Why does dystonia fascinate and challenge neurology?

Dystonia is probably the most nebulous of neurological terms. Neurologists use the term for a vast array of neurological diseases. Dystonia also crops up as part of many complex neurological syndromes. Worse still, neurologists also use the name dystonia as a symptom. All quite confusing and perplexing for the lay observer.

No wonder dystonia defies simple definitions. Take the National Institute of Neurological Disorders and Stroke (NINDS) definition which labels dystonia as “a disorder characterized by involuntary muscle contractions that cause slow repetitive movements or abnormal postures“. Then compare it with the NHS Choices definition which sees dystonia as “a medical term for a range of movement disorders that cause muscle spasms and contractions“. We must accept the flexibility of dystonia as both a disorder, and a range of disorders. The defining feature of dystonia however is simple enough-abnormal muscle postures and contractions.

The complexity in the definition is just a tip of the iceberg of the things that neurologists find fascinating about dystonia. Here are 5 big reasons why dystonia excites and challenges neurologists.

1. Dystonia is a very visible disorder

Rogers Hartmann at TEDxSMU from tedxsmu on Vimeo.

The abnormal postures that typify dystonia are observable, and the neurologist can describe and define the disorder (or disorders!). This is not the case with many neurological disorders such as migraine, which rely entirely on a history, or epilepsy, which rely heavily on eyewitness accounts. The abnormal postures in dystonia are often very dramatic, and sometimes literally defy description. To help ‘decode’ complex dystonia, neurologists often make video recordings of their patients and send to dystonia experts. And dystonia experts present their own video recordings at neurology conferences, to teach the less initiated of course, but also to flaunt their well-earned expertise.

2. Dystonia is both hereditary and acquired

Many types of dystonia are hereditary. Myoclonus-dystonia and dopa-responsive dystonia (DRD) for example are caused by well-defined genetic mutations. Dystonia is however also frequently acquired, for example as an adverse effect of antidepressant, antipsychotic, and anti-epileptic drugs. Neurologists go to great lengths to sort out what type of dystonia their patients have, bristling with anticipation that the next genetic blood test they send off will clinch the diagnosis. It doesn’t seem to matter that this is often hope trumping experience.

3. Dystonia manifests in a multitude of ways

Dystonia may be localised such as with blepharospasm (excessive eyelid twitching), hemifacial spasm, Meige’s syndrome, and cervical dystonia (torticollis). At the same time, dystonia may be generalised as in Wilson’s disease, neuroferritinopathy, and neuroacanthocytosis. Dystonic symptoms often manifest spontaneously, but they may only be task-specific such as in writers cramp and musician’s dystonia. A further way dystonia crops up is as an ally of other movement disorders, as we see with dystonic tremor.

4. Dystonia is a rapidly evolving field

Unlike some neurological specialities that are stuck with age-old diseases, dystonia experts regularly describe new dystonia syndromes and genetic mutations, filling up an already crowded taxonomy. An example is the ever-expanding genetic mutations that cause primary dystonia, starting from DYT 1 to DYT 21, and still counting. The field of non-genetic dystonia is also expanding with new disorders such as Watchmaker’s dystonia. Well-established dystonia syndromes also surprise neurologists by manifesting in completely unexpected ways. Recent examples of these new phenotypes are foot drop dystonia resulting from parkin (PARK2) mutation. Neurologists also get excited when they come across known, but rare, presentations of dystonic syndromes such as this recent report on feeding dystonia in chorea-acanthocytosis. 

5. Treatments of dystonia are proliferating

Just as the types of dystonia are burgeoning, so are the treatments. Some interventions are novel, and some have a feel of ‘back to the future’. A few recent examples are treatment of isolated dystonia with zolpidem and selective peripheral denervation for cervical dystonia. Enough to keep the dystonia researchers busy, and to keep their patients feeling valued. Old school treatment such as botulinum toxin however maintain their pride of place. 

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For more on dystonia syndromes and treatment, check out:

• Isolated and combined dystonia syndromes-an update on new genes and their phenotypes
• Therapeutic advances in dystonia (oh dear, its not open access).
• EFNS guidelines on diagnosis and treatment of primary dystonias 

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Dystonia is a hydra; why not get a concise handle by exploring the dystonia topics in neurochecklists