Key Classifications of Pain

Key Classifications of Pain

• Pain can be classified temporally, mechanistically, and regionally.

Temporal Classification

• Acute pain lasts for less than 3 months.
• Acute pain can result from injury combined with unresolved tissue healing.
• Arthritis and fibromyalgia are examples of conditions causing acute pain.

Mechanistic Classification

• Nociceptive pain is a healthy feeling pain caused by tissue damage.
• Nociceptive pain responds to NSAIDs and opioids and examples are acute injury and post-surgical pain.
• Inflammatory pain is a healthy pain that is associated with tissue inflammation.
• Inflammatory pain is often short-lived, unless related to chronic conditions, such as rheumatoid arthritis or infections.
• Neuropathic pain results from lesions or diseases affecting the somatosensory nervous system.
• Neuropathic pain responds poorly to traditional painkillers, but may improve with neuroactive drugs.
• Trigeminal neuralgia and diabetic neuropathy are examples of neuropathic pain conditions.
• Nociplastic pain is dysfunctional central pain without clear damage or inflammation.
• Fibromyalgia and irritable bowel syndrome are examples of nociplastic pain conditions.

Regional Classification

• Orofacial pain is unique due to the complex anatomy of the head, face, and neck.
• Orofacial pain involves the trigeminal nerve, which is responsible for sensory input from the face.
• Acute orofacial pain is a protective reflex that stops us damaging ourselves.
• Increased sensitivity from swelling helps remind us to protect the region from unnecessary movement and further trauma, thereby helping maximise healing capacity.
• Chronic orofacial pain is largely due to subtle changes in the peripheral and central nervous system, meaning pain-sensing nerves (nociceptors) process normal and painful information differently.
• Headaches, temporomandibular joint disorders (TMDs), and dental pain are examples of orofacial pain conditions.

Orofacial Pain: Unique Characteristics

• The orofacial region contains vital structures, including the eyes, mouth, ears, nose, and brain.
• Functions such as breathing, eating, speaking, sleeping, and communication all occur in the orofacial region.
• Damage to the orofacial region can lead to severe psychological and physiological consequences.
• Loss of social function and identity can occur as a result of orofacial pain.
• Chronic orofacial pain can be debilitating, causing emotional distress and social isolation.

International Classification of Orofacial Pain (ICOP) 2020

• ICOP 2020 provides a structured classification for both acute and chronic orofacial pain.
• Seven pain categories exist within ICOP 2020.
• Nociceptive pain includes pulpitis, gingival pain, and mucosal pain.
• Myogenous pain is muscle-based pain, such as temporalis and masseter involvement.
• Articular pain is joint pain, such as TMJ disorders.
• Neuropathic pain includes trigeminal neuralgia and post-traumatic neuropathy.
• Neurovascular pain includes headache-related facial pain, such as migraines and cluster headaches.
• Nociplastic pain is chronic, non-specific pain, such as burning mouth syndrome.
• Psychological aspects highlights the impact of psychosocial factors.

Acute Orofacial Pain

• Dental pain is the most common type of acute orofacial pain.
• Dental pain progresses through reversible pulpitis to irreversible pulpitis and abscess formation.
• Misdiagnosis of dental pain can lead to unnecessary treatments.
• Protective pain alerts the brain to potential harm.
• Cold allodynia and mechanical allodynia from cracked teeth or exposed dentine are examples of protective pain.

Chronic Orofacial Pain

• Burning Mouth Syndrome (BMS) has a spontaneous onset in women >50 years.
• Symptons of BMS: Burning pain in the tongue, lips, or mucosa with no visible cause.
• BMS is often linked to psychological factors and systemic issues, e.g., menopause or diabetes.
• Persistent Idiopathic Facial Pain (PIFP) is chronic pain that lasts for >6 months.
• PIFP is non-responsive to treatments and is not confined to anatomical boundaries.
• PIFP is often associated with psychosocial stressors.
• PIFP is constant and lasts greater than 6 months.
• PIFP is "pain all the time resistant to interventions usually greater than 3 years."

Neuropathic Pain in Orofacial Region

• Trigeminal Neuralgia involves sudden, unilateral pain in the distribution of the trigeminal nerve (V2/V3 regions).
• Trigeminal Neuralgia triggers: Brushing teeth, shaving, talking, or eating.
• Trigeminal Neuralgia pain lasts for seconds, and can have periods of being pain free.
• Associated Trigeminal Neuralgia factors: trigger areas and weight loss.
• Trigeminal Neuralgia is managed with Carbamazepine or surgical options for refractory cases.
• Secondary TN is caused by multiple sclerosis, stroke, vasculitis etc.
• Idiopathic TN is not secondary and has No NVC.
• Post-Traumatic Neuropathic Pain (PTNP) is caused by dental procedures like third molar surgery, implants, or endodontics.
• Burning pain, allodynia (pain from normally non-painful stimuli, like light touch), and altered sensation are features of PTNP.
• Prompt intervention for nerve injuries is required to improve PTNP outcomes.
• Post-Herpetic Neuralgia is persistent pain after herpes zoster infection (shingles).
• Post-Herpetic Neuralgia is common in elderly or immunocompromised patients.
• In trigeminal system Post-Herpetic Neuralgia is most commonly V1 and V2.
• Early treatment for Post-Herpetic Neuralgia involves high-dose antifungals: acyclovir and prednisone.

Features of Neuropathic Pain

• Multiple injuries or episodes of infection and pain.
• Non-responsive to anti-inflammatory pain killers (NSAIDs and Paracetamol).
• Pain is better in the mornings but worsens during the day.
• Pain does not disturb sleep.
• Pain presentation consists of constant burning, elicited neuralgic, or a combination of the two.
• Pain worsens with stress, tiredness, and illness.

Neurovascular Pain

• Migraine presents as unilateral, throbbing pain often associated with aura, nausea, and photophobia.
• Cluster headaches present as severe, episodic pain around the eye or temple.
• Cluster headaches are more common in males and often misdiagnosed as toothache.
• Tension-Type Headaches present as bilateral, dull pain with possible links to medication overuse.

Pain Mechanisms in Dentistry

• Toothache mimics neuralgia when involving dentine or pulp exposure.
• TMJ Disorders include myogenous and arthralgia-related pain.
• TMJ Disorders may mimic migraines or cluster headaches.

Psychological and Psychosocial Factors

Axis I: Physical Conditions

• Axis I focuses on physical conditions responsible for initiating nociceptive impulses.
• These conditions are classified based on the specific orofacial structures involved in generating pain.
• Cutaneous and Mucogingival Pains originate from the skin and gingival (gum) tissues.
• Gingivitis, localized infections, and trauma to gingival tissues are examples of Cutaneous and Mucogingival Pains.
• Mucosal Pains of the Pharynx, Nose, and Paranasal Sinuses are linked to mucosal tissues in the upper respiratory tract.
• Sinusitis, pharyngitis, and nasal infections are examples of Mucosal Pains of the Pharynx, Nose, and Paranasal Sinuses.
• Pains of Dental Origin are caused by dental structures.
• Pulpitis, periapical abscess, and cracked tooth syndrome are examples of Pains of Dental Origin.
• Pains of the Musculoskeletal Structures of the Mouth and Face involve muscles, joints, and related tissues.
• Temporomandibular joint disorders (TMD) and myofascial pain are examples of Pains of the Musculoskeletal Structures of the Mouth and Face.
• Pains of the Visceral Structures of the Mouth and Face arise from deeper structures such as salivary glands.
• Sialadenitis (salivary gland inflammation) and oropharyngeal infections are examples of Pains of the Visceral Structures of the Mouth and Face.
• Pains of the Neural Structures of the Mouth and Face are linked to nerve damage or dysfunction in the orofacial region.
• Trigeminal neuralgia and post-traumatic neuropathy are examples of Pains of the Neural Structures of the Mouth and Face.

Axis II: Psychological Conditions

• Axis II addresses psychological conditions that either directly produce or significantly influence the pain experience.
• These conditions impact how patients perceive, respond to, and manage pain.
• Anxiety Disorders involve excessive worry and fear that can amplify pain perception.
• Generalized anxiety disorder and panic disorder are examples of Anxiety Disorders..
• Mood Disorders involve emotional disturbances that can exacerbate pain sensitivity.
• Depression and bipolar disorder are Mood Disorders.
• Somatoform Disorders are psychological conditions presenting as physical symptoms with no identifiable medical cause.
• Somatization disorder and conversion disorder are Somatoform Disorders.
• Other Psychological Factors Affecting a Medical Condition are mental health issues that influence the onset, severity, or progression of physical pain.
• Post-traumatic stress disorder (PTSD) and health-related anxiety are examples of Other Psychological Factors Affecting a Medical Condition.
• Effective pain management requires addressing both physical (Axis I) and psychological (Axis II) components.
• For example, treating dental pain (Axis I) may require concurrent anxiety management (Axis II) for optimal patient outcomes.
• A comprehensive evaluation should include both physical examination and psychosocial history to ensure all contributing factors are identified and managed.
• Treatment must target the underlying physical pathology while considering the psychological state to enhance recovery and prevent chronic pain conditions.
• Anxiety, depression, and catastrophizing influence pain perception and chronicity.
• Significant life events and early trauma can predispose individuals to chronic pain.
• A holistic assessment of the patient is crucial.
• Ensure neoplasia is excluded in persistent, unexplained pain.

Red Flags in Orofacial Pain

• Recent onset or rapid progression.
• Unexplained sensorimotor neuropathy.
• Persistent painless ulcers or lymphadenopathy.
• Unresponsiveness to conventional treatments.
• Associated systemic symptoms such as weight loss, night fevers, or anemia.

Conclusion

• Pain is a complex experience involving physiological and psychological factors.
• Accurate diagnosis requires a thorough history and structured assessment.
• ICOP 2020 provides a foundation for consistent classification and management of orofacial pain.

Explore the key classifications of pain: temporal, mechanistic, and regional. Understand acute, nociceptive, inflammatory, and neuropathic pain types. Learn how each classification responds to different treatments and the conditions associated with them.