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Thunderclap headache was the subject of a recent review in this journal, in which the pathophysiology was linked to segmental vasospasm.1 Specifically, the abrupt onset of the headache was linked to vasospasm caused by neurogenic rather than biochemical mechanisms. Hyperventilation can probably induce generalised vasospasm through alkalosis of the cerebrospinal fluid.2 We recently saw a patient where hyperventilation or exertion caused thunderclap-like headaches.
This previously healthy 15 year old boy was admitted to Leiden University Medical Centre because of acute (that is, maximum severity within one minute), severe left sided headache associated with, successively, a numb and tingling sensation in the right arm and leg, weakness of the right arm for 30 minutes, and difficulty in speaking. Four weeks earlier, after running for several minutes to catch a train, he suffered an acute, severe bi-frontal, throbbing headache, which subsided within minutes after he stopped running. There were no associated symptoms. Three weeks before admission he experienced a similar headache for 30 minutes which started after 10 minutes of running. That evening a third episode occurred but this time the headache started spontaneously, lasted for two hours, and was accompanied by nausea and vomiting. In the subsequent three weeks until admission, these headache episodes occurred every one or two days, occasionally triggered by exertion, but often seemingly spontaneous.
On admission, physical examination was uneventful apart from non-fluent speech and decreased dexterity of the right hand. Brain magnetic resonance imaging scan, cerebrospinal fluid, and an electrocardiogram (ECG) were normal. The next day only a dull sensation in the head persisted and neurological examination was normal. Physical exertion (climbing stairs for 10 minutes) increased the dull sensation only slightly. However, forced hyperventilation while seated provoked a sudden severe headache that continued for 30 minutes after stopping hyperventilation and that was not accompanied by other symptoms. The patient recognised the headache as the same as those he had been suffering previously. Quantified hyperventilation was abnormal (positive on five of seven items). Spirometry was normal and no pulmonary cause for hyperventilation was found. He was discharged and relaxation exercises and physical therapy were initiated. He has since been able to exercise and run normally, and has had no more headaches. No re-challenge with forced hyperventilation was performed. Last follow up was six months after discharge.
This patient had three, apparently different types of severe, acute, alarming headaches: (1) exertion induced headaches, (2) spontaneous headaches, and (3) one episode of headache associated with nausea, vomiting, and transient focal neurological symptoms. Recurrent headaches following exertion may be caused by serious cerebral disorders such as subarachnoid haemorrhage, posterior fossa tumour, or Arnold-Chiari malformation, but these were all excluded.3 Cardiac ischaemia is a rare cause of unilateral exertional headache. Although no ECG during exertion was performed, the normal ECG at the time of complaints and the ability to exercise normally after relaxation therapy make this an unlikely cause. Cerebral angiography was not performed.
Benign exertional headache typically presents as bilateral throbbing headaches for five minutes to 24 hours following physical exercise.3 In the present patient, however, the headache was induced by hyperventilation following exercise, rather than by the exercise itself. His “spontaneous” headaches, most likely, were also caused by hyperventilation; this is supported by the complete disappearance of these headaches after initiation of relaxation therapy. Although hyperventilation can cause a dull and non-specific generalised headache in about 20% of patients, such an alarming, explosive type of headache has, to our knowledge, never been described.4 The attack that prompted admission, most likely, was migraine with aura, as supported by the sequential rather than simultaneous development of neurological symptoms. Migraine seems to occur more frequently in patients with benign exertional headache.5
Our case illustrates that hyperventilation, both in rest and following physical exertion, may cause severe, acute, “explosive” headaches, and that adequate relaxation exercises and physical therapy can prevent these alarming headaches. The precise mechanism of the headache in our patient remains elusive. Additionally, although breathing exercises would not prevent physiological exercise induced hyperventilation, they may prevent excessive hyperventilation following exercise. Hyperventilation provocation tests can be diagnostic and should be considered in all patients with exertion induced headaches. In light of the recent review, magnetic resonance angiography could be considered in such cases to evaluate a possible involvement of cerebral vasospasm.1