White Matter and Internal Capsule

Vocabulary practice flashcards covering cerebral white matter classifications, commissures, subdivisions of the corpus callosum and internal capsule, their blood supply, and relevant clinical syndromes.

Association Fibers

Nerve fibers that connect two cortical areas within the same cerebral hemisphere, subdivided into short and long fibers.

Short Association Fibers

Association fibers that connect adjacent gyri to one another within the same hemisphere.

Long Association Fibers

Association fibers that connect gyri located farther away from one another within the same hemisphere.

Commissural Fibers

Fibers that connect corresponding areas between different cerebral hemispheres, allowing the two hemispheres to communicate and orchestrate into a single personality.

Anterior Commissure

A commissural fiber tract that connects olfactory structures of both cerebral hemispheres, specifically the olfactory bulb and the anterior perforated substance.

Posterior Commissure

A commissural tract located just above the upper end of the cerebral aqueduct that connects visual structures between both hemispheres.

Hippocampal Commissure

Also known as the commissure of the fornix; fibers that connect the hippocampus of one side with its fellow on the opposite side.

Corpus Callosum

The largest commissure in the brain, divided into four anatomical parts: the rostrum, genu, body, and splenium.

Rostrum of Corpus Callosum

The thin part forming the anterior end of the corpus callosum; connects the orbital surfaces of the frontal lobes of both hemispheres.

Genu of Corpus Callosum

The curved anterior bend of the corpus callosum; connects the anterior parts of the frontal lobes on both sides.

Forceps Minor

The fiber bundle formed by the radiation of genu fibers running forwards toward the frontal poles.

Body of Corpus Callosum

The segment of the corpus callosum that arches posteriorly and ends as the splenium; connects the posterior part of the frontal lobe and anterior part of the parietal lobe on both sides.

Splenium of Corpus Callosum

The thick posterior end of the corpus callosum; connects the posterior parietal, temporal, and occipital lobes between both hemispheres.

Tapetum

Fibers of the splenium that pass lateral to the posterior horn of the lateral ventricle.

Forceps Major

Fibers radiating from the splenium that pass medial to the posterior horn of the lateral ventricle into the occipital lobes.

Split-Brain Syndrome

A condition resulting from surgical sectioning of the corpus callosum (used to treat intractable epilepsy), causing hemisphere disconnection where patients cannot verbally identify items or words presented exclusively to the left visual field or left hand.

Projection Fibers

White matter fibers passing to or from the cerebral cortex, subdivided into ascending and descending pathways.

Internal Capsule

A compact projection fiber band composed of all afferent and efferent fibers passing to or from the cerebral cortex; anatomically divided into an anterior limb, genu, and posterior limb.

Anterior Limb of Internal Capsule

The portion of the internal capsule located between the head of the caudate nucleus and lentiform nucleus; carries frontopontine fibers and anterior thalamic radiation.

Genu of Internal Capsule

The bend between the anterior and posterior limbs of the internal capsule; contains corticobulbar (corticonuclear) fibers.

Thalamolentiform Part of Posterior Limb

The region of the posterior limb lying between the lentiform nucleus and the thalamus; transmits parietopontine fibers, superior thalamic radiation, corticospinal tract, corticorubral tract, and corticostriate tract.

Retrolentiform Part of Posterior Limb

The region extending caudally behind the lentiform nucleus; transmits occipitopontine fibers and posterior thalamic radiation including optic radiation.

Sublentiform Part of Posterior Limb

The region passing beneath the lentiform nucleus; transmits temporopontine fibers and inferior thalamic radiation including auditory radiation.

Arterial Supply of Internal Capsule Limbs

Both anterior and posterior limbs receive primary arterial supply via branches of the middle cerebral artery.

Anterior Cerebral Artery (Internal Capsule Territory)

The artery supplying the anteromedial parts of the anterior limb of the internal capsule.

Internal Carotid Artery (Internal Capsule Territory)

The artery that gives off direct branches supplying the genu of the internal capsule.

Anterior Choroidal Artery (Internal Capsule Territory)

The artery supplying the ventral portion of the posterior limb and the entire retrolenticular (retrolentiform) part of the internal capsule.

Infarction of the Internal Capsule

Clinical condition most frequently caused by occlusion of the lenticulostriate branches of the middle cerebral artery, presenting with contralateral anesthesia, contralateral hemiparesis (with the Babinski sign), and contralateral lower facial weakness.