Definition<unk>  is now contained under the umbrella term functional neurological symptom disorder. In cases of<unk> , there is a psychological stressor. The diagnostic criteria for functional neurological symptom disorder, as set out in DSM-5, are: Specify type of symptom or deficit as: * With weakness or paralysis * With abnormal movement (e.g. tremor, dystonic movement, myoclonus, gait disorder) * With swallowing symptoms * With speech symptoms (e.g. dysphonia, slurred speech) * With attacks or seizures * With amnesia or memory loss * With special sensory loss symptoms (e.g. visual blindness, olfactory loss, or hearing disturbance) * With mixed symptoms. Specify if: * Acute episode: symptoms present for less than six months * Persistent: symptoms present for six months or more. Specify if: * Psychological stressor<unk>  * No psychological stressor (functional neurological symptom disorder) Exclusion of neurological disease<unk>  presents with symptoms that typically resemble a neurological disorder such as stroke, multiple sclerosis, epilepsy, hypokalemic periodic paralysis or narcolepsy. The neurologist must carefully exclude neurological disease, through examination and appropriate investigations. However, it is not uncommon for patients with neurological disease to also have<unk> . In excluding neurological disease, the neurologist has traditionally relied partly on the presence of positive signs of<unk> , i.e. certain aspects of the presentation that were thought to be rare in neurological disease but common in<unk> . The validity of many of these signs has been questioned, however, by a study showing they also occur in neurological disease. One such symptom, for example, is la belle indifférence, described in DSM-IV as "a relative lack of concern about the nature or implications of the symptoms". In a later study, no evidence was found that patients with functional symptoms are any more likely to exhibit this than patients with a confirmed organic disease. In DSM-V, la belle indifférence was removed as a diagnostic criterion. Another feature thought to be important was that symptoms tended to be more severe on the non-dominant (usually left) side of the body. There have been a number of theories about this, such as the relative involvement of cerebral hemispheres in emotional processing, or more simply, that it was "easier" to live with a functional deficit on the non-dominant side. However, a literature review of 121 studies established that this was not true, with publication bias the most likely explanation for this commonly held view. Although agitation is often assumed to be a positive sign of<unk> , release of epinephrine is a well-demonstrated cause of paralysis from hypokalemic periodic paralysis. Misdiagnosis does sometimes occur. In a highly influential study from the 1960s, Eliot Slater demonstrated that misdiagnoses had occurred in one third of his 112 patients with<unk> . Later authors have argued that the paper was flawed, however, and a meta-analysis has shown that misdiagnosis rates since that paper was published are around four percent, the same as for other neurological diseases. Exclusion of feigning<unk>  is unique in ICD-10 in explicitly requiring the exclusion of deliberate feigning. Unfortunately, this is likely to be demonstrable only where the patient confesses, or is "caught out" in a broader deception, such as a false identity. One neuroimaging study suggested that feigning may be distinguished from<unk>  by the pattern of frontal lobe activation; however, this was a piece of research, rather than a clinical technique. True rates of feigning in medicine remain unknown. However, it is believed that feigning of<unk>  is no more likely than of other medical conditions. Psychological mechanism The psychological mechanism of<unk>  can be the most difficult aspect of a<unk>  diagnosis. Even if there is a clear antecedent trauma or other possible psychological trigger, it is still not clear exactly how this gives rise to the symptoms observed. Patients with medically unexplained neurological symptoms may not have any psychological stressor, hence the use of the term "functional neurological symptom disorder" in DSM-5 as opposed to<unk> ", and DSM-5's removal of the need for a psychological trigger.
Conversion disorder
Somatization disorder
Otodental syndrome
Malingering
Bruxism
Anterior cerebral artery syndrome
Perisylvian syndrome
Diencephalic syndrome