Movement disorders occur when communication is disrupted within the sensorimotor network in the brain. Without a movement disorder, our brains work at our direction to perform the functions we need to move from one place to another. Movement disorders make it difficult for our bodies to move in the ways we want them to.

Essential tremor is the most common form of movement disorder. It affects an estimated 7 million Americans, according to a 2014 study in the journal Tremor or about one in five people over the age of 65.

About 60,000 people each year are diagnosed with Parkinson’s disease. The Parkinson’s Foundation estimates there are 7 to 10 million people worldwide with this movement disorder.

Other common movement disorders include:

• Dystonia                                                                     
• Tics and Tourette syndrome
• Chorea and Huntington’s disease                              
• Restless leg syndrome
• Ataxia, myoclonus and startle           
• Gait disorders 

Some movement disorders are strongly influenced by genetics. Age can also be a factor. Some movement disorders can be related to an injury, environmental toxins, an unrelated medical condition such as a stroke, metabolic disorders, or certain medications.  There are also some instances where we do not yet know the cause of the movement disorder.

At Stanford, Health Care, my colleague Kathleen Poston, MD, has been working on how we can image the networks involved in movement disorders. She has made great progress using PET scans and functional MRI.

In my lab, we are recording electrical signals from the basal ganglia, a group of nuclei deep in the brain that are crucial for the coordination of movement. We are making progress in being able to track the brain signals that support normal versus abnormal movement.  These new techniques will make it much easier for us to design precise therapies, targeted for the individual patient’s symptoms and are based on the underlying pathophysiology.

We have developed computerized technology that helps us measure fine movements, limb movements, gait, and postural control and these will be used at the recently opened Stanford Neuroscience Health Center. Our Kinematic Lab and Balance Center, supported by some very experienced therapists, has new equipment that’s not generally available. Computerized dynamic posturography (CDP), for example, is a way to test balance in various situations. Our CDP system combines virtual reality with moving force plates that assesses in real time sensory, balance, and vestibular functions. It is the only system of its kind in the San Francisco Bay Area. The Kinematic Lab also has a type of gait analysis which is more versatile and informative than traditional systems. Our gait-tracking system analyzes the way people walk in a more natural setting, closer to the walking they do in normal life. That system makes it possible for us to be much more precise in our measurements, for both diagnosis and treatment of movement disorders.

One well established treatment for several movement disorders is deep brain stimulation. It has been used very successfully for more than three decades as a way to reset abnormal brain activity associated with movement disorders. Doctors implant an electrode in the part of the brain where the disruption is occurring. That electrode is connected via a lead under the skin, to a battery-operated neurostimulator implanted in the chest. It acts like a pacemaker by sending electrical signals to the electrodes in the brain.

At Stanford, we have begun to test the next generation of DBS. The first generation DBS system is called open loop: It cannot sense the brain signals it is modulating and is active all the time.  The next generation DBS system can sense brain signals and the research we are doing will lead to an adaptive DBS system, or brain pacemaker, that will only stimulate when needed. It also will automatically adapt its stimulation parameters to a patient’s specific symptoms and state of activity. An adaptive or sensing DBS is already FDA approved for epilepsy. We believe it will be very useful in the future to treat a wider range of neuropsychiatric diseases, including depression, obsessive-compulsive disorder, post-traumatic stress disorder and anxiety.