The thalamus is an even nucleus of gray matter located within the brain.

Position. The thalamus is a structure of the central nervous system, and more specifically of the diencephalon. Each nucleus is located in one of the two hemispheres of the brain, and more particularly at the front of the epithalamus, above the hypothalamus (1) and below the caudate nucleus. Between the two thalami forms the 3rd ventricle, a cavity in which cerebrospinal fluid circulates (2). The side walls of the thalami are separated from the lenticular nuclei by the internal capsule, which consists of bundles of white matter.

Structure. A large nucleus with an ovoid shape and gray matter, the thalamus is actually made up of several substructures or nuclei. These nuclei can be categorized into two parts (2):

• the specific nuclei of the thalamus in relation to the cerebral cortex;
• the specific nuclei of the thalamus in relation to the other structures of the diencephalon as well as the brainstem.

Vascularization. Three arteries supply the thalamus: the posterior communicating artery, the posterior cerebral artery and the anterior choroidal artery (3).

The thalamus plays an essential role in the relay (1):

• sensory and sensory impulses going up to the corresponding regions;
• motor impulses from the cortical motor nuclei and cerebellum to reach the motor regions
• as well as other nerve impulses

Many pathologies can affect the thalamus and in particular lead to thalamic syndrome. The latter corresponds to disorders associated with lesions of the thalamus such as motor disorders, sensory disorders or memory disorders (4). The causes of these lesions are varied and may in particular be of vascular, degenerative, traumatic or even tumor origin.

Head trauma. It corresponds to a shock to the skull which can cause brain damage. (5) These lesions can be concussions, that is to say reversible lesions or contusions, irreversible lesions (1).

Stroke. Cerebrovascular accident, or stroke, is manifested by obstruction, such as the formation of blood clots or the rupture of a blood vessel in the brain. (6) This pathology can impact on the functions of the thalamus.

Parkinson disease. It is one of the main neurodegenerative diseases. Symptoms include a tremor at rest, or a slowing and reduced range of motion. (7)

Brain tumors. Benign or malignant tumors can develop in the thalamus. (8)

Thrombolyse. Used during strokes, this treatment consists of breaking up the thrombi, or blood clots, with the help of drugs. (3)

Drug treatments. Depending on the pathology diagnosed, different treatments may be prescribed such as anti-inflammatory drugs.

Surgical treatment. Depending on the type of pathology diagnosed, surgical intervention may be carried out.

Chemotherapy, radiotherapy. Depending on the stage of the tumor, these treatments may be prescribed.

Clinical examue. First, a clinical examination is performed in order to observe and assess the symptoms perceived by the patient.

Medical imaging exam. In order to assess brainstem damage, a cerebral and spinal CT scan or a cerebral MRI can in particular be performed.

biopsy. This examination consists of a sample of cells.

Lumbar puncture. This exam allows the cerebrospinal fluid to be analyzed.

Galen, an ancient Greek physician, was the first to introduce the term thalamus (9).