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Hypotensive Cerebral Infarction


KEY FACTS

Terminology

  • Hypotensive cerebral infarction (HCI)

    • Infarction resulting from insufficient cerebral blood flow (CBF) to meet metabolic demands (low-flow state)

    • 2 types of border zone or watershed infarcts

      • –

        Border zone between major arterial territories

        • □

          Typically at cortex, gray matter (GM)-white matter (WM) junctions

      • –

        Border zone between perforating arteries

        • □

          Typically in deep WM

Imaging

  • Best imaging tool

    • MR with DWI/ADC ± MR perfusion

  • Cortical border zone

    • Between major arterial territories

    • Typically at GM-WM matter junctions

    • Hypodensity between vascular territories

  • WM matter border zone

    • Between perforating arteries

    • Typically in deep WM (centrum semiovale)

    • ≥ 3 lesions

    • Linear AP orientation → string of pearls appearance

    • If unilateral, look for stenosis of major vessel

  • Imaging recommendations

    • MR + GRE, DWI, MRA (both cervical, intracranial)

    • ± pMR (may show ↓ CBF to affected areas)

    • NECT, pCT, CTA if MR not available

    • CTA/DSA > MRA for determining total vs. near occlusion of internal carotid artery

Top Differential Diagnoses

  • Acute embolic cerebral infarction(s)

  • Arteriosclerosis (“small vessel disease”)

  • Posterior reversible encephalopathy (PRES)

  • Vasculitis

  • Pseudolaminar necrosis (other causes, e.g., Reye, lupus, etc.)

T1WI show 2 watershed (WS) zones. External WS zones are depicted in turquoise. Yellow lines indicate internal (deep white matter) watershed zones between perforating arteries and major territorial vessels.

Axial gross pathology shows classic external (cortical) watershed infarcts
from cerebral hypoperfusion. The patient survived several days, allowing for petechial hemorrhagic transformation to occur.

Axial FLAIR MR in a patient with transient global hypoperfusion secondary to a hypotensive episode shows multifocal hyperintensities along the cortical WS zone
. Changes are most severe at the confluence of the anterior cerebral, posterior cerebral, and middle cerebral artery cortical vascular territories
.

DWI in the same patient shows corresponding areas of restricted diffusion in the cortical WS zones bilaterally
, most severe at the trivascular confluence
. The diagnosis was hypotensive WS cerebral infarctions.

TERMINOLOGY

Abbreviations

  • Hypotensive cerebral infarction (HCI)

Synonyms

  • Border zone or watershed infarction

Definitions

  • Infarction resulting from insufficient cerebral blood flow (CBF) to meet metabolic demands (low-flow state)

IMAGING

General Features

  • Best diagnostic clue

    • Restricted diffusion on DWI/ADC

  • Location

    • 2 types

      • –

        Border zone between major arterial territories

        • □

          Typically at gray-white matter junctions

      • –

        Border zone between perforating arteries

        • □

          Typically in deep white matter

    • Supratentorial structures in severe perinatal asphyxia

    • Bilateral abnormalities in global hypoxic-ischemic (HIE) events (with underlying vascular stenoses + relative hypoperfusion) can lead to unilateral presentations

  • Morphology

    • Cortically based, wedge-shaped abnormality at border zone between vascular territories

    • Deep white matter (WM) watershed with rosary or string of pearls/beads appearance

      • –

        Multiple round foci in linear orientation within centrum semiovale

    • Pseudolaminar necrosis = curvilinear, gyriform, cortical T1 shortening

    • Diffuse supratentorial abnormality (global HIE)

CT Findings

  • NECT

    • Major arterial border zone infarcts

      • –

        Hypodensity at gray-white matter junction between vascular territories

      • –

        Severe (i.e., global HIE)

        • □

          Usually significant hemodynamic compromise (i.e., hypotension)

        • □

          Most all supratentorial gray-white matter junctions effaced

        • □

          Basal ganglia (BG), thalami affected

        • □

          Occasionally isolated to BG ± hippocampus

      • –

        “White” cerebellum (sometimes called cerebellar reversal sign)

        • □

          Cerebellum appears relatively hyperdense compared to supratentorial hypodensity

    • Deep WM watershed infarcts

      • –

        ≥ 3 deep WM lesions within centrum semiovale

      • –

        String of pearls appearance

        • □

          Linear orientation in AP (front to back) direction

        • □

          Parallel to lateral ventricle

        • □

          Can resemble multiple emboli

      • –

        Can be unilateral

        • □

          Look for major vessel stenosis on side of infarcts

      • –

        Bilateral if bilateral vessel stenoses ± significant hemodynamic event

  • CECT

    • Enhancement in subacute HCI

  • CTA

    • Use to determine complete vs. near-complete ICA occlusion

  • CT perfusion

    • CBF ↓ in affected areas

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