Sir, we report here the first case of paracetamol (acetaminophen) misuse and overdose due to an undiagnosed cluster headache.

A 32-year-old man presented himself at a dental emergency service due to an unbearable pain resistant to analgesics in the right maxillary region lasting for two days. He reported severe, intermittent and poorly localised right hemifacial pain evolving for six months. Due to this intensive pain, he ingested 32 g of paracetamol during the night corresponding to 12 hours.

Clinical examination revealed asthenia, dizziness, pallor, sweating and nausea with episodes of bilious vomiting in the morning. Extraoral examination revealed a discrete oedema of the right hemifacial region, a slight ptosis and tearing of the right eye. The intraoral examination and the periapical radiographic examination were unremarkable.

The patient was then hospitalised for paracetamol over-consumption and probable cluster headache. At the entrance examination, the biological analysis showed increased liver enzyme activity (alanine transaminase, gamma-glutamylcyclotransferase and amylases). Breakthrough pains in the right hemifacial region were multi-daily, lasting from 15 minutes to several hours and were not relieved by analgesics. He also reported moderate photophobia for two years. All these elements confirmed the diagnosis of cluster headache.

The treatment initially consisted in the administration of N-acetylcysteine for paracetamol overdose. This allowed the normalisation of biological parameters. Cluster headache requires special awareness from practitioners and dentists because some patients report only dental or midfacial pain as a primary presentation.1 The median time to diagnose cluster headache is three years and over 30% of the patients report having consulted a dentist, an otorhinolaryngologist, an ophthalmologist or a neurologist before being diagnosed. More than 16% had a dental, sinus or eye surgery without improvement.2

Thus, it seems necessary for dentists to know the main clinical signs of this pathology.2 The differential diagnosis must be made with other primary headaches (shorter, more frequent and responding well to analgesics) and with facial neuralgia (serial short access). Cluster headaches may also be secondary to vascular, tumour, infectious or inflammatory pathologies. Thus, brain imaging is essential.2 The treatment consists of administration of sumatriptan (6 mg subcutaneous) in case of breakthrough pain associated to a background treatment including verapamil (120 mg, three times a day) and prednisolone with a decreasing dosage for seven days. This treatment enabled the disappearance of the crises in this case.