| Lacunar infarct | lipohyalinosis of penetrating arteries (hypertension, diabetes) | < 15 mm deep infarcts: basal ganglia, internal capsule, thalamus, pons, corona radiata; classic syndromes (pure motor, pure sensory, ataxic hemiparesis) |
| Small vessel disease (leukoaraiosis) | chronic hypertension, ageing | FLAIR periventricular and deep white matter hyperintensities (Fazekas grade), lacunes, microbleeds (deep: hypertension; lobar: amyloid), enlarged perivascular spaces, atrophy |
| Watershed (border zone) | hypotension, carotid stenosis | cortical (ACA/MCA, MCA/PCA) wedges or internal border zone "string of beads" |
| Cerebral venous thrombosis | postpartum/pregnancy, OCP, dehydration, infection (mastoiditis), thrombophilia, malignancy | NCCT: dense (cord) sign in a cortical vein, dense triangle (dense superior sagittal sinus); CECT/CTV: empty delta sign (non‑enhancing clot surrounded by enhancing dura in the SSS); non‑arterial‑territory venous infarcts, often haemorrhagic, bilateral parasagittal (SSS), temporal (transverse sinus), bilateral thalami (deep venous/straight sinus); MRV/CTV = IOC; SWI blooming clot |
| Global hypoxic–ischaemic injury (arrest, drowning, hanging) | — | diffuse cerebral oedema, loss of grey–white differentiation, reversal sign (cerebral parenchyma darker than white matter/cerebellum), white cerebellum sign (relatively preserved cerebellum/brainstem appears bright), pseudo‑SAH; DWI cortical ribboning/deep grey: poor prognosis |
| Moyamoya | progressive stenosis of the supraclinoid ICA / proximal ACA and MCA; Japanese, also Indian children; Down, NF1, sickle cell, radiation (moyamoya syndrome) | "puff of smoke" collaterals (lenticulostriate) on DSA (gold standard); MRA + MRI (IOC non‑invasive); ivy sign (leptomeningeal collateral FLAIR/post‑contrast hyperintensity); infarcts in children, haemorrhage in adults; Suzuki stages |
| PRES | eclampsia/pre‑eclampsia (commonest), hypertensive encephalopathy, calcineurin inhibitors (cyclosporine, tacrolimus), chemotherapy, renal failure, sepsis | bilateral parieto‑occipital subcortical vasogenic oedema (FLAIR bright, DWI normal/ADC high), also frontal, holohemispheric watershed, cerebellum; usually reversible; can haemorrhage |
| RCVS | postpartum, vasoactive drugs | thunderclap headache, convexity SAH, "string of beads" angiography that reverses |
| CADASIL | NOTCH3 | anterior temporal pole and external capsule white matter lesions |
| Arterial dissection | trauma, neck manipulation | crescentic intramural haematoma (T1 fat‑sat bright), tapered stenosis ("flame"), pseudoaneurysm |