Functional Dystonia

 

The Functional Neuroimaging Correlates Of Psychogenic Versus Organic Dystonia – March 2013

“The neurobiological basis of psychogenic movement disorders remains poorly understood and the management of these conditions difficult. Functional neuroimaging studies have provided some insight into the pathophysiology of disorders implicating particularly the prefrontal cortex, but there are no studies on psychogenic dystonia, and comparisons with findings in organic counterparts are rare…..”

“Comparing organic dystonia with psychogenic dystonia revealed significantly greater regional blood flow in the primary motor cortex, whereas psychogenic dystonia was associated with significantly greater blood flow in the cerebellum and basal ganglia (all P < 0.05, family-wise whole-brain corrected). Group × task interactions were also examined. During movement, compared with rest, there was abnormal activation in the right dorsolateral prefrontal cortex that was common to both organic and psychogenic dystonia groups (compared with control subjects, P < 0.05, family-wise small-volume correction).”

 

Functional (Psychogenic) Movement Disorders: Merging Mind And Brain – March 11 2012

“Functional dystonia is the second most common presentation in patients with FMD.  There are substantial differences of opinion between experts regarding the diagnosis of functional dystonia. These differences are not helped by the history of dystonia in general: patients now classified as having organic dystonia were, until the 1980s, commonly classified as having hysteria.  Advances in genetics have led to recognition of the phenotypes of primary idiopathic dystonia, which have typical ages of onset, courses, and distributions of dystonia.  For example, DYT1 gene-related primary dystonia starts before age 25 years, often affects the legs at onset, and can spread over a few years after onset to cause generalised dystonia.   By contrast, late-onset primary dystonia affects the cranio-cervical region (spasmodic torticollis is the most common form) and tends to remain focal.  This identification of distinct phenotypes has made easier the recognition of secondary dystonic (including functional) disorders, which have presentations incongruous with primary dystonia phenotypes.  Patients with functional dystonia typically present with fixed abnormal postures accompanied by severe pain similar to that noted in chronic regional pain syndrome type 1 (CRPS1).  Most patients with functional dystonia are young women and the usual trigger is a minor peripheral injury, but the disorder is sometimes spontaneous.  Such patients (who might also be classed as having “causalgia-dystonia” or “tonic dystonia of chronic regional pain”) may experience spread of symptoms to other body parts without further injury.  Limbs are usually involved, but fixed dystonia affecting the neck or jaw has also been reported.”

“Physical examination manoeuvres can be used to show with certainty whether attention is playing a key part in symptom generation in functional tremor; however, to show the same level of certainty in fixed dystonia is difficult.  One might argue that this difficulty occurs because fixed dystonia is not a functional disorder, but to state that maintenance of postures does not need a similar level of attention as maintenance of tremor would also be reasonable.  However, in some patients a brief give way of muscle activity in the affected limb will be felt when the patient is distracted.  In support of the functional label for fixed dystonia, symptoms may resolve with multidisciplinary rehabilitation with an emphasis on cognitive-behavioural therapy, the disorder may co-exist with other more clearly defined psychogenic disorders, and marked (curative) placebo responses have been reported.  However, some, but not all, research electro-hysiological tests suggest similarities between patients with fixed dystonia and those with organic dystonia, although these tests are all subject to confounding from muscle activity, attention, and anxiety.  Maintenance of a fixed posture has been hypothesised to produce secondary changes in central body schema, and these changes might contribute to pain and other unusual features, such as the seeking of limb amputation by some patients.”