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Amr Hassan, M.D. Associate professor of Neurology - Cairo

University

CRANIAL NERVES

olfactory nerve Pathway of smell :

From the receptors in the olfactory mucosa the fibers of

the olfactory nerve pierce the cribriform plate of the

ethmoid bone and run in the olfactory groove to relay in

the olfactory bulb. A new set of fibers travels in the

olfactory tract to terminate in the olfactory sensory area

in the uncus of the temporal lobe of both sides

olfactory nerve

olfactory nerve lesion Unilateral anosmia Bilateral anosmia

a) Traumatic: fracture cribriform plate.

b) Inflammatory: basal meningitis

c) Neoplastic e.g.olfactory groove

meningioma

a) E.N.T. causes as common

cold.

b) Congenital.

c) Hysterical.

2. Parosmia: Perverted sense of smell. usually unpleasant. Commonest cause

is Post-traumatic.

3. Olfactory hallucinations: Perception of smell usually unpleasant, in the

absence of stimulus. It is due to an irritative lesion in or near the uncus.

The olfactory

system consists

of the olfactory

epithelium, bulbs

and tracts along

with olfactory

areas of the brain

collectively

known as the

rhinencephalon.

Lesions of the olfactory nerve Anosmia

Unilateral : traumatic, inflammatory

neoplastic: Foster-Kennedy syndrome

• Bilateral : ENT, Hereditary, Hysterical • Parasomia NB: Olfactory hallucination is due to central olfactory dysfunction

Optic nerve The visual pathway

After converting light into electrical signals, rods and cones transmit this

information through the optic nerve.

Nasal fibers from each eye cross over to join the opposite optic nerve at the

optic chiasma to form the optic tract that contains the ipsilateral temporal

fibers and the contralateral nasal fibers. Optic tract fibers go to lateral

geniculate nucleus (LGN) in the thalamus; After leaving the lateral

geniculate nucleus the fibers optic radiation (the upper part of the optic

radiation passes through the parietal lobe while its lower part passes through

the occipital lobe) the primary visual cortex in the occipital lobe of the

cerebrum

Site of lesion Resulting deficit Explanation

1 The optic nerve Total loss of vision

2 The optic chiasm Bitemporal hemianopia A loss of vision in the temporal halves of both visual

fields because the chiasm carries crossing nasal fibers

from both eyes.

3 The optic tract Contralateral hemianopia Complete loss of vision in the opposite half of the

visual field (e.g. the nasal half of the field of the right

eye and the temporal half of the field of the left eye.

4 Lower optic radiation (temporal lobe)

Upper contralateral quadrantic anopia

A loss of vision in the upper quadrant of the opposite

half of the visual field of both eyes.

5 Upper optic radiation (parietal lobe)

Lower contralateral quadrantic anopia

A loss of vision in the lower quadrant of the opposite

half of the visual field of both eyes.

6 The visual cortex Contralateral hemianopia with macular sparing

Intact macular vision due to its double blood supply.

Monocular blindness

Bitemporal hemianopia

Contralateral homonymous hemianopia

Oculomotor nerve Anatomy

The oculomotor nerve originates from 3 nuclei motor neurons arise from the

oculomotor nucleus, parasympathetic fibers arise from Edinger-Westphal and

Perlia nuclei in the midbrain.

The nerve passes through the superior orbital fissure to reach the orbit.

The motor component of the nerve divides into a superior and inferior division:

The superior division supplies the levator palpebrae superioris and superior rectus

muscles.

The inferior division supplies the medial rectus, inferior rectus and inferior oblique

muscles.

The parasympathetic component of the oculomotor nerve travels with inferior

division to innervate the ciliary muscle and the constrictor pupillae muscle

Oculomotor nerve

External ophthalmoplegia:

Paralysis of Levator palpebrae superioris ptosis

Paralysis of superior rectus muscles, medial rectus, inferior rectus and inferior oblique muscles eye is deviated out and down (due to unopposed action of lateral rectus (supplied by Cr N VI) and superior oblique (supplied by Cr N IV).

Internal ophthalmoplegia :

Paralysis of constrictor pupillae muscle. mydriasis (dilated fixed pupil).

Oculomotor nerve lesion

Lesions of the oculomotor nerve

External ophthalmoplegia

Internal ophthalmoplegia

NB:

compression: early mydriasis and lost light reflex

infarction: pupillary reflex intact

Extraocular muscle movement

Ptosis

Partial Complete

Block the action of frontalis to differentiate between partial and complete ptosis.

The pupil

Constrictor pupillae muscle (parasympathetic supply)

Dilator pupillae (sympathetic supply)

Reflex Light Accommodation

Stimulus Light (torch). Near vision.

Receptor Rods and cones in retina. Rods and cones in retina.

Afferent Ipsilat. optic nerve. Ipsilat. optic nerve.

Center Midbrain: Ipsilat. pretectal nucleus EW nucleus on

both sides.

Occipital cortex.

Efferent Oculomotor nerve on both sides (parasympathetic

fibers) to ciliary ganglion then to constrictor papillae

through short ciliary nerves.

Oculomotor nerve on both sides ( parasympathetic fibers)

to ciliary ganglion constrictor papillae + ciliary muscle

to contact to increase refractive power of lens.

Oculomotor nerve on both sides ( motor fibers) Medial

recti on both sides convergence.

Response Miosis (Constriction of the pupils). 1. Convergence of the eyes due to contraction of both

medial recti muscles.

2. Miosis (constriction of the pupils) due to contraction

of the constrictor pupillae muscles.

3. Accommodation (increased refractive power of the

lens) due to contraction of ciliary muscles.

Accomodation reflex

Convergence

Miosis

Increase refractive

power of lens

Pupillary reflexes

Trochlear nerve

The trochlear nerve has only a somatic motor component which

innervates the superior oblique muscle of the contralateral orbit.

The nucleus of this nerve lies in the lower part of the midbrain.

The trochlear nerve supplies the superior oblique muscle which

turn the eye inwards & downwards (Thus help reading and

descending the stairs).

The Abducent Nerve The nucleus of this nerve lies in the lower part of the pons.

The nerve runs a long intracranial course to supply the lateral

rectus muscle which moves the eye outwards (laterally).

Lesion:

It is the most commonly affected ocular nerve because of its

long course.

Diplopia only when the patient looks outwards, towards the

paralysed side due to limitation of movement of the affected eye

on looking outwards.

Abducent nerve palsy Trochlear nerve palsy

Torticollis

Trigeminal nerve

main 4The trigeminal nerve has

nuclei. 1st 3rd are sensory while the

4th one is motor:.

•Spinal nucleus lies in medulla

oblongata

•Main sensory nucleus lies in pons

•Mesencephalic nucleus lies in midbrain

•Motor nucleus lies in pons .

It leaves the brain stem through the middle cerebellar peduncle form trigeminal ganglion, this ganglion lies in a depression in the floor of the middle

cranial fossa.

Ophthalmic nerve: which enter

the cranial cavity through the

superior orbital fissure. It receive

sensation from GREEN area.

Maxillary nerve: which enter the

cranial cavity through the

foramen rotundum. It receive

sensation from RED area.

Mandibular nerve: which enter the cranial cavity through the foramen ovale. It receive sensation from BLUE area.

Trigeminal nerve functions Functions: 2 functions

The motor function:

The motor fibers start in the motor nucleus in the pons. The fibers emerge from the pons & pass laterally below the trigeminal ganglion to join the mandibular branch of the nerve which leaves the cranial cavity through the foramen ovale. It supplies 7 muscles:

The muscles of mastication: temporalis, masseter, lateral & medial pterygoids.

Three other muscles: anterior belly of digastric, mylohyoid and tensor palati.

بت و بت : سوف الفرق واحدة خدودها مدورين و التانية شفايفها بيضاويين

Trigeminal nerve functions The sensory function:

Fibers carrying pain and temperature sensations from

the 3 divisions run downwards to relay in the spinal

nucleus in the lower part of the medulla on the same side.

In this nucleus:

The face is represented upside down i.e. ophthalmic

fibers end in the lower part of the nucleus while the

mandibular fibers end in its upper part.

Trigeminal nerve functions The peripheral part of the face is represented in the inner

part of the nucleus and the central part of the face is

represented in its outer part.

Fibers carrying proprioceptive sensations from the 3 divisions

run upwards and relay in the mesencephalic nucleus in the

midbrain, on the same side . Fibres carrying touch from the 3

divisions pass directly to the main sensory nucleus in the pons

on the same side.

Lesions of the trigeminal nerve Loss of sensations on the same side of the face (sparing

the angle of the mandible that supplied by C2).

Weakness of the muscles of mastication on the same side of the lesion.

Deviation of the jaw to the affected side due to the unopposed action of the pterygoid muscles of the healthy side.

Trigeminal Neuralgia Definition: Paroxysmal pain along distribution of trigeminal nerve. Clinical picture: Pain is brief (Seconds to 1-2 minutes) and paroxysmal, occur in Several attacks, Stabbing or Shocklike and is typically Severe. One (Single) or more branches of the trigeminal nerve (usually maxillary or mandibular) are involved. Pain is unilateral (rarely bilateral). Trigger points Various triggers may commonly precipitate a pain attack. Light touch or vibration is the most provocative. Activities such as shaving, laughing, brushing teeth and face washing. Pain provokes brief muscle Spasm of the facial muscles, thus producing the tic. Investigations: MRI brain to exclude an uncommon mass lesion or aberrant vessel compressing the nerve roots. Treatment: Medical: Carbamazepine (Tegretol) is the drug of choice. B. Surgical

Motor affection: Weakness of muscles of mastication on the same side of the

lesion

Deviation of the jaw to the affected side

Reflex affection Ipsilateral loss of corneal and conjunctival refelx.

Ipsilateral loss of palatal refelx.

Lost jaw reflex

Exaggerated jaw reflex BILATERAL UMNL ABOVE THE PONS.

Facial nerve

The facial nerve is a mixed nerve, as it contains motor,

sensory and autonomic fibers.

Anatomy of the motor part:The motor nucleus of the

facial nerve is located in the pons.The upper part of the

nucleus is bilaterally supplied from the pyramidal tracts

of both sides, while its lower part is unilaterally supplied

from the pyramidal tract of the opposite side only.

Facial nerve From the nucleus, the motor fibres pass through the

cerebello pontine angle in close proximity to Cr.N. V & VIII

then enter through the internal auditory meatus, into

the facial canal where it becomes adherent to its sensory and

autonomic parts.

It then leaves the canal through the stylomastoid foramen,

passes through the parotid gland to divide into its terminal

branches that supply the following muscles.

Facial nerve Muscles of expression Other muscles

1. Frontalis

2. Oricularis oculi

3. Orbicularis oris

4. Buccinator

5. Retractor anguli

1. Platysma.

2. Stapedius

3. Posterior belly of the

digastric muscle.

4. Stylohyoid.

•Stylohyoid

•Post. Belly of diagastric

•Stapidus

•platysma

بس بس

Facial nerve Anatomy of the sensory and autonomic parts: In the facial canal lies the

geniculate ganglion, which contains unipolar cells. The process of these cells

divides in a T-shaped manner into a peripheral branch and a central branch.

1. The peripheral branch runs laterally and divides into the greater superficial

petrosal nerve and the chorda tympani.

a. The greater superficial petrosal (GSP) nerve passes forwards to

relay in the sphenopalatine ganglion where a new set of fibres gives

autonomic supply to the lacrimal gland.

b. The chorda tympani leaves the facial nerve before the stylomastoid foramen, to

supply the submaxillary and sublingual salivary glands and to carry taste

sensations from the anterior 2/3 of the tongue.

Facial nerve

The central branch passes centrally, joins the motor part of the nerve,

then enters the cranial cavity through the internal auditory meatus as

the nervus intermediusenters the brain stem terminate in the

solitary nucleus in the medulla. A new set of fibers passes from the

nucleus to the opposite side and runs upwards to terminate in the

lower part of the ;cortical sensory area, where taste sensation from

the anterior 2/3of the tongue is perceived.

Facial nerve

U.M.N.L L.M.N.L

Affecting Δ tract above facial nucleus. Affecting the facial motor nucleus or the nerve

itself.

Paralysis of the muscles of lower half of the

face on the opposite side of the lesion

(supplied from the opposite ∆ tract only)

leading to:

a. Obliteration of the naso-labial fold.

b. Dropping of the angle of the mouth

with dribbling of saliva.

c. Accumulation of food behind the cheek

d. Inability to blow the cheek.

e. Inability to show the teeth properly.

Paralysis of the muscles of the upper & lower

halves of the face on the same side of the lesion

leading to:

a e and in addition:

f. Inability to raise the eyebrows with absence

of wrinkles of the forehead.

g. Inability to close the eye, when the pt.

attempts to close his eye the eyeball rolls

upwards (Bell's phenomenon).

Paralysis involves the voluntary movement;

it spares the emotional & associative

movements (which are supplied by extra ∆

fibers).

Paralysis affects voluntary, emotional &

associative movements.

There is associated hemiplegia on the

same side of the facial paralysis.

If there is hemiplegia, it is on the opposite side

of the facial paralysis (crossed hemiplegia).

Upper motor neurone Facial nerve lesion

Site

of lesion

Facial

muscles

Taste

sensation.

Salivation

lacrimation

Other

Features

Causes

Nuclear

Lesion

Paralysed Intact Intact Hemiplegia

on opposite

side

Vascular:

Vertebro-basilar insuf.

Millard-Gubler

syndrome.

Infective:

Encephalitis.

Poliomyelitis.

Neoplastic:

Astrocytoma

Glioma

Demyelinating: M.S.

Cerebello-

Pontine Angle

Lesion:

Paralysed ↓ ↓ Cr.n.

V,VIII

palsies on

same side

Infective:

Basal meningitis.

Neoplastic:

Acoustic neuroma.

Meningioma

Facial Canal

Lesion:

Paralysed ↓ if chorda

tympani is

involved.

Lacrimation

↓ If the

GSP nerve

is involved.

Salivation↓

if chorda

tympani is

involved.

Traumatic:

Fracture base.

Infective:

Otitis media.

Herpes zoster.

Neoplastic:

Facial neuroma.

Bell's palsy.

Extracranial

Facial Lesion:

After its exit

from the

stylomastoid

foramen.

Paralysed Intact Intact Intact Neuropathy:

Diabetic

Myasthenia.

Myopathy:

Facioscapulo-humeral.

Myotonia Atrophica.

Neoplastic:

Invasion by a tumour

e.g. from parotid.

Bell’s palsy

Definition: It is an acute paralysis of the facial nerve near the stylomastoid foramen (i.e. LMN). It is usually unilateral, may be recurrent & sometimes runs in families.

Aetiology: Many causes have been suggested:

1. Exposure to air drafts usually precedes the onset; this may lead to ischaemia, oedema & compression of the nerve at the stylomastoid foramen.

2. It may be 2ry to a neurotropic virus e.g. Herpes zoster.

3. It may be autoimmune, as evidenced by high levels of immunoglobulins in the patient's serum.

Bell’s palsy

Clinical Picture:

The onset is usually acute with pain behind the ear One or two days later, there is complete

paralysis of the facial muscles on the affected side of L.M.N. nature.

Treatment :

1. Medical:

a) Oral steroids

b) Protection of the exposed cornea.

2. Physiotherapy:

3. Surgical:

a) Decompression of the facial nerve.

b) Facial nerve grafting.

Fig. 30: A patient with Lt 7th nerve palsy

Prognosis:

Full recovery occurs in about 80% of the cases, 15% experience some kind of

permanent nerve damage and 5% remain with severe sequelae.

Poor prognostic factors:

- Complete palsy or severe degeneration (electrophysiology).

- No signs of recovery by three weeks.

- Age >60.

- Severe pain.

- Ramsay Hunt's syndrome (herpes zoster virus).

- Associated with either hypertension, diabetes, or pregnancy.

Bell’s palsy

Those with axonal degeneration may not show any re-innervation for three months and recovery may be partial or not at all.

Synkinesis is often seen e.g. blinking causes the angle of the mouth to contract.

Also aberrant parasympathetic re-innervation may cause symptoms such as gustatory lacrimation ('crocodile tears').

Bell’s palsy

The Vestibulo-Cochlear Nerve This nerve is composed of 2 divisions: 1. Vestibular. 2. Cochlear

1. Vestibular branch:

Fibers originating from the semicircular canal, utricle & saccule in the inner ear join the

cochlear division in the internal auditory canal (see fig. 31).

They then pass in the cerebello-pontine angle to enter the brain stem where they relay in the

vestibular nuclei in the brain stem. New fibres take 3 pathways to:

1. The archicerebellum, concerned with equilibrium.

2. The medial longitudinal bundle, concerned with the synchronous movements of the eyes,

head & neck.

3. The cerebral cortex, concerned with the perception of the sense of vertigo.

Lesion of the vestibular division results in:

1. Vertigo. 2. Ipsilateral incoordination. 3. Spontaneous nystagmus.

The Vestibulo-Cochlear Nerve 2. Cochlear nerve:

Fibers originating from the ganglion cells of the cochlea pass centrally from the inner ear through the internal auditory canal where they are joined by the vestibular division. They then pass through the cerebello pontine angle to enter the brain stem, where they relay in the cochlear nucleus (in the lower pons) lateral lemniscus medial geniculate bodies (M.G.B.) auditory sensory area in the temporal lobes (see fig. 31).

Lesion:

Tinnitus, in irritative lesions.

Deafness, in destructive lesions.

Vertigo Definition: It is the sense of rotation of the body in steady

surroundings or the reverse that is usually aggravated by

movements of the head and it persists in all positions: sitting,

standing or supine.It is usually associated with autonomic

manifestations in the form of nausea, vomiting, pallor and

bradycardia.

N.B. Vertigo should be differentiated from dizziness, giddiness

and light headedness where the unsteadiness is not associated

with a sense of rotation.

Vertigo

Causes:

Table 8: causes of vertigo.

Labyrinthine Peripheral nerve Brain stem

Physiological: sea

sickness, car sickness.

Pathological:

labyrinthitis, Meniere's

disease, otosclerosis.

Cerebello-pontine angle

lesion as acoustic

neuroma.

Vestibular neuritis.

Vertebro-basilar artery

insufficiency.

Posterior inferior cerebellar

artery occlusion.

M.S.

Treatment: Treatment of the cause and medical.treatment for vertigo

IX. The Glossopharyngeal Nerve This is a mixed nerve carrying motor, sensory &

autonomic (parasympathetic) fibers.

Motor fibers: supplying stylopharyngeus and constrictors of the pharynx.

Sensory fibers: receive general sensations from the posterior ⅓ of tongue, pharynx & tonsils and taste sensation from the posterior ⅓ of tongue.

Autonomic fibers: Parasympathetic fibers to the parotid gland (see fig. 32).

Lesion:

Ipsilateral loss of taste & general sensations from the posterior ⅓ of the tongue.

Ipsilateral loss of the pharyngeal reflex (afferent Cr.N. 9, efferent Cr.N.10).

IX. The Glossopharyngeal Nerve

The Vagus Nerve

This is a mixed nerve carrying motor, sensory & autonomic (parasympathetic) fibers (see fig. 33).

Anatomy:

1. Motor fibers: to the soft palate, pharynx & larynx.

2. Sensory fibers: from - The skin over the external auditory meatus.

- The thoracic & abdominal viscera.

3. Autonomic fibers: Parasympathetic fibers to the heart (inhibitory), the G.I.T. & the bronchial tree (secretory & motor).

Lesion:

1. True Bulbar Palsy:

- Bulbar symptoms: Dysphagia, dysarthria, dysphonia & nasal regurge.

- Ipsilateral loss of palatal & pharyngeal reflexes.

2. Dysautonomia: Tachycardia & constipation. `

Glossopharyngeal and vagus nerves

Deviation of the palate

Palatal reflex

Pharyngeal reflex

Swallowing water

Palatal deviation

XI. The Accessory Nerve This nerve is purely motor & is formed of 2 parts.

Anatomy:

1. Cranial part: It arises in the medulla & runs with the vagus nerve to

share in the motor innervation of the soft palate & pharynx.

2. Spinal part: It arises from the A.H.C. of the upper five cervical

segments, ascends alongside the spinal cord and enters the cranial

cavity through the foramen magnum. It joins the cranial portion to exit

through the jugular foramen to supply the sternomastoid &

trapezius muscles (see fig. 34).

Lesion: Ipsilateral paralysis of the sternomastoid & trapezius muscles.

XII. The Hypoglossal Nerve This is a purely motor nerve which supplies the

intrinsic muscles of the tongue.

Anatomy: Its fibers arise from the cells of the hypoglossal nucleus in the medulla hypoglossal canal hypoglossal foramen intrinsic muscles of the tongue (see fig. 35).

Lesion:

Table 9: U.M.N. and L.M.N. hypoglossal nerve.

. U.M.N.L L.M.N.L.

Unilateral Deviation of the tongue to the

opposite side of the lesion.

No wasting or fasciculation.

Deviation of the tongue to the side of

the lesion.

Wasting and fasciculation.

Bilateral Inability to protrude the tongue

(spastic tongue)

No wasting or fasciculation.

Inability to protrude the tongue.

Wasting and fasciculation.

XII. The Hypoglossal Nerve

Inspect the tongue for: Deviation.

Wasting.

Fasiculations.

Abnormal movement

Evidence of systemic disease

Test for the power

The hypoglossal nerve

Thank you