Excerpt from Chronic Paroxysmal Hemicrania

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Background

Chronic paroxysmal hemicrania (CPH) is also known as Sjaastad syndrome. It was first described in 1974 by Sjaastad and Dale.¹ In 1976, the term CPH was proposed by Sjaastad on the basis of the first 2 patients, who had daily (ie, chronic), solitary, limited attacks (ie, paroxysmal) of unilateral headache that did not shift sides (ie, hemicrania).² CPH, which has been included in the International Headache Society (IHS) classification system since 1988, is much less common than cluster headache (CH).

The short-lasting primary headache syndromes may be divided into (1) headaches with autonomic activation and (2) headaches without autonomic activation. Headaches with autonomic activation include chronic and episodic paroxysmal hemicrania, CH, and short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT syndrome).

Pathophysiology

The mechanisms responsible for the pain in CPH remain unknown. Discussion of important features, such as unilateral intense headache, autonomic abnormalities, and effectiveness of indomethacin, may help in understanding the pathogenesis.³

The release of both trigeminal and parasympathetic neuropeptides during headache has been described.⁴ Activation of the ipsilateral trigeminovascular system may explain sudden unilateral headache and may lead to miosis, increased intraocular pressure (IOP), and other autonomic abnormalities.

Increased sweating and decreased salivation during attacks and inhibition of increased IOP by an alpha-blocking agent or stellate ganglion blockade suggest sympathetic involvement.

Increased tearing, nasal secretion, and miosis may be due to parasympathetic stimulation. Trigeminoparasympathetic activation during CPH attack has been suggested; increases in vasoactive intestinal peptide (ie, parasympathetic peptide) level have been reported. Levels of calcitonin gene-related peptide also are reported to be high during CPH attacks.

Pain and pressure threshold, nociceptive flexion reflex, and blink and corneal reflexes have been studied in patients with CPH. The corneal reflex thresholds have been found to be decreased bilaterally during CPH attacks. Increases in corneal temperature on the symptomatic side also have been reported; this finding may be due to increased ocular blood flow.

The effectiveness of indomethacin in CPH may be due partly to reduction of intracranial blood flow (via a nonprostaglandin mechanism) and partly to its anti-inflammatory effects.

These findings may indicate a primary central mechanism and a secondary involvement of peripheral factors, affecting both the sympathetic and parasympathetic systems.

Frequency

United States

CPH is a rare syndrome, but the number of diagnosed cases is increasing. The prevalence of CPH is not known, but the relative frequency compared with CH is reported to be approximately 1-3% (Antonaci, 1989).

International

Many cases of CPH have been described throughout the world, in different races and different countries, including Australia, Czech Republic, Slovakia, Denmark, Italy, France, Mexico, Canada, Sweden, Germany, Poland, India, Spain, Brazil, South Africa, Norway, New Zealand, the United Kingdom, and the United States.

Mortality/Morbidity

Mortality rate and morbidity of CPH have not been reported, although the therapy of choice, indomethacin, is known to be associated with the risk of bleeding.

Race

CPH is not known to occur preferentially in any race. CPH has been described in Caucasians and black South Africans.

Sex

In the past, because of female preponderance, CPH was considered a disease of women. However, CPH has been reported in increasing numbers of men. A study conducted in 1979 reported a female-to-male ratio of 7:1, but a review of 84 patients in 1989 reported a female-to-male ratio of 2.3:1.

Age

CPH can occur at any age; mean age of onset is 34 years.⁵ The youngest patient described in the literature was aged 6 years and the oldest was aged 81 years.^{6, 7} In one report, CPH beginning at age 3 years was described; however, it may have been related to ipsilateral occipital hemorrhagic infarction.⁸

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