Vestibular function refers to the balance function of the vestibular organ. When the vestibule is stimulated, dysfunction will occur, mainly manifested as nystagmus, vertigo, dumping, etc. If the patient has the above-mentioned symptoms due to pathological changes of the vestibule, It is called spontaneous vestibular symptoms. The occurrence of spontaneous vestibular symptoms indicates that pathological changes surely exist in the vestibule. If the artificial method is used to stimulate to induce vestibular symptoms, this is referred to as vestibular function test. The test can determine the vestibular function and help diagnosis. The specific discussions are as follows.
1. Examination of spontaneous vestibular symptoms
1. Examination of spontaneous nystagmus
Ask the patient to hold his head still, with both eyes staring at the fingers of the examiner who is 50 cm away. Then the eyeballs move upwards, downwards, leftwards and rightwards, follwing the finger. The movement is limited to the angle of 45°to 50°from the midline. Severe strabismus may lead to physiological nystagmus. If nystagmus occurs, pay attention to the type, direction, amplitude of the vibration, severity, frequency, time, etc. of nystagmus. Nystagmus can be divided into fast phase and slow phase. Slow phase results from the fact that the labyrinth is stimulated, which is in agreement with the direction of lymphokinesis; fast phase is the phenomenon that infracortical centre adjusts eyeballs towards the opposite direction, which is contrary to the direction of lymphokinesis. Clinically, fast phase is easy to be observed, so it is used to represent the direction of nystagmus.
- Nystagmus may be divided into three degrees according to the severity.
- First degree: When the patient gazes at the fast phase direction, nystangmus will begin to occur.
- Second degree: When the patient pays attention to the front, nystagmus will occur.
- Third degree: When the patient moves to any direction, nystagmus will occur.
- Nystagmus may be divided into three types, the cause of which may be determined by discriminating the types of nystagmus.
Peripheral labyrinthine nystagmus: It is characterized by horizontal or rotatory nystagmus, with fast phase and slow phase. In the case of mild pathological changes, mystagmus occurs in the affected side mostly; in the case of severe pathological changes, nystagmus occurs in the healthy side on most occasions. Simultaneously, vertigo exists, the severity of which is in agreement with the severity of nystagmus, and which is possibly accompanied by nausea and vomiting. Bodily dumping or deviation orientation test slants to the slow phase direction of nystagmus.
Central nystagmus: It is characterized by severe nystagmus and indefinite directions. Possibly, the eyeballs vibrate horizontally, or vertically, or rotatively, etc. This type of nystagmus exists for several years or for a couple of months, and is caused by diseases of central nervous system and accompanied by the symptoms of diseases of central nervous system. Nausea, vomiting, dumping or deviation orientation are not related to the severity of nystagmus.
Ocular nystagmus: It is characterized by fast vibration of eyeballs towards various directions and caused by ocular diseases. Nystagmus may exist for several years and is often accompanied by dizziness which will disappear or abate when the patient closes his eyes or stops gazing.
2. Examination of symptoms of spontaneous dumping
Ask the patient to stand upright, with eyes closed and feet closed up. Then observe whether dumping exists or not. If dumping is due to vestibular pathological changes, the direction of dumping is in agreement with the slow phase of nystagmus.
3. Deviation orientation test
A normal person can be conscious of the position where he is and make out the directions even if he closes his eyes. Orientation disturbance will occur in the case of vestibular pathological changes or after the stimulation during the test if visual coordination is not adopted. This is referred to as deviation orientation. The application of this phenomenon in vestibular function test is called deviation orientation test. In terms of the test methods, the examiner sits before the patient. Then the former extends one finger, asking the latter to raise one upper limb and move downwards. Next, the examiner uses his index finger to touch the examinee’s fingers: first, conduct the test while the examinee is gazing. Afterwards, conduct it after the examinee is asked to close his eyes. If the movement of the patient’s upper limb slants to one side, it is termed as deviation orientation sign positive. In the case of vertigo occurring after the vestibule is stimulated, the patient will feel that the things around him are going away from him and moving. The patient will try to touch the examiner’s fingers, with his upper limb slanting to one side in order to compensate for the deviation. In this case, deviation orientation will occur.