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vestibular function test

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Updated: Sunday, Jul 25,2010, 4:06:35 PM
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1. caloric test

Pour water of 30℃ and 44℃ (water cooler than body temperature and water warmer than body temperature) respectively into the external auditory canal to reach the drum membrane. Than observe the amplitude of the vibration, frequency, direction and time of the examinee’s nystagmus to understand the examinee’s vestibular function.

2. Rotation test

Ask the patient to sit in a rotary test chair, with feet treading on the footboard. Then the patient holds his head in a position slightly bending forward at the bilateral horizontal semicircular canals will be in horizontal position. Rotate the chair to the right side for 10 cycles at the rate of 10 cycles/20 sec. Suddenly, stop the chair. At this time, ask the patient to notice the front. Observe the direction, type and time of nystagmus. After a five-to-ten-minute rest, rotate the chair to the left side in the same way. Superior vertical and posterior vertical semicircular canals can be examined by holding the head in a position bending backward at the angle of 60℃ or bending forward at the angle of 120℃.

In the case of horizontal semicircular canal test, horizontal nystagmus occurs; in the case of vertical semicircular canal test, rotatory nystagmus appears.

When the patient’s head bends forward at the angle of 30℃ and the rightward rotation is stopped suddenly, the endolymphatic liquid inside the horizontal semicircular canal at the left side will flow to ampulla, giving rise to nystagmus with fast phase slanting to the left. Normal nystagmus lasts 30 seconds. If nystagmus lasts one to three minutes, this does not necessarily mean vestibular pathological changes, but possibly vestibular sensitiveness. If nystagmus lasts less than 20 seconds, this indicates the vestibule is unsusceptible to stimulation. Besides, vestibular pathological changes often make nystagmus time short as well.

1. Fistula test

Fistula test is to check whether there exists fistula on the bone wall of the horizontal semicircular canal or not to enter lymph space due to pathological changes( especially erosion of cholesteatoma). Methods: Place a pneumatic otoscope into the external acoustic meatus and fasten it. Then press the rubber balloon to increase the pressure of the tympanic cavity. If fistula exists, the membranous labyrinth will be simulated by the pressure. In this case, nystagmus or mild light-headedness will occur. With eyeball vibration slanting to the affected side. If the fistula is blocked by granulation, or labyrinth has been damaged, no reaction will appear even if there exits fistula.

2. Glycerine test

Take glycerine added to equal amount of physiological saline on an empty stomach according to the dosage of 1.2to 1.5g/kg (body weight). Test pure tome once every hour before and after the administration, altogether for three times. If the hearing of the speech frequency or other frequencies in the affected side is over 15 decibels better than that of before administration, it is termed as glycerine test positive. Labyrinthine hydrops may exist in the patient with glycerine test positive.

Tags: function vestibular

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