DO NOT USE FOR CLINICAL PRACTICE
Please use current guidelines available on the UHNM intranet for patient treatment
Please use current guidelines available on the UHNM intranet for patient treatment
RECOGNITION AND ASSESSMENT
Definition
- Subjective decrease in resistance to passive range of movement
- Separate from weakness, which refers to lack of muscle strength
- Important to differentiate between central (upper motor neurone), and peripheral (lower motor neurone) hypotonia – may be a mixed picture. See Table 1
- central hypotonia is most common (70–80%)
- Hypotonia
- relatively common finding in newborn period
- transient in majority of cases
- if severe/persistent investigate further
Symptoms and signs
- Reduced activity/movement
- Reduced level of consciousness/alertness
- High pitched, weak or fatigable cry
- Increased or reduced respiratory effort
- Feeding difficulties/choking/pooling of secretions
- Seizures/abnormal movements
- Note: Look for syndrome associated dysmorphic features
DIFFERENTIAL DIAGNOSIS
- Causes of hypotonia in the newborn baby are numerous, not all are listed here
- Benign congenital hypotonia is a diagnosis of exclusion
Central
- Hypoxic ischaemic encephalopathy (HIE)
- Intracranial haemorrhage
- Structural brain malformation
- Chromosomal abnormalities e.g. trisomy 21, Prader-Willi syndrome
- Congenital infection e.g. TORCH
- Acquired infection e.g. Group B Streptococcus
- Endocrine e.g. congenital hypothyroidism
- Metabolic disorders e.g. acid maltase deficiency (Pompe's disease), carnitine deficiency, muccopolysacharidosis, peroxisome biogenesis disorders e.g. Zellweger syndrome
- Drug effects e.g. benzodiazepines
Peripheral
- Spinal cord e.g. birth trauma (especially breech delivery), syringomyelia
- Anterior horn cell e.g. spinal muscular atrophy (SMA)
- Neuromuscular junction e.g. myasthenia gravis, transitory myasthenia
- Peripheral nerves e.g. hereditary motor and sensory neuropathies e.g. Charcot Marie-Tooth disease
- Muscle disorders e.g. muscular dystrophy, congenital myopathy
HISTORY
Family
- Affected parents/siblings
- Consanguinity
- Previous miscarriage/stillbirth
- Metabolic/genetic disease
- Premature death
Maternal
- Diabetes
- Infection
- Medications
- Myotonic dystrophy
- Myasthenia gravis
Antenatal
- TORCH infections
- Drug/alcohol exposure
- Fetal movements
- Liquor volume
Birth
- Gestational age
- Delivery complications
- Malpresentation
- Instrumental delivery
- APGAR score/resuscitation at birth
- Cord gases
Neonatal
- Respiratory distress
- Feeding issues
- Level of alertness
- Level of spontaneous movement
- Seizures
- Hypoglycaemia
- Weak cry
PHYSICAL EXAMINATION
Mother
- Examine for signs of myotonic dystrophy
Baby
- Full neurological assessment
- Level of alertness
- Abnormal posture
- Degree of hypotonia
- pull to sit – significant head-lag
- scarf sign
- shoulder suspension − ‘slipping through hands’
- ventral suspension
- frog-leg posture
- Asymmetry
- Strength
- Deep tendon reflexes
- Primitive reflexes
- Gag and suck
- Fasciculations (including tongue)
- Abnormal eye movements
- Ptosis
- Cataracts
- Dysmorphic features/abnormal facies
- Respiratory effort
- Hepatosplenomegaly
- Undescended testicles
- Contractures
- Arthrogryposis
Table 1: Summary of typical findings according to cause
Central hypotonia | Peripheral hypotonia | |||
Anterior horn cell | Nerve | Neuromuscular junction | Muscle | |
Normal strength | Generalised weakness | Weakness (distal>proximal) | Weakness, including face/eyes/bulbar | Weakness (proximal>distal), including face, extraocular muscles |
Normal/ increased deep tendon reflexes (DTRs) Clonus |
Decreased/ absent DTRs |
Decreased/ absent DTRs |
Normal DTRs | Decreased DTRs |
+/- Seizures | Fasciculations | +/- Fasciculations | No fasciculations | |
+/- Dysmorphic features, reduced alertness | Often described as alert | +/- Arthrogryposis | +/- Contractures |
© Auckland District Health Board
Babies with profound central hypotonia may have absent deep tendon reflexes; this sign may not reliably rule out a central cause of hypotonia in first few days of life
- Weakness uncommon in central hypotonia – except in acute stages
- points to lower motor neurone disorder
- Clinical findings which may direct to a specific diagnosis:
- hepatosplenomegaly – storage disorders, congenital infections
- hypopigmentation, undescended testes – Prader-Willi syndrome
- hepatomegaly, retinitis pigmentosa – neonatal adrenoleukodystrophy
- renal cysts, high forehead, wide fontanelle – Zellweger syndrome
- congenital cataracts, glaucoma, proteinuria – oculocerebrorenal (Lowe) syndrome
- abnormal odour – metabolic disorders
INVESTIGATIONS
- Guided by detailed history and clinical examination
- If hypotonic with a degree of strength, central cause is most likely
- If hypotonic and weak, peripheral cause is possible. Discuss with neurologist
- Involve relevant specialist team early
Investigation | |
Infection screen |
|
Metabolic screen |
|
Endocrine screen |
|
Genetic screen |
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Other |
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Muscle biopsy may be delayed until aged 6 months, as neonatal results are difficult to interpret
MANAGEMENT
- Specific management determined by individual condition and presentation
- Airway and breathing
- may need resuscitation at birth
- airway positioning/Guedel airway
- intubation and ongoing respiratory support
- suction of respiratory secretions
- Feeding
- specialised bottles/teats
- nasogastric tube feeds
- early speech and language team involvement (where available)
- Skin and developmental care
- regular position changes to avoid pressure sores, reduce risk of contractures and optimise neurodevelopment (see Developmental care guideline)
- Physiotherapy
- refer to neonatal/paediatric physiotherapy (while inpatient)
- physiotherapist will:
- advise on specific handling and positioning to optimise neurodevelopmental outcomes
- assess for symmetry and risk of joint contractures/positional deformity and advise on management
- on discharge refer to community paediatric physiotherapy services
- Early involvement of neurologist, and other specialist teams as indicated