Olfactory, Optic, Oculomotor,Trochlear, Abducens, Trigeminal, Facial, Vestibulocochlear, Glossopharyngeal, Vagus, Accessory, and Hypoglossal. In this post we have discussed all the cranial nerve examinations :
- How to examine the Olfactory nerve.
- How to examine the Optic nerve.
- How to examine the Oculomotor, Trochlear, and Abducens nerve.
- How to examine the Trigeminal nerve.
- How to examine the Facial nerve.
- How to examine the Vestibulocochlear nerve.
- How to examine the Glossopharyngeal nerve.
- How to examine the Vagus nerve.
- How to examine the Accessory nerve.
- How to examine the Hypoglossal nerve.
1. How to examine Olfactory nerve(1st) :
This test helps in smell sensation. Small bottles containing fragments or pungent smelling substances such as lemon, dove, or asofoetida are placed in each nostril independently to evaluate this.
1. Hyposmia :
Hyposmia refers to a loss of smell or the inability to detect odours through the nose. The inability to smell anything is known as annosmia.
ENT illnesses, Parkinson’s disease, and Alzheimer’s disease are the most common causes of this.
2. Hypogeusia/Ageusia :
- Hypogeusi is a condition in which one’s ability to taste things is impaired (to taste sweet, sour, bitter, or salty substances). Ageusia is a condition in which a person is unable to recognise flavours.
- Anosmia could be caused by either of these two factors.
3. Other tests :
Although objective’scratch and sniff’ tests are available, bedside examination of scent is of limited clinical utility. One example is University of Pennsylvania smell identification test (UPSIT)
UPSIT :
- The UPSIT is a test that determines a person’s capacity to detect scents over their threshold. The exam is normally given in a waiting area and takes only a few minutes to complete.
- The test consists of four 10-page booklets with a total of 40 questions. There is a distinctive scratch and sniff strip embedded with a microencapsulated odorant on each page. On each page, there is also a four-choice multiple-choice question.
- A pencil is used to discharge the smells. The patient smells the level and detects the odour from the four options after each aroma is emitted. On the back of the test booklet is an answer column, and the test is scored out of 40 items.
2. How to examine Optic nerve(2nd) :
I. Visual acuity test :
The snellen chart is used to determine this, with 6/6 being normal vision and the youngster achieving it within 6 years.
- At birth, the visual acuity is 6/45, and at one year, it is 6/45.
- If the child is unable to see, a finger count is performed at 1 metre, which is 6/60 at the top of the chart -> If the child is unable to see, a finger count is performed at 1 metre, which is 6/60 at the top of the chart -> If the child is unable to see, a finger count is performed at 1 metre, which
- If the youngster does not observe the finger count, the child’s perception of hand movement is tested.
II. Field of vision test :
Monocular and binocular visual fields are both tested.
A. Binocular vision field :
The examiner sits face to face with the child and holds his or her hands about one metre apart, asking the child if he or she can see both hands.
Moving the index finger down to the right and left, superior and inferior quadrants, accomplishes the same result.
B. Monocular vision field :
A pin with a bright red pinhead is used to evaluate this vision. The field’s margins are locations where the red colour fades or disappears. The identical method is then repeated in each quadrant.
III. Colour vision test :
Ishihara plates on the bedside reveal this. In the exam, multicolor red toys can be used to accomplish this. It’s possible that the child is older than three years.
IV. Squint test :
Corneal light reflex and cover tests can be used to determine this. By illuminating a light in front of the face, the corneal light reflex can be seen. Each cornea should have the same position of the light reflex. Then, using a doll or a toy on which the youngster focuses his gaze, perform a cover and uncover test.
V. Pupillary light reflexes test :
Corneal light reflex and cover tests can be used to determine this. By illuminating a light in front of the face, the corneal light reflex can be seen. Each cornea should have the same position of the light reflex. Then, using a doll or a toy on which the youngster focuses his gaze, perform a cover and uncover test.
VI. Others test :
- Fundoscopy is done to check any abnormalities.
- Mild optic neuropathy might cause loss of redness in one eye.
- A lack of red response indicates corneal opacity, lens cataract, and vitreous opacity.
3. How to examine Oculomotor(3rd), Trcochlear(4th), Abducens(6th) nerve :
To examine the function of these three nerves, we can simply rely on the extra ocular muscles functions.
ALL3, LR6 and SO4
- ALL-3 : It simply suggests that all the extra ocular muscles other that superior oblique and Lateral rectus is supplied by the 3rd cranial nerve.
- LR-6 : This signifies that the lateral rectus is supplied by the 6th cranial nerve.
- SO-4 : Superior oblique muscle is supplied by the 4th cranial nerve.
Now we can check any of the above nerve palsy by various test.
- 3rd nerve palsy – Ptosis, dilated pupils, and external strabismus are the only side effects. In order to do a 3rd nerve test, we must look for adduction paresis (medial rectus), elevation paresis (inferior rectus), ptosis (owing to levator palpabrae superioris paresis), and dilated fixed pupil with loss of accommodation.
- 4th nerve palsy – This will result in diplopia, head tilting to the opposite side of the lesion, and impaired downward eye ball movement.
- 6th nerve palsy – Squinting results, lateral gaze results in horizontal diplopia, and lateral gaze is impossible.
Other than this tests, there are some specific tests, and they are described below :
- Argyll Robertson pupil – The accommodation reflex is present but the pupillary light reflex is lacking, which is common in midbrain injuries.
- Dolls eye manuever –The eyeball moves in this case in the opposite direction of the head movement seen in comatose patients. It shows a supranuclear lesion with a healthy brainstem and third nerve.
- Hippus – This is rhythmic pupillary dilatation and constriction, which can be seen in certain healthy children, retrobulbar optic neurirtis, Ethanmbutal poisoning, and encephalitis.
- Marcus gunn pupil – The pupil dilates in the damaged eye and constricts in the unaffected eye, which is most common in optic nerve lesions.
- Horner’s syndrome – Occurrence of pupillary constriction, ptosis, and anhidrosis.
Proptosis, Ptosis and Cataract pathologies :
| Causes of proptosis | Causes of ptosis | Causes of cataract |
| 1. Optic glioma 2. Neurofibromatosis 3. Neuroblastoma 4. Chloroma 5. Retro-orbital haemorrhage 5. Thyrotoxicosis | 1. Congenital causes 2. Horner’s syndrome 3. Myasthenia gravis | 1. Down syndrome 2. Diabetes mellitus 3. Steroid 4. TORCHES – virus group 5. Senile/age related |
4. How to examine Trigeminal nerve(5th) :
This nerve gives sensory input to the face, mouth, and a portion of the dura mater, as well as motor input to the masticatory muscles.
- Cotton wool test – This test evaluates test feeling. While the patient’s eyes are closed, cotton wool points are touched. By answering ‘yes,’ the test is confirmed.
- Jaw jerk test – The patient is asked to open his or her mouth, and the examiner places his or her fingertip in the midline between the lower lip and the chin, attempting to percuss the forefinger with a tendon hammer. Then any jaw closure due to reflux is recorded.
- Corneal reflex – This is checked by rubbing a wisp of damp cotton wool across the cornea and looking for direct and voluntary blinking.
- Muscles of mastication – Looking for wasting and feeling the mastication muscles can be used to assess motor function. The examiner places his hand beneath the patient’s jaw to give resistance while asking them to open it. The examiner then attempts to note any deviations. Finally, when the patient clenches his or her jaw, he or she tries to feel the contraction of the masseter muscles.
- Trigeminal nerve is marked intact, when the child ables to bite a spatula or food.
5. How to examine Facial nerve(7th) :
The facial muscles, lacrimal glands, and salivary glands are all supplied by this nerve. It also conveys taste sensations from the anterior two-thirds of the tongue.
We will check for :
- Facial movements – While the child cries, the facial motions are monitored, and the asymmetry is verified while the youngster grins. If slight facial asymmetry is discovered through observation, it may be considered normal.
- Parkinson’s disease – Involuntary facial movement, such as levodopa-induced dyskinesias, can result in the lack of spontaneous facial motions, including a reduced blink rate.
- Bell’s palsy – The most prevalent type of acute lower motor neuron 7th nerve palsy is this one. Ramsay Hunt syndrome (ipsilateral loss of taste, buccal ulceration, painful vesicular eruption of the external auditory meatus), high blood pressure, otitis media, and parotid tumour are some of the other causes.
- Bilateral facial palsies – Guillain-Barre syndrome, Sarcoidoses, Lyme disease, and HIV infection are the most common causes of these facial palsies. It’s difficult to diagnose and gives the face a mask-like aspect, with a flat or non-expressive expression.
- VII nerve upper motor neuron lesion –
- Taste sensation – Taste sensation in the anterior 2/3rd of the tongue and feeling in the tragus of the ear are both checked by the examiner.
- Hyperacusis – This high-pitched sound is uncomfortably louder than usual.
6. How to examine Vestibulocochlear nerve(8th) :
The eighth cranial nerve, the vestibulocochlear nerve (auditory vestibular nerve), carries sound and balance information from the inner ear to the brain. The vestibular system is linked to balance, whereas the cochlear system is linked to hearing.
- Rinne’s test – We can use this test to distinguish between conductive and sensorineural deafness. The examiner first strikes the tuning fork and holds it near the external ear canal, vibrating the prongs towards the meatus (air conduction) and subsequently against the mastoid process (mastoid process) (bone conduction). The examiner next asks the patient which of the two sounds was louder. Rinne is positive, and AC>BC indicates that the patient’s hearing is normal. Rinne is negative, and BC>Ac denotes conductive deafness.
- Weber’s test – With the patient’s eyes closed and the base of the vibrating tuning fork firmly on the vertex or forehead in the middle, the examiner asks if sound is heard in the conductive ear or the ear with stronger cochlear function.
- Fistula test – To occlude the external auditory meatus, the examiner repeatedly crushes the tragus against it. If there is a perception of vertigo with nystagmus, this indicates an aberrant communication between the middle ear and the vestibular apparatus, such as in cholesteatoma erosion.
- Unterberger’s test – The patient is instructed to march on the spot while closing his eyes. The patient will then spin to the side of a labyrinth that has been injured.
- Dix hallpike positional test – The patient is requested to recline with his or her head stretched beyond the end of the couch and his or her neck rotated slightly. The examiner then looks for any nystagmus or vertigo. Nystagmus and vertigo are not present in normal people.
- Vestibular function – This is checked by having the patient follow the examiner’s finger up, down, and side to side as if they were looking at the examiner for any horizontal, vertical, or rotatory oscillations.
- Nystagmus testing – Testing for nystagmus, the Dix hallpike positional test, Unterberger’s test, and the Fistula test are all used to assess vestibular function.
7. How to examine Glossopharyngeal nerve(9th) :
This nerve aids in the transmission of feeling from the throat and tonsil. It has autonomic, secrerto-motor fibres for the parotid gland, as well as taste and smell from the posterior 1/3rd of the tongue.
- It may not be tested routinely, but it should be evaluated in children who are comatose or stuporous.
- Using an orange stick, examiner lightly touches the posterior pharyngeal wall to see the gag reaction. It’s nasty and has a low aspiration predictive value.
8. How to examine Vagus nerve(10th) :
The upper pharyngeal and laryngeal muscles are served by this nerve, which is both motor and sensory.
The examiner then asks for the patient’s speech and listens for dysarthria and dysphonia, which are common in patients with bilateral vagus palsy.
The examiner asks the patient to pronounce ‘Ah,’ and then uses a torch to examine the movements of the palate and uvula.
In a normal situation, the palate lifts symmetrically on both sides and the uvula remains in the middle.
- Unilateral vagus nerve palsy – In this case, palatal elevation weakening and uvula deviation on the unaffected side can be seen.
- Bilateral vagus nerve palsy – Here due to bilateral vagus nerve palsy, which is commonly caused by polyneuropathy or myasthenia gravis, bilateral palatal weakness is noticed.
- The patient is instructed to blow out his or her cheeks while keeping his or her lips tightly shut. The tester then listens for any audible air escaping from the nose.
- The examiner asks the patient to cough, and then tries to gauge the severity of the cough.
Swallow test :
This test is performed on a fully aware patient by giving 3 teaspoonfuls of water and watching for an absent swallow, a delayed cough, or a change in voice quality after each teaspoonful. If there is no problem, the same reflexes are observed as the patient drinks a glass of water.
9. How to examine Accessory nerve(11th) :
It has a spinal and cranial component. The upper trapezius and sternocleidomastoid muscle fibres are supplied by the spinal part, while the 10th nerve is supplied by the cranial part.
- From the front, any sternomastoid wasting and hypertrophy can be noticed.The patient’s back shows a wasting trapezius and asymmetry.
- The left/right steromastoid is tested by having the patient turn their hand right or left against resistance.
- Scapula winging is examined if it is present.
- To test the power, the patient is requested to shrug his shoulder while applying downward pressure with his hand.
- 11th nerve palsy can be caused by a variety of conditions, including myotonic dystrophy, myopathies, myasthenia, and motor neuron disease.
10. How to examine Hypoglossal nerve(12th) :
- This is a motor nerve to the muscles of the tongue. So all the tests are related with the tongue.
- Looking for wasting, fasciculation, or involuntary movement of the tongue, which happens in chronic bilateral palsy, is a way to test the nerve’s function.
- The examiner then asks the patient if he or she has any tongue protrusion, noting any weakness or deviation to the affected side.
Another test requires the patient to press his or her tongue against each cheek as the examiner presses his or her cheek from the outside with his or her fingers. - Finally, the patient is requested to quickly move his tongue from side to side.