Ossified pseudomeningocoele following laminectomy: case reports and review of the literature.

To date, four cases of ossified extradural pseudocyst have been described, the first being in 1951 by Verbiest who described unusual forms of compression of the cauda equina including a case of a lumbo-sacral extradural cyst and a case of 'knotting' of a caudal nerve root. We present an additional two cases.