Quadrigeminal plate cistern lipoma presenting with seizures in a child.

Intracranial lipomas are neither hamartomatous nor neoplastic lesions. They result from abnormal persistence and development of meninx primitiva.[1] They are extremely rare and are seen in around 0.08-0.2% of all autopsy cases and constitute only 0.06-0.3% of incidental lesions.[2] Rarely, they have been associated with seizures, headache, and behavioral disturbances.[3] These lesions are managed conservatively owing to their indolent course.

A 3-year-old child from rural background was referred for CT scan of head for evaluation of single episode of generalized tonic-clonic seizures 1 day back. There was associated loss of consciousness and postictal confusion. The patient denied any history of prior similar episodes, and his neurological development was normal. On examination, the patient was in overall good general health and systemic examination of respiratory, cardiovascular, and nervous system revealed no anomaly. Routine hematological investigations were within normal limits.

Axial non-contrast CT scan of the head revealed a well-defined lobulated hypodense lesion, with smooth margins and showing fat attenuation (CT value of -30 HU), in the quadrigeminal plate cistern [Figure 1]. There was no evidence of calcification within the lesion, and the lesion exhibited no enhancement on contrast administration. No other abnormality was detected.

Figure 1

(a) Axial non-contrast CT scan of the patient showing a well-defined lobulated hypodense lesion, with no evidence of calcification and showing smooth margins and fat attenuation, in the quadrigeminal plate cistern. (b) On contrast administration, there is no enhancement of the lesion

A provisional diagnosis of quadrigeminal plate lipoma was made, and patient was treated with oral anti-epileptic drugs. The patient is on regular follow up for 1 year, with no evidence of progression of symptoms.

Meckel was the first to report intracranial lipomas, way back in 1818.[1] Since then, intracranial lipomas have being routinely described in literature as incidental lesions. Yilmaz et al. reported that these lesions were occasionally associated with headache, epilepsy, and neurological dysfunction.[3] Lipomas of the quadrigeminal plate have been associated with obstructive hydrocephalus due to compression of cerebral aqueduct.[4] These lesions are usually seen in children and young adults, but to the best of our knowledge, this is the youngest case of a child with quadrigeminal plate cistern lipoma.

The most common location of these lesions is pericallosal, where 45% of these lesions are found. Other uncommon locations include suprasellar cistern, quadrigeminal plate cistern, cerebellopontine angle, and the sylvian fissure. On CT scans, they appear as well demarcated non-enhancing lesions with fat attenuation. The lesions in pericallosal location may show calcifications. On MRI, they appear hyperintense on both T1W and T2W sequences and show signal drop on fat saturated images. The common differentials of these lesions on imaging include dermoid and epidermoid cysts, tectal plate cysts, arachnoid cysts and, rarely, lipomatous transformation of neoplasms like DNET and tectal gliomas.

An association of these lesions has been described with neurocutaneous syndromes like encephalocraniocutaneous lipomatosis, epidermal nevus syndrome, or congenital infiltrating lipomatosis.[5] Quadrigmenial plate lipomas have also been associated with hypoplasia of inferior colliculus. Vascular abnormalities including kinking and narrowing along with arteriovenous malformations have also been linked with intracranial lipomas.[6]

These lesions are usually managed conservatively[7] as surgical removal of these lesions is difficult owing to their close contiguity with adjacent neurovascular structures. Attempts of surgical evacuation often result in marked neurological deterioration.[8] In conclusion, quadrigeminal plate lipomas are extremely rare entities with varied clinical presentations. A thorough knowledge of the imaging features is essential to rule out other conditions as it is usually asymptomatic and rarely requires aggressive management.