Hypotonia

Hypotonia
ICD-10	P94.2, R27
ICD-9	781.3
DiseasesDB	21417
MedlinePlus	003298
MeSH	D009123

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Synonyms and keywords: Muscle flaccidity; decreased muscle tone; flaccid muscle tone; floppy muscles; low muscle tone; benign congenital hypotonia; congenital hypotonia ; congenital muscle hypotonia ; congenital muscle weakness ; amyotonia congenita ; floppy baby syndrome; infantile hypotonia

Overview

Hypotonia is a condition of abnormally low muscle tone (the amount of tension or resistance to movement 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. 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 to help the person compensate for the neuromuscular disability.

Causes

Some conditions known to cause hypotonia include:

Congenital - i.e. present from birth (including genetic disorders presenting within 6 months)

• Genetic disorders are the most common cause
  • Down's syndrome - most common
  • 3-Methylcrotonyl-CoA carboxylase deficiency
  • Achondroplasia
  • Aicardi syndrome
  • Canavan disease
  • Centronuclear myopathy (including myotubular myopathy)
  • Familial dysautonomia (Riley-Day syndrome)
  • Infantile spinal muscular atrophy such as Werdnig-Hoffman disease
  • Krabbe disease
  • Leigh's disease
  • Marfan's syndrome
  • Menkes syndrome
  • Methylmalonic acidemia
  • Nonketotic hyperglycinemia (NKH) or Glycine encephalopathy (GCE)
  • Prader-Willi syndrome
  • Tay-Sachs disease
  • Trisomy 13
  • 22q13 deletion syndrome
  • FG syndrome

• Developmental disability
  • Cerebellar ataxia (congenital)
  • Dysfunction in Sensory Integration (DSI)
  • Developmental Dyspraxia
  • Hypothyroidism (congenital)
  • Hypotonic Cerebral palsy
  • Teratogenesis from in utero exposure to Benzodiazepines

Acquired - i.e. onset occurs after birth

• Genetic
  • Muscular dystrophy (including Myotonic dystrophy) - most common
  • Metachromatic leukodystrophy

• Infections
  • Encephalitis
  • Guillian-Barre syndrome
  • Infant botulism
  • Meningitis
  • Poliomyelitis
  • Sepsis

• Autoimmunity disorders
  • Myasthenia gravis - most common
  • Abnormal vaccine reaction

• Metabolic disorder
  • Hypervitaminosis
  • Kernicterus
  • Rickets

• 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
  • Hypothyroidism

Causes by Organ System

Cardiovascular	Down's syndrome, Noonan syndrome, Pompe disease, Trisomy E, Williams syndrome, XXXXY syndrome, Ehlers-Danlos syndrome, XXXXX syndrome, Young Simpson syndrome, Plasma membrane carnitine transporter deficiency, Marfan's syndrome
Chemical / poisoning	Mercury, Organophosphates, Tick paralysis
Dermatologic	Griscelli syndrome type 1, Autosomal recessive cutis laxa type 2, Menkes disease, Wrinkly skin syndrome, Pellagra, Pallister-Killian syndrome, Ehlers-Danlos syndrome, Xylosylprotein 4-beta-galactosyltransferase deficiency, Dermatomyositis
Drug Side Effect	Baclofen, Barbiturates, Benzodiazepines, Dantrolene, Diazepam, Flunitrazepam, Flurazepam, Ioxilan,Lorazepam, Medazepam, Midazolam, Nitrazepam, Nordazepam, Oxazepam, Palivizumab, Pergolide, Triazolam, Zopiclone
Ear Nose Throat	Osteogenesis imperfecta, Kabuki syndrome, 1p36 deletion syndrome, 22q13 deletion syndrome, Tay-Sachs disease
Endocrine	Growth harmone deficiency, Hypothyroidism, Pituitary dwarfism, Neonatal adrenoleukodystrophy
Environmental	No underlying causes
Gastroenterologic	Celiac disease, Sandifer syndrome, Galloway-Mowat syndrome, Pompe disease, Trisomy E, Pellagra, Mulibrey nanism syndrome, Zellweger spectrum, Zellweger syndrome , Down's syndrome, Sialidosis
Genetic	17q21.31 deletion syndrome, 1p36 deletion syndrome, Alpers disease, Arakawa's syndrome II, Arylsulphatase A deficiency, Autosomal recessive cutis laxa type 2, Becker's muscular dystrophy, Biotinidase deficiency, Canavan disease, Carbohydrate deficient glycoprotein syndrome type 1a, Central core disease, Centronuclear myopathy, Christianson syndrome, Coffin-Siris syndrome, Congenital fiber-type disproportion myopathy, Congenital muscular dystrophy, Congenital myopathies, Congenital myotonic dystrophy, Cri-du-Chat syndrome, D-2-hydroxyglutarate dehydrogenase deficiency, D-bifunctional Protein Deficiency, De Grouchy Syndrome, Dejerine Sottas syndrome, Dibasic aminoaciduria type 2, Distal Trisomy 10q, Down's syndrome, Duchenne muscular dystrophy, Ehlers-Danlos syndrome, Ethylmalonic encephalopathy, FG syndrome, Fragile X syndrome, Fukuyama congenital muscular dystrophy, Galactose epimerase deficiency, Galloway-Mowat syndrome, Gamma-aminobutyrate transaminase deficiency, Glucose transporter type 1 deficiency, Glycine encephalopathy, Glycogen storage diseases, Hereditary motor-sensory neuropathy, Infantile neuroaxonal dystrophy, Isodicentric 15, Joubert syndrome, Kabuki syndrome, Kennedy disease, Krabbe disease, Leigh's disease, Lesch-Nyhan syndrome, Long chain hydroxyacyl-CoA dehydrogenase deficiency, Lowe syndrome, Malonyl-CoA decarboxylase deficiency, Marfan's syndrome, McArdle disease, MECP2 duplication syndrome, Menkes disease, Methylmalonic acidemia, Mitochondrial DNA depletion syndrome, hepatocerebral form, Mitochondrial encephalomyopathy, Mitochondrial trifunctional protein deficiency, Mucolipidosis IV, Mulibrey nanism syndrome, Muscular dystrophy, Nemaline myopathy, Neonatal adrenoleukodystrophy, Noonan syndrome, Osteogenesis imperfecta, Pallister-Killian syndrome, Paramyotonia congenita, Patau's syndrome, Pelizaeus-Merzbacher disease, Periodic familial paralysis, Pitt-Hopkins syndrome, Plasma membrane carnitine transporter deficiency, Pompe disease, Pontocerebellar hypoplasia type 1, Prader-Willi syndrome, Propionic acidemia, Pyridoxine-dependent epilepsy, Pyruvate carboxylase deficiency, Rett syndrome, Rigid spine muscular dystrophy type 1, Riley-Day syndrome, Robinow syndrome, Salla disease, Short-chain acyl-coenzyme A dehydrogenase deficiency, Sialidosis, Smith-Lemli-Opitz syndrome, Sotos syndrome, Spinal muscular atrophy, Stuve-Weidemann syndrome, Succinic semialdehyde dehydrogenase deficiency, Succinyl-CoA synthetase deficiency, Tay-Sachs disease, Tetrasomy 12p , Tetrasomy 18p, Trisomy E, Urea cycle disorder, Valinemia , Vitamin D dependent rickets type 1, Walker-Warburg syndrome, Werdnig-Hoffman disease, Williams sy, drome, Wolf-Hirschhorn syndrome, Wrinkly skin syndrome, X linked immunoneurologic disorder, XXXX syndrome, XXXXX syndrome, XXXXY syndrome, Xylosylprotein 4-beta-galactosyltransferase deficiency, Young Simpson syndrome, Zellweger spectrum, Zellweger syndrome , Achondroplasia, Carey-Fineman-Ziter syndrome, Adult polyglucosan body disease, Cerebellar hypoplasia, 3-alpha-hydroxyacyl-CoA dehydrogenase deficiency, 3-Methylcrotonyl-CoA carboxylase deficiency, 3-Methylglutaconic aciduria type 4, Barth syndrome, Allan-Herndon-Dudley syndrome, Griscelli syndrome type 1, 22q13 deletion syndrome
Hematologic	No underlying causes
Iatrogenic	Abnormal vaccine reaction
Infectious Disease	Infantile botulism, Intracranial abscess, Meningitis, Poliomyelitis, Sepsis, Encephalitis
Musculoskeletal / Ortho	22q13 deletion syndrome, Achondroplasia, Acute intervertebral disc herniation, Arthrogryposis , Benign congenital hypotonia, Carey-Fineman-Ziter syndrome, Congenital myasthenic syndromes, Dermatomyositis, Familial infantile myasthenia, Inclusion body myositis, Polymyositis, Transient neonatal myasthenia, 17q21.31 deletion syndrome, Arylsulphatase A deficiency, Becker's muscular dystrophy, Central core disease, Centronuclear myopathy, Coffin-Siris syndrome, Congenital fiber-type disproportion myopathy, Congenital myopathies, Congenital myotonic dystrophy, Cri-du-Chat syndrome, D-2-hydroxyglutarate dehydrogenase deficiency, Down syndrome, Duchenne muscular dystrophy, Ehlers-Danlos syndrome, Fukuyama congenital muscular dystrophy, Isodicentric 15, Kabuki syndrome, Kennedy disease, Marfan's syndrome, Mulibrey nanism syndrome, Muscular dystrophy, Nemaline myopathy, Paramyotonia congenita, Periodic familial paralysis, Prader-Willi syndrome, Rigid spine muscular dystrophy type 1, Robinow syndrome, Smith-Lemli-Opitz syndrome, Sotos syndrome, Spinal muscular atrophy, Stuve-Weidemann syndrome, Walker-Warburg syndrome, Werdnig-Hoffman disease, Williams syndrome, Wolf-Hirschhorn syndrome, XXXXY syndrome, Allan-Herndon-Dudley syndrome, Motor neuron disease, Myasthenia gravis, Autosomal recessive cutis laxa type 2, Menkes disease, Wrinkly skin syndrome, Galloway-Mowat syndrome, Christianson syndrome, Congenital muscular dystrophy, Dejerine Sottas syndrome, FG syndrome, Fragile X syndrome, Joubert syndrome, Patau's syndrome, Pontocerebellar hypoplasia type 1, Succinic semialdehyde dehydrogenase deficiency, Succinyl-CoA synthetase deficiency, XXXXX syndrome, Young Simpson syndrome, Mitochondrial encephalomyopathy, Plasma membrane carnitine transporter deficiency, Pallister-Killian syndrome, Xylosylprotein 4-beta-galactosyltransferase deficiency, Pompe disease, Trisomy E, Noonan syndrome, Osteogenesis imperfecta, Pitt-Hopkins syndrome, 1p36 deletion syndrome
Neurologic	Acute spinal cord injury, Adult polyglucosan body disease, Agenesis of the corpus callosum, Aicardi syndrome, Allan-Herndon-Dudley syndrome, Bell's palsy, Brain damage due to birth trauma, Bulbar palsy, Cerebellar ataxia, Cerebellar hypoplasia, Cerebellar syndrome, Cerebral malformations, Cerebral palsy, Cervical myelopathy, Chronic inflammatory demyelinating polyneuropathy, Encephalitis, Encephalocele, Friedreich ataxia, Glue-sniffing neuropathy, Intracranial tumor, Kernicterus, Miller Fisher syndrome, Motor neuron disease, Myasthenia gravis, Paresis, Peripheral neuropathy, Porencephaly, Postpoliomyelitis syndrome, Schizencephaly, Sensory integration dysfunction, Spinal cord tumor, Sydenham's chorea, Syringomyelia, Transverse myelitis, Griscelli syndrome type 1, Sandifer syndrome, 1p36 deletion syndrome, Alpers disease, Arakawa's syndrome II, Canavan disease, Christianson syndrome, Congenital muscular dystrophy, Dejerine Sottas syndrome, Distal Trisomy 10q, FG syndrome, Fragile X syndrome, Gamma-aminobutyrate transaminase deficiency, Glucose transporter type 1 deficiency, Hereditary motor-sensory neuropathy, Infantile neuroaxonal dystrophy, Joubert syndrome, Leigh's disease, MECP2 duplication syndrome, Neonatal adrenoleukodystrophy, Pallister-Killian syndrome, Patau's syndrome, Pelizaeus-Merzbacher disease, Pitt-Hopkins syndrome, Pontocerebellar hypoplasia type 1, Pyridoxine-dependent epilepsy, Rett syndrome, Riley-Day syndrome, Salla disease, Succinic semialdehyde dehydrogenase deficiency, Succinyl-CoA synthetase deficiency, XXXXX syndrome, Xylosylprotein 4-beta-galactosyltransferase deficiency, Young Simpson syndrome, Zellweger spectrum, Zellweger syndrome , Intracranial abscess, Meningitis, Poliomyelitis, Acute intervertebral disc herniation, Congenital myasthenic syndromes, Familial infantile myasthenia, Transient neonatal myasthenia, Subacute combined degeneration of the cord, Hypoxic ischemic encephalopathy, Guillain-Barre syndrome, Traumatic brain injury, Noonan syndrome, Arylsulphatase A deficiency, Cri-du-Chat syndrome, D-2-hydroxyglutarate dehydrogenase deficiency, Isodicentric 15, Robinow syndrome, Smith-Lemli-Opitz syndrome, Sotos syndrome, Spinal muscular atrophy, Walker-Warburg syndrome, Wolf-Hirschhorn syndrome, Glycine encephalopathy, Lowe syndrome, X linked immunoneurologic disorder, Pellagra, Mulibrey nanism syndrome, Menkes disease, Mitochondrial encephalomyopathy, Long chain hydroxyacyl-CoA dehydrogenase deficiency, Mucolipidosis IV, Tay-Sachs disease, Prader-Willi syndrome, Sialidosis
Nutritional / Metabolic	3-alpha-hydroxyacyl-CoA dehydrogenase deficiency, 3-Methylcrotonyl-CoA carboxylase deficiency, 3-Methylglutaconic aciduria type 4, Barth syndrome, Gangliosidosis, Hypercalcemia, Hypermagnesemia, Hypervitaminosis, Hypoglycemia, Pellagra, Rickets, Subacute combined degeneration of the cord, Biotinidase deficiency, Carbohydrate deficient glycoprotein syndrome type 1a, D-bifunctional Protein Deficiency, Dibasic aminoaciduria type 2, Ethylmalonic encephalopathy, Galactose epimerase deficiency, Glycine encephalopathy, Glycogen storage diseases, Krabbe disease, Lesch-Nyhan syndrome, Long chain hydroxyacyl-CoA dehydrogenase deficiency, Malonyl-CoA decarboxylase deficiency, McArdle disease, Methylmalonic acidemia, Mitochondrial DNA depletion syndrome, hepatocerebral form, Mitochondrial encephalomyopathy, Mitochondrial trifunctional protein deficiency, Mucolipidosis IV, Plasma membrane carnitine transporter deficiency, Propionic acidemia, Pyruvate carboxylase deficiency, Short-chain acyl-coenzyme A dehydrogenase deficiency, Sialidosis, Tay-Sachs disease, Urea cycle disorder, Valinemia , Vitamin D dependent rickets type 1, Arakawa's syndrome II, Gamma-aminobutyrate transaminase deficiency, Glucose transporter type 1 deficiency, Williams syndrome, Succinic semialdehyde dehydrogenase deficiency, Succinyl-CoA synthetase deficiency, Pellagra
Obstetric/Gynecologic	Maternal drug use , Premature babies, Teratogenecity from inutero exposure to barbiturates, Teratogenecity from inutero exposure to benzodiazepines, Teratogenecity from inutero exposure to chlordiazepoxide, Teratogenecity from inutero exposure to chloroquine, Teratogenecity from inutero exposure to drugs, Brain damage due to birth trauma
Oncologic	Intracranial tumor, Spinal cord tumor
Opthalmologic	Lowe syndrome, 22q13 deletion syndrome, Aicardi syndrome, Osteogenesis imperfecta, Marfan's syndrome, Long chain hydroxyacyl-CoA dehydrogenase deficiency, Mucolipidosis IV, Sialidosis, Tay-Sachs disease, 1p36 deletion syndrome, Walker-Warburg syndrome, Mulibrey nanism syndrome
Overdose / Toxicity	Barbiturates, Benzodiazepines, Dantrolene, Diazepam, Flunitrazepam, Flurazepam, Lorazepam, Medazepam, Midazolam, Nitrazepam, Nordazepam, Oxazepam, Triazolam, Zopiclone, Hypervitaminosis
Psychiatric	Kabuki syndrome, 22q13 deletion syndrome, FG syndrome, Arylsulphatase A deficiency, Cri-du-Chat syndrome, Isodicentric 15, Smith-Lemli-Opitz syndrome, Sotos syndrome, Prader-Willi syndrome
Pulmonary	Hypoxic ischemic encephalopathy, Pitt-Hopkins syndrome, XXXXX syndrome
Renal / Electrolyte	Galloway-Mowat syndrome, Patau's syndrome, Lowe syndrome, Trisomy E
Rheum / Immune / Allergy	Guillain-Barre syndrome, Celiac disease, X linked immunoneurologic disorder, Dermatomyositis, Inclusion body myositis, Polymyositis, Chronic inflammatory demyelinating polyneuropathy, Miller Fisher syndrome, Sydenham's chorea, Transverse myelitis
Sexual	Fragile X syndrome
Trauma	Traumatic brain injury, Acute spinal cord injury
Urologic	No underlying causes
Dental	No underlying causes
Miscellaneous	Premature babies

Causes in Alphabetical Order

17q21.31 deletion syndrome 1p36 deletion syndrome 22q13 deletion syndrome 3-alpha-hydroxyacyl-CoA dehydrogenase deficiency 3-Methylcrotonyl-CoA carboxylase deficiency 3-Methylglutaconic aciduria type 4 Abnormal vaccine reaction Achondroplasia Acute intervertebral disc herniation Acute spinal cord injury Adult polyglucosan body disease Agenesis of the corpus callosum Aicardi syndrome Allan-Herndon-Dudley syndrome Alpers disease Arakawa's syndrome II Arthrogryposis Arylsulphatase A deficiency Autosomal recessive cutis laxa type 2 Baclofen Barbiturate withdrawl Barth syndrome Becker's muscular dystrophy Bell's palsy Benign congenital hypotonia Benzodiazepine Biotinidase deficiency Brain damage due to birth trauma Bulbar palsy Canavan disease Carbohydrate deficient glycoprotein syndrome type 1a Carey-Fineman-Ziter syndrome Celiac disease Central core disease Centronuclear myopathy Cerebellar ataxia Cerebellar hypoplasia Cerebellar syndrome Cerebral malformations Cerebral palsy Cervical myelopathy Christianson syndrome Chronic inflammatory demyelinating polyneuropathy Coffin-Siris syndrome Congenital fiber-type disproportion myopathy Congenital muscular dystrophy Congenital myasthenic syndromes Congenital myopathies Congenital myotonic dystrophy Cri-du-Chat syndrome D-2-hydroxyglutarate dehydrogenase deficiency Dantrolene D-bifunctional Protein Deficiency De Grouchy Syndrome Dejerine Sottas syndrome Dermatomyositis Diazepam Dibasic aminoaciduria type 2 Distal Trisomy 10q Down's syndrome Duchenne muscular dystrophy Ehlers-Danlos syndrome Encephalitis Encephalocele Ethylmalonic encephalopathy Familial infantile myasthenia FG syndrome Flunitrazepam Flurazepam Fragile X syndrome

Friedreich ataxia Fukuyama congenital muscular dystrophy Galactose epimerase deficiency Galloway-Mowat syndrome Gamma-aminobutyrate transaminase deficiency Gangliosidosis Glucose transporter type 1 deficiency Glue-sniffing neuropathy Glycine encephalopathy Glycogen storage diseases Griscelli syndrome type 1 Growth harmone deficiency Guillain-Barre syndrome Hereditary motor-sensory neuropathy Hypercalcemia Hypermagnesemia Hypervitaminosis Hypoglycemia Hypothyroidism Hypoxic ischemic encephalopathy Inclusion body myositis Infantile botulism Infantile neuroaxonal dystrophy Intracranial abscess Intracranial tumor Isodicentric 15 Joubert syndrome Kabuki syndrome Kennedy disease Kernicterus Krabbe disease Leigh's disease Lesch-Nyhan syndrome Long chain hydroxyacyl-CoA dehydrogenase deficiency Lorazepam Lowe syndrome Malonyl-CoA decarboxylase deficiency Marfan's syndrome Maternal drug use McArdle disease MECP2 duplication syndrome Medazepam Meningitis Menkes disease Mercury Methylmalonic acidemia Midazolam Miller Fisher syndrome Mitochondrial DNA depletion syndrome, hepatocerebral form Mitochondrial encephalomyopathy Mitochondrial trifunctional protein deficiency Motor neuron disease Mucolipidosis IV Mulibrey nanism syndrome Muscular dystrophy Myasthenia gravis Nemaline myopathy Neonatal adrenoleukodystrophy Nitrazepam Noonan syndrome Nordazepam Organophosphates Osteogenesis imperfecta Oxazepam Pallister-Killian syndrome Paramyotonia congenita Paresis Patau's syndrome Pelizaeus-Merzbacher disease Pellagra

Pergolide Periodic familial paralysis Peripheral neuropathy Pitt-Hopkins syndrome Pituitary dwarfism Plasma membrane carnitine transporter deficiency Pneumococcal Vaccine 13-Valent (Prevnar 13): in infants and toddlers Poliomyelitis Polymyositis Pompe disease Pontocerebellar hypoplasia type 1 Porencephaly Postpoliomyelitis syndrome Prader-Willi syndrome Premature babies Propionic acidemia Pyridoxine-dependent epilepsy Pyruvate carboxylase deficiency Rett syndrome Rickets Rigid spine muscular dystrophy type 1 Riley-Day syndrome Robinow syndrome Salla disease Sandifer syndrome Schizencephaly Sensory integration dysfunction Sepsis Short-chain acyl-coenzyme A dehydrogenase deficiency Sialidosis Smith-Lemli-Opitz syndrome Sotos syndrome Spinal cord tumor Spinal muscular atrophy Stuve-Weidemann syndrome Subacute combined degeneration of the cord Succinic semialdehyde dehydrogenase deficiency Succinyl-CoA synthetase deficiency Sydenham's chorea Syringomyelia Tay-Sachs disease Teratogenecity from inutero exposure to barbiturates Teratogenecity from inutero exposure to benzodiazepines Teratogenecity from inutero exposure to chlordiazepoxide Teratogenecity from inutero exposure to chloroquine Teratogenecity from inutero exposure to drugs Tetrasomy 12p Tetrasomy 18p Tick paralysis Transient neonatal myasthenia Transverse myelitis Traumatic brain injury Triazolam Trisomy E Urea cycle disorder Valinemia Vitamin D dependent rickets type 1 Walker-Warburg syndrome Werdnig-Hoffman disease Williams syndrome Wolf-Hirschhorn syndrome Wrinkly skin syndrome X linked immunoneurologic disorder XXXX syndrome XXXXX syndrome XXXXY syndrome Xylosylprotein 4-beta-galactosyltransferase deficiency Young Simpson syndrome Zellweger spectrum Zellweger syndrome Zopiclone

Signs and objective manifestations

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 and motivation. 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 hypotonics may experience constipation, while others have no bowel problems.

Since hypotonia is most often diagnosed during infancy, it is also known as "floppy infant syndrome" or "infantile hypotonia." Infants who suffer from hypotonia are often described as feeling and appearing as though they are "rag dolls" or a "sack of jello," easily slipping through one's hands. This image demonstrates the floppiness of a hypotonic infant. 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 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 mental retardation, that may be associated with the cause of hypotonia.

Muscle tone vs. muscle strength

The low muscle tone associated with hypotonia must not be confused with low muscle strength. In body building, good muscle tone is equated with good physical condition, with taut muscles, and a lean appearance, whereas an out-of-shape, overweight individual with fleshy muscles is said to have "poor tone." Neurologically, however, muscle tone cannot be changed under voluntary control, regardless of exercise and diet.

In an article by Diane E Gagnon, M.Ed., PT, she explains

"True muscle tone is the inherent ability of the muscle to respond to a stretch. For example, if you quickly straighten the flexed elbow of an unsuspecting child with normal tone, the biceps will quickly contract in response (automatic protection against possible injury). When the perceived danger has passed, which the brain figures out really quickly once the stimulus is removed, the muscle then 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 realising their full potential of maintaining a muscle contraction over time. "

Diagnosis

"A diagnosis of hypotonia is sometimes considered a form of muscular dystrophy or cerebral palsy, depending on the symptoms and the doctor. If the cause of the hypotonia is thought to lie in the brain, then it might be classified as a cerebral palsy. If the cause seems to be in the muscles, it might be classified as a muscular dystrophy, even though most forms of hypotonia are not seriously dystrophic. If the cause is thought to be in the nerves, it could be classified as either or neither. In any case, hypotonia is rarely an actual muscular dystrophy or cerebral palsy, and is often not classified as either one, or anything at all for that matter."

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.

Differential diagnosis

Diseases	History and Physical								Diagnostic tests		Other Findings
	Motor Deficit	Sensory deficit	Cranial nerve Involvement	Autonomic dysfunction	Proximal/Distal/Generalized	Ascending/Descending/Systemic	Unilateral (UL) or Bilateral (BL) or No Lateralization (NL)	Onset	Lab or Imaging Findings	Specific test
Adult Botulism	+	-	+	+	Generalized	Descending	BL	Sudden	Toxin test	Blood, Wound, or Stool culture	Diplopia, Hyporeflexia, Hypotonia, possible respiratory paralysis
Infant Botulism	+	-	+	+	Generalized	Descending	BL	Sudden	Toxin test	Blood, Wound, or Stool culture	Flaccid paralysis (Floppy baby syndrome), possible respiratory paralysis
Guillian-Barre syndrome	+	-	-	-	Generalized	Ascending	BL	Insidious	CSF: ↑Protein ↓Cells	Clinical & Lumbar Puncture	Progressive ascending paralysis following infection, possible respiratory paralysis
Eaton Lambert syndrome	+	-	+	+	Generalized	Systemic	BL	Intermittent	EMG, repetitive nerve stimulation test (RNS)	Voltage gated calcium channel (VGCC) antibody	Diplopia, ptosis, improves with movement (as the day progresses)
Myasthenia gravis	+	-	+	+	Generalized	Systemic	BL	Intermittent	EMG, Edrophonium test	Ach receptor antibody	Diplopia, ptosis, worsening with movement (as the day progresses)
Electrolyte disturbance	+	+	-	-	Generalized	Systemic	BL	Insidious	Electrolyte panel	↓Ca++, ↓Mg++, ↓K+	Possible arrhythmia
Organophosphate toxicity	+	+	-	+	Generalized	Ascending	BL	Sudden	Clinical diagnosis: physical exam & history	Clinical suspicion confirmed with RBC AchE activity	History of exposure to insecticide or living in farming environment. with : Diarrhea, Urination, Miosis, Bradycardia, Lacrimation, Emesis, Salivation, Sweating
Tick paralysis (Dermacentor tick)	+	-	-	-	Generalized	Ascending	BL	Insidious	Clinical diagnosis: physical exam & history	-	History of outdoor activity in Northeastern United States. The tick is often still latched to the patient at presentation (often in head and neck area)
Tetrodotoxin poisoning	+	-	+	+	Generalized	Systemic	BL	Sudden	Clinical diagnosis: physical exam & dietary history	-	History of consumption of puffer fish species.
Stroke	+/-	+/-	+/-	+/-	Generalized	Systemic	UL	Sudden	MRI +ve for ischemia or hemorrhage	MRI	Sudden unilateral motor and sensory deficit in a patient with a history of atherosclerotic risk factors (diabetes, hypertension, smoking) or atrial fibrillation.
Poliomyelitis	+	+	+	+/-	Proximal > Distal	Systemic	BL or UL	Sudden		PCR of CSF	Asymmetric paralysis following a flu-like syndrome.
Transverse myelitis	+	+	+	+	Proximal > Distal	Systemic	BL or UL	Sudden	MRI & Lumbar puncture	MRI	History of chronic viral or autoimmune disease (e.g. HIV)
Neurosyphilis	+	+	-	+/-	Generalized	Systemic	BL	Insidious	MRI & Lumbar puncture	CSF VDRL-specifc CSF FTA-Ab -sensitive	History of unprotected sex or multiple sexual partners. History of genital ulcer (chancre), diffuse maculopapular rash.
Muscular dystrophy	+	-	-	-	Proximal > Distal	Systemic	BL	Insidious	Genetic testing	Muscle biopsy	Progressive proximal lower limb weakness with calf pseudohypertrophy in early childhood. Gower sign positive.
Multiple sclerosis exacerbation	+	+	+	+	Generalized	Systemic	NL	Sudden	↑CSF IgG levels (monoclonal)	Clinical assessment and MRI	Blurry vision, urinary incontinence, fatigue
Amyotrophic lateral sclerosis	+	-	-	-	Generalized	Systemic	BL	Insidious	Normal LP (to rule out DDx)	MRI & LP	Patient initially presents with upper motor neuron deficit (spasticity) followed by lower motor neuron deficit (flaccidity).
Inflammatory myopathy	+	-	-	-	Proximal > Distal	Systemic	UL or BL	Insidious	Elevated CK & Aldolase	Muscle biopsy	Progressive proximal muscle weakness in 3rd to 5th decade of life. With or without skin manifestations.

Prognosis and treatment

There is currently no known treatment or cure for most (or perhaps all) causes of hypotonia, and objective manifestations can be life long. 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 him 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 and 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).

For most hypotonics, the National Institute of Health recommends "physical therapy [to] improve motor control and overall body strength. Occupational therapy to assist with fine motor skill development and hand control, and speech-language therapy can help breathing, speech, and swallowing difficulties. Therapy for infants and young children may also include sensory stimulation programs." Ankle/foot orthoses are sometimes used for weak ankle muscles. Toddlers and children with speech difficulties may benefit greatly by using sign language.

Breastfeeding

Low-tone infants often have difficulty feeding, especially coordinating the suck-swallow reflex required for proper breastfeeding. Early diagnosis of hypotonic newborns can help mothers find the support and information they need to establish a successful breastfeeding relationship. Hypotonic babies may take longer to breastfeed because of the poor timing of sucking bursts and the need for long rests. If feeding is inefficient, they will also require greater feeding frequency. A baby with low muscle tone may suck better when the head and bottom are level, indicating pillow support in the lap. If the infant tends to arch his back, it may be helpful to swaddle the child loosely with arms drawn across the chest and legs drawn up toward the belly with a rounded spine during feedings. It may be necessary to support the infant's chin with one's hand if jaw, ear, and temple movement are not observed. If the baby tolerates touch to the mouth and face, the mother might gently rub the baby's lips and the outer surface of the gums to stimulate muscle sensitivity before beginning feeding. "If the tongue does not have the tone, strength, or range of motion to lift and press the breast against the palate (roof of the mouth), the baby might compensate by pressing more with his jaws. This excessive compression is painful for the mother. Getting a deeper latch, making sure the baby is not tongue-tied, and using an asymmetrical latch to increase the amount of tongue in contact with the breast can all be helpful to reduce compression." Finally, if nursing is too frustrating and stressful for mother and child, breast milk can be expressed by use of a breast pump and fed through a bottle.

Positions which allow for better drainage of the breast through the help of gravity or manual expressing/massage while the baby is nursing may improve milk intake at the breast. Proper latch can be taught/encouraged by reinforcing appropriate mouth/tongue movements with massage of the breast to increase flow. Taking extra time with feeds is helpful. Many low-tone babies have a hard time with the coordination of sucking, swallowing and breathing and taking frequent short breaks may be helpful.

Exclusive feeding of breastmilk, especially for infants who have frequent bouts of gagging due to poor coordination, can be helpful in avoiding some of the sequelae of aspiration of formula. Breastmilk is less irritating to the lungs and less likely to cause infection if aspirated. When weighing the benefits vs. risks of formula supplementation to encourage weight gain, the possibility of aspiration should be considered. It may be better to have a little slower gain and avoid the risk of non-breastmilk fluids being aspirated.

Related Chapters

• Hypertonia
• Atonia

Additional Resources

• Template:NINDS

External links

Support organizations

• National Rehabilitation Information Center (NRIC)
• Muscular Dystrophy Association (MDA)
• American Coalition of Citizens with Disabilities (ACCD)
• National Multiple Sclerosis Society (NMSS)
• March of Dimes Birth Defects Foundation

Online message boards

• Hypotonia Hope
• Children With Hypotonia
• ParentsPlace Hypotonia Message Board

Template:Certain conditions originating in the perinatal period