An interpeduncular fossa is a slightly bowl-shaped area on the lower inside surface of the midbrain, located between two stalks of the cerebral peduncles. Several anatomical structures are contained within the interpeduncular fossa, including the posterior perforated substance, two mammillary bodies, the tuber cinereum, and the pituitary stalk and gland.
The surface of the floor of the interpeduncular fossa is called the posterior perforated substance. This layer of gray brain matter has many small holes across its surface that allows blood vessels to pass through to the brain. Traveling through the structure are the thalamoperforating arteries which enter the brain from the holes in the posterior perforated substance.
Above the posterior perforated substance of the interpeduncular fossa are the pituitary stalk and the pituitary gland. The pea-sized pituitary gland secretes nine different hormones that control many bodily functions. The pituitary stalk connects the gland to the hypothalamus. Anterior to the pituitary gland are two mammillary bodies, or corpora mamillaria, which are part of the limbic system. Between the mammillary bodies is part of the hypothalamus called the tuber cinereum.
Malformed interpeduncular fossa may indicate an underlying neurological condition which may be diagnosed with a magnetic resonance imaging (MRI) scan, used to visualize the internal structures of the brain. The congenital condition Joubert Syndrome is characterized by a brain malformation that looks like an adult molar tooth; the white tooth-shaped space visible on the brain scan is caused by an unusually deep fossa, surrounded by abnormally straight and wide peduncle stalks. A third defining characteristic is a hypoplastic, or not completely developed, cerebellar vermis, which is a narrow segment of brain tissue that is located in between the two halves of the cerebellum.
Most people born with Joubert’s have many developmental delays. Basic growth milestones, such as sitting and walking do not occur on average until the child has reached at least 18 months old. As many as half of the children diagnosed with it are not able to walk without assistance due to the poor muscle tone, or hypotonia, that is common when a malformed interpeduncular fossa has been identified.
Children with this condition have several identifying facial characteristics. A child’s eyebrows are rounder and located higher on the forehead; his ears are small and set low on either side of his head. Often, his tongue will protrude from his mouth. Although the child will have respiratory and vision difficulties, the personality of the child is usually very friendly and happy.
