Chronic cystic lesion of the sacrum: characterisation with diffusion-weighted MR imaging.
OBJECTIVE
Sacral bone remodelling with abnormal dilatation of intervertebral foramina is usually associated with Tarlov cysts but can be caused by slow-growth lesions, which also may present cerebrospinal-fluid (CSF)-like signal or density. We describe three patients with a similar history of lower back pain presenting CSF-like density/signal lesions with extensive sacral bone remodelling who were affected by a Tarlov cyst, an epidermoid cyst and a giant neurofibroma, respectively.


METHODS
Magnetic resonance imaging (MRI) studies were performed with 1.0-T magnet; axial and sagittal pre- and postcontrast T1-and T2-weighted images were obtained. Moreover, axial and sagittal diffusion-weighted (DWI) echoplanar images were produced, and corresponding apparent diffusion coefficient (ADC) values were calculated. ADC values were measured within the lesions on axial images.


RESULTS
All lesions presented a CSF-like signal on conventional MRI. The Tarlov cyst was hypointense on DWI with high ADC values (2,793 s/mm(2)+/-137). The epidermoid cyst proved to be markedly hyperintense on DWI, with reduced ADC values (855 s/mm(2)+/-109). The neurofibroma was isointense on DWI, with ADC values not compatible with CSF (1,467 s/mm(2)+/-130).


CONCLUSIONS
DWI and ADC values seem to be able to clearly differentiate Tarlov cysts from slow-growth lesions, allowing for adequate treatment.
Neuroradiologic Unit, University of Padua, Via Giustiniani 2, 35128 Padova, Italy. renzo.manara@sanita.padova.it
R
R
Manara
M
M
Severino
R
R
Mandari
G
G
Mattisi
S
S
Dal Pozzo
C
C
Carollo
D000328:Adult; D038524:Diffusion Magnetic Resonance Imaging; D004814:Epidermal Cyst / Q000175:diagnosis* / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008875:Middle Aged; D009455:Neurofibroma / Q000175:diagnosis* / Q000000981:diagnostic imaging; D012447:Sacrum / Q000000981:diagnostic imaging / Q000473:pathology*; D013125:Spinal Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging; D052958:Tarlov Cysts / Q000175:diagnosis* / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed