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Infundibular thickening refers to abnormal enlargement of the pituitary stalk (infundibulum), usually detected on contrast-enhanced MRI.

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The normal pituitary stalk tapers from superior (3–4 mm at the optic chiasm) to inferior (1.5–2 mm at the pituitary insertion). Thickening indicates infiltration, inflammation, or neoplasm.

Etiopathology

Causes can be grouped as:

| Neoplastic | • Germinoma (most common in children/young adults; often with diabetes insipidus, part of bifocal germinoma if pineal also involved). • Metastasis (breast, lung, lymphoma, leukemia). • Langerhans cell histiocytosis (LCH) (common pediatric cause; systemic disease with osseous and skin involvement). • Primary CNS lymphoma. • Pituitary adenoma (rare stalk involvement). | | --- | --- | | Inflammatory / Granulomatous | • Lymphocytic hypophysitis (autoimmune; often in peripartum women). • Granulomatous hypophysitis (TB, sarcoidosis, syphilis, fungal). • IgG4-related hypophysitis. | | Congenital / Others | • Rathke’s cleft cyst rupture with inflammation. • Idiopathic (diagnosis of exclusion) |

Clinical Features

| Endocrine dysfunction | • Diabetes insipidus (very common, especially in germinoma, LCH, metastasis). • Hypopituitarism (GH, TSH, ACTH deficiencies). • Hyperprolactinemia (stalk effect). | | --- | --- | | Visual symptoms | Compression of optic chiasm. | | Systemic features | • LCH: Bone lesions, skin rash, diabetes insipidus. • Sarcoidosis/TB: Systemic involvement. • Germinoma: May be part of bifocal presentation with pineal lesion. |

Radiology

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MRI shows loss of normal tapering, with enhancing thickened stalk and loss of posterior pituitary bright spot.

• Normal stalk: 3–4 mm superiorly, <2 mm inferiorly. Smooth tapering. </aside>

Patterns**:**

Ancillary investigations

Diagnostic Workup

• Endocrine evaluation (pituitary hormones, water deprivation test).
• Serum/CSF tumor markers (β-hCG, AFP for germ cell tumors).
• Systemic workup (bone survey, chest imaging, biopsy for sarcoidosis/LCH).