Sella/Pituitary Normal Variants

Anne G. Osborn, MD, FACR

DIFFERENTIAL DIAGNOSIS

Common

Less Common

Rare but Important

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Helpful Clues for Common Diagnoses

Pituitary Hyperplasia (Physiologic)
- Enlarged pituitary gland
  - 10-15 mm, convex upwards
  - Enhances strongly, uniformly
- May be indistinguishable from macroadenoma, lymphocytic hypophysitis
- Beware: “Macroadenoma-appearing” pituitary in young males may be physiologic hyperplasia, not tumor!
Pituitary “Incidentaloma”
- “Filling defects” in 15-20% of normal scans
- Cystic changes common, may be transient
“Empty” Sella (ES)
- Rarely (if ever) truly empty
- Intrasellar CSF, pituitary gland flattened against sellar floor
- Primary ES
  - Considered normal variant
  - Usually asymptomatic, incidental finding
  - 5-10% prevalence
  - Peak age 40-49 years
- Secondary ES
  - Surgery, radiation, bromocriptine therapy
  - Sheehan syndrome (postpartum pituitary necrosis)

Helpful Clues for Less Common Diagnoses

“Bright” Pituitary Gland
- Neonate: Adenohypophysis large, hyperintense on T1WI
- Size, signal ↓ during first 6 weeks
Absent Posterior Pituitary “Bright Spot”
- Neurohypophysis normally has short T1
- Commonly absent in central DI
- Found in up to 20% of normal patients
Small Sella Turcica
- Small or shallow bony sella can be normal
- Causes pituitary gland to protrude upwards