Cluster Headache: A primary headache disorder that is characterized by severe, strictly unilateral PAIN which is orbital, supraorbital, temporal or in any combination of these sites, lasting 15-180 min. occurring 1 to 8 times a day. The attacks are associated with one or more of the following, all of which are ipsilateral: conjunctival injection, lacrimation, nasal congestion, rhinorrhea, facial SWEATING, eyelid EDEMA, and miosis. (International Classification of Headache Disorders, 2nd ed. Cephalalgia 2004: suppl 1)Headache: The symptom of PAIN in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of HEADACHE DISORDERS.Vascular Headaches: Secondary headache disorders attributed to a variety of cranial or cervical vascular disorders, such as BRAIN ISCHEMIA; INTRACRANIAL HEMORRHAGES; and CENTRAL NERVOUS SYSTEM VASCULAR MALFORMATIONS.Headache Disorders: Various conditions with the symptom of HEADACHE. Headache disorders are classified into major groups, such as PRIMARY HEADACHE DISORDERS (based on characteristics of their headache symptoms) and SECONDARY HEADACHE DISORDERS (based on their etiologies). (International Classification of Headache Disorders, 2nd ed. Cephalalgia 2004: suppl 1)Tension-Type Headache: A common primary headache disorder, characterized by a dull, non-pulsatile, diffuse, band-like (or vice-like) PAIN of mild to moderate intensity in the HEAD; SCALP; or NECK. The subtypes are classified by frequency and severity of symptoms. There is no clear cause even though it has been associated with MUSCLE CONTRACTION and stress. (International Classification of Headache Disorders, 2nd ed. Cephalalgia 2004: suppl 1)Migraine Disorders: A class of disabling primary headache disorders, characterized by recurrent unilateral pulsatile headaches. The two major subtypes are common migraine (without aura) and classic migraine (with aura or neurological symptoms). (International Classification of Headache Disorders, 2nd ed. Cephalalgia 2004: suppl 1)Sumatriptan: A serotonin agonist that acts selectively at 5HT1 receptors. It is used in the treatment of MIGRAINE DISORDERS.Trigeminal Autonomic Cephalalgias: Primary headache disorders that show symptoms caused by the activation of the AUTONOMIC NERVOUS SYSTEM of the TRIGEMINAL NERVE. These autonomic features include redness and tearing of the EYE, nasal congestion or discharge, facial SWEATING and other symptoms. Most subgroups show unilateral cranial PAIN.Headache Disorders, Primary: Conditions in which the primary symptom is HEADACHE and the headache cannot be attributed to any known causes.Pterygopalatine Fossa: A small space in the skull between the MAXILLA and the SPHENOID BONE, medial to the pterygomaxillary fissure, and connecting to the NASAL CAVITY via the sphenopalatine foramen.Trigeminal Nerve: The 5th and largest cranial nerve. The trigeminal nerve is a mixed motor and sensory nerve. The larger sensory part forms the ophthalmic, mandibular, and maxillary nerves which carry afferents sensitive to external or internal stimuli from the skin, muscles, and joints of the face and mouth and from the teeth. Most of these fibers originate from cells of the TRIGEMINAL GANGLION and project to the TRIGEMINAL NUCLEUS of the brain stem. The smaller motor part arises from the brain stem trigeminal motor nucleus and innervates the muscles of mastication.Alkadienes: Acyclic branched or unbranched hydrocarbons having two carbon-carbon double bonds.Migraine with Aura: A subtype of migraine disorder, characterized by recurrent attacks of reversible neurological symptoms (aura) that precede or accompany the headache. Aura may include a combination of sensory disturbances, such as blurred VISION; HALLUCINATIONS; VERTIGO; NUMBNESS; and difficulty in concentrating and speaking. Aura is usually followed by features of the COMMON MIGRAINE, such as PHOTOPHOBIA; PHONOPHOBIA; and NAUSEA. (International Classification of Headache Disorders, 2nd ed. Cephalalgia 2004: suppl 1)Spinal Nerves: The 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included.Migraine without Aura: Recurrent unilateral pulsatile headaches, not preceded or accompanied by an aura, in attacks lasting 4-72 hours. It is characterized by PAIN of moderate to severe intensity; aggravated by physical activity; and associated with NAUSEA and / or PHOTOPHOBIA and PHONOPHOBIA. (International Classification of Headache Disorders, 2nd ed. Cephalalgia 2004: suppl 1)Paroxysmal Hemicrania: A primary headache disorder that is similar to the CLUSTER HEADACHE with unilateral head pain, but differs by its multiple short severe attacks. It is usually seen in females, and may be responsive to non-steroidal-anti-inflammatory drugs (NSAIDS).Tryptamines: Decarboxylated monoamine derivatives of TRYPTOPHAN.Headache Disorders, Secondary: Conditions with HEADACHE symptom that can be attributed to a variety of causes including BRAIN VASCULAR DISORDERS; WOUNDS AND INJURIES; INFECTION; drug use or its withdrawal.Anisocoria: Unequal pupil size, which may represent a benign physiologic variant or a manifestation of disease. Pathologic anisocoria reflects an abnormality in the musculature of the iris (IRIS DISEASES) or in the parasympathetic or sympathetic pathways that innervate the pupil. Physiologic anisocoria refers to an asymmetry of pupil diameter, usually less than 2mm, that is not associated with disease.Cluster Analysis: A set of statistical methods used to group variables or observations into strongly inter-related subgroups. In epidemiology, it may be used to analyze a closely grouped series of events or cases of disease or other health-related phenomenon with well-defined distribution patterns in relation to time or place or both.Trigeminal Caudal Nucleus: The caudal portion of the nucleus of the spinal trigeminal tract (TRIGEMINAL NUCLEUS, SPINAL), a nucleus involved with pain and temperature sensation.Orbit: Bony cavity that holds the eyeball and its associated tissues and appendages.Miosis: Pupillary constriction. This may result from congenital absence of the dilatator pupillary muscle, defective sympathetic innervation, or irritation of the CONJUNCTIVA or CORNEA.Hypothalamus: Ventral part of the DIENCEPHALON extending from the region of the OPTIC CHIASM to the caudal border of the MAMMILLARY BODIES and forming the inferior and lateral walls of the THIRD VENTRICLE.