The internal capsule is a mass of white fibers which lie between the basal ganglia and thalamus. The posterior limb is commonly injures due to hemorrhage or thrombosis in the lenticulo striate artery. The lesion results in the following:
1- Hemi-plegia i.e. paralysis of the muscles present in the opposite side of the body due to damage of pyramidal and extra- pyramidal tracts fibers.
2- Hemi-anesthesia i.e. loss of all sensations from the opposite side of the body due to damage of sensory radiation.
3- Hemi-anopia i.e. loss of vision in the opposite halves of visual fields of both eyes. So, lesion in the right internal capsule leads to loss of vision in the left halves of visual fields of both eyes. It is due to damage of optic radiation.
4- Decrease hearing;it is due to damage of auditory radiation. No deafness because each ear is bilaterally represented in the cerebral cortex.