Pineal Cyst

KEY FACTS

Terminology

• Nonneoplastic intrapineal glial-lined cyst

Imaging

• CT

  • Sharply demarcated, smooth cyst behind 3rd ventricle

  • 80% < 10 mm (can be large; reported up to 4.5 cm)

  • Fluid iso-/slightly hyperdense to cerebrospinal fluid (CSF)

  • 25% Ca++ in cyst wall

• MR

  • Slightly hyperintense to CSF (55-60%) on most sequences

  • Isointense (40%)

  • 1-2% hemorrhage (heterogeneous signal intensity)

  • Does not suppress on FLAIR

Top Differential Diagnoses

• Normal pineal gland

• Pineocytoma

• Epidermoid cyst

• Arachnoid cyst

• Pineal parenchymal tumor of intermediate differentiation

Clinical Issues

• Vast majority clinically silent, discovered incidentally

  • Occur at all ages

  • Found in 1-5% of normal MRs

  • May spontaneously resolve in children

• Headache (less common)

• “Pineal apoplexy” with intracystic hemorrhage (rare)

  • ± acute hydrocephalus, sudden death (very rare)

Diagnostic Checklist

• Cannot distinguish benign PC from neoplasm (pineocytoma) on basis of imaging studies alone

  • Both may remain stable for many years

• Heterogeneous, nodular, or ring-like enhancing pineal mass may be benign cyst, not neoplasm

TERMINOLOGY

IMAGING