Case of the Month
Section Editor: Nicholas Stence, MD
Children's Hospital Colorado, Aurora, CO
November 2019
Next Case of the Month Coming December 10...
Subarachnoid Fat Droplets from Sacral Fracture
- Background:
- Cerebral subarachnoid fat syndrome may occur in the setting of a rupture of CNS fat-containing lesions, as well as posttraumatic and/or postoperative transthecal contamination.
- Fat-attenuating droplets occupy the subarachnoid space with or without fat-fluid levels observed on the nondependent portions of the ventricular system.
- Discovery of subarachnoid fat in a trauma patient warrants the entire neural axis to be scrutinized for fat-containing lesions, postsurgical fat grafts, traumatic injury, or possible postoperative/postprocedural breach of the dural integrity.
- Clinical Presentation:
- Headache is the most common symptom.
- Signs and symptoms of chemical meningitis related to irritation caused by the fat
- Key Diagnostic Features:
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Fat-attenuating droplets are observed in the subarachnoid compartment on NECT head. A soft-tissue window provides the best contrast for this depiction.
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Precontrast T1-hyperintense fat droplets are seen in the subarachnoid space. They may demonstrate chemical shift artifact. These droplets are not identified on fat-suppressed images.
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- Differential Diagnoses:
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Ruptured (usually spontaneously ruptured) dermoid or other fat-containing tumors
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Fat released from postoperative fat grafts and serial lumbar puncture/baclofen pump placement has also been described in the literature as a possible source of subarachnoid fat.
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Residual subarachnoid iophendylate (Pantopaque) from remote intrathecal contrasted procedures is a historical yet possible differential diagnosis.
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In this case, a posttraumatic source (including possible postoperative dural breach in repair of the acute sacral fractures) was considered the putative source of cerebral subarachnoid fat emboli. A follow-up CT myelogram 3 weeks after the trauma failed to demonstrate an active dural tear, which likely spontaneously resolved in the interim or was too small to be demonstrated.
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- Treatment:
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Consider treatment or supportive care of aseptic meningitis or other complications.
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Our patient was placed on steroids for the orbital traumatic injury and possible chemical meningitis.
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May require shunt placement if rare complication of hydrocephalus occurs
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Identification of possible dural tear for consideration of treatment of CSF leak
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