For instance, some people with hypotonia may experience constipation, while others have no bowel problems.
Floppy baby syndrome
The term "floppy infant syndrome" is used to describe abnormal limpness when an infant is born, affecting limbs, trunk, and head. Such condition may appear immediately after birth or during early life as inability to maintain proper posture during movement and rest. In severe cases, hypotonic infants often have difficulty feeding, as their mouth muscles cannot maintain a proper suck-swallow pattern, or a good breastfeeding latch.[5]
Developmental delay
Children with normal muscle tone are expected to achieve certain physical abilities within an average timeframe after birth. Most low-tone infants have delayed
Speech difficulties can result from hypotonia. Low-tone children learn to speak later than their peers, even if they appear to understand a large vocabulary, or can obey simple commands. Difficulties with muscles in the mouth and jaw can inhibit proper pronunciation, and discourage experimentation with word combination and sentence-forming. Since the hypotonic condition is actually an objective manifestation of some underlying disorder, it can be difficult to determine whether speech delays are a result of poor muscle tone, or some other neurological condition, such as intellectual disability, that may be associated with the cause of hypotonia. Additionally, lower muscle tone can be caused by Mikhail-Mikhail syndrome, which is characterized by muscular atrophy and cerebellar ataxia which is due to abnormalities in the ATXN1 gene.[citation needed]
Muscle tone vs. muscle strength
The low muscle tone associated with hypotonia must not be confused with low muscle strength or the definition commonly used in bodybuilding. Neurologic muscle tone is a manifestation of periodic action potentials from motor neurons. As it is an intrinsic property of the nervous system, it cannot be changed through voluntary control, exercise, or diet.[citation needed]
- "True muscle tone is the inherent ability of the muscle to respond to a stretch. For example, quickly straightening the flexed elbow of an unsuspecting child with normal tone, will cause their biceps to contract in response (automatic protection against possible injury). When the perceived danger has passed, (which the brain figures out once the stimulus is removed), the muscle relaxes and returns to its normal resting state."
- "...The child with low tone has muscles that are slow to initiate a muscle contraction, contract very slowly in response to a stimulus, and cannot maintain a contraction for as long as his 'normal' peers. Because these low-toned muscles do not fully contract before they again relax (muscle accommodates to the stimulus and so shuts down again), they remain loose and very stretchy, never realizing their full potential of maintaining a muscle contraction over time. "
Cause
The most common cause of central hypotonia in newborns is
Some conditions known to cause hypotonia include:
- Genetic disorders are the most common cause
- 22q13 deletion syndrome a.k.a. Phelan–McDermid syndrome
- 3-Methylcrotonyl-CoA carboxylase deficiency[6]
- Achondroplasia
- ADNP syndrome
- Aicardi syndrome
- Autism spectrum disorders[7]
- Canavan disease
- Centronuclear myopathy (including myotubular myopathy)
- Central core disease
- CHARGE syndrome
- Cohen syndrome
- Costello syndrome
- Dejerine–Sottas disease (HMSN Type III)
- Down syndrome a.k.a. trisomy 21 — most common
- Ehlers–Danlos syndrome
- Familial dysautonomia (Riley–Day syndrome)
- FG syndrome
- Fragile X syndrome
- GLUT1 deficiency syndrome
- Griscelli syndrome Type 1 (Elejalde syndrome)
- Holocarboxylase synthetase deficiency / Multiple carboxylase deficiency[8]
- Krabbe disease
- Leigh's disease
- Lesch–Nyhan syndrome[9]
- Marfan's syndrome
- Menkes syndrome
- Methylmalonic acidemia
- Myotonic dystrophy
- Niemann–Pick disease
- Nonketotic hyperglycinemia (NKH) or Glycine encephalopathy(GCE)
- Noonan syndrome
- Neurofibromatosis
- Patau syndrome a.k.a. trisomy 13
- Pituitary dwarfism/growth hormone deficiency(in adults)
- Prader–Willi syndrome
- Rett syndrome
- Septo-optic dysplasia (de Morsier syndrome)
- Snyder–Robinson syndrome (SRS)
- Spinal muscular atrophy (SMA)
- Succinic semialdehyde dehydrogenase deficiency (SSADH)
- Tay–Sachs disease
- Werdnig–Hoffmann syndrome – Spinal muscular atrophy with congenital degeneration of anterior horns of spinal cord. Autosomal recessive [10]
- Wiedemann–Steiner syndrome
- Williams syndrome
- Zellweger syndrome a.k.a. cerebrohepatorenal syndrome
- Developmental disability
- Cerebellar ataxia (congenital)
- Sensory processing disorder
- Developmental coordination disorder
- Hypothyroidism (congenital)
- Hypotonic cerebral palsy
- benzodiazepines
Acquired
Acquired – i.e. onset occurs after birth
- Genetic
- Muscular dystrophy (including myotonic dystrophy) – most common
- Metachromatic leukodystrophy
- Rett syndrome
- Spinal muscular atrophy
- Infections
- Encephalitis
- Guillain–Barré syndrome
- Infant botulism
- Meningitis
- Poliomyelitis
- Sepsis
- Toxins
- Infantile acrodynia (childhood mercury poisoning)
- Autoimmunity disorders
- Myasthenia gravis – most common
- Abnormal vaccine reaction
- Celiac disease[11]
- Metabolic disorder
- Neurological
- Traumatic brain injury, such as the damage that is caused by shaken baby syndrome
- Lower motor neuron lesions
- Upper motor neuron lesions
- Miscellaneous
- Central nervous system dysfunction, including cerebellar lesions and cerebral palsy
- Hypothyroidism
- Sandifer syndrome
- Neonatal benzodiazepine withdrawal syndrome in children born to mothers treated in late pregnancy with benzodiazepine medications[12]
Diagnosis
The approach to diagnosing the cause of hypotonia (as with all syndromes in neurology) is first localization. The physician must first determine if the hypotonia is due to muscle, neuromuscular junction, nerve, or central cause. This will narrow the possible causes. If the cause of the hypotonia is found to lie in the brain, then it can be classified as a cerebral palsy. If the cause is localized to the muscles, it can be classified as a muscular dystrophy. If the cause is thought to be in the nerves, it is called hypotonia due to polyneuropathy. Many cases cannot be definitively diagnosed.[13]
Diagnosing a patient includes obtaining family medical history and a physical examination, and may include such additional tests as
Mild or benign hypotonia is often diagnosed by physical and occupational therapists through a series of exercises designed to assess developmental progress, or observation of physical interactions. Since a hypotonic child has difficulty deciphering their spatial location, they may have some recognizable coping mechanisms, such as locking the knees while attempting to walk. A common sign of low-tone infants is a tendency to observe the physical activity of those around them for a long time before attempting to imitate, due to frustration over early failures. Developmental delay can indicate hypotonia.[citation needed]
MRI Brain is used to rule out structural malformations in the brain or metabolic disorders.[4] Magnetic resonance spectroscopic imaging is used to detect metabolic disorders.[4]
Treatment
This section needs more primary sources. (April 2016) |
The outcome in any particular case of hypotonia depends largely on the nature of the underlying disease. In some cases, the underlying cause is treatable. But in general, treatment comprises providing supportive care with rehabilitation services, nutritional and respiratory support.[14]
Along with normal pediatric care, specialists who may be involved in the care of a child with hypotonia include developmental pediatricians (specialize in child development), neurologists, neonatologists (specialize in the care of newborns), geneticists, occupational therapists, physical therapists, speech therapists, orthopedists, pathologists (conduct and interpret biochemical tests and tissue analysis), and specialized nursing care.
If the underlying cause is known, treatment is tailored to the specific disease, followed by symptomatic and supportive therapy for the hypotonia. In very severe cases, treatment may be primarily supportive, such as mechanical assistance with basic life functions like breathing and feeding, physical therapy to prevent muscle atrophy and maintain joint mobility, and measures to try to prevent opportunistic infections such as pneumonia. Treatments to improve neurological status might involve such things as medication for a seizure disorder, medicines or supplements to stabilize a metabolic disorder, or surgery to help relieve the pressure from hydrocephalus (increased fluid in the brain).
The
Occupational therapy can assist the patient with increasing independence with daily tasks through improvement of motor skills, strength, and functional endurance. Speech-language therapy can help with any breathing, speech, and/or swallowing difficulties the patient may be having. Therapy for infants and young children may also include sensory stimulation programs. A physical therapist may recommend an ankle/foot orthosis to help the patient compensate for weak lower leg muscles. Toddlers and children with speech difficulties may benefit greatly by using sign language.
Terminology
The term hypotonia comes from the Ancient Greek ὑπο-, hypo-, 'under' and τόνος, tónos, from τείνω, teinō, 'to stretch'. Other terms for the condition include:[citation needed]
- Low muscle tone
- Benign congenital hypotonia
- Congenital hypotonia
- Congenital muscle hypotonia
- Congenital muscle weakness
- Amyotonia congenita
- Floppy baby syndrome
- Infantile hypotonia
See also
References
- ^ "Hypotonia". MedlinePlus Medical Encyclopedia.
- ^ Sarah Bager (2009). "Central Hyptonia" (PDF). Retrieved 22 April 2017.
- ^ a b c d e f g h i O'Sullivan S. B. (2007). Strategies to Improve Motor Function. In S. B. O’Sullivan, & T. J. Schmitz (Eds.), Physical Rehabilitation (5th Ed.) Philadelphia: F.A. Davis Company.
- ^ PMID 26664445.
- ^ S2CID 8546619.
- ^ "3-methylcrotonyl-CoA carboxylase deficiency (3-MCC deficiency)". Genetics Home Reference. Retrieved 28 November 2013.
- ^ Xue Ming, et al. Prevalence of motor impairment in autism spectrum disorders. Brain and Development. Volume 29, Issue 9, October 2007, Pages 565–570.
- ^ "Holocarboxylase Synthetase Deficiency / Multiple Carboxylase Deficiency". HLCS Gene Sequencing. GeneDx. Archived from the original on 21 September 2019. Retrieved 28 November 2013.
- ISBN 978-1455775668.
- ^ "Motor Neuron Disease (MND): 7 Types, Causes, Symptoms & Treatment".
- PMID 15173490.
- PMID 7881198.
- ^ "The Benign Congenital Hypotonia Site". Archived from the original on 2012-03-05. Retrieved 2007-06-07.
- PMID 32965880, retrieved 2022-02-06
Further reading
- Martin K, Inman J, Kirschner A, Deming K, Gumbel R, Voelker L (2005). "Characteristics of hypotonia in children: a consensus opinion of pediatric occupational and physical therapists". Pediatric Physical Therapy. 17 (4): 275–82. S2CID 24077081.