# Quantitative Electroencephalographic Analysis in Women with Migraine during the Luteal Phase
## 1 Introduction  
Migraine is a form of neurovascular headache [1], with a high incidence (>12%). Predominantly women (3:1 compared with men) are affected and intensity is variable [2]. Migraine is a public health problem, and it is also one of the main causes of incapacity for work because fifty percent of migraine patients interrupt their daily activities due to attacks and most of them require rest at home in dark places [3]. Migraine symptoms negatively affect quality of life as well as academic and work performance and limit the realization of daily activities [4]. In general, it is defined as an episodic attack of intense, pulsating, and unilateral headache that may last from 4 to 72 h ranging from once a week to once a year [5]. The age group with the highest prevalence of migraine is between 25 and 55 years old [6], however, there are reports that indicate that the number of episodes decreases as the age of the patients increases, or at least the prevalenceof unilateral and pulsating pain [7]. With regard to triggers that induce migraine, it has been reported that drinking alcohol, smoking, living with stress, neck pain, and hormonal changes are the main stimuli that play a role [8]. Migraine's etiology involves a neurovascular mechanism and is characterized by cortical hypersensitivity [9]. However, for some authors, it is mainly a neuronal pathology with secondary vascular effects [10]. Migraine has been associated with hormonal changes; several authors have reported that there is an increase in the reproductive years, and menstruation specifically is considered one of the most common triggers for migraine, also affecting the level of pain, the duration of symptoms, and the response to treatment [11; 12; 13]. The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that makes pregnancy possible. The four phases of the menstrual cycle are menstruation, the follicular phase, ovulation, and the luteal phase. Common menstrual problems include heavy or painful periods and premenstrual syndrome. Migraines that occur during the menstrual period tend to be more disabling than those that happen at different times of the month [14]. Moreover, hormonal contraceptive use during the reproductive years and hormone replacement in menopause alter the levels of sex hormones, and these events and interventions are associated with a change in the prevalence and intensity of headaches [14]. Regarding the mechanism for menstrual migraine, it was reported that an estrogen level drop during the late luteal phase may be a marker of vulnerability to migraine symptoms in women that experience migraine [15]. In line with this, others reported a drop in estrogen levels prior to menstruation, which was explained by the effects of estrogens and progestogens on central serotonergic and opioidergic neurons, modulating their neuronal activity and the density of the 5-HT1 type receptor [16; 17]. Although there are some techniques for studying the central mechanisms involved in chronic pain like migraine, electroencephalography (EEG) stands out as a valuable, non-invasive tool because it provides reliable and relevant information about brain functioning during rest, sensory stimulation, and cognitive tasks. In addition, this technique is safe, low-cost, and employs a straightforward methodology, thus making it an appropriate tool for use in clinical practice. EEG has been applied to assess brain function in several chronic pain syndromes. The American Neurology Academy has suggested that EEG can be used in people with symptoms associated with headaches and migraine [18]. One of the first studies in which EEG alterations were associated with headache dates back to 1959, when [PERSON] and [PERSON] [19], described two main types of EEG frequency response during flickering light: (a) a peak in the alpha band and a rapid decline with an increase in stimulus frequency above 14 f/s, and (b) a flat-top showing a response maintained up to or above 20 f/s.