Genu of the Internal Capsule

genu capsulae internae

The genu is the bend of the internal capsule where the anterior and posterior limbs meet, pointing towards the midline at the level of the interventricular foramen. It carries corticobulbar fibres from the motor cortex to the cranial nerve motor nuclei that control the face, jaw, tongue and throat.

Anatomical Data

Structure & Connections

Location	Bend of the internal capsule between the anterior and posterior limbs, at the level of the interventricular foramen
Connections	Corticobulbar tract Primary motor cortex (face area) Cranial nerve motor nuclei
Blood Supply	Direct branches of the internal carotid artery; Lenticulostriate arteries; Anterior choroidal artery

Biomechanics

Function & Actions

Carries motor commands from the cortex to the brainstem nuclei that move the face, jaw, tongue, palate and throat.

Clinical Relevance

Clinical Notes

A small lesion here can cause weakness of the lower opposite face and tongue with difficulty speaking and swallowing (dysarthria), sometimes with mild arm weakness. Because the upper face receives input from both hemispheres, the forehead is usually spared, a key sign of an upper motor neuron facial weakness.

Pathology

Common Injuries & Conditions

Genu Lacunar Infarct

Small stroke causing weakness of the opposite lower face and tongue with dysarthria.

Dysarthria Clumsy Hand Syndrome

A lacunar syndrome with slurred speech and a clumsy hand, sometimes from a lesion near the genu.

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