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Boy with seizures.

Contributed from the case records of the 
Indiana University Department of Radiology

History:  Boy with seizures.
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Which choice best localizes the salient abnormality?

Temporal lobe.Orbit.Thalamus.Posterior fossa.Optic nerve.
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Boy with seizures.

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Which choice best characterizes the abnormal finding?

Position of cerebellar tonsils.Dilatation of 4th ventricle.Mass within 4th ventricle.Abnormal signal in dural sinus.Mega cisterna-magna.
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Boy with seizures.



Given that this is the only significant CNS finding, which choice is the most likely diagnosis?

Chiari I malformation.Chiari II malformation.Chiari III malformation.Chiari IV malformation.
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Boy with seizures.

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Findings:  There is caudal protrusion of the cerebellar tonsils through the foramen magnum.


Differential diagnosis:

  • Chiari I
  • Chiari II
  • Intracranial hypotension
  • Normal age-related tonsillar descent
Diagnosis:  Chiari I malformation
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Boy with seizures.


Key points:
 

  • Chiari I malformation occurs when a normal sized cerebellum tries to fit in an underdeveloped posterior fossa.
  • The cerebellar tonsils protrude inferiorly through the foramen magnum.
  • There can be obstruction of CSF flow at the foramen magnum.
  • In children, tonsillar protrusion > 7mm is abnormal. In adults, 5mm is abnormal.
  • In contrast to Chiari II, Chiari I is not associated with myelomeningocele or any midline abnormality.
  • Patients with Chiari I may experience symptoms associated with obstructed CSF flow such as headache and syncope.
  • Treatment is aimed at restoring and maintaining CSF flow and involves surgical decompression.

References: 

  1. Aitken LA et al: Chiari type I malformation in a pediatric population. Pediatr Neurol. 40(6):449-54, 2009.
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Boy with seizures.


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