Brain
DDx by Finding: The Workstation Quick Reference
Fellowship-level neuroradiology teaching by E. Brooke Schrickel, MD. Open this topic in the interactive reading room →
Core clinical idea
Differentials belong under the FINDING, not the disease. Scan to the imaging finding in front of you and read the short list of what causes it — this is a workstation fast-reference, built for speed, not for completeness.
Bottom line
Find the finding, then run its short differential — fast, not exhaustive.
Differential by finding
Draft fast-reference. Finding-first differentials for the workstation — high-yield starting points, not exhaustive lists.
Restricted diffusion (DWI bright, low ADC)Acute infarct · Abscess (restricts centrally) · Epidermoid · Hypercellular tumor (lymphoma, medulloblastoma, high-grade glioma) · Acute demyelination · CJD (cortical ribbon / deep GM)
Ring-enhancing lesionAbscess (smooth thin rim, central DWI) · Glioblastoma (thick/nodular rim) · Metastasis · Demyelination (open/incomplete ring) · Subacute infarct or hematoma · Radiation necrosis
Multiple cerebral microhemorrhages (SWI)Hypertensive (deep: basal ganglia, thalamus, pons) · Cerebral amyloid angiopathy (lobar / peripheral) · Diffuse axonal injury · Hemorrhagic mets (melanoma, RCC, thyroid, choriocarcinoma) · Cavernomas / familial · Septic emboli, CADASIL, prior radiation
Leptomeningeal (pia-arachnoid) enhancementInfectious meningitis · Leptomeningeal carcinomatosis · Neurosarcoidosis · Vasculitis · Low CSF pressure / post-procedure
Pachymeningeal (dural) enhancementIntracranial hypotension (SIH) · Post-surgical / post-LP · Meningioma or dural metastases · Neurosarcoid / IgG4 / idiopathic hypertrophic pachymeningitis · Chronic subdural collections
Bilateral symmetric basal ganglia signalToxic / metabolic (CO, hypoxic-ischemic, hepatic) · Osmotic (extrapontine myelinolysis) · Deep venous thrombosis (internal cerebral veins) · Wilson disease · CJD · Flavivirus encephalitis; Leigh (peds)
Bilateral mesial temporal T2/FLAIR signalAutoimmune / limbic encephalitis (LGI1, paraneoplastic) · HSV encephalitis (often hemorrhagic, asymmetric) · Status epilepticus (peri-ictal, reversible) · Gliomatosis / infiltrating glioma
Cerebellopontine-angle massVestibular schwannoma (widens IAC, acute angles) · Meningioma (dural base, obtuse angles, tail) · Epidermoid (DWI bright) · Arachnoid cyst (DWI dark) · Metastasis / aneurysm
Suprasellar massAdult: macroadenoma, meningioma, craniopharyngioma, aneurysm, metastasis · Peds: craniopharyngioma, hypothalamic/chiasmatic glioma, germinoma, Langerhans
Multiple enhancing lesions at the gray–white junctionMetastases · Septic emboli / abscesses · Demyelination · Granulomatous (TB, sarcoid, fungal) · Lymphoma
Non-suppressing CSF on FLAIRMeningitis · Subarachnoid hemorrhage · Leptomeningeal tumor · Supplemental O₂ or gadolinium artifact · Slow flow / acute infarct
Restricted diffusion in the splenium of the corpus callosumCLOCCs / MERS (cytotoxic lesion of the corpus callosum) · Seizure or antiepileptic-related · Demyelination · Infection · Trauma (DAI)
Core workstation questions
- Did I clear the sphenoid/temporal skull base for an encephalocele, meningocele, or arachnoid pits — and do I need a thin-section CT to prove it?
- Is the FDG hypometabolism truly mesial temporal, or focal neocortical sparing the mesial lobe?
- Did I look at the amygdala specifically — and if smoothly enlarged, am I about to wrongly suggest tumor?
- Could a subcortical hypothalamic hamartoma be false-localizing this to the cortex?
- Should I prompt an autoimmune antibody panel (LGI1/NMDA), especially if MRI is near-normal with medial-temporal signal?
- Is this true hydrocephalus or atrophy/ex-vacuo/cyst — and did I phrase it as 'volume loss'/'ex-vacuo dilatation'?
- What level is the block, and is there a high-stakes lesion (colloid cyst, entrapment, posterior fossa mass)?
- Posterior fossa cystic-looking lesion: how much vermis is present (Dandy-Walker vs mega cisterna magna/arachnoid cyst)?
Source lectures
- Differential Diagnosis of Temporal Lobe Epilepsy
- Imaging of Hydrocephalus: Differential Diagnosis
- Differential Diagnosis (DDx) – Quick Reference
Educational material for radiology residents and neuroradiology fellows. Nothing here drives individual patient care, and it contains no patient data.