Introductory Neuroimaging: What you need to know at 3 am And some cool stuff. . . Kathleen Tozer, MD

Outline Choosing a study Normal anatomy Trauma Ischemic stroke Aneurysm

Outline Choosing a study Normal anatomy Trauma Ischemic stroke Aneurysm

Which study? Acute change For acute mental status change, first study is ALWAYS noncontrast head CT Brain MR: Stroke protocol (noncontrast) ICH protocol (with contrast) Tumor protocol (with contrast)

Which study? Vascular CTA: MRA: Neck: Aortic arch through Circle of Willis. Head: Circle of Willis only MRA: Brain: noncontrast Neck: without and with contrast.

Regarding contrast: Iodinated contrast: GFR > 60: GFR < 60: in the clear GFR < 60: If acute, tread cautiously, especially if <30 Hydration, mucomyst, Sodium bicarb protocol Decrease dose, Visipaque ESRD: Coordinate with hemodialysis

Regarding contrast: Gadolinium contrast: GFR > 60: GFR 30-60: in the clear GFR 30-60: weigh risks. Consider noncontrast study first. Multihance GFR < 30: CONTRAINDICATED due to risk of NSF (nephrogenic systemic fibrosis). Try noncontrast. Consult radiology for alternative studies.

Hounsfield Units (HU) CT density scale: Air = -1000 Fat = -120 Water = 0 Muscle = +40 Blood clot = +65 Bone = +1000 Metal >> +1000

Outline Choosing a study Normal anatomy Trauma Ischemic stroke Aneurysm

Normal Anatomy Note utility of CT scout view--much easier to comprehend, in this instance

Normal Anatomy Note utility of CT scout view--much easier to comprehend, in this instance

Normal Anatomy Note utility of CT scout view--much easier to comprehend, in this instance

Normal Anatomy Note utility of CT scout view--much easier to comprehend, in this instance

Acute Head CT Checklist Midline Shift Mass Effect Density CSF Spaces Vascular Territories Intra-/Extra-axial Herniation Checklist of pathological changes

Outline Choosing a study Normal anatomy Trauma Ischemic stroke Aneurysm

Epidural Hematoma Injury to epidural vessel Lentiform shape Arterial bleeding Lentiform shape Does not cross sutures May cross falx or tentorium Look for: FRACTURE RAPID EXPANSION

Acute Subdural Hematoma Injury to bridging vessel Venous Crescent shaped May cross sutures Does not cross falx or tentorium Does not enter sulci Watch for: MASS EFFECT SLOW EXPANSION

Chronic Subdural Hematoma HYPODENSE (blood degradation) MIXED (Acute-on-chronic)

Note midline shift to the left!

Isodense Subdural Hematoma Coagulopathy Anemia Evolution of blood products Note midline shift to the left! Look for: Sulcal Effacement Subtle Mass Effect

Subarachnoid Hemorrhage Sulci Cisterns Ventricles Trauma lateral convexities Aneurysm basal cisterns Interpeduncular Cistern most sensitive

Cerebral Contusion Intraparenchymal “Coup-Contrecoup” Look for: Blow to head Sudden deceleration Brain impacts inner table (contralateral side) Look for: Scalp contusion Halo of edema

Subcortical Injury Shear-Strain forces “Tip of the iceberg” Penetrating vessels Axonal injury “Tip of the iceberg” Consider MRI Neurological deficits may be out of proportion to degree of injury visible on CT

MRI: Diffuse Axonal Injury GRE sequence is useful for CT-occult blood degradation products, although other substances can mimic hemosiderin

Diffuse Cerebral Edema Grey-white interface often obscured Sulcal effacement Focal subtypes: Vasogenic Extracellular White matter > GM Cytotoxic Intracellular Grey matter > WM

Outline Choosing a study Normal anatomy Trauma Ischemic stroke Aneurysm

Stroke

Acute Ischemia-Infarction Subtle HYPODENSITY Vascular distribution Loss of grey-white margin CT often NEGATIVE Early CT signs “Hyperdense MCA” “Insular ribbon” Role of CT: EXCLUDE BLEED MRA or CTA useful DSA for intervention Early treatment may improve outcome

Diffusion-MRI: Acute Infarct Note abnormality conforms to a vascular distribution within the brain--right MCA territory

Case 1

Acute facial droop, hemiparesis

Case 1

Case 1 CTA

Angio

Post intervention

Watershed Infarction End

15 hours later

Anoxic brain injury Loss of Gray-White Progresses with worsening edema PseudoSAH Hydrocephalus Cisterns compressed

Subacute Infarction 2-14 days out Hypodensity ENHANCEMENT Hemorrhagic transformation

MRI: Enhancing Subacute Infarct

Chronic Infarction VOLUME LOSS Hypodensity Ex vacuo dilatation encephalomalacia

Dural Sinus Thrombosis Occlusive thrombosis Subtle early signs Bilateral infarcts Hemorrhages CTV or DSA Filling defect MRI/MRV

Outline Choosing a study Normal anatomy Trauma Ischemic stroke Aneurysm

Aneurysmal SAH Sudden severe headache HYPERDENSE CSF spaces Location Interhemispheric: ACoA Sylvian: MCA HYDROCEPHALUS, VASOSPASM and ISCHEMIA MUST find the aneurysm! DSA, CTA and/or MRA

Saccular Aneurysm

Fusiform Aneurysm

Active Re-bleeding

Ruptured Aneurysm

Intracerebral Hemorrhage Hypertension Most common Characteristic Locations IF LOBAR BLEED: SEARCH for underlying cause! MRI/MRA/MRV DSA or CTA Repeat imaging if negative initially Look for: EXPANSION UNDERLYING LESION

MRI: Blood Products GRE “blooming” effect

MRI: Hemorrhagic Tumor Note enhancement

Parenchymal Hemorrhage with Ventricular Extension

MRI Flow Voids: AVM