| Interthalamic adhesion | |
|---|---|
 Dissection showing the ventricles of the brain. (Interthalamic adhesion labeled as Massa Intermedia at center right.) | |
 Coronal section of brain through intermediate mass ofthird ventricle. | |
| Details | |
| Part of | Thalamus |
| Identifiers | |
| Latin | adhaesio interthalamica |
| NeuroNames | 301 |
| NeuroLex ID | nlx_144100 |
| TA98 | A14.1.08.103 |
| TA2 | 5778 |
| FMA | 74869 |
| Anatomical terms of neuroanatomy | |
Theinterthalamic adhesion (also known as themassa intermedia,intermediate mass ormiddle commissure) is a flattened band of tissue that connects both parts of thethalamus at their medial surfaces. The medial surfaces form the upper part of the lateral wall to thethird ventricle.
In humans, it is only about one centimeter long – though in females, it is about 50% larger on average.[1] Sometimes, it is in two parts – and 20% of the time, it is absent.[2] In other mammals, it is larger.
In 1889, a Portuguese anatomist by the name of Macedo examined 215 brains, showing that male humans are approximately twice as likely to lack an interthalamic adhesion as are female humans. He also reported its absence, still reported today in about 20% of humans. Its absence is seen to be of no consequence.[2]
The interthalamic adhesion containsnerve cells andnerve fibers; a few of the latter may cross the middle line, but most of them pass toward the middle line and then curve laterally on the same side. It is still uncertain whether the interthalamic adhesion contains fibers that cross the midline – and for this reason, it is inappropriate to call it acommissure.
The interthalamic adhesion is notably enlarged in patients with the type IIArnold–Chiari malformation.[3]
This article incorporates text in thepublic domain from the 20th edition ofGray's Anatomy(1918)
