Updated: 4/13/2019

CNS Abnormalities

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Forebrain
  • Anencephaly
    • failure of anterior neuropore to close resulting in failure of brain and calvarium to form
    • no swallowing center → polyhydramnios
    • AFP 
      • most common cause of  ↑ AFP is incorrect pregnancy dating 
  • Holoprosencephaly
    • failure of prosencephalon to divide and form cerebral hemispheres
      • absence of olfactory bulbs and tracts
      • cyclopia, cleft palate, cleft lip
    • associated with
      • Patau syndrome (trisomy 13) and Edwards syndrome (trisomy 18)
      • severe fetal alcohol syndrome
      • cleft lip/palate
      • fetal alcohol syndrome
Posterior Fossa
  • Dandy-Walker syndrome 
    • dilation of 4th ventricle
    • absence of cerebellar vermis
    • small cerebellar hemispheres
    • posterior fossa cysts
    • enlargement of posterior fossa
    • associated with hydrocephalus and spina bifida
  • Arnold Chiari I 
    • cerebellar tonsil herniation through foramen magnum
    • often presents in adulthood with chronic headaches and ataxia
    • associated with cervico-thoracic syringomyelia 
    • milder in severity in comparison to type II malformations 
  • Arnold Chiari II 
    • due to small posterior fossa, the cerebellar tonsils herniate through foramen magnum causing aqueductal stenosis and hydrocephaly 
    • may present with synringomelia, thoracolumbar spina bifida with myelomeningocele
    • symptoms present from compression of medulla oblongata and CN IX, X, and XI
      • reduced gag reflex
      • vocal cord paralysis
      • laryngeal stridor
      • swallowing difficulty
      • spastic dysphonia
Spinal Cord
  • Syringomyelia 
    • central canal of spinal cord enlarges
    • nerves closest to central canal affected first
      • spinothalamic tract: bilateral loss of pain and temperature sensation in affected area, touch not affected
        • occurs most often at C8-T1
        • cape-like pattern loss
      • often associated with Chiari I, less frequently with Chiari II

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(M1.EB.15.75) A 32-year-old male presents to his primary care physician with complaints of chronic headaches that have developed and increased in frequency and severity over the last several months. Additionally, the patient has noted he has been less coordinated over the last few weeks, stumbling and tripping often when he is walking. Physical examination is significant for notably reduced hand grip strength bilaterally as well as decreased pain and temperature sensation along the upper back and down both arms to the hands. A referral to the appropriate specialist is made, and an MRI of the brain and neck is obtained. Results of the MRI are show in Figures A and B. Which of the following is the most likely diagnosis in this patient?

QID: 106776
FIGURES:
1

Arnold-Chiari malformation type 1

43%

(15/35)

2

Arnold-Chiari malformation type 2

23%

(8/35)

3

Arnold-Chiari malformation type 3

14%

(5/35)

4

Arnold-Chiari malformation type 4

3%

(1/35)

5

Budd-Chiari syndrome

6%

(2/35)

M 2 E

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