Intracranial subarachnoid fat arising from a comminuted sacral fracture

Intracranial Transthecal Fat Migration After a Sacral Fracture: 2 Case Reports

BACKGROUND The presence of fat droplets within the subarachnoid space is an uncommon finding, which is almost exclusively associated with a ruptured dermoid cyst. In a trauma setting, transthecal migration of fat droplets is an extremely rare occurrence. We present 2 case reports of intracranial transthecal migration of fatty bone marrow after sacral fractures. CASE REPORT Both patients presented to the Emergency Department (ED) after falls from a standing height. The first patient, an 84-year-old woman, suffered a stable sacral fracture extending into a large meningeal cyst within the right S2 foramen. Her initial neurological assessment and computed tomography (CT) of the head were unremarkable. As the fracture did not require surgical treatment, she was discharged home and prescribed bed rest, analgesics, and venous thromboembolism prophylaxis. Three days after the injury, she was readmitted to the ED with a mild headache, dizziness, and an episode of nausea and vomiting. A follow-up head CT revealed fat droplets in the subarachnoid space and lateral ventricles. After successful symptomatic treatment, she was discharged home in good general condition. The second patient, a 60-year-old man, underwent a head CT for a scalp hematoma, which revealed fat droplets in the 3rd ventricle and right lateral ventricle. The pelvic CT revealed a large sacral meningeal cyst with microfractures in its wall. He was discharged home on the same day and prescribed bed rest and analgesics. CONCLUSIONS The detection of intracranial intrathecal fat droplets in association with a specific trauma mechanism should initiate the search for a sacral fracture.

Imaging of intracranial fat: from normal findings to pathology

The presence of intracranial adipose tissue is often overlooked, although it may be detected in different physiological (dural sinuses or falx deposition of fat) and pathological (lipoma, dermoid cyst, subarachnoid fat dissemination) conditions. In this review, we illustrate various scenarios in which radiologists and neuroradiologists may encounter intracranial fat, providing a list of differential diagnosis.

Intracranial subarachnoid fat and hemorrhage secondary to sacral fracture with spondylopelvic dissociation

We describe a case of fat droplets and blood in the cerebral subarachnoid space secondary in a patient with a complex sacral fracture without associated cranial trauma, a few days after admission. To our knowledge, there is only one published case with similar findings and without any other underlying lesion as cause. We explain the differences in the mechanism of production between this direct fat embolism and brain fat embolism syndrome, which is an intravascular embolism with different radiological appearance. The most important features of sacral fracture with spondylopelvic dissociation are described. Finally, this entity should be taken into account in the differential diagnosis of the few causes of fat in the subarachnoid space. In the context of high-energy trauma fractures of the sacrum or spine must be ruled out as a potential cause of this uncommon intracranial finding.