The fornix (from the Latin fornix, meaning ark) is a structure of the brain, belonging to the limbic system and making it possible to connect the two cerebral hemispheres.

Position. The fornix belongs to the central nervous system. It constitutes an intra and inter-hemispherical commissure, that is to say a structure making it possible to connect the two cerebral hemispheres, left and right. The fornix is ​​located in the center of the brain, under the corpus callosum (1), and extends from the hippocampus to the mammillary body of each hemisphere.

Structure. The fornix is ​​made up of nerve fibers, particularly from the hippocampus, the structure of the brain contained in each hemisphere (2). The fornix can be divided into several parts (1):

• The body of the fornix, positioned horizontally and glued to the underside of the corpus callosum, constitutes the central part.
• The columns of the fornix, two in number, arise from the body and move towards the front of the brain. These columns then curve downward and backward to reach and terminate at the mammillary bodies, structures of the hypothalamus.
• The pillars of the fornix, two in number, arise from the body and go towards the back of the brain. A beam comes from each pillar and is inserted within each temporal lobe to reach the hippocampus.

Actor of the limbic system. The fornix belongs to the limbic system. This system links the structures of the brain and allows the processing of emotional, motor and vegetative information. It has an impact on behavior and is also involved in the memorization process (2) (3).

Of degenerative, vascular or tumor origin, certain pathologies can develop and affect the central nervous system and in particular the fornix.

Head trauma. It corresponds to a shock to the skull which can cause brain damage. (4)

Stroke. Cerebrovascular accident, or stroke, is manifested by the blockage of a cerebral blood vessel, including the formation of blood clots or the rupture of a vessel.5 This condition can affect the functions of the fornix.

Alzheimer’s disease. This pathology is manifested by a modification of cognitive faculties with in particular a loss of memory or a decrease in the faculty of reasoning. (6)

Parkinson disease. It corresponds to a neurodegenerative disease, the symptoms of which are in particular a tremor at rest, or a slowing down and reduction in the range of motion. (7)

Multiple sclerosis. This pathology is an autoimmune disease of the central nervous system. The immune system attacks the myelin, the sheath surrounding nerve fibers, causing inflammatory reactions. (8)

Brain tumors. Benign or malignant tumors can develop in the brain and affect the functioning of the fornix. (9)

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

Thrombolyse. Used during strokes, this treatment consists of breaking up the thrombi, or blood clots, with the help of drugs. (5)

Surgical treatment. Depending on the type of pathology diagnosed, surgery may be performed.

Chemotherapy, radiotherapy, targeted therapy. Depending on the type and stage of the tumor, these treatments may be implemented.

Physical examination. 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 fornix damage, a brain scan or a brain MRI can in particular be performed.

biopsy. This examination consists of a sample of cells, in particular to analyze tumor cells.

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

Papez’s circuit, described by the American neuroanatomist James Papez in 1937, groups together all the structures of the brain involved in the process of emotions, including the fornix. (10).