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| June 5, 2006 |
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| The physicians and staff of The Neuroscience Group are providing this physician and provider communication to help you stay abreast of issues and updates in the dynamic field of neurosciences, with the goal of helping you provide better overall healthcare services to your patients. |
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Service Update for Primary Care Colleagues |
| The neurologists are providing EMG services at New London Clinic and Shawano Clinic in conjunction with expanded physician coverage. Dr. Lisa Kokontis will be scheduling patients at New London on Thursday mornings, beginning mid-June. Dr. Susan Hibbs will be joining Dr. Gizell Larson in providing appointments and EMGs at the Shawano clinic on Fridays. Same day appointments are available at our Neenah office for neurology patients requiring urgent care. It is not necessary for the physician to make a call prior to scheduling a patient requiring an urgent visit, although the neurologists do appreciate any clinical insights that you feel might make the neuro consult more beneficial for your patient. |
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Effectively Using EMG and NCS in Detecting Disorders of the Peripheral Nervous System |
| Electromyography (EMG) and Nerve Conduction Studies (NCS) are almost always done in tandem. Together they help to provide complementary information. During an EMG needle electrodes are inserted into muscles to observe and record motor unit potentials MUPs). Muscles are tested at various stages of rest and contraction. In active neuropathic processes, fibrillation potentials occur and can be recorded. In neuropathic conditions MUPs have increased amplitude, duration and degree of polyphasia. Fibrillations are also seen in myopathic processes as well but the MUP’s may have decreased amplitude, duration and increased polyphasia and rapid recruitment. EMG/NCS are useful in diagnosing motor neuron disease (ALS), radiculopathy, plexopathy and entrapment neuropathy, peripheral polyneuropathy, disease of the neuromuscular junction (myasthenia gravis and Lambert Eaton), myopathy and myositis. |
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During NCS, surface electrodes are used to record the electric responses, sensory nerve action potentials (SNAPs) and motor action potentials (MAPs). The latency, amplitude, duration and conduction velocity of these responses is used to characterize nerve function. |
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| When ordering an EMG/NCS the physician/nurse practitioner/physician’s assistant is seeking assistance in either verifying the presence of a specific disease process or eliminating this from the differential. The usefulness of the EMG/NCS is best understood as an extension of the neurological history and neurophysical exam. As a diagnostic test, it is most effective when performed by the examining neurologist who specifically tailors the exam to study the parts of the nervous peripheral nervous system potentially responsible for the patient’s symptoms. |
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For example, let’s look at how NCS (along with a comprehensive clinical evaluation) can help to narrow the differential diagnosis for peripheral neuropathy. The test helps to determine if the lesion is primarily the result of damage to the myelin sheath or to the axon, whether the lesion is focal or diffuse, helps to determine whether the process is distal or proximal and helps with determining severity and temporal profile of the process. Peripheral neuropathy can be categorized as:
- Uniform demylinating mixed sensorimotor neuropathy (hereditary forms of neuropathy, metachromatic leukodystrophy, Tangier’s disease, Krabbe’s disease)
- Segmental demylinating motor sensory polyneuropathy (Guillain-Barre syndrome), neuropathy associated with gammopathy, hypothyroidism, carcinoma or lymphoma, AIDs, Lyme disease and responses to neurotoxins
- Axonal motor sensory polyneuropathy such as hereditary forms of neuropathy, lymphomatous neuropathy
- Axonal sensory neuropathy, such as hereditary forms of neuropathy, primary amyloidosis, Sjogren’s syndrome, paraneoplastic neuropathy or neuropathy cased by drugs or vitamin B12 deficiency
- Mixed axonal demylinating sensorimotor polyneuropathy from uremia or diabetes mellitus
- Axonal sensorimotor polyneuropathy caused by nutritional deficiencies, alcohol, sarcoidosis, connective tissue disease, toxins, heavy metals and drugs
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| EMG/NCSs can be scheduled through our patient service representatives at 725-9373. |
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