Disorders of consciousness are divided into two categories:

Vegetative state—complete unawareness of the self and environment despite preservation of some brain functions (often cardiovascular and autonomic control).

Tension-type or muscle contraction headache is the most common type of primary headache.

Migraine headache, the second most common type of primary headache, has four phases:

Chronic daily headache—any type of headache that occurs ≥15 days per month.

Cluster headache—≥5 attacks of severe, unilateral, orbital, supraorbital, and/or temporal pain lasting 15 to 180 minutes and associated with ipsilateral lacrimation, conjunctival injection, rhinorrhea, nasal congestion, forehead and facial sweating, miosis, ptosis, or eyelid edema.

Thunderclap headache—maximal at onset.

Hemicrania continua—continuous, daily unilateral headache, associated with autonomic features (miosis, ptosis, lacrimation, rhinorrhea).

Group of symptoms that include memory impairment affecting social interactions.

The most common cause of dementia is Alzheimer’s disease (AD).

Vascular dementia—secondary to multiple cerebral infarcts or chronic cerebral ischemia causing white matter injury (Binswanger’s disease).

Normal-pressure hydrocephalus—dementia, gait abnormalities, and urinary incontinence.

Vertigo—an illusion of movement caused by a disorder of the vestibular system.

Near syncope (lightheadedness)—a sensation of almost fainting caused by an inadequate cerebral perfusion pressure.

Disequilibrium—a sensation of dizziness caused by a gait disorder.

Seizure—any stereotypical experience or activity arising from hypersynchronous discharges in the cerebral cortex and perhaps some subcortical structures.

Epilepsy—a disorder characterized by two, three, or more seizures that are unprovoked by any known proximate insult.

Status epilepticus—continuous seizures lasting for longer than 30 minutes or repeated seizures lasting a total of 30 minutes from which the patient does not recover awareness between episodes.