Functional movement disorder (FMD) is also known as functional neurological disorder, conversion disorders.1 FMD is applied to conditions where there are physical symptoms such as tremors, abnormal movements, gait problems, etc. But there is no apparent organic disease found that can be the cause of the symptoms. Since, there is no organic disease found the symptoms are though to be due to a psychological condition. Basically, there is a problem in the function of the body but there is no structural problem in the body and the symptoms cannot be related to any neurological or medical condition. The diagnosis of Functional movement disorder is arrived after excluding malingering (fabricating symptoms with an underlying motive), even though there is no organic disease FMD patients are not fabricating symptoms.
What Causes Functional Movement Disorder?
The exact cause of Functional movement disorder is not known.1 Many research studies have already started to find the risk factors and causes. It is believed that a previous injury or a similar symptom in the affected body part might trigger FMD. Usually when you get a symptom it resolves spontaneously or with medication, here the symptoms get stuck in a pattern in the nervous system and then it is mirrored in the altered brain functioning. When that happens, it goes beyond the patient’s control. Sometimes the symptoms might not actually be present but the patient feel as if it is there; she or he is not lying about it because they actually feel that way.
Some of the risk factors or triggering factors that research studies have found out that has been present proceeding the Functional movement disorder are:
- Chronic pain
- Traumatic events
- Physical injury
- Panic attack
Earlier days Functional movement disorder was thought to be purely psychological, the effects of a recent or earlier stressful event might manifest as a physical symptom. This is how the term conversion disorder name came. But this cannot be applied to all patients who were diagnosed with FMD; therefore this cannot fully explain the cause of FMD. A patient does not necessarily have to be anxious, depressed or gone through a traumatic childhood event to develop functional movement disorder.
A study done by using a single photon emission computerized tomography (SPECT) to view the brain has shown reduced blood flow in the thalamus and in the basal ganglia in affected patients for a short period of time.
Another study done by using Electroencephalography (EEG) and MRI to visualize the brain and record the brain activity have shown some abnormal changes like increased brain activity in some areas that is not seen in a healthy individual. Another study done using Voxel-based morphometry shown increased cortical thickness and grey matter volume in functional movement disorder patients.
FMD occurs both in children and adults. The exact prevalence of FMD is in children is not available because it’s difficult to diagnose FMD in children, however the prevalence is about 1-4 per 100,000. Weakness, abnormal movements and pseudo seizures are the common symptoms seen in children. All age group children are affected by FMD however it is uncommon in children less than 10 years. The exact prevalence of Functional movement disorder in adults is unknown; the estimated prevalence is 14-22 per 100,000. It is actually the second commonest neurological reason for an adult to visit the outpatient department, whereas the first being headaches/migraine. It is believed to be as common as multiple sclerosis or Parkinson’s disease. FMD is more common in females than in males in both children and in adults.
Functional movement disorder (FMD) is a condition where there are physical symptoms such as tremors, abnormal movements, gait problem, etc. But there is no apparent organic disease (structural abnormality) found that can be the cause for the symptoms. The exact cause of FMD is not known. Many research studies have already started to find the risk factors and causes. It is believed that a previous injury, chronic pain, stress, infection, traumatic event, panic attacks and physical injury might trigger functional movement disorder. Imaging studies done on FMD patients have shown some changes in the brain therefore, there might be a structural change causing FMD.