The CN VIII only contains sensory fibres. As suggested by its name, this nerve transmits impulses from the vestibular apparatus and the cochlea. The nerve enters the brainstem at the cerebellopontine angle. The examination should also aim to determine whether there is a sensory lesion (auditory canal, middle ear, labyrinth) or one involving the peripheral nerve or the central nervous system.
Hearing examination
Procedure
When examining hearing you should try to distinguish between conductive deafness and sensorineural (perceptive) deafness. This should be done using tuning fork tests.
Weber test
- Firmly strike the tuning fork (512Hz) against the ulnar side of your hand, for example.
- Firmly place the tuning fork on the middle of the patient’s head [Figure 25].
- Ask the patient where they best hear the sound (left, right or in the middle).
- If the patient is unsure, have them simulate conductive deafness by putting their finger in one ear and then repeat the procedure. The sound should normally lateralise to the closed ear.
- Then repeat the procedure with both ears open.
Figure 25
Rinne test
- Strike the tuning fork and firmly place the foot of the tuning fork on the patient’s mastoid process [Figure 26].
- Ask the patient to indicate when they no longer hear the sound.
- Next hold the vibrating arms of the tuning fork in front of the patient’s ear so that the arms are horizontal with the auditory canal [Figure 27].
- Ask whether the patient hears the sound now.
- You can also alternately hold the vibrating tuning fork in front of the patient’s ear and on their mastoid process.
- Inquire at which point the patient best hears the sound.
- The Rinne test is considered abnormal if the bone conduction is better than air conduction.
Figure 26
Figure 27
Schwabach test
- Strike the tuning fork and firmly place the foot of the tuning fork on the patient’s mastoid process.
- Ask the patient to indicate when they no longer hear the sound.
- Now place the foot of the tuning fork on your own mastoid process. If you are able to hear the sound, the Schwabach test is abnormal.
Interpretation
If you detect lateralisation with the Weber test, for example to the right, it may indicate right-sided conductive deafness or left-sided sensorineural deafness.
Right-sided conductive deafness should lead to an abnormal Rinne test on the right side. This is often not the case because air conduction is so much better than bone conduction that a slight loss of air conduction will not lead to an abnormal Rinne test. A clearly abnormal Rinne test does indicate conductive deafness.
Left-sided sensorineural deafness should lead to an abnormal Schwabach test on the left side. If there is conductive deafness, it may be caused by the presence of cerumen or a middle ear condition. In the presence of sensorineural deafness, specialised examination techniques are required to differentiate between a pathology involving the cochlea, the cranial nerve or central connections.
The examination of the vestibular system
When examining the vestibular system (generally carried out if the patient complains of a spinning sensation or dizziness or instability), you should be aware that the patient is using impulses from the visual system, the vestibular system and the proprioceptive system to maintain their balance. All three systems provide the patient with information about their spatial position and movement. This information is integrated in the central vestibular system. Therefore, if a patient has a balance problem, you will have to examine all these systems. If, during the history-taking, the patient clearly indicates a constant or episodic sensation that they or the room is spinning, a condition involving the vestibular system is likely. The fact that the patient also often suffers from nausea, vomiting and sweating is related to the connections between this system and autonomic regulatory centres.
Procedure
The examination is split into two parts; the assessment of balance and the detection of nystagmus.
To examine balance, you can use Romberg’s test and, to increase sensitivity, Barré’s test or Jendrassik’s manoeuvre.
NB: In the case of a severe vestibular condition a patient will not even be able to stand and even when sitting will show a tendency to fall.
The nystagmus examination should be carried out as follows:
- Have the patient sit up in front of you.
- Dim the light in the examination room.
- Hold up a finger about 75 cm from the patient’s face and have the patient follow your finger with just their eyes.
NB: The gaze angle with the eyes in a neutral position should not be more than 45°. Nystagmus that occurs at a larger gaze angle may be physiological. - Have the patient look to the left, right, up and down for about 20 seconds each time (the angle at neutral eye position should be about 30°).
- Observe whether nystagmus develops. This is a rhythmic conjugate eye movement, lasting longer than a few seconds, in which rapid and slow phases can be distinguished.
- Describe the direction of the slow and rapid phase of the nystagmus.
- A nystagmus is named according to the direction of the rapid phase, the phase in which the eyes return to their original position.
- Determine whether a nystagmus occurs:
- When the gaze is in the direction of the rapid phase (grade I)
- When the gaze is straight ahead (grade II)
- When the gaze is in the direction of the slow phase (grade III).
Examination to detect positional vertigo
Hallpike manoeuvre or ‘tipping test’
Procedure
- The examination room should be dimly lit.
- The patient should sit on the examination table in such a way that when they lie down, their head just hangs over the end of the table.
- You should stand next to the patient and hold their head between your hands [Figure 28].
- Now lay the patient down on their back in one smooth movement, turning their head towards you in a slightly over-flexed position [Figure 29].
- Look carefully at the patient’s eyes for at least 30 seconds to determine whether nystagmus occurs and ask whether they are experiencing any dizziness [Figure 30]. Ask the patient to look at your finger tip, moving from the central position up and down.
- In one smooth movement return the patient to the original position (sitting upright and looking straight ahead).
- Look at the patient’s eyes again to assess whether nystagmus occurs and ask whether the patient is experiencing any dizziness.
- Repeat the manoeuvre, this time turning the patient’s head away from you.
Figure 28
Figure 29
Figure 30
Interpretation
Four types of nystagmus can be identified:
- Spontaneous nystagmus in the absence of visual fixation. The nystagmus disappears or improves upon visual fixation.
- Spontaneous nystagmus upon visual fixation. The nystagmus is visible in the absence of provocation.
- Positional nystagmus. This occurs upon rapid head movements, as with the Hallpike manoeuvre.
- Optokinetic nystagmus, or one which is induced by increased velocity. This is physiological.
Classification can also be carried out on the basis of the direction of the nystagmus. A distinction is made between horizontal, vertical and rotational.
With the following findings you should consider peripheral conditions, in other words those involving the cochlear labyrinth or peripheral nerve:
- nystagmus which only occurs or becomes far more pronounced during examination using Frenzel glasses,
- a tendency to fall in the same direction as the slow phase of the nystagmus,
- positional nystagmus,
- nystagmus accompanied by impaired perception.
In the case of the following findings you should consider a central condition, for example one located in the vestibulocerebellar connections:
- spontaneous nystagmus in the absence of dizziness,
- fixation nystagmus to the right when looking to the right and to the left when looking to the left,
- dissociated nystagmus (nystagmus which alternates between the two eyes),
- vertical or rotational nystagmus.NB: Slow progressive diseases involving the peripheral nerve (for example a tumour) are not always accompanied by vertigo and / or nystagmus, because of central compensation mechanisms.