Tuberculosis Hypophysitis

Background:

• Inflammatory and granulomatous lesions of the pituitary gland can mimic neoplastic etiologies.
• Tuberculosis of the pituitary, although quite rare, is a cause of secondary granulomatous hypophysitis.

Clinical Presentation

• Headache is the most common symptom.
• Visual disturbances such as affection of visual fields, visual acuity, diplopia, mydriasis, or blurred vision
• Multiple pituitary hormone deficiencies

Key Diagnostic Features

• Diffusely enlarged, globular contour of the pituitary gland with moderate heterogeneous enhancement
• Thickened, enhancing infundibulum (usually not deviated)
• Absent posterior pituitary bright spot on sagittal T1-weighted images
• Parasellar involvement may occur with larger lesion size. Features such as dural tail, erosion of the sellar floor, involvement of the cavernous sinus/Meckel cave, and visual pathways may occur.
• Occasional thickening of the mucosa lining the sphenoid and adjacent posterior ethmoid sinuses

Differential Diagnoses

• A number of entities with secondary involvement of the pituitary gland may have similar imaging presentations. Hypophysitis can have different etiologies, and correlation to the clinical presentation, demographics, and systemic findings can be helpful.
• Lymphocytic hypophysitis: Lymphocytic infitration. Temporal association with late pregnancy or the early postpartum period. Near-symmetric homogeneous enhancement of the pituitary gland. Parasellar dark T2 signal may be seen (usually not observed with pituitary adenomas).
• Medication induced: Use of ipilimumab, most often in the setting of metastatic melanoma; breast, lung, or kidney cancer. Usually no parasellar extension.
• Other granulomatous conditions such as sarcoidosis and other key systemic manifestations of sarcoidosis. Otherwise, the differential diagnosis is mainly histologic.
• IgG4-related hypophysitis: Lymphoplasmacytic infiltration mainly with IgG4-positive plasma cells. Nonspecific enlargement of the pituitary gland with or without infundibulum enlargement. Hypertrophic pachymeningitis may be seen.
• It may be difficult to distinguish pituitary adenoma from:
  • Pituitary macroadenoma: Pituitary volume can be much greater in large macroadenomas with an asymmetric expansion of the sella. In addition, macroadenomas are typically T2 isointense to gray matter. The Gutenberg score can also be useful in differentiating between macroadenoma (asymmetric growth, parasellar invasion) and autoimmune hypophysitis.
  • Pituitary metastasis: Mass involving both the intra- and suprasellar compartments, having irregular edges and dumbbell shape
• Enhancement of the pituitary stalk can be seen in the setting of germinoma, lymphoma, or Langerhans cell histiocytosis.