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Normal Aging Brain


KEY FACTS

Terminology

  • ↓ overall brain volume with advancing age

    • Reflected in relative ↑ cerebrospinal fluid spaces

Imaging

  • Broad spectrum of “normal” on imaging in elderly patients

  • “Successfully aging brain”

    • Smooth, thin, periventricular, high signal rim on FLAIR is normal

    • White matter hyperintensities (WMHs) absent/few

  • Decreased total brain volume

    • Selective atrophy of white matter (not gray matter) predominates

  • WMHs

    • ↑ In number/size after 50 years

    • Approximately universal after 65 years

  • GRE/SWI

    • Increasing mineralization of basal ganglia with age

    • Microbleeds are not characteristic of successful aging brain

  • Age-related shift from anterior to posterior cortical metabolism

Top Differential Diagnoses

  • Mild cognitive impairment

  • Alzheimer disease

  • Sporadic subcortical arteriosclerotic encephalopathy

  • Vascular dementia

  • Frontotemporal lobar degeneration (Pick disease)

Clinical Issues

  • WMHs correlate with age, silent stroke, hypertension, female sex

Diagnostic Checklist

  • Cannot predict cognitive function from CT/MR

    • Imaging only roughly correlates with cognitive function

    • Significant overlap with dementias

Axial graphic depicts a normally aging brain in an 80-year-old patient. Note the widening of sulci and ventricles in the absence of any brain parenchymal abnormalities.

Axial NECT demonstrates mild sulcal enlargement and mild ventriculomegaly in a 70-year-old patient. The white matter appears completely normal, without periventricular hypodensities or white matter lacunar infarcts.

Axial SWI in a 67-year-old woman shows striking hypointensity in the globi pallidi
with less prominent hypointensity in the putamina
due to iron deposition.

Axial FLAIR MR in a 79-year-old man shows enlargement of ventricles and sulci due to age-related volume loss. Smooth, thin, periventricular hyperintense rim
and subtle hyperintensity in the splenium
of corpus callosum are common and normal.

TERMINOLOGY

Definitions

  • ↓ overall brain volume with advancing age

    • Reflected in relative ↑ CSF spaces

IMAGING

General Features

  • Best diagnostic clue

    • “Successfully aging brain”

      • –

        Thin, periventricular, high signal rim

      • –

        Absent/few white matter hyperintensities (WMHs)

      • –

        Mild shrinkage of selected cerebellar regions

  • Location

    • Selective atrophy of white matter (WM) predominates, not gray matter (GM)

    • Striatum (primarily caudate nucleus, putamen)

  • Size

    • Decreased total brain volume

    • Absolute striatal size

      • –

        Caudate decreases linearly with age

      • –

        Putamen remains relatively stable

    • Relative striatal size (ratio of absolute size to total brain volume)

      • –

        Caudate remains relatively stable

      • –

        Putamen increases linearly with age

  • Morphology

    • Brain tissue ↓, CSF volume ↑

      • –

        Reflects overall WM volume loss > focal WMHs

      • –

        Rounded appearance of dilated ventricles, sulci ↑

    • Strong correlation between WM volume and CSF volume: Measure of overall brain atrophy

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