Gaius Plinius Secundus, also known as Pliny the Elder, (AD 23-79) recommended the first headache categorization indicating distinct pain localization i.e., headache

involving the entire head, temporal or occipital [10], and besides he even suggested the application of medicinal herbs for the alleviation of headache [11].

The Greek doctor Aretaeus of Cappadocia, approximately 1st part of 2nd

centennial, made a basal distinction between three types of major headaches and contributed very early to HD classification [12]:

1. Heterocrania: half-sided extremely painful headache, wavering in different head areas and periodically followed by nausea, bilious vomiting, and fainting. Aretaeus then interpreted migraine as heterocrania [13]. Due to the lack of medicine for HD at that period the treatment was limited to bloodletting and laxative [14,15].
2. Cephalea: chronic, intense headache and often difficult to treat [1].
3. Cephalalgia: a mild, short duration of headache. Dangerous if correlated with fever, coldness, or decreased muscle tone [13,16]. His findings contributed basally to the international classifications of the International Headache Society regarding

the categorization of migraine from tension-type headache [17].

The famous Greek physician Galen of Pergamum, who lived around AD 129–199, also categorized headache into three various types: [18].

1. Cephalgia: a mild, short duration of headache
2. Cephalea: chronic, constant pain, with photophobia as a concomitant feature [1].
3. Heterocrania: pounding headache with sudden attacks [1].

He was the first physician to use the term heterocrania, which was later known

as ʻhemicraniaʼ. He assumed that excessive heat or cold could be a triggering aspect for headaches. Galen of Pergamum presumed an individual’s health relied on a personal balance or disharmony of four fluids, namely black bile, blood, humors, and phlegm [19]. His entrenched pattern carried on until the 17th century.

Caelius Aurelianus (5th century) described cephalgia as an acute headache

followed by fever. Hemicrania was characterized by pulsating pain with dizziness, nausea, or emesis and cephalea was a chronic, sequential headache without fever [20]. Table 1 presents the historical definition/naming of the most prevalent primary and secondary headaches.

The neuroanatomist Thomas Willis (AD 1621-1671) from England was a pioneer of contemporary clinical neurology. Continuous headache, intermittent headache, and intermittent headache with vague and uncertain attacks [21] were the three common forms of headache he had distinguished at his time.

Samuel Auguste Tissot (AD 1728-1797), a renowned physician from Switzerland provided clinical insight on migraine in his work «Treatise on the nerves and nervous disorders» [22]. He differentiated between migraine, cephalalgia, cephalaea, and parietal or occipital headache and narrated precisely the recurrence and the pattern of migraine outbreaks [23]. Tissot discovered the involvement of the nervous system in migraine. As a result, he described hemianopia (half-sided blindness), hemiplegia (unilateral or hemiplegic paralysis), and aura [22].

An assistant of the famous physician Herman Boerhaave in Leiden (AD 1668- 1738) named Gerhard van Swieten (AD 1700-1772) composed in AD 1745 several volumes of influential medical textbooks discussing on the scripts of Herman Boerhaave. The content included a fundamental explanation known to date of episodic cluster headache (ECH), which conforms to the benchmark of the International Headache Society of AD 1988 for ECH [24].

An English physician named Edward Liveing (AD 1832-1919) presented new theories on migraine pathogenesis in his book «On Megrim» [25] which was published in AD 1873. His work, a collection of clinical elements, can be regarded as an essential text for neurological comprehension of migraine. He characterized migraine as an appearance of ʻnerve-storm’ and interpreted it as riddance of exuberance nerve-force through the body and brain [26].

Emil du Bois-Reymond (AD 1818-1896) interpreted migraine in AD 1860 as tetany of the vascular muscles and conjectured the pain was induced by the elevated blood pressure against the vessel walls. He also assumed migraine was an ailment of the centrum ciliospinale in the Medulla spinalis [27].

The British neurologist William Richard Gowers (AD 1845-1915) was a pioneer in modern neurology [28]. He was one of the first leading person segregating migraine treatments into abortive or preventive [29]. His, at that time a modern

textbook in neurology, «Manual of Diseases of the Nervous System (AD 1886– 1888)» categorizes every facet of neurological disorder formulated in a pattern according to their section. The book distinguishes epilepsy and headache and contains information about performing the appropriate neurological diagnosis [30].

The first «International Classification of Headache Disorders» (ICHD) was published in AD 1988 and updated in AD 2004 [31]. The currently valid ICHD-3 was published in AD 2018. It distinguishes more than 250 types of headaches, which are divided into primary, secondary, neuropathies & facial pains, and other headaches [32].

The three most common types of primary headaches are Tension-Type Headache (TTH), migraine, and Cluster Headache (CH), whereas migraines and CH are the most important primary headaches in a clinical context, with Medication-Overuse Headache (MOH) being the most important secondary type [33]. The cause of primary headaches to date is still not very clear.

Table 1: Historical definition of most prevalent HD.