Persistent Idiopathic Facial Pain

Persistent idiopathic facial pain (formerly atypical facial pain) is daily facial pain for most of the day, over more than 3 months, poorly localised, not following a nerve distribution, with no sensory loss or other cause on examination and investigation. It affects women more often, with onset around 30 to 50 years, and a prevalence of about 0.03 to 1%.

Pathophysiology. Central sensitisation and abnormal pain processing are thought to underlie it, often with psychological comorbidity.

Deep, dull, aching or burning pain in one side of the face, often at the maxilla or angle of the jaw, which may spread to the neck or become bilateral. Pain is continuous, with fluctuating intensity, and may follow minor surgery or injury. Stress and fatigue worsen it. There are no autonomic features, no paroxysms, and neurological examination is normal. Depression, anxiety and sleep disturbance are frequent.

Red flags.

• Sensory loss, cranial nerve palsy or facial swelling.
• Weight loss, fever or jaw claudication with age over 50 years.

Diagnosis is by exclusion. Examine the face, mouth and cranial nerves. MRI of the brain with attention to the skull base, cerebellopontine angle and trigeminal nerve is advised to exclude secondary causes. Dental and sinus assessment (panoramic radiograph, CT sinuses). Check ESR and CRP when giant cell arteritis is possible. Screen for depression and anxiety.

Differential diagnosis.

• Trigeminal neuralgia and painful post-traumatic trigeminal neuropathy.
• Temporomandibular disorder, dental and sinus disease.
• Giant cell arteritis, cluster headache and burning mouth syndrome.
• Neoplasm of the skull base and postherpetic neuralgia.

Avoid unnecessary dental or surgical procedures.

Explanation and psychology. Reassurance, education, cognitive behavioural therapy and pain management programmes.

Drugs.

• Amitriptyline 10 mg at night, increased gradually by 10 mg every 1 to 2 weeks to 50 to 75 mg (or nortriptyline).
• Alternatives: venlafaxine 37.5 mg daily, increased to 150 mg daily, duloxetine 30 to 60 mg daily, gabapentin 300 mg daily, increased to 1800 mg daily, or pregabalin 75 to 300 mg twice daily (adjust to eGFR).
• Topical capsaicin or lidocaine in selected cases. Opioids are not advised.

Other options. Botulinum toxin, transcutaneous electrical nerve stimulation and neuromodulation (occipital nerve stimulation) in refractory cases. Avoid nerve ablation and surgery, which can worsen the pain.

Monitoring. Pain diaries, mood and drug adverse effects.

Referral and escalation. Refer to neurology or a pain clinic, and to psychology.