SURGICAL ANATOMY OF CRANIAL NERVES

GUIDED BY PRESENTED BY:DR.RAMAKRISHNA DR.MURARI WASHANIDR.VIVEK I YEAR M.D.S

CONTENT INTRODUCTION

CRANIAL NERVES

CLINICAL TESTING OF NERVES

INTRODUCTION

An example mnemonic sentence for the initial letters "OOOTTAFVGVAH" is "Oh, oh, oh, to touch and feel very good velvet...ah,

OLFACTORY NERVE

The olfactory nerve transmits olfactory impulses from the olfactory epithelium of the nose to the brain

It is actually a collection of sensory nerve rootlets that extend down from the olfactory bulb and pass through the many openings of the cribriform plate in the ethmoid bone.

Clinical notes

Anosmia ( loss of sense of smell)

CSF Rhinnorhoea

Hyposmia (a decreased sense of smell)

Parosmia (a perversion of the sense of smell)

Cacosmia (awareness of a disagreeable or offensive odour that does not exist)

Test:-

Bedside testing with pure (non-irritant) odours should be performed during early recovery

Serial testing should be done in patients with anosmia : should try ammonia

MRI imaging frequently reveals abnormalities in the olfactory bulbs and tracts and in the inferior frontal lobes in patients with posttraumatic olfactory dysfunction

OPTIC NERVE

Sight is dependent not only on cerebral cortex but also on other six cranial nerve.

Occulomotor ,trochlear nerve and abducent nerve innervate the extrinsic occular muscle and control movement of eye ball.

Pain, touch and pressure sensation is carried by the opthalmic nerve.

Facial nerve innervate the orbicularis oculi muscle.

CLINICAL NOTES:- Section of one optic nerve causes blindness in

one eye Bitemporal hemianopia Homonymous hemianopia Exudates, haemorrhages and abnormalities of

blood vessels may be seen on retinoscopy and may be signs of generalized disease processes (e.g. diabetes, rheumatoid arthritis, etc.)

Damage to optic nerve can cause diplopia, blurring of vision

Clinical testing Confrontation test –

Snellens test-

Colour vision is tested using Ishihara plates which identify patients who are colour blind.

Occulomotor

INTRODUCTION  Occulomotor nerve supplies the levator palpebral superioris , Superior rectus, medial rectus, inferior rectus and inferior oblique

CLINICAL NOTES:- Occulomotor nerve injury

Ptosis- paralysis of levator palpabre

lateral squint

spasm of the muscles supplied by it (e.g. spasm of medial rectus leading to a medial squint.

TROCHLEAR NERVE

Trochlear nerve supplies the superior oblique. It is the smallest nerve in terms of the number

of axons it contains. It has the greatest intracranial length

o trochlear nerve is so called because superior oblique (which it supplies) is arranged as a pulley (Latin: trochlea – pulley).

Clinical notes.limiting infero-lateral moment of eyeInjury to the trochlear nerve can cause vertical diplopia on looking downward which improves with contralateral head tilt and worsens with ipsilateral head tilt.

Trigeminal nerve

Originate from trigeminal ganglion.

largest cranial nerve

contains both sensory & the motor fibres

The word trigeminal is derived from the word ‘trigemina’ meaning triplet

DIVISIONS OF TRIGEMINAL NERVE: 1. Ophthalmic nerve 2. maxillary nerve 3. mandibular nerve

 OPTHALMIC BRANCH:

transmits sensory fibres from the eyeball, the skin of the upper face and anterior scalp, the lining of the upper part of the nasal cavity

and air cells, and the meninges of the anterior cranial fossa.

Clinical notes1.Corneal reflex 2.Supraorbital injuries

3.Ethmoid tumours

4.Nasal fractures

MAXILLARY NERVE The maxillary nerve transmits sensory fibres

from the skin of the face between the palpebral fissure and the mouth, from the nasal cavity and sinuses, and from the maxillary teeth.

The maxillary division gives off branches in four division : In the middle cranial fossa In the ptreygopalatine fossa In the infra-orbital groove and canal On the face ( Terminal branches )

Branches in the middle cranial fossa : middle meningeal nerve. Branches in pterygopalatine fossa : 1. Zygomatic nerve a.Zygomaticofacial nerve b.Zygomaticotemporal nr 2. Pterygopalatine nerve a.Orbital nerve b.Nasal nerve - Posterior superior lateral nasal branch . - Medial or septal branch. c.Palatine nerve Posterior superior alveolar branches : Branches in the infraorbital groove and canal : - Middle superior alveolar nerve. - Anterior superior alveolar nerve. Terminal branches - Inferior palpebral branches - Lateral nasal branches - Superior labial branches

Clinical notes1 Infraorbital injuries: malar fractures2 Maxillary sinus infections3 Maxillary antrum tumours4 Maxillary teeth abscesses Clinical testingTest skin sensation of lower eyelid, cheek and upper lip

MANDIBULAR BRANCH The mandibular nerve is a mixed sensory and

motor nerve.

It transmits sensory fibres from the skin over the mandible , side of the cheek and temple, the oral cavity and contents, the external ear, the tympanic membrane and temporomandibular joint.

It is the largest of all the three divisions.

Clinical notes1 Lingual nerve damage2 Inferior alveolar nerve and inferior alveolar nerve block3. TRIGEMINAL NEURALGIA:- Clinical testing1 Sensory: Test skin sensation of chin and lower lip.2 Motor: Feel contractions of masseter, temporalis. Open jaw against resistance (pterygoids, mylohyoid, anterior digastric)

ABDUCENT NERVE

Supplies lateral rectus muscle. Note: the abducent nerve is so called because lateral rectus abducts the eyeball.

The abducent nerve innervates lateral rectus muscles exclusively.

It emerges from the brain stem between the pons and the medulla oblongata and usually runs through the inferior venous compartment of the petroclival venous confluence in a bow shaped canal, Dorello’s canal.

DAMAGE TO THE ABDUCENS NERVE : - In a complete injury of the abducent nerve, the

affected eye is turned medially. In an incomplete injury, the affected eye is seen at midline at rest, but the patient cannot deviate the eye laterally.

-Combined injuries of the III, IV and/or V nerves are common and can result in the loss of depth perception and reading and visual scanning problems

FACIAL NERVE

The facial nerve supplies the muscles of facial expression.

taste sensation from the anterior portion of the tongue and oral cavity.

It is a mixed type of nerve, contains both sensory & motor fibres

 

Course and branches Intracranial course and branches

Extracranial course and branches

The most important thing about the intracranial course of VII is its relationship to the middle ear.

The most important thing about the extracranial course is its relationship to the parotid gland.

Clinical notes1. Parotid disease

2. Stapedius: hyperacusis (cannot tolerate sound)

3. Bell’s palsy

4. Facial nerve injury in babies- mastoid rudimentry

Clinical testing1. Observe the face. Normal facial movements (lips, eyelids, emotions) and the presence of normal facial skin creases indicate an intact nerve.

2. Test strength by trying to force apart tightly closed eyelids. This should be difficult.

VESTIBULOCOCHLEAR NERVE:-

The vestibulocochlear nerve is the sensory nerve for hearing (cochlear) and equilibration (vestibular).

It is also known as the statoacoustic nerve.Origin and course Arises laterally in cerebellopontine angle.

Passes with facial nerve into internal acoustic meatus (temporal bone). Cochlear portion (anteriorly) and vestibular portion (posteriorly). Vestibulocochlear nerve does not emerge externally.

TWO PARTSA.COCHLEAR NERVE:- CONCERNED WITH HEARING2.VESTIBULAR NERVE:-CONCERNED WITH BALANCINGCLINICAL NOTES1.Lesions- Hearing defects2.TRAUMA- IN FRACTURE OF MIDDLE FOSSA - COMPRESSED BY TUMOUR

Tests- Rinne’s Weber’s

GLOSSOPHARYNGEAL NERVE

The main function of the glossopharyngeal nerve is the sensory supply of the oropharynx and posterior part of the tongue.

BRANCHES The glossopharyngeal nerve has following

branches: i) Tympanic ii) Carotid iii) Pharyngeal iv) Muscular v) Tonsillar vi) Lingual

Clinical notes:- Glossopharyngeal neuralgia

Swallowing difficulties

Tardive dyskinesia: tardive dyskinesia is characterized by repetitive, involuntary, purposeless movements

Testing of nerve Tickling the posterior wall of pharynx Taste sensibility on the posterior 1/3rd of tongue

VAGUS NERVE

The main functions of the vagus are phonation and swallowing. It also transmits cutaneous sensory fibres from the posterior part Of the external auditory meatus and the tympanic membrane.

It is so called because of its extensive( vague) course through the head, neck & thorax

The vagus is the most extensively distributed of all cranial nerves. Its name reflects both its wide distribution and the type of sensation it conveys (Latin: vagus – vague, indefinite, wandering)

Clinical notes

1. Palatal elevation – ‘ah’ glossopharyngeal and vagus nerves.

2. Vagal reflexes: coughing, vomiting, fainting

3. Referred pain

4. Vocal cords

Clinical testing

If speech is normal, the vagus nerves are fine. Tradition and convention, however, often demand the charade of testing them.

1 Listen to speech.2 Gag reflex3 Testing palatal, pharyngeal movements, and listening to speech are tests of motor components of IX, X and cranial XI .They are thus tests of the nucleus ambiguss.

ACCESSORY NERVE

The accessory nerve has two parts: cranial and spinal. Oddly enough, when clinicians refer to the eleventh cranial nerve, or accessory nerve, they almost always mean spinal accessory

Origin and course of spinal accessory)• Rootlets from upper four or five segments of spinal cord con-tinue series of rootlets of IX, X and cranial XI.• Emerge between ventral and dorsal spinal nerve roots, just behind denticulate ligament.• Ascends through foramen magnum to enter posterior cranial fossa.• Briefly runs with cranial XI before emerging through jugularforamen (middle compartment).• Passes deep to sternocleidomastoid which it supplies.• Enters roof of posterior triangle of neck. Surface marking in poste-rior triangle: one third of way down posterior border of sternocleidomastoid to one third of way up anterior border of trapezius.

Clinical notes• The accessory nerve is vulnerable in the posterior triangle as it crosses the roof. • Such injuries result in paralysis of trapezius (but not sternocleidomastoid which it has already supplied) and thus shoulder abduction beyond 90° involving scapular rotation is impaired (hair grooming, etc.).• The accessory nerve may be damaged in dissection Of the neck for malignant disease, in biopsy of enlarged lymph nodes in and around the posterior triangle, or in penetrating injuries to this region.

Clinical testing of spinal accessory 1. Ask the patient to shrug the shoulders (trapezius) against

resistance. 2. Ask the patient to put hand on head (trapezius: shoulder

abduction beyond 90°). 3. Ask the patient to move the chin towards one shoulder

against resistance (contralateral sternocleidomastoid).

HYPOGLOSSAL NERVE:

The hypoglossal nerve supplies the muscles of the tongue. Movements of the tongue are important in chewing, in the initial

stages of swallowing and in speech. It also conveys fibres from C1 which innervate the strap muscle

Origin, course and branches •Originates from medulla by vertical series of rootlets between pyramid and olive. •Hypoglossal (condylar) canal in occipital bone.•Receives motor fibres from C1 and descends to submandibular region.•Turns forwards, lateral to external carotid artery, hooking beneath origin of occipital artery. Passes lateral to hyoglossus and enters tongue from below.•Gives descendens hypoglossi to ansa cervicalis carrying fibres from C1 to strap muscles; other C1 fibres remain with XII to supply geniohyoid.•Supplies intrinsic muscles of tongue, hyoglossus, genioglossus and styloglossus.

Clinical notes1. Hypoglossal nerve lesions•damage to the hypoglossal nerve in the neck would result in an ipsilateral lower motor neuron lesion. This would cause the protruded tongue to deviate to the side of the lesion.2.Carotid artery surgery, block dissection of neck•The hypoglossal nerve is vulnerable in surgery (e.g. carotid endarterectomy, block dissection of the neck for malignant disease) where it passes under the origin of the occipital artery.

Clinical testing

1.Ask the patient to protrude tongue. If it deviates to one side, thenthe nerve of that side is damaged – the tongue is pushed to theparalysed side by muscles of the functioning side.

2.Ask patient to push tongue into cheek, then palpate cheek to feel tone and strength of tongue muscles.

• GRAYS ANATOMY• ATLAS OF HUMAN BODY- NETTERS• LASTS ANATOMY – SINNATANBY• MONHEIMS LOCAL ANESTHESIA AND

PAIN CONTROL – C.RICHARD BENNETT

• Hollinshead's Textbook of Anatomy