Dolls Eye Movement In Response To Irrigation Of Tympanic Membranes Of Ears

The cochlear branch subserves hearing, The fibres arise from the end organs in the inner ear. They pass centrally along the internal acoustic meatus and cross the cerebellopontine CSF cistern to enter the lateral brain stem at the

Preserved function in upper face

Loss of nasolabial fold

Mouth deviates to normal side

Nasolabial Fold Vii

Bell's phenomenon

Loss of frontal wrinkling

Loss of nasolabial fold

Mouth deviates to normal side

Fig. 6.21 Types of facial weakness. Caused in IB by lesion of precenfral area or pyramidal Iract (upper motor neurone); El by lesion of facial nerve or nucleus (lower motor neurone), also showing Bell's phenomenon.

Bell's phenomenon

Fig. 6.21 Types of facial weakness. Caused in IB by lesion of precenfral area or pyramidal Iract (upper motor neurone); El by lesion of facial nerve or nucleus (lower motor neurone), also showing Bell's phenomenon.

Preserved function in upper face

Loss of frontal wrinkling

Loss of nasolabial fold

Mouth deviates to normal side

Loss of nasolabial fold

Mouth deviates to normal side

TABLE 6.16 Common causes of VII nerve palsies

Unilateral

Bilateral

Upper motor neurone type weakness

Usually vascular

Often vascular

Cerebral tumour

Consider motor neurone disease

Multiple sclerosis

Lower motor neurone type weakness

Usually Bell's palsy

Neurosarcoidosis

Consider parotid tumour,

Myasthenia gravis

head injuries,

Generalised polyneuropathies

skull base tumours

(Guillain—Barre syndrome)

Some myopathies (e.g. myotonic dystrophy)

pontomedullary junction. The fibres then synapse in the cochlear (dorsal, ventral) and vestibular (inferior, superior, lateral and medial) nuclear complexes. From the cochlear nucleus second-order fibres ascend to the superior olivary and trapezoid nuclei. Central libres then ascend up the lateral lemniscus, and synapse in the inferior colliculus and medial geniculate body (MGB) before entering the primary auditory cortex in the superior temporal gyrus (areas 41 and 42). The ascending auditory pathways decussate al several levels so that each cortical region receives impulses from both ears.

The inferior and superior vestibular branches and the associated vestibular pathways are very important in the maintenance of correct posture, eye coordination and movement.

The vestibular part of the VIII is also the afferent limb of both the oculoeephalie (doll's eye reflex) and oculo-vestibular (caloric) reflexes. The oculocephalic reflex involves conjugate movements of the eyes in response to changes in head position. The oculovestibular reflex involves elicitation of eye movements following irrigation of the external ear canal by either cold or warm water.

The central connections of the four vestibular nuclei are complcx. Through fibres in the MLF they interconnect with the III, IV and VI cranial nuclei. Other fibres project to the cerebellar vermis and flocculus, while others descend in the vestibulospinal tracts. Ascending fibres relay through the medial geniculate body (MGB) to the posterior temporal lobe.

Examination

In clinical practice deafness or impaired hearfiig is best studied using audiometry and brain-stem evoked.potentials to determine their precise aetiology, 'Bed-side' tests are relatively crude but should give some indication as to whether hearing is normal, abnormal or asymmetrical.

Whispering numbers or words tests hearing for higher frequencies in particular. Rinne's test determines whether air conduction is better than bone conduction. Normally the air-conducted sound is perceived as louder. Weber's lateralising test provides supplementary information about the nature of any hearing impairment. Normally, the sound appears to arise in (he midline (Fig. 6.22).

Vestibular function can be assessed clinically by testing the oculocephalic reflex, or doll's eye manoeuvre, and by induction of positional nystagmus. In the former, the normal response is for the patient's eyes to deviate to the left as the patient's head is turned to the right and vice versa on contralateral head turning. If the patient's head is briskly extended the patient's eyes should move downwards. In the doll's eye manoeuvre, the normal response to unilateral irrigation with cool water is for the patient to develop nystagmus towards the contralateral side. If the ear is irrigated with warm water the patient will have nystagmus towards the side of the irrigated ear.

Weber Test
Fig. 6.22 Weber's test.

Usually caloric vestibular tests are carried out in a special laboratory set up to record eye movement electronically.

Examination sequence

Hearing

□ Mask bearing in Ibe non-tested ear by either rubbing the forefinger and thumb together over the external acoustic meatus or gently massaging the patient's external acoustic meatus with the examiner's forelinger.

□ Test hearing in cach car by asking the patient to repeat whispered numbers or words.

□ Perform Rinne's test by placing a vibrating tuning fork (256 or 512 Hz) on the mastoid proccss (to assess bone conduction of sound } then just lateral to the external ear (Fig. 6.23).

□ Ask the patient which of the two sounds appears louder.

□ Perform Weber's test by placing the strongly vibrating tuning fork to the middle of the forehead. Ask the patient where the sound is heard loudest (in the midline or preferentially to one side).

□ Examine the external acoustic canal using an auroscope. Visualise the tympanic membranes and note any abnormal vascularity of the membrane or retrotympanic fluid level (p. 50).

Induction of positional nystagmus (Hallpike's test)

□ Support the patient's head, with eyes open, and lower it briskly below the horizontal plane of the couch, turning the head to one side (Fig. 6.24).

Air Conduction Test Tuning Fork

Fig. 6.23 Rinne's test. [A] Testing bone conduction. IBJ Testing air conduction.

Fig. 6.23 Rinne's test. [A] Testing bone conduction. IBJ Testing air conduction.

□ Sit the patient up again, and repeat the test, turning the head to the other side.

□ Note the response of the eyes to head movement.

Oculovestibular reflex

□ Inspect the canal to ensure that the tympanic membranes are visualised.

□ If necessary, remove any impacted wax.

□ Gently irrigate the canal with patienl's eyes open using water at either 30°C or 44°C and observe the response.

Oculovestibular Response
Fig. 6.24 Testing for positional nystagmus.

Oculocephalic reflex

□ Perform llie lesi with the patient lying down.

□ Stand above and behind the patient at the head of the bed.

□ Slightly Hex and support the patient's head.

□ Briskly rotate the head from one side to the other and note lateral movements of the eyes.

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