Normal bone marrow signal of the clivus
Bone marrow signal of the clivus changes predictably with age and is well assessed with midline T1 non-fat-saturated, non-contrast images. As is seen in the rest of the body the proportion of yellow (fatty) marrow increases with age. Knowledge of these changes allows the diagnosis of the abnormal clivus.
Kimura et al 1 divided the appearance into three grades, by comparing the clivus to the pons and subcutaneous fat. A high signal was similar to subcutaneous fat, whereas low was iso- to slightly hypointense to the pons. It should be pointed out that the figures obtained in the study by Kimura et al, have not been exactly replicated in other studies 2,3, and that the grading proposed is by no means widely used in clinical practice. Nonetheless, it serves as a useful guide when examining MRI of the brain, and relating bone marrow signal to age.
- grade 1: predominantly low signal (>50% of clivus)
- grade 2: mixed-signal (low signal 20-50% of clivus)
- grade 3: predominantly high signal (>80% of clivus)
The signal will vary according to the age of patients 1:
- patients in their 20s
- grade 1: 33% of patients
- grade 2: 33%
- grade 3: 34%
- patients in their 50s
- grade 1: 0%
- grade 2: 40%
- grade 3: 60%
- patients in their 80s
- grade 1: 0%
- grade 2: 0%
- grade 3: 100%
To make things simple, the calvarial bone marrow signal intensity should homogenously match the white matter on non-contrast, T1 non-fat-saturated images as an internal reference standard 3. Most importantly, a finding of low signal in elderly patients warrants comment and review of additional imaging and clinical information.
- 1. Kimura F, KS Kim, H Friedman et al. “MR imaging of the normal and abnormal clivus.” Am. J. Roentgenol. 155, no. 6 (December 1, 1990): 1285-1291. [Link].
- 2. Olcu E, Arslan M, Sabanciogullari V et-al. Magnetic resonance imaging of the clivus and its age-related changes in the bone marrow. Iran J Radiol. 2011;8 (4): 224-9. doi:10.5812/iranjradiol.4494 - Free text at pubmed - Pubmed citation
- 3. Loevner LA, Tobey JD, Yousem DM et-al. MR imaging characteristics of cranial bone marrow in adult patients with underlying systemic disorders compared with healthy control subjects. AJNR Am J Neuroradiol. 2002;23 (2): 248-54. AJNR Am J Neuroradiol (full text) - Pubmed citation