Cranial Nerve Examination Explained - Clinical Skills Deep Dive - Medical School Revision - Dr Gill

hello and welcome to another episode in trying to understand the clinical examinations with myself dr. James Gill so we're going to be having a look at the cranial nerve examination hopefully by now you've already seen the video that we've performed of myself and doing the cranial nerve examination but as I'm sure that as people have noticed there is no additional dialogue over the top of that video the main reason being so that it can be used for teaching in multiple different levels whether or not you're a first-year medical student or whether or not you are finally a medical student in the previous understanding clinical examinations podcast I did highlight that I'm not a fan of the neurological examination or to be specific I've got no problem with the examination but it's some of the very very high level neurology knowledge that I always find a little bit uncomfortable thankfully the cranial nerve exam is a much easier mental challenge for me to get my head round and in terms of physically performing the 12 different cranial nerve examinations I've actually kind of enjoyed those yes I've revised them and learn them by rote but nevertheless I still think it's quite an elegant examination so with that in mind we're going to turn over to McLeod clinical examination I'm going to go through the chapter on the cranial nerve examination as before people have asked for a little bit more interjection from myself so as well as reading through our CVS chapters I will give my own opinion and any particular features that I feel irrelevant to pay attention to during the examination and perhaps more hopefully I'll throw in the odd clinical pearl that I've found beneficial when actually interacting with the patient I'm trying to perform the examination okay so with that here are the cranial nerves the twelve pairs of cranial nerves with the exception of cranial nerve one till a factory nerve all arise from the brainstem cranial nerves two three four and six relates to the eye while eight relates to hearing and balance okay as far as introduction was going terrible what about the other cranial nerves okay let's go over the summary box instead because I think that's probably a good introduction or a better one than they've got there so cranial nerve one the olfactory nerve this is your sense of smell and there's an innovation to each nostril abnormalities that might be seen will be an ma smear or Paris Mia so that being when a patient can't smell all they're smelling things that other people can't a good example of this might be a patient who sustained a head injury and when seen in the A&E department cannot smell anymore the cranial nerve one the olfactory nerve actually goes through the base of the skull at something called the cribriform plate and that allows smell to go up into your nostrils tickle the nerves and give us the sensation of smell however because of these little finger-like protrusions --is that go through the cribriform plate they're very very delicate and if as an example you get a severe blow to the head which causes the brain to jerk within the skull those very delicate fibers can be ripped from the cribriform plate or simply severed resulting in the loss of smell similarly the peril smear if a patient has a brain tumor which is affecting the cranial nerve 1 then they may get abnormal senses of smell cranial nerve - this is dealing with visual acuity your visual fields will help control your pupil size and shape allow your eyes to respond to light reflex and to ensure a thorough examination must also be examined with direct fan Tasca p abnormalities that you can see may be partial sight or blindness a scotoma indicating a partial loss of vision spot in an otherwise normal field that's something as have received in terms of feedback from the previous video where I'm using clinical terminology I'm going to try and give the actual definition or use of it because certainly when I was learning there's nothing worse than having to interrupt your learning experience to you're scurrying off to check the dictionary for what hemianopia means in this particular case how many opiate means half site or hemming or Opia site but specifically that would be half the vision has been lost from a single eye not the one eye isn't working so for example if they close their eye the patient might find that the lateral half of their vision has disappeared depending on what the underlying pathology was another feature that we may see with a cranial nerve - lesion is Anna scoria if you want a really good clinical example of that than a device you to have a look at some of the photographs of David Bowie not only does he have heterochromia so different colored eyes which is a genetic family trait for himself but also anis Coria so he has one pupil which is a different size to the other the reason for that being he had a childhood fight over a girl about the age of 15 and his friend punched him in the eye scratching the eye itself resulting in damage to the muscle fibers that control his pupil this dilation of the pupil also has its own medical terminology that being mydriasis seriously doctors have got a word for everything and if they haven't they're probably just going to make it up other problems with cranial nerve - might also cause issues with the optic disk and retinal changes cranial nerve three or the oculomotor nerve is responsible for light and accommodation reflex that being the pupil changing size to help you focus on something which is near and far away and if there's any problem there then you're going to have a loss of light reflex to the eye so I'm performing the cranial nerve examination you should shine a light in the patient's eye whereupon you would expect to see their pupils constrict if cranial nerve three was functioning correctly hold on doesn't that clash with the fact that we've just said that cranial nerve two could have issues with Anna scoria we will go into this in more detail in a moment but suffice to say that cranial nerve two is saying I have this signal and cranial nerve three is acting on that signal which is why they can both have problems with the pupils however cranial nerve three also has additional functions along with the cranial nerve for that being the trochlear and cranial nerve 6 the abducens they're involved in I position and movements of the eye where a patient who may have a difficulty here may have strabismus or a squint diplopia so double vision or nystagmus which is the rhythmic beating of the eye at the very extremes of gaze so if for example you two keep your head still and look all the way to the left as you strain your eyes to the left your eye should remain static somebody with nystagmus there I would bounce a little bit side to side at that very extreme cranial nerve 5 or the trigeminal nerve is responsible for facial sensation the corneal reflex basically blinking if something touches your eye the muscles of mastication eye those who chew it and a Georgia reflex in terms of abnormalities might be seen you may get simple impairment so difficulty feeling with one area of the face along with weaknesses in chewing if there was a lesion affecting the trigeminal nerve whilst the trigeminal nerve deals with sensation of the face the slightly confusingly named facial nerve or cranial nerve seven deals with the muscles of expression so smiling grimacing etc also provides a small sensory component giving taste over the anterior 2/3 of the tongue if we had issues the cranial nerve seven we may see facial weakness or problems with loss of taste classically a stroke is seen to present with a facial nerve weakness similarly a Bell's palsy a lower motor neuron lesion affecting the facial nerve will again affect expression that this expression was slightly different and crucially so compared to that which is seen with a stroke it is arguable the cranial nerve eight is one of the most important cranial nerves the vestibular cochlear nerve is vital for hearing but also balance if there are problems with the cranial nerve eight then you may have hearing or straightforward deafness we may have a nystagmus and most troubling for patients problems with the vestibular cochlear nerve may cause vertigo cranial nerve nine or the glossopharyngeal nerve provides pharyngeal sensation and is not routinely tested cranial nerve 10 or the vagus nerve is involved with palatine movements so the ability to phone 8 and the movement of the soft palate if this is tested it's using a pen taunt and simply getting the patient to say ah whilst looking at the top of their mouth the pronouncement cranial nerve cranial nerve 11 or the spinal accessory nerve is required for movement of the trapezius and the stern of mastoid muscles if there is a lesion affecting this nerve we will see weakness in the scapula and neck movements finally the hypoglossal or twelfth nerve this is involved in hunger parents are you sticking your tongue out and also movements of the tongue problems with cranial nerve 12 or the hypoglossal nerve may cause dysarthria where a person has problems making the sounds of words they may also have issues with chewing and/or swallowing as the tongue is exceptionally important in the act of eating and mobilizing a bolus of food around the mouth and initiating the swallowing process so there's a brief summary of the overview of the cranial nerves and how these cranial nerves interact and the functions that they provide for the head and neck in the next video we're going to be looking at the specifics of the examinations of the cranial nerves on what abnormalities we might find here I've changed things around in this video and tried to split the sections into different videos rather than loading everything into one session so I'd be very grateful for your feedback as to whether or not you prefer the longer video where everything is packed into one session or prefer the idea of splitting things into an overview and then the focus on the examination afterwards okay I hope you have a good evening and if I could please ask you kindly if you found this useful please give it a like below and certainly subscribe and then you'll get a heads up when the next video is published hopefully in the week okay thanks so much see you later bye you