Dystonia is a circuit disorder of the brain involving the basal ganglia, cerebellum, and the cortex. Medical & Scientific Advisory Council Member Kristina Simonyan, MD, PhD led two recently published studies describing important advancements in our understanding of how these networks are compromised in adult onset focal dystonia. These studies suggest a common underlying mechanism to dystonia as well as unique mechanisms specific to particular subtypes. DMRF Clinical Fellow Pichet Termsarasab, MD contributed to this work.
In a study using MRI to examine volunteers with spasmodic dysphonia, writer’s cramp/hand dystonia, cervical dystonia, and blepharospasm, investigators found patterns of brain activity that were very different from healthy controls. They discovered re-organized brain circuits across all dystonias, and unique changes in task-specific dystonias. The investigators took a closer look at spasmodic dysphonia (SD) to further explore functional brain circuits. Differences in how the brain processes sensory information have long been associated with dystonia, but it is unknown how these differences correspond to the various subtypes of dystonia.
Dr. Simonyan and team looked at subtypes of SD: adductor and abductor as well as sporadic cases and cases with a family history of SD. Volunteers were asked to respond to visual and tactile stimuli (for example, flashing lights and blindfolded touch to the hands). MRI was used to monitor brain activity during these sensory exercises. The investigators found similarities and differences among the SD subtypes in terms of how affected subjects processed sensory information compared to controls. Certain abnormalities in how volunteers responded to stimuli across time were found in all SD subtypes, and especially in patients with a family history of SD. Patients with familial SD had greater involvement of the cerebellum during these exercises, while patients with sporadic SD displayed greater involvement of other brain areas. There were differences among volunteers with adductor and abductor SD.
AT A GLANCE
- Brain pathways are circuits of neurons (brain cells) that conduct signals from one part of the nervous system to another.
- Dystonia patients process sensory information using different brain pathways than healthy controls.
- The coordination of signals between certain areas of the brain is compromised in adult onset focal dystonia.
- Identifying these disorganized brain pathways may provide opportunities to develop treatment strategies to correct them.