Molar tooth sign

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[edit] Discussion of Molar tooth sign

  • The molar tooth sign is seen on transverse computed tomographic and magnetic resonance images obtained at the level of the midbrain in patients with Joubert syndrome.
  • The term molar tooth refers to the characteristic appearance of an enlarged and horizontally directed tubular structure on each side of the midline emerging from the midbrain.
  • The sign is caused by a lack of normal decussation of superior cerebellar peduncular fiber tracts.
  • A lack of decussation leads to enlargement of the peduncles; in addition, the peduncles follow a more horizontal course as they extend perpendicularly to the brainstem between the midbrain and the cerebellum.
  • The absence of crossing fibers is responsible for the decreased anteroposterior diameter of the midbrain and also causes the interpeduncular cistern to be deeper than that in the normal brain.
  • The combination of these findings leads to the characteristic "molar tooth" appearance on transverse CT and MR images of the midbrain in patients with Joubert syndrome.

[edit] Images

Patient #1

[edit] See Also

[edit] External Links

Goldminer: Molar tooth sign

[edit] References for Molar tooth sign