Multiple Hypointense Foci on GRE/SWI

Nancy J. Fischbein, MD

DIFFERENTIAL DIAGNOSIS

Common

Less Common

Vascular Malformations
- Cavernous Malformation, Multiple
- Multiple Micro-Arteriovenous Malformations
Infections
- Neurocysticercosis
- Tuberculomas
- Fungal Diseases
- Septic Emboli
Vasculitis
Vasculopathy
Radiation and Chemotherapy
- Radiation-Induced Telangiectasia
- Mineralizing Microangiopathy

Rare but Important

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

NECT may help with differential diagnosis
- Air black on CT, calcification (Ca++) dense, hemosiderin staining not appreciable
GRE/SWI susceptibility generally greater for hemosiderin than for Ca++
Distribution of GRE/SWI hypointensities
- CAA typically peripheral/subcortical, while hypertension (HTN) changes are central
- Subarachnoid involvement suggests pneumocephalus, cysticercosis
Gadolinium enhancement
- Neoplasm & infection generally enhance, whereas CAA, HTN changes, DAI do not

Helpful Clues for Common Diagnoses

Chronic Hypertension
- Increased prevalence of GRE/SWI hypointensities related to “microbleeds”
- Predominate in basal ganglia, thalami, brainstem (esp. pons), cerebellum
Cerebral Amyloid Angiopathy (CAA)
- Usually affects age > 65 years unless familial
- Lesions predominantly juxta-cortical, cerebellar
- Relative sparing of deep gray nuclei, brainstem
- May coexist with HTN changes & Alzheimer disease
- Often accompanied by moderate to severe small vessel ischemic changes in hemispheric white matter (WM)
Diffuse Axonal Injury (DAI)
- Classic triad: Lobar WM, corpus callosum, dorsolateral brainstem
- History of severe head injury with acceleration-deceleration mechanism
- Often associated with cerebral contusions, EDH/SDH, SAH, IVH
Metastases, Parenchymal
- Classically hemorrhagic mets: Melanoma, thyroid carcinoma, renal cell carcinoma, choriocarcinoma
- Lung & breast cancer so prevalent, account for many cases of hemorrhagic metastasis
- Hemorrhage may be seen at presentation or following treatment
Pneumocephalus
- Obvious on CT, can be confusing on MR
- Often high signal edge surrounding low signal center, suggesting artifact
- Seen post-trauma, post-surgical, CSF leak, spinal intervention

Helpful Clues for Less Common Diagnoses

Vascular Malformations
- Cavernous Malformation, Multiple
  - Occur both supra- & infratentorially
  - Autosomal dominant inheritance pattern
  - Not associated with developmental venous malformation
- Multiple Micro-Arteriovenous Malformations
  - Occur in setting of HHT
  - Associated with vascular shunts & AVMs in other organ systems
Infections
- Neurocysticercosis
  - Stage 4 lesions (chronic, healed) present as punctate & rounded Ca++ on CT
  - Variable hypointensity on GRE
- Tuberculomas
  - Active lesions: Often central intermediate SI on T2WI
  - Treated lesions: Often calcified, GRE/SWI hypointense
  - Often present with TB meningitis
- Fungal Diseases
  - Invasive fungal infection is associated with multifocal brain parenchymal hemorrhage
  - Usually seen in severely immunocompromised patients
- Septic Emboli
  - Associated with multifocal infarction, often hemorrhagic
  - May result in microabscesses
Vasculitis
- Brain microhemorrhage may be due to primary or secondary CNS vasculitis
Vasculopathy
- Small vessel vasculopathy (e.g., CADASIL or sickle cell disease) is associated with cerebral microbleeds & hemorrhage
Radiation and Chemotherapy
- Brain radiation is associated with formation of multiple telangiectasias
  - Distribution conforms to radiation port
  - Increase over time
- Chemotherapy
  - In combination with radiation may lead to mineralizing microangiopathy
  - Dense Ca++ on CT, variable loss of signal on GRE/SWI