Functional Neurological Symptom Disorder (FNsD) is a neurological disorder for which very little is currently known. It is an umbrella term for a variety of symptoms which look similar to those caused by neurological conditions such as
Multiple Sclerosis (MS) or
Parkinson's Disease, including weakness, fatigue and seizures. It is currently believed that Functional Neurological Symptom Disorder arises from a problem with the patient's
Central Nervous System, which is not sending and receiving signals correctly.
[1] The brain of a patient with Functional Neurological Symptom Disorder is structurally normal, but functions incorrectly.
[2]
Currently, traditional tests and investigations such as blood tests, MRI and CT scans will show no abnormalities in patients with FNsD; however, it has been discovered that there is a difference in blood flow to certain key areas of the brain when scanned using
Functional Magnetic Resonance Imaging (fMRI). Although currently there is no way to 'see' whether a patient has FNsD, their symptoms are real, and often cause disability and distress to the individual.
[3] It is widely accepted that those with FNsD are equally disabled as those with Multiple Sclerosis or Parkinsons, and often are more distressed.
The first mention of Functional Neurological Symptom Disorder in literature dates from Ancient Egypt, and little progress has been made in understanding the condition since. FNsD has also previously been referred to as
Hysteria and
Conversion Disorder (CD). The term Conversion Disorder is still used by some clinicians, however refers specifically to those who have a psychological stressor causing their symptoms, such as a traumatic event or mental illness. It is "a psychoanalytic concept that describes the occurrence of motor or sensory neurological symptoms other than pain and fatigue that cause distress, are not explained by disease, not malingered but are thought to relate to psychological factors"
[4]