Cranial Nerve Examination for mbbs .pptx

Mbbs cns exam

1. Cranial nerves examination 1, 5, 7, 8, 9, 10, 11, 12

2. Olfactory nerve Anatomy - the olfactory receptors present in the septum and lateral wall , give central processes and penetrate the cribriform plate . This then enters the olfactory bulb leading into olfactory tract . The tracts ends at the pyriform lobe of the temporal lobe , and then onto amygdala , septal nuclei and hypothalamus . The sense of smell is tested by asking the patient to sniff various non irritating substances separately in each nostril and identify them . Parosmia – perversion of smell , Cacosmia – unpleasant odours

3. Anosmia – causes

4. Trigeminal nerve - anatomy

5. Trigeminal nerve testing The motor function can be tested by asking the patient to clench his teeth , and seeing the prominence of the temporalis and masseter on both sides . Affected side wont have a prominence . The patient is asked to keep the jaw open , if paralysis is present , the jaw is pushed by the healthy lateral pterygoid muscle . The sensory function is tested in all three divisions separately , comparing both sides . Pain , temperature and light touch are tested. Lesions at or proximal to gasserian ganglion involve the complete ipsilateral face . Lesions within the brain stem and upper cervical cord result in onion skin distribution of sensory loss .

6. Trigeminal nerve reflexes Conjunctival and corneal reflexes Afferent – ophthalmic division of trigeminal nerve Reflex centre – pons Efferent – facial nerve Method – the patient should turn his eyes to opposite direction . The examiner should the cornea or conjunctiva from the side with wisp of cotton . In response to this stimulus , normally there is bilateral blinking or closing of the eyes . Jaw jerk – afferent – sensory portion of trigeminal nerve Reflex – pons Method – the examiner places his index finger over the middle of the patients chin , holding the mouth slightly open . He then taps his finger with the hammer . Normal response is slight and consists of closure of the mouth .

7. Facial nerve – anatomy

8. Facial nerve testing and diagnosis A. asymmetry of the face B. stasis of food in the mouth C. dribbling of saliva from the angle of mouth D. inability to close the eyes Signs – 1. orbicularis oculi – difficulty in closing the eyelids and bells phenomenon , involuntary blinking is abolished . 2. nasociliary – frowning of the forehead is lost 3. frontal head of occipitofrontalis – wrinkling of forehead is lost 4. orbicularis oris – whistling is not possible 5. buccinator – cheek puffs out with expiration 6. muscles of facial expression – flattening of the nasolabial fold , drooping of the angle of mouth on the affected side , crooked smile and laugh

9. Auditory nerve , nuclei and anatomy

10. Auditory pathway

11. Auditory tests Rinne’s test – a vibrating tuning fork is placed in front of the ear (air conduction )and then on the mastoid bone (bone conduction) . Normally , air conduction is better than bone conduction . In middle ear disease , bone conduction is better than air conduction . In nerve deafness , air conduction is better than bone conduction but both are depressed . Weber’s test – a vibrating tuning fork is placed over the forehead in the centre . Normally , vibrations are heard equally on both the sides . In middle ear disease , it is better heard on the affected side because external sound interfering with the vibrations is less on the affected side . In nerve deafness , the vibrations are heard better on the healthy side . Vestibular function - derangement of vestibular function usually causes vertigo , dzziness , nausea and unsteady gait .calorie and rotational tests are employed to produce change in the endolymph current in the semicircular canals . This results in nausea , dizziness and horizontal nystagmus when the vestibular apparatus is intact . These will be absent when vestibular function is lost .

12. Ninth , tenth and eleventh nerve anatomy The ninth , tenth and eleventh nerves arise in that order from above downwards , in an elongated nucleus in the floor of the fourth ventricle . They emerge along the lateral aspect of the medulla . The spinal part pf the eleventh nerve (accessory)from the lateral columns of the spinal cord passes up through the foramen magnum and joins the cranial part of the accessory nerve and emerges with it through the jugular foramen . The ninth nerve supplies the sensations including the taste from posterior tongue . Also supplies middle constrictor of pharynx and stylopharyngeus . The tenth nerve is motor for soft palate , pharynx and larynx . It is sensory and motor for the respiratory passages , the heart and the abdominal viscera . The eleventh nerve is pure motor for innervation of the larynx , pharynx , sternomastoid and trapezius .

13. 9,10,11 - testing The sensory part can be tested by testing the superficial as well as the taste sensations over the posterior one third of the tongue . The motor function is tested as follows – The patient is asked to open the mouth and say ‘ah’ and palatal movements on both the sides are noted . Normally they are equal and uvula is in the centre . In unilateral palatal palsy , the median raphe is pulled to the normal side , as palatal movements on the affected side are absent . In bilateral paralysis , the whole palate remains motionless . The sternomastoid muscle is tested by asking the patient to rotate his chin to the opposite side . In unilateral paralysis, the chin is deviated to the affected side and there is impairment of rotation of the chin to the opposite side .

14. Gag reflex - Reflex centre – medulla Efferent – vagus Method – stimulation of the posterior wall by a tongue blade or a cotton applicator results in elevation and constriction of pharyngeal musculature accompanied by retraction of the tongue . Significance – the reflex may be absent or brisk in hysteria . The reflex is lost in lesions of ninth and tenth nerves .

15. Twelfth nerve – anatomy

16. 12 nerve testing - The tongue should be observed at rest and on protrusion and various movements are noted . Unilateral lesion may cause paresis , atrophy , furrowing , fibrillations and fasciculations on the affected half of the tongue . On protrusion , the tongue deviates to the paralyzed side due to unopposed action of the opposite genioglossus . Bilateral weakness in addition , causes dysphagia and dyspnea when the flaccid tongue falls back and obstructs the pharynx . Dysarthria especially for d and t phenomes occur .