**3. Headache physiopathology**

as topiramate [4], and sometimes further requiring nonopioid and opioid analgesics such as ketoprofen [5] and codeine [6]. With so many people suffering from headaches and having such a varied set of available drugs for treatment, it is no surprise that the problem of overuse and abuse of such treatments exists, leading to the appearance of secondary adverse effects such as the development of new pain pathways, among a certain group of patients. To understand the complexity of a problem like this, it is necessary to gain a deep knowledge of headache physiopathology, pharmacological options, and treatment guidelines, in order to identify the reasons leading to cephalea treatment overuse, and the arising of such a tricky

Although the concept of cephalea has mostly remained the same since it was first used to describe this type of disorder, its classification has been evolving continuously in line with modern physiopathological and pharmacologic concepts. The term cephalea or cephalalgia denotes pain located anywhere in the head and neck, regardless of the etiology; however, such a vast subject requires a very detailed classification scheme to determine which would be the best treatment for each type. Headaches are divided into two major groups: primary headaches and secondary headaches. Primary headaches are those appearing spontaneously with no association to any other disease or medical condition, while secondary headaches are those appearing in close temporal relation to another condition known to produce cephalea [7]. The main difference between both groups is whether or not an association is found with another cause, thus primary headaches have an intrinsic physiopathology while secondary

cephalea is the consequence of another disease, trauma, or medical condition.

(1) Headache attributed to trauma or injury to the head and/or neck

(2) Headache attributed to cranial or cervical vascular disorder

(3) Headache attributed to nonvascular intracranial disorder

(4) Headache attributed to a substance or its withdrawal

(6) Headache attributed to disorder of homoeostasis

Primary cephalalgia is divided into four major categories:

problem such as the development of new pain pathways.

**2. Classification of headaches**

142 Pain Relief - From Analgesics to Alternative Therapies

(1) Migraine

(2) Tension-type headache

(3) Trigeminal autonomic cephalalgias

While secondary cephalea has eight:

(5) Headache attributed to infection

(4) Other primary headache disorders [8]

A detailed description of the physiopathology of each type of headache goes far from the reach of this chapter, thus the discussion will be focused on the most common subtypes; migraine and tension-type headache as well as on a common feature for each cephalea type: the pain pathway.
