| fourth ventricle | A cavity of irregular tentlike shape extending from the obex rostralward to its communication with the sylvian aqueduct, enclosed between the cerebellum dorsally and the rhombencephalic tegmentum ventrally, having a rhomboid-shaped floor (rhomboid fossa) and a tentlike roof which in its caudal part is formed by the tela choroidea and the posterior medullary velum, in its middle part by the white matter of the cerebellum, and in its narrowing rostral part (recessus superior) by the anterior medullary velum. The fourth ventricle reaches its greatest width at the pontomedullary transition, where it expands laterally behind the cerebellar peduncles into the spoutlike lateral recess, and its greatest height at the fastigial recess, which reaches up into the cerebellar white matter. Direct communication of the brain's ventricle system and the subarachnoid space is established at the level of the fourth ventricle by a median opening in the tela choroidea, the medial aperture of Magendie's foramen, which opens into the cerebellomedullary cistern, and on both sides by the lateral aperture or foramen of Luschka, which connects the lateral recess with the interpeduncular cistern. Synonym: ventriculus quartus, ventricle of rhombencephalon. (05 Mar 2000) |
|---|---|
| fourth ventricle mass | <radiology> IN ADULTS: choroid plexus papilloma, haemangioblastoma, vermian metastasis, arteriovenous malformation (AVM), inflammatory mass/cyst IN KIDS: medulloblastoma, uniform enhancement, homogeneous, ependymoma, patchy enhancement, heterogeneous, calcified (12 Dec 1998) |
| lateral recess of fourth ventricle | The narrow recess of the ventricle that extends laterally over, and down along the side of, the inferior cerebellar peduncle and the overlying cochlear nuclei; at its tip it opens by way of Luschka's foramen into the interopeduncular cistern of the subarachnoid space. By way of this recess, part of the choroid plexus of the fourth ventricle protrudes into the subarachnoid space. Synonym: recessus lateralis ventriculi quarti. (05 Mar 2000) |
| lateral vein of lateral ventricle | A vein draining deep portions of the temporal and parietal lobes; it runs in the lateral wall of the lateral ventricle to terminate in the superior thalamostriate vein. Synonym: vena ventriculi lateralis lateralis, lateral atrial vein, lateral vein of lateral ventricle. (05 Mar 2000) |
| lateral ventricle | A cavity shaped somewhat like a horseshoe in conformity with the general shape of the hemisphere; each lateral ventricle communicates with the third ventricle through the interventricular foramen of Monro, and expands from there forward into the frontal lobe as the anterior horn as well as caudally over the thalamus as the central part or cella media which, behind the thalamus, curves ventrally and laterally, then forward into the temporal lobe as the inferior horn; from the apex of the curve a variably sized posterior horn extends back into the white matter of the occipital lobe. The large choroid plexus of the lateral ventricle invades the cella media and the inferior horn (but not the anterior and posterior horn) from the medial side. Synonym: ventriculus lateralis, ventricle of cerebral hemisphere. (05 Mar 2000) |
| left ventricle | <anatomy> The muscular chamber of the heart which accepts blood from the left atrium and ejects it into the aorta to the systemic circulation. (27 Sep 1997) |
| bladder neoplasms | Cancers or tumours of the bladder. The majority of bladder neoplasms are of the transitional cell variety and are usually papillary and multicentric. (12 Dec 1998) |
| bone marrow neoplasms | Neoplasms located in the bone marrow. They are differentiated from neoplasms composed of bone marrow cells, such as myeloma. most bone marrow neoplasms are metastatic. (12 Dec 1998) |
| breast neoplasms, male | Any neoplasms of the male breast. These occur infrequently in males in developed countries, the incidence being about 1% of that in females. Two-thirds of patients present with intraductal carcinoma. The average age of onset is 60 years for men. Orchiectomy was the standard treatment but it has been replaced by tamoxifen as the initial therapy since oestrogen-receptor-positive tumours are predominant in males. Orchiectomy and mastectomy may be used if initial drug therapy is not successful. The prognosis is worse than that for females. (12 Dec 1998) |
| vascular neoplasms | <oncology> Neoplasms located in vascular tissue or specific veins. They are differentiated from neoplasms, vascular tissue which are neoplasms composed of vascular tissue, such as angiofibroma or haemangioma. (12 Dec 1998) |
| pancreatic cystic neoplasms | <radiology> Microcystic adenoma, glycogen, benign, mucinous cystic neoplasm, macrocystic adenoma, cystadenoma/cystadenocarcinoma, mucin, pre-malignant, Both occur more commonly in women, peak in middle age (12 Dec 1998) |
| pancreatic neoplasms | <radiology> Adenocarcinoma, most common, usually in pancreatic head, nasty (1-2% survival at 1 yr!), cystic neoplasms, slow-growing, more common in women, isleT-cell tumours, soft-tissue tumours (rare), metastases (breast, lung, melanoma, stomach, colon) (12 Dec 1998) |
| mammary neoplasms | Tumours of the mammary gland. Their occurrence is uncommon with the exception of the female dog, in which they account for 25% of all neoplasms. (12 Dec 1998) |
| paranasal sinus neoplasms | Neoplasms or tumours of the paranasal sinuses. Malignant neoplasms are rare, comprising 3% of all head and neck neoplasms. The majority arise in the maxillary sinus with malignancies of the ethmoid sinus constituting virtually all the remaining tumours. (12 Dec 1998) |
| genital neoplasms, male | Neoplasms of the male genitalia. (12 Dec 1998) |