Quadrigeminal plate cistern lipoma

Abstract

Intracranial lipomas are rare benign neoplasms accounting for <0.1% of all primary brain tumours. Most lipomas were incidentally detected by autopsy or computed tomography (CT).These slow growing benign lesions are usually asymptomatic and rarely require surgery. We report the case of a 70-year-old Nigerian woman who presented with persistent headaches following involvement in a road traffic accident 20 days previously. CT demonstrated a quadrigeminal cistern lipoma with no evidence of raised intracranial pressure or compression of neural structures. Her headaches resolved with conservative care. We describe the CT findings with a brief review of the literature.

Background

Intracranial lipomas are rare benign neoplasms, cases of which have not been previously reported from Africa. We report an incidental finding of a lipoma in a 70-year-old head trauma patient. Radiologic findings were not related to the symptoms

Case presentation

A 70-year-old Nigerian widow was referred for cranial computed tomography (CT) scan on account of persistent headaches following a road traffic accident that occurred 3 weeks before presentation. There was associated transient loss of consciousness but no other associated injury. She has hypertension which has been treated with nifedipine for >15 years, with optimal blood pressure control. She has no history of stroke or transient ischaemic attack. She is para-7+0 (all alive), and her last child was born 36 years ago.

The examination revealed an elderly woman in stable general condition and normal cardiovascular, nervous system, respiratory and gastrointestinal systems.

Laboratory results of complete blood count and renal function tests were within normal limits.

A cranial CT revealed a normal cranial vault as well as cerebral and cerebellar hemispheres. The ventricles were not dilated and the sulci were within normal limits for the patient’s age; however, a non-enhancing hypodense ovoid area (measuring 1.3×0.9 cm) was seen within the right half of the quadrigeminal plate cistern (fig 1). The lesion had a negative attenuation value of –10, consistent with fat. A diagnosis of quadrigeminal plate cistern lipoma was made. The patient’s headaches subsided with conservative management; she received counselling and is being followed up at our outpatient clinic.

Figure 1.

(a) Pre- and (b) post-contrast axial computed tomography slices at the level of the third ventricle, showing an ovoid hypodensity of negative attenuation (arrows).

Differential diagnosis

The differential diagnoses include: arachnoid cysts, tectal plate cyst, tectal masses (gliomas), supracerebellar abscess, dermoid and epidermoid cysts, ruptured P4 segment aneurysm of the posterior cerebral artery, and rarely pineal region mass.

Discussion

Intracranial lipomas are benign rare congenital neoplasms. Most are detected as incidental findings in isolated cases, as happened with our patient. Some cases have been associated with other cerebral developmental disorders, particularly in childhood.¹ Lipoma in the quadrigeminal region has previously been reported as lipoma in the quadrigeminal cistern, the quadrigeminal plate, the ambient cistern, the superior vermis, or the superior medullary velum.² The most common sites are the corpus callosum, quadrigeminal/superior cerebellar cistern, suprasellar/interpeduncular cistern, cerebellopontine angle cistern and sylvian cistern.³ Lipomas of the quadrigeminal plate/ambient cistern produce symptoms in about 20% of patients.³ The usual neurological symptoms are intracranial hypertension and hydrocephalus which are successfully treated by shunt operation.⁴

Although rare, most of the reported cases involve children and young adults.⁵ Our patient falls into an uncommonly reported elderly age group, similar to the cases presented by Ambrosette et al.⁶ To the best of our knowledge this is the first report from sub-Saharan Africa.

Outside the quadrigeminal cistern, another relatively uncommon location is the sylvian fissure.^2,7 The majority of patients are asymptomatic; some may present with pressure symptoms as a result of the compressive effect on the brain parenchyma, cranial nerves, vessels or ventricular system, with consequent neurologic deficit, obstructive hydrocephalus or raised intracranial pressure.^4,8 Even though our patient presented with persistent headaches, it appeared unrelated to the lipoma, as no compressive, obstructive or evidence of raised intracranial pressure was seen.

Treatments of intracranial lipomas vary from conservative (as adopted for our patient) to surgical excision, in tumours sufficient to cause a mass effect.² The deep location of these lipomas and their adherence to the sylvian cortex and the branches of the middle cerebral artery make radical removal impossible and dangerous.⁹

Learning points

• Quadrigeminal plate cistern lipoma is rare.

• They are usually asymptomatic, but may cause significant symptoms of mass effect.

• Diagnosis of quadrigeminal cistern lipoma is always definitive on imaging, and therefore histopathological confirmation is practically never required.