Orofacial Pain

By Dr.Anura Ariyawardana

 

Introduction    

     International Association for the Study of Pain has declared that “relief of pain should be a human right”. Pain contributes to a significant proportion of human suffering. Clinicians encounter pain patients in their day to day practice and they are often called upon for prompt action in pain relief.

     Orofacial pain (OFP) possesses unique characteristics and contributes for a significant proportion of all pain problems that a human being could encounter. Moreover, OFP has a significant adverse impact on quality of life. Anatomically the oro-facial structures are complex and hence there are many sources that may produce pain. As a result many pain problems mimic each other making the diagnosis difficult. In addition, many referral pain patterns also exist in the orofacial region making the diagnosis further difficult. The success of treatment is based on the accuracy of diagnosis. Hence, the clinicians should possess sound knowledge and sufficient skills to analyze pain to arrive at the diagnosis based on which appropriate treatment plan in overall management of a patient complaining of pain is determined.

 

Diagnostic classification

     An important concept for clinicians to understand is that the clinical characteristics of pain can be useful in identifying the tissues or structures that are responsible for the pain. A classification therefore will be based on the structures that are responsible in producing pain. However, certain pain conditions could be caused due to or influenced by psychological factors which may not be sorted out by observing the physical abnormalities. Therefore, in order to classify pain disorder the clinician must consider both somatosensory and psychological inputs.

     In other words, a complete pain classification must assess the pain condition on two levels of axes.  Axis I depicts the physical causes whereas II depicts psychological factors. Although more acute physical conditions are falling under axis I, some chronic pain conditions may be influenced by the axis II factors as well.

     Axis I disorders could either be acute or chronic. In the majority of acute pain conditions a physical abnormality is obvious to find and hence easy to diagnose and treat.   However, in most of the chronic pain condition no obvious physical abnormality can be detected. Chronic pain disorders could also be associated with axis II factors. Therefore, any management directed only addressing the physical factors is more likely to be unsuccessful.

 

Site vs source of pain

     It is a very important concept for a clinician to understand the difference between the site of pain and the source of pain. “Site” of pain is the anatomical location where the patient feels pain, where as “source” is the actual origin of pain. When the site and the source of pain are identical, it is quite easy to diagnose and manage. However, particularly in the orofacial region the site and the source may be non-identical. This may be due to the complexity of the pain referral pattern in the oro-facial region. If any treatment is directed towards the “site” of pain, it often fails even leading to irreversible tissue loss such as tooth extraction. Therefore clinicians must be very clear of the origin of pain before embarking on any irreversible treatment options.

 

Table 02. Orofacial pain conditions

 

Clinical characteristics of different types of oro-facial pain

 

Superficial somatic pains

Pain is a bright, stimulating sensation that is precisely located by the patient.

Respond to provocation is faithful in location, duration and intensity.

Pain is necessarily “clear cut” with no central excitatory effects.

Pain can be arrested by local anesthesia at the site.

Deep somatic pains

Pain is dull, depressing and less precisely located by the patient.

Respond to provocation is less faithful as to location and intensity.

Pain frequently exhibits CNS excitatory effects.

Pain is arrested by blocking the source of the pain.

Musculoskeletal pain

Pain is intimately related to biomechanical function.

Respond to provocation is proportionate to the stimulus.

Visceral pain

Pain is irrelevant to biomechanical function.

Pain is non-responsive to provocation until the threshold is reached.

Neuropathic pain

Burning type of pain that is spontaneous or triggered and ongoing and unremitting

Pain occurs disproportionate to the stimulus

Pain may be accompanied by other neurologic signs

No evidence of tissue damage

Pain may be initiated or maintained by sympathetic nervous system

Episodic Neuropathic pain

Quick, sharp, electric type pain

Very intense debilitating pain

Duration is momentary

Very little pain between attacks

Pain follows the distribution of the affected nerve

Continuous neuropathic pain

Dull or burning quality

Pain is ongoing, unremitting and intensity can show pattern of fluctuation

Pain may be accompanied by other neurological signs (anesthesia, paresthesia)

No evidence of tissue damage

 

Diagnosis of oro-facial pain

     For the diagnosis of any pain condition, it is mandatory to obtain a thorough pain history. It is imperative for the clinician to be patient enough to listen to the pain history carefully especially in assessing a chronic oro-facial pain problem. Pain intensity assessment using a reliable tool such as visual analogue scale is of utmost importance. Moreover, details of psycho-social history also play a pivotal role. Insight into the previous treatments is also mandatory.

 

Physical examination

     Clinicians who intend to treat oro-facial pain should have a thorough understanding of the complex regional gross and neuro-anatomy, neurophysiology and behavior and function of the loco-regional structures. Oral soft tissues and hard tissues should be thoroughly assessed for structural and functional abnormalities. Inter-incisal mouth opening, mobility of the structures should be assessed. In addition, it is of utmost important to carry out examination of the muscles of mastication and the neck muscles. Clinicians should carry out neurological examination for sensory and motor abnormalities too.

 

Special investigations

     In the diagnosis of oro-facial pain, special investigations play a significant role though they all are secondary to history and physical examination. The most important of all investigations is the radiological investigation. Periapical, bitewing or occlusal radiographs are most frequently taken. However where necessary, clinicians should order dental panoramic tomogram or other extra-oral skull radiographs. More sophisticated techniques are also available such as cone beam CT, Contrast radiography, ultrasound and MRI. The clinicians should choose the most appropriate method. More importantly, the clinicians should possess knowledge and skills in interpreting the results. It is of utmost importance to keep in mind that the radiological investigations can be used only to exclude or to confirm the diagnosis but not to arrive at.

     In addition, vitality testing of relevant teeth is also important. In certain occasions, local anesthetic injections can be used to determine the origin of pain in cases where referred pain is considered.

 

Interpretation of findings and confirmation: An overview

     All the findings should be analyzed rationally to negate or confirm the diagnosis. This particularly depends upon the clinician’s knowledge, skills and experience. Relevant diagnostic criteria should be considered in interpreting the findings. The readers are expected to read diagnostic criteria of the American Academy of Orofacial pain, International headache society and Research diagnostic criteria for Temporomandibular disorders.

 

Principles of management

     The success of the management depends on the proper diagnosis. History plays a key role in the diagnosis and special investigations particularly radiological findings are used either to negate or to confirm the diagnosis.  Similarly contributing factors both precipitating and perpetuating must be identified. Except in absolute indications conservative approach should be chosen in as the fist line approach particularly in chronic orofacial pain problems. Major conservative approaches include: patient education, pharmacotherapy, rest and relaxation, cognitive behavioral intervention, physical therapy, orthopedic appliances, and Management of trigger points.

     Patients should be educated about their pain problem especially in chronic orofacial pain conditions. It is important to explain the treatment options available and the appropriate option should be chosen carefully. In managing patients, one should not consider “one diagnosis one treatment approach”. Pharmacotherapy includes: analgesics (NSAID/opioid analgesics), anxiolytics (benzodiazepines), muscle relaxants (cyclobenzaprine/diazepam), low dose antidepressants (amitriptyline, SSRIs), antiepileptics (carbamazepine, oxcarbazepine, phenytoin, valproate, divalproex, gabapentin, toperamate), corticosteroids and other drugs (baclofen).

      In most of the chronic orofacial pain conditions it may be evident that some patients are indulged with certain behavioral problems such as adverse habits. As such it is important to consider cognitive and behavioral intervention. Certain simple adverse habits can be reversed by explanation. However some habit may need professional attention considering more advanced approaches.

     Application of moist heat, soft laser, ultrasound and infra red therapy also has been used especially in musculoskeletal problems such as myofascial pain. Use of occlusal appliances may be indicated for some painful temporomandibular disorders. However, there is no promising evidence through randomized controlled trials regarding the success of such treatment modalities. Therefore, individual patients should be assessed separately and apply the most appropriate method available for the management.

     Physical therapy including muscle stretching exercises is also indicated in musculoskeletal pain problems. It is useful to apply moist heat or vapo-coolant application prior to application of such exercises. Such methods are particularly useful in pain conditions with dysfunction.

      Trigger point injections are used to eliminate trigger points in painful myofascial conditions. Injection could be either with local anesthetic without a vasoconstrictor. This may be done as an adjunctive to the other more conservative approaches.

 

Summary

     Oro-facial pain poses significant problems to the sufferer as well as to the clinician. It is of utmost importance to arrive at the accurate diagnosis to prevent treatment failure. Chronic orofacial pain conditions are difficult to manage and hence the clinician should take more precautions in arriving at the diagnosis. Proper selection of the most appropriate treatment modality is vital for the success. Clinicians should pay particular attention to the history taking and carful clinical evaluation of the condition. In chronic pain cases conservative modalities should be considered as the first line of treatment. Where appropriate, general practitioners should consider specialist referral for further management and specialized care.

 

References

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Fricton J. Myogenous temporomandibular disorders: Diagnostic and management considerations. Dent Clin N Am 2007; 51: 61-83.

Headache Classification Subcommittee of the International Headache Society. The international classification of headache disorders; 2nd ed. Cephalalgia.2004; 24 (suppl 1) 9-160.

Okeson J P. Bell's Orofacial Pains: The Clinical Management Of Orofacial Pain. 6th ed Quintessence 2004.

Okeson J P. Orofacial Pain: Guidelines for Assessment, Diagnosis, and Management. 1st ed Quintessence  1996.

Okeson J P. The classification of orofacial pains. Oral Maxillofac Surf Clin N Am 2008; 20: 133-144.

Zakrzewska J M, Harrison  SD (Editors). Assessment and Management of Orofacial Pain. 1st ed Elsevier, 2002.