The theory of a transaxonal short circuit between sensory fibers and pain fibers of the trigeminal root as an explanation of essential facial neuralgia is satisfactory in that it elucidates the character of the crises and clarifies their pathogenesis. The etiology of these crises is often obscure and one should look for possible sources of irritation at the root of the nerve: osseous causes, super-elevation of the petrous apex, meningeal causes, and contact with a sclerotic or tortuous artery of the posterior fossa. This concept permits us to look at the pathogenesis and etiology of idiopathic facial neuralgia in a new light and to modify the technique of retrogasserian neurotomy which it suggests.