Miscellaneous Intracranial Metastases

KEY FACTS

Terminology

• Brain metastases in locations other than skull/meninges or parenchyma

Imaging

• General features

  • > 95% of brain metastases parenchymal

  • Only 1-2% in ventricles, pituitary gland, etc.

  • Sites generally very vascular

  • Extraventricular metastases more diffuse, infiltrative than parenchymal metastases (usually round)

• Location

  • Choroid plexus ± ventricular ependyma

  • Pituitary gland infundibulum

  • Eye (choroid)

  • Cranial nerves

  • Pineal gland

  • Preexisting neoplasm (“collision tumor”)

• Best imaging tool: MR with T1WI C+ FS

  • Metastases almost always enhance

Top Differential Diagnoses

• Varies with location

• Choroid plexus, ventricle = meningioma

• Pituitary gland, infundibular stalk

  • Pituitary macroadenoma

  • Lymphocytic hypophysitis

  • Lymphoma

• Cranial nerves = neurofibromatosis type 2, lymphoma

• Eye (globe)

  • Ocular melanoma

  • Retinal or choroidal detachment

  • Choroidal hemangioma

Diagnostic Checklist

• Look for “secret sites” outside parenchyma when imaging brain for possible metastatic disease

TERMINOLOGY