knowledge a person has, the more implausible are the presenting symptoms. However, no systematic studies have yet been performed to substantiate this statement. Diagnosis Definition Conversion disorder is now contained under the umbrella term functional neurological symptom disorder. In cases of conversion disorder, 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 (conversion disorder) No psychological stressor (functional neurological symptom disorder) Exclusion of neurological disease Conversion disorder 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 conversion disorder. In excluding neurological disease, the neurologist has traditionally relied partly on the presence of positive signs of conversion disorder, i.e. certain aspects of the presentation that were thought to be rare in neurological disease but common in conversion. 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