Infraorbital neuralgia: A diagnostic possibility in patients with zygomatic arch pain

Dear Editor:

Neuralgia of the infraorbital nerve is an unusual cause of facial pain. The patient experiences paroxysmal or constant discomfort, often in the form of stabbing pain, in the distribution area of the infraorbital nerve.¹ The sensation is associated with hypersensitivity to palpation in the infraorbital notch.

The infraorbital nerve is a branch of the maxillary nerve. It originates in the infraorbital canal of the upper jaw and then follows the anterior and superior dental canal, branching off towards the incisor and canine roots and towards the mucous membranes of the anterior part of the inferior meatus.²

We present the case of a patient with left zygomatic arch pain refractory to medical treatment that was temporarily resolved with an infraorbital nerve block.

Our patient was a man aged 39 years with no relevant medical history. He made an appointment with the headache service because he had been experiencing continuous burning pain with no apparent cause over a 16-month period. Pain intensity was 5 out of 10 on the visual analog scale (VAS, with 0 indicating no pain and 10, the worst pain imaginable); it was located in the left zygomatic arch. He also experienced infrequent exacerbations lasting about an hour during which pain intensity was 9/10 on the VAS. Neurological examination yielded the surprising finding that this pain could be provoked by palpation of the nerve in the infraorbital notch. No other concomitant data of interest were observed.

Before attending our service, he had been assessed by the otorhinolaryngology and maxillofacial surgery departments. MRI and facial CT scans had been performed and neither yielded pathological findings.

Pain responded partially to naproxen but did not abate with a daily dose of 200 mg of lamotrigine.³ Since we suspected neuralgia of the infraorbital nerve, we performed an anesthetic block with 1 cm³ of lidocaine.⁴ Cessation of pain for 2 weeks confirmed the diagnosis (code 13.7 in the second edition of the International Headache Classification [ICHD-2]).⁵

We later performed several anesthetic blocks that were temporarily effective. Results did not change on the one occasion when anesthetic block was associated with a corticosteroid. We continued looking for a means of long-term pain resolution since it was not achieved with amitriptyline dosed at 25 mg daily and carbamazepine was not well tolerated. Partial improvement of symptoms has currently been achieved with pregabalin dosed at 150 mg daily.

When doctors suspect infraorbital neuralgia, they must rule out other symptomatic causes in order to assign a diagnosis. Doctors should determine if there is any history of traumatic episodes.⁶ Where no such history is present, they must rule out other secondary causes, mainly neoplasms that can cause these symptoms due to haematogenous, lymphatic, or perineural spread. For these reasons, imaging studies are recommended for all these patients.^7,8 Once all the above have been ruled out, we can consider primary neuralgia^9,10 and confirm the diagnosis after achieving pain relief with anesthetic nerve block.

Infraorbital neuralgia may be refractory to medical treatment, which generally includes analgesic, anti-inflammatory, anti-epileptic, or antidepressant drugs.¹¹ Other therapy alternatives include electrical transdermal nerve stimulation in extremely resistant cases.¹²

Cases of terminal branch neuralgia of the trigeminal nerve are rare and they frequently manifest as continuous pain. In contrast, cases of central involvement of the trigeminal nerve are generally associated with painful paroxysms.^13–15 Considering these neuralgias and palpating the nerve territories corresponding to the painful area may provide effective treatment alternatives for symptoms that are frequently persistent and incapacitating. Nerve block is among the essential diagnostic criteria for these neuralgias, and it may therefore be suggested as a first therapeutic step, as in our case.