Zoran Rumboldt MD, Presenter: Nothing to Disclose

Zeke Walton, Abstract Co-Author: Nothing to Disclose

Bernard Lee Maria MD, Abstract Co-Author: Nothing to Disclose

Joubert syndrome (JS) is a rare autosomal recessive disorder with a distinctive hindbrain malformation in which absence of decussation of both corticospinal and superior cerebellar tracts has been proposed as an underlying abnormality. The goal of this study was to investigate whether evidence for loss of decussation of the superior cerebellar peducles (SCP) may be found on routine brain MRI studies.

Midsagittal T1-weighted images from 20 patients with JS and 30 age-matched control patients were retrospectivly reviewed. The patients were divided into different age groups: 0-6 months, 6-12 months, 12-30 months, 30 months-5 years, and over 5 years of age. The digital images (one image per patient) were magnified and cropped to show only the brainstem and were then evaluated by a neuroradiologist, who was blinded to all the patient data. An ill-defined oval area of lower T1 signal intensity in the inferior midbrain was considered the sign of SCP decussation, and its presence or absence was noted. The obtained results were analysed for statistical significance using Fischer's exact test.

The hypointensity corresponding to the SCP decussation could not be visualized in any patient under 30 months of age, either in JS patients or in the control group. In subjects who were 30 months or older the sign of SCP decussation was also absent in all 6 JS patients, but was present in all 16 control group patients. The observed difference between JS patients and control group in presence of SCP decussation sign for age 30 months and older was statistically significant at p<0.0001 level.

The decussation of SCP is well seen on routine brain MRI studies in normal subjects at the age of 30 months and older. The decussation appears to be absent in JS patients, confirming the proposed lack of commissural fibers in Joubert syndrome.

Rumboldt, Z, Walton, Z, Maria, B, Absence of Decussation of the Superior Cerebellar Peduncles in Patients with Joubert Syndrome.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4414864.html