Pediatric Neurology Quick Talks

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Pediatric Neurology Quick Talks

• Hypotonia
• Michael Babcock
• Summer 2013

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Scenario

• 2 do M in the NICU
• Poor feeding and weakness
• Not intubated
• Delivered 37 weeks by C/S failure to progress
• Poor maternal pre-natal care
• HC 50
• Exam axillary slippage, reduced spontaneous
  movements, head lag, normal suck. awake

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Hypotonia Localize gt Central or Peripheral

• Central (brain/spinal cord)
• Normal/mild weakness
• normal bulk
• normal/increased reflexes
• Dysmorphisms
• encephalopathy

• Peripheral (Anterior horn, peripheral nerve, NMJ,
  muscle)
• Marked weakness
• decreased bulk
• decreased reflexes
• no dysmorphisms
• Awake, alert

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Central Causes

• Sepsis
• Maternal narcotics
• Hypothyroid
• Prematurity
• HIE
• Down's Syndrome
• Prader-Willi
• Inborn Errors of Metabolism
• Zellweger
• Cerebral dysgenesis

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Peripheral Causes

• Anterior Horn
• SMA
• Pompe
• Peripheral Nerve (uncommon)
• Inflammatory GBS
• Demyelinating
• Axonal
• Metabolic- Leigh

• Neuromuscular Junction
• Myasthenias
• Infantile botulism
• Hypermagnesemia
• Muscle
• Myopathy
• Muscular dystrophy
• Myotonic dystrophy
• Metabolic myopathy

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Perkowski's top 5 not to miss causes of floppy
baby

• Down's syndrome
• Prader Willi
• Pompe (have heart problems)
• Zellweger
• Spinal Muscular Atrophy
• However, most common is HIE

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History

• Mother systemic illness, fever, substance abuse
• Pregnancy polyhydramnios, fetal movement,
  abnormal lie
• Delivery complicated/prolonged, trauma, Apgars
• Family history delayed milestones, weakness,
  myotonia

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Exam Assess Tone

• Tone is resistance to stretch forces, develops
  with nervous system development, low tone is
  normal for premature infants Ballard testing.
• Resting posture assess resting posture when
  infant is quiet/drowsy
• Hypotonic infant frog leg position
• Long-standing immobility can cause joint
  contractures arthrogryposis
• Passive manipulation
• Infants develop increasing flexor tone in
  extremities causes increased recoil after limb
  is extended
• Head control in vertical/horizontal suspension
• Vertical suspension

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Ballard Testing Testing tone
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Work Up

• Central
• Electrolytes (Mg, Ca, Gluc)
• TFT's
• Brain imaging U/S vs MRI
• EEG
• Karyotype, CMA
• Metabolic work-up

• Peripheral
• CK
• EMG/NCS
• muscle/nerve bx

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Spinal Muscular Atrophy (SMA)

• AR SMN1 gene SMN protein (survival motor
  neuron) SMN2 gene regulates severity
• Weakness and atrophy of muscles, including tongue
• Symmetric weakness, more proximal than distal,
  more severe in LE
• Tongue fasciculations
• Absent DTRs
• Normal intellectual capacity
• Facial muscles typically spared early on

• Types
• Type 1 infantile - Werdnig Hoffman - lt6mo. -
  never sit
• Type 2 intermediate - Dubowitz 6-18 months
  never walk
• Type 3 juvenile - Kugelberg-Welander 18mo- 17
  years. - able to walk initially, often lose this.
• Type 4 adult-onset

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Myasthenias

• Congenital
• Genetic disorder of NMJ
• Hypotonia, weakness (ocular, bulbar, respiratory)
• Variable onset, sometimes in utero
  arthrogryposis
• Recurrent ALTEs
• Fatigability, weak cry, feeding difficulties,
  episodic apnea
• Sometimes respond to AchE inhibitors
• Transient neonatal
• Transplacental transfer of AchR Antibodies.
• 10-15 of infant of myasthenic mothers
• Hypotonia, weaknessbulbar and respiratory,
  within 4 days of birth
• Good response to AchE inhibitors

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Infant Botulism

• Weakness and hypotonia
• Can have hx of honey ingestion though
  contamination from soil is most common
• Constipation is often first sign
• Eye findings, ophthalmoplegia botulism is
  descending paralysis
• Can test stool
• Can give Human boutlinum immunoglobulin 50mg/kg
  in first few days shortens course
• Often severe respiratory weakness requiring
  ventilation, prolonged course.

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Prep Question

• During the health supervision visit for a 6 week
  old boy, his father expresses concern that his
  son doesnt look like his other children.
  Growth parameters are normal except for a head
  circumference of 35.5 cm (lt5th percentile).
• On PE, you note that the infant does not appear
  to fixate or track your face visually. There is a
  slip through on vertical suspension and
  draping over on horizontal suspension. DTRs are
  brisk. Moro reflex is present and brisk. Of the
  following, the MOST likely cause of this infants
  hypotonia is

• Anterior horn cell disease
• Congenital brain malformation
• Congenital myasthenic syndrome
• Congenital myopathy
• Spinal cord disease

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B. Congenital brain malformation

• Hypotonia
• Localize! UMN vs. LMN signs, axial vs
  appendicular
• Take into account growth parameters, especially
  HC, as well as features such as tracking
• Regarding other choices
• A. anterior horn cell disease wouldn't cause
  microcephaly or increased reflexes
• C. Congenital myasthenic syndrome wouldn't
  cause microcephaly or brisk reflexes
• D. Congenital myopathy no microcephaly or poor
  visual tracking
• E. Spinal cord disease wouldn't cause
  microcephaly or poor visual tracking.

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References

• Paediatr Child Health. 2005 September 10(7)
  397400. PMCID PMC2722561 A schematic approach
  to hypotonia in infancy
• Respiratory update.com