| phi phenomenon | An illusion of movement, which occurs by means of successive visual impressions at intervals of 1/15 to 1/20 sec; when an occluder is passed from one eye to the other while a small distant light is observed, the light seems to move with the occluder in exophoria, but in an opposite direction in oesophoria. (05 Mar 2000) |
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| Rumpel-Leede phenomenon | Appearance of petechiae in an area following application of vascular constriction, such as by a tourniquet, usually after 10 minutes but can appear after shorter period, such as following application of tourniquet to draw blood specimen or use of blood pressure cuff. Due to capillary fragility or abnormal platelet numbers (e.g. Thrombocytopenia) or function. (05 Mar 2000) |
| Rust's phenomenon | In cancer or caries of the upper cervical vertebrae, the patient will always support the head by the hands when changing from the recumbent to the sitting posture or the reverse. (05 Mar 2000) |
| misdirection phenomenon | Misdirected regrowth of nerve fibres seen for example, after oculomotor nerve injury. Synonym: misdirection phenomenon. (05 Mar 2000) |
| Mitsuo's phenomenon | Restoration of the normal colour of the fundus with dark adaptation in Oguchi's disease. (05 Mar 2000) |
| cogwheel phenomenon | A sudden brief halt in usually smooth respiration or other motor activity. Synonym: Negro's phenomenon. (05 Mar 2000) |
| Wenckebach phenomenon | Progressive lengthening of conduction time in any cardiac tissue (most often the A-V node or junction) with ultimate dropping of a beat (A-V Wenckebach) or reversion to the initial conduction time (as in QRS Wenckebach). (05 Mar 2000) |
| Westphal-Piltz phenomenon | A constriction of both pupils when an effort is made to close eyelids forcibly held apart. A variant of the pupil response to near vision. Synonym: Galassi's pupillary phenomenon, Gifford's reflex, lid-closure reaction, orbicularis phenomenon, orbicularis pupillary reflex, Piltz sign, Westphal's pupillary reflex, Westphal-Piltz phenomenon. (05 Mar 2000) |
| Westphal's phenomenon | <clinical sign> Abolition of the patellar tendon reflex, in tabes and certain other diseases of the spinal cord, and occasionally also in brain disease. Synonym: Erb sign, Westphal's phenomenon, Westphal's sign, Westphal-Erb sign. (05 Mar 2000) |
| Wever-Bray phenomenon | The action potentials in the acoustic nerve that correspond to auditory stimuli reaching the cochlea. (05 Mar 2000) |
| constancy phenomenon | In perception, the tendency for brightness, colour, size, or shape to remain relatively perceptually constant despite real changes in colour, size, shape or other conditions of observation. (05 Mar 2000) |
| courvoisier phenomenon | <radiology> In the presence of jaundice: small gall bladder most likely to be cholecystitis / impacted stone (gall bladder chronically inflamed, scarred), large gall bladder most likely to be NEOPLASM (gall bladder intrinsically normal, can dilate), pancreatic head, cholangiocarcinoma (distal common bile duct), ampulla of Vater, duodenal papilla (12 Dec 1998) |
| Pool's phenomenon | In tetany, spasm both of the extensor muscles of the knee and of the calf muscles when the extended leg is flexed at the hip. Synonym: leg phenomenon, Pool-Schlesinger sign, Schlesinger's sign. In tetany, contraction of the arm muscles following the stretching of the brachial plexus by elevation of the arm above the head with the forearm extended, resembles the contraction resulting from stimulation of the ulnar nerve. Synonym: arm phenomenon. (05 Mar 2000) |
| crossed phrenic phenomenon | Hemisection of the cord above the exit of the phrenic nerve paralyzes the ipsilateral half of the diaphragm; if the contralateral phrenic nerve is then sectioned or blocked, contractions on the ipsilateral side are resumed. (05 Mar 2000) |
| Cushing phenomenon | A rise in systemic blood pressure when the intracranial pressure acutely increases, usually in excess of 50% of the systolic arterial pressure. Synonym: Cushing effect, Cushing response. (05 Mar 2000) |