Teaching Case

A 24-year-old female presented with intermittent headaches for one year. Otherwise, she has no other pertinent history.

There is a well-defined hypodense fat attenuating, curvilinear, pericallosal lesion with lobulated surface (Figures 1, 2a and 2b). It extends from the level of the anterior aspect of the body of the corpus callosum and posteriorly to wraps around the posterior part of the corpus callosum with associated local mass effect (Figures 2a and 2b). The posterior part of the corpus callosum appears hypoplastic. The lesion has an extension into the posterior part of the body of the left lateral ventricle (Figures 3a, 3b, 4a and 4b).

Background

Pericallosal lipomas are rare benign congenital fat-containing lesions occurring in the interhemispheric fissure closely related to the corpus callosum, which may be abnormal. It is the most common location for an intracranial lipoma. The exact aetiology of intracranial lipomas is still not well known. Although it has been said that they can originate from an abnormal differentiation of the meninx primitive, a mesenchymal derivative of the neural crest, rather than being absorbed it differentiates into lipomatous tissue. Normally, the resorption occurs between the 8^th and 10^th weeks of gestation.

Clinical Perspective

They are usually asymptomatic. They are detected incidentally during brain imaging for other purposes. However, symptoms like headache, seizures, extremity weakness and memory loss are usually related to other associated anomalies or disorders. Our patient has only intermittent type of headache.

Radiographic Perspective

The diagnosis of pericallosal lipoma can be easily made using CT or MR imaging.

Pericallosal lipomas have two morphological types: tubulonodular and curvilinear:

• Tubulonodular type are usually anterior, they are round or lobular and typically measure > 2cm in diameter. They are also frequently associated with hypogenesis or agenesis of the corpus callosum, frontal lobe deformities, ocular anomalies and calcifications, and thus are more frequently symptomatic as compared to the curvilinear subtype.
• Curvilinear type are usually posteriorly located. They are usually thin, elongated, curve around the margin of the corpus callosum, and usually measure <1cm in diameter. Associated corpus callosum anomalies are usually mild if present.

CT is diagnostic, demonstrating fat density mass ranging from -40 to -120 HU.

MRI is useful in the characterisation of the clear extent of the lesion and other associated anomalies. They follow fat signal in all sequences, i.e., T1 and T2 hyperintense with suppression in fat-saturated sequences, and show no post-contrast enhancement.

Pericallosal lipomas may have extension into the choroid plexus and lateral ventricles, as in our case.

Management Perspective

Pericallosal lipomas usually do not require treatment. Treatment is indicated for those presenting seizures. Surgery is rarely indicated as it has high morbidity. Surgery can be considered in cases of uncontrolled seizure and hydrocephalus.

Written informed consent was obtained from the patient for publication.