Objective: To describe the morphological and topographic features of the triangular recess (TR) in the anterior wall of the third ventricle and the pathological conditions that allow its observation during ventricular endoscopic neuronavigation.
Methods: A systematic review of records and operative videotapes for 145 patients who underwent endoscopic third ventriculostomy was performed.
Results: The TR could be recognized in five cases of hydrocephalus, each caused by a different underlying pathological condition. The approach was precoronal in four cases and suboccipital in one. The morphological and topographic features of the TR and adjacent structures varied among the different cases.
Conclusion: Although it is seldom reported in neuroanatomy handbooks and is not readily accessible under normal conditions, the TR is a characteristic structure of the third ventricle, which might become apparent in several conditions that produce hydrocephalus. Neurosurgeons who perform neuroendoscopy should be aware of this structure and of the situations that cause its deformation and allow its observation during endoscopic neuronavigation.