- Department of Neurosurgery, College of Medicine, University of Florida, Gainesville, Florida, USA
- Department of Neurosurgery, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey
Department of Neurosurgery, College of Medicine, University of Florida, Gainesville, Florida, USA
DOI:10.4103/2152-7806.179383Copyright: © 2016 Surgical Neurology International This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.
How to cite this article: Baydin S, Gungor A, Baran O, Tanriover N, Rhoton AL. The double massa intermedia. Surg Neurol Int 29-Mar-2016;7:30
How to cite this URL: Baydin S, Gungor A, Baran O, Tanriover N, Rhoton AL. The double massa intermedia. Surg Neurol Int 29-Mar-2016;7:30. Available from: http://surgicalneurologyint.com/surgicalint_articles/the-double-massa-intermedia/
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.
Conclusion:The surgeon should be aware of the possibility of a double MI to avoid confusion during third ventricle surgery.
Keywords: Double massa intermedia, endoscopic surgery, neuroanatomy, third ventricle
The massa intermedia (MI), also called the adhesio interthalamica, links the paired thalami across the midline of the third ventricle.[
The third ventricles of ten formalin- and alcohol-fixed human brains and two whole cadaveric heads were examined from superior to inferior in a fiber dissection study. All specimen were refrigerated at −10–20°C for 2 weeks. After thawing the specimens under the water, the fiber dissection technique was performed under ×6 to ×40 magnifications provided by a Zeiss Surgical Microscope (Carl Zeiss AG, Oberkochen, Germany), and using the 0°, 18 cm Hopkins endoscopes (KARL STORZ GmbH and Co., Tuttlingen, Germany) connected to a xenon light source and a high-definition camera.[
Dissections proceeded from the superior surface of the cerebral cortex to the inferior. After opening the ventricle from superior, the paired fornices were retracted laterally to expose the third ventricle posterior to the foramen of Monro and AC, crossing the midline in the anterior wall of the third ventricle. The posterior commissure, also called the epithalamic commissure, was identified crossing the third ventricle just anterior to the pineal gland in the posterior part of the third ventricle above the cerebral aqueduct. In the center part of the third ventricle, a single MI was identified crossing the midline in all but one specimen, in which a second round, smooth connection between thalami was found posteroinferior to the most anterior MI [
Fiber dissection. Superior view. (a) The cortex, U fibers, cingulum, callosal fibers, and ependyma were removed to expose the lateral ventricle. After opening the ventricle from superior, the paired fornices were exposed. The fornices were separated in the midline to expose the third ventricle. In the center part of the third ventricle, posterior to the anterior commissure and foramen of Monro and anterior to the posterior commissure and pineal gland, a massa intermedia connected the medial surfaces of the thalami. A second smaller round, smooth massa intermedia crossed the midline posteroinferior to the large massa intermedia. (b) Enlarged view of 1a. Ant.: Anterior, Comm.: Commissure, Gl.: Gland, Int.: Intermedia, Plx.: Plexus, Sec.: Second, Vent.: Ventricle
Endoscopic view. (a) The endoscope has been advanced from posterosuperiorly to expose the anterior part of the third ventricle. A large massa intermedia is seen posterior to the anterior commissure, and a second smaller massa intermedia is located posteroinferior to the larger massa intermedia. (b) Enlarged view of 2a. Both massa intermedias have been retracted superiorly with a nerve hook. (c) The endoscope has been advanced from anterosuperiorly above the anterior commissure to see the posterior part of the third ventricle. (d) Enlarged view of 2c. The second massa intermedia is retracted superiorly by a nerve hook. Ant.: Anterior, Comm.: Commissure, Gl.: Gland, Int.: Intermedia, Mam.: Mammillary, Plx.: Plexus, Post.: Posterior, Sec.: Second, Vent.: Ventricle
Although morphology, relations, location, and size of MI are well-defined, its role in the central nervous system is not clear. The MI can be defined in approximately 75% of individuals during imaging procedures.[
In this case, the second structure in the middle of the third ventricle, it was defined that the structure reported here was a second massa intermedia based on its location and connecting structures. There are some other commissural fibers that must be differentiated from secondary MI. These include the habenular, anterior, and posterior commissures.[
The morphology, size, and position of MI are important in neurosurgery as well as in neuroanatomy and neuroradiology. It is especially important in endoscopic third ventricular interventions. There are also some classifications of third ventricle tumors that use the MI as a landmark.[
Awareness of duplicate MI may prove helpful in surgical planning for third ventricle or pineal region approaches.
Financial support and sponsorship
Funding was from the University of Florida Foundation.
Conflicts of interest
There are no conflicts of interest.
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