Dizziness is an impairment in spatial perception and stability. Because the term "dizziness" is imprecise, it can refer to vertigo, presyncope, disequilibrium, or a non-specific feeling such as giddiness or foolishness.

One can induce dizziness by engaging in disorientating activities such as spinning.

- Vertigo is the sensation of spinning or having one's surroundings spin about them. Many people find vertigo very disturbing and often report associated nausea and vomiting. It represents about 25% of cases of occurrences of dizziness.

- Disequilibrium is the sensation of being off balance, and is most often characterized by frequent falls in a specific direction. This condition is not often associated with nausea or vomiting.

- Presyncope is lightheadedness, muscular weakness and feeling faint as opposed to a syncope, which is actually fainting.

- Non-specific dizziness is often psychiatric in origin. It is a diagnosis of exclusion and can sometimes be brought about by hyperventilation.

A stroke is the cause of isolated dizziness in 0.7% of people who present to the emergency room.

Dizziness is broken down into 4 main subtypes: vertigo (~50%), disequilibrium (less than ~15%), presyncope (less than ~15%) and lightheadedness (~10%).

Lightheadedness is a common and typically unpleasant sensation of dizziness and/or a feeling that one may faint. The sensation of lightheadedness can be short-lived, prolonged, or, rarely, recurring. In addition to dizziness, the individual may feel as though his or her head is weightless. The individual may also feel as though the room is what causes the "spinning" or moving (vertigo) associated with lightheadedness. Most causes of lightheadedness are not serious and either cure themselves quickly, or are easily treated.

Keeping a sense of balance requires the brain to process a variety of information received from the eyes, the nervous system, and the inner ears. If the brain is unable to process these signals, such as when the messages are contradictory, or if the sensory systems are improperly functioning, an individual may experience lightheadedness or dizziness.

Lightheadedness can be simply (and most commonly) an indication of a temporary shortage of blood or oxygen to the brain due to a drop in blood pressure, rapid dehydration from vomiting, diarrhea, or fever. Other causes are: low blood sugar, hyperventilation, Postural Orthostatic Tachycardia Syndrome, panic attacks, and anemia. It can also be a symptom of many other conditions, some of them serious, such as heart problems (including abnormal heart rhythm or heart attack), respiratory problems such as pulmonary embolism, and also stroke, bleeding, and shock. If any of these serious disorders is present, the individual will usually have additional symptoms such as chest pain, a feeling of a racing heart, loss of speech or change in vision.

Many people, especially as they age, experience lightheadedness if they arise too quickly from a lying or seated position. Lightheadedness often accompanies the flu, hypoglycaemia, common cold, or allergies.

Dizziness could be provoked by the use of antihistamine drugs, like levocetirizine or by some antibiotics or SSRIs. Nicotine or tobacco products can cause lightheadedness for inexperienced users. Narcotic drugs, such as codeine can also cause lightheadedness.

Faintness, dizziness, headache, increased pulse, restlessness, nausea, vomiting, and brief loss of consciousness.

Vertigo is a sensation of spinning while stationary. It is commonly associated with nausea or vomiting, unsteadiness (postural instability), falls, changes to a person's thoughts, and difficulties in walking. Recurrent episodes in those with vertigo are common and frequently impair the quality of life. Blurred vision, difficulty in speaking, a lowered level of consciousness, and hearing loss may also occur. The signs and symptoms of vertigo can present as a persistent (insidious) onset or an episodic (sudden) onset.

Persistent onset vertigo is characterized by symptoms lasting for longer than one day and is caused by degenerative changes that affect balance as people age. Naturally, the nerve conduction slows with aging and a decreased vibratory sensation is common.

Additionally, there is a degeneration of the ampulla and otolith organs with an increase in age. Persistent onset is commonly paired with central vertigo signs and symptoms.

The characteristics of an episodic onset vertigo is indicated by symptoms lasting for a smaller, more memorable amount of time, typically lasting for only seconds to minutes. Typically, episodic vertigo is correlated with peripheral symptoms and can be the result of but not limited to diabetic neuropathy or autoimmune disease.

Vertigo that arises from injury to the balance centers of the central nervous system (CNS), often from a lesion in the brainstem or cerebellum, is called "central" vertigo and is generally associated with less prominent movement illusion and nausea than vertigo of peripheral origin. Central vertigo may have accompanying neurologic deficits (such as slurred speech and double vision), and pathologic nystagmus (which is pure vertical/torsional). Central pathology can cause disequilibrium which is the sensation of being off balance. The balance disorder associated with central lesions causing vertigo is often so severe that many patients are unable to stand or walk.

A number of conditions that involve the central nervous system may lead to vertigo including: lesions caused by infarctions or hemorrhage, tumors present in the cerebellopontine angle such as a vestibular schwannoma or cerebellar tumors, epilepsy, cervical spine disorders such as cervical spondylosis, degenerative ataxia disorders, migraine headaches, lateral medullary syndrome, Chiari malformation, multiple sclerosis, parkinsonism, as well as cerebral dysfunction. Central vertigo may not improve or may do so more slowly than vertigo caused by disturbance to peripheral structures.

Vertigo is a medically recognized term for the symptom of vestibular system disturbance. It may include a feeling of rotation or illusory sensations of motion or both. The general term dizziness is used by nonmedical people for those symptoms but often refers to a feeling of light-headedness, giddiness, drowsiness, or faintness, all of which must be differentiated from true vertigo, since the latter symptoms might have other causes.

Motion sickness occurs more frequently in migraine patients (30–50% more than in controls). Benign paroxysmal vertigo of childhood is an example of migraine-associated vertigo in which headache does not often occur. Basilar artery migraine (BAM) consists of two or more symptoms (vertigo, tinnitus, decreased hearing, ataxia, dysarthria, visual symptoms in both hemifields or both eyes, diplopia, bilateral paresthesias, paresis, decreased consciousness and/or loss of consciousness) followed by throbbing headache. Auditory symptoms are rare. However, a study showed a fluctuating low-tone sensorineural hearing loss in more than 50% of patients with BAM with a noticeable change in hearing just before the onset of a migraine headache. The attacks of vertigo are usually concurrent with the headache and the family history is usually positive. The diagnostician must rule out: TIAs, and paroxysmal vestibular disorder accompanied by headache.

There is also a familial vestibulopathy, familial benign recurrent vertigo (fBRV), where episodes of vertigo occur with or without migraine headache. Testing may show profound vestibular loss. The syndrome responds to acetazolamide. Familial hemiplegic migraine (FHM) has been linked to mutations in the calcium channel gene. (Ophoff et al. 1966 cf. Lempert et al.)

Heat syncope occurs in a warm environment when blood pressure is lowered as the body dilates (widens) arterioles (small blood vessels) in the skin to radiate heat. This condition occurs within five days of heat acclimatization, before the blood volume expands. The result is less blood to the brain, causing light-headedness and fainting when a person stands up quickly or stands for a long period of time. Those who perform strenuous work outside in warm climates are at particular risk.

Benign paroxysmal positional vertigo - Migraine is commonly associated with BPPV, the most common vestibular disorder in patients presenting with dizziness. The two may be linked by genetic factors or by vascular damage to the labyrinth.

Ménière's disease - There is an increased prevalence of migraine in patients with Ménière's disease and migraine leads to a greater susceptibility of developing Ménière’s disease. But they can be distinguished. Ménière's disease may go on for days or even years, while migraines typically do not last longer than 24 hours.

Motion sickness is more prevalent in patients with migraine.

Psychiatric syndromes Dizziness and spinning vertigo are the second most common symptom of panic attacks, and they can also present as a symptom of major depression. Migraine is a risk factor for developing major depression and panic disorder and vice versa.

Benign paroxysmal vertigo of childhood is an uncommon neurological disorder which presents with recurrent episodes of dizziness. The presentation is usually between the ages of 2 years and 7 years of age and is characterised by short episodes of vertigo of sudden onset when the child appears distressed and unwell. The child may cling to something or someone for support. The episode lasts only minutes and resolves suddenly and completely. It is a self-limiting condition and usually resolves after about eighteen months, although many go on to experience migrainous vertigo (or vertiginous migraine) when older.

Benign paroxysmal vertigo of childhood is a migrainous phenomenon with more than 50% of those affected having a family history of migraines affecting a first-degree relative. It has no relationship to benign paroxysmal positional vertigo which is a different condition entirely.

Problems with balance can occur when there is a disruption in any of the vestibular, visual, or proprioceptive systems. Abnormalities in balance function may indicate a wide range of pathologies from causes like inner ear disorders, low blood pressure, brain tumors, and brain injury including stroke.

Many different terms are often used for dizziness, including lightheaded, floating, woozy, giddy, confused, helpless, or fuzzy. Vertigo, Disequilibrium and pre-syncope are the terms in use by most physicians and have more precise definitions.

Vertigo

Vertigo is the sensation of spinning or having the room spin about you. Most people find vertigo very disturbing and report associated nausea and vomiting.

Disequilibrium

Disequilibrium is the sensation of being off balance, and is most often characterized by frequent falls in a specific direction. This condition is not often associated with nausea or vomiting.

Presyncope

Pre-syncope is a feeling of lightheadedness or simply feeling faint. Syncope, by contrast, is actually fainting. A circulatory system deficiency, such as low blood pressure, can contribute to a feeling of dizziness when one suddenly stands up.

Problems in the skeletal or visual systems, such as arthritis or eye muscle imbalance, may also cause balance problems.

A degenerative disease of the autonomic nervous system, symptoms include dizziness and fainting (caused by orthostatic hypotension), visual disturbances and neck pain. Chest pain, fatigue and sexual dysfunction are less common symptoms that may also occur. Symptoms are worse when standing; sometimes one may relieve symptoms by lying down.

When balance is impaired, an individual has difficulty maintaining upright orientation. For example, an individual may not be able to walk without staggering, or may not even be able to stand. They may have falls or near-falls. The symptoms may be recurring or relatively constant. When symptoms exist, they may include:

- A sensation of dizziness or vertigo.

- Lightheadedness or feeling woozy.

- Problems reading and difficulty seeing.

- Disorientation.

Some individuals may also experience nausea and vomiting, diarrhea, faintness, changes in heart rate and blood pressure, fear, anxiety, or panic. Some reactions to the symptoms are fatigue, depression, and decreased concentration. The symptoms may appear and disappear over short time periods or may last for a longer period.

Cognitive dysfunction (disorientation) may occur with vestibular disorders. Cognitive deficits are not just spatial in nature, but also include non-spatial functions such as object recognition memory. Vestibular dysfunction has been shown to adversely affect processes of attention and increased demands of attention can worsen the postural sway associated with vestibular disorders. Recent MRI studies also show that humans with bilateral vestibular damage undergo atrophy of the hippocampus which correlates with their degree of impairment on spatial memory tasks.

The main symptom of labyrinthitis is severe vertigo. Rapid and undesired eye motion (nystagmus) often results from the improper indication of rotational motion. Nausea, anxiety, and a general ill feeling are common due to the distorted balance signals that the brain receives from the inner ear.

Hyperventilation syndrome (HVS); also chronic hyperventilation syndrome (CHVS) and dysfunctional breathing hyperventilation syndrome is a respiratory disorder, psychologically or physiologically based, involving breathing too deeply or too rapidly (hyperventilation). HVS may present with chest pain and a tingling sensation in the fingertips and around the mouth (paresthesia) and may accompany a panic attack.

People with HVS may feel that they cannot get enough air. In reality, they have about the same oxygenation in the arterial blood (normal values are about 98% for hemoglobin saturation) and too little carbon dioxide (hypocapnia) in their blood and other tissues. While oxygen is abundant in the bloodstream, HVS reduces effective delivery of that oxygen to vital organs due to low--induced vasoconstriction and the suppressed Bohr effect.

The hyperventilation is self-promulgating as rapid breathing causes carbon dioxide levels to fall below healthy levels, and respiratory alkalosis (high blood pH) develops. This makes the symptoms worse, which causes the person to try breathing even faster, which further exacerbates the problem.

The respiratory alkalosis leads to changes in the way the nervous system fires and leads to the paresthesia, dizziness, and perceptual changes that often accompany this condition. Other mechanisms may also be at work, and some people are physiologically more susceptible to this phenomenon than others.

Hyperventilation syndrome is a remarkably common cause of dizziness complaints. About 25% of patients who complain about dizziness are diagnosed with HVS.

A diagnostic Nijmegen Questionnaire provides an accurate diagnosis of Hyperventilation.

Symptoms of heat exhaustion include nausea, dizziness, irritability, headache, thirst, weakness, high body temperature, excessive sweating, and decreased urine output.

Many patients will report a history of vertigo as a result of fast head movements. Many patients are also capable of describing the exact head movements that provoke their vertigo. Purely horizontal nystagmus and symptoms of vertigo lasting more than one minute can also indicate BPPV occurring in the horizontal semicircular canal.

Patients do not experience other neurological deficits such as numbness or weakness, and if these symptoms are present, a more serious etiology, such as posterior circulation stroke or ischemia, must be considered.

The spinning sensation experienced from BPPV is usually triggered by movement of the head, will have a sudden onset, and can last anywhere from a few seconds to several minutes. The most common movements patients report triggering a spinning sensation are tilting their heads upwards in order to look at something, and rolling over in bed.

Heat exhaustion is a severe form of heat illness. It is a medical emergency. Heat exhaustion is caused by the loss of water and electrolytes through sweating.

The pathology of pure autonomic failure is not yet completely understood. However, a loss of cells in the intermediolateral column of the spinal cord has been documented, as has a loss of catecholamine uptake and catecholamine fluorescence in sympathetic postganglionic neurons. In general, levels of catecholamines in these patients are very low while lying down, and do not increase much upon standing.

Labyrinthitis, also known as vestibular neuritis, is inflammation of the inner ear. It results in vertigo and also possible hearing loss or ringing in the ears. It can occur as a single attack, a series of attacks, or a persistent condition that diminishes over three to six weeks. It may be associated with nausea and vomiting. Vestibular neuronitis may also be associated with eye nystagmus.

The cause is often not clear. It may be due to a virus, but it can also arise from bacterial infection, head injury, extreme stress, an allergy, or as a reaction to medication. 30% of affected people had a common cold prior to developing the disease. Either bacterial or viral labyrinthitis can cause permanent hearing loss in rare cases. This appears to result from an imbalance of neuronal input between the left and right inner ears.

Vestibular neuritis affects approximately 35 per million people per year. It typically occurs in those between 30 and 60 years of age. There is no significant gender difference. It derives its name from the labyrinths that house the vestibular system, which senses changes in head position.

A number of heat illnesses exist including:

- Heat stroke - Defined by a body temperature of greater than due to environmental heat exposure with lack of thermoregulation. Symptoms include dry skin, rapid, strong pulse and dizziness.

- Heat exhaustion - Can be a precursor of heatstroke; the symptoms include heavy sweating, rapid breathing and a fast, weak pulse.

- Heat syncope - Fainting or dizziness as a result of overheating.

- Heat edema

- Heat cramps - Muscle pains that happen during heavy exercise in hot weather.

- Heat rash - Skin irritation from excessive sweating.

- Heat tetany - Usually results from short periods of stress in intense heat. Symptoms may include hyperventilation, respiratory problems, numbness or tingling, or muscle spasms.

Functional somatic syndrome is characterized by ambiguous, non-specific symptoms that appear in otherwise-healthy populations. Overlap exists in different syndromes, including gastrointestinal issues, pain, fatigue, cognitive difficulties, and sleep difficulties. Some have proposed to group symptoms into clusters or into one general functional somatic disorder given the finding of correlations between symptoms and underlying etiologies.

In medicine, disequilibrium refers to an impaired sense of equilibrioception.

It is one of the causes of dizziness.