The encephalon (from the ancient Greek ???? fa ???, or egkephalos, meaning “which is in the head”) corresponds to the structures located within the cranial box which constitute the central nervous system with the spinal cord.

Position. The brain is located within the cranial box, a bony structure that protects it.

Structure. The brain is the intracranial part of the central nervous system and is made up of several distinct parts (1).

• The telencephalon occupies most of the brain and corresponds to the brain. It consists in particular of the two hemispheres, left and right, as well as associated structures such as the corpus callosum, connecting the two hemispheres.
• The diencephalon is centrally located under the corpus callosum and is extended by the brainstem. It is made up of the thalamus, the hypothalamus and the epithalamus.
• The cerebellum is located behind the brain and below the hemispheres.
• The brainstem is the lower part of the brain located between the diencephalon and the spinal cord. It is made up of 3 parts: the midbrain, the bridge and the medulla oblongata.

Protection of the brain. The brain is protected by different structures:

• The bones of the skull surround and protect the brain.
• The meninges are located under the skull and envelop the brain. They are made up of three layers: the dura mater, the arachnoid and the pia mater.
• Cerebrospinal fluid circulates in the subarachnoid space, between the pia mater and the arachnoid, as well as in the 4 ventricles, cavities of the brain.
• The blood-brain barrier separates the bloodstream from the brain and allows greater selectivity of molecules crossing the nervous tissue.

Role within the central nervous system. The brain and its structures play a vital role. They control in particular consciousness, cognition, interpretation, assimilation of perceptions, as well as voluntary movements (2).

Different pathologies can affect the brain and its structures.

Head trauma. It corresponds to a shock to the skull that can cause brain damage.3 These lesions can be concussions, that is to say reversible lesions, or bruises, irreversible lesions (2).

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. (4) This pathology can impact on the functions of the brain.

Degenerative cerebral pathologies. Certain pathologies can lead to changes in nervous tissue in the brain.

• Alzheimer’s disease. It results in a modification of cognitive faculties with in particular a loss of memory or reasoning. (5)
• Parkinson disease. It is manifested in particular by a tremor at rest, a slowing down and a reduction in the range of motion. (6)

Brain tumors. The brain can be the site of the development of benign or malignant tumors. (7)

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

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

Surgical treatment. Depending on the type of pathology diagnosed and the course, surgery may be carried out.

Chemotherapy, radiotherapy. Depending on the stage of the tumor, these treatments can be implemented.

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

Medical imaging examination. 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.