pediatric resident

1. APPROACH TO HYPOTONIC INFANT
BY :DR.TADELE T
Moderator – DR AYALEW (Pediatrician and Pediatric neurologist⁾
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2. OUTLINE
Introduction
Approach to patient
Investigations
Summary
Reference
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3. INTRODUCTION
Muscle tone is defined as a skeletal muscle’s inherent resistance to
passive movement.
 It is particularly important to differentiate this from muscle strength,
which is a muscle’s maximum voluntary resistance to movement.
 Tone is controlled by the peripheral fusimotor system with input from
the central nervous system (CNS).
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4. Cont…
Failure of any component of the motor unit, from the anterior horn
cell, motor neuron, neuromuscular junction, or the muscle itself, will
result in hypotonia.
Supraspinal input from the motor cortex, basal ganglia, striatum, red
nucleus, and cerebellum is predominantly inhibitory in its interaction
with fusimotor system.
In older children and adults, disturbance of inhibitory pathways results
in increased excitatory output with hypertonia and hyperreflexia.
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5. Cont….
In contrast, disturbance to these pathways in infancy often presents
with decreased muscle tone; but importantly, the reflex arc is the
preserved.
Therefore, hypotonia in infancy may be caused by disorders affecting
any level of the nervous system.
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6. Cont….
The floppy infant is an informal term for generalized hypotonia and is
a presenting feature for a wide range of both systemic and neurologic
disease.
Although at present most of the conditions have few disease
modifying treatments, diagnosis is essential as:
It provides both families and physicians with prognostic information and
screening strategies for associated pathologies.
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7. Cont….
Severe hypotonia usually presents in the neonatal period.
But milder or slowly progressive pathologies may not come to a
physician’s attention until the child fails to attain milestones in the
latter part of the first or second years.
The first step in the determination of the cause of hypotonia is to
localize the pathology.
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8. LOCALIZATION OF HYPOTONIA
CENTRAL
PERIPHERAL
COMBINED
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9. CENTRAL HYPOTONIA
Conditions that affect the central nervous system, and therefore
supraspinal pathways.
Hypotonia in the absence of weakness is suggestive of disorders
affecting the central nervous system.
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10. Cont….
May present with other findings suggesting disorders involving the
CNS:
Dysmorphic features
 Decreased level of consciousness
 Seizures
 May have evidence of brisk reflexes and clonus
 History of developmental delay affecting both cognitive and
motor domains
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11. Cont…
Fisting of the hand
Abnormal eye movement
Axial motor are more affected
Account for about 70% of cases
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12. Cont….
The findings should prompt consideration of a syndromic diagnosis or
chromosomal abnormalities, and involvement of a geneticist include:
 Multiple congenital abnormalities
 Dysmorphic facial features
Delay in cognitive milestones
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13. Cont…
Both sepsis and severe congenital heart disease can cause a picture of
central hypotonia.
Hypoxicischemic injury accounts for approximately one-third of
infants with hypotonia.
Intraventricular hemorrhage accounts for a significant proportion of
preterm neonates with hypotonia.
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14. Cont…
The approach to an infant with central hypotonia should be directed at
identifying the most life-threatening and actionable diagnoses first
with consideration of the most common etiologies next.
It is therefore imperative that the general health of the infant be a part
of the initial assessment.
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15. Causes of central hypotonia
CEREBRAL HYPOTONIA
Benign congenital hypotonia
CHRONIC NONPROGRESSIVE ENCEPHALOPATHY
CEREBRAL MALFORMATION
Perinatal distress
Postnatal disorders
Peroxisomal disorders
Cerebrohepatorenal syndrome
Neonatal adrenoleukodystrophy
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16. Cont….
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17. PERIPHERAL HYPOTONIA
Hypotonia with weakness suggest disorder affecting lower motor
neuron .
Patient alert, with no signs of CNS involvement
Motor development may be delayed
Less common than central hypotonia
Weakness is proximal and more profound
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18. Cont….
Clinical features of an infant that presents with pathology affecting the
motor neuron unit
 Have a paucity of antigravity movements
 May have myopathic facies .
Generally alert and reach cognitive milestones appropriately.
Fasciculation
Muscle atrophy
Diminished reflexes are characteristic
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19. Cont…
Most common causes are;
 SMA
 Myotonic dystrophy
 Congenital myopathy
 Congenital myastenic syndrome
 Carnitine deficiency
 Pompe disease
 Barth syndrome
 Polyneuropathy
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20. Cont….
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21. COMBINED HYPOTONIA
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22. Causes of peripheral hypotonia
SPINAL CORD DISORDERS
Spinal muscular atrophies
Infantile neuronal degeneration
Neurogenic arthrogryposis
DISORDERS OF NEUROMUSCULAR TRANSMISSION
Familial infantile myasthenia
Infantile botulism
Transitory myasthenia gravis
Myotubular (centronuclear) myopathy
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23. Cont….
MUSCULAR DYSTROPHIES
Congenital dystrophinopathy
Congenital muscular dystrophy
Congenital myotonic dystrophy
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24. Difference between peripheral and central hypotonia
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25. Approach to patient
History
Physical examination
Investigation
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26. Cont….
History
Key components of the clinical history and examination;
Confirm the presence of hypotonia.
Localizes its origins.
Narrows the differential diagnosis.
A careful and complete history is essential
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27. Cont…
The pregnancy history
History of maternal illnesses ,exposure to medications .
Results of antenatal ultrasounds, specifically polyhydramnios.
paucity of fetal movements
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28. Cont….
Delivery history may uncover risk factors for hypoxicischemic injury
(HIE), such as maternal hypotension, breech extraction, cord
prolapse, or placental abruption.
Onset and progression of the hypotonia should be elucidated.
Central hypotonia tends to improve with time, whereas peripheral
hypotonia remains stable or progresses gradually.
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29. Cont….
Rapid progression after an uncomplicated pregnancy, delivery and
neonatal course suggests an inborn error of metabolism.
Infantile botulism may also present with progressive weakness and
history of constipation, after an otherwise unremarkable neonatal
course.
Fluctuation in symptoms may be seen with congenital myasthenia
syndromes or in LAMA2-related muscular dystrophy.
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30. Cont….
A feeding history may also be reveal bulbar dysfunction, resulting in
choking or aspiration often seen.
Fatigue with feeding may be observed with myasthenic syndromes.
Seizures have been traditionally associated with central causes,
although have been reported in peripheral disorders particularly in
LAMA2-related muscular dystrophies.
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31. Cont…
Developmental history should be obtained if the infant is of an
appropriate age.
Motor delay will often result secondary to the hypotonia, but cognitive
delay is more common with central causes and myotonic dystrophy.
Weak cry is also a consequence of respiratory
muscle weakness, although high pitched or unusual cries are more in
keeping with central etiologies.
 A fatigable cry is associated with myasthenia.
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32. Cont….
A detailed family history is essential.
Ethnicities Ashkenazi Jewshigh carrier rate for familial dysautonomia and
Canavan disease.
Presence of consanguinity-Inborn errors of metabolism
Maternal history of recurrent miscarriage-syndromes
History of malignant hyperthermiaa -congenital myopathy
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33. Physical examination
The assumption of unusual postures by the hypotonic infant is often
the first indication of decreased tone.
 Instead of the contracted posture of a healthy term infant, infants with
hypotonia typically have flaccid extension of the arms and abduction
of the legs of described as “frog-leg.”
 There are several maneuvers that are particularity useful for assessing
tone in infants.
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34. Cont….
The pull-to-sit (or traction)
 Used to assess both axial tone and upper limb weakness.
The supine infant is pulled by the hands to the sitting position with the
examiner observing for head lag.
Term neonates, until about 2 months, should have only mild head-lag
Infants usually resist this movement with flexion at the shoulder and elbow;
this also gives the examiner an opportunity to assess strength in the upper
limb
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35. Cont….
The scarf-sign
provides a measure of appendicular tone in the upper limb.
To elicit this sign the supine infant’s hand is pulled toward the opposite
shoulder and around the neck.
The sign is positive for hypotonia if the elbow can be pulled across the
midline.
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36. Cont….
Measurement of the popliteal angle
Is a more objective way to measure tone in the lower limb.
 In the supine position, the infant’s hip is flexed to the torso and the knee
extended as far as possible.
The angle between the thigh and the leg is the popliteal angle and should be
less than 90 degrees in the term infant
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37. Cont….
Shoulder suspension (vertical suspension)
The infant is held under the shoulders in the vertical position assesses
appendicular tone.
 A term neonate resists falling through the hands of the examiner.
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38. Cont….
ventral suspension
The examiner holds the infant by the torso in a supine position.
 An infant with adequate tone is able to maintain both upper and lower limbs
in flexed posture and, at least transiently, be able to hold their head higher than
the horizontal
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39. Cont….
Particular attention should be placed on examining the infant’s facial
features.
Joint contractures may also be observed in the context of weakness
secondary to prolonged periods of decreased movement.
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40. Cont…
Reflexes are often unreliable in the newborn period, as they are often
brisk or may be normally absent
Clonus, if present, may indicate an upper motor neuron lesion, but it
must be kept in mind that up to six beats of clonus may be normal in
neonates.
Severe weakness that impairs an infant’s spontaneous antigravity
movement and appropriate withdrawal response is most likely
secondary to a peripheral pathology.
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41. Cont…
The presence or absence of weakness is the most reliable
distinguishing feature between central and peripheral causes.
Axial hypotonia with the relative preservation of peripheral tone
should prompt consideration of metabolic disease.
This particular pattern is also seen in the LMNA1 congenital muscular
dystrophy and SPEN1-congenital myopathy.
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42. Cont…..
Some features when present are highly suggestive of specific
diagnosis
Tongue fasciculation –anterior horn cell disease
Joint hypermobility
-connective tissue disease
-college VI related CMD
 Cardiac involvement
-metabolic myopathies
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43. INVESTIGATION
CK
Raised suggest hypotonia of peripheral origin
Most marked elevation in patients with congenital muscular
dystrophy
 May be normal in all forms of peripheral pathologies
EMG and NCs
May identify slowed conduction velocity
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44. Cont….
All infants presenting with hypotonia should have a CK level
measured
Magnetic resonance imaging of the brain should be obtained to
identify structural abnormalities
Additional investigations based on the history and examination.
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46. Cont….
Information from clinical presentation, family history, investigation
results helps to prioritization of genetic testing.
Arrange for genetic testing if there is ;
Maternal history of myotonic dystrophy
Family history of specific neuromuscular disorder
Drawback of genetic testing
 prolonged time required for result to be available
 Interpretation of genetic result may be more complicated
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59. REFERENCES
• Swaiman’s Pediatric neurology : Principles and Practice,6th edition
• Uptodate 2018
• Nelson text book of pediatrics 21 edition,2019
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