Pearls & Oy-sters: Postpipeline Headache Phenomenon

Discussion

The best term to describe the patient's new headache presentation is postpipeline embolization headache phenomenon. This relatively new term describes a new or different headache in individuals who recently underwent intracranial vascular stenting as a treatment for cerebral aneurysms.¹ A recent study performed a telephone survey of 88 individuals who underwent flow-diverting/Pipeline stenting for the treatment of cerebral aneurysms.¹ Of the patients surveyed, 55% reported a new postprocedural headache with varying characteristics and associated symptoms. Individuals described their pain as dull, sharp, or throbbing, typically located ipsilaterally to the aneurysm/stent. The headaches started an average of 20 days after the procedure, and 69% of patients were still experiencing the headache an average of 21.6 months later. Most patients described intermittent rather than constant head pain, with an average headache frequency of 2–3 times per week, an average duration of 9.7 hours and an average 3.6/10 pain intensity.¹ It is of interest that predictors for developing postpipeline embolization headache include young age and a history of headaches, both of which were present in our patient.

Numerous headache phenotypes can occur after postflow diverter intracranial stenting.¹ By her description, our patient's postflow diverter headache most closely resembled the phenotype of a nummular headache (NH), characterized by focal head pain in a well-circumscribed oval or elliptical-shaped area. The current International Classification of Headache Disorders, Third edition (ICHD-3) diagnostic criteria for NH require the pain to be as follows: (1) continuous or intermittent; (2) felt exclusively in the area of the scalp described as sharply contoured, fixed in size and shape, round/elliptical, and 1–6 cm in diameter; and (3) not corresponding better to another ICHD-3 diagnosis.²

The pain of NH is most often persistent, similar to our case, with up to 75% of published cases describing pain present for more than 3 months.² The painful area may be anywhere on the scalp but is typically located in the parietal region.² Pain is generally described as pressure-like, sharp or stabbing, and is of mild-to-moderate intensity, with occasional superimposed severe exacerbations.³ In a review of 250 patients with NH, the average age at onset was 45 years, with a female predominance.⁴ Similar to our patient, patients with NH commonly have abnormal sensation in the affected area and may describe variable combinations of paresthesia, dysesthesia, and allodynia in the affected area.² Treatment of NH resembles treatment for other primary headache disorders, with 55% of patients requiring preventative therapy.⁵ Gabapentin, indomethacin, tricyclic antidepressants, and onabotulinumtoxinA have been reported effective in select cases.^3,-,5 Unfortunately, NH can become refractory to abortive and preventive analgesic therapies, as seen in our patient's presentation.

While NH is considered a primary headache disorder, numerous possible secondary etiologies have been described (Table). Headaches resembling NH have occurred after trauma and in association with bony lesions such as fibrous dysplasia, craniosynostosis, Paget disease, and Langerhans histiocytosis.³ Some secondary cases have described pathology corresponding to the affected area, such as varicella zoster viral infection, calcified hematoma, and linear scleroderma; other cases have a less clear association with the location of pathology, such as contralateral NH after a pituitary adenoma resection.³ Pertinent to our case, there have been several cases of NH associated with vascular pathologies, although each of these were associated with fusiform areas of superficial vessels near the area of pain.³

Our patient developed ipsilateral NH after placement of a flow-diverting stent in the right paraclinoid ICA. Pain from stimulation within the ICA is not without precedent. In classic studies performed by Ray and Wolff⁶ in 1940, the intracranial carotid artery was found to be sensitive to pain brought on by stretching, stroking, and faradic stimulation. Focal referred pain has also been demonstrated ipsilateral to balloon inflation within the distal ICA.⁷ While the intracranial portion of the ICA is generally believed to refer pain to the frontotemporal region due to innervation from the trigeminal nerve, there is significant anatomic variation in the innervation of intracranial structures, with overlapping innervation by both trigeminal and the upper cervical nerves.⁸

Endovascular treatment of aneurysms using flow-diverting devices such as Pipeline stents is becoming relatively common. Most complications are asymptomatic; however, severe complications can also occur including in-stent stenosis or potential branch occlusions of perforating arteries with a risk of ischemia. Therefore, any patient presenting with new unexplained headache after an endovascular stent procedure for an intracranial aneurysm requires additional evaluation. If the evaluation shows no structural abnormalities and the new postprocedural headache remains unexplained, postpipeline embolization headache should be considered in the differential.