The molar tooth sign refers to the appearance of the midbrain in an axial section in which the elongated superior cerebellar peduncles give the midbrain an appearance reminiscent of a molar or wisdom tooth.
It was initially described in Joubert syndrome and related disorders (JSRD) 2 but is now recognized to occur in a number of other conditions, e.g. nephronophthisis, hepatic fibrosis, Cogan's syndrome, and pontine tegmental cap dysplasia 4.
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 3.
The absence of crossing fibers also leads to a reduction in the anteroposterior diameter of the midbrain and deepening of the interpeduncular cistern 3.
- 1. Barkovich AJ. Pediatric neuroimaging. Lippincott Williams & Wilkins. (2005) ISBN:0781757665. Read it at Google Books - Find it at Amazon
- 2. Harbert MJ, Gleeson JG. Classifying a novel brain malformation. Brain. 2007;130 (Pt): 2242-4. doi:10.1093/brain/awm194 - Pubmed citation
- 3. Mcgraw P. The molar tooth sign. Radiology. 2003;229 (3): 671-2. doi:10.1148/radiol.2293020764 - Pubmed citation
- 4. Cadman CJ, Fraser L, McArthur C. Case 266: Pontine Tegmental Cap Dysplasia. (2019) Radiology. 291 (3): 814-818. doi:10.1148/radiol.2018162304 - Pubmed