Pituitary MRI Recognition Pattern

Systematic approach to interpreting pituitary MRI with anatomical landmarks, pathological patterns, and protocol optimization

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1. MRI Protocol

A. Standard Sequences

• • Sagittal T1:
  - 3mm slices
  - Anatomical overview
  - Pituitary stalk evaluation
• • Coronal T1:
  - 2-3mm slices
  - Pituitary gland symmetry
  - Cavernous sinus invasion
• • Coronal T2:
  - Cystic vs solid lesions
  - CSF pulsation artifacts

B. Dynamic Contrast-enhanced

• • Timing:
  - 20-30 sec temporal resolution
  - 5-7 acquisitions
  - Early arterial phase critical
• • Slice alignment:
  - Perpendicular to stalk
  - Cover entire sella

2. Anatomical Landmarks

A. Normal Measurements

Structure

Normal Size

Pituitary height

≤8mm (adults), ≤10mm (postpartum)

Infundibulum

≤3mm diameter

Posterior lobe

T1 hyperintense "bright spot"

B. Key Relationships

• • Cavernous sinus:
  - CN III, IV, V1, V2, VI
  - Internal carotid arteries
• • Optic chiasm:
  - 5-10mm above diaphragm
  - Visual field correlation

3. Microadenoma Features

A. Typical Characteristics

Sequence

Appearance

T1

Hypo/isointense to pituitary

T2

Variable (often hyperintense)

Dynamic CE

Delayed enhancement

B. Location Clues

• • Prolactinoma:
  - Lateral wing (70%)
  - More common in women
• • ACTH-secreting:
  - Central (60%)
  - Often smallest at diagnosis

4. Macroadenoma Features

A. Invasion Assessment

Grade

Criteria

I

Confined to sella

II

Suprasellar extension

III

Local invasion (cavernous sinus/floor)

IV

Diffuse invasion

B. Hemorrhage/Cystic Change

• • Pituitary apoplexy:
  - Acute headache
  - T1: hyperintense blood products
  - T2: variable depending on age

5. Non-Adenoma Lesions

A. Cystic Lesions

Lesion

Key Features

Rathke's cleft cyst

Midline, T1 variable (50% hyper)

Arachnoid cyst

CSF signal, no enhancement

B. Solid Masses

• • Craniopharyngioma:
  - 90% suprasellar
  - Adamantinomatous (T1/T2 mixed)
  - Papillary (T1 iso, T2 hyper)
• • Meningioma:
  - Dural tail
  - Homogeneous enhancement
  - Hyperostosis

6. Post-Surgical Assessment

A. Expected Findings

• • Transsphenoidal:
  - Fat packing (T1 hyper)
  - Surgical defect in sphenoid

B. Complications

• • CSF leak:
  - Fluid in sphenoid sinus
  - Meningeal enhancement
• • Diabetes insipidus:
  - Absent posterior bright spot
  - Thickened stalk

7. Reporting Template

• 1. Technique: Sequences, contrast use
• 2. Pituitary gland:
  - Size/symmetry
  - Focal lesions
• 3. Stalk:
  - Thickness
  - Deviation
• 4. Adjacent structures:
  - Optic chiasm
  - Cavernous sinus
• 5. Post-surgical (if applicable)

Always correlate with endocrine labs. For Cushing's disease, focus on the central gland with dynamic imaging. In prolactinomas, measure lesion size to monitor medical therapy response. Postoperative scans should be obtained at least 3 months after surgery to allow for resolution of postoperative changes. Document incidental findings (empty sella, vascular loops) with appropriate clinical context.

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