Clinical Neurophysiologic Services (Electro diagnosis) 

» Electromyography (NCV/EMG)
» Evoked potentials (EP)
» Electroencephalography (EEG)
» Sleep studies (polysomnography) 

Electro diagnostic studies can be helpful in evaluating weakness, numbness, pain and symptoms such as fatigue, cramps and abnormal sensation. Electro diagnostic evaluation is an extension of the neurologist's physical examination and is performed by our clinical neurophysiologist who is a neurologist with special training in clinical neurophysiology. The time required to complete the study generally takes approximately 60 to 120 minutes. The two main procedures used to study nerves and muscles are needle electromyography (EMG) and nerve conduction velocity studies (NCV). 

EMG
During an EMG, the neurologist analyses the electric activity in muscles by inserting a fine needle electrode into selected muscles. Needle insertion may cause mild temporary discomfort. The needle is not used for injection and no shocks are given. The physician can determine whether the muscle is working normally by seeing the electric activity on a screen and listening over a loudspeaker. The needles are discarded after use or sterilized to prevent the transmission of AIDS, hepatitis and other infections.

NCV
To perform nerve conduction studies, the physician tapes small metal electrodes on the skin and applies a brief electric stimulus to one portion of a nerve. Nerve stimulation will cause a tingling sensation. The physician can then evaluate the electric response of the nerve or muscle to which the nerve is attached and determine if the nerve impulse is a) conducted normally, b) at a slow speed or c) not transmitted at all, suggesting damage to the nerve.

Evoked Potentials
Electro diagnosis may also include a number of other tests, such as evoked potentials. These studies use different stimuli, such as auditory clicks, a changing visual pattern such as a checkerboard, or small electric stimuli applied to specific nerves. The recordings are made over the surface of the head and the spine to evaluate whether the sensory impulses are conducting normally through the nerves, spinal cord or brain.

Special Precautions
The patient does not need to do anything special to prepare for this test, except to keep the skin free of any lotions or emollients on the day of the examination. Be sure to inform the physician, however, if you are taking blood-thinning medication such as Coumadin, have hemophilia or a cardiac pacemaker. Patients with myasthenia gravis should ask their physician whether or not to take anti-cholinesterase medications on the day of the test.

EEG
EEG is the single most important laboratory test in the evaluation of patients with seizures and related disorders. It is a painless procedure, during which the brain's electrical activity detected by electrodes pasted to the scalp is amplified and recorded. The test lasts for approximately one hour. Patients are advised to keep their hair free of any oil and grease and not to be fasting before the test. They should also continue taking any medicines prescribed to them. At Apollo Hospitals, advanced computerised Digital EEGs offer off-line data analysis for greater diagnostic yield.