The risk of awareness is reduced by avoidance of paralytics unless necessary; careful checking of drugs, doses and equipment; good monitoring, and careful vigilance during the case. The Isolated Forearm Technique (IFT) can be used to monitor consciousness; the technique involves applying a tourniquet to the patient's upper arm before the administration of muscle relaxants, so that the forearm can still be moved consciously. The technique is considered a reference standard by which other means of assessing consciousness can be assessed.

The incidence of anesthesia awareness is higher and has more serious sequelae when muscle relaxants or neuromuscular-blocking drugs are used. This is because without relaxant the patient will move and the anesthesiologist will deepen the anesthesia.

One study has indicated this phenomenon occurs in about 1 or 2 per 1000 patients or 0.13%. There is conflicting data however as another study suggested it is a rare phenomenon, with an incidence of 0.0068% after review of their data from a patient population of 211,842 patients.

Post operative interview by an anesthetist is common practice to elucidate if awareness occurred in the case. If awareness is reported a case review is immediately performed to identify machine, medication, or operator error.

Metabolic studies are useful, but they are not able identify neural activity within a specific region to specific cognitive processes. Functionality can only be identified at the most general level: Metabolism in cortical and subcortical regions that may contribute to cognitive processes.

At present, there is no established relation between cerebral metabolic rates of glucose or oxygen as measured by PET and patient outcome. The decrease of cerebral metabolism occurs also when patients are treated with anesthetics to the point of unresponsiveness. Lowest value (28% of normal range) have been reported during propofol anesthesia. Also deep sleep represents a phase of decreased metabolism (down to 40% of the normal range)

In general, quantitative PET studies and the assessment of cerebral metabolic rates depends on many assumptions.

PET for example requires a correction factor, the lumped constant, which is stable in healthy brains. There are reports, that a global decrease of this constant emerges after a traumatic brain injury.

But not only the correction factors change due to TBI.

Another issue is the possibility of anaerobic glycolysis that could occur after TBI. In such a case the glucose levels measured by the PET are not tightly connected to the oxygen consumption of the patient's brain.

Third point regarding PET scans is the overall measurement per unit volume of brain tissue. The imaging can be affected by the inclusion of metabolically inactive spaces e.g. cerebrospinal fluidin the case of gross hydrocephalus, which artificially lowers the calculated metabolism.

Also the issue of radiation exposure must be considered in patients with already severely damaged brains and preclude longitudinal or follow-up studies.

Although MCS patients are able to demonstrate cognitively mediated behaviors, they occur inconsistently. They are, however, reproducible or can be sustained long enough to be differentiated from reflexive behavior. Because of this inconsistency, extended assessment may be required to determine if a simple response (e.g. a finger movement or a blink) occurred because of a specific environmental event (e.g. a command to move the finger or to blink) or was merely a coincidental behavior. Distinguishing between VS and MCS is often difficult because the diagnosis is dependent on observation of behavior that show self or environmental awareness and because those behavioral responses are markedly reduced. One of the more common diagnostic errors involving disorders of consciousness is mistaking MCS for VS which may lead to serious repercussions related to clinical management.

Giacino et al. have suggested demonstration of the following behaviors in order to make the diagnosis of MCS.

- Following simple commands.

- Gestural or verbal yes/no responses (regardless of accuracy).

- Intelligible verbalization.

- Purposeful behavior such as those that are contingent due to appropriate environmental stimuli and are not reflexive. Some examples of purposeful behavior include:

- appropriate smiling or crying in response to the linguistic or visual content of emotional but not to neutral topics or stimuli.

- vocalizations or gestures that occur in direct response to the linguistic content of questions.

- reaching for objects that demonstrates a clear relationship between object location and direction of reach.

- touching or holding objects in a manner that accommodates the size and shape of the object.

- pursuit eye movement or sustained fixation that occurs in direct response to moving or salient stimuli.

One of the defining characteristics of minimally conscious state is the more continuous improvement and significantly more favorable outcomes post injury when compared with vegetative state. One study looked at 100 patients with severe brain injury. At the beginning of the study, all the patients were unable to follow commands consistently or communicate reliably. These patients were diagnosed with either MCS or vegetative state based on performance on the JFK Coma Recovery Scale and the diagnostic criteria for MCS as recommended by the Aspen Consensus Conference Work-group. Both patient groups were further separated into those that suffered from traumatic brain injury and those that suffered from non-traumatic brain injures (anoxia, tumor, hydrocephalus, infection). The patients were assessed multiple times over a period of 12 months post injury using the Disability Rating Scale (DRS) which ranges from a score of 30=dead to 0=no disabilities. The results show that the DRS scores for the MCS subgroups showed the most improvement and predicted the most favorable outcomes 12 months post injury. Amongst those diagnosed with MCS, DRS scores were significantly lower for those with non-traumatic brain injuries in comparison to the vegetative state patients with traumatic brain injury. DRS scores were also significantly lower for the MCS non-traumatic brain injury group compared to the MCS traumatic brain injury group. Pairwise comparisons showed that DRS scores were significantly higher for those that suffered from non-tramuatic brain injuries than those with traumatic brain injuries. For the patients in vegetative states there were no significant differences between patients with non-traumatic brain injury and those with traumatic brain injuries. Out of the 100 patients studied, 3 patients fully recovered (had a DRS score of 0). These 3 patients were diagnosed with MCS and had suffered from traumatic brain injuries.

In summary, those with minimally conscious state and non-traumatic brain injuries will not progress as well as those with traumatic brain injuries while those in vegetative states have an all around lower to minimal chance of recovery.

Because of the major differences in prognosis described in this study, this makes it crucial that MCS be diagnosed correctly. Incorrectly diagnosing MCS as vegetative state may lead to serious repercussions related to clinical management.

Brain death is the irreversible end of all brain activity, and function (including involuntary activity necessary to sustain life). The main cause is total necrosis of the cerebral neurons following loss of brain oxygenation. After brain death the patient lacks any sense of awareness; sleep-wake cycles or behavior, and typically look as if they are dead or are in a deep sleep-state or coma. Although visually similar to a comatose state such as persistent vegetative state, the two should not be confused. Criteria for brain death differ from country to country. However, the clinical assessments are the same and require the loss of all brainstem reflexes and the demonstration of continuing apnea in a persistently comatose patient (< 4 weeks).

Functional imaging using PET or CT scans, typically show a hollow skull phenomenon. This confirms the absence of neuronal function in the whole brain.

Patients classified as brain dead are legally dead and can qualify as organ donors, in which their organs are surgically removed and prepared for a particular recipient.

Brain death is one of the deciding factors when pronouncing a trauma patient as dead. Determining function and presence of necrosis after trauma to the whole brain or brain-stem may be used to determine brain death, and is used in many states in the US.

Misdiagnosis of PVS is not uncommon. One study of 40 patients in the United Kingdom reported that 43% of those patients classified as in a PVS were misdiagnosed and another 33% able to recover whilst the study was underway. Some cases of PVS may actually be cases of patients being in an undiagnosed minimally conscious state. Since the exact diagnostic criteria of the minimally conscious state were formulated only in 2002, there may be chronic patients diagnosed as PVS before the notion of the minimally conscious state became known.

Whether or not there is conscious awareness in vegetative state is a prominent issue. Three completely different aspects of this issue should be distinguished. First, some patients can be conscious simply because they are misdiagnosed (see above). In fact, they are not in vegetative state. Second, sometimes a patient was correctly diagnosed but is then examined during the early stages of recovery. Third, perhaps some day the very notion of the vegetative state will change so as to include elements of conscious awareness. Inability to disentangle these three cases leads to confusion. An example of such confusion is the response to a recent experiment using functional magnetic resonance imaging which revealed that a woman diagnosed with PVS was able to activate predictable portions of her brain in response to the tester's requests that she imagine herself playing tennis or moving from room to room in her house. The brain activity in response to these instructions was indistinguishable from those of healthy patients.

In 2010, Martin Monti and fellow researchers, working at the MRC Cognition and Brain Sciences Unit at the University of Cambridge, reported in an article in the "New England Journal of Medicine" that some patients in persistent vegetative states responded to verbal instructions by displaying different patterns of brain activity on fMRI scans. Five out of a total of 54 diagnosed patients were apparently able to respond when instructed to think about one of two different physical activities. One of these five was also able to "answer" yes or no questions, again by imagining one of these two activities. It is unclear, however, whether the fact that portions of the patients' brains light up on fMRI could help these patients assume their own medical decision making.

In November 2011, a publication in "The Lancet" presented bedside EEG apparatus and indicated that its signal could be used to detect awareness in three of 16 patients diagnosed in the vegetative state.

There is limited evidence that the hypnotic drug zolpidem has an effect. The results of the few scientific studies that have been published so far on the effectiveness of zolpidem have been contradictory.

The body's inflammatory response to surgery likely plays an important role, at least in elderly patients. Various research initiatives during recent years have evaluated whether actions taken before, during and after surgery can lessen the possible deleterious effects of inflammation. For example, anti-inflammatory agents can be given before surgery. During surgery, inflammation can be modulated by temperature control, use of regional rather than general anesthesia or the use of beta blockers. After surgery, optimal pain management and infection control is important. Several studies have shown variable-significance positive effects when a multidisciplinary, multifactorial approach to elderly patient is followed during pre, peri and post-operative care.

Animal studies indicate that volatile anaesthestics may augment the pathological processes of Alzheimer's Disease by affecting amyloid-beta processing. However, in young healthy mice, the volatile anesthetic isoflurane can also produce long-lasting memory impairment. This adverse effect is preventable by pre-administering the GABA(A)α5 inverse agonist L-655,708.

POCD is common after cardiac surgery, and recent studies have now verified that POCD also exists after major non-cardiac surgery, although at a lower incidence. The risk of POCD increases with age, and the type of surgery is also important because there is a very low incidence associated with minor surgery. POCD is common in adult patients of all ages at hospital discharge after major noncardiac surgery, but only the elderly (aged 60 years or older) are at significant risk for long-term cognitive problems. Patients with POCD are at an increased risk of death in the first year after surgery. Research interest has increased since early 2000, especially as more elderly patients are able to undergo successful minor and major surgeries.

POCD has been studied through various institutions since the inception of the IPOCDS-I study centred in Eindhoven, Netherlands and Copenhagen, Denmark. This study found no causal relationship between cerebral hypoxia and low blood pressure and POCD. Age, duration of anaesthesia, introperative complications, and postoperative infections were found to be associated with POCD.

- POCD is just as likely to occur after operations under regional anesthesia as under general anesthesia.

- More likely after major operations than minor operations.

- More likely after heart operations than other types of surgery.

- More likely in aged than in younger patients.

- More likely in older patients with high alcohol intake/abuse.

- People with higher preoperative ASA physical status scores are more likely to develop POCD.

- People with lower educational level are more likely to develop POCD than those with a higher educational level.

- People with prior history of a stroke, even though there is complete functional recovery, are more likely to develop POCD.

- More likely in the elderly with pre-existing declining mental functions, termed mild cognitive impairment (MCI). MCI is a transitional zone between normal mental function and evident Alzheimer's disease or other forms of dementia. It is insidious, and seldom recognized, except in retrospect after affected persons are evidently demented.

- Delirium and severe worsening of mental function is very likely in those with clinically evident Alzheimer's disease or other forms of dementia, as well as those with a history of delirium after previous operations.

Expensive and invasive, the above treatments are not guaranteed to work, and are not meeting the needs of patients. There is a need for a new, less expensive, less invasive form of treatment, two of which are postulated below.

- Spinal cord stimulation has been studied in the last couple of years. In a long case study, 8 patients were given spinal cord stimulation via insertion of a percutaneous lead at the appropriate level of the cervical or thoracic spine. Between 36 and 149 months after the stimulations, the patients were interviewed. 6 of the 8 had received initial pain relief, and three experienced long-term pain relief. Spinal cord stimulation is cheaper than brain stimulation and less invasive, and is thus a more promising option for pain treatment.

- In 2007, Dr. V. S. Ramachandran and his lab proposed that caloric stimulation might be effective in treating Dejerine–Roussy syndrome. They hypothesized that if cold water was streamed into the ear down the auditory canal, the symptoms associated with Dejerine–Roussy syndrome would be alleviated. Ramachandran stated that he had carried out provisional experiments on two patients and believed that their reactions supported his theory.

Dejerine-Roussy is a rare pain syndrome. Individuals with emerging Dejerine–Roussy syndrome usually report they are experiencing unusual pain or sensitivity that can be allodynic in nature or triggered by seemingly unrelated stimuli (sounds, tastes). Symptoms are typically lateralized and may include vision loss or loss of balance (position sense). Workup should be performed by a neurologist and brain imaging to look for evidence of infarction or tumor should be obtained.

Experiences - are characterized by the presence of the following three factors:

- disembodiment, an apparent location of the self outside one's body;

- impression of seeing the world from an elevated and distanced visuo-spatial perspective or extracorporeal, but egocentric visuo-spatial perspective;

- impression of seeing one's own body from this perspective (autoscopy).

Laboratory of Cognitive Neuroscience, École Polytechnique Fédérale de Lausanne, Lausanne, and Department of Neurology, University Hospital, Geneva, Switzerland, have reviewed some of the classical precipitating factors of autoscopy. These are sleep, drug abuse, and general anesthesia as well as neurobiology. They have compared them with recent findings on neurological and neurocognitive mechanisms of the autoscopy. The reviewed data suggest that autoscopic experiences are due to functional disintegration of lower-level multisensory processing and abnormal higher-level self-processing at the temporoparietal junction.

Clinically, anosognosia is often assessed by giving patients an anosognosia questionnaire in order to assess their metacognitive knowledge of deficits. However, neither of the existing questionnaires applied in the clinics are designed thoroughly for evaluating the multidimensional nature of this clinical phenomenon; nor are the responses obtained via offline questionnaire capable of revealing the discrepancy of awareness observed from their online task performance. The discrepancy is noticed when patients showed no awareness of their deficits from the offline responses to the questionnaire but demonstrated reluctance or verbal circumlocution when asked to perform an online task. For example, patients with anosognosia for hemiplegia may find excuses not to perform a bimanual task even though they do not admit it is because of their paralyzed arms.

A similar situation can happen on patients with anosognosia for cognitive deficits after traumatic brain injury when monitoring their errors during the tasks regarding their memory and attention (online emergent awareness) and when predicting their performance right before the same tasks (online anticipatory awareness). It can also occur among patients with dementia and anosognosia for memory deficit when prompted with dementia-related words, showing possible pre-attentive processing and implicit knowledge of their memory problems. More interestingly, patients with anosognosia may overestimate their performance when asked in first-person formed questions but not from a third-person perspective when the questions referring to others.

When assessing the causes of anosognosia within stroke patients, CT scans have been used to assess where the greatest amount of damage is found within the various areas of the brain. Stroke patients with mild and severe levels of anosognosia (determined by response to an anosognosia questionnaire) have been linked to lesions within the temporoparietal and thalamic regions, when compared to those who experience moderate anosognosia, or none at all. In contrast, after a stroke, people with moderate anosognosia have a higher frequency of lesions involving the basal ganglia, compared to those with mild or severe anosognosia.

Autoscopy is the experience in which an individual perceives the surrounding environment from a different perspective, from a position outside of his or her own body. Autoscopy comes from the ancient Greek ("self") and ("watcher").

Autoscopy has been of interest to humankind from time immemorial and is abundant in the folklore, mythology, and spiritual narratives of most ancient and modern societies. Cases of autoscopy are commonly encountered in modern psychiatric practice. According to neurological research, autoscopic experiences are hallucinations.

Anaphia, also known as tactile anesthesia, is a medical symptom in which there is a total or partial absence of the sense of touch.

Anaphia is a common symptom of spinal cord injury and neuropathy.

In regard to anosognosia for neurological patients, no long-term treatments exist. As with unilateral neglect, caloric reflex testing (squirting ice cold water into the left ear) is known to temporarily ameliorate unawareness of impairment. It is not entirely clear how this works, although it is thought that the unconscious shift of attention or focus caused by the intense stimulation of the vestibular system temporarily influences awareness. Most cases of anosognosia appear to simply disappear over time, while other cases can last indefinitely. Normally, long-term cases are treated with cognitive therapy to train patients to adjust for their inoperable limbs (though it is believed that these patients still are not "aware" of their disability). Another commonly used method is the use of feedback – comparing clients' self-predicted performance with their actual performance on a task in an attempt to improve insight.

Neurorehabilitation is difficult because, as anosognosia impairs the patient's desire to seek medical aid, it may also impair their ability to seek rehabilitation. A lack of awareness of the deficit makes cooperative, mindful work with a therapist difficult. In the acute phase, very little can be done to improve their awareness, but during this time, it is important for the therapist to build a therapeutic alliance with patients by entering their phenomenological field and reducing their frustration and confusion. Since severity changes over time, no single method of treatment or rehabilitation has emerged or will likely emerge.

In regard to psychiatric patients, empirical studies verify that, for individuals with severe mental illnesses, lack of awareness of illness is significantly associated with both medication non-compliance and re-hospitalization. Fifteen percent of individuals with severe mental illnesses who refuse to take medication voluntarily under any circumstances may require some form of coercion to remain compliant because of anosognosia. Coercive psychiatric treatment is a delicate and complex legal and ethical issue.

One study of voluntary and involuntary inpatients confirmed that committed patients require coercive treatment because they fail to recognize their need for care. The patients committed to the hospital had significantly lower measures of insight than the voluntary patients.

Anosognosia is also closely related to other cognitive dysfunctions that may impair the capacity of an individual to continuously participate in treatment. Other research has suggested that attitudes toward treatment can improve after involuntary treatment and that previously committed patients tend later to seek voluntary treatment.

Somatoparaphrenia is a type of monothematic delusion where one denies ownership of a limb or an entire side of one's body. Even if provided with undeniable proof that the limb belongs to and is attached to their own body, the patient produces elaborate confabulations about whose limb it really is, or how the limb ended up on their body. In some cases, delusions become so elaborate that a limb may be treated and cared for as if it were a separate being.

Somatoparaphrenia differs from a similar disorder, asomatognosia, which is characterized as loss of recognition of half of the body or a limb, possibly due to paralysis or unilateral neglect. For example, asomatognosic patients may mistake their arm for the doctor's. However, they can be shown their limb and this error is temporarily corrected.

Somatoparaphrenia has been reported to occur predominately in the left arm of one's body, and it is often accompanied by left-sided paralysis and anosognosia (denial or lack of awareness) of the paralysis. The link between somatoparaphrenia and paralysis has been documented in many clinical cases and while the question arises as to whether paralysis is necessary for somatoparaphrenia to occur, anosognosia is not, as documented by cases with somatoparaphrenia and paralysis with no anosognosia.

The use of oral potassium and avoiding high carbohydrate meals can help treat it according to resent tests. Dr. Jacob O. Levitt, a dermatologist who has hypokalemic periodic paralysis, recently conducted research in to it.

Postanesthetic shivering (PAS) is shivering after anesthesia.

The intensity of PAS may be graded using the scale described by Crossley and Mahajan:

Postanesthetic shivering is one of the leading causes of discomfort in patients recovering from general anesthesia. It usually results due to the anesthetic inhibiting the body's thermoregulatory capability, although cutaneous vasodilation (triggered by post-operative pain) may also be a causative factor. First-line treatment consists of warming the patient; more persistent/severe cases may be treated with medications such as tramadol, pethidine, clonidine and nefopam, which work by reducing the shivering threshold temperature and reducing the patient's level of discomfort. As these medications may react and/or synergize with the anesthetic agents employed during the surgery, their use is generally avoided when possible.

One form of treatment that has produced a more integrated body awareness is mirror therapy, in which the individual who denies that the affected limb belongs to their body looks into a mirror at the limb. Patients looking into the mirror state that the limb does belong to them; however body ownership of the limb does not remain after the mirror is taken away.

Tardive Dysmentia is a rarely used term introduced in a 1983 paper to describe "changes in affect, activation level, and interpersonal interaction", and hypothesized to be caused by long-term exposure to neuroleptic drugs in the same way as the much better known syndrome of tardive dyskinesia. Several papers in the following years discussed the validity of the concept, and this small literature was reviewed in a 1993 publication by M. S. Myslobodsky, who drew attention to the "possibility that the syndrome of dysmentia is occasional excessive emotional reactivity, enhanced responsiveness to environmental stimuli, and indifference to or reduced awareness of the patient's abnormal involuntary movements", but concluded that the pathophysiology is uncertain. Since then, the term has fallen into disuse, receiving at most only passing mentions in the literature.

It can reduce the effectiveness of the sodium-channel blocker lidocaine in dental work, so the amide-type local anesthetic. articaine is used on victims instead.

PNE can be caused by pregnancy, scarring due to surgery, accidents and surgical mishaps. Anatomic abnormalities can result in PNE due to the pudendal nerve being fused to different parts of the anatomy, or trapped between the sacrotuberous and sacrospinalis ligaments. Heavy and prolonged bicycling, especially if an inappropriately shaped or incorrectly positioned bicycle seat is used, may eventually thicken the sacrotuberous and/or sacrospinous ligaments and trap the nerve between them, resulting in PNE.

Asomatognosia is a neurological disorder characterized as loss of recognition or awareness of part of the body. The failure to acknowledge, for example, a limb, may be expressed verbally or as a pattern of neglect. The limb may also be attributed to another person, a delusion known as somatoparaphrenia. However, they can be shown their limb and this error is temporarily corrected. Some authors have focused on the prevalence of hemispatial neglect in such patients.