Diffuse axonal injury (DAI) is a brain injury in which damage in the form of extensive lesions in white matter tracts occurs over a widespread area. DAI is one of the most common and devastating types of traumatic brain injury, and is a major cause of unconsciousness and persistent vegetative state after severe head trauma. It occurs in about half of all cases of severe head trauma and may be the primary damage that occurs in concussion. The outcome is frequently coma, with over 90% of patients with severe DAI never regaining consciousness. Those who do wake up often remain significantly impaired.

DAI can occur in every degree of severity from very mild or moderate to very severe. Concussion may be a milder type of diffuse axonal injury.

DAI is the result of traumatic shearing forces that occur when the head is rapidly accelerated or decelerated, as may occur in car accidents, falls, and assaults. Vehicle accidents are the most frequent cause of DAI; it can also occur as the result of child abuse such as in shaken baby syndrome.

Immediate disconnection of axons could be observed in severe brain injury, but the major damage of DAI is delayed secondary axon disconnections slowly developed over an extended time course. Tracts of axons, which appear white due to myelination, are referred to as white matter. Lesions in both grey and white matters are found in postmortem brains in CT and MRI exams.

Besides mechanical breaking of the axonal cytoskeleton, DAI pathology also includes secondary physiological changes such as interrupted axonal transport, progressive swellings and degeneration. Recent studies have linked these changes to twisting and misalignment of broken axon microtubules, as well as tau and APP deposition.

Diffuse axonal injury, or DAI, usually occurs as the result of an acceleration or deceleration motion, not necessarily an impact. Axons are stretched and damaged when parts of the brain of differing density slide over one another. Prognoses vary widely depending on the extent of damage.

Presentation varies according to the injury. Some patients with head trauma stabilize and other patients deteriorate. A patient may present with or without neurological deficit. Patients with concussion may have a history of seconds to minutes unconsciousness, then normal arousal. Disturbance of vision and equilibrium may also occur. Common symptoms of head injury include coma, confusion, drowsiness, personality change, seizures, nausea and vomiting, headache and a lucid interval, during which a patient appears conscious only to deteriorate later.

Symptoms of skull fracture can include:

- leaking cerebrospinal fluid (a clear fluid drainage from nose, mouth or ear) may be and is strongly indicative of basilar skull fracture and the tearing of sheaths surrounding the brain, which can lead to secondary brain infection.

- visible deformity or depression in the head or face; for example a sunken eye can indicate a maxillar fracture

- an eye that cannot move or is deviated to one side can indicate that a broken facial bone is pinching a nerve that innervates eye muscles

- wounds or bruises on the scalp or face.

- Basilar skull fractures, those that occur at the base of the skull, are associated with Battle's sign, a subcutaneous bleed over the mastoid, hemotympanum, and cerebrospinal fluid rhinorrhea and otorrhea.

Because brain injuries can be life-threatening, even people with apparently slight injuries, with no noticeable signs or complaints, require close observation; They have a chance for severe symptoms later on. The caretakers of those patients with mild trauma who are released from the hospital are frequently advised to rouse the patient several times during the next 12 to 24 hours to assess for worsening symptoms.

The Glasgow Coma Scale (GCS) is a tool for measuring degree of unconsciousness and is thus a useful tool for determining severity of injury. The Pediatric Glasgow Coma Scale is used in young children. The widely used PECARN Pediatric Head Injury/Trauma Algorithm helps physicians weigh risk-benefit of imaging in a clinical setting given multiple factors about the patient—including mechanism/location of injury, age of patient, and GCS score.

Symptoms most frequently reported include a persistent sensation of motion usually described as rocking, swaying, or bobbing, disequilibrium with difficulty maintaining balance; it is seldom accompanied by a true spinning vertigo. Chronically fatigued, sufferers can become fatigued quickly with minimal exertion and experience neck and back pain. Other common symptoms include difficulty concentrating or inability to multitask, visual intolerance of busy patterns, headaches and/or migraine headaches, and ear pain or fullness.

Fluctuations in weather, in particular barometric pressure, also affect suffers. Many have photo-sensitivity and find it more difficult to walk in the dark as well as other sensitivities to strong smells including chemical smells. Cognitive impairment ("brain fog") includes an inability to recall words, short term memory loss, an inability to multi-task, misspelling and mispronunciation of words. MdDS sufferers report they are unable to use a computer for any length of time due to the visual overstimulation, and some are even unable to watch television.

The condition may be masked by a return to motion such as in a car, train, plane, or boat; however, once the motion ceases, the symptoms rebound or return, often at much higher levels than when the journey first commenced. Symptoms can be increased by stress, lack of sleep, crowds, flickering lights, loud sounds, fast or sudden movements, enclosed areas or busy patterns.

MdDS sufferers can sleep up to 12 or more hours a day, depending on their symptom levels. Research reveals MdDS is not migraine related and many sufferers have never had migraine symptoms prior to the onset of the disorder. However, for some MdDS sufferers there maybe have been a correlation between migraine and some pathophysiological overlap or even some other precipitating illness.

The symptoms of MdDS may be extremely debilitating and fluctuate high and low on a daily basis; it greatly affects the working capacity of sufferers with many having to relinquish work; it also limits most other daily and social activities. Sufferers can have low quality of life in both the physical and emotional realms, comparable to people who have multiple sclerosis.

Mal de debarquement (or mal de débarquement) syndrome (MdDS, or common name disembarkment syndrome) is a neurological condition usually occurring after a cruise, aircraft flight, or other sustained motion event. The phrase "mal de débarquement" is French for "sickness from disembarkation".

MdDS is typically diagnosed by a neurologist or an ear nose & throat specialist when a person reports a persistent rocking, swaying, or bobbing feeling (though they are not necessarily rocking). This usually follows a cruise or other motion experience. Because most vestibular testing proves to be negative, doctors may be baffled as they attempt to diagnose the syndrome. A major diagnostic indicator is that most patients feel better while driving or riding in a car, i.e.: while in passive motion. MdDS is unexplained by structural brain or inner ear pathology and most often corresponds with a motion trigger, although it can occur spontaneously. This differs from the very common condition of "land sickness" that most people feel for a short time after a motion event such as a boat cruise, aircraft ride, or even a treadmill routine which may only last minutes to a few hours. The syndrome has recently received increased attention due to the number of people presenting with the condition and more scientific research has commenced to determine what triggers MdDS and how to cure it.

Reactive attachment disorder (RAD) is described in clinical literature as a severe and relatively uncommon disorder that can affect children. RAD is characterized by markedly disturbed and developmentally inappropriate ways of relating socially in most contexts. It can take the form of a persistent failure to initiate or respond to most social interactions in a developmentally appropriate way—known as the "inhibited form". Due to recent revision in the DSM-5 the "disinhibited form" is now considered a separate diagnosis named "Disinhibited attachment disorder".

RAD arises from a failure to form normal attachments to primary caregivers in early childhood. Such a failure could result from severe early experiences of neglect, abuse, abrupt separation from caregivers between the ages of six months and three years, frequent change of caregivers, or a lack of caregiver responsiveness to a child's communicative efforts. Not all, or even a majority of such experiences, result in the disorder. It is differentiated from pervasive developmental disorder or developmental delay and from possibly comorbid conditions such as intellectual disability, all of which can affect attachment behavior. The criteria for a diagnosis of a reactive attachment "disorder" are very different from the criteria used in assessment or categorization of attachment "styles" such as insecure or disorganized attachment.

Children with RAD are presumed to have grossly disturbed internal working models of relationships that may lead to interpersonal and behavioral difficulties in later life. There are few studies of long-term effects, and there is a lack of clarity about the presentation of the disorder beyond the age of five years. However, the opening of orphanages in Eastern Europe following the end of the Cold War in the early-1990s provided opportunities for research on infants and toddlers brought up in very deprived conditions. Such research broadened the understanding of the prevalence, causes, mechanism and assessment of disorders of attachment and led to efforts from the late-1990s onwards to develop treatment and prevention programs and better methods of assessment. Mainstream theorists in the field have proposed that a broader range of conditions arising from problems with attachment should be defined beyond current classifications.

Mainstream treatment and prevention programs that target RAD and other problematic early attachment behaviors are based on attachment theory and concentrate on increasing the responsiveness and sensitivity of the caregiver, or if that is not possible, placing the child with a different caregiver. Most such strategies are in the process of being evaluated. Mainstream practitioners and theorists have presented significant criticism of the diagnosis and treatment of alleged reactive attachment disorder or the theoretically baseless "attachment disorder" within the controversial form of psychotherapy commonly known as attachment therapy. Attachment therapy has a scientifically unsupported theoretical base and uses diagnostic criteria or symptom lists markedly different to criteria under ICD-10 or DSM-IV-TR, or to attachment behaviors. A range of treatment approaches are used in attachment "therapy", some of which are physically and psychologically coercive, and considered to be to attachment "theory". Many constitute abuse.

Pediatricians are often the first health professionals to assess and raise suspicions of RAD in children with the disorder. The initial presentation varies according to the child's developmental and chronological age, although it always involves a disturbance in social interaction. Infants up to about 18–24 months "may" present with non-organic failure to thrive and display abnormal responsiveness to stimuli. Laboratory investigations will be unremarkable barring possible findings consistent with malnutrition or dehydration, while serum growth hormone levels will be normal or elevated.

The core feature is severely inappropriate social relating by affected children. This can manifest itself in two ways:

1. Indiscriminate and excessive attempts to receive comfort and affection from any available adult, even relative strangers (older children and adolescents may also aim attempts at peers).

2. Extreme reluctance to initiate or accept comfort and affection, even from familiar adults, especially when distressed.

While RAD is likely to occur in relation to neglectful and abusive treatment, automatic diagnoses on this basis alone cannot be made, as children can form stable attachments and social relationships despite marked abuse and neglect.

The name of the disorder emphasizes problems with attachment but the criteria includes symptoms such as failure to thrive, a lack of developmentally appropriate social responsiveness, apathy, and onset before 8 months.

Attachment disorder is a broad term intended to describe disorders of mood, behavior, and social relationships arising from a failure to form normal attachments to primary care giving figures in early childhood. Such a failure would result from unusual early experiences of neglect, abuse, abrupt separation from caregivers between 6 months and three years of age, frequent change or excessive numbers of caregivers, or lack of caregiver responsiveness to child communicative efforts resulting in a lack of basic trust. A problematic history of social relationships occurring after about age three may be distressing to a child, but does not result in attachment disorder.

The term attachment disorder is used to describe emotional and behavioral problems of young children, and also applied to school-age children, teenagers and adults. The specific difficulties implied depend on the age of the individual being assessed, and a child's attachment-related behaviors may be very different with one familiar adult than with another, suggesting that the disorder is within the relationship and interactions of the two people rather than an aspect of one or the other personality. No list of symptoms can legitimately be presented but generally the term attachment disorder refers to the absence or distortion of age appropriate social behaviors with adults. For example, in a toddler, attachment-disordered behavior could include a failure to stay near familiar adults in a strange environment or to be comforted by contact with a familiar person, whereas in a six-year-old attachment-disordered behavior might involve excessive friendliness and inappropriate approaches to strangers.

There are currently two main areas of theory and practice relating to the definition and diagnosis of attachment disorder, and considerable discussion about a broader definition altogether. The first main area is based on scientific enquiry, is found in academic journals and books and pays close attention to attachment theory. It is described in ICD-10 as reactive attachment disorder, or "RAD" for the inhibited form, and disinhibited attachment disorder, or "DAD" for the disinhibited form. In DSM-IV-TR both comparable inhibited and disinhibited types are called reactive attachment disorder or "RAD".

The second area is controversial and considered pseudoscientific. It is found in clinical practice, on websites and in books and publications, but has little or no evidence base. It makes controversial claims relating to a basis in attachment theory. The use of these controversial diagnoses of attachment disorder is linked to the use of pseudoscientific attachment therapies to treat them.

Some authors have suggested that attachment, as an aspect of emotional development, is better assessed along a spectrum than considered to fall into two non-overlapping categories. This spectrum would have at one end the characteristics called secure attachment; midway along the range of disturbance would be insecure or other undesirable attachment styles; at the other extreme would be

non-attachment. Agreement has not yet been reached with respect to diagnostic criteria.

Finally, the term is also sometimes used to cover difficulties arising in relation to various attachment styles which may not be disorders in the clinical sense.

ICD-10 describes Reactive Attachment Disorder of Childhood, known as RAD, and Disinhibited Disorder of Childhood, less well known as DAD. DSM-IV-TR also describes Reactive Attachment Disorder of Infancy or Early Childhood. It divides this into two subtypes, Inhibited Type and Disinhibited Type, both known as RAD. The two classifications are similar and both include:

- markedly disturbed and developmentally inappropriate social relatedness in most contexts,

- the disturbance is not accounted for solely by developmental delay and does not meet the criteria for Pervasive Developmental Disorder,

- onset before 5 years of age,

- requires a history of significant neglect, and

- implicit lack of identifiable, preferred attachment figure.

ICD-10 includes in its diagnosis psychological and physical abuse and injury in addition to neglect. This is somewhat controversial, being a "commission" rather than "omission" and because abuse in and of itself does not lead to attachment disorder.

The inhibited form is described as "a failure to initiate or respond...to most social interactions, as manifest by excessively inhibited responses" and such infants do not seek and accept comfort at times of threat, alarm or distress, thus failing to maintain 'proximity', an essential element of attachment behavior. The disinhibited form shows "indiscriminate sociability...excessive familiarity with relative strangers" (DSM-IV-TR) and therefore a lack of 'specificity', the second basic element of attachment behavior. The ICD-10 descriptions are comparable. 'Disinhibited' and 'inhibited' are not opposites in terms of attachment disorder and can co-exist in the same child. The inhibited form has a greater tendency to ameliorate with an appropriate caregiver whilst the disinhibited form is more enduring.

While RAD is likely to occur following neglectful and abusive childcare, there should be no automatic diagnosis on this basis alone as children can form stable attachments and social relationships despite marked abuse and neglect. Abuse can occur alongside the required factors but on its own does not explain attachment disorder. Experiences of abuse are associated with the development of disorganised attachment, in which the child prefers a familiar caregiver, but responds to that person in an unpredictable and somewhat bizarre way. Within official classifications, attachment disorganization is a risk factor but not in itself an attachment disorder. Further although attachment disorders tend to occur in the context of some institutions, repeated changes of primary caregiver or extremely neglectful identifiable primary caregivers who show persistent disregard for the child's basic attachment needs, not all children raised in these conditions develop an attachment disorder.

In Chinese alchemy, elixir poisoning refers to the toxic effects from elixirs of immortality that contained metals and minerals such as mercury and arsenic. The official "Twenty-Four Histories" record numerous Chinese emperors, nobles, and officials who ironically died from taking elixirs in order to prolong their lifespans. The first emperor to die from elixir poisoning was likely Qin Shi Huang (d. 210 BCE) and the last was Yongzheng (d. 1735). Despite common knowledge that immortality potions could be deadly, fangshi and Daoist alchemists continued the elixir-making practice for two millennia.

The etymology of English elixir derives from Medieval Latin "", from Arabic ("al-ʾiksīr"), probably from Ancient Greek ("xḗrion" "a desiccative powder for wounds"). "Elixir" originated in medieval European alchemy meaning "A preparation by the use of which it was sought to change metals into gold" (elixir stone or philosopher's stone) or "A supposed drug or essence with the property of indefinitely prolonging life" (elixir of life). The word was figuratively extended to mean "A sovereign remedy for disease. Hence adopted as a name for quack medicines" (e.g., Daffy's Elixir) and "The quintessence or soul of a thing; its kernel or secret principle". In modern usage, "elixir" is a pharmaceutical term for "A sweetened aromatic solution of alcohol and water, serving as a vehicle for medicine" ("Oxford English Dictionary", 2nd ed., 2009). Outside of Chinese cultural contexts, English "elixir poisoning" usually refers to accidental contamination, such as the 1937 Elixir sulfanilamide mass poisoning in the United States.

"Dān" 丹 "cinnabar; vermillion; elixir; alchemy" is the keyword for Chinese immortality elixirs. The red mineral cinnabar ("dānshā" 丹砂 lit. "cinnabar sand") was anciently used to produce the pigment vermilion ("zhūhóng" 朱紅) and the element mercury ("shuǐyín" 水銀 "watery silver" or "gǒng" 汞).

According to the "ABC Etymological Dictionary of Old Chinese", the etymology of Modern Standard Chinese "dān" from Old Chinese "*tān" (< *"tlan" ?) 丹 "red; vermillion; cinnabar", "gān" 矸 in "dāngān" 丹矸 from *"tân-kân" (< *"tlan-klan" ?) "cinnabar; vermillion ore", and "zhān" from *"tan" 旃 "a red flag" derive from Proto-Kam-Sui *"h-lan" "red" or Proto-Sino-Tibetan *"tja-n" or *"tya-n" "red". The *"t-" initial and *"t-" or *"k-" doublets indicate that Old Chinese borrowed this item. (Schuessler 2007: 204).

Although the word "dan" 丹 "cinnabar; red" frequently occurs in oracle script from the late Shang Dynasty (ca. 1600-1046 BCE) and bronzeware script and seal script from the Zhou Dynasty (1045-256 BCE), paleographers disagree about the graphic origins of the logograph 丹 and its ancient variants 𠁿 and 𠕑. Early scripts combine a 丶 dot or ⼀ stroke (depicting a piece of cinnabar) in the middle of a surrounding frame, which is said to represent:

- "jǐng" 井 "well" represents the mine from which the cinnabar is taken" ("Shuowen Jiezi")

- "the crucible of the Taoist alchemists" (Léon Wieger )

- "the contents of a square receptacle" (Bernhard Karlgren)

- "placed in a tray or palette to be used as red pigment" (Wang Hongyuan 王宏源)

- "mineral powder on a stretched filter-cloth" (Needham and Lu).

Many Chinese elixir names are compounds of "dan", such as "jīndān" 金丹 (with "gold") meaning "golden elixir; elixir of immortality; potable gold" and "xiāndān" 仙丹 (with "Daoist immortal") "elixir of immortality; panacea", and "shéndān" 神丹 (with "spirit; god") "divine elixir". "Bùsǐ zhī yào" 不死之藥 "drug of deathlessness" was another early name for the elixir of immortality. Chinese alchemists would "liàndān" 煉丹 (with "smelt; refine") "concoct pills of immortality" using a "dāndǐng" 丹鼎 (with "tripod cooking vessel; cauldron") "furnace for concocting pills of immortality". In addition, the ancient Chinese believed that other substances provided longevity and immortality, notably the "língzhī" 靈芝 ""Ganoderma" mushroom".

The transformation from chemistry-based "waidan" 外丹 "external elixir/alchemy" to physiology-based "neidan" 內丹 "internal elixir/alchemy" gave new analogous meanings to old terms. The human body metaphorically becomes a "ding" "cauldron" in which the adept forges the Three Treasures (essence, life-force, and spirit) within the "jindan" Golden Elixir within the "dāntián" 丹田 (with "field") "lower part of the abdomen".

In early China, alchemists and pharmacists were one in the same. Traditional Chinese Medicine also used less concentrated cinnabar and mercury preparations, and "dan" means "pill; medicine" in general, for example, "dānfāng" 丹方 semantically changed from "prescription for elixir of immortality" to "medical prescription". "Dan" was lexicalized into medical terms such as " dānjì" 丹劑 "pill preparation" and "dānyào" 丹藥 "pill medicine".

The Chinese names for immortality elixirs have parallels in other cultures and languages, for example, Indo-Iranian "soma" or "haoma", Sanskrit "amrita", and Greek "ambrosia".

The distinction between Hua () and Yi (), also known as Sino–barbarian dichotomy, is an ancient Chinese concept that differentiated a culturally defined "China" (called Hua, Huaxia 華夏, or Xia 夏) from cultural or ethnic outsiders (Yi "barbarians"). Although Yi is often translated as "barbarian", other translations of this term in English include "foreigners",

"ordinary others" "wild tribes", and "uncivilized tribes."

The Hua–Yi distinction asserted Chinese superiority, but implied that outsiders could become "Hua" by adopting Chinese values and customs.

Ancient China was composed of a group of states that arose in the Yellow River valley. According to historian Li Feng, during the Zhou dynasty (ca. 1041–771 BCE), the contrast between the 'Chinese' Zhou and the 'non-Chinese' Xirong or Dongyi was "more political than cultural or ethnic". Lothar von Falkenhausen argues that the perceived contrast between "Chinese" and "Barbarians" was accentuated during the Eastern Zhou period (770–256 BCE), when adherence to Zhou rituals became increasingly recognized as a "barometer of civilization."; a meter for sophistication and cultural refinement. It is widely agreed by historians that the distinction between the Hua and the Yi emerged during that period.

Gideon Shelach claimed that Chinese texts tended to overstate the distinction between the Chinese and their northern neighbors, ignoring many intergroup similarities. He doubted the existence of the Hua–Yi distinction. Nicola di Cosmo doubted the existence of a strong demarcation between the "Zhou Universe" and "a discrete, 'barbarian', non-Zhou universe" and claimed that Chinese historian, Sima Qian's popularized this concept, writing of the "chasm that had always existed between China – the Hua-Hsia [Huaxia] people – and the various alien groups inhabiting the north."

The conclusion of the Warring States period brought the first unified Chinese state-established by the Qin dynasty in 221 BCE-who established the imperial system and forcibly standardized the traditional Chinese script, leading to the first of the distinctions between the refined Hua and the increasingly marginalized Yi. The Han dynasty (221 BCE-206 CE) further contributed to the divide with its creation of a persistent Han cultural identity.

The Han Chinese civilization influenced neighboring states Korea, Japan, Vietnam and Thailand and other Asian countries. Although Han Chinese superiority had only been sporadically reinforced by displays of Chinese military power, the Sinocentric system treated these countries as vassals of the emperor of China, literally "the Son of Heaven" (天子), who was in possession of the Mandate of Heaven (天命), the divine right to rule. Areas outside Sinocentric influence and the divine rule of the Emperor were considered to consist of uncivilized lands inhabited by barbarians.

Throughout history, Chinese frontiers had been periodically attacked by nomadic tribes from the north and west. These people were considered "barbarians" by the Chinese who believed themselves to be more refined and who had begun to build cities and live an urban life based on agriculture. It was in consideration of how best to deal with this threat that the philosopher, Confucius (551 – 479 BCE) was prompted to formulate principles for relationships with the barbarians, briefly recorded in two of his "Analects".

The arrival of European trade and colonialism in the 18th and 19th centuries, exposed Chinese civilization to the developments that had long outstripped China's. As such, the nation was forced to undergo a modification of its traditional views of its relationships with those "barbarians".