Lab 6b- Test for cranial nerve function

Question 1

what is the purpose of vestibulo-ocular reflex

Answer 1

stabilise images on retina during head movements

Question 2

what are the components of the vestibular apparatus and what do they detect

Answer 2

Semi-circular canals
- detects angular acceleration in 3 dimensions

Otolith organs (utricle and saccule)
- detects linear acceleration

Question 3

which component of the vestibular apparatus is involved in eliciting the vestibulo-ocular reflex

Answer 3

Semi-circular canals

Question 4

what results in disturbance of the vestibulo-ocular relfex

Answer 4

nystagmus

Question 5

what 2 methods are used to elicit the vestibulo-ocular reflex

Answer 5

Barany chair

Caloric Testing

Question 6

what type of nystagmus are produced in barany chair testing

Answer 6

horizontal
rotatory
vertical

Question 7

describe caloric stimulation

Answer 7

injection of water into the external auditory meatus leads to heat transfer and sets up convection currents in the horizontal semi-circular canal. Fluid movement stimulates hair cells -> stimulating vestibulo-ocular reflex

Question 8

what signs are seen in caloric stimulation to show that vestibulo-ocular reflex has been achieved

Answer 8

dizziness

horizontal nystagmus

Question 9

what is the relevance of caloric stimulation in a clinical setting

Answer 9

Can be used to test brainstem integrity in an unconscious patient by eliciting the vestibul-ocular reflex

Question 10

what other tests are used to test brainstem integrity

Answer 10

Direct light reflex

Gag reflex

Question 11

what leads to physiological activation of semi-circular canals

Answer 11

• Normal ‘sharp’ and ‘short’ head movements lead to transient hair cell activation
• Powerful stimulation e.g. fair ground rides: elicits motion sickness, dizziness and nystagmus

Question 12

which conditions cause vestibular dysfunction

Answer 12

Labrynthitis
Vesitbular Neuritis
meniere disease

Question 13

excessive stimulation of semicircular canal leads to what

Answer 13

disorientation and may cause disability

Question 14

what is the cranial nerve test for olfactory I

Answer 14

Function – smell

• Smell samples of familiar odours with one nostril with the other closed one at a time
• Ensure samples are not irritant since even if olfactory function is lost irritants can still be detected by nociception’s in nasal mucosa

Question 15

what is the cranial nerve test for optic II

Answer 15

Function- Vision

1) Visual acuity
- one eye covered and printed material (book) is read from 18 inches away. repeat this for the other eye

2) Visual Fields
- sit opposite subject (1 metre away)
- ask subject to cover their left eye with left hand. examiner covers right eye with right hand.
- compare your visual fields to the subjects
- ask the subject to look into your eye and see your fingertip wiggling. test each of the 4 quadrants

Question 16

what is the cranial nerve test for occulomotor III, Trochlear IV, Abducens VI

Answer 16

Function – Extraocular eye muscles
- Observe if normal position is distorted e.g.
deviation of an eye or for nystagmus
- Ask patient to keep head straight then draw a H
using your finger and ask patient to follow your
finger

Question 17

what is occulomotor palsy

Answer 17

• Eye position: downward and outward gaze
  (SO4 and LR6 function retained)
• Dilated pupil and fixed pupil
• Ptosis

SO4- superior oblique muscle controlled by CN IV
LR6- lateral rectus muscle controlled by CN VI

Question 18

what is trochlear palsy

Answer 18

• Eye position appears normal but rotated outwards

- Compensatory head position tilted to the other side

Question 19

what is abducens palsy

Answer 19

• Eye position is adducted

- may show compensatory head position- tilted to the lesioned side

Question 20

what are the divisions of the trigeminal nerve

Answer 20

1. Opthalmic nerve -> supra orbital nerve
2. Maxillary nerve -> Infra orbital nerve
3. Mandibular nerve -> mental nerve

Question 21

what is the sensory division of the trigeminal nerve branches and what does it innervate

Answer 21

Opthalmic- forehead, eye and upper nose
Maxillary- Temporal region (cheekbone, lower nose and upepr lip
Mandibular- lower lip and jaw

sensory innervation to face, teeth, tongue, oral and nasal cavity, sinuses

Question 22

how to test the sensory function of the trigeminal nerve

Answer 22

• Lightly touch the areas of the 3 division of trigeminal nerve with cotton wool or a blunt object with subject eyes closed
• Repeat on other side

Question 23

what is the motor innervation of the trigeminal nerve how do you test it

Answer 23

Motor innervation: muscles of mastication (mandibular nerve)

• Clench jaw and palpate superior and inferior to zygomatic arch – masseter and temporalis muscle
• Ask patient to open mouth and note deviation, if the jaw deviates to R then Lat. Pterygoid on L is weak and vice versa
• Ask patient to move jaw side to side. Jaw jerk reflex – place finger on subject chin
  and hit with hammer

Question 24

where is the trigeminal ganglion localised and what is its functions

Answer 24

Trigeminal ganglion: made of 3 sensory nuclei (mesencephalic, principal sensory and spinal)
Location- occupies a cavity (meckels’ cave in dura mater)
Function- Receives sensory input and sends this info to motor nuclei of trigeminal nerve for control of mastication muscles

Question 25

what is the cranial nerve test for facial nerve

Answer 25

Test to see the motor control of the muscles of facial expression. Subject is asked to raise eyebrows, frown, smile and puff out cheeks

Question 26

what is the cranial nerve test for vestibulocochlear nerve

Answer 26

1) whisper voice test Stand a couple steps behind subjects right ear and whisper several numbers to see if they can repeat them. Hold a ticking watch from a distance and slowly bring it towards ear and have the subject tell you when they can hear it . Repeat the test on the left side 2) Rinnes and webers test (tuning fork) Rinnes test- place a tuning fork on subjects mastoid process and then next to their ear. ask which sound is louder, normal patient will find second position louder Webers test- place tuning fork in centre of patients forhead and ask if it is louder in either ear.

Question 27

what is the cranial nerve test for glossopharyngeal and vagus nerve

Answer 27

- Speech: ask patient to speak and watch for difficulties (dysphonia) or huskiness in voice – vagus - Swallowing: ask patient to swallow and watch for difficulties swallowing (dysphagia) – vagus and glossopharyngeal - Ask patient to open mouth and say ‘AAAA’ observe for deviation of uvula (deviates away from side of lesion) – vagus - Gag reflex – touch the pharynx with tongue blade and should evoke a gag reflex – glossopharyngeal nerve and vagus nerve

Question 28

which nerve innervates stapedius muscle of ear

Answer 28

facial nerve

Question 29

what is the cranial nerve test for accessory spinal nerve and whats muscles does it innervate

Answer 29

innervation to trapezius and sternocleidomastoid place arms firmly on shoulders of subject, they should be able to raise their shoulders against resitance

Question 30

what is the cranial nerve test for hypoglossal nerve

Answer 30

o Instruct patient to stick tongue out o Tip should deviate to weak side if lesion o Check if movements in other directions can be made with ease

Question 31

Which nerve provides sensory innervation for touch and temperature sensation to the nasal cavity?

Answer 31

Trigeminal nerve- opthalmic and maxillary branches

Question 32

Which structures in the eye have parasympathetic innervation

Answer 32

iris sphincter muscle/ Sphincter pupillae, ciliary muscle.

Question 33

Which cranial nerves are involved in the corneal reflex?

Answer 33

Trigeminal nerve, ophthalmic division – sensory afferent | Facial nerve - efferent (orbicularis oculi).

Question 34

Which large gland is innervated by the glossopharyngeal nerve

Answer 34

Parotid gland (via the lesser petrosal nerve).

Question 35

Which nerves provide taste innervation to the tongue?

Answer 35

Anterior 2/3 is innervated by the chorda tympani from the facial nerve Posterior 1/3 is innervated by the glossopharyngeal nerve

Question 36

Which cranial nerves are involved in the gag reflex

Answer 36

Afferent glossopharyngeal nerve (sensation posterior pharyngeal wall) Efferent vagus nerve (elevation soft palate, constriction pharynx).

Question 37

A patient presents with severe, shooting pain on the left side of her jaw, triggered by cleaning her teeth, chewing, cold wind or even just touching the left jaw. GP recognises this as neuralgia- hyperexcitbaility of a CN. which cranial nerve is affected

Answer 37

Trigeminal nerve – in this case mandibular division. Condition is called Trigeminal neuralgia. It is rare for TG neuralgia to involve ophthalmic division. The cause is not fully understood. It can occur as a result of pressure on the TG nerve root from an aberrant loop of the superior cerebellar artery. Also can result from compression from a tumour; patients with multiple sclerosis often have TG neuralgia although again the exact reason is not understood.

Question 38

Patient presents with their soft palate elevated, uvula deviated towards intact side- points away from side of lesison) which main CN affected and which other CN can be affected

Answer 38

Main CN- vagus nerve | other CN- Glossopharyngeal (uvula deviated towards side of lesion)

Question 39

A patient comes with with weakness on the left side of her face. She cannot completely close her left eye, raise her left eyebrow, or smile on the left side. the patient has shingles. which CN has been affected

Answer 39

facial nerve

Question 40

Shingles is caused by reactivation of the Varicella-Zoster virus, which remains dormant in nerve-cell ganglia. In which ganglion has the virus reactivated in this example?

Answer 40

Geniculate ganglion The shingles rash is seen on the pinna, the facial nerve is closely associated with the inner ear. This particular form of shingles is known as “Ramsay Hunt syndrome”. After chicken pox, the varicella zoster virus remains latent. Geniculate ganglion is within the temporal bone and contains cell bodies from taste fibres

Question 41

A patient is found to have a tumour at the jugular foramen. which CN are most liekly to be affected What symptoms is the patient likely to have presented with, in relation to the cranial nerve lesions?

Answer 41

CN IX, X and XI – these nerves pass through the jugular foramen loss of taste to posterior 1/3 of tongue (CN IX), dysphonia, hoarseness, dysphagia (CN X) , sternocleidomastoid and trapezius paralysis (CN XI) Anything that compresses the jugular foramen can cause this syndrome. The commonest cause is a paraganglioma.

Question 42

A woman presents with a 2-day history of imbalance, nausea and vomiting. She noticed her hearing had deteriorated in her right ear when using the telephone. She reports having an upper respiratory infection the week previously. On examination her GCS is 15. She is apyrexial and cardiovascular and respiratory examinations are normal. Tuning fork testing reveals sensorineural hearing loss in the right ear. On examination of eye movements, the GP notices rapid side-to-side movements of the eye. There are no other abnormal neurological findings. What is the medical term that describes the abnormal eye movements? and what is the liekly diagnosis

Answer 42

nystagmus viral labrynthitis

Question 43

A patient presents to the emergency department 24 hours after falling off a horse whilst out riding. next day she noticed she could not smell anything and had a watery discharge from her nose. what clinical sign is seen in this condition (severe red brusining around eyes) What is the discharge coming from her nose What is the most likely underlying injury

Answer 43

panda eyes CSF fracture of the cribriform plate (part of ethmoid bone), with associated tearing of the dura mater & arachnoid mater.

Question 44

what does the clinical sign- panda eyes suggest

Answer 44

Base of skull fracture

Question 45

describe the innervation of the occulomotor/ external eye muscles that control eye movement

Answer 45

``` 6 eye muscles. 4 controlled by CN II occulomotor nerve: - Medial Rectus - Inferior Rectus - Superior Rectus - Inferior Oblique ``` 2 controlled by CN IV Trochlear and CN VI Abducens - SO4- superior oblique controlled by CN IV Trochlear - LR6- lateral rectus CN VI Abducens