Cranial Nerves and Examination Flashcards
Dental Relevance of neurological disorders
- Neurological disorders may present as dental problems
- CN examination may help you distinguish between the two
- Pain of non-dental origin may be interpreted as dental pain, resulting in unnecessary extraction of sound teeth
- Pathology associated with these nerves present in the head and neck. Dentist are in perfect position to detect neuropathies at an early stage and ensure the patient has prompt onward referral and follow up
Taking a history of a neurological disorder
-Ability to locate the lesion anatomically and understand the underlying pathological process
-Allow patient to describe in their own time and words without putting words in their mouth
-Right-handed patient indicates left hemisphere dominant and vice versa
-Note details of the primary and main symptom or sign:
When did it happen
Description of what happened
Time taken for deficit to develop
Recurrence or persistence
Provoking or relieving factors
Time for development of symptoms to peak and improve
Associated clinical symptoms and signs
Doing an examination of a neurological disorder
- Cranial Nerves
- Tone
- Power
- Coordination
- Reflexes
- Sensation
-Level of consciousness:
Alert?
Confused?
Orientated in time and space?
-Examine the memory:
Recall their name and address and repeat after 5 mins
Concentration: serial subtraction of 7 from 100
General knowledge: current pm
-Look at speech:
Dysarthria (disorder of articulation)?
Dysphasia (language disorder)?
-Remember to gain consent and wear gloves prior to doing any examination
CN I Anatomy, Description, Examination and Defects
Anatomy and Description
- Sense of smell
- Purely sensory
- Peripheral olfactory process sit in the olfactory mucosa at the top of the nasal cavity
- Sense of smell detected by olfactory receptors located within the nasal epithelium, which then penetrates small foramina of the cribiform plate of the ethmoid and enters the cranial cavity
Examination
- Rarely tested
- Ask them about their sense of smell
- Any recent changes
- Test each nostril asking them to identify certain smells
- Often coffee
Defects
- Lesions may result in anosmia
- Temporary or permanent
- Temporary would include infection/local disorder of the nose
- Permanent would include injury, tumours, neurodegenerative disorders
CN II Anatomy, Description, Examination and Defect
Anatomy and Description
- Transmission of sensory information from the retina to the primary visual cortex of the brain
- Purely sensory
- Optic chiasm
Examination
-4 main tests: Visual acuity, visual fields, pupillary reflexes and fundoscopy
-Visual acuity:
Tested through a Snellen chart where the patient is sat 6 metres away
-Visual Fields:
Test through confrontation
Sit opposite patient and ask them to fixate on your nose
Get patient to count fingers at edge of each field in each eye in all 4 quadrants
Monocular blindness: One eye is blind
Bitemporal hemianopia: Blindness in the outer half of each eye
Homonymous hemianopia: Blindness in the right/left half of each eye
-Pupillary reflex:
Light reflex and accommodation
Step 1: Using a pen torch in a dark room and shine it into one eye
Step 2: Observe direct response (response to light in that eye) and consensual response (response to light in the other eye)
Step 3: Repeat in the other eye
Note: Afferent pathway through optic nerve, efferent pathway through oculomotor nerve
If you shine a light into the left eye and there is a left optic nerve lesion:
Loss of left direct response (left pupil will not constrict)
Loss of right consensual response
If you shine a light into the right eye and there is a left optic nerve lesion:
Maintenance of left consensual response
Maintenance of right direct response
Vice versa for right optic nerve lesion
If you shine a light into the left eye and there is left oculomotor lesion:
Loss of left direct response
Maintenance of right consensual response
If you shine a light into the right eye and there is a left oculomotor lesion:
Maintenance of right direct response
Loss of left consensual response
Vice versa for right oculomotor lesion
-Fundoscopy takes practice; leave it to the opticians
Defects -Causes of optic nerve defects include: MS Compression Tumour- pituitary adenoma causing tunnel vision Ischaemia Retinal artery compression
CN III, IV and VI anatomy, description, examination and defects
Anatomy and Description
- All supply extra ocular muscles
- All purely motor
- CNIII supplies medial rectus, superior rectus, inferior rectus, inferior oblique, sphincter pupillae and levator palpabrae superioris
- CNIV supplies superior oblique
- CNVI supplies lateral rectus
Clinical Examination
-Trochlear nerve (CNIV) palsy would show patient looking up and in
Inability to turn the eye down and in???
-Abducens nerve palsy would show a patient looking medially
Inability to look laterally
-Oculomotor palsy would show ptosis (drooping), fixation of the eye downwards and outwards and inability to constrict that eye (as described above in Optic Nerve examination)
Defects
-Causes of CNIII lesions include:
Oculomotor compression by intracranial tumour, aneurysm of the posterior communicating artery, trauma after road traffic accidents
Oculomotor paresis caused by: sarcoidosis, diabetes, infarction due to ischaemia, demyelination
-Causes of CNIV lesions include:
Trauma, especially closed head injury
Uncommonly, MS, aneurysms and tumours may also cause lesions
-Causes of CNVI lesions include: Nasopharyngeal tumour Intracranial tumour Diabetes Infections Aneurysm
CN V Anatomy, description, examination and defects
Anatomy and Description
- Sensory and motor components
- Sensory components divided in to V1, V2 and V3; ophthalmic, maxillary and mandibular zones respectively
- Supply motor components to the muscles of mastication (temporalis, masseter, medial pterygoid and lateral pterygoid), tensor tympani (located in the middle ear), tensor veli palatini (tenses the soft palate), mylohyoid (floor of oral cavity) and anterior belly of digastric.
Examination
- Sensory component divided into V1, V2 and V3
- Tested through light touch using a cotton wool
- Get patient to close their eyes and lightly touch cotton wool against an area supplied by each of the branches of CNV
- Get patient to confirm when they feel a sensation
- Corneal reflex can also be tested to test sensory component
- Blink elicited by a gently touch of the cornea with a wisp of corneal cotton wool
- Touch the margin of the cornea from the side and approach from behind so patient does not see it approaching
- Motor component can be tested by getting patient to clench their teeth
- Palpate masseter and temporalis muscles
- Muscles will be wasted on the side of a lower motor neurone lesion
- Jaw opening and jaw jerk can also be tested
- Jaw will deviate to the side of a lower motor neuron lesion when the patient opens the jaw against resistance
- Ask patient to open and relax their mouth so it hangs open. Place your thumb on the patient’s chin and strike your thumb gently with a tendon hammer. The reflex is very variable but may be brisk in upper motor neurone lesion. This is the jaw jerk reflex
Defects -UMN lesion causes may include: Ischaemia Tumour MS -LMN lesion causes may include: Acoustic neuroma Cavernous sinus lesion
CNVII Anatomy, description, examination and defects
Anatomy and Description
-Sensory and Motor
-4 main functions:
Motor: Muscles of facial expression, posterior belly of digastric, stylohyoid and stapedius muscle
General Sensory: Small area around the concha of the auricle
Special Sensory: Special taste sensation to the anterior 2/3rd of the tongue
Parasympathetic: Various glands including the submandibular salivary glands, sublingual salivary glands, nasal mucous glands, palatine mucous glands, pharyngeal mucous glands and lacyrimal glands
-Branches of the facial motor nerve include the temporal, zygomatic, buccal, marginal mandibular and cervical (Two Zebras Bit My Chin)
Examination
-Ask patient about their sense of taste and hearing. Has it has changed?
- Ask patient to repeat a set of standardised facial movements
- Grin, show their teeth, screw up their eyes and wrinkle their forehead
- A LMN lesion involves unilateral weakness of the whole of the one side of the face
- A UMN lesion involves unilateral weakness of the lower face only with the forehead spared
Defects
-LMN lesions can be caused by:
Parotid tumour
-UMN lesions can be caused by:
CVA (Stroke)
- Intracranial lesions result in UMN lesions
- Extracranial lesions result in LMN lesions
- Bell’s palsy is a lower motor neurone palsy of unknown aetiology
- Patient unable to close their eyes completely
- No forehead creases and unable to grimace
- Diminished or distorted taste
- Drooling
- MRI, CT, CXR, FBC required
- Eye patch to prevent corneal drying and scarring
- Patient becomes depressed and need psychological support
- Corticosteroids required per day and needed to reduce swelling and vasculitis
- Surgery only considered in patients who have problems eating and speaking 12 months after the initial event
CN VIII anatomy, definition, examination and defects
Anatomy and Definition
- Purely sensory
- Transmits sound and equilibrium information from the inner ear to the brain
Examination
-Test acuity of hearing (use a watch and test if it can be heard)
-Perform Rinne’s and Weber’s tests as deafness may be conductive or neural
Defects
- Lesions can result in deafness, tinnitus, vertigo and vomiting
- Deafness on the ipsilateral side if lesion of cochlear division
- Lesion of vestibular division leads to nystagmus and vertigo
CN IX anatomy, definition, examination and defects
Anatomy and Definition
- Branchial motor (special visceral efferent) to the stylopharyngeus muscle
- Visceral motor (general visceral efferent) providing parasympathetic innervation of the parotid gland via the otic ganglion
- Visceral sensory (general visceral afferent)- carries visceral sensory information from the carotid sinus and carotid body
- General sensory (general somatic afferent)- provides general sensory information from inner surface of the tympanic membrane, upper pharynx and posterior 1/3rd of the tongue
- Visceral afferent (special visceral afferent)- provides taste sensation from posterior 1/3rd of the tongue
Examination
-Gag Reflex: Touch the tonsillar fossa- there should be elevation of the midline of the palate
Defects
-Nasopharyngeal tumours
CN X anatomy, defintion, examination and defects
Anatomy and Definition
- Principally motor to pharynx, larynx and soft palate (cricothyroid, levator veli palatini, palatoglossus, palatopharyngeus, superior/middle/inferior pharyngeal constrictors, muscles of the larynx)
- Visceral motor branch supplies parasympathetic innervation of the smooth muscle and salivary glands, the pharynx, the larynx and the viscera of the abdomen and the thorax
- General sensory branch supplies general sensory information from the skin of the preauricular area, the external auditory meatus, parts of the external surface of the tympanic membrane and the pharynx
- Visceral sensory branch supplies sensory information from the larynx, oesophagus, trachea, abdominal and thoracic viscera. Also provides stretch receptors of the aortic arch and chemoreceptors of the aortic body
- Special sensory branch is a minor branch which supplies taste sensation from the epiglottic region
Examination
- Get patient to say ‘ahhhhh’ and visualise the uvula and soft palate
- If there is a deficit present, then the soft palate will lie lower on the side of the lesion
- Uvula will be pulled away from the side of the lesion, so will point towards the normal side
- Gag reflex can also be checked
- Can patient swallow properly?
Defects
- Isolated lesions are unusual
- Sometimes during thyroid surgery or tumour, the recurrent laryngeal branch may be damaged, resulting in hoarseness of the voice
CNXI anatomy, defintion, examination and defects
Anatomy and Definition
- Purely motor
- Supplies the sternocleidomastoid and trapezius muscles
- Cranial component and a spinal component from the cervical spinal cord
Examination
- Shrug shoulder against resistance
- Turn head against resistance
Defects
-Lesions of the spinal accessory nerve result in paralysis of the trapezius and sternocleidomastoid muscles
CN XII anatomy, definition, defects and examination
Anatomy and Definition
- Purely motor
- Motor control of the extrinsic muscles of the tongue (genioglossus, styloglossus and hyoglossus) and all the intrinsic muscles of the tongue
- Basically all the tongue muscles except the palatoglossus muscle which is supplies by CNX
Examination
- Get patient to stick their tongue out at you
- Should be horizontal
Defect
-If there is a lesion present, the tongue will deviate to the side of the lesion
