Solitary Hypodense Parenchymal Lesion
Anne G. Osborn, MD, FACR
DIFFERENTIAL DIAGNOSIS
Common
Cerebral Contusion
Cerebral Ischemia-Infarction, Acute
Cerebral Infarction, Subacute
Cerebral Infarction, Chronic
Glioblastoma Multiforme
Anaplastic Astrocytoma
Metastasis
Oligodendroglioma
Less Common
Diffuse Astrocytoma, Low Grade
Pilocytic Astrocytoma
Cerebritis
Encephalitis
Intracerebral Hematoma (Resolving)
Thrombosis, Cortical Venous
Rare but Important
Multiple Sclerosis
ADEM
Tuberculoma
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
Definition
Includes solitary focal hypoattenuating parenchymal lesions that are hypodense to brain but hyperdense compared to CSF
Excludes cysts, cyst-like lesions
Excludes multifocal, diffuse/confluent white matter diseases
History key
Trauma (contusion, resolving hematoma)?
Sudden (e.g., stroke) vs. gradual onset (tumors, infection, demyelinating diseases)
Effect of age on differential diagnosis
Child
Diffuse astrocytoma, low grade
ADEM
Adult
Multiple sclerosis
ADEM
Glioblastoma multiforme
Anaplastic astrocytoma
Metastasis
Both
Contusion
Infection (cerebritis, encephalitis)
Cerebral ischemia-infarction (adult > child)
Helpful Clues for Common Diagnoses
Cerebral Contusion
Cortical/subcortical hypodensity
± Petechial hemorrhages
Multifocal > solitary, confluent
Look for
Overlying scalp swelling (coup) or opposite lesion (contrecoup)
Adjacent traumatic subarachnoid hemorrhage
Lesions “bloom” (become more prominent) with time
Cerebral Ischemia-Infarction, Acute
Look for dense MCA, dot signs
Subtle effacement of gray-white interfaces
Insular ribbon sign
Hypodense/“smudged” basal ganglia
Cerebral Infarction, Subacute
Hypodensity increases
Mass effect increases
Wedge-shaped hypodensity in vascular distribution
Involves both gray, white matter; extends to cortex
Cerebral Infarction, Chronic
Gliotic, encephalomalacic brain
Hypointense on FLAIR but often has hyperintense borders
Glioblastoma Multiforme
Glioblastoma multiforme (GBM) usually tumor of middle-aged, older adults
95% central necrosis, thick enhancing rind, edema
Ca++ rare; gross hemorrhage common
Anaplastic Astrocytoma
Poorly-delineated, infiltrating
Ca++, hemorrhage less common
If any enhancement, suspect GBM
Metastasis
Iso- to hypodense mass, variable edema
Enhances (solid, ring, nodular)
Oligodendroglioma
Hypodense cortical/subcortical mass
50% calcify
Enhancement variable
Helpful Clues for Less Common Diagnoses
Diffuse Astrocytoma, Low Grade
Hypodense, nonenhancing
2/3 supratentorial (hemispheres)
1/3 posterior fossa (brainstem, cerebellum)
Pilocytic Astrocytoma
Cerebellum = cyst + nodule
Hypothalamus/optic pathway
Lobulated hypodense mass
Enhances strongly, uniformly
Cerebritis
First, earliest stage of abscess formation
Poorly marginated hypodense mass
Enhancement none or minimal
Encephalitis
Mostly viral
General imaging findings = hypodense mass, variable enhancement
Herpes encephalitis most common
Limbic system predilection (both temporal lobes, cingulum, subfrontal cortex)
Cortex, subcortical white matter
Enhancement, hemorrhage absent in early stage
MR with FLAIR most sensitive
Intracerebral Hematoma (Resolving)
Hypodense to brain but hyperdense to CSF
May show ring enhancement
MR shows evidence for resolving hemorrhage
Thrombosis, Cortical Venous
Can be solitary or multiple
Can occur with or without associated dural sinus occlusion
May show “cord sign” (thrombosed cortical vein)
Hypodense cortex/subcortical white matter lesion(s)
Patchy petechial hemorrhage common
Do CECT/CTV
MR
Include T1 C+
Do T2* (GRE/SWI), look for blooming clot in thrombosed cortical veinRelated posts:
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