A Systematic Search Pattern

The biggest cause of missed findings on neuroimaging is satisfaction-of-search — once you find one abnormality, your eye stops looking. A disciplined search pattern, run identically every time, catches the second lesion (a chronic infarct), the subtle bone lesion (a skull metastasis), the venous sinus thrombosis hiding next to the obvious mass, the SDH on the contralateral side. Use this page as a working checklist until it becomes reflex.

🔹 Bottom Line: A Search Pattern That Works

  • Read by tissue, not by region: every CT/MRI gets a complete pass through skull/scalp → bones → sinuses/mastoids → vessels → CSF spaces (ventricles, cisterns, sulci) → parenchyma (white matter, gray matter, deep gray, brainstem, cerebellum, cord if covered).
  • Compare left vs right systematically at every level.
  • Use the right window/sequence for the right question: don’t try to read brain on bone windows or vice versa.
  • Always read prior comparisons if available — many “new” findings are old.
  • Read the technical bar: motion, coverage, gadolinium given, missing sequences.
  • Then form a single sentence: “[where] + [what signal] + [pattern] + [age]” → narrows differential before you commit.

Checklist — Brain CT (Non-Contrast)

Use brain window for parenchyma; bone window for skull/sinuses; subdural window (wide, e.g. WL 75/WW 250) to catch isodense subdurals.

  1. Scalp + extracranial soft tissues — hematoma, foreign body, laceration, swelling.
  2. Skull (bone window) — fractures, lytic / sclerotic lesions, sutural diastasis, sinus disease.
  3. Sinuses, mastoids, orbits — opacification, air-fluid levels, orbital pathology.
  4. Extra-axial spaces — epidural, subdural, subarachnoid blood; pneumocephalus.
  5. Ventricular system — size, symmetry, blood, mass effect.
  6. Basal cisterns — suprasellar (5-star), perimesencephalic, prepontine. Effacement = elevated ICP / herniation. Hyperdense = SAH.
  7. Sulci — effaced (mass effect / edema / SAH) or prominent (atrophy).
  8. Midline structures — shift? Pineal calcification, choroid plexus calcification, septum pellucidum.
  9. Vessels — hyperdense MCA / basilar (acute thrombus); calcifications.
  10. Gray-white differentiation — loss of insular ribbon, loss of lentiform definition, sulcal effacement (acute ischemia). Score ASPECTS in MCA strokes.
  11. Cortical gray — focal hypodensity (subacute infarct, tumor edema).
  12. Subcortical white matter — leukoaraiosis (chronic small vessel ischemia).
  13. Deep gray nuclei — symmetric vs asymmetric attenuation.
  14. Brainstem + cerebellum — symmetric attenuation, mass effect on 4th ventricle.
  15. Compare prior if available.

Checklist — Brain MRI (Multi-Sequence)

Use each sequence for what it shows best. A complete MRI read passes through every sequence at every level.

By Sequence

  1. T1 (sagittal + axial) — anatomy reference; identify atrophy, hemorrhage subacute (methemoglobin bright), fat, melanin, mineralization, gyriform cortical laminar necrosis.
  2. T2 (axial) — pathology screen; bright = water-rich (edema, gliosis, cyst, CSF, demyelination, infarct subacute/chronic). Dark = iron, calcium, dense fibrous, blood products.
  3. FLAIR (axial ± sagittal/coronal) — same physiology as T2 but suppresses CSF. The workhorse for periventricular and cortical lesions. Detects MS plaques, gliosis, encephalitis, low-grade tumor.
  4. DWI + ADC — diffusion restriction (high DWI + LOW ADC) = cytotoxic edema (acute infarct, abscess, lymphoma, prion, viscous fluid). T2 shine-through is the trap — confirm with ADC darkness.
  5. SWI / GRE / T2* — blood products, calcium, iron, air, melanin (susceptibility / blooming artifact). Microbleeds, CAA, cavernoma, dural sinus thrombus.
  6. Post-contrast T1 — enhancement = BBB disruption or vascular structure. Pattern matters: ring (tumor, abscess, demyelinating), nodular (metastasis, lymphoma), gyriform (subacute infarct, encephalitis), leptomeningeal (carcinomatous, infectious), dural (intracranial hypotension, meningioma, dural metastasis).

By Region (Run This on Every Sequence)

  1. Scalp + skull / bone marrow signal.
  2. Sinuses, orbits, mastoids.
  3. Extra-axial spaces (subdural, subarachnoid, epidural).
  4. Ventricles + cisterns.
  5. Sulci + cortex.
  6. Subcortical + periventricular white matter.
  7. Deep gray nuclei (caudate, putamen, globus pallidus, thalamus).
  8. Internal capsule + corpus callosum.
  9. Brainstem (midbrain → pons → medulla).
  10. Cerebellum (hemispheres, vermis, peduncles, dentate).
  11. Vessels (MRA if obtained; MRV; flow voids on T2).
  12. Cervicomedullary junction + visualized cord.
  13. Pituitary gland + cavernous sinuses + sella.

Window Selection — The Common Errors

What you’re looking for Right window / sequence Common mistake
Brain parenchyma Brain window (CT) / T2 + FLAIR (MRI) Trying to read brain on bone CT or T1 only
Acute SDH (isodense) Wide subdural window CT (WL 75 / WW 250) Missing on standard brain window — looks similar to cortex
Skull fractures, base of skull Bone window (CT) Reading brain window only
Sinus disease, mastoiditis Bone window + soft-tissue (CT) Skipping ENT structures
Acute stroke (hyperacute) DWI + ADC (MRI) Reading T2/FLAIR only → still normal in first ~6 hours
Microbleeds, cavernoma SWI / GRE (MRI) Missing on T1/T2
Subacute hemorrhage T1 (bright methemoglobin) Mistaking for fat or melanin
Periventricular lesions FLAIR (MRI) T2 alone makes CSF and lesion both bright
Leptomeningeal disease Post-contrast FLAIR or T1 Standard T2/FLAIR will miss
Cervicomedullary cord Sagittal T2 + STIR Skipping spinal cord on a “brain MRI”

Two Reads Are Not the Same

  • First pass — anatomy + obvious: identify the lesion, characterize it, localize it.
  • Second pass — systematic checklist: go through every region/tissue regardless of whether you already found something. This catches second pathologies + incidentals.
  • Always compare prior imaging when available — old infarcts, stable masses, postoperative changes, chronic small vessel disease.

Forming Your Sentence

Before committing to an impression, reduce the finding to a single descriptive sentence: [where (location + side + tissue compartment)] + [what (T1/T2/FLAIR/DWI/SWI signal + enhancement)] + [pattern (focal / multifocal / confluent / gyriform / leptomeningeal)] + [age clues (acute / subacute / chronic / mixed ages)].

Examples:

  • “Left mesial temporal hippocampus shows volume loss + T2/FLAIR hyperintensity without DWI restriction or enhancement, no contralateral involvement” → mesial temporal sclerosis (MTS) → epilepsy substrate.
  • “Bilateral parieto-occipital cortical-subcortical T2/FLAIR hyperintensity, vasogenic edema, sparing the deep white matter, no DWI restriction” → PRES.
  • “Bilateral cortical ribbon DWI restriction with pulvinar FLAIR hyperintensity” → CJD (variant).
  • “Multiple ovoid periventricular and juxtacortical FLAIR-hyperintense lesions perpendicular to the ventricles, several with central enhancing rim, no mass effect” → MS, mixed ages.
  • “Ring-enhancing mass right frontal with central DWI restriction, surrounding vasogenic edema” → abscess vs hypercellular tumor (lymphoma); clinical context decides.
  • “Hyperdense vessel sign right M1 with insular ribbon loss and effacement of left frontal sulci” → acute LVO.

🔹 Clinical Relevance: What Gets Missed Most

  • Isodense subdural hematomas: pure subacute hematomas may be exactly the density of cortex on standard brain window — look in subdural windows + look for sulcal effacement / midline shift.
  • Bilateral acute infarcts of different ages: classic embolic pattern. Don’t anchor on the worst lesion.
  • Cerebral venous sinus thrombosis: hyperdense sinus on CT, low T2 signal in sinus + filling defect on MRV. Easy to miss if you don’t look at the sinuses.
  • Carotid / vertebral dissection: crescentic intramural hematoma on fat-sat T1 axial neck. Look in the necks on any stroke MRI.
  • Bone metastasis on a “brain MRI”: T1 dark replacement of fatty marrow.
  • Pituitary apoplexy: enlarged pituitary + heterogeneous T1/T2 ± hemorrhage. Easy miss if you skip the sella.
  • Pineal mass: subtle enlargement vs cyst — look at pineal on every study.
  • Olfactory groove meningioma: anterior cranial fossa, often asymptomatic but pre-frontal. Don’t skip subfrontal anatomy.
  • Cervicomedullary cord pathology: NMO, MS, syrinx, Chiari — visible on sagittal T1/T2 of brain MRI.
  • Mastoiditis / labyrinthitis: in the right clinical context (CN VII, vertigo) — read the mastoids on every MRI.

Pitfalls and Pearls

  • Read the technical bar first: gadolinium given? Motion-degraded? Missing sequences (no DWI = bad for stroke)?
  • Read by sequence, not by region first, then by region: each sequence tells you something different. Cross-check between sequences.
  • If you find one lesion, force yourself to do a second pass on the rest of the study.
  • Subtle is real: insular ribbon loss, asymmetric basal ganglia attenuation, faint hyperdense vessel — these are early stroke signs.
  • Beware of T2 shine-through on DWI: high DWI signal without ADC darkness ≠ restriction (it’s just bright on T2).
  • Beware of artifacts: motion (zipper), susceptibility (dental, frontal sinus, blood), aliasing, chemical shift.
  • Be explicit about location: “left subcortical white matter” not “in the brain.”
  • Be explicit about laterality: scroll through the entire study to confirm the side.
  • Compare prior in a separate viewport: side-by-side, same level, same sequence.
  • Don’t be afraid to call “no acute intracranial finding”: an honest negative is valuable.

References

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  3. Wood BP. Visual expertise. Radiology. 1999;211(1):1-3.
  4. Drew T, Vo MLH, Wolfe JM. The invisible gorilla strikes again: sustained inattentional blindness in expert observers. Psychol Sci. 2013;24(9):1848-1853.