A functional movement disorder causes abnormal movement or involuntary positioning of parts of the body. This is caused due to malfunction in the nervous system. This condition can also develop due to undiagnosed neurological disease.
What is Functional Movement Disorder?
Functional movement disorder is a form of neurological disorder that inhibits normal limb and movement functions.
There are different symptoms of a functional movement disorder, such as functional jerks, functional tremors, functional gait disorders, etc.
Some patients may show only one type of symptom while others may experience multiple symptoms at a time. Patients suffering from functional neurological disorders often experience several distressing and disabling signs, such as:
Tremor – An arm or leg shakes uncontrollably. In functional tremors, the severity of the shaking can vary greatly. The symptom may even dissipate if you are distracted. However, the severity of symptoms can also be so high as to render the patient helpless and disabled.
Twitches/Jerks – Some patients may experience jerky movements. They may usually be caused due to loud noises, certain kinds of lights and even bursts of pain.
Contractures/Spasms/Dystonia – Some patients may find that their feet and hands develop abnormal positions, which are often hard to rectify. They may either be a temporary spasm or can be a chronic condition. Chronic spasms are usually called functional contracture or functional dystonia. Patients suffering from functional dystonia often have a twisted foot or a ‘clenched hand’.
Gait issues – Functional movement disorders can also cause a variety of gait (walking) problems. The most commonly seen problem is the ‘dragging’ walk which is often seen in patients with a weakened function in one leg. Other forms of gait problems can be unsteady gait, which is usually caused by a history of falling down and a heightened fear of falling in the future.
As opposed to other types of movement disorders such as Parkinson’s disease a functional movement disorder does not develop due to disease or damage to the nervous system.
It is rather a reversible problem that affects the way the nervous system normally works. This means that a functional movement disorder can be treated successfully or even go away completely.
How is Functional Movement Disorder diagnosed?
Functional movement disorder is usually diagnosed by a neurologist. It can be quite difficult to diagnose the disorder as it requires extensive knowledge of the complete range of movement disorders caused by neurological problems. Many of these disorders are unusual and even bizarre in some cases.
Hence, it can be difficult to conclude all of the clinical features of functional movement disorder. These often develop as a result of an injury and can come on suddenly.
What are the Symptoms of Functional Movement Disorder?
These are the different types of symptoms and how they affect the patient’s movement:
Functional tremor is usually identified when:
- The tremor disappears shortly or changes in rhythm when following movements with a healthy arm or leg. This is often called the ‘entertainment test’.
- It becomes difficult to make rhythmic movements with your healthy hand or leg.
- There are times when the shaking is not present.
- The tremors change severity.
- Tremors worsen if someone tries to hold the affected arm or leg in place.
Involuntary jerking of limbs is also called ‘myoclonus’, which is identified by:
- Jerks in response or anticipation to loud sounds.
- The presence of a special brainwave called ‘Bereitschaftpotential’ is not found in patients suffering from any neurological disease.
Benign twitches are also called ‘benign fasciculations’ and are often experienced in multiple areas of the body at a time. This can cause anxiety about the cause of the symptoms, which worsens the symptoms.
Functional spasms (dystonia) usually affect the wrist and hand. This condition may cause the hand to clench in an abnormal position, called a ‘carpopedal spasm’.
This symptom can also be caused due to other medical disorders, such as low blood calcium. This condition is most likely to develop during hyperventilation. Hence, doctors consider this cause before deciding if the condition is ‘functional’ or not.
Fixed posture/Functional dystonia
A fixed posture defines a hand or feet which remains fixed in a single position for all, or most of the time. This condition is often related to functional weaknesses of the limbs and usually causes pain.
Functional gait disorder
Functional gait disorders can occur in different forms. This condition causes difficulty in walking without an underlying neurological disease as its cause.
The patient may experience excessive slowness while walking or a cautious gait with feet wide apart and stiff legs.
This condition may also cause the person to walk in a crouching position and experience sudden buckling of the knees, which is usually associated with a functional weakness in the legs.
The patient may also experience a generally unsteady gait with sudden sidesteps.
Functional movement disorders can be caused due to various reasons in different patients. At times, the condition can arise following an injury or chronic pain. It is highly recommended to consult an expert neurologist when you notice abnormal shaking or tremors in your limbs.