PAIN is an unpleasant sensory/emotional experience associated with actual or potential tissue damage or described in terms of such damage

It is described by duration, site, distribution, type

1. Acute pain – sudden onset, obvious cause, identifiable pathology, responds to analgesics, and treatment of the pathology, associated with the emotions of fear and apprehension.

2. Chronic pain – insidious onset, no evident cause or readily identifiable pathology, responds poorly to analgesics, patient depressed

Physiology of pain:

• Nociceptive stimuli (inflammation, infection, trauma, chemicals, thermal stimulus, biochemical stimulus)
• Acts on peripheral pain receptors (non myelinated nerve fibres).
• The impulse transmitted in form of a chemical transmitter substance across the synaptic cleft & an electric potential along the neuron.
• Pain is perceived centrally causing peripheral release of endorphins (endogenous morphines)
• From small interneurons that block the presynaptic release of the chemical pain transmitter (substance P) = tolerance

Gate control theory of pain:

• Spinal gates at dorsal horn – at each segment of spinal cord
• Heat, touch and pain impulse compete for the gate – therefore non painful stimulus blocks transmission of noxious stimulus
• Modulated by substantia gelatinosa (SG) in the dorsal horn
• Which then influences the first central transmission cells (T cells)
• SG – modulating gate – permits only one type of impulse to pass through
• Larger nerves eg. touch receptors carry impulse to brain quicker and get through gate, blocking nociceptors
• Therefore use massage and heat therapy to inhibit pain sensation

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Causes of facial pain and headaches

1. Local causes:

• Dental or oral disease
• Referred pain
• Upper respiratory tract lesions
• Neck lesions
• Ocular lesions/ defective vision
• Trauma

2. Neurologic causes:

• Trigeminal neuralgia
• Glossopharyngeal neuralgia
• Herpetic neuralgia
• Intracranial disease

3. Psychogenic causes:

• Tension headaches
• Atypical facial pain
• Temporomandibular pain dysfunction syndrome

4. Vascular causes:

• Migraine
• Migranous neuralgia
• Temporal arteritis

5. Systemic causes:

• Severe hypertension
• Drugs (vinca alkaloids etc)

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Diagnostic features of conditions presenting with orofacial pain

Common diseases in this list need to be ruled out before diagnosis of rare conditions

1. Acute osteomyelitis:

• Causative lesion – carious tooth/PDL disease, and bone swelling
• Moth eaten appearance only manifests when approx 30% of bone undergoes osteolysis

2. Acute pulpitis:

• Sensitivity to temperature extremes and sugary foods
• ↑ pain at night or when lying down.
• Vitalometry – indicates that the pulp is still vital
• Percussion sensitivity – indicates apical spread

3. Apical abscess:

• Non vital tooth with fistula, parulis or extra oral drainage tracts
• This may be acute (with febrile presentation) or chronic

4. Cracked tooth syndrome:

• Apico-occlusal crack which does not show up on x-ray
• Pain on mastication
• Lateral pressure on the inclines of the cusp causes pain

5. Cluster headaches:

• Seasonal headaches with acute episodes in the evenings + ipsilateral conjunctival
  reddening and nasal discharge

6. Internal derangement of TMJ meniscus/ capsule adhesions

7. Myalgia of masticatory muscles:

• Pain and spasm of muscles of mastication – marked by a trigger point on one or more of these muscles (masseter, medial and lateral pterygoids, temporalis)
• Usually found in patients with a history of jaw clenching on anxiety

8. Otitis media:

• Unilateral hearing impairment and bulging, perforated, red or purulent tympanic membrane

9. PDL abscess:

• Expression of pus from the PDL pocket of a vital tooth
• Characterized by presence of calculus and alveolar bone damage
• If the tooth is non vital, it’s a perio-endo lesion

10. TMJ capsulitis/ synovitis/ arthritis:

• Pain over the joint
• Limited mouth opening or deviation on opening
• Crepitus on palpation of the TMJ – indicates bone erosions – secondary to arthritis

11. Neuralgia (Trigeminal, Glossopharyngeal or Postherpetic):

• Pain of neural origin, paroxysmal pain
• Distinct trigger zone on skin/ in mouth
• Middle aged or old patients, female patients
• Trigeminal neuralgia is called ‘Tic Doloureux’ when it is accompanied by spasms of the muscles of facial expression

Classical trigeminal neuralgia:

• Sudden unilateral, severe, brief, stabbing, recurrent pains in the distribution of trigeminal nerve branches
• Pain is paroxymal
• Provoked by light touch
• Confined to trigeminal distribution
• Unilateral
• Lasts from few seconds to 2 minutes
• Etiology: Intracranial compression of nerve by vasculature/foramina (osteopetrosis)
• Diagnosis: History, CT scan, MRI, LA during an attack attenuates the pain instantly
• Management: Carbamazepine, cryotherapy, vascular decompression

12. Atypical facial pain:

• No known organic cause (diagnosis of exclusion)
• Described by the patient in vague terms, treated as a symptom of depressive illness
• It is also called psychogenic pain

13. Myofascial pain dysfunction syndrome (MPDS)

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The diagnostic protocol for acute facial pain

Is the contributing lesion clinically visible (intra- and extra-oral examination for caries, PDL
disease, swellings, erosions, joint sounds, radiographic changes)?

If YES:
− Is it accompanied by fever (a sign of acute disease)?

If YES:
− Pulp or PDL: Abscess or osteomyelitis
− Mucosal lesions: Viral vesiculo-ulceration
− Facial swelling: Cellulitis or space infection
− Salivary swelling: Mumps or obstructive sialadenitis
− TMJ or mid ear: Infectious capsulitis or otitis media

If NO:

1. Dull or episodic aches:

2. Constant ache:

• Teeth or jaws:
  − Atypical facial pain
  − Myalgia of muscles of mastication
• TMJ: Temporomandibular myalgia

3. Acute episodic ache:

• Short term (seconds): Trigeminal neuralgia
• Long term (minutes): Cluster headaches

NB: Manage pain and re-evaluate in 1 wk to eliminate an organic source eg cracked tooth

4. Chronic episodic ache:

• Teeth or jaws:
  − Atypical facial pain
  − Myalgia of muscles of mastication
  − Cardiogenic (one of the signs of hypertension)
  − Vasogenic (migraine)
• TMJ: Myalgia

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Facial paralysis

UMN lesion: Lesion of the neural pathway above the anterior horn cell of spinal cord, or motor nuclei of the cranial nerves

LMN lesion: Affects nerve fibers traveling from anterior horn of spinal cord or cranial motor nuclei to the relevant muscles

1. Bell’s palsy: Picture

• LMN paralysis of the face – due to inflammation in the stylomastoid canal
• Reversible in 80% of cases
• Management: Corticosteroid therapy

2. Ramsay Hunt syndrome:

• Severe facial palsy – due to herpes zoster infection of the geniculate ganglion of the facial nerve
• In hereditary craniofacial malformation

3. Tardive dyskinesia: Picture

• Complication of longterm treatment with phenothiazines or butyrophenones
• Clinical: Involuntary facial movements

4. Horner’s syndrome: Picture

• A series of signs and symptoms – secondary to trauma to the cervical sympathetic trunk
• Clinical: Miosis (papillary constriction), ptosis (drooping eyelids), facial anhidrosis (loss of sweating) and occasionally enophthalmos

5. Adie’s pupil: Unilateral dilatation + very slow light reflex – due to syphilis. Picture

6. Argyll-Robertson pupil: Picture

• Failure of light reflex, but dilation for accommodation.
• Also seen in neurosyphillis + other conditions affecting the Edinger Westphal nucleus eg diabetes mellitus, sarcoidosis, encephalopathies, midbrain tumors, trauma and amyloidosis