Neurology




Neonatal Seizures



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Etiologies of Neonatal Seizures
























Underlying Defect


Points to Remember


Hypoxic–ischemic encephalopathy




  • Leading cause of neonatal seizures in full-term infants.
  • This diagnosis should never be one of exclusion.
  • Data supporting this diagnosis (history of prolonged labor, perinatal depression, prolonged resuscitation) should be obtained and documented.


Focal ischemia/infarction




  • Second most common cause of neonatal seizures in full-term infants.
  • Most common presentation is right-sided clonic seizures due to infarction in the left middle cerebral artery territory.
  • Cerebral vein thromboses can lead to venous infarcts.


Intracranial hemorrhage




  • In term infants, subarachnoid hemorrhage is more associated with subsequent seizure than subdural hemorrhage.
  • Infratentorial subdural hemorrhages require urgent evaluation due to risk of brainstem compression.
  • In preterm infants, intraventricular hemorrhage is the most common type of ICH (see below).


Infections of the CNS




  • Can occur in utero (CMV, toxoplasmosis) or perinatally (herpes simplex, bacterial meningitis with GBS or Escherichia coli being most common).
  • Prognosis can be very grim.


Metabolic derangement




  • Transient causes (hypoglycemia, hypocalcemia, hyponatremia); see Chapter 34 for further information.
  • Inborn errors of metabolism (pyridoxine dependency, nonketotic hyperglycinemia, urea cycle defects, glutaric aciduria (type II), maple syrup urine disease, organic acidurias, cofactor deficiencies, mitochondrial defects , Zellweger Syndrome).


Structural defects




  • Defects of neuronal migration (heterotopias).
  • Defects of neuronal organization (polymicrogyria).
  • Cerebral malformation (holoprosencephaly).
  • Usually will display associated dysmorphic features on physical examination.





Common Causes of Neonatal Seizures by Age at Presentation



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Day of Life


Possible Causes


1


Hypoxic ischemic encephalopathy


Infection


Hypocalcemia


Maternal drug use


Hypoglycemia


2–3


All of the above


Inborn errors of metabolism


Drug withdrawal


CNS malformation


Hypernatremia


Hyponatremia





Classification of Neonatal Seizures



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Seizure Type


Clinical Manifestation


Subtle


Oral–buccal–lingual or ocular movements


Autonomic dysfunction (Δ in HR, BP, Spo2)


Stereotypical stepping/swimming


Clonic


Rhythmic, slow jerking


Facial, extremity, or axial involvement


Focal or generalized


Tonic


Sustained limb posturing


Asymmetric position of trunk/neck


Focal or generalized


Myoclonic


Rapid isolated jerks


Limb/trunk involvement


Generalized, multifocal, or focal





Neonatal Seizure Mimics



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Seizure Mimic


Clinical Manifestation


Jitteriness


Spontaneous or provoked by stimulus


Flexion/extension are equivalent


Diminished by repositioning


Abolished with containment


Benign neonatal sleep myoclonus


Bilateral or unilateral


Synchronous or asynchronous


Occurs during sleep


Not due to a stimulus


Stimulus-evoked myoclonus


Focal or generalized


Severe CNS dysfunction


EEG may show cortical spike-wave discharge


Hyperekplexia (stiff-man syndrome)


Generalized stiffness


Autosomal dominant and recessive forms


Excessive startle responses to unexpected stimuli


Excessive stiffness following startle response


Benzodiazepines reduce symptoms





Management




  • Support respiratory and cardiovascular function (may require endotracheal intubation and mechanical ventilation).
  • Place on continuous cardiorespiratory monitoring.
  • Correct any known causes of seizures (see above).
  • If seizures continue after correction of transient metabolic derangements, load with phenobarbital (20 mg/kg IV); can be followed by repeat doses of 5–10 mg/kg IV to a total dose of 40 mg/kg IV, if needed.
  • If seizures continue, load with a benzodiazepine such as midazolam (0.1 mg/kg IV; repeat doses can be given to a total dose of 0.3 mg/kg IV).
  • If seizures continue, load with fosphenytoin 20 mg/kg.
  • If seizures continue, can consider loading with pyridoxine (100 mg/kg IV), preferably with EEG monitoring. Maintenance dosing can be 50-100 mg/dose once daily (orally)
  • Newer agents that are used in older children, adolescents, and adults may sometimes be given (in consultation with the neurology service), but no data exist on the safety and efficacy of these medications in neonates.




Intraventricular Hemorrhage



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  • Definition: an intracranial hemorrhage that originates in the paraventricular subependymal germinal matrix and may extend into the lateral ventricular system.

    • 50% of IVH occurs in the first 24 h after birth, and 90% by 7-10 days of life..
    • Incidence and severity are inversely proportional to gestational age.
    • Antenatal steroid administration is associated with a lower incidence.
    • Major risk factors:

      • Extreme prematurity
      • Need for assisted ventilation
      • Pneumothorax

    • Clinical presentation can be very diverse:

      • May be asymptomatic
      • May have nonspecific symptoms (bulging fontanelle, sudden drop in hematocrit, apnea/bradycardia, metabolic acidosis, seizures, change in level of consciousness)
      • May present with a catastrophic constellation of symptoms (profound hypotension, severe neurogenic pulmonary edema, rapid deterioration in neurologic exam, decerebrate posturing)

    • All infants with birth weight <1500 g and any infant who the attending physician feels is at risk for IVH should receive a screening head US between 7 and 10 DOL.

      • If abnormalities are noted on the initial screening US, follow-up is recommended at weekly intervals to monitor for the development of posthemorrhagic hydrocephalus.
      • If no abnormalities are noted on the initial screening US, follow-up cranial imaging can be done at 36–40 wk postmenstrual age to evaluate for evidence of periventricular leukomalacia.




Papile’s Grading of Ivh



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Grade I


Germinal matrix hemorrhage


Grade II


Germinal matrix hemorrhage with intraventricular hemorrhage but without ventricular dilation


Grade III


Germinal matrix hemorrhage with intraventricular hemorrhage and dilation


Grade IV


Germinal matrix hemorrhage with parenchymal involvement






  • Prognosis:

    • Mortality in severe IVH (grades III/IV) is approximately 20%–50%.
    • Incidence of posthemorrhagic hydrocephalus in severe IVH (grades III/IV) is approximately 55%–80%.
    • Long-term major neurologic sequelae are related to the extent of parenchymal injury:

      • 15%–20% of infants with minor degrees of hemorrhage will have a major neurodevelopmental impairment (slightly higher than those without IVH).
      • 50%–80% of infants with severe hemorrhage will have major developmental impairment.




Neonatal Encephalopathy



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  • A diagnosis of neonatal encephalopathy can be considered when an infant has both a change in mental status and an abnormal neurologic examination.
  • The Sarnat classification is most frequently used to describe the severity of encephalopathy and is most appropriate for infants with HIE.




Sarnat Stages of HIE



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Stage 1 (Mild)


Stage 2 (Moderate)


Stage 3 (Severe)


Level of consciousness


Hyperalert


Lethargic


Stuporous, comatose


Tone


Normal


Hypotonic


Flaccid


Posture


Normal


Flexed


Decerebrate


Reflexes


Hyperactive


Hypoactive


Absent


Pupils


Mydriasis


Miosis


Unequal, poor light reflex, midline


Oculovestibular


Normal


Overactive


Weak or absent


Seizures


None


Common


Decerebrate


EEG


Normal


Low voltage with seizures


Burst suppression to isoelectric


Duration of symptoms


<24 h


2–14 d


Hours to weeks


Outcome


Nearly 100% normal


80% normal


∼50% die; survivors have severe sequelae

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Jan 9, 2019 | Posted by in PEDIATRICS | Comments Off on Neurology
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