The major findings of the present study were that TIA patients compared to controls more frequently had migraine within the previous year, more often had headache within one week before TIA and at the time of TIA.
Previous studies of headache in TIA
Only few studies have attempted to characterize headache in patients with TIA and no studies were performed in the past 10 years [1,2,3,4,5,6,7,8,9,10]. In most studies headaches were analyzed in TIA patients together with stroke patients [1, 2, 4, 9] but two studies analyzed TIA patients separately [5, 10]. Patients were asked in one study about the presence and localization of headache at symptom onset and to describe the quality of headache according to predefined categories: dull, pressing, stabbing, burning, pulsate, or circular [2]. In the other study patients were asked about the presence and nature (throbbing versus constant) of headache [4]. In three other studies patients were asked about onset, duration, location and quality of headache [1, 5, 9, 10]. Patients were asked about headache prior to TIA only in two studies [1, 5]. All previous studies used CT but not MRI with DWI for detection of infarct and many studies therefore may have included small infarcts. Besides no study could make a specific diagnosis of headache because of absence of classification that time or lack of information about necessary characteristics of the headache. The few studies with a big number of TIA patients did not use a detailed interview about previous and current headache [2, 3]. Therefore, it is difficult to compare our results with previous studies. The character of headaches at TIA onset was different in different studies: throbbing [1, 9] or diffuse [5] or generalized non-localized [10]. The overall prevalence of headache at the time of TIA varied from 16% to 36% and is thus in accordance with our results [1,2,3,4,5,6,7,8,9,10].
Methodological considerations
Several principles should be taken into account in studies of headache in TIA patients. First of all, it is impossible to know the exact diagnosis of headache without using the diagnostic criteria of the International classification of headache [11]. This requires a professional semi-structured interview about previous and current headache, preferably face to face, because some important characteristics of headache can otherwise be missed in acutely ill patients. It is also necessary to record the exact timing of headache and TIA and to use a generally accepted definition of transient ischemic attacks including MRI with DWI to exclude acute infarcts.
Headache can only manifest in a limited number of ways. Thus, most secondary headaches including headache in TIA patients have the characteristics of tension-type headache or migraine without aura. If there is a close temporal relation, it must, however, be classified as a secondary headache attributed to the causative disorder according to ICHD-3 [11]. Since most of the headaches encountered in the present study were new or had altered characteristics and occurred significantly more often than in the control group, we have chosen to call those occurring in the week before or at the time of TIA migraine–like headaches and tension-type-like headaches.
Significance of our findings
Our results have important clinical implications and also bespeak to some extent the possible mechanisms of headache and migraine.
Can headache be a warning sign of TIA?
From transcranial doppler monitoring it is well known that patients have many neurologically silent cerebral emboli [15]. Perhaps some of them cause headache. Our study showed beyond doubts that headache, more specifically migraine-like headache, is more common within the previous year before TIA than in controls. The difference was even more pronounced within one week of TIA and particularly within the last day before TIA. It seems overwhelmingly likely, therefore, that headache, especially headache of a new type or with altered characteristics can be a warning about impending TIA. But is headache a useful warning symptom? In other words, should such a headache lead to vascular work-up? In our opinion the answer is yes, under some circumstances. All middle aged to elderly patients who encounter a new type of headache should definitely have a vascular work-up. But also middle aged to elderly patients with a previously existing headache such as migraine or tension-type headache should be studied if the headache changes markedly in frequency or character despite the fact that the diagnosis is still the same. Special attention should be paid to patients with accelerating frequency of migraine that cannot otherwise be explained. Some may consider this a too aggressive attitude, but it must be remembered that diagnostic methods needed for prevention of cerebrovascular disorders are quite simple, pose no risk to the patient and that vascular episodes that can be prevented are often serious. Ultrasound examination of the neck vessels and blood tests may suffice, supplemented as necessary according to the degree of risk and other factors.
Anterior versus posterior circulation TIA
In agreement with previous studies in stroke and TIA [1,2,3,4,5,6,7,8,9,10], we confirm that headaches in TIA patients are more prevalent with posterior circulation TIA. In fact, all our patients with posterior circulation TIA had headache within the week before TIA and many at the time of TIA. The reason for this remains unclear but it is noteworthy that the interest in brain stem and hypothalamic mechanisms of migraine is increasing. During attack of migraine without aura, blood flow was increased in a small area of the ventro-medial medulla and this finding has later been confirmed [16, 17]. The vast majority of migraine auras are caused by blood flow changes thought to be caused by cortical spreading depression in the occipital cortex [18] and, finally, white matter abnormalities in migraine patients are primarily seen in the posterior fossa circulatory territory [15]. There are also reports of small pathologies in the brain stem associated with headache or migraine [17].
Strengths and weaknesses of the present study
To the best of our knowledge this is the first study that has examined headache in TIA patients using a professional, face to face, semistructured interview describing all relevant characteristics of headaches associated with TIA.
One limitation of this study is the quick disappearance of clinical symptoms in TIA patients before admission to the hospital. Some of them could not remember details which are important in the differential diagnosis of TIA and MA. For example, some patients could have missed gradual spread of symptoms or presence of succession of symptoms. Some patients could not describe the characteristics of headache during TIA very well. Therefore some cases of MA could have been missed. However, we performed follow-up of 118 out of 120 patients with TIA. The period of follow-up varied from 6 months till 4 years. We found only one case of migraine with aura which was missed during the first interview. This patient experienced three more similar attacks of migraine with aura during two following years.
The weakness of the present study was using only CT in 8 patients which is not an accurate method for detection of small infarcts, especially in the posterior territory. However we performed a follow-up of these 8 patients during 3 years and nobody from them had recurrent episodes and other neurological problems. Also, the inaccuracy of patient’s recall of headache during the last year may have been a limiting factor.
