Pathogenesis of arachnoid cyst: Congenital or traumatic?

For clarifying the pathophysiology of arachnoid cysts and restablishing the rapeutic criteria for such cases, we reviewed a series of 90 cases with ara chnoid cysts focusing on the traumatic origin. Arachnoid cysts of congenita l origin have been well known. But we suspected that 14 out of 90 patients (15.6%) with arachnoid cyst were closely related to head trauma. Seven of t hem suffered from head traumas in infancy. The episodes of head trauma incl uded falling down in 4 patients, slipping down in 2 patients, and a motor v ehicle accident in 1 patient. Traumatic arachnoid cysts had a latent period from head trauma to initial clinical manifestation. The mean latent period was 2.2 years, ranging from 10 months to 6.2 years. Six of 7 arachnoid cys ts were located in the suprasellar area and 1 at the posterior fossa. An ot her 7 patients had a history of perinatal trauma. We postulate that head tr auma in infancy may contribute to the pathogenesis of arachnoid cyst in som e cases.