[Radicular sciatica due to an intrarachidian mucoid cyst in a child].

In a 15 years old boy, a sciatica appears, at surgery, to be related with the compression of one SI root, and into the epidural space, by a pseudo-cyst, limited by a connective wall and containing a mucoid substance. Authors note the similarity of this lesion with the para-synovial cysts of extremities and with the colloid degeneration of the tunica adventitia of some vessels or of the connective sheath of the peripheric nerves. To their knowledge, such formations with mucoid content, at the spinal level, have only been reported on in the adult subject; they insist therefore on their patient's young age.