Cranial Dysraphism

Aka: Cranial Dysraphism, Cranial Neural Tube Defect, Cranial Bifidum, Cephalocele, Encephalocele, Anencephaly, Congenital Exophytic Scalp Nodule

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II. Definitions

  1. Cranial Dysraphism
    1. Incomplete raphe closure results in Cranial Bifidum
  2. Cranial Bifidum
    1. Bony midline cranial defect allowing Cephalocele
  3. Cephalocele
    1. Congenital Herniation of intracranial contents
    2. Meninges or brain protrudes via a scalp defect
  4. Cranial Meningocele
    1. Herniation of Meninges and cerebrospinal fluid
  5. Encephalocele
    1. Herniation of brain through skull defect
  6. Anencephaly ("Absence of the head")
    1. Complete absence of brain in most cases
    2. Absence of calvarium covering brain

III. Causes

  1. Idiopathic
  2. Meckel-Gruber Syndrome
    1. Autosomal Recessive cause of occipital Encephalocele

IV. Signs

  1. Site
    1. Frontal, parietal or occipital swelling
    2. Midline or just lateral of midline
  2. Characteristics
    1. Soft, compressible Nodule
    2. Increases in size with infant crying or Valsalva
    3. Disrupts normal hair pattern
    4. Covered by normal, blue or translucent skin
  3. Findings highly correlated with Cephalocele
    1. Congenital Exophytic Scalp Nodule
      1. Nontraumatic scalp Nodule
      2. As many as 37% communicate with CNS
    2. Hypertrichosis (hair collar sign)
      1. Ring of denser, darker, coarser hair around Nodule
  4. Associated dermatologic findings
    1. See Cutaneous Signs of Dysraphism
    2. Capillary malformation
    3. Hemangiomas
    4. Skin dimpled or sinus evident

V. Diagnosis

  1. Transillumination
    1. Identifies neural tissue within sac
  2. XRay for anatomic definition
    1. Skull XRay
    2. Cervical Spine XRay
  3. Cranial Ultrasound
    1. Identifies sac contents

VI. Complications

  1. Cranial Meningocele carries good prognosis
  2. Encephalocele complications
    1. Hydrocephalus
    2. Vision disorders
    3. Microcephaly
    4. Mental Retardation
    5. Seizure Disorder

VII. References

  1. Behrman (2000) Nelson Pediatrics, Saunders, p. 1806
  2. Goetz (1999) Neurology, Saunders, p. 515-16
  3. Drolet (2000) Pediatr Clin North Am 47(4):813-23 [PubMed]

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