Normal bone marrow signal of the clivus

Last revised by Henry Knipe on 31 Oct 2023

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%

    • 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 homogeneously 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.

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