- Internal capsule
Name = PAGENAME
Latin = capsula interna
GraySubject = 189
GrayPage = 836
Caption = Horizontal section of right cerebral hemisphere. (Capsula interna labeled at upper left.)
Caption2 = The motor tract.
BrainInfoType = hier
BrainInfoNumber = 180
DorlandsPre = c_07
DorlandsSuf = 12211417
The internal capsule is an area of
white matterin the brainthat separates the caudate nucleusand the thalamusfrom the lenticular nucleus. The internal capsule contains both ascending and descending axons.
It consists of
axonal fibres that run between the cerebral cortexand the pyramids of the medulla.
The internal capsule is V-shaped when cut both "coronally" (on the same plane as the face) and "horizontally"/"transversely" (the same plane as the brim of a
When cut horizontally:
* the bend in the V is called the "genu".
* the part in front of the genu is the "
anterior limb". or "crus anterius".
* the part behind the genu is called the "
posterior limb" or "crus posterius".
There is also a "retrolenticular" and a "sublenticular" part to the internal capsule.
* The posterior limb of the internal capsule contains
corticospinal fibers and sensory fibers from the body.
* The genu contains
corticobulbar fibers, which run between the cortex and the brainstem.
* The anterior limb of the internal capsule contains:
frontopontine(corticofugal) fibers project from frontal cortexto pons;
thalamocortico fibersconnect the medial and anterior nuclei of the thalamus to the frontal lobes (these are severed during a prefrontal lobotomy).
* The retrolenticular part contains fibers from the optic system, coming from the
lateral geniculate nucleusof the thalamus. More posteriorly, this becomes the optic radiation. Some fibers from the medial geniculate nucleus(which carry auditory information) also pass in the retrolenticular internal capsule, but most are in the sublenticular part.
The anterior limb of the internal capsule is supplied by lenticulostriate arteries coming off the
middle cerebral arteryand by Heubner's artery, which comes from the anterior cerebral artery.
The posterior limb of the internal capsule is supplied by the
thalamogeniculate artery, which is a branch of the posterior cerebral artery.
Infarctions to the internal capsule tend to be small, punctate lesions.
They can affect sensory and motor systems on the opposite side of the body, and possibly
eyesight(to the contralateral visual field).
Hearing should not be affected in a single capsule lesion, as this information crosses over to both sides of the brain while in the brainstem.
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