[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/) › Third ventricle [Nervous system](https://durgical.com/en/anatomy/system/nervous-system/) · [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) # Third ventricle The third ventricle is a narrow fluid-filled cavity in the midline of the brain between the two thalami; it passes cerebrospinal fluid toward the aqueduct. [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=head_neck&select=third_ventricle&side=r) Opens in the Durgical app, no sign-up needed. ## What it is A narrow midline cavity between the two thalami. ## What it does Passes cerebrospinal fluid from the [lateral ventricles](https://durgical.com/en/anatomy/lateral-ventricle/) to the aqueduct. ## Key points - Floor, front to back: optic chiasm, infundibulum, tuber cinereum, mammillary bodies, posterior perforated substance; its recesses are optic, infundibular, pineal and suprapineal - Colloid cyst at the front of the roof can plug both interventricular foramina: positional headache, sudden hydrocephalus and even sudden death - Endoscopic third ventriculostomy opens the thin floor between the infundibulum and the mammillary bodies into the cisterns, bypassing a block at the cerebral aqueduct; the [basilar artery](https://durgical.com/en/anatomy/basilar-artery/) lies just behind ## Key facts **Where** Midline between the thalami **Blood supply** Choroid plexus: posterior choroidal arteries **Function** CSF -> cerebral aqueduct ## Relations **Lateral** [Thalamus](https://durgical.com/en/anatomy/thalamus/) above the hypothalamic sulcus and [hypothalamus](https://durgical.com/en/anatomy/hypothalamus/) below; the interthalamic adhesion crosses it in most brains **Above** Tela choroidea with its [choroid plexus](https://durgical.com/en/anatomy/choroid-plexus/) and the internal cerebral veins, then the [fornix](https://durgical.com/en/anatomy/fornix/) and the [corpus callosum](https://durgical.com/en/anatomy/corpus-callosum/) **In front** Lamina terminalis, [anterior commissure](https://durgical.com/en/anatomy/anterior-commissure/) and columns of the fornix; the interventricular foramina at its upper front corners **Below** [Optic chiasm](https://durgical.com/en/anatomy/optic-chiasm/) and hypothalamus, with the infundibulum leading down to the [pituitary gland](https://durgical.com/en/anatomy/pituitary-gland/) **Behind** [Pineal gland](https://durgical.com/en/anatomy/pineal-gland/), habenular and posterior commissures, and the opening of the [cerebral aqueduct](https://durgical.com/en/anatomy/aqueduct-of-midbrain/) ## How to find it On a midline sagittal MRI it is the narrow slit between the two thalami. At endoscopy from the frontal horn, the interventricular foramen is found by following the choroid plexus and the thalamostriate and septal veins, which meet at its back edge; through it the mammillary bodies and the thin floor come into view. ## On imaging On sagittal MRI a block at the aqueduct makes the third ventricle balloon, with its floor bowing down and the recesses rounding out, the features checked before a ventriculostomy. A colloid cyst is typically a small, round, often bright (hyperdense) lesion at the foramina on CT. ## Clinical notes - Craniopharyngioma and other suprasellar masses can push up into the floor, causing hydrocephalus plus hypothalamic signs such as great thirst and urine output (diabetes insipidus), weight gain or poor growth - The transcallosal approach reaches it from above, through the corpus callosum and then the interventricular foramen or the gap between the fornices; damage to both fornices can impair the forming of new memories - Hypothalamic hamartoma, a mass in its floor or wall, classically causes laughing seizures (gelastic epilepsy) and early puberty ## Anatomical variants - The interthalamic adhesion (massa intermedia) bridges the cavity in most brains but is absent in about 15–20%, more often in men; it is sometimes double; its absence has no known effect ## Development It is the cavity of the diencephalon; the lamina terminalis is the closed front end of the neural tube. ## Related conditions - [Hydrocephalus](https://durgical.com/en/conditions/hydrocephalus/) ## Test yourself Think of the answer, then tap the question to see it. ## What forms the lateral walls of the third ventricle? The thalamus above the hypothalamic sulcus and the hypothalamus below; the interthalamic adhesion crosses it in most brains. ## Why can a colloid cyst of the third ventricle be dangerous? At the front of the roof it can plug both interventricular foramina: positional headache, sudden hydrocephalus and even sudden death. ## Where is the opening made in endoscopic third ventriculostomy? In the thin floor between the infundibulum and the mammillary bodies, into the cisterns, bypassing an aqueduct block; the basilar artery lies just behind. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/anatomy/third-ventricle/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** ventriculus tertius TA2 5769 **Official Spanish (DeCS)** Tercer Ventrículo DeCS D020542 **English (TA2)** Third ventricle ## Related - [Thalamus](https://durgical.com/en/anatomy/thalamus/) - [Cerebral aqueduct](https://durgical.com/en/anatomy/aqueduct-of-midbrain/) Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=34050&filter=ths_termall&q=Third%20Ventricle); [Neuroanatomy, Ventricular System](https://www.ncbi.nlm.nih.gov/books/NBK532932/); [13.3 Circulation and the Central Nervous System](https://openstax.org/books/anatomy-and-physiology-2e/pages/13-3-circulation-and-the-central-nervous-system) (OpenStax (Rice University), 2022) · adapted, [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/); 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/third-ventricle/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/third-ventricle/