Posterior pituitary bright spot

Normal MRI finding representing the neurohypophysis.

On non-contrast T1-weighted images, the posterior pituitary appears as a small, midline, T1-hyperintense dot at the back of the sella. The high signal is thought to relate to vasopressin-containing neurosecretory granules and their lipid/protein content.

Typical appearance:

• Sagittal T1: bright focus at the posterior floor of the sella.
• Coronal T1: bright dot at the posterior margin of the gland.

Clinical significance:

• Usually preserved (or displaced) in pituitary adenoma → diabetes insipidus (DI) at presentation is uncommon.
• Absent or ectopic bright spot suggests central DI or stalk pathology, e.g.:
  • Hypophysitis
  • Langerhans cell histiocytosis
  • Metastasis / post-surgical / post-radiation damage
  • Stalk interruption syndrome
    • Ectopic bright spot at median eminence
    • Thin/absent stalk
    • Small anterior gland).

Exam line: “Loss or ectopic posterior bright spot = think central DI / stalk disease.