The Collaborative Center for X-linked Dystonia Parkinsonism (XDP) at Massachusetts General Hospital provides resources to physicians who are treating patients that exhibit signs of XDP.
What is X-linked Dystonia Parkinsonism?X-Linked Dystonia Parkinsonism (XDP) was first described by Dr. George H. Viterbo. XDP is an adult-onset, genetic movement disorder which predominantly affects males who descend from the Philippine Island of Panay. It is a neurodegenerative disease that evolves over the course of many years, resulting in significant disability and a shortened life span.
Phases of XDP
XDP generally presents in three different clinical phases:
In the majority of patients, XDP begins with involuntary muscle contractions that can occur in any part of the body. These contractions can manifest in many ways, including excessive eye blinking, repeated jaw opening and closing, or twisting/dragging a foot. Over the course of 2-5 years, more muscles become affected, leading to twisting and uncomfortable postures.
When one part of the body is affected, it is called focal dystonia. When many muscle groups are affected, a patient is said to have generalized dystonia.
Dystonia and Parkinsonism
The next phase of XDP usually begins 7-15 years after the onset of focal dystonia. During this phase, the patient has features of both generalized dystonia and parkinsonism. The parkinsonian features include bradykinesia (slowness of movements and reflexes), shuffling gait and rest tremor.
By 15 years after onset, XDP patients primarily show features of parkinsonism. In 6% of patients, XDP manifests primarily as parkinsonism, without evidence of dystonia. Many patients have responded well to deep brain stimulation.
As XDP progresses, patients become more disabled and are eventually unable to work. In the late stages of disease, patients become dependent on others, immobile and unable to care for themselves. Patients with XDP have a reduced life expectancy due to complications of disease.
Patient Referrals to the Mass General Dystonia Clinic
Movement disorders can sometimes be very difficult to diagnose. Many patients come to the neurology department at Massachusetts General Hospital for additional diagnostic evaluations after seeing neurologists outside of the hospital.
Upon visiting the Dystonia Clinic, new patients undergo a comprehensive evaluation that can include a thorough clinical assessment, laboratory testing, cognitive evaluation and brain imaging. These capabilities—along with the experience and expertise of our on-staff neurologists—allow us to make quick and accurate diagnoses.
Once we have established the diagnosis, we are happy to provide ongoing care at our clinic or in collaboration with the patient's primary care physician or neurologist. In addition, we can make referrals to other specialists at Mass General for further testing or treatment when appropriate.
To refer a patient to the Dystonia Clinic at Mass General, please call 617-643-2083, or visit the Dystonia Clinic website.
Research Study Enrollment
The Center supports ongoing research studies in dystonia. Download the attached letter (PDF) if you have a patient with X-linked dystonia parkinsonism (XDP) or another form of dystonia who might be interested in participating.
We do not give results as part of the research study. If a research participant has symptoms for which clinical genetic testing is recommended, the genetic counselor who works on our research study staff can help facilitate that. Please share our IRB-approved study brochure with your patients. Brochure (PDF)
If you have further questions about the study please contact our Study Coordinator, Trisha Multhaupt-Buell, by email at DystoniaResearch@partners.org
The Center for XDP supports training opportunities at Mass General or in the Philippines for clinicians interested in learning about the care and treatment of XDP and other forms of dystonia. For more information, please contact Amy Alessi, PhD at firstname.lastname@example.org.
Investigating Deep Brain Stimulation
Deep brain stimulation (DBS) is a surgical treatment in which an implanted device delivers electrical stimulation to the brain in order to alleviate neurologic symptoms.
Stimulation is applied through a surgically implanted wire (also called a lead or electrode) that is inserted into the brain. DBS is most commonly used to treat the symptoms of Parkinson’s disease, essential tremor and dystonia. In dystonia, the most common stimulation target is the globus pallidus internus (GPi). The electrical stimulation is generated by an implantable pulse generator (IPG) that is placed under the skin in the chest, similar to a cardiac pacemaker. The stimulation can be adjusted non-invasively by a neurologist in order to optimize symptom relief.
DBS is most effective for primary dystonias—that is, inherited dystonias like XDP and dystonias without a known cause—and less effective for secondary or acquired dystonias, such as those due to brain injury from cerebral palsy or stroke. With DBS, primary dystonia symptoms improve by 50-60% on average, although individuals may benefit substantially more or less than average. These benefits appear to last at least 10 years.
There is less known about the long-term benefit of DBS in XDP specifically, although ours' and others' experience has been that DBS can be a very effective treatment for the symptoms of XDP. In one study of eight individuals with XDP, all eight patients experienced an improvement in dystonia symptoms, with six of eight patients improving by more than 65% at three months (Neurology April 8, 2014 vol. 82 no. 10 Supplement P1.013).
With the DBS surgery, there is a 1-2% risk of brain bleeding or stroke that results in new symptoms such as weakness, numbness or problems with speech; in the majority of cases, these side effects fade with time. There is also a 3-4% risk of surgical infection, which may require removal of all or part of the stimulator.
Lastly, as the IPG battery depletes, it must be replaced in a minor surgery. The interval between replacement varies widely between individuals depending on the device and stimulation settings, but is typically 2-5 years for non-rechargeable batteries and up to 9 years for rechargeable batteries.
Deep Brain Stimulation at Mass General
The neurosurgeons at the Functional Neurosurgery Center at Mass General use deep brain stimulation (DBS) to treat patients with a wide variety of movement disorders. The Neurosurgery Center uses the most advanced stereotactic technology—microelectrode recordings—for optimal lead positioning and the best patient outcome.
Mass General was one of the first hospitals to perform DBS, and today the Neurosurgery Center uses it to treat Parkinson’s disease as well as many different types of dystonia, including:
- Genetic dystonia, such as XDP
- Generalized dystonia
- Segmental dystonia
- Focal dystonia, such as spasmodic torticollis