Dubai Neurology - Neurological Tests

 
 


 

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  Evoked Potentials
 


 

Introduction:

Evoked Potentials are also referred to as evoked responses.  In these tests, the brain’s response to various stimuli is recorded.  The three commonly performed types of evoked responses are:

  • Visual evoked potentials (VEP).  During this procedure a light stimulus is presented to the patient.
  • Brainstem auditory evoked potentials (BAEP).  During this procedure a sound stimulus is presented to the patient.
  • Somatosensory evoked potentials (SSEP).  During this procedure an electric impulse is presented to the patient.  There are two common varieties of this test:

    Upper extremity (SSEP)
    Lower extremity (SSEP)

Where the test is performed:

These are outpatient procedures.  They can be performed in your physician’s office or in a hospital. 


Who performs these tests?

Evoked potential (EP) studies are performed by specially trained neurophysiology technologists.

How to prepare for the test:
  • Wash and dry your hair prior to testing, preferably the night before
  • Do not use conditioner, oils or any hair care products
  • If undergoing SSEP testing, do not use creams, lotions or moisturizers on your skin
  •  If you wear glasses or contacts, bring them with you.  You will be requested to wear them during the  test
  •  If you wear a hearing aid, bring it with you.  You will be requested to wear it during the test
  • Wear comfortable loose clothing
  • There are no dietary or activity restrictions neither before nor after the testing procedure

Visual Evoked Potentials:

This procedure tests the integrity of the visual pathway.  It is usually requested for patients with optic neuritis and for those suspected to suffer from multiple sclerosis.  At times it is also used to investigate patients with hysterical blindness.

You will be seated in a chair and instructed to look at a flashing checkerboard pattern.  Electrodes (small metal discs) will be fixed to your scalp with conducting gel and tape and the information is then transmitted via wires to the recording apparatus where it is displayed on a monitor.

The test is painless and usually requires 30-45 minutes to complete.


Brainstem Auditory Evoked Potentials:

This procedure tests the integrity of the auditory pathway.  It is usually requested for patients suspected to suffer from multiple sclerosis or from an acoustic neuroma (a small tumor of the auditory nerve) or to evaluate the integrity of the brainstem.

You will be instructed to lie on a bed or to sit in a reclining chair with headphones. Electrodes (small metal discs) will be fixed to your scalp with conducting gel and tape. You will be asked to close your eyes and relax. You may go to sleep. A clicking sound or tones are presented to one ear at a time and the response is displayed on a monitor.

The test is painless and usually requires about 45 minutes to complete.


Somatosensory Evoked Potentials:

This procedure tests the integrity of the sensory pathways from either the upper or lower limbs.  It may be requested to investigate the complaints of pain, weakness or numbness.

You will be instructed to lie on a bed and relax.  Electrodes (small metal discs) will be fixed to your scalp, neck, back and limbs with conducting gel and tape.  Weak electric impulses are applied to a nerve at the wrist or ankle and the response is displayed on a monitor.

The electric impulses may be transiently uncomfortable but are not usually described as painful by patients.  Occasionally patients fall asleep during the procedure.  The duration of the test is usually about 60 minutes. 


 
  Neurological Tests

Electroencephalogram Brain wave test (EEG)
Nerve Conduction Studies (NCS) & Electromyography (EMG)
Evoked Potentials
Carotid Ultrasound
Computerized Axial Tomography (CT Scan / CAT Scan)
Magnetic Resonance Imaging (MRI)
Lumbar Puncture
Angiography
© 2006 D M Kayed, MD, FAAN Dubai Neurology
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