Orbital porencephalic cyst following penetrating orbitocranial trauma.

In a 10-year-old boy an orbitocranial penetrating wound produced by an umbrella tip caused an orbital roof bone fragment to penetrate up to the anterior part of the third ventricle behind the left foramen of Monro. Hemorrhages and encephalomalacia developed along the trajectory of the fragment and subsequently a porencephalic cyst was formed at this site. Six months after the trauma, increased pressure developed in the left ventricular system due to obstructive hydrocephalus and consequently the porencephalic cyst herniated into the orbit through the orbital roof fracture, producing intermittent diplopia, left exophthalmos, and palpebral swelling. A ventriculo-peritoneal shunt led to shrinkage of the orbital cyst content and resolution of the symptoms.