| occult hydrocephalus | <neurology> A brain disorder caused by blockage of the flow of cerebrospinal fluid (CSF), with enlargement of the ventricles of the brain (keep the pressure normal) and compression of brain tissue. Brain atrophy is the result. In this condition the CSF is produced normally but not reabsorbed. Symptom onset is gradual. A key feature is dementia. Treatment is surgical (VP shunt). (13 Nov 1997) |
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| occult | Obscure, concealed from observation, difficult to understand. (18 Nov 1997) |
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| occult bleeding | See: occult blood. (05 Mar 2000) |
| occult blood | Blood that is in the faeces or vomitus that is not obvious by general inspection. Used as a diagnostic screening test for colon cancer. Tests for occult blood are generally colourimetric. Stool sample will turn blue when a particular chemical reagent is mixed with the specimen on test paper. Kits for measuring occult blood in the stools are now available at most drug stores. (27 Sep 1997) |
| occult border of nail | The proximal border of the nail entirely covered by the nail wall. Synonym: margo occultus unguis, occult border of nail. (05 Mar 2000) |
| occult carcinoma | <tumour> A small carcinoma, either asymptomatic or giving rise to metastases without symptoms due to the primary carcinoma. (05 Mar 2000) |
| occult fracture | A condition in which there are clinical signs of fracture but no X-ray evidence; after 3 or 4 weeks X-ray imaging shows new bone formation. (05 Mar 2000) |
| faecal occult blood test | <investigation> A chemical test that measures the presence of fresh or decomposed blood. Blood may arise from bleeding anywhere along the gastrointestinal tract, from the mouth to the anus. An easy to perform colourmetric test. Occult means hidden. (08 Mar 2000) |
| communicating hydrocephalus | Type of hydrocephalus in which there is an abnormality in cerebrospinal fluid absorption; there is no obstruction to cerebrospinal fluid flow in the ventricular system or where the cerebrospinal fluid passes into the spinal canal. (05 Mar 2000) |
| congenital hydrocephalus | Hydrocephalus due to a developmental defect of the brain. Synonym: primary hydrocephalus. (05 Mar 2000) |
| postmeningitic hydrocephalus | Ventricular dilation following meningitis and secondary to obstruction of cerebrospinal fluid pathways. (05 Mar 2000) |
| posttraumatic hydrocephalus | Ventricular dilation following injury, due either to impaired circulation and/or absorption of cerebrospinal fluid or due to loss of brain substance (h. Ex vacuo). (05 Mar 2000) |
| primary hydrocephalus | Hydrocephalus due to a developmental defect of the brain. Synonym: primary hydrocephalus. (05 Mar 2000) |
| secondary hydrocephalus | An accumulation of fluid in the cranial cavity, due to meningitis or obstruction to the venous flow. (05 Mar 2000) |
| hydrocephalus | A condition marked by dilatation of the cerebral ventricles, most often occurring secondarily to obstruction of the cerebrospinal fluid pathways and accompanied by an accumulation of cerebrospinal fluid within the skull, the fluid is usually under increased pressure, but occasionally may be normal or nearly so. It is typically characterised by enlargement of the head, prominence of the forehead, brain atrophy, mental deterioration and convulsions, may be congenital or acquired and may be of sudden onset (acute h.) or be slowly progressive (chronic or primary b.). Origin: Gr. Kephal = head (18 Nov 1997) |
| hydrocephalus ex vacuo | Hydrocephalus due to loss or atrophy of brain tissue; less commonly associated with raised intracranial pressure. (05 Mar 2000) |