Ear

Facial Nerve and Its Disorders

ANATOMY AND FUNCTIONS OF FACIAL NERVE

Facial nerve is a mixed nerve having motor and a sensory root. The latter is also called the nerve of Wrisberg.

Nucleus of Facial Nerve

Motor nucleus of the nerve is situated in the pons. It receives fibres from the precentral gyrus. The function of forehead is preserved in supranuclear lesions because of bilateral innervation. The emotional movements such as smiling and crying are preserved in supranuclear palsies because of fibres from the thalamus

Course of Facial Nerve

Motor fibres take origin from the nucleus of VIIth nerve, hook round the nucleus of VIth nerve and are joined by the sensory root (nerve of Wrisberg). Facial nerve leaves the brainstem , travels through posterior cranial fossa and enters the internal acoustic meatus. At the fundus of the meatus (lateral most part of meatus), the nerve enters the bony facial canal, traverses the temporal bone and comes out of the stylomastoid foramen. The course of the nerve can thus be divided into:

1. Intracranial part

From pons to internal acoustic meatus (15-17 mm).

2. Intratemporal part

From internal acoustic meatus to stylomastoid foramen. It is further divided into: (a) Meatal segment. Within internal acoustic meatus (8-10 mm). (b) Labyrinthine segment. From fundus of meatus to the geniculate ganglion where nerve takes a turn posteriorly forming a "genu". The labyrinthine segment has the narrowest diameter . Thus oedema or inflammation can easily compress the nerve and cause paralysis. This is also the shortest segment of the nerve-only 4 mm. (c) Tympanic or horizontal segment. From geniculate ganglion to just above the pyramidal eminence. It lies above the oval window and below the lateral semicircular canal (11 mm). (d) Mastoid or vertical segment. From the pyramid to stylomastoid foramen. Between the tympanic and mastoid segments is the 2nd genu of the nerve (13 mm).

3. Extracranial part

From stylomastoid foramen to the termination of its peripheral branches

Branches of Facial Nerve

1. Greater superficial petrosal nerve

It arises from geniculate ganglion and carries secretomotor fibres to lacrimal gland and the glands of nasal mucosa.

2. Nerve to stapedius

It arises at the level of second genu and supplies the stapedius muscle.

3. Chorda tympani

It arises from the middle of vertical segment, passes between the incus and neck of malleus, and leaves the tympanic cavity through petrotympanic fissure. It carries secretomotor fibres to submandibular and sublingual glands and brings taste from anterior two-thirds of tongue.

4. Communicating branch

It joins auricular branch of vagus and supplies the concha, retroauricular groove, posterior meatus and the outer surface of tympanic membrane.

5. Posterior auricular nerve

It supplies muscles of pinna, occipital belly of occipitofrontalis .

6. Muscular branches

to stylohyoid and posterior belly of digastric.

7. Peripheral branches

The nerve trunk, after crossing the styloid process, forms two divisions, an upper temporofacial and a lower cervicofacial, which further divide into smaller branches in the substance of parotid gland. These are the temporal, zygomatic, buccal, mandibular and cervical and together form pes anserinus (goose-foot). They supply all the muscles of facial expression.

Blood Supply of Facial Nerve

It is derived from four blood vessels: (i) Anterior-inferior cerebellar artery supplies the nerve in CP angle; (ii) labyrinthine artery, branch of anterior inferior cerebellar artery, supplies the nerve in internal auditory canal; (iii) superficial petrosal artery, a branch of middle meningeal artery, which supplies geniculate ganglion and the adjacent region; and (iv) stylomastoid artery, branch of posterior auricular artery, which supplies the mastoid segment.

Electrodiagnostic Tests

These tests are useful to differentiate between neurapraxia and degeneration of the nerve. They also help to predict prognosis and indicate time for surgical decompression of the nerve.

1. Minimal nerve excitability test

2. Maximal stimulation test (MST)


3. Electroneuronography (ENoG)

4. Electromyography (EMG)

CAUSES OF FACIAL PARALYSIS
Table 14-1. Causes of facial paralysis

Central

Brain abscess
Pontine gliomas
Poliomyelitis
Multiple sclerosis
Intracranial part (cerebellopontine angle)
Acoustic neuroma
Meningioma
Congenital cholesteatoma
Metastatic carcinoma
Meningitis
Intratemporal part
(a) Idiopathic
Bell's palsy
Melkersson's syndrome
(b) Infections
Acute suppurative otitis media
Chronic suppurative otitis media
Herpes zoster oticus
Malignant otitis externa
(c) Trauma
Surgical: Mastoidectomy Stapedectomy
Accidental: Fractures of temporal bone
(d) Neoplasms
Malignancies of external and middle ear
Glomus jugulare tumour
Facial nerve neuroma
Metastasis to temporal bone (from cancer of breast, bronchus, prostate)
Extracranial part
Malignancy of parotid
Surgery of parotid
Accidental injury in parotid region
Neonatal facial injury (obstetrical forceps)
Systemic diseases
Diabetes mellitus
Hypothyroidism
Uraemia
Polyarteritis nodosa
Wegener's granulomatosis
Sarcoidosis (Heerfordt's syndrome)
Leprosy
Leukaemia
Demyelinating disease


A. IDIOPATHIC

1. Bell's Palsy

Sixty to seventy-five percent of facial paralysis is due to Bell's palsy. It is defined as idiopathic, peripheral(LMN) facial paralysis or paresis of acute onset. Both sexes are affected with equal frequency. Any age group may be affected though incidence rises with increasing age. A positive family history is present in 6-8% of patients. Risk of Bell's palsy is more in diabetics (angiopathy) and pregnant women (retention of fluid).

Aetiology

(a) Viral infection : Herpes simplex?

(b) Vascular ischaemia

(c) Hereditary

(d) Autoimmune disorder

Clinical Features

Onset is sudden. Patient is unable to close his eye. On attempting to close the eye, eyeball turns up and out (Bell's phenomenon). Saliva dribbles from the angle of mouth. Face becomes asymmetrical. Tears flow down from the eye (epiphora). Pain in the ear may precede or accompany the nerve paralysis. Some complain of noise intolerance (stapedial paralysis) or loss of taste (involvement of chorda tympani). Paralysis may be complete or incomplete. Bell's palsy is recurrent in 3-10% of patients.

Treatment

General

1. Reassurance.

2. Relief of ear pain by analgesics.
3. Care of the eye.
4. Physiotherapy or massage of the facial muscles gives psychological support to the patient.

Medical management

Steroids

Prednisolone is the drug of choice, the adult dose of prednisolone is 1 mg/kg/day divided into morning and evening doses for 5 days. Patient is seen on the 5th day. If paralysis is incomplete or is recovering, dose is tapered during the next 5 days. If paralysis remains complete, the same dose is continued for another 10 days and thereafter tapered in next 5 days. (total of 20 days). Contraindications to use of steroids include pregnancy, diabetes, hypertension, peptic ulcer, pulmonary tuberculosis and glaucoma. Steroids can be combined with acyclovir for Herpes zoster oticus or Bell's palsy.

Surgical treatment

Nerve decompression relieves pressure on the nerve fibres and thus improves the microcirculation of the nerve. Vertical and tympanic segments of nerve are decompressed. Some workers have suggested total decompression including labyrinthine segment by postaural and middle fossa approach.

Prognosis

Eighty-five to ninety percent of the patients recover fully. 10-15% recover incompletely and may be left with some stigmata of regeneration. Recurrent facial palsy may not recover fully.
2. Melkersson's Syndrome


It is also an idiopathic disorder consisting of a triad of facial paralysis, swelling of lips and fissured tongue. Paralysis may be recurrent. Treatment is the same as for Bell's palsy.

B. INFECTIONS

Herpes Zoster Oticus (Ramsay-Hunt Syndrome)

There is facial paralysis along with vesicular rash in the external auditory canal and pinna . There may also be anaesthesia of face, giddiness and hearing impairment due to involvement of Vth and VIIIth nerves. Treatment is the same as for Bell's palsy.

Infections of Middle Ear

Malignant Otitis Externa

C. TRAUMA

1. Fractures of Temporal Bone

Fractures of temporal bone may be longitudinal, transverse or mixed . Facial palsy is seen more often in transverse fractures (50%). Paralysis is due to intraneural haematoma, compression by a bony spicule or transection of nerve. In these cases, it is important to know whether paralysis was of immediate or delayed onset. Delayed onset paralysis is treated conservatively like Bell's palsy while immediate onset paralysis may require surgery in the form of decompression, re-anastomosis of cut ends or cable nerve graft.

2. Ear or Mastoid Surgery

Facial nerve is injured during stapedectomy, tympanoplasty or mastoid surgery. Paralysis may be immediate or delayed and treatment is the same as in temporal bone trauma. Sometimes, nerve is paralysed due to pressure of packing on the exposed nerve and this should be relieved first.
3. Parotid Surgery and Trauma to Face

Facial nerve may be injured in surgery of parotid tumours or deliberately excised in malignant tumours. Accidental injuries in the parotid region can also cause facial paralysis. Application of obstetrical forceps may also result in facial paralysis in the neonate due to pressure on the extratemporal part of nerve

D. NEOPLASMS

1. Intratemporal Neoplasms

Carcinoma of external or middle ear, glomus tumour, rhabdomyosarcoma and metastatic tumours of temporal bone, all result in facial paralysis. Facial nerve neuroma is treated by excision and nerve grafting. High resolution CT scan and gadolinium-enhanced MRI is very useful for facial nerve tumour
2. Tumours of Parotid

Facial paralysis with tumour of the parotid almost always implies malignancy

E. SYSTEMIC DISEASES AND FACIAL PARALYSIS

e.g diabetes, hypothyroidism, leukaemia, sarcoidosis, polyarteritis nodosa, Wegener's granulomatosis, leprosy, syphilis and demyelinating disease.
Topodiagnostic Tests for Lesions in Intratemporal Part


The following tests are useful in finding the site of lesion in paralysis of lower motor neuron.

1. Schirmer's test

2. Stapedial reflex

3. Taste test

4. Submandibular salivary flow test

HYPERKINETIC DISORDERS OF FACIAL NERVE

1. Hemifacial spasm

It is characterised by repeated, uncontrollable twitchings of facial muscles on one side . Microvascular decompression.
selective section of the branches of facial nerve in the parotid

Botulinum toxin has been used in the affected muscle by preventing release of acetylcholine.

2. Blepharospasm

Twitchings and spasms are limited to orbiculars oculi muscles on both sides. The eyes are closed due to muscle spasms causing functional blindness. The cause is uncertain.
It is treated by selective section of nerves supplying muscles around the eye on both sides.

Botulinum-A toxin injected into the periorbital muscles gives relief for 3-6 months. Injection can be repeated if necessary.

Tumours of External Ear

Of all the cases of ear carcinoma, 85% occur on the pinna, 10% in the external canal and 5% in the middle ear.

Pinna

External ear canal
Benign
Preauricular cyst or sinus
Sebaceous cyst
Dermoid cyst
Keloid
Haemangioma
Papilloma
Cutaneous horn
Keratoacanthoma
Neurofibroma
Malignant
Squamous cell carcinoma
Basal cell carcinoma
Melanoma
Benign
Osteoma
Exostosis
Ceruminoma
Sebaceous adenoma
Papilloma
Malignant
Squamous cell carcinoma
Basal cell carcinoma
Adenocarcinoma
Malignant ceruminoma
Melanoma


TUMOURS OF EXTERNAL AUDITORY CANAL

Benign Tumours

1. Osteoma

presents as a single, smooth, bony, hard, pedunculated tumour, often arising from the posterior wall of the osseous meatus, near its outer end. Treatment is surgical removal by fracturing through its pedicle or removal with a drill.

2. Exostoses

They are multiple and bilateral, often presenting as smooth, sessile, bony swellings in the deeper part of the meatus near the tympanic membrane. Exostosis is often seen in persons exposed to entry of cold water in the meatus as in divers and swimmers. Males are affected three times more than females.

Treatment. When small and asymptomatic, no treatment is necessary. Larger ones, which impair hearing or cause retention of wax and debris, may be removed with high speed drill to restore normal sized meatus. Exostoses may extend deeply and lie in close relation to the facial nerve. Therefore, use of gouge and hammer should be avoided.

3. Ceruminoma

4. Sebaceous adenoma

5. Papilloma

Malignant Tumours

1. Squamous cell carcinoma

Most often, it is seen in cases of long-standing ear discharge. It may arise primarily from the meatus or be a secondary extension from the middle ear carcinoma.

Presenting symptoms are: blood staining of mucopurulent or purulent discharge and severe earache.

Examination may show an ulcerated area in the meatus or a bleeding polypoid mass or granulations. Facial nerve may be paralysed because of local extension of disease through posterior meatal wall or its spread into the middle ear. Regional lymph nodes may be involved.

Treatment is en bloc wide surgical excision with post-operative radiation.

2. Basal cell and adenocarcinomas

3. Malignant ceruminoma

4. Malignant melanoma

Tumours of Middle Ear and Mastoid

Tumours of middle ear and mastoid can be divided into:

1. Primary Tumours

Benign: Glomus tumour
Malignant: Carcinoma, sarcoma

2. Secondary Tumours

(a) From adjacent areas, e.g. nasopharynx, external meatus and the parotid. (b) Metastatic, e.g. from carcinoma of bronchus, breast, kidney, thyroid, prostate and gastrointestinal tract
GLOMUS TUMOUR

It is the most common benign neoplasm of middle ear and is so-named because of its origin from the glomus bodies found in the dome of jugular bulb or on the promontory along the course of tympanic branch of IXth cranial nerve (Jacobson's nerve).

Clinical Features

The tumour is often seen in the middle age (40-50 years). Females are affected five times more.

Earliest symptoms are hearing loss and tinnitus. Hearing loss is conductive and slowly progressive. Tinnitus is pulsatile and can be temporarily stopped by carotid pressure.

Otoscopy

"Rising sun" appearance is seen when tumour arises from the floor of middle ear.


"Pulsation sign" (Brown's sign) is positive,

Dizziness or vertigo and facial paralysis may appear. Earache is less common than in carcinoma of the external and middle ear.

Otorrhoea may occur due to secondary infection and the condition may simulate chronic suppurative otitis media with polyp.

Audible bruit

Cranial nerve palsies(9-12 CN)

Some glomus tumours secrete catecholamines and produce symptoms like headache, sweating, palpitation, hypertension and anxiety.

Diagnosis

History and physical examination
Serum levels of catecholamines or their break-down products in urine (vanillylmandelic acid, metanephrine, etc.).

CT scan

MRI

Four-vessel angiography

Embolization

In large tumours, embolization of feeding vessels 1-2 days before operation.

Biopsy

Preoperative biopsy of the tumour for diagnosis is never done.

Treatment

It consists of:

1. Surgical removal.
2. Radiation.
3. Embolisation.
4. Combination of the above techniques.

Acoustic Neuroma

Acoustic neuroma is also known as vestibular schwannoma, neurilemmoma or eighth nerve tumour.
Incidence


Acoustic neuroma constitutes 80% of all cerebellopontine angle tumours and 10% of all the brain tumours

Pathology

It is a benign, encapsulated, extremely slow-growing tumour of the 8th nerve. Bilateral tumours are seen in patients with neurofibromatosis type 2

Clinical Features

1. Age and sex

Tumour is mostly seen 40-60 years. Both sexes are equally affected.

2. Cochleovestibular symptoms

Progressive unilateral sensorineural hearing loss, often accompanied by tinnitus, is the presenting symptom in majority of cases. There is marked difficulty in understanding speech. Some patients may get sudden hearing loss.

Vestibular symptoms are imbalance or unsteadiness.

3. Cranial nerve involvement

Vth nerve

VIIth nerve

IXth and Xth nerves. There is dysphagia and hoarseness

Other cranial nerves. XIth and XIIth, IIIrd, IVth and VIth are affected when tumour is very large.

4. Brainstem involvement

There is ataxia, weakness and numbness of the arms and legs with exaggerated tendon reflexes.

5. Cerebellar involvement

Pressure symptoms on cerebellum are seen in large tumours.

6. Raised intracranial pressure

This is also a late feature. There is headache, nausea, vomiting, diplopia due to VIth nerve involvement and papilloedema with blurring of vision.

Investigations and Diagnosis

1. Audiological tests


2. Stapedial reflex decay test

3. Vestibular tests

Caloric test will show diminished or absent response in 96% of patients.

4. Neurological tests

Fundus is examined for blurring of disc margins or papilloedema.

5. Radiological tests

(a) Plain X-rays.
(b) CT scan.
(c) MRI with gadolinium contrast. It is superior to CT scan and is the gold standard for diagnosis of acoustic neuroma.
(d) Vertebral angiography. This is helpful to differentiate acoustic neuroma from other tumours of cerebellopontine angle when doubt exists.

6. Evoked response audiometry (BERA)

It is very useful in the diagnosis of retrocochlear lesions.


Differential Diagnosis

Acoustic neuroma should be differentiated from the cochlear pathology (i.e. Meniere's disease) and other cerebellopontine angle tumours, e.g. meningioma, primary cholesteatoma and arachnoidal cyst.

Treatment

Surgery

Surgical removal of the tumour is the treatment of choice. Surgical approach will depend upon the size of tumour.

Gamma knife surgery.

Cyber knife.

Otalgia (Earache)

Pain in the ear can be due to causes occurring locally in the ear or referred to it from remote areas.
A. Local Causes

1. External ear

Furuncle, impacted wax, otitis externa, otomycosis, myringitis bullosa, herpes zoster, and malignant neoplasms.

2. Middle ear

Acute otitis media, eustachian tube obstruction, mastoiditis, extradural abscess, aero-otitis media, and carcinoma middle ear

B. Referred Causes

1. Via Vth cranial nerve

(a) Dental. Caries tooth, apical abscess, impacted molar, malocclusion.

(b) Oral cavity. Benign or malignant ulcerative lesions of oral cavity or tongue.

(c) Temporomandibular joint disorders. Bruxism, osteoarthritis, recurrent dislocation, ill-fitting denture.

(d) Sphenopalatine neuralgia.

2. Via IXth cranial nerve

(a) Oropharynx. Acute tonsillitis, peritonsillar abscess, tonsillectomy. Benign or malignant ulcers of soft palate, tonsil and its pillars.


(b) Base of tongue. Tuberculosis or malignancy.

(c) Elongated styloid process.

3. Via Xth cranial nerve

Malignancy or ulcerative lesion of: vallecula, epiglottis, larynx or laryngopharynx, oesophagus.

4. Via C2 and C3 spinal nerves

Cervical spondylosis, injuries of cervical spine, caries spine

C. Psychogenic Causes

When no cause has been discovered, pain may be functional in origin but the patient should be kept under observation with periodic re-evaluation.

Otalgia is a symptom. It is essential to find its cause before specific treatment can be instituted.
Tinnitus

Tinnitus is ringing sound or noise in the ear. The characteristic feature is that the origin of this sound is within the patient. Usually, it is unilateral but may also affect both ears. It may vary in pitch and loudness and has been variously described by the patient as roaring, hissing, swishing, rustling or clicking type of noise. Tinnitus is more annoying in quiet surroundings, particularly at night, when the masking effect of ambient noise from the environment is lost


Types of Tinnitus

Two types of tinnitus are described:

(a) Subjective, which can only be heard by the patient.
(b) Objective, which can even be heard by the examiner with the use of a stethoscope

A. Subjective

I. Otologic
Impacted wax
Fluid in the middle ear
Acute and chronic otitis media
Abnormally patent eustachian tube
Meniere's disease
Otosclerosis
Presbyacusis
Noise trauma
Ototoxic drugs
Tumours of VIIIth nerve
II. Non-otologic
Diseases of CNS
Anaemia
Arteriosclerosis
Hypertension
Hypotension
Hypoglycaemia
Epilepsy
Migraine
Drugs
B. Objective (usually pulsatile)
Vascular tumours of middle ear (glomus tumour)
Aneurysm of carotid artery
Palatal myoclonus
C. Psychogenic



Treatment

Where possible, its cause should be discovered and treated.

When no cause is found, management of tinnitus includes:
1. Reassurance and psychotherapy.
2. Techniques of relaxation and biofeedback.
3. Sedation and tranquillizers.(TCA) They may be needed in initial stages till patient has adjusted to the symptom.
4. Masking of tinnitus. Tinnitus is more annoying at bed time when the surroundings are quiet. Use of a fan, loudly clicking clock or a similar device may mask the tinnitus and help the patient to go to sleep. Use of a hearing aid, in persons with hearing loss, not only improves hearing but also provides a masking effect.

Tinnitus maskers can be used in patients who have no hearing loss. They are worn like a hearing aid.