Lumbar epidural lipomatosis: the "Y" sign of thecal sac compression.
OBJECTIVE
We have identified a specific sign of lumbar thecal sac compression seen in patients with symptomatic lumbar epidural lipomatosis. Recognition of this sign will aid with proper diagnosis of this unusual disorder.


METHODS
Computerized Tomography (CT) and Magnetic Resonance Imaging (MRI) examinations of the lumbar spine performed in the evaluation of low back pain over a 24 mo period demonstrated nine patients with excessive fat in the epidural space. Myelography was performed on five of these patients. Detailed analysis of the shape and degree of thecal sac compression was made.


RESULTS
Eight of the nine patients with epidural lipomatosis demonstrated a characteristic type of thecal sac compression not seen with other spinal disorders. On cross sectional imaging, the thecal sac has a striking stellate appearance with three rays emanating from a central core. This produces a trifid shape resembling the letter "Y". In two patients scanned following subsequent surgical removal of the epidural fat, the thecal sac had resumed its normal configuration.


CONCLUSIONS
A seemingly specific and easily recognized type of compression of the thecal sac may occur with lumbar epidural lipomatosis. This creates a trifid appearance of the thecal sac; we have termed this the "Y" sign.
Division of Neuroradiology, Southern Illinois University School of Medicine, Springfield 62769.
M J
MJ
Kuhn
H T
HT
Youssef
T L
TL
Swan
L C
LC
Swenson
D000328:Adult; D000368:Aged; D003287:Contrast Media; D004388:Dura Mater / Q000000981:diagnostic imaging / Q000473:pathology; D004824:Epidural Space; D005260:Female; D006801:Humans; D008068:Lipomatosis / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D017116:Low Back Pain / Q000175:diagnosis / Q000000981:diagnostic imaging; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009192:Myelography; D013117:Spinal Cord Compression / Q000175:diagnosis / Q000000981:diagnostic imaging; D013122:Spinal Diseases / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed
D003287:Contrast Media