Hypotonia

Hypotonia, commonly known as floppy baby syndrome, is a state of low muscle tone[1] (the amount of tension or resistance to stretch in a muscle), often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but a potential manifestation of many different diseases and disorders that affect motor nerve control by the brain or muscle strength. Hypotonia is resistance to passive movement, whereas muscle weakness results in impaired active movement. Central hypotonia originates from the central nervous system, while peripheral hypotonia is related to problems within the spinal cord, peripheral nerves and/or skeletal muscles.[2] Recognizing hypotonia, even in early infancy, is usually relatively straightforward, but diagnosing the underlying cause can be difficult and often unsuccessful. The long-term effects of hypotonia on a child's development and later life depend primarily on the severity of the muscle weakness and the nature of the cause. Some disorders have a specific treatment but the principal treatment for most hypotonia of idiopathic or neurologic cause is physical therapy, occupational therapy for remediation, and/or music therapy.

Hypotonia is thought to be associated with the disruption of afferent input from stretch receptors and/or lack of the cerebellum’s facilitatory efferent influence on the fusimotor system, the system that innervates intrafusal muscle fibers thereby controlling muscle spindle sensitivity.[3] On examination a diminished resistance to passive movement will be noted and muscles may feel abnormally soft and limp on palpation.[3] Diminished deep tendon reflexes also may be noted. Hypotonia is a condition that can be helped with early intervention.

Hypotonia
Other namesFloppy baby syndrome
SpecialtyPediatrics

Signs and symptoms

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. Infants who suffer from hypotonia are often described as feeling and appearing as though they are "rag dolls". They are unable to maintain flexed ligaments, and are able to extend them beyond normal lengths. Often, the movement of the head is uncontrollable, not in the sense of spasmatic movement, but chronic ataxia. Hypotonic infants often have difficulty feeding, as their mouth muscles cannot maintain a proper suck-swallow pattern, or a good breastfeeding latch.

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 developmental milestones, but the length of delay can vary widely. Motor skills are particularly susceptible to the low-tone disability. They can be divided into two areas, gross motor skills, and fine motor skills, both of which are affected. Hypotonic infants are late in lifting their heads while lying on their stomachs, rolling over, lifting themselves into a sitting position, remaining seated without falling over, balancing, crawling, and sometimes walking. Fine motor skills delays occur in grasping a toy or finger, transferring a small object from hand to hand, pointing out objects, following movement with the eyes, and self-feeding.

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.

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.

"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

Some conditions known to cause hypotonia include:

Congenital – i.e. disease a person is born with (including genetic disorders presenting within 6 months)

Acquired

Acquired – i.e. onset occurs after birth

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.[11]

Diagnosing a patient includes obtaining family medical history and a physical examination, and may include such additional tests as computerized tomography (CT) scans, magnetic resonance imaging (MRI) scans, electroencephalogram (EEG), blood tests, genetic testing (such as chromosome karyotyping and tests for specific gene abnormalities), spinal taps, electromyography muscle tests, or muscle and nerve biopsy.

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 his spatial location, he 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.

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:

  • Low Muscle Tone
  • Benign Congenital Hypotonia
  • Congenital Hypotonia
  • Congenital Muscle Hypotonia
  • Congenital Muscle Weakness
  • Amyotonia Congenita
  • Floppy Baby Syndrome
  • Infantile Hypotonia

Prognosis and treatment

There is currently no known treatment or cure for most (or perhaps all) causes of hypotonia, and objective manifestations can be lifelong. The outcome in any particular case of hypotonia depends largely on the nature of the underlying disease. In some cases, muscle tone improves over time, or the patient may learn or devise coping mechanisms that enable them to overcome the most disabling aspects of the disorder. However, hypotonia caused by cerebellar dysfunction or motor neuron diseases can be progressive and life-threatening.

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 National Institute of Neurological Disorders and Stroke states that physical therapy can improve motor control and overall body strength in individuals with hypotonia. This is crucial to maintaining both static and dynamic postural stability, which is important since postural instability is a common problem in people with hypotonia.[3] A physiotherapist can develop patient specific training programs to optimize postural control, in order to increase balance and safety.[3] To protect against postural asymmetries the use of supportive and protective devices may be necessary.[3] Physical therapists might use neuromuscular/sensory stimulation techniques such as quick stretch, resistance, joint approximation, and tapping to increase tone by facilitating or enhancing muscle contraction in patients with hypotonia.[3] For patients who demonstrate muscle weakness in addition to hypotonia strengthening exercises that do not overload the muscles are indicated.[3] Electrical Muscle Stimulation, also known as Neuromuscular Electrical Stimulation (NMES) can also be used to “activate hypotonic muscles, improve strength, and generate movement in paralyzed limbs while preventing disuse atrophy (p.498).”[3] When using NMES it is important to have the patient focus on attempting to contract the muscle(s) being stimulated. Without such concentration on movement attempts, carryover to volitional movement is not feasible.[3] NMES should ideally be combined with functional training activities to improve outcomes.

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.

See also

References

  1. ^ "Hypotonia". MedlinePlus Medical Encyclopedia.
  2. ^ Sarah Bager (2009). "Central Hyptonia" (PDF). Retrieved 22 April 2017.
  3. ^ 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.
  4. ^ "3-methylcrotonyl-CoA carboxylase deficiency (3-MCC deficiency)". Genetics Home Reference. Retrieved 28 November 2013.
  5. ^ Xue Ming, et al. Prevalence of motor impairment in autism spectrum disorders. Brain and Development. Volume 29, Issue 9, October 2007, Pages 565–570.
  6. ^ "Holocarboxylase Synthetase Deficiency / Multiple Carboxylase Deficiency". HLCS Gene Sequencing. GeneDx. Retrieved 28 November 2013.
  7. ^ Kliegman, Robert. Nelson Textbook of Pediatrics (20 ed.). p. 747. ISBN 978-1455775668.
  8. ^ http://www.webmd.com/children/werdnig-hoffman-disease
  9. ^ Zelnik N, Pacht A, Obeid R, Lerner A (June 2004). "Range of neurologic disorders in patients with celiac disease". Pediatrics. 113 (6): 1672–6. CiteSeerX 10.1.1.545.9692. doi:10.1542/peds.113.6.1672. PMID 15173490.
  10. ^ McElhatton PR. (November–December 1994). "The effects of benzodiazepine use during pregnancy and lactation". Reprod Toxicol. 8 (6): 461–75. doi:10.1016/0890-6238(94)90029-9. PMID 7881198.
  11. ^ "The Benign Congenital Hypotonia Site". Retrieved 2007-06-07.

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. doi:10.1097/01.pep.0000186506.48500.7c. PMID 16357683.

External links

External resources
13q deletion syndrome

13q deletion syndrome is a rare genetic disease caused by the deletion of some or all of the large arm of human chromosome 13. It causes intellectual disability and congenital malformations that affect a variety of organ systems.

1p36 deletion syndrome

1p36 deletion syndrome (also known as monosomy 1p36) is a congenital genetic disorder characterized by moderate to severe intellectual disability, delayed growth, hypotonia, seizures, limited speech ability, malformations, hearing and vision impairment, and distinct facial features. The symptoms may vary, depending on the exact location of the chromosomal deletion.The condition is caused by a genetic deletion (loss of a segment of DNA) on the outermost band on the short arm (p) of chromosome 1. It is one of the most common deletion syndromes. It is estimated that the syndrome occurs in one in every 5,000 to 10,000 births.

9q34 deletion syndrome

9q34 deletion syndrome, also known as Kleefstra syndrome, is a rare genetic disorder. Terminal deletions of chromosome 9q34 have been associated with childhood hypotonia, a distinctive facial appearance and developmental disability. The facial features typically described include arched eyebrows, small head circumference, midface hypoplasia, prominent jaw and a pouting lower lip. Individuals with this disease may often have speech impediments, such as speech delays. Other characteristics of this disease include: epilepsy, congenital and urogenital defects, microcephaly, corpulence, and psychiatric disorders. From analysis of chromosomal breakpoints, as well as gene sequencing in suggestive cases, Kleefstra and colleagues identified EHMT1 as the causative gene.

This gene is responsible for producing the protein Histone methyltransferase which functions to alter histones. Ultimately, histone methyltransferases are important in deactivating certain genes, needed for proper growth and development. Moreover, a frameshift, missense, or nonsense error in the coding sequence of EHMT1 can result in this condition in an individual.

ACADS

Acyl-CoA dehydrogenase, C-2 to C-3 short chain is an enzyme that in humans is encoded by the ACADS gene. This gene encodes a tetrameric mitochondrial flavoprotein, which is a member of the acyl-CoA dehydrogenase family. This enzyme catalyzes the initial step of the mitochondrial fatty acid beta-oxidation pathway. The ACADS gene associated with short-chain acyl-coenzyme A dehydrogenase deficiency.

Allan–Herndon–Dudley syndrome

Allan–Herndon–Dudley syndrome is a rare X-linked inherited disorder of brain development that causes both moderate to severe intellectual disability and problems with speech and movement.Allan–Herndon–Dudley syndrome, which is named eponymously for William Allan, Florence C. Dudley, and C. Nash Herndon, results from a mutation of the thyroid hormone transporter MCT8 (also referred to as SLC16A2). Consequently, thyroid hormones are unable to enter the nervous system, which depends on thyroid signaling for proper function and development.

Ballard Maturational Assessment

The Ballard Maturational Assessment, Ballard Score, or Ballard Scale is a commonly used technique of gestational age assessment. It assigns a score to various criteria, the sum of all of which is then extrapolated to the gestational age of the fetus. These criteria are divided into physical and neurological criteria. This scoring allows for the estimation of age in the range of 26 weeks-44 weeks. The New Ballard Score is an extension of the above to include extremely pre-term babies i.e. up to 20 weeks.

The scoring relies on the intra-uterine changes that the fetus undergoes during its maturation. Whereas the neurological criteria depend mainly upon muscle tone, the physical ones rely on anatomical changes. The neonate (less than 37 weeks of age) is in a state of physiological hypotonia. This tone increases throughout the fetal growth period, meaning a more premature baby would have lesser muscle tone.

It was developed in 1979.

Cerebellar hypoplasia

Cerebellar hypoplasia is characterized by reduced cerebellar volume even though cerebellar shape is (near) normal. It consists of a heterogeneous group of disorder of cerebellar maldevelopment presenting as early onset non progressive ataxia, hypotonia, and motor learning disability. Various causes have been incriminated like hereditary, metabolic, toxic and viral agents. First reported by Crouzon in 1929. In 1940 an unclaimed body came for dissection in London Hospital and was discovered to have no cerebellum. This unique case was appropriately named "human brain without a cerebellum" and was used every year in the Department of Anatomy at Cambridge University in a neuroscience course for medical students.

Congenital myopathy

Congenital myopathy is a very broad term for any muscle disorder present at birth. This defect primarily affects skeletal muscle fibres and causes muscular weakness and/or hypotonia. Congenital myopathies account for one of the top neuromuscular disorders in the world today, comprising approximately 6 in 100,000 live births every year. As a whole, congenital myopathies can be broadly classified as follows:

A distinctive abnormality in skeletal muscle fibres on the cellular level; observable via light microscope

Symptoms of muscle weakness and hypotonia

Is a congenital disorder, meaning it occurs during development and symptoms present themselves at birth or in early life.

Is a genetic disorder.

FG syndrome

FG syndrome (FGS) is a rare genetic syndrome caused by one or more recessive genes located on the X chromosome and causing physical anomalies and developmental delays. FG syndrome was named after the first letters of the surnames of the first patients noted with the disease. First reported by Opitz and Kaveggia in 1974, its major clinical features include intellectual disability, hyperactivity, hypotonia (low muscle tone), and a characteristic facial appearance including macrocephaly (an abnormally large head).

Flunitrazepam

Flunitrazepam, also known as Rohypnol among other names, is an intermediate acting benzodiazepine used in some countries to treat severe insomnia and in fewer, early in anesthesia. As with other hypnotics, flunitrazepam has been advised to be prescribed only on a short-term basis or by those with chronic insomnia on an occasional basis.It was patented in 1962 and came into medical use in 1974. Flunitrazepam has been referred to as a date rape drug, though the percentage of reported rape cases in which it is involved is small.

Guanidinoacetate methyltransferase deficiency

Guanidinoacetate methyltransferase deficiency, is an autosomal recessive cerebral creatine deficiency that primarily affects the nervous system and muscles. It is the first described disorder of creatine metabolism. Clinically, affected individuals often present with hypotonia, seizures and developmental delay. Diagnosis can be suspected on clinical findings, and confirmed by specific biochemical tests, brain magnetic resonance spectroscopy, or genetic testing. Biallelic pathogenic variants in GAMT are the underlying cause of the disorder. After GAMT deficiency is diagnosed, it can be treated by dietary adjustments, including supplementation with creatine. Treatment is highly effective if started early in life, however if it is started late, it cannot reverse brain damage which has already taken place.

Malouf syndrome

Malouf syndrome (also known as "congestive cardiomyopathy-hypergonadotropic hypogonadism syndrome") is a congenital disorder that causes one or more of the following symptoms: mental retardation, ovarian dysgenesis, congestive cardiomyopathy, broad nasal base, blepharoptosis, and bone abnormalities, and occasionally marfanoid habitus (tall stature with long and thin limbs, little subcutaneous fat, arachnodactyly, joint hyperextension, narrow face, small chin, large testes, and hypotonia).This disease is named after J. Malouf, who performed a case study on a family suffering from this disease in 1985.

Michael Urtecho

Wilson Michael Urtecho Medina (born 6 November 1969 in Trujillo, Peru) is a Peruvian politician (National Solidarity) and was a Congressman representing La Libertad. Urtecho was diagnosed with hypotonia as a child and uses a wheelchair.Urtecho holds a Master in Chemical engineering. After his graduation, he started working as head of informatics of the La Libertad regional government and parallel as a consultant for the Institute for Disasters and Environment. In 2003 he changed to the Chavimochic special irrigation project, where he worked as an informatic engineer until his entry into Congress.

In 2000 Urtecho joined the conservative National Renewal party, where he acted as a regional delegate for La Libertad. In 2006 he was elected to Congress for the 2006-2011 term on the joint center-right National Unity list. In March 2010, he left the National Renewal to join the National Solidarity Party (PSN) of Lima's mayor Luis Castañeda. He became the regional political coordinator of that party in La Libertad. Urtecho was re-elected in the 2011 election for another five-year term for the National Solidarity Alliance. While he was in congress he was chairman of the Special Commission for Disability (CODIS).In September 2013, former staff members accused Urtecho of failing to pay them for work they had done. Urtecho stood down from the congressional ethics committee while an investigation was launched. A separate investigation into Urtecho's income commenced shortly after, following allegations of financial irregularities stemming from his personal spending habits. The final report published by the ethics committee called for Urtecho's suspension for illegal embellishment. In December 2013, the Peruvian Congress approved his desafuero and banned him from holding public office for a ten-year period. He was replaced in office by Rosa Núñez.

Mitochondrial DNA depletion syndrome

Mitochondrial DNA depletion syndrome (MDS or MDDS) is any of a group of autosomal recessive disorders that cause a significant drop in mitochondrial DNA in affected tissues. Symptoms can be any combination of myopathic, hepatopathic, or encephalomyopathic. These syndromes affect tissue in the muscle, liver, or both the muscle and brain, respectively. The condition is typically fatal in infancy and early childhood, though some have survived to their teenage years with the myopathic variant and some have survived into adulthood with the SUCLA2 encephalomyopathic variant. There is currently no curative treatment for any form of MDDS, though some preliminary treatments have shown a reduction in symptoms.

Muscle tone

In physiology, medicine, and anatomy, muscle tone (residual muscle tension or tonus) is the continuous and passive partial contraction of the muscles, or the muscle's resistance to passive stretch during resting state. It helps to maintain posture and declines during REM sleep.

Norman–Roberts syndrome

Lissencephaly 2, more commonly called Norman–Roberts syndrome, is a rare form of microlissencephaly caused by a mutation in the RELN gene.A small number of cases have been described. The syndrome was first reported by Margaret Grace Norman and M. Roberts et al. in 1976.Lack of reelin prevents normal layering of the cerebral cortex and disrupts cognitive development. Patients have cerebellar hypoplasia and suffer from congenital lymphedema and hypotonia. The disorder is also associated with myopia, nystagmus and generalized seizures.

Norman–Roberts syndrome is one of two known disorders caused by a disruption of the reelin-signaling pathway. The other is VLDLR-associated cerebellar hypoplasia, which is caused by a mutation in the gene coding for one of the reelin receptors, VLDLR.

Disruption of the RELN gene in human patients is analogous to the malfunctioning RELN gene in the reeler mouse.

Oculocerebrorenal syndrome

Oculocerebrorenal syndrome (also called Lowe syndrome) is a rare X-linked recessive disorder characterized by congenital cataracts, hypotonia, intellectual disability, proximal tubular acidosis, aminoaciduria, and low-molecular-weight proteinuria. Lowe syndrome can be considered a cause of Fanconi syndrome (bicarbonaturia, renal tubular acidosis, potassium loss, and sodium loss).

Qazi–Markouizos syndrome

Qazi–Markouizos syndrome is a rare hereditary condition characterized by non-progressive, congenital hypotonia, severe intellectual disability, an increased proportion of type 2 muscle fibers, which additionally exhibited increased size, as well as dysharmonic skeletal maturation. To date, the molecular mechanism of Qazi–Markouizos syndrome, which is also known as Puerto Rican infant hypotonia syndrome, remains unknown.

Sotos syndrome

Sotos syndrome (cerebral gigantism or Sotos-Dodge syndrome) is a rare genetic disorder characterized by excessive physical growth during the first years of life. Excessive growth often starts in infancy and continues into the early teen years. The disorder may be accompanied by autism, mild intellectual disability, delayed motor, cognitive, and social development, hypotonia (low muscle tone), and speech impairments. Children with Sotos syndrome tend to be large at birth and are often taller, heavier, and have relatively large skulls (macrocephaly) than is normal for their age. Signs of the disorder, which vary among individuals, include a disproportionately large skull with a slightly protrusive forehead, large hands and feet, large mandible, hypertelorism (an abnormally increased distance between the eyes), and downslanting eyes. Clumsiness, an awkward gait, and unusual aggressiveness or irritability may also occur. Although most cases of Sotos syndrome occur sporadically, familial cases have also been reported. It is similar to Weaver syndrome.

Diseases of myoneural junction and muscle / neuromuscular disease (G70–G73, 358–359)
Neuromuscular-
junction disease
Myopathy/
congenital myopathy
Certain conditions originating in the perinatal period / fetal disease (P, 760–779)
Maternal factors and
complications of pregnancy,
labour and delivery
Length of gestation
and fetal growth
Birth trauma
By system
Infectious
Other

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