Lipoma

KEY FACTS

TERMINOLOGY

• Intracranial lipoma (ICL)

• Mass of mature adipose tissue (congenital malformation,

not true neoplasm)

IMAGING

• Well-delineated lobulated extraaxial mass with fat

attenuation/intensity

○ CT: -50 to -100 Hounsfield units (HU) (fat density); Ca++

varies from none to extensive

○ MR: Hyperintense on T1WI (becomes hypointense with

fat suppression); may encase vessels and cranial nerves;

often occurs with corpus callosum dysgenesis

• 80% supratentorial

○ 40-50% interhemispheric fissure (over corpus callosum;

may extend into lateral ventricles, choroid plexus)

○ 15-20% suprasellar (attached to infundibulum,

hypothalamus)

○ 10-15% tectal region (usually inferior colliculus/superior

vermis)

• 20% infratentorial

○ Cerebellopontine angle (may extend into internal

auditory canal, vestibule)

TOP DIFFERENTIAL DIAGNOSES

• Teratoma: Locations similar to lipoma; tissue from all 3

embryonic germ layers

CLINICAL ISSUES

• Most are asymptomatic; some present with seizures or

headaches mainly affecting interhemispheric fissure

DIAGNOSTIC CHECKLIST

• When in doubt, use fat-saturation sequence

• Could high signal on T1WI be due to other substances with

short T1 (e.g., subacute hemorrhage)

• Beware: Lipoma can mimic intracranial air on nonenhanced

CT (use bone windows to distinguish)

(Left) Coronal graphic shows

callosal agenesis with a bulky

tubulonodular

interhemispheric lipoma ﬊

that encases the arteries ﬉

and extends into the lateral

ventricles ﬈. (Right) Sagittal

T1WI MR shows a rather thin

curvilinear interhemispheric

lipoma in a 9-month-old

infant. Note that the

hyperintense lipoma ſt is

thicker posteriorly than

anteriorly. It wraps around the

back of the corpus callosum

and extends beneath the

corpus ﬇ into the velum

interpositum.

(Left) Sagittal T1WI MR in a

neonate shows a large,

tubulonodular,

interhemispheric lipoma ﬇

dorsal to a wedge-shaped

callosal remnant (absent body,

splenium) ſt. (Right) Axial

T2WI FS MR in the same

patient shows the lipoma ﬈

as hypointense and lying

between the 2 cerebral

hemispheres. The lipoma

extends through the choroidal

fissures into the lateral

ventricles ﬉, where it is in the

stroma of the choroid

plexuses.

Brain: Pathology-Based Diagnoses: Malformations,

Trauma, and Stroke

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