Space adaptation syndrome (SAS) or space sickness is a condition experienced by around half of space travelers during adaptation to weightlessness. It is related to motion sickness, as the vestibular system adapts to weightlessness.

Space motion sickness is caused by changes in g-forces, which affect spatial orientation in humans. According to "Science Daily", "Gravity plays a major role in our spatial orientation. Changes in gravitational forces, such as the transition to weightlessness during a space voyage, influence our spatial orientation and require adaptation by many of the physiological processes in which our balance system plays a part. As long as this adaptation is incomplete, this can be coupled to motion sickness (nausea), visual illusions and disorientation."

Modern motion-sickness medications can counter space sickness but are rarely used because it is considered better to allow space travelers to adapt naturally over the first day or two than to suffer the drowsiness and other side effects of medication. However, transdermal dimenhydrinate anti-nausea patches are typically used whenever space suits are worn because vomiting into a space suit could be fatal, as it could obscure vision or block airflow. Space suits are generally worn during launch and landing by NASA crew members and always for extra-vehicular activities (EVAs). EVAs are consequently not usually scheduled for the first days of a mission to allow the crew to adapt, and transdermal dimenhydrinate patches are typically used as an additional backup measure.

Simulator sickness is a subset of motion sickness that is typically experienced by pilots who undergo training for extended periods of time in flight simulators. Due to the spatial limitations imposed on these simulators, perceived discrepancies between the motion of the simulator and that of the vehicle can occur and lead to simulator sickness.

It is similar to motion sickness in many ways, but occurs in simulated environments and can be induced without actual motion. Symptoms of simulator sickness include discomfort, apathy, drowsiness, disorientation, fatigue, vomiting, and many more.

These symptoms can reduce the effectiveness of simulators in flight training and result in systematic consequences such as decreased simulator use, compromised training, ground safety, and flight safety. Pilots are less likely to want to repeat the experience in a simulator if they have suffered from simulator sickness and hence can reduce the number of potential users. It can also compromise training in two safety-critical ways:

1. It can distract the pilot during training sessions.

2. It can cause the pilot to adopt certain counterproductive behaviors to prevent symptoms from occurring.

Simulator sickness can also have post-training effects that can compromise safety after the simulator session, such as when the pilots drive away from the facility or fly while experiencing symptoms of simulator sickness.

The Simulator Sickness Questionnaire (SSQ) is currently the standard for measuring simulator sickness. The SSQ was developed based upon 1,119 pairs of pre-exposure/post-exposure scores from data that were collected and reported earlier. These data were collected from 10 Navy flight simulators representing both fixed-wing and rotary-wing aircraft. The simulators selected were both 6-DOF motion and fixed-base models, and also represented a variety of visual display technologies. The SSQ was developed and validated with data from pilots who reported to simulator training healthy and fit.

The SSQ is a self-report symptom checklist. It includes 16 symptoms that are associated with simulator sickness. Participants indicate the level of severity of the 16 symptoms that they are experiencing currently. For each of the 16 symptoms there are four levels of severity (none, slight, moderate, severe). The SSQ provides a Total Severity score as well as scores for three subscales (Nausea, Oculomotor, and Disorientation). The Total Severity score is a composite created from the three subscales. It is the best single measure because it provides an index of the overall symptoms. The three subscales provide diagnostic information about particular symptom categories:

- Nausea subscale is made up of symptoms such as increased salivation, sweating, nausea, stomach awareness, and burping.

- Oculomotor subscale includes symptoms such as fatigue, headache, eyestrain, and difficulty focusing.

- Disorientation subscale is composed of symptoms such as vertigo, dizzy (eyes open), dizzy (eyes closed), and blurred vision.

The three subscales are not orthogonal to one another. There is a general factor common to all of them. Nonetheless, the subscales provide differential information about participants' experience of symptoms and are useful for determining the particular pattern of discomfort produced by a given simulator. All scores have as their lowest level a natural zero (no symptoms) and increase with increasing symptoms reported.

Solipsism syndrome refers to a psychological state in which a person feels that the world is not external to his or her mind. Periods of extended isolation may predispose people to this condition. In particular, the syndrome has been identified as a potential concern for individuals living in outer space for extended periods of time.

This syndrome can begin with severe shoulder or arm pain followed by weakness and numbness. Those who suffer from Parsonage–Turner experience acute, sudden-onset pain radiating from the shoulder to the upper arm. Affected muscles become weak and atrophied, and in advanced cases, paralyzed. Occasionally, there will be no pain and just paralysis, and sometimes just pain, not ending in paralysis. MRI may assist in diagnosis. Scapular winging is commonly seen.

Parsonage-Turner involves neuropathy of the suprascapular nerve in 97% of cases, and variably involves the axillary and subscapular nerves. As such, the muscles usually involved are the supraspinatus and infraspinatus, which are both innervated by the suprascapular nerve. Involvement of the deltoid is more variable, as it is innervated by the axillary nerve.

Acrophobia (from the , "ákron", meaning "peak, summit, edge" and , "phóbos", "fear") is an extreme or irrational fear or phobia of heights, especially when one is not particularly high up. It belongs to a category of specific phobias, called space and motion discomfort, that share both similar causes and options for treatment.

Most people experience a degree of natural fear when exposed to heights, known as the fear of falling. On the other hand, those who have little fear of such exposure are said to have a head for heights. A head for heights is advantageous for those hiking or climbing in mountainous terrain and also in certain jobs e.g. steeplejacks or wind turbine mechanics.

Acrophobia sufferers can experience a panic attack in high places and become too agitated to get themselves down safely. Approximately 2–5% of the general population suffers from acrophobia, with twice as many women affected as men.

Limber tail syndrome, or acute caudal myopathy, is a disorder of the muscles in the tail, usually affecting working dogs.

It is an injury occurring mostly in sporting or working dogs such as English Pointers, English Setters, Foxhounds, Beagles, and Labrador Retrievers. Limber tail syndrome is also known as swimmer's tail, cold water tail, broken tail, dead tail, "happy tail" or broken wag.

It has been said by many dog owners that limber tail had been caused shortly (24 hours) after swimming in water that is too cold or on rare occasions too warm and indeed this has certainly produced this very condition. The actual cause is unknown but it may be caused by the narrowing of the space through which the spinal cord passes, typically due to degenerative change to the intervertebral disk spaces. These underlying changes may not lead to visible change until the problem is suddenly exacerbated, such as during physical activity, after trauma, etc. Occasionally other changes are seen prior to or in conjunction with limber tail disease, such as urinary or fecal incontinence, postural abnormalities in the pelvic limb, or pain in response to touching the lower back.

Individuals experiencing solipsism syndrome feel that the world is not 'real' in the sense of being external to their own minds. The syndrome is characterized by feelings of loneliness, detachment and indifference to the outside world. Solipsism syndrome is not currently recognized as a psychiatric disorder by the American Psychiatric Association, though it shares similarities with depersonalization disorder, which is recognized. Solipsism syndrome is distinct from solipsism, which is not a psychological state but rather a philosophical position, namely that nothing exists or can be known to exist outside of one's own mind; advocates of this philosophy do not necessarily suffer from solipsism syndrome, and sufferers do not necessarily subscribe to solipsism as a school of intellectual thought.

Periods of extended isolation may predispose people to solipsism syndrome. In particular, the syndrome has been identified as a potential challenge for astronauts and cosmonauts on long-term missions,

and these concerns influence the design of artificial habitats.

Differential considerations include similar rotator cuff denervation syndromes such as Parsonage–Turner syndrome, and compression of the suprascapular nerve at the spinoglenoid notch in which the infraspinatus, and to a lesser degree supraspinatus is involved.

If these symptoms are observed/experienced it is important to contact a physician specializing in sports medicine (MD/DO), a doctor of podiatric medicine (DPM), or other qualified health care professional immediately so as to get the appropriate advice/treatment before serious damage occurs.

The 5 Ps of Anterior Compartment Syndrome:

1. Pain

2. Pallor

3. Paresthesia

4. Pulselessness

5. Paralysis (If not treated)

Diagnosis is usually suspected by clinical history and confirmed by MRI, in which edema of the teres minor is seen, with variable involvement of the deltoid. The circumflex humeral artery may also be compressed. Before the advent of MRI, compression of this vessel on angiography used to be the mechanism of diagnosis, although this is no longer done as it is an invasive procedure.

Atrophy can occur in cases of chronic nerve impingement. It can be associated with a glenoid labral cyst, with the cyst also reflecting injury of the glenoid labrum.

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.

Barotrauma can affect the external, middle, or inner ear. Middle ear barotrauma (MEBT) is the most common being experienced by between 10% and 30% of divers and is due to insufficient equilibration of the middle ear. External ear barotrauma may occur on ascent if high pressure air is trapped in the external auditory canal either by tight fitting diving equipment or ear wax. Inner ear barotrauma (IEBT), though much less common than MEBT, shares a similar mechanism. Mechanical trauma to the inner ear can lead to varying degrees of conductive and sensorineural hearing loss as well as vertigo. It is also common for conditions affecting the inner ear to result in auditory hypersensitivity.

Diffuse tightness and tenderness over the entire belly of the tibialis anterior that does not respond to elevation or pain medication can be early warning signs and suggestive of Anterior Compartment Syndrome. Other common symptoms include excessive swelling that causes the skin to become hot, stretched and glossy. Pain, paresthesias, and tenderness in both the ischemic muscles and the region supplied by the deep common fibular nerve are exhibited by patients suffering from this condition. Sensitivity to passive stretch and active contraction are common, and tend to increase the symptoms.

Traditionally, acrophobia has been attributed, like other phobias, to conditioning or a traumatic experience. Recent studies have cast doubt on this explanation; a fear of falling, along with a fear of loud noises, is one of the most commonly suggested inborn or "non-associative" fears. The newer non-association theory is that a fear of heights is an evolved adaptation to a world where falls posed a significant danger. The degree of fear varies and the term phobia is reserved for those at the extreme end of the spectrum. Researchers have argued that a fear of heights is an instinct found in many mammals, including domestic animals and humans. Experiments using visual cliffs have shown human infants and toddlers, as well as other animals of various ages, to be reluctant in venturing onto a glass floor with a view of a few meters of apparent fall-space below it. While an innate cautiousness around heights is helpful for survival, an extreme fear can interfere with the activities of everyday life, such as standing on a ladder or chair, or even walking up a flight of stairs.

A possible contributing factor is a dysfunction in maintaining balance. In this case the anxiety is both well founded and secondary. The human balance system integrates proprioceptive, vestibular and nearby visual cues to reckon position and motion. As height increases, visual cues recede and balance becomes poorer even in normal people. However, most people respond by shifting to more reliance on the proprioceptive and vestibular branches of the equilibrium system.

An acrophobic, however, continues to over-rely on visual signals whether because of inadequate vestibular function or incorrect strategy. Locomotion at a high elevation requires more than normal visual processing. The visual cortex becomes overloaded resulting in confusion. Some proponents of the alternative view of acrophobia warn that it may be ill-advised to encourage acrophobics to expose themselves to height without first resolving the vestibular issues. Research is underway at several clinics.

The most common symptoms in impingement syndrome are pain, weakness and a loss of movement at the affected shoulder. The pain is often worsened by shoulder overhead movement and may occur at night, especially if the patient is lying on the affected shoulder. The onset of the pain may be acute if it is due to an injury or may be insidious if it is due to a gradual process such as an osteoarthritic spur. The pain has been described as dull rather than sharp, and lingers for long periods of a time, making it hard to fall asleep at night. Other symptoms can include a grinding or popping sensation during movement of the shoulder.

The range of motion at the shoulder may be limited by pain. A painful arc of movement may be present during forward elevation of the arm from 60° to 120°. Passive movement at the shoulder will appear painful when a downwards force is applied at the acromion but the pain will ease once the downwards force is removed.

Shift work sleep disorder (SWSD) is a circadian rhythm sleep disorder characterized by insomnia and excessive sleepiness affecting people whose work hours overlap with the typical sleep period. There are numerous shift work schedules, and they may be permanent, intermittent, or rotating; consequently, the manifestations of SWSD are quite variable.

Barotrauma is physical damage to body tissues caused by a difference in pressure between a gas space inside, or in contact with the body, and the surrounding gas or fluid. The initial damage is usually due to over-stretching the tissues in tension or shear, either directly by expansion of the gas in the closed space, or by pressure difference hydrostatically transmitted through the tissue. Tissue rupture may be complicated by the introduction of gas into the local tissue or circulation through the initial trauma site, which can cause blockage of circulation at distant sites, or interfere with normal function of an organ by its presence.

Barotrauma generally manifests as sinus or middle ear effects, decompression sickness (DCS), lung overpressure injuries, and injuries resulting from external squeezes.

Barotrauma typically occurs when the organism is exposed to a significant change in ambient pressure, such as when a scuba diver, a free-diver or an airplane passenger ascends or descends, or during uncontrolled decompression of a pressure vessel such as a diving chamber or pressurised aircraft, but can also be caused by a shock wave. Ventilator induced lung injury (VILI) is a condition caused by over-expansion of the lungs by mechanical ventilation used when the body is unable to breathe for itself, and is associated with relatively large tidal volumes and relatively high peak pressures. Barotrauma due to over-expansion of an internal gas filled space may also be termed volutrauma. Bats can be killed by lung barotrauma when flying in low pressure regions close to operating wind turbine blades.

A brainstem stroke syndrome is a condition involving a stroke of the brainstem. Because of their location, they often involve impairment both of the cranial nuclei and of the long tracts.

A person may have vertigo, dizziness and severe imbalance without the hallmark of most strokes – weakness on one side of the body. The symptoms of vertigo, dizziness or imbalance usually occur together; dizziness alone is not a sign of stroke. Brainstem stroke can also cause diplopia, slurred speech and decreased level of consciousness. A more serious outcome is locked-in syndrome.

Hyperacusis (or hyperacousis) is a debilitating hearing disorder characterized by an increased sensitivity to certain frequencies and volume ranges of sound (a collapsed tolerance to usual environmental sound). A person with severe hyperacusis has difficulty tolerating everyday sounds, some of which may seem unpleasantly or painfully loud to that person but not to others.

"Hyperacusis" is often coincident with tinnitus. Both conditions have a prevalence of about 10–15% and hearing loss as a major risk factor. However, there also appear to be important differences between the mechanisms involved in tinnitus and hyperacusis.

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.

In hyperacusis, the symptoms are ear pain, annoyance, and general intolerance to many sounds that most people are unaffected by. Crying spells or panic attacks may result from the experience of hyperacusis. It may affect either or both ears. Hyperacusis can also be accompanied by tinnitus. Hyperacusis can result in anxiety, stress and phonophobia. Avoidant behaviour is often a response to prevent the effects of hyperacusis and this can include avoiding social situations.