There are numerous causes for intracranial calcifications and for lesions to appear hyperattenuating (dense) on non-contrast computed tomography (CT) scans.

Hyperdense Lesions

There are a variety of causes for lesions to be hyperdense (hyperattenuating) on CT scanning. One of the most common causes is hemorrhage, but other etiologies include dense cellularity, mucinous or proteinaceous lesions, and partial or “psammomatous” calcification. Some metabolic and toxic processes can also result in dense lesions, although the mechanisms are not well understood.

Lesions that May Appear Hyperdense on Non-contrast CT

Neoplastic Lesions

• Highly cellular, hemorrhagic, or calcified neoplasms
  
• “Round blue cell tumors” (high cellularity with high nuclear to cytoplasmic ratio)
  
• Lymphoma
  
• Primitive neuroectodermal tumors (PNET)
  
• Medulloblastoma
  
• High-grade ependymoma
  
• Germinoma
  
• Choroid plexus papilloma/carcinoma
  
• Meningioma (mild)
  
• Metastases (may be due to cellularity, blood, mucin, calcification): melanoma, adenocarcinoma, choriocarcinoma, renal cell, carcinoma, osteosarcoma

Mucin or Protein-Containing Lesions

• Colloid cyst (may vary in attenuation)
  
• Craniopharyngioma (cystic areas)
  
• Rathke’s cleft cyst: occasionally
  
• Mucinous metastases

Vascular Lesions

• Hemorrhagic tumors: Glioblastoma multiforme (GBM) Metastases (renal cell, choriocarcinoma, melanoma)
  
• Cavernous malformation: may be due to calcium, blood, or combination of both; may have stippled appearance
  
• Aneurysm with clot (or just with mildly dense blood): may have calcification of wall
  
• Arteriovenous malformation (AVM): may be increased density due to calcium in walls, may have associated parenchymal atrophy, low density or mass effect, and large draining veins, etc.
  
• Hemorrhage from any cause

• Toxoplasmosis (generally hypodense, but may have hyperdense central area)

Metabolic