Anorectal malformation and spinal dysraphism: the value of diffusion-weighted imaging in detecting associated intradural (epi)dermoid cyst

Anorectal malformations (ARMs) are associated with a variety of spinal dysraphisms, of which clinical impact is often underestimated. A 6-year-old girl, with a history of rectovaginal fistula, presented with gait disturbance, asthenia, and worsening of fecal incontinence. The spinal magnetic resonance imaging (MRI) at 12 months of age had revealed a tethered cord and a little intradural lipoma. Within the lipoma, a small cystic lesion, interpreted as a cerebrospinal fluid (CSF)-filled loculation, was also described. A consecutive MRI showed a marked increase in size of the CSF-like cyst that was clearly hyperintense on diffusion-weighted imaging (DWI) and presented reduced apparent diffusion coefficient values (855 ± 109 s/mm²), not compatible with CSF values. This lesion, interpreted as an (epi)dermoid cyst, was removed and histologically confirmed; the spinal cord was untethered. The child's lower limb motor deficit resolved rapidly after surgery, and the fecal incontinence slowly returned to the previous bowel habit. There is a growing interest in recognizing and defining spinal dysraphism in ARM patients because some abnormalities may carry severe clinical consequences. For this purpose, a standardized MR protocol is required, in which DWI plays a pivotal role to disclose associated dysembriogenetic lesions, in particular when a CSF loculation is detected.