Cavernous malformations are benign vascular hamartomas consisting of dysplastic immature vascular channels with variable mass effect depending on size. Although nearly always angiographically occult, these lesions may be dynamic in their behavior over time, with evidence of hemorrhagic products of mixed stages, and may present with acute parenchymal hemorrhage. Presentation can include seizure (up to 50%) or focal neurologic deficit (25%) or can be asymptomatic/incidental (20%).

• General characteristics
  • Masses of immature, cavern-like vascular channels or blood pools of variable complexity
    • Loculated intralesional hemorrhages with different stages of blood product evolution
    • Complete hemosiderin rim usually surrounds lesion
    • Lesions classically described as having a "popcorn" appearance on MRI
    • Dynamic behavior on serial imaging, including enlargement, regression, and de novo formation
  • Locations
    • Occurs throughout the central nervous system
    • Brain parenchyma (common)
    • Spinal cord (rare, more common in patients with multiple cavernous malformation syndrome)
    • Extraaxial (rare)
    • Can originate within any venous sinus (cavernous sinus is the most common site)
  • Size
    • Can attain large size before becoming symptomatic
    • Varies from microscopic to giant (>6 cm)
    • Majority fall in the range of 0.5 to 4.0 cm
  • Multiple cavernous malformations
    • Multiple (familial) cavernous malformation syndrome
      • Autosomal dominant, variable penetrance
      • Nonsense, frame-shift, or splice-site mutations consistent with 2-hit model
    • Radiation induced
  • Associated abnormalities
    • Developmental venous anomaly
    • Superficial siderosis
    • Cutaneous abnormalities
    • Café au lait spots
    • Hyperkeratotic capillary-venous malformations
  • Differential diagnoses
    • Arteriovenous malformation
    • Hemorrhagic neoplasm
    • Calcified neoplasm
    • Hypertensive microbleeds
    • Amyloid angiopathy
• Nonenhanced CT
  • Technique
    • Axial 5-mm collimation is typical
    • Reformatted images in coronal/sagittal planes can be made available for difficult cases, although they are generally not needed
  • Findings
    • Negative in up to 50% of cases without recent parenchymal hemorrhage
    • Well-delineated round/ovoid hyperdense lesion, usually <3 cm
    • Partially calcified in some cases
    • No evidence of surrounding hypodense edema or mass effect (unless recent hemorrhage)
• CT angiography
  • Findings
    • Minimal to no enhancement, usually negative (angiographically occult)
• MRI
  • Technique
    • Multiple pulse sequences available to evaluate various tissue properties as well as dynamic properties (flow, velocity)
  • Findings
    • Most commonly identified as a popcorn-like mass lesion with mixed signal on T1- and T2-weighted and FLAIR imaging, reflecting mixed-blood–containing loculations
    • T1 signal
      • Variable depending on blood product evolution
    • T2 signal
      • Variable depending on blood product evolution
      • T2-hypointense hemosiderin rim
      • May see loculations of blood with fluid-fluid levels
    • FLAIR
      • Again, variable signal dependent on age of blood products
      • May reveal perilesional parenchymal edema if recently hemorrhagic
    • T2* GRE, SWI
      • Prominent hypointense blooming from susceptibility artifact
      • Very sensitive for detection, particularly in cases of multiple lesions, familial syndrome
    • DWI
      • Usually normal
    • T1WI C+
      • Minimal or no enhancement (may show associated developmental venous anomaly)
    • MRA
      • Usually normal (angiographically occult)
  • Pitfalls
    • Large acute hemorrhage may obscure more typical features
• Digital subtraction angiography
  • Findings
    • Usually normal (angiographically occult vascular malformation)
    • Extradural lesions can be hypervascular
    • Slow intralesional flow without arteriovenous shunting may be seen
    • Avascular mass effect if large or acute hemorrhage
    • Associated other malformations, most commonly developmental venous anomaly
    • In general, there is no current role for endovascular therapy
• Staging, grading, and classification
  • Zabramski classification: associated with risk of rehemorrhage
    • Type 1 = subacute hemorrhage (hyperintense on T1WI; hyperintense or hypointense on T2WI)
    • Highest risk of rehemorrhage
    • Type 2 = mixed signal intensity on T1WI, T2WI with degrading hemorrhage of various ages
    • Type 3 = chronic hemorrhage (hypointense to isointense on T1WI, T2WI)
    • Type 4 = punctate microhemorrhages (T2*GRE and SWI sequences most sensitive)

For more information, please see the corresponding chapter in Radiopaedia and the Cavernous Malformation chapter within the Brain Tumor Mimics subvolume of The Neurosurgical Atlas.

Contributor: Daniel Murph, MD

DOI: https://doi.org/10.18791/nsatlas.v2.03.03.04.04