In its milder and infrequent forms, episodic tension-type headache (ETTH) is usually experienced as a normal headache or as a nuisance. In its frequent forms, however, it becomes distressing and socially disturbing, although it rarely incapacitates those affected to the same degree as chronic tension-type headache (CTTH) or migraine. Most previous studies in tension-type headache (TTH) have been performed in specialized headache clinics and have dealt with the chronic form. Patients with the episodic form very rarely consult a specialist and therefore would not be included in such studies. The pattern of TTH seen in general practice is clearly milder and different from that present in patients referred to a specialist, although most sufferers have not even consulted a general practitioner (
4,
10,
27,
34,
40). In recent years more data from the general population have been published (
4,
10,
27,
34,
40), demonstrating a large variation in headache pattern in individuals with ETTH. The clinical manifestations of ETTH will be summarized in this chapter. (See also
Chapter 67 on epidemiology.)
DIAGNOSIS AND CLASSIFICATION OF EPISODIC TENSION-TYPE HEADACHE
The classification of TTH has changed significantly in the International Classification of Headache Disorders (ICHD)-II (
14) as compared to the previous ICHD-I (
13). The different types of ETTH included in the classification are shown in
Table 77-1.
As can be seen, ETTH is subclassified as infrequent or frequent, with the arbitrary distinction that patients with less than 12 days per year of TTH fall into the infrequent category and patients with greater than or equal to 12 days per year and less than 15 days per month fall into the frequent category. The diagnostic criteria for infrequent and frequent ETTH are identical, except for criterion A, where the frequency is specified.
Other than the division into infrequent ETTH and frequent ETTH, the basic diagnostic criteria have not changed (
Table 77-2). In the ICHD-I classification, ETTH was subdivided into a form with and a form without a muscular factor. In the ICHD-II classification, it has been specified that this subdivision is based only on manual palpation, which is used to determine whether pericranial tenderness is present (
Table 77-3).
For headaches resembling ETTH that do not quite fulfill the diagnostic criteria for this disorder, a diagnosis of probable ETTH can be made, either infrequent or frequent. Diagnostic criteria for probable frequent ETTH are given in
Table 77-4. It should be noted that if headaches also fulfill the diagnostic criteria for definite (not probable) migraine without aura, they should be coded to that diagnosis, rather than probable ETTH.
CLINICAL PICTURE OF EPISODIC TENSION-TYPE HEADACHE
Most patients with ETTH do not seek medical assistance because their headaches usually are mild in intensity, are relatively short-lasting, lack the migraine-associated incapacitating symptoms of nausea and vomiting, and usually respond to simple analgesics. The clinical picture is therefore not as well described as it is for most other primary headache disorders. Furthermore, the diagnosis of ETTH is also frequently overlooked because most patients in headache clinics focus on their most severe and most recent headaches. In the comparative study by Russell et al., where headache diagnosis from a clinical interview was compared to the diagnosis from a diagnostic prospective headache diary, less than 50% of the patients that actually
had ETTH during the prospective diary recording period reported such episodes at the clinical interview. In contrast, the vast majority of migraineurs were identified initially (
41). As most patients in specialized headache clinics have several coexisting headache disorders, it is necessary to focus on these mild headaches because they comprise a very important differential diagnosis to migraine. They are also probably the main reason for accelerating and inappropriate drug consumption because many patients treat them as mild migraine attacks with antimigraine medications.
The mean duration of ETTH has been reported to be 10.3 years in a German population study (
12) and 9 years in a recent clinical study (
50). These studies illustrate that TTH is a long-lasting pain disorder and that subjects suffer several years before seeking medical help.
In a recent clinical study of 55 patients from a specialized headache clinic, the median frequency of episodes was 6 days per month (
50), compared to a median frequency at 2.2 days per month in the general population (
12). In another population-based study, which included all TTH, the median number of attacks suffered per year was 6, with a median duration of attacks of 4 hours (
32). The impact of frequent ETTH has only rarely been reported, but in epidemiologic studies ETTH accounted mostly for reduced effectiveness whereas 3 workdays were missed per month in the clinical study mentioned above.
In daily clinical practice individuals with infrequent TTH are regarded as headache free, but it is important to emphasize that they are not completely headache-free from a genetic and pathophysiologic point of view. Because of this, they should probably be categorized separately from headache-free subjects in future research.
Duration of each headache episode is also extremely variable, with mean values between 4 and 13 hours and extreme values at 30 minutes to 72 hours (
18,
20). These values are similar to those from older studies that used less strict criteria (
18). The male:female ratio at 4:5 and the highly variable temporal profile within and between patients are additional features that distinguish TTH from migraine (
23,
33,
44,
46).
CLINICAL FEATURES OF TENSION-TYPE HEADACHE AND THE DIAGNOSTIC CRITERIA
It is perhaps a somewhat circular exercise to discuss the clinical symptomatology of a condition that is itself defined primarily by clinical diagnostic criteria. Although this is not unique to ETTH, it is especially important in this condition because TTH is perhaps the least well defined of the primary headache types in the new International Headache Society (IHS) classification (
14). ETTH occupies that broad expanse between patients having no headache and patients with mixed headaches also meeting the diagnostic criteria for migraine. Often called “ordinary or common headaches” by patients with migraine who also have some ETTH, ETTH is characterized to a very significant degree by what is not present.
Nevertheless, patients with ETTH do display a spectrum of symptoms and symptom severity, and it is important that the clinical spectrum of ETTH be better defined by clinical research. An attempt has been made to do this by asking adolescents whether their headaches met the following description: “This headache may start gradually and the pain is mild or moderate. The pain is usually located in the whole head or in the neck. It feels like it is tightening or pressing (like a band around the head). I usually have no nausea or vomiting. When I have this headache I can normally keep on with my schoolwork, my homework, and most physical activity.” When the diagnosis of TTH was made in this manner and compared with the diagnosis made in the same subjects by neurologist interviews, the sensitivity was 87% and the specificity 88%. The positive predictive value was 83% and the negative predictive value 91%. Therefore, the vast majority of TTH in the 92 young subjects studied fit this classical description of ETTH (
51).
CHARACTER OF PAIN
Patients usually describe their pain as a “dull,” “nonpulsating” headache, and terms such as a sensation of “tightness,” “pressure,” or “soreness” are often employed; some patients refer to a “band” or a “cap” compressing their head, while others mention a big “weight” over their head and/or their shoulders (
11,
51). Several studies confirm this pain quality. In a series of 402 patients, a dull head pain was found in 85% and a “tight heaviness” in 83% (
9). The high incidence of a pressing quality was confirmed in later studies; it was present in 78% of 488 subjects with ETTH from the general population (
35,
36) but only in 52% of 50 patients with ETTH from a prospective diary study (
17).
A pulsating character occurs “seldom” or “never” in 80 to 86% of the patients from clinical populations (
17,
18). The most frequent pain quality in TTH is thus nonpulsating and pressing, although it may be experienced as periodically pulsating during severe pain episodes in a minority of subjects (
37).