Dr. William Britt, Jr. spoke to us about "How the Brain Malfunctions in Dystonia".

First he said that if he could really answer that question he would win a Nobel Prize! But he went on to give us a great presentation.

He gave us a definition of dystonia and a recap of the types of dystonia. He then showed an example of the challenge in diagnosing dystonia, presenting a very interesting case of DOPA-responsive dystonia.

Next he summarized the known causes for primary (genetic or idiopathic) and secondary (caused by other underlying problems) dystonias, saying that most generalized and focal dystonias are idiopathic=unknown. Therefore medical management (apart from dopa-responsive dystonia) is nonspecific and symptom-directed.

We then looked at neuropharmacology, the medications available which affect neurotransmitters and receptors throughout the whole body, or botulinum toxins which are peripheral and focused.

Dr. Britt spoke of the neurophysiology discussing the differences between normal motor cortex activation (usually there is an immediate burst of activity which is then inhibited) and dystonia where the dampening inhibition does not occur.

Interestingly, recent neuroimaging studies have shown that in the focal dystonia of writer's cramp, images demonstrate increased activity in the frontal motor cortex. Instead of one small part of the cortex being activated during writing, adjacent areas are also being activated. Further studies have revealed a deficiency in the number of axons in the nerve tract running from the basal ganglia to the motor cortex. Since those inputs are inhibitory, that deficiency may be responsible for the failure of "surround inhibition," causing an enlarged area of the motor cortex to be activated during writing.*

We learned that malfunction in the globus pallidi and the putamen are the areas in the basal ganglia that have the highest correlation to dystonia.

Deep brain stimulation surgery and thalamotomy were also discussed.

In a follow up email Dr. Britt said that nerves travel from the thalamus to the prefrontal motor cortex which then primes the motor cortex for activation. Small tracts connect the motor cortex and all the basal ganglia with feedback and feedforward effects resulting in extraordinary fine-tuning of the motor cortex.

The sensory part of the process is derived from two primary sources: signals received from the muscle spindles (the muscle stretch receptors which tell us the extent of muscle contraction) and sensory receptors in the joints (Golgi tendon organs) that tell the brain of the weighting across and position of the joints. (Since our sensory information seems so out of whack in dystonia this was of particular interest to me!)

*The exciting part is that with advanced nueroimaging, we are starting to "see dystonia at work" in the brain.