Molar tooth sign on MRI

What it means

An abnormal appearance of the midbrain in axial magnetic resonance imaging in which the elongated superior cerebellar peduncles give the midbrain an appearance reminiscent of a molar or wisdom tooth.

Molar tooth appearance results from a lack of normal decussation of superior cerebellar peduncular fiber tracts which in turn leads to enlargement of the peduncles, which also follow a more horizontal course. The absence of crossing fibers also leads to a reduction in the anteroposterior diameter of the midbrain and deepening of the interpeduncular cistern.

Rare diseases that can present with this8

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Molar tooth sign · Molar tooth sign on brain imaging · Molar tooth sign on imaging