[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) › Fornix [Nervous system](https://durgical.com/en/anatomy/system/nervous-system/) · [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) # Fornix The fornix is an arched band of nerve fibres running from the hippocampus to the mammillary bodies; it carries signals of the memory circuit. [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=head_neck&select=fornix&side=r) Opens in the Durgical app, no sign-up needed. ## What it is An arched band of fibres from the hippocampus to the mammillary bodies. ## What it does Carries memory circuit signals. ## Key points - Main output of the hippocampus: alveus, fimbria, crus, body and column, ending mostly in the mammillary bodies, with some fibres to the septal nuclei - Papez circuit: hippocampus, fornix, mammillary bodies, mammillothalamic tract, anterior thalamic nucleus, [cingulate gyrus](https://durgical.com/en/anatomy/cingulate-gyrus/), and back to the hippocampus - Wernicke–Korsakoff (thiamine deficiency, often with heavy alcohol use) damages the mammillary bodies and medial thalamus: confusion, eye movement problems, ataxia, then amnesia with confabulation - Bilateral fornix injury, for example during surgery for a colloid cyst of the third ventricle, causes anterograde amnesia ## Key facts **Where** Arches from the hippocampus to the mammillary bodies under the corpus callosum **Blood supply** ACA, PCA branches **Function** Output of the hippocampus (Papez circuit) ## Relations **Course** Fimbria along the [hippocampus](https://durgical.com/en/anatomy/hippocampus/), crus arching up behind the [thalamus](https://durgical.com/en/anatomy/thalamus/) under the splenium (the two crura are linked there by the hippocampal commissure), body under the [corpus callosum](https://durgical.com/en/anatomy/corpus-callosum/), columns curving down in front of the interventricular foramen to the mammillary bodies **Above** Corpus callosum, joined to it in front by the septum pellucidum **Below** Roof of the [third ventricle](https://durgical.com/en/anatomy/third-ventricle/) (tela choroidea with the internal cerebral veins) and the thalamus **In front** Its columns form the front border of the interventricular foramen (of Monro); the [anterior commissure](https://durgical.com/en/anatomy/anterior-commissure/) crosses just in front of them **Lateral** Bodies of the [lateral ventricles](https://durgical.com/en/anatomy/lateral-ventricle/), with the [choroid plexus](https://durgical.com/en/anatomy/choroid-plexus/) attached along its edge ([choroid](https://durgical.com/en/anatomy/choroid/) fissure) ## How to find it On midsagittal MRI it is the thin arched band under the corpus callosum, joined to it by the septum pellucidum, curving down in front of the thalamus to the mammillary body. On coronal images the paired bodies sit at the lower edge of the septum pellucidum. ## On imaging Wernicke encephalopathy: symmetric high T2/FLAIR signal in the medial thalami, mammillary bodies and periaqueductal grey; in chronic Korsakoff syndrome the mammillary bodies shrink. ## Clinical notes - Approaches to the third ventricle (transcallosal, through the interventricular foramen) put the fornix at risk - Glucose given without thiamine to a malnourished person can precipitate Wernicke encephalopathy ## Development The C-shaped growth of the hemisphere, as the [temporal lobe](https://durgical.com/en/anatomy/middle-temporal-gyrus/) swings down and forward, explains why the fornix, the lateral ventricles, the tail of the [caudate nucleus](https://durgical.com/en/anatomy/caudate-nucleus/) and the stria terminalis all arch from the frontal region into the temporal lobe. ## Related conditions - [Alzheimer disease](https://durgical.com/en/conditions/alzheimer-disease/) ## Test yourself Think of the answer, then tap the question to see it. ## Where does the fornix carry the output of the hippocampus? Mostly to the mammillary bodies, through the fimbria, crus, body and column, with some fibres to the septal nuclei. ## What is the sequence of the Papez circuit? Hippocampus, fornix, mammillary bodies, mammillothalamic tract, anterior thalamic nucleus, cingulate gyrus, and back to the hippocampus. ## What does bilateral fornix injury cause, and in which surgery is it at risk? Anterograde amnesia; it is at risk in surgery for a colloid cyst of the third ventricle, as its columns border the interventricular foramen. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/anatomy/fornix/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** fornix TA2 5633 **Official Spanish (DeCS)** Fórnix DeCS D020712 **English (TA2)** Fornix ## Related - [Hippocampus](https://durgical.com/en/anatomy/hippocampus/) Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=34051&filter=ths_termall&q=Fornix,%20Brain); [Neuroanatomy, Limbic System](https://www.ncbi.nlm.nih.gov/books/NBK538491/); [Neuroanatomy, Mammillary Bodies](https://www.ncbi.nlm.nih.gov/books/NBK537192/); Tratado de anatomía humana (9.ª ed.), tomo II, Libro V, cap. VI: Cerebro (configuración exterior e interior, ventrículos, formaciones coroideas, epífisis). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/fornix/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/fornix/