The thalamus is a paired, egg-shaped mass of grey matter on either side of the third ventricle, often described as the gateway to the cerebral cortex. Nearly all sensory pathways (except smell) synapse here before reaching the cortex, and it also relays motor loops from the cerebellum and basal ganglia. Its many nuclei are divided by a thin Y-shaped sheet of white matter called the internal medullary lamina.
| Location | Deep in each cerebral hemisphere, forming the upper lateral walls of the third ventricle, medial to the posterior limb of the internal capsule |
|---|---|
| Parts |
|
| Connections |
|
| Blood Supply | Thalamoperforating arteries (posterior cerebral artery); Thalamogeniculate arteries; Polar (tuberothalamic) artery from the posterior communicating artery; Posterior choroidal arteries |
Relays and modulates sensory, motor and limbic information to the cortex, helps control alertness and sleep-wake states, and contributes to attention, memory and emotion.
Thalamic lesions classically cause contralateral loss of all sensory modalities. Weeks later some patients develop Dejerine-Roussy (thalamic pain) syndrome, a severe burning pain on the numb side. Occlusion of the artery of Percheron, a single vessel supplying both medial thalami, causes sudden coma or hypersomnolence with eye movement problems. Deep brain stimulation of thalamic targets (ventral intermediate nucleus) is used to treat essential tremor.
Also called Dejerine-Roussy syndrome, a chronic central pain that develops after a thalamic stroke, felt as burning or aching pain on the side of the body opposite the lesion.
Blockage of a single artery supplying both paramedian thalami, producing sudden reduced consciousness, vertical gaze palsy and memory loss.
Hypertensive bleeding into the thalamus that can cause hemisensory loss, hemiparesis if it extends into the internal capsule, and hydrocephalus if it ruptures into the ventricles.
