Posterior pituitary bright spot

Last revised by Francis Deng on 13 Sep 2023

The posterior pituitary bright spot is the normal hyperintensity of the neurohypophysis on non-contrast T1 weighted MR images. 

Most studies have found posterior pituitary bright spots in 90-100% of normal patients 2,3,6,8,9. One notable exception found it in only 52% of patients on T1 weighted images 1. It was visualized on 3D time-of-flight angiography source images at 3T in 83% of patients 7.

The signal intensity of the posterior pituitary declines with age and is higher in females 1,3,6.

The posterior pituitary bright spot, having intrinsically high signal on T1 weighted images is believed to be from the storage of vasopressin, which has a T1-shortening effect 2. The hormone is synthesized in the hypothalamus and carried down the axons that form the stalk to the posterior pituitary bound to a vasopressin-neurophysin II-copeptin complex, a macromolecular structure that shortens T1 relaxation time 4

In individuals with compression or interruption of the stalk the aforementioned downward transport can be halted and brightness can be seen above the compression/interruption. This should not be mistaken for an ectopic posterior pituitary 4

  • oval/round high T1 signal, best seen on sagittal images in the posterior aspect of the pituitary fossa

  • normal measurements (decreasing size with age) 1,2

    • long axis: 1.2-8.5 mm

    • short axis: 0.4-4.4 mm

The absence of posterior pituitary bright spot should prompt the consideration of the following (noting it may be absent in normal patients): 

When a T1 hyperintensity is seen in the sella without the typical morphology and location of the posterior pituitary bright spot, other causes should be considered: pituitary region mass with intrinsic high T1 signal.

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