ORAL MEDICI ne Dr. Ali Al-Ibrahemy

OROFACIAL NEURALGIES AND NEUROPATHIC PAIN

Pain is the most common symptom for which patients seek help.

Approximately 40% of the British population only visit a dentist for pain relief.

Emotional disturbance itself can also produce the symptom of physical pain. The International Association for the Study of Pain's widely used definition

states: "Pain is an unpleasant sensory and emotional experience associated with

actual or potential tissue damage, or described in terms of such damage."

There are many causes of oral or maxillofacial pain. Pulpitis and

periapical periodontitis as sequels of dental caries are by far the most common

causes. The source of such pain is usually obvious on examination but some

sources of dental pain can be exceedingly difficult to identify. Disease of the

teeth (usually the result of dental caries) and adjacent tissues must always be

excluded in the investigation of pain. The most causes of pain felt in the oral

tissues are illustrated blew:-

1- Diseases of teeth and/or supporting tissues 2- Oral mucosal diseases3- Diseases of the jaw4- Pain in the edentulous patient5- Postoperative pain6- Pain triggered by mastication7- Referred pain8- Neurological diseases9- Psychogenic (atypical) facial pain

1- Diseases of teeth and/or supporting tissuesThere are many sources of pain felt in the oral cavity which are:-

Pulpitis Dentine hypersensitivity, cracked tooth or cracked cusp syndrome Periapical periodontitis

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Lateral (periodontal) abscess Acute necrotising ulcerative gingivitis HIV-associated periodontitis Pericoronitis

Pulpitis is usually the cause when hot or cold food or drinks trigger the

pain. It is also the main cause of spasmodic, poorly localised attacks of pain

which may be mistaken for a variety of other possible causes. The pain of acute

pulpitis is of a sharp lancinating character peculiar to itself, impossible to

describe but unforgettable once experienced.

Pain from acute periapical periodontitis should be readily identifiable as

there is precisely localised tenderness of the tooth in its socket. Radiographs are

of little value in the early stages but useful after sufficient destruction shows

itself as loss of definition of the periapical lamina dura, so after one week the

early sign is appear by widening of the periodontal space. In other cases, acute

inflammation may supervene on chronic, and a rounded area of radiolucency is

seen. Acute maxillary sinusitis can rarely cause similar tenderness of a group of

teeth, particularly upper molars.

In lateral periodontal cyst, the tooth is tender in its socket, but is usually

vital and there is deep localised pocketing. Occasionally both a periodontal and

periapical abscess may form together on a non-vital tooth with severe

periodontal disease, or a periodontal abscess may be precipitated by endodontic

treatment when a reamer perforates the side of the root.

The acute necrotising ulcerative gingivitis and HIV-associated necrotising

periodontitis can cause acute ulcerative gingivitis usually causes soreness, but

when it extends deeply and rapidly, destroying the underlying bone, there may

be severe aching pain. In such cases the diagnosis is usually obvious clinically.

HIV-associated periodontitis presents a somewhat similar picture and is acutely

painful.

2- Oral mucosal diseases

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Ulcers generally cause soreness rather than pain, but deep ulceration may

cause severe aching pain. Carcinoma in particular causes severe pain once nerve

fibers become involved. It is important to emphasize again that early carcinoma

is painless; pain is a late symptom. By the time that pain becomes troublesome

the tumors is usually easily seen unless it is far back in the mouth. Herpes zoster

causes severe aching pain, sometimes indistinguishable from toothache, because

of involvement of cervical ganglia

3- Diseases of the jawThe important feature of these conditions is that, as well as the history and

clinical presentation, the provisional diagnosis depends on the radiographic

findings. Fractures and osteomyelitis should be recognizable by such means.

Other lesions of the jaws, by contrast, sometimes have less clear cut clinical and

radiographic features, and the differentiation of an infected cyst from a

malignant tumour may be difficult, with the exception of fractures and

osteomyelitis, diagnosis then depends on biopsy and histological examination.

There are many conditions that caused painful jaws diseases which are:-

Fractures Osteomyelitis Infected cysts Malignant neoplasms Sickle cell infarcts

4- Pain in the edentulous patientThese conditions differ from most others because dental causes can be

excluded. The chief difficulty is to decide whether the pain is due to the dentures

themselves, or to some condition of the mucosa or jaws on which a denture is

pressing. Some of problems can illustrate under this condition which are:-

Denture trauma (such as traumatic ulcers) Excessive vertical dimension (such as TMJ dysfunction syndrome) Diseases of the denture-bearing mucosa (such as denture induced

candidiasis) Diseases of the jaws (such as residual cyst) Teeth or roots erupting under a denture

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5- Postoperative painImportant causes are summarised in table below. By far the most common

cause of pain after dental extractions is alveolar osteitis (dry socket), which can

usually be recognised on clinical examination. Fracture of the jaw following

operative treatment is rare but can also be recognised from the history, and by

clinical and radiographic examination. Forcible opening of the mouth under

general anaesthesia, particularly for removing wisdom teeth, can damage the

temporomandibular joint and lead to persistent pain on opening or during

mastication. Postoperative osteomyelitis should be a thing of the past but could

develop in an immunedeficient patient with, for example, unrecognised

leukaemia. Persistent postoperative pain is sometimes ascribed to damage to

nerve fibers either as a result of operative trauma or by involvement in scar

tissue. However, if there is no objective evidence of disturbed sensation there is

little or nothing abnormal to be found. Operative intervention in the attempt to

relieve such pain may do more harm than good. In some such cases there is

complaint of persistent pain unresponsive to treatment but without any organic

cause. Rarely damaged nerve tissue may proliferate to form a traumatic

neuroma, which is tender to pressure. The causes of postoperative pain are:-

Alveolar osteitis (dry socket). Fracture of the jaw. Damage to the temporomandibular joint. Osteomyelitis. Damage to nerve trunks or involvement of nerves in scar tissue.

6- Pain triggered by masticationThe common dental cause for pain on mastication is apical periodontitis,

but any conditions which causes the tooth to be tender in its socket, whether it

be a lateral periodontal abscess or, occasionally, maxillary sinusitis, can cause

this symptom. The main causes of pain induced by mastication are:-

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Diseases of teeth and supporting tissues Myofascial pain dysfunction syndrome Diseases of the temporomandibular joint Trigeminal neuralgia (rarely) Salivary calculi

7- Pain from extraoral diseases (referred pain)

Antral disease can cause pain felt in the upper teeth but a sinus

radiograph should provide the diagnosis. Salivary gland and ear diseases

typically cause preauricular pain. They may simulate temporomandibular joint

symptoms but are rarely mistaken for dental problems. Acute sinusitis is the

most common paranasal disease that causes facial pain but antral carcinoma is

rare. Mumps is a common cause of pain from, and swelling of, the parotid

glands. Suppurative parotitis is uncommon but may be a complication of dry

mouth. Acute parotitis may therefore be seen as a complication of Sjogren's

syndrome or irradiation damage to the glands. Sjogren's syndrome itself can

occasionally cause parotid pain and swelling of the glands. Swelling rather than

pain is usually the first symptom of malignant tumours of salivary glands.

Parotid gland tumours can also cause facial palsy and, finally, ulceration and

fungation. Myocardial infarction usually causes constricting or crushing pain

substernally, but pain may radiate down the inside of the left arm or up into the

neck or jaw. Rarely, cardiac pain is felt in the jaw alone.

8- Neurological diseasesThe most important one is the trigeminal neuralgia, and the reminder

intracranial neurological disorders are:-

o Trigeminal neuralgia

o Glossopharyngeal neuralgia

o Multiple sclerosis

o Herpes zoster

o Postherpetic neuralgia

o Migrainous neuralgia

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o Intracranial tumours

o Bell's palsy

Trigeminal neuralgiaThe typical features are elderly patients are affected, and though the pain

is excruciatingly severe, there is complete, or almost complete, relief between

spasms. During an attack the patient's face is often distorted with anguish, while

between attacks the patient may appear apprehensive at the thought of

recurrence. The severity of the pain may also make the patient depressed. The

pain is paroxysmal, i.e. severe, sharp and stabbing in character, but lasts only

seconds or minutes and may be described as like lightning. However, attacks

may sometimes be quickly recurrent at short intervals. Stimuli to an area

(trigger zone) within the distribution of the trigeminal nerve can provoke an

attack. Common stimuli are touching, draughts of cold air, or teeth brushing.

Occasionally, masticatory effort induces the pain. There are no objective signs.

Either the second or third division of the trigeminal nerve is usually first

affected, but pain soon involves both. The first division is rarely affected and

pain does not spread to the opposite side.

Diagnosis, should be readily made from the features described, with the

absence of objective sensory loss and absence of any detectable organic cause. A

careful search should be made for diseased teeth, though pain of this severity is

unlikely to be due to dental disease. An inflamed pulp can cause stabs of severe

pain in its early stages, but the pain changes in character and soon becomes

more prolonged. Any diseased teeth should of course be treated, though this

does not affect the neuralgia. In the absence of disease, teeth should not be

arbitrarily extracted, as this only adds to the patient's misfortunes.

TreatmentThe most effective drugs are anticonvulsants, particularly carbamazepine

and to a lesser extent phenytoin. Carbamazepine, with or without phenytoin,

will usually relieve the pain, at least for a time. Abolition of the pain of

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trigeminal neuralgia by giving an anticonvulsant, such as carbamazepine, also

helps to confirm the diagnosis. Carbamazepine ( l00mg/day gradually raised if

necessary to 800mg/day ), must be given long-term (essentially prophylactically)

to reduce the frequency and severity of attacks. Up to 80% of patients are

relieved of pain partly or completely by carbamazepine, but minor side-effects are

common, such as drowsiness, dryness of the mouth, giddiness, diarrhoea, and

nausea are all to some extent dose-related. A few patients are unresponsive to

carbamazepine or cannot tolerate the side-effects. If drug treatment fails, the final

resort is surgery. The simplest option is cryotherapy to the trigeminal nerve or, if

this fails, cryotherapy at the base of the skull. If these fail, microvascular

decompression of the trigeminal ganglion may be required.

Glossopharyngeal neuralgiaThis rare condition is characterised by pain similar to that of trigeminal

neuralgia but felt in the base of the tongue and faces on one side. It may also

radiate deeply into the ear. The pain, which is sharp, lancinating and transient,

is typically triggered by swallowing, chewing, or coughing. It may be so severe

that patients may be terrified to swallow their saliva and try to keep the mouth

and tongue as completely immobile as possible. Glossopharyngeal neuralgia

sometimes responds to carbamazepine, but less often than trigeminal neuralgia.

Once an organic cause has been excluded, surgical treatment may be needed.

However, like trigeminal neuralgia, there can be spontaneous remissions,

sometimes for years.

Paraesthesia and Dysaesthesia of the lipParaesthesia of the lip can be caused by osteomyelitis or fracture of the

jaw. Very occasionally it results from neurological disease. Prolonged

anaesthesia or paraesthesia of the lip can occasionally follow inferior dental

blocks, possibly as a result of damage to the nerve by the needle. Spontaneous

recovery usually takes place. Paraesthesia of the lip can be a complication of

fractures of the mandible where the nerve has become stretched, particularly 7

over the sharp edge of the canal. The effect is temporary but complete recovery

may take some months. The inferior dental nerve may occasionally be damaged

in operations on the mandible and there may be anaesthesia or paraesthesia

lasting for many months. Complete loss of sensation is unusual but recovery may

take a year or more. The inferior dental nerve is rarely involved in osteomyelitis

but, with effective treatment, recovery is the rule. Alternatively it may be

compressed by a neoplasm or a tumour may infiltrate the nerve sheath. A jaw

tumour causing pain or paraesthesia strongly suggests malignancy. In such

cases, the prognosis is poor either because the tumour may be a secondary

carcinoma or a primary but highly malignant tumour such as an osteosarcoma.

The mental foramen can become exposed by excessive resorption of mandibular

bone in an edentulous patient. The denture can then press upon the nerve as it

leaves the foramen. Though these changes are common, they rarely cause

paraesthesia of the lip.

Herpes zoster affecting the trigeminal nerve can leave residual

disturbances of sensation. The most severe and troublesome is postherpetic

neuralgia but in other patients there may be persistent paraesthesia of the lip.

Disturbances of sensation of the face and other regions can be caused by multiple

sclerosis. Tetany is the result of hypocalcaemic states and causes heightened

neuromuscular excitability together with minor disorders of sensation such as

paraesthesia of the lip. A significant cause of tetany is over-breathing, usually

due to anxiety (hyperventilation syndrome).

Facial PalsyImportant causes of facial palsy, which include both upper and lower motor

neurone lesions, are summarised below :-

Extracranial causes :- Bell's palsy Malignant parotid neoplasms Parotid surgery Sarcoidosis (Heerfordt's syndrome) Misplaced local anaesthetic Melkersson-Rosenthal syndrome

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Intracranial causes :- Strokes Cerebral tumours and other neurological diseases Multiple sclerosis HIV infection Lyme disease Ramsay Hunt syndrome Trauma to the base of the skull

Bell's palsyBell's palsy is a common cause of facial paralysis. It probably results from

compression of the facial nerve in its canal as a result of inflammation and

swelling. A viral infection, particularly herpes simplex, is suspected as the cause.

Either sex may be affected, usually between the ages of 20 and 50. As mentioned

earlier, pain in the jaw sometimes precedes the paralysis or there may be

numbness in the side of the tongue. Though this disease is uncommon in dental

practice, its recognition is important as early treatment may prevent permanent

disability and disfigurement. Function of the facial nerve is tested by asking the

patient to perform facial movements. When asked to close the eyes, the lids on

the affected side cannot be brought together but the eyeball rolls up normally,

since the oculomotor nerves are unaffected. When the patient is asked to smile,

the corner of the mouth on the affected side is not pulled upwards and the

normal lines of expression are absent. The wrinkling round the eyes which

accompanies smiling is also not seen on the affected side and the eye remains

staring. This is a lower motor neurone lesion unlike the upper motor neurone

lesion seen, for example, after a stroke.

The majority of patients recover fully or partially without treatment. At

least 10% of patients with Bell's palsy are unhappy about the final outcome

because of permanent disfigurement or other complications. A guide to the need

for treatment is the severity of the paralysis when first seen. Full recovery is

usual in patients with an incomplete palsy seen within a week of onset, but more

than half of those with a complete lesion fail to recover completely.

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Electromyography and other electrodiagnostic techniques can be used to

measure the degree of functional impairment as a guide to the need for

treatment. Prednisolone, by mouth (20 mg four times a day) may be given for 5-

10 days and then tapered off over the following 4 days, and may be effective if

given within 24 hours of the onset. The addition of acyclovir appears to produce

more reliable results and also suggests a role for a herpes virus.

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