Practical No : 21
EXAMINATION OF THE CRANIAL NERVES & CEREBELLAR
FUNCTION
Objectives :
Examination of the Cranial Nerves
At the end of the practical the student should be able to,
1. Enumerate the Cranial Nerves and describe their pathways.
2. Explain the action and the physiological basis underlying the examination of each
of the Cranial Nerves.
3. Accurately perform a detailed examination of each of the Cranial Nerves.
4. Describe the major abnormalities seen in some of the main Cranial Nerve
Lesions.
The Cranial Nerves
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
Olfactory Nerve
(Sensory)
Optic Nerve
(Sensory)
Oculomotor Nerve (Motor)
Trochlear Nerve
(Motor)
Trigeminal Nerve
(Mixed)
Abducent Nerve
(Motor)
Facial Nerve
(Mixed)
Vestibulocochlear nerve (Sensory)
Glossopharyngeal Nerve (Mixed)
Vagus Nerve
(Mixed)
Accessory Nerve
(Motor)
Hypoglossal Nerve (Motor)
Examination Procedure
(I) Olfactory nerve
-
-
Prior to examination, inquire from the patient about any infection or inflammation
of the respiratory passages. Eg. Sinusitis, common cold
Test each nostril separately.
The patient is asked to close one nostril at a time and sniff a vial containing an
easily recognizable substance, and identify the odour perceived.
Eg. Cinnamon oil, clove oil, vanilla
Anosmia
The absence of any sense of smell
Parosmia
Perception of a different, often foul, smell even in the
presence of a sweet one.
Bilateral anosmia is most often due to inflammation / infection of the respiratory
passages
Unilateral anosmia is most often significant.
(II) Optic Nerve
Examination is discussed in the practical on vision.
(III) Oculomotor, (IV) Trochlear and (VI) Abducent nerves
-
-
-
Levator Palpabrae Superioris and six other muscles are collectively known as the
external ocular muscles.
As these three cranial nerves supply all the external ocular muscles, they are best
tested together.
Oculomotor nerve supplies
The Levator Palpabrae Superioris
The Medial Rectus
The Inferior Rectus &
The Inferior Oblique Muscles
Trochlear Nerve supplies
The Superior Oblique Muscle
Abducent Nerve supplies
The Lateral Rectus Muscle
Apart from the above, parasympathetic pre-ganglionic fibre also run with the
oculomotor nerve.
Examination begins with the inspection of the eyelids. Ptosis? Partial Ptosis? Which
side?
Rate of blinking should be examined.
Look for the size and equality of pupils (both sides).
Normally
3 – 5 mm diameter
< 3 mm diameter
Miosis
> 5 mm diameter
Mydriasis
-
If not checked with the Optic nerve, the pupillary reflexes should be checked
 Direct and consensual light reflex.
 Accommodation reflex.
-
Ocular movements
-
-
-
Inspect for the direction of deviation (if any) of the optical axes of the eyes
from the parallel (squint?).
Ask the patient if they see double at any time.
The patient should be first asked to move his eyes, upwards, downwards,
medially, laterally, medially then up and downwards, and laterally then
upwards and downwards.
Then the examiner holds the patient’s head with one hand, in order to
stabilize it, holds and object in front of him and asks the patient to follow
the object while it is moved in the above mentioned directions.
First test with both eyes open, then if necessary, check with each eye
closed.
At each direction the object is moved, the patient is asked to report any
double vision.
Also observe for Nystagmus (involuntary oscillations of the eyes) at this
time.
Interpretation :
Medial
(Elevates eye when eye
is turned medially)
Inferior
Oblique
Inferior Oblique
-
-
(Moves eye laterally)
Superior
Oblique
Inferior
Rectus
(Depresses the eye
when in mid position)
Inferior Rectus
(Depresses eye when
eye is turned laterally)
The Superior and Inferior Obliques and the Superior and Inferior Recti are attached
to the eyeball at an angle.
Therefore, in order to isolate their specific actions, the eyeball has to be moved
medially or laterally (adducted or abducted).
When the eye is abducted, the
ocular axis lies in line with the
Superior and Inferior Recti.
-
Therefore, looking upward or
downward in this position will
involve, and test, only these
muscles.
-
When the eye is adducted, the
ocular axis lies in line with the
Superior and Inferior Obliques.
-
Superior Rectus
Lateral Rectus
Medial Rectus
(Depresses eye when
eye is turned medially)
(Elevates eye when eye
is turned laterally)
Superior
Rectus
(Moves eye medially)
Superior Oblique
Lateral
(Elevates the eye
when in mid position)
Therefore, looking upward and
downward in this position will
involve, and test, only these
muscles.
Medial
Superior
Oblique
Ocular axis
Medial
Lateral
Superior
Rectus
Superior
Oblique
Lateral
Superior
Rectus
(V) Trigeminal Nerve
-
This is a mixed nerve, which is made up of the following,
Ophthalmic Division
Maxillary Division
Mandibular Division
-
Examination of this nerve involves examination of sensation, motor function and
reflexes.
-
Sensory functions
- The sensory distribution is to the face and scalp, upto the vertex.
- This territory is divided into three divisions as supplied by the 3 divisions of
the Trigeminal nerve.
- Test for light touch using a cotton wool swab.
- Test for pain using a toothpick.
- Make sure to test all three territories as well as compare both sides of the
face.
Ophthalmic Division
(Va)
C2
Maxillary Division
(Vb)
Mandibular Division
(Vc)
C3
C4
-
Motor functions
- Trigeminal nerve supplies the muscles of mastication.
- Initially, inspect for signs of muscle wasting on either side of the face.
- Ask patient to open and close jaw passively.
- Next, repeat this while the examiner applies resistance against opening of
the jaw. Look for deviation of the mandible. (pterygoids). In case of
paralysis, the lower jaw will deviate to the paralysed side.
- Ask patient to clench his teeth while the examiner palpates the masseter and
temporalis muscles of either side.
-
Reflexes
- Most important, is the Corneal Reflex, which is the first to disappear in a
lesion of the trigeminal nerve.
-
-
The patient is asked to look to a side while the examiner brings a rolled
piece of cotton wool from the opposite side.
Care should be taken not to approach from the front of the patient as this
might initiate a blink reflex.
Carefully touch the patient’s sclero-corneal junction with the tip of cotton
wool and observe for blinking.
The sensory path is via the Ophthalmic division and motor path via the
Facial nerve. Both nerves are thus tested.
The Jaw Jerk is performed with the patient staying with his mouth opened
slightly while the examiner places his thumb on the patient’s chin.
The examiner, then hits his own thumb with a knee hammer to elicit the jaw
jerk.
(VII) Facial Nerve
-
An extremely important nerve that innervates the muscles of facial expression.
Examination for lesions of the facial nerve require a thorough knowledge of its intra
and extra-cranial pathway
Geniculate Ganglion
Anterior 2/3rds
of the tongue
Motor Root of
Facial Nerve
Nerve to Stapedius
Nervus Intermedius
Lingual Nerve
Chorda
Timpani
Auditory Nerve
Internal Auditory Meatus
Stylomastoid Foramen
Glossopharyngeal Nerve
Vagus Nerve
To facial
muscles
Circumvallate Pappillae
Motor Function
- The two sides of the face should be compared, as well as the upper and lower
parts of the face. Signs of paralysis are usually obvious.
- Inspect for absence of expression and a less pronounced (flattened) nasolabial
fold on the affected side.
- There may be a widened palpebral fissure on the affected side.
- Inspect for drooping of the corner of the mouth with dribbling of saliva, on the
affected side.
- Ask the patient to wrinkle his forehead – the furrows of the brow on the affected
side are smoothed out.
- Ask the patient to shut his eyes tightly and keep them shut while the examiner
tries to open them. The eye on the affected side will fail to remain closed.
- Ask the patient to smile or bare his teeth - the mouth will be drawn towards the
normal side, as muscles are stronger.
- Ask the patient to whistle (impossible in VIIth nerve palsy).
- Ask patient to blow out his cheeks while the examiner taps both sides gently. Air
can be made to escape easily out of the affected side.
- Also, look for the action of the platysma muscle.
Sensory function
- The patient is asked to protrude his tongue while the examiner holds it gently with
a gauze swab.
- Test taste sensation over the anterior two thirds of the tongue thus,
 Sweet
Sugar / saccharin
 Salt
Salt
 Bitter
Quinine
 Sour
Vinegar
- These substances are placed on the tongue on each side, in turn, and the patient is
asked to identify the taste by pointing to the relevant word on a card shown to
him.
- The patient should be instructed not to speak.
Interpretation
The upper part of the face is supplied by both
cerebral hemispheres.
The lower part of the face is supplied by the
opposite hemisphere.
Upper Motor Neuron Lesion
Lower part of the face on the opposite side
is affected. Upper part preserved.
Lower Motor Neuron Lesion
Both upper and lower parts of the face on
the same side are affected.
(VIII) Vestibulocochlear (Auditory) Nerve
Examination is discussed in the practical on Auditory Function
(IX) Glossopharyngeal, (X) Vagus and (XI) Accessory Nerves
- Isolated lesions of the above nerves occur extremely rarely.
- Therefore, when testing, the Glossopharyngeal nerve, Vagus nerve and cranial part
of the Accessory nerve are tested together.
- The spinal part of the Accessory nerve is tested separately.
IX
Best tested by eliciting its sensory and reflex functions
Test for taste sensation in the posterior 1/3rd of the tongue.
Touch the posterior wall of the pharynx to elicit the “Gag” reflex.
X
The Vagus is Motor to the Soft Palate, Pharynx and Larynx.
Ask patient whether he experiences nasal regurgitation on swallowing
fluids.
Ask patient to pronounce the words, ‘Egg’, ‘Leg’ etc. the word may sound
like ‘Eng’.
Ask patient to open his mouth wide, and say “Aah” while the examiner
shines a torch to observe the soft palate. See whether there is deviation of
the uvula to one side, or if it is lifted straight up.
If paralysis is present, the uvula will deviate to the normal side.
Touch the posterior wall of the pharynx to elicit the “Gag” reflex.
XI
Since the Cranial part of the Accessory nerve is distributed to the palate
and pharynx via the Vagus nerve, tests for the Vagus nerve will also test
this section of the Accessoty nerve.
The Spinal Root of the Accessory nerve supplies the Trapezius and
Sternocleidomastoid muscles.
Ask the patient to shrug his shoulders while the examiner opposes the
action by pressing down on the shoulders. (Trapezius).
Ask the patient to turn his chin to both sides while the examiner opposes
this action and feels for the sternocleidomastoid muscle of the relevant
side.
(XII) Hypoglossal Nerve
- This is the nerve of the tongue, supplying all intrinsic and most extrinsic muscles of
the tongue.
- Ask patient to open his mouth wide, and observe the tongue for unilateral wasting
and fasciculation.
- Next, ask him to protrude his tongue. In case of paralysis, the tongue will deviate to
the paralysed side.
- The strength can be tested by asking the patient to push his cheek with his tongue
while the examiner resists this movement by pushing against the cheek from the
outside.
Examination of Cerebellar Function
Objectives :
At the end of the practical the student should be able to,
1. Explain the physiological basis of the functions of the cerebellum.
2. List the abnormalities manifested in disease of the Cerebellum.
3. Perform a quick examination of Cerebellar Functions.
Function of the Cerebellum
The cerebellum is involved with coordination
Proprioceptive organs in
joints and muscles
Each Red Nucleus
Vestibular Nuclei
Vestibular nuclei
Cerebellum
Basal Ganglia
Basal Ganglia
The corticospinal
system
The corticospinal
system
Olivary nuclei
Afferents
Efferents
Lesions of the Cerebellum
A cerebellar lesion can be reliably identified by examining for the following signs,
- Muscle Hypotonia
- Adiadochokinasia (Dysdiadochokinasia)
- Dysarthria
- Dysmetria
- Rebound Phenomenon
- Pendular Knee Jerk
- Ataxia
- Nystagmus
- Drunken Gait
- Intension Tremor
Examination of cerebellar function
- Ask patient to stretch out his arms. Look
for arm drift.
- Examine for muscle tone as explained in
the practical on Ex. of sensory and motor
systems, and observe for hypotonia.
- Ask the patient to tap alternately, the palm and back of one hand on the other hand or
thigh, in a rapid alternating movement. Observe whether the movement is clumsy,
sluggish or disorganized.
- Ask the patient to pronounce words like " British constitution", or “West Register
Street” after you. Observe for loud, slurred, halting or jerky speech.
- Ask the patient to stand or sit straight with
his arm outstretched and forefinger pointing.
Next, ask him to repeatedly stretch his arm
out and then touch his nose. If this is
possible, the examiner stretches his hand and
asks the patient to touch his finger to the
examiner's finger and then touch his own
nose. Observe for past pointing and intension
tremor.
- Ask patient to lie down on a bed in the supine position and perform the 'Heel - Shin"
test. (read. Motor system examination). Observe for jerky uncoordinated movements.
- With the patient seated on the
edge of a bed, ask him to stretch
out both arms. The examiner
then presses the arms down and
releases suddenly. A normal
person will be able to control
the subsequent movement. A
patient with a cerebellar lesion
cannot, and his arms will
rebound.
- With the patient seated on the edge of a bed,
the examiner should try to elicit the knee jerk.
Observe for a pendular response.
- Ask the patient to gaze laterally, observe for a
coarse, jerky nystagmus. The prominent
direction of the jerky movement will indicate
the side of the lesion.
- Draw a line on the ground and ask the patient
to walk with his head held straight. Observe for
a broad based, drunken type gait. Observe if
the patient staggers to one side. This will be the
affected side.