Clinical History
A 22-year-old man presented with hearing impairment.
Imaging Findings
A brain MRI was performed. Sagittal T1W images demonstrated a high signal curvilinear mass situated around the genu, body and splenium of the corpus callosum (Fig. 1a). The mass showed high signal on both T1W (Fig. 1a) and T2W (Fig. 2) images and low signal on fat saturated pulse sequences (Fig. 1b, Fig. 3), consistent with a lipoma. The sagittal images showed that the splenium of the corpus callosum was smaller than normal and the rostrum was absent (Fig. 1, 3).
Discussion
Intracranial lipomas are rare developmental lesions of the central nervous system, which are usually asymptomatic and discovered incidentally. They mainly occur in the region of the corpus callosum and the pericallosal cistern, accounting for up to 65% of all intracranial lipomas [1]. Other characteristic regions for which intracranial lipomas have a predilection are: quadrigeminal cistern, suprasellar cistern, cerebellopontine angle and sylvian fissure. Pericallosal lipomas (PCL) occur in the interhemispheric fissure closely related to the corpus callosum and approximately 48% of them are associated with partial or complete agenesis of the corpus callosum. Other associated anomalies include; additional lipomas at other sites, hypoplastic fornix, absent septum pellucidum, spina bifida, myelomeningocele, frontal bone defects, encephaloceles, heterotopic gray matter, agenesis of the vermis, and cleft lip [2].
The most frequent clinical presentation of PCL is seizure, or it can be found as an incidental finding in the evaluation of headache, dizziness, or head trauma [3].
The diagnosis of PCL can easily be made on MRI, which shows a homogeneous well-circumscribed lesion displaying the characteristic short T1 and T2 signal of fat. On fat saturated sequences, the mass is typically of low signal. MRI, particularly T1W sagittal acquisitions, exquisitely demonstrate the anatomic relationship between the lipoma and the adjacent dorsal surface of the corpus callosum. They may vary in size from less than a centimetre to a large mass [2]. Based on imaging, they can be grouped into two distinct types: tubulonodular and curvilinear. Tubulonodular PCLs, the more common variety, are rounded or lobular masses usually situated anteriorly and measuring more than 2 cm. Curvilinear PCLs are thin masses situated along with the callosal margin usually situated posteriorly and measuring less than 1 cm in thickness [2, 4]. The differential diagnosis includes the masses containing fat: intracranial dermoid, intracranial teratoma and neoplasms which may show lipomatous transformation including PNET, ependymoma, and glioma.
Intracranial lipomas are asymptomatic in most cases. They usually do not require treatment even when they are associated with symptomatic malformations. Surgical resection has relatively high morbidity with little benefit. If present, the treatment of hydrocephalus or seizures is necessary [5].
Differential Diagnosis List
Pericallosal lipoma associated with corpus callosum dysgenesis
Intracranial dermoid
Intracranial teratoma
Final Diagnosis
Pericallosal lipoma associated with corpus callosum dysgenesis
