Intracranial transthecal subarachnoid fat emboli and subarachnoid haemorrhage arising from a sacral fracture and dural tear

Abstract

ABSTRACT. We present the case of a 28-year-old man with an unusual aetiology of lipid-dense material in the subarachnoid space. CT of the head at presentation was normal. MRI of the spine revealed a defect in the dura at L5/S1, with avulsed left L5 and S1 nerve roots. Haematoma and marrow fat were observed in close relation to the dural tear adjacent to the sacral fracture. Head CT and MRI subsequently demonstrated new lipid-dense material and haemorrhage in the subarachnoid space after sacral instrumentation, presumably owing to transthecal displacement of fatty marrow. The presence of fat droplets within the subarachnoid space is an unusual finding and is most commonly the sequelae of a ruptured dermoid. We present a unique case with CT and MRI that demonstrates the development of subarachnoid fat emboli and subarachnoid haemorrhage secondary to pelvic trauma. A sacral fracture with an adjacent dural tear and nerve root avulsion is the putative source of the subarachnoid fat and blood. Case reportA 28-year-old man presented to the emergency room after being struck by a high-speed vehicle as a pedestrian. He suffered multiple orthopaedic injuries, including an open-book pelvic fracture as well as upper and lower extremity fractures. Pertinent physical examination findings included the absence of left ankle dorsiflexion, plantar flexion, inversion and eversion. An absence of light touch and pinprick sensation in the left L5 and S1 dermatomes was also noted.At presentation, CT of the head did not demonstrate any calvarial or skull base fracture or other intracranial abnormalities (Figure 1a). Specifically, neither subarachnoid haemorrhage nor subarachnoid fat droplets were present. CT of the pelvis demonstrated a transforaminal left sacral fracture and superior and inferior left pubic rami fractures. A mixed fat and blood attenuation collection was also seen within the left aspect of the thecal sac at the L5/S1 level. Fixation of the sacral fracture, with the placement of an iliosacral screw, was performed shortly after initial imaging.Three days post-trauma, repeat CT of the head was performed because of a decreased level of consciousness.Small supernatant globules of fat (2124 Hounsfield units (HU)) were identified in the subarachnoid space in the prepontine cistern (Figure 1b), frontal horns of the lateral ventricles and foramen magnum. Intraventricular blood and subarachnoid haemorrhage in the interpeduncular fossa were also seen. A CT angiogram from the aortic arch to the vertex revealed no evidence of traumatic dissection, aneurysm or vascular malformation that would explain the presence of the new subarachnoid haemorrhage. MRI of the brain performed the same day confirmed the presence of subarachnoid and intraventricular fat and haemorrhage (Figure 2a,b). The MR study also showed several T 2 /FLAIR (fluid-attenuated inversion-recovery) hyperintensities in the cerebral white matter, as well as in the splenium of the corpus callosum, in keeping with diffuse axonal injury.MRI of the post-operative lumbosacral...

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

“…The first radiological description of intracranial fat dissemination was reported on a skull radiography in 1977, secondary to the spontaneous rupture of an intracranial dermoid cyst [ 7 ]. The spontaneous or iatrogenic rupture of lipid-containing masses (mostly dermoid or epidermoid cysts, and sometimes pineal teratomas) is an established cause of dissemination of fat droplets within the subarachnoid space [ 1 , 2 , 4 ]. It is rare that the rupture of an intracranial dermoid cyst is caused by trauma [ 8 ].…”

“…The observation of fat in the subarachnoid space after trauma in the absence of an intracranial or intraspinal tumor is exceptional and has been reported exclusively after sacral fractures [ 2 – 5 ]. The abundance of fatty yellow marrow in the sacral bone (especially in older patients) is a well-known phenomenon [ 18 ].…”

“…The presence of fat droplets in the cerebrospinal fluid (CSF) is an unusual imaging finding, which is almost always associated with spontaneous, postoperative, or post-traumatic rupture of fat-containing tumors (most frequently dermoid cysts) [ 1 , 2 ]. Although dermoid cysts are rare and represent only 0.5% of all primary intracranial tumors, the observation of fat in the subarachnoid space after trauma in the absence of intracranial or intraspinal tumors is exceptional and has been reported only after sacral fractures [ 1 – 6 ].…”

A Rare Case of Complex Pelvic Injury and Associated Intrathecal Fat Embolism due to Spinopelvic Dislocation with Sacral Burst Fracture

“…The observation of fat droplets in the ventricular system can rarely be found in the existing literature. It has been mostly described in cases of ruptures of intracranial or intraspinal dermoid or tarlov cysts [ 2 , 4 , 5 ], ruptures of teratomas [ 6 , 7 ], and rarely after removal of intracranial neoplasms such as meningioma [ 2 ]. There are also several reports that intracranial fat may occur after aortic valve surgeries [ 8 ].…”

Ventriculoperitoneal shunt malfunction caused by proximal catheter fat obstruction

“…The migration of fat droplets into the subarachnoid space after craniotomy [9][10][11], spinal trauma [12][13][14], baclofen pump insertion [15], and rupture of intracranial [16][17][18][19][20] or intraspinal canal dermoid cysts [21,22] has been previously described. Recently, two cases of obstructive hydrocephalus due to Sylvian aqueduct obstruction with fat droplets after craniotomy were reported [23,24].…”