Based on the hypothesis that a constitutionally small posterior fossa represents a predisposition for the development of neurovascular conflict,the aim of this article is either to confirm or to reject this hypothesis.To this end,indices of the size of the posterior fossa were studied,in patients with neurovascular conflict and,parallelly in patients randomly selected from the standard population.The latter group was represented by patients having suffered brain concussion.The investigation of a sample of 100 patients (50 with neurovascular conflict and 50 after brain concussion)showed a significantly different size of the posterior fossa in the group of patients with neurovascular conflict.

        Key words: trigeminal neuralgia,hemifacial spasm,developmental anomalies,posterior fossa