title: The double massa intermedia.
abstract: BACKGROUND
  To describe the rare finding of a double massa intermedia (MI). Typically, the MI (interthalamic adhesion) is a single bridge of gray matter connecting the medial surfaces of the thalami.
  
  
  METHODS
  Twelve formalin- and alcohol-fixed human third ventricles were examined from superior to inferior by fiber dissection technique under ×6 to ×40 magnifications and with the endoscope.
  
  
  RESULTS
  In all hemispheres, the anterior and posterior commissure were defined. The MI, which bridges the medial surfaces of the thalami, was defined in all hemispheres. In one hemisphere, there was a second bridge between the thalami, located posteroinferior to the common MI. Endoscopic view confirmed that there was a second MI in this specimen. The MI usually traverses the third ventricle posterior to the foramen of Monro and connects the paired thalami. The MI is an important landmark during endoscopic and microscopic surgeries of the third ventricle. Although a double MI is very rare, surgeons should be aware of the possibility in their surgical planning.
  
  
  CONCLUSIONS
  The surgeon should be aware of the possibility of a double MI to avoid confusion during third ventricle surgery.
authors.affiliation: Department of Neurosurgery, College of Medicine, University of Florida, Gainesville, Florida, USA.
authors.forename: Serhat
authors.initials: S
authors.lastname: Baydin
authors.affiliation: Department of Neurosurgery, College of Medicine, University of Florida, Gainesville, Florida, USA.
authors.forename: Abuzer
authors.initials: A
authors.lastname: Gungor
authors.affiliation: Department of Neurosurgery, College of Medicine, University of Florida, Gainesville, Florida, USA.
authors.forename: Oguz
authors.initials: O
authors.lastname: Baran
authors.affiliation: Department of Neurosurgery, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey.
authors.forename: Necmettin
authors.initials: N
authors.lastname: Tanriover
authors.affiliation: Department of Neurosurgery, College of Medicine, University of Florida, Gainesville, Florida, USA.
authors.forename: Albert L
authors.initials: AL
authors.lastname: Rhoton
keywords: Double massa intermedia; endoscopic surgery; neuroanatomy; third ventricle