| Grasset's phenomenon | In organic paralysis of the lower extremity, the patient, lying on his back, can raise either limb separately, but not both together. Synonym: Grasset-Gaussel phenomenon. (05 Mar 2000) |
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| peroneal phenomenon | Tapping the peroneal nerve below the head of the fibula causes dorsiflexion and abduction of the foot. (05 Mar 2000) |
| Ritter-Rollet phenomenon | On equal electrical stimulation of motor nerve trunks, the flexor and abductor muscle groups react more readily than the extensors and adductors. (05 Mar 2000) |
| Pfeiffer's phenomenon | The alteration and complete disintegration of cholera vibrios when introduced into the peritoneal cavity of an immunised guinea pig, or into that of a normal one if immune serum is injected at the same time; extended to include bacteriolysis in general. (05 Mar 2000) |
| Gunn phenomenon | <syndrome> An increase in the width of the eye lids during chewing, sometimes with a rhythmic elevation of the upper lid when the mouth is open and ptosis when the mouth is closed. Synonym: Gunn phenomenon, Gunn's syndrome, jaw-winking phenomenon, jaw-working reflex, Marcus Gunn phenomenon, Marcus Gunn syndrome. (05 Mar 2000) |
| R-on-T phenomenon | A premature ventricular (QRS) complex in the electrocardiogram interrupting the T wave of the preceding beat; often predisposes to serious ventricular arrhythmias. (05 Mar 2000) |
| phenomenon | Origin: L. Phaenomenon, Gr. Fainomenon, fr. Fainesqai to appear, fainein to show. See Phantom. 1. An appearance; anything visible; whatever, in matter or spirit, is apparent to, or is apprehended by, observation; as, the phenomena of heat, light, or electricity; phenomena of imagination or memory. "In the phenomena of the material world, and in many of the phenomena of mind." (Stewart) 2. That which strikes one as strange, unusual, or unaccountable; an extraordinary or very remarkable person, thing, or occurrence; as, a musical phenomenon. Source: Websters Dictionary (01 Mar 1998) |
| 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) |
| 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) |