EMG
Electromyography is a technique for evaluating and recording the electrical activity produced by skeletal muscles.
Department of Clinical Neurophysiology (EMG & EP)
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This department was established in 1975 by Dr. S.S.Pandya who was trained in U.K. by Prof Buchthal,a pioneer in this field. Dr. Shubha Pandya was the first one to introduce this branch of diagnostic medicine in Mumbai and possibly in the country.
The Electrodiagnostic department at Bombay Hospital is equipped with top of the line equipment. The entire study is performed by doctors trained specially in this branch of medicine.
Electromyograph: The Machine
Electromyography & Nerve Conduction Study (EMG & NCS) also known as Electrodiagnosis, is an assessment of a patient by a physician using a series of tests to establish an accurate diagnosis of a presenting clinical problem that suggests a neuromuscular disorder.
It is an extension of the clinical examination to assess the functional status of the peripheral neuromuscular system and is useful in the diagnosis of Peripheral Neuropathies, Cranial neuropathies, Radiculopathies, Neuromuscular junction effects, Myopathies, Nerve Injuries, Plexopathies and Anterior Horn cell diseases.
It is the only test that examines the function of the nervous tissue being examined and is directed by the clinical impression and the working diagnosis (customized for every patient.
- Accurate localization of the site (Nerve, Plexus, Root, muscle, AHC)
- Determining the extent( localised, widespread, Multifocal)
- Identifying the predominant Pathophysiology( Demyelinating, axonal or both)
- Objective quantification of the severity (Mild, Moderate, severe)
- Documents progress of lesion
- Intra operative assessment( for trauma)
Nerve conduction studies- A method of measuring changes in a peripheral nerve by stimulating it electrically and recording the action potential generated.
- Sensory nerve conduction studies
- Motor nerve conduction studies
Electromyography-
A method of studying the electrical activity of a muscle, by placing a needle electrode within it and observing:
- The spontaneous activity in the muscle at rest.
- The action potentials (Motor Unit Action Potentials) generated by voluntary contraction of the muscle. This is an audio visual diagnosis and is done online.
What should your patient expect?
NCS FAQs answered
- Nerve Conduction Studies are performed using surface electrodes
- The ‘shocks’ given are in Milli amperes and are quite bearable.
- The stimulus is local and does not travel all over the body
- Nerve Conduction Studies are always required with a Needle Electrode Examinations.
- Can be done very safely even in the new –born & pregnant women.
- The Motor conduction stimulus feels like a tap and causes movement of the area being stimulated
- The Nerve Conduction Studies may be contraindicated in patients with Pacemakers.?
What should your patient expect?
EMG FAQs answered
- The Needle EMG examination is done using fine Disposable Electrodes, which are solid pins but thin and very sharp
- No shocks are givenThe Needle is inserted just into the muscle for few seconds
- The Needle is inserted just into the muscle for few seconds
- The patient is asked to contract the muscle and the activity is picked up by the electrode and displayed on the monitor and over a loud speaker –diagnosis is made on-line
- The number of muscles examined depend upon the working diagnosis
- Needle EMG should be avoided in patients with bleeding disorders, Patients on Anticoagulants and when there is local infection
How can the referring Doctor help?
- The working diagnosis or Differential diagnosis should be stated in the referral note
- It helps to customize the procedure.
- Relevant reports and supportive radiography should be sent with the patient
- If the patient is HbsAg or HIV positive/ has a pacemaker or is on Anticoagulants the Electromyographer must be alerted
The other tests done in our department are Evoked Potentials which include:
- Visual evoked potentials (VEP)
- Brainstem auditory evoked potentials (BAEP)
- Somatosensory evoked potentials (SSEP)
Visual Evoked Potentials (VEP): Test the optic pathway
- This method currently provides the most sensitive means of detecting subclinical lesions of the optic nerve and may enable a diagnosis of M.S. to be made at an earlier time.
- Abnormality in the Visual Evoked Potentials is also encountered with compressive lesions of the anterior visual pathways.
- In the pediatric age group, the flash VEP may be used as a screening test for the visual pathway.
Brainstem Auditory Evoked Potentials (BAEP): Test the Auditory pathway
- The neurologic applications of Brainstem Auditory Evoked Potentials have been proven useful in the diagnosis of Multiple Sclerosis.
- It may be used as a screening test for early detection of acoustic neuromas and in the assessment of comatose patients.
- Like the Visual Evoked Potentials, it may also be a useful screening test for hearing in the pediatric age group such as neonatal screening and those who do not cooperate sufficiently with behavioral testing.
Somatosensory Evoked Potentials (SSEP): Test spinal cord function
- The Sensory Evoked Potentials findings may help in the detection and localization of lesions of the central somatosensory pathways but are not pathognomonic of specific diseases.
- In Multiple Sclerosis (MS) the presence of Sensory Evoked Potentials abnormalities may reveal subclinical lesions involving the central somatosensory pathways thus aiding in early diagnosis.
- In patients with definite Multiple Sclerosis, the incidence of Sensory Evoked Potentials abnormality is about 80% whereas in the category of possible Multiple Sclerosis, the yield is only about 30%.
- The interpretation of electrophysiological results must therefore always be taken in a clinical context.
AVAILABLE DIAGNOSTIC FACILITIES
- Nerve conduction studies and Electromyography for assessing nerve, muscle, root and plexus disorders in adults
- Neuromuscular diseases in Paediatrics
- Assessment of Birth brachial plexus injuries
- Specialized tests for Neuromuscular Junction Disorders
- Provocative tests for Channelopathies
- Tests for evaluating & prognosticating traumatic nerve / plexus involvement in adults
- Assistance in EMG guided Botulinum toxin injections
- Studies to assess erectile dysfunction & pelvic floor study
- Visual evoked potentials (VEP)
- Somatosensory evoked potentials (SSEP)
- Brainstem auditory evoked potentials for determining hearing in children (BAEP)
