Functional Neurological Deficit
Encyclopedia
The diagnosis of Functional Neurological Deficit provides an umbrella term for a variety of symptoms of apparent neurological origin but which current models struggle to explain psychologically or organically. Presentation may be similar to a wide range of other neurological conditions from paralysis to weakness. Most neurologists use it as a code for conversion disorder
or hysteria an effort not to offend the patient. Given the controversy over conversion disorder
as a real diagnosis the term is most useful in an aetiological neutral sense.
Functional Neurological Deficit can present with any motor or sensory symptom in the body including:
Given the occurrence of these medically unexplained symptoms in patients with organic brain injury, spinal injury, to post-anaethaesia and post-viral illnesses, the modern term moves away from psychodynamic theory and provides a useful label for what is a complex and little understood disorder.
and thalamus
.
Macrocosmic damage (in the form of lesions for example) in the same subcortical pre-motor circuits may also result in unilateral motor neglect, where voluntary limb use may fail despite a lack of true paralysis and intact primary sensorimotor pathways.
As such hypothesized perpetuating aetiologies and even the precipitating stimuli are relatively unimportant, certainly psychodynamic theories of primary and secondary gain are of questionable relevance. Symptoms may indeed arise in any circumstance that the cortex is not structurally equipped to deal with; from post-anaesthetic weakness, neurological damage , viral infection, fatigue to trivial psycho-social events . These are not however the cause of symptoms but rather the abnormalities within the cortex predispose the brain towards a systemic reaction. (think about how windows randomly crashes) Hence a history of functional symptoms may me be found in individuals. In other species the prefrontal cortex is dedicated to voluntary movement but in man its development encompasses a variety of higher functions including memory and imagination.
As Functional Deficits arise almost certainly from the brain's idea of a limb (stone) then it is useful to hypothesize that dysfunction in the prefrontal cortex has caused the disconnection downstream (Vuilleimier) with the observation of prolonged physiotherapy being that patients "have forgotten how to move properly". Other prolonged observations showing "that patients have real changes of tone" is also thus explained by reciprocal motor neglect.
As the prefontal cortex is also associated with a variety of psychological deficits co-existing disturbances of consciousness and mood may also be present though co-morbidity is not a necessary precursor to functional motor symptoms.
deficiency, lyme disease
, antiphospholipid syndrome
and various other non-structural diseases are all common causes.
The importance of the sub-cortex in movement and its relatively recent evolution could be hypothesised as the structural flaw in the “animal who knows and knows that he knows.” Chardin
Studies of functional symptoms in other higher mammals thus offer the possibility of further insight into what is a distressing and often long-term, though completely reversible condition.
Conversion disorder
Conversion disorder is a condition in which patients present with neurological symptoms such as numbness, blindness, paralysis, or fits without a neurological cause. It is thought that these problems arise in response to difficulties in the patient's life, and conversion is considered a psychiatric...
or hysteria an effort not to offend the patient. Given the controversy over conversion disorder
Conversion disorder
Conversion disorder is a condition in which patients present with neurological symptoms such as numbness, blindness, paralysis, or fits without a neurological cause. It is thought that these problems arise in response to difficulties in the patient's life, and conversion is considered a psychiatric...
as a real diagnosis the term is most useful in an aetiological neutral sense.
Functional Neurological Deficit can present with any motor or sensory symptom in the body including:
- Weakness / Paralysis of a limb or the entire body
- Impaired hearing or vision
- Loss / Disturbance of sensation
- Impairment or loss of speech
- Fixed DystoniaDystoniaDystonia is a neurological movement disorder, in which sustained muscle contractions cause twisting and repetitive movements or abnormal postures. The disorder may be hereditary or caused by other factors such as birth-related or other physical trauma, infection, poisoning or reaction to...
, unlike normal dystonia - Tremor, MyoclonusMyoclonusMyoclonus is brief, involuntary twitching of a muscle or a group of muscles. It describes a medical sign and, generally, is not a diagnosis of a disease. Brief twitches are perfectly normal. The myoclonic twitches are usually caused by sudden muscle contractions; they also can result from brief...
, or other movement disorders - Gait problems
Given the occurrence of these medically unexplained symptoms in patients with organic brain injury, spinal injury, to post-anaethaesia and post-viral illnesses, the modern term moves away from psychodynamic theory and provides a useful label for what is a complex and little understood disorder.
Neuroanatomy
Abnormalities in orbitofrontal, cingulate or prefrontal cortex circuits in processing environmental stimuli from the CNS result in an interruption of “awareness” of contralateral basal ganglia and thalamic motor-circuits. Once the connection is disrupted motor circuits are no longer activated by cortex activity as they rely on reciprocal paths for continual function. In effect it is a hardware crash caused by an interruption of power (consciousness) with a corresponding decrease in blood flow to the basal gangliaBasal ganglia
The basal ganglia are a group of nuclei of varied origin in the brains of vertebrates that act as a cohesive functional unit. They are situated at the base of the forebrain and are strongly connected with the cerebral cortex, thalamus and other brain areas...
and thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
.
Macrocosmic damage (in the form of lesions for example) in the same subcortical pre-motor circuits may also result in unilateral motor neglect, where voluntary limb use may fail despite a lack of true paralysis and intact primary sensorimotor pathways.
As such hypothesized perpetuating aetiologies and even the precipitating stimuli are relatively unimportant, certainly psychodynamic theories of primary and secondary gain are of questionable relevance. Symptoms may indeed arise in any circumstance that the cortex is not structurally equipped to deal with; from post-anaesthetic weakness, neurological damage , viral infection, fatigue to trivial psycho-social events . These are not however the cause of symptoms but rather the abnormalities within the cortex predispose the brain towards a systemic reaction. (think about how windows randomly crashes) Hence a history of functional symptoms may me be found in individuals. In other species the prefrontal cortex is dedicated to voluntary movement but in man its development encompasses a variety of higher functions including memory and imagination.
As Functional Deficits arise almost certainly from the brain's idea of a limb (stone) then it is useful to hypothesize that dysfunction in the prefrontal cortex has caused the disconnection downstream (Vuilleimier) with the observation of prolonged physiotherapy being that patients "have forgotten how to move properly". Other prolonged observations showing "that patients have real changes of tone" is also thus explained by reciprocal motor neglect.
As the prefontal cortex is also associated with a variety of psychological deficits co-existing disturbances of consciousness and mood may also be present though co-morbidity is not a necessary precursor to functional motor symptoms.
Treatment
Treatment options should be aimed towards the re-establishment of power (consciousness) to affected motor circuits through explanation of the condition, proprioception based physiotherapy and drug treatment. Finding and treating the root organic cause that has "sparked" the deafferentation within the CNS is also important i.e. vitamin b12Vitamin B12
Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
deficiency, lyme disease
Lyme disease
Lyme disease, or Lyme borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most...
, antiphospholipid syndrome
Antiphospholipid syndrome
Antiphospholipid syndrome or antiphospholipid antibody syndrome , often also Hughes syndrome, is an autoimmune, hypercoagulable state caused by antibodies against cell-membrane phospholipids that provokes blood clots in both arteries and veins as well as pregnancy-related complications such as...
and various other non-structural diseases are all common causes.
The importance of the sub-cortex in movement and its relatively recent evolution could be hypothesised as the structural flaw in the “animal who knows and knows that he knows.” Chardin
Chardin
The family name Chardin may refer to either:* Jean-Baptiste-Siméon Chardin, French painter* Pierre Teilhard de Chardin, French Jesuit, philosopher and paleontologist* Jean Chardin, French jeweller and traveller, author of The Travels of Sir John Chardin...
Studies of functional symptoms in other higher mammals thus offer the possibility of further insight into what is a distressing and often long-term, though completely reversible condition.