Movement Disorder Laboratory diagnoses and treats complex dystonias
Movement disorders such as tremor, dystonia and Parkinson's disease are among the most common neurological conditions. For patients, movement disorders can result in considerable disability. Hand and arm tremor can impair eating, handwriting and grooming. Vocal tremor can hinder communication, resulting in social withdrawal. For the physician, precise diagnosis can be difficult because of the broad array of related movement disorders.
Mayo Clinic's Parkinson's Disease and Movement Disorders Laboratory in Rochester, Minn., is one of the few centers in the United States that offers a wide range of analytic techniques capable of aiding in the classification of these conditions. Among the techniques used are:
- Tremor frequency analysis
- Quantitative brain wave analysis
- Dystonia mapping studies
- Movement pattern analysis
The core assessment tool comprises simultaneous electroencephalogram (EEG), electromyogram (EMG) and video recordings taken while the patient exhibits abnormal movements.
Although most EMG laboratories focus on disorders of the peripheral nervous system, Mayo Clinic's laboratory also uses these techniques to diagnose problems of the central nervous system. A typical diagnostic test in the Parkinson's Disease and Movement Disorders Laboratory lasts 20 to 45 minutes. Surface EMG is used to monitor muscle activity. For some conditions, such as myoclonus, EEG helps determine the locus of abnormal movement in the central nervous system. Computer analysis of the recordings has advantages for diagnostic specificity, often allowing identification of the precise type of tremor a patient has.
Stiff person syndrome
The experience and expertise of Mayo's movement specialists extend to rare movement disorders, such as orthostatic tremor and stiff man syndrome (SMS), also known as stiff person syndrome. Two-thirds of patients who received a diagnosis of this rare disorder at Mayo during the period from 1984 through December 2008 were women.
SMS, identified by Mayo Clinic in 1956, is characterized by chronic rigidity and spasms in the muscles of the limbs and trunk. Patients frequently have painful spasms and falls, as well as fixed spinal deformities from long-term rigidity. Some patients have respiratory impairment from chest wall spasms.
SMS is distinguishable by hyperexcitability of spinal motor neurons. The Parkinson's Disease and Movement Disorders Laboratory uses multichannel surface EMG, concentric needle studies of the lumbar paraspinal muscles, and electrical and acoustic stimulation of the nerves to evaluate startle reflexes in suspected cases of SMS. This condition is often mistaken for a psychogenic disorder, but electrophysiological findings consistent with brainstem and spinal hyperexcitability can help confirm the clinical suspicion in many cases.
Diagnostic testing in the Movement Disorder Laboratory can also guide treatment. For example, multichannel EMG needle mapping studies can pinpoint areas of activity that cause spasmodic torticollis. Precise localization can then help physicians choose sites for injecting botulinum toxin and identify patients who might benefit from surgical treatment.
Collaborative care for complex conditions
Mayo also has a large practice in treating spasmodic dysphonia and jaw and orofacial dystonias with botulinum toxin. Movement disorder neurologists, ear, nose and throat surgeons, and speech pathologists share a close collaboration in caring for patients who receive these complex injections.
Movement disorders, particularly in rare conditions, can be very difficult to diagnose and treat. The expertise at Mayo Clinic lies in clarifying a difficult diagnosis, as well as providing botulinum toxin treatment in common and rare conditions.
Points to remember
- Although most electromyogram (EMG) laboratories focus on disorders of the peripheral nervous system, Mayo Clinic's laboratory also uses multiple techniques to diagnose and classify movement disorder problems of the central nervous system precisely.
- Among the techniques used are tremor frequency analysis, quantitative brain wave analysis, dystonia mapping studies and movement pattern analysis. The core assessment tool comprises simultaneous electroencephalogram (EEG), EMG and video recordings taken while the patient exhibits abnormal movements.