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Writer's pictureMedicine Revision Crash Course

Cranial Nerve Examination


Equipment needed:

  • Torch

  • Snellen chart

  • Ophthalmoscope

  • Cotton wool

  • Neuro tip

  • Tuning fork.

  • Glass of water


 

Introduction:

  • Introduce yourself

  • Wash hands

  • Confirm patient identity - name and DOB.

  • Explain the examination

  • Gain consent

  • Check to see if the patient is in any pain.


 

General inspection.

  • Look at the general appearance and posture of the patient, look for clues around the patient’s bedside.

  • Look for any obvious problems with the patients face/ eyes/ speech


 

1. Olfactory nerve

  • Ask the patient if they have had any changes in smell.

  • If they say yes, then it might be useful to test with something familiar such as coffee or oranges.


 

2. Optic nerve


Pupils/ PERLA


P - Pupils


E - Equal

  • This involves checking if they are symmetrical, of correct shape and the same size.

  • Size → pupils vary in size in different lighting conditions, they are also usually smaller in infants and larger in teens

  • Symmetry → asymmetrical pupils can be due to a palsy such as an oculomotor palsy.


R - Reactive


L - to Light

  • Direct response

→ To assess this shine a light into a patients eye, from the inferior lateral corner and watch to see the pupil constrict.

→ Sluggish contraction is sign of pathology

  • Consensual response

→ When you shine a light into one eye, besides the specified eye contracting, then the other eye should mirror the eye in question.

→ A negative test can be suggestive of: damage to one or both optic nerves, damage to edinger westphal nucleus.


  • Swinging light test

→ Move the torch quickly between the two pupils, pausing over each eye for a few seconds.

→ A normal response is for both pupils to dilate when the light is traveling between the two, but both should contract again no matter which eye the light is shone into.


A - accommodation

  • Ask patient to focus on a far away object such as the top corner of the room.

  • Place your finger or pen torch in front of their nose, about 10-15cm away.

  • Countdown from 3 and ask them to refocus on the end of the object chosen.

  • The pupils should converge and constrict.


Visual acuity

  • To assess visual acuity use the Snellen chart.

  • Ask the patient to stand 6m back from the chart, with one eye covered, read as far down the chart as they can.

  • Record this as the number of meters they are away over the lowest line read.

  • If their eyesight is normal then it should be recorded as 6/6

  • If 1 or 2 letters on a line are incorrect then it should be 6/6 (-1) or (-2), however, if more than 2 on that line are wrong, you have to take the last full line to be the numerator.

  • If the patient is unable to read the top line, reduce the distance to 3m, then to 1m.

  • If this is still unfeasible then test to see if they can count fingers, or sense movement.

  • If movement is undetectable, see if they can detect light.


Colour vision

  • Assess using ishihara charts, this is not commonly done in clinical practice.


Visual fields

  • Ask patient to cover one of their eyes with their hand, mirror this on yourself, don’t forget, their right covered should mean your left is covered.

  • Once you are at an equal height level, extend your arm to all four corners of the visual field, Slowly bring it back towards the centre.

  • Ask the patient to tell you when it comes into their field of vision.

  • Repeat for all 4 quadrants and then repeat again for the other eye.

  • If you are able to see the finger and the patient is not then it would suggest a visual field defect.


Fundoscopy

  • Darken the room to widen the pupils as much as possible.

  • Ask the patient to focus on an object in the distance.

  • Assess for the red light reflex by looking through the ophthalmoscope and ensure the light is directed into the pupil.

  • After this is done, move closer and examine the optic disc and vessels within the eye.

  • Also assess the optic disc, retinal vessels and the macula.


Bind spot

  • This may be tested for, but is often not done unless otherwise suggested.

  • Use a coloured object, preferably red, hold it vertically, an equal distance between you and the patient at eye level.

  • Cover one of your eyes and get the patient to mirror you action.

  • Move the Neurotip outwards, whilst still asking the patient to stay focused on your nose.

  • The neurotip should go out of focus at around 15 degrees.

  • Test all 4 directions around this point to make sure it comes back in afterwards also.


 

3/4/6. Oculomotor, Trochlear and Abducens nerves


Eye movements

  • Hold your finger around 30-50cm away from the patient’s face.

  • Ask the patient to follow your finger with their eyes, but keeping their head still.

  • Move your finger through a H shape to test all the axis of eye movement.

  • Observe any restriction in movement or nystagmus.


 

5. Trigeminal nerve


  • This is an assessment of both light touch and pinprick sensation for the branches of the trigeminal nerve.


  • Ask the patient to close their eyes and say yes if they feel something.

  • Press on both sides of their face in the set positions.

→ Forehead - V1.

→ Cheek - V2

→ Jaw - V3.


Motor

  • Ask the patient to tense their jaw whilst you place your hands wither side of their face to feel the bulk of the masseter muscle.

  • Ask them to do this another time and feel for the bulk of the temporalis muscle.


Reflexes


  • Jaw jerk → very rarely assessed

  1. Ask patient to open their mouth, place finger just below their lower lip and tap it with a tendon hammer.

  2. Normal is for a slight closure of the jaw.


  • Corneal reflex --> rarely assessed

  1. Depress lower eyelid, from the inferior lateral direction.

  2. Ask the patient to look upwards and touch the edge of the cornea with a wisp of cotton wool.

  3. Normal response is to blink.


 

7. Facial nerve


This involves asking the patient to perform specific tasks:

  1. Raise your eyebrows

  2. Close your eyes

  3. Blow out your cheeks

  4. Purse your lips

  5. Close your lips.


  • Throughout all of these, resist the patient's movements and tell them then should try to act against you.

  • Also ask the patient if they had had any: Hearing or taste changes


 

8. Vestibulocochlear nerve


General hearing test

  • To test this, get the patient ot cover up one of their ears.

  • About 1/2m away from the other ear, rub your fingers together.

  • A bristling sound should be heard so long as the room is quiet.

  • If they cannot hear it then move closer until they can.


Rhinne’s test

  • Strike a 512hz tuning fork and then place it behind the ear on the mastoid process.

  • Ask the patient if they are able to hear it and if they can tell you when the noise has stopped.

  • Once it has stopped, move the tuning fork to in front of the auditory meatus, and ask the patient again if they can then hear it.


Normal results - air conduction > bone conduction

Sensorineural deafness - bone bone and air conduction reduced equally.

Conductive deafness - Bone conduction > air conduction.


Weber’s test

  • Tap a 512hz tuning fork and place it either in the centre of the forehead or on the sagittal suture of the skull.

  • Ask the patient if the sound is louder in one ear or equal in both?


Normal = equal in both.

Sensorineural deafness = louder in the unaffected ear.

Conductive deafness - louder in the affected ear.


Vestibular testing

  • Ask patient to march on the spot with their arms out and eyes closed.

  • If they turn to one side or the other then there is likely to be a vestibular lesion.

  • If the patient remains unrotated then it is unlikely.


 

9. Glossopharyngeal nerve


  • Gag reflex is used to test this, however, it is not often done in clinical practice.

  • Ask patient to cough as damage to CN IX or X can give a bovine cough.

  • Swallow - If there is a Glossopharyngeal defect then it may result in a delayed swallowing action.


 

10. Vagus nerve


  • Gag reflex and cough test also cover the vagus nerve.

  • Ask patient to open their mouth and say ‘ahhhh’ as if they were gargling fluid.

  • Note any obvious deviations of the uvula, if it deviated to one side, the lesion is likely to be on the opposite side.


 

11. Accessory nerve


  • Ask their patient to shrug their shoulders and resist you pushing them down. This can be used to test the accessory innervation to the trapezius muscle.

  • Ask the patient to turn their head into your hand and resist you pushing it back. This can be used to assess the accessory innervation of the sternocleidomastoid.


 

12. Hypoglossal nerve


  • Ask patient to stick out their tongue.

  • Inspect tongue for any resting fasciculations.

  • Note if there is any deviation on tongue protrusion.

  • If there is then a lesion would cause deviation towards the side it is on for this test.


 

To complete the examination

  • Full sensory and motor neurological exam of upper and lower limbs

  • Cerebellar examination

  • CT/MRI head

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