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Intracranial Lipoma

Summary

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  • Rare, congenital, benign tumour composed of mature adipose tissue
  • Usually asymptomatic and incidentally discovered
  • Most commonly located in the pericallosal region

Pathophysiology

  • Believed to result from abnormal persistence and differentiation of meninx primitiva during embryonic development
  • Typically occurs in midline locations, particularly near the corpus callosum
  • Often associated with other congenital malformations, such as corpus callosum agenesis or dysgenesis

Demographics

  • Incidence: 0.1-1.7% of all intracranial tumours
  • No significant gender predilection
  • Can occur at any age, but most commonly diagnosed in young adults

Diagnosis

  • Usually asymptomatic and incidentally discovered on imaging
  • When symptomatic, may present with:
    • Headaches
    • Seizures
    • Neurological deficits (rare)
  • Clinical presentation depends on size and location of the lipoma

Imaging

  • CT:

    • Homogeneous, well-defined, hypodense lesion (-50 to -100 HU)
    • No contrast enhancement
    • Calcifications may be present at the periphery

  • MRI:

    • T1-weighted: Hyperintense signal, similar to subcutaneous fat
    • T2-weighted: Variable signal intensity, often hyperintense
    • FLAIR: Suppressed signal, similar to CSF
    • Fat-suppression sequences: Signal suppression confirming fatty nature
    • No enhancement with gadolinium

  • Additional findings:

    • Associated malformations (e.g., corpus callosum agenesis) should be evaluated
    • Curvilinear calcifications may be present at the periphery

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  • T1-hyperintense lesion in the posterior fossa that suppressed on fat-suppressed FLAIR imaging representing a a fat-filled lesion. With no non-fat components (and no change in 10 years), the lesion is most consistent with a lipoma.
  • The lipoma was associated with a small volume (or partially absent) vermis; this could be due to hypoplasia rather than atrophy.

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  • An incidental fat-containing lesion contained calcification and was associated with a posteriorly deficient corpus callosum.
  • The lesion contained fat based on T1 hyperintensity and suppression of signal of fat suppressed sequences (FLAIR and GRE T2).

Treatment

  • Generally, no treatment is required for asymptomatic lesions
  • Conservative management and follow-up imaging for most cases
  • Surgical intervention is rarely indicated and may be considered in cases of:
    • Intractable seizures
    • Obstructive hydrocephalus
    • Mass effect causing neurological deficits
  • Surgical resection is challenging due to adherence to adjacent neurovascular structures
  • Partial resection or biopsy may be performed for diagnostic confirmation in atypical cases

Differential diagnosis

Differential Diagnosis Differentiating Feature
Dermoid cyst Contains dermal elements; often midline
Epidermoid cyst Diffusion restriction on MRI; irregular margins
Arachnoid cyst Follows CSF signal on all sequences; no fat content
Teratoma Complex mass with mixed tissue types; calcifications common
Lipomatous meningioma Enhances with contrast; dural tail sign
Hamartoma Often associated with cortical dysplasia; may enhance
Low-grade glioma Infiltrative appearance; may enhance; no fat signal
Cholesteatoma Typically in petrous apex; erosive; no fat content
Craniopharyngioma Calcifications; cystic and solid components; no fat signal
Choroid plexus lipoma Located within ventricles; may have calcifications