SONOGRAPHIC FEATURES OF ASCENDING TRANSTENTORIAL HERNIATION OF POSTERIOR FOSSA CYSTIC MASSES.

Ascending transtentorial herniation of a posterior fossa cystic mass is an unusual condition. The sonographic anatomy of the tentorium cerebelli and the tentorial notch is presented and the anatomical basis and the sonographic criteria for the diagnosis of transtentorial herniation are discussed. In neurosonography, the identification of the tentorium helps in separating lesions of the posterior fossa from the lesions in the occipital lobes of the cerebrum. Two patients with transtentorial herniation were diagnosed by real-time neurosonography performed through the anterior fontanelle. The ascending transtentorial herniation of such masses can lead to compression of the mid brain and the posterior cerebral arteries in addition to producing pressure on the vital contents of the posterior fossa.