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 NervesI Olfactory Nerve (Sensory)II Optic Nerve (Sensory)III Oculomotor Nerve (Motor)IV Trochlear Nerve (Motor)V Trigeminal Nerve (Mixed)VI Abducent Nerve (Motor)VII Facial Nerve (Mixed)VIII Vestibulocochlear nerve (Sensory)IX Glossopharyngeal Nerve (Mixed)X Vagus Nerve (Mixed)XI Accessory Nerve (Motor)XII 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.

Practical No : 21

(II) Optic NerveExamination 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 SuperiorisThe Medial RectusThe 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 :

- 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.

- Therefore, looking upward and downward in this position will involve, and test, only these muscles.

Medial Lateral

Inferior Oblique

Superior Oblique

Superior Rectus

Inferior Rectus

Medial Rectus Lateral Rectus

Inferior Oblique

Superior Rectus

Inferior Rectus

Superior Oblique

(Moves eye medially) (Moves eye laterally)

(Elevates the eye when in mid position)

(Depresses the eye when in mid position)

(Elevates eye when eye is turned medially)

(Depresses eye when eye is turned medially)

(Depresses eye when eye is turned laterally)

(Elevates eye when eye is turned laterally)

Lateral Medial

Ocular axis

Superior Rectus

Superior Oblique

Superior Rectus

Superior Oblique

Lateral Medial

(V) Trigeminal Nerve

- This is a mixed nerve, which is made up of the following,Ophthalmic DivisionMaxillary DivisionMandibular 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.

- 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.

Ophthalmic Division (Va)

Maxillary Division (Vb)

Mandibular Division (Vc)

C2

C4

C3

- 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

Motor Root of Facial Nerve

Nervus Intermedius

Auditory NerveInternal Auditory Meatus

Stylomastoid Foramen

Glossopharyngeal Nerve

Vagus Nerve

Geniculate Ganglion

Nerve to Stapedius

Lingual NerveChorda Timpani

To facial muscles

Circumvallate Pappillae

Anterior 2/3rds of the tongue

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 LesionLower part of the face on the opposite side is affected. Upper part preserved.

Lower Motor Neuron LesionBoth 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 functionsTest 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

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.

Proprioceptive organs in joints and muscles

Vestibular nuclei

Basal Ganglia

The corticospinal system

Olivary nuclei

Cerebellum

Each Red Nucleus

Vestibular Nuclei

Basal Ganglia

The corticospinal system

Afferents Efferents

- 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.