[Suprasellar arachnoid cyst associated with syringomyelia. Case report].

We present a case of suprasellar arachnoid cyst which was revealed by visual impairement and hypopituitarism. Neuroradiological imaging showed the peculiar association of the suprasellar cyst with cerebellar tonsillar herniation and a large asymptomatic cervical syringomyelic cavity. Surgical treatment of the suprasellar cyst allowed the reduction of both the cyst and the syrinx. A common pathophysiological mechanism of these lesions is discussed. We suggest the possibility that an initial obstruction of the basal cisterns caused the suprasellar cyst formation which led to medullar cavity formation.