EEG, or electroencephalogram, is a tool we use to image the brain while it is performing a cognitive task. This allows us to detect the location and magnitude of brain activity involved in the various types of cognitive functions we study. EEG allows us to view and record the changes in your brain activity during the time you are performing the task. Images are acquired by using electrodes to monitor the amount of electrical activity at different points on your scalp.
Risks & Benefits EEGs are non-invasive and do not involve any X-rays, radiation, or injections. EEGs have been used for many years and are considered very safe. The electrodes record activity without producing any sensation. Slight redness may occur in the locations where the electrodes were placed, but this will wear off after a few hours. However, there may be risks depending on your specific medical condition, so we will screen for disorders such as epilepsy.
A nerve conduction study (NCS) is a test commonly used to evaluate the function, especially the ability of electrical conduction, of the motor and sensory nerves of the human body. Nerve conduction velocity (NCV) is a common measurement made during this test.
Purposes Nerve conduction studies are used mainly for evaluation of paresthesias (numbness, tingling, burning) and/or weakness of the arms and legs. The type of study required is dependent in part by the symptoms presented. A physical exam and thorough history also help to direct the investigation.
Some of the common disorders that can be diagnosed by nerve conduction studies are:
- Peripheral neuropathy
- Carpal tunnel syndrome
- Ulnar neuropathy
- Guillain-Barré syndrome
- Facioscapulohumeral muscular dystrophy
- Spinal disc herniation
Electromyography, or EMG, involves testing the electrical activity of muscles. Often, EMG testing is performed with another test that measures the conducting function of nerves. This is called a nerve conduction study. Because both tests are often performed at the same office visit and by the same personnel, the risks and procedures generally apply to both tests.
Muscular movement involves the action of muscles and nerves and needs an electrical current. This electrical current is much weaker than the one in your household wiring.
In some medical conditions the electrical activity of the muscles or nerves is not normal. Finding and describing these electrical properties in the muscle or nerve may help your doctor diagnose your condition.
EMG may aid with the diagnosis of nerve compression or injury (such as carpal tunnel syndrome), nerve root injury (such as sciatica), and with other problems of the muscles or nerves. Less common medical conditions include amyotrophic lateral sclerosis, myasthenia gravis, and muscular dystrophy.
People usually have a small amount of discomfort during EMG testing because of pin insertion. Disposable needles are used so there is no risk of infection.
During nerve conduction studies, small electrodes are taped to the skin or placed around fingers. You typically experience a brief and mild shock, which may be a bit unpleasant. Most people find it only slightly annoying.
No specific preparation is needed for the testing.
During the Procedure
During EMG, small pins or needles are inserted into muscles to measure electrical activity. The needles are different than needles used for injection of medications. They are small and solid, not hollow like hypodermic needles. Because no medication is injected, discomfort is much less than with shots.
- You will be asked to contract your muscles by moving a small amount during the testing.
- With nerve conduction studies, small electrodes will be taped to your skin or placed around your fingers. You typically will experience a mild and brief tingling or shock, which may be a bit unpleasant.
- The person who administers the test will explain the procedure. Often muscle activity is monitored through a speaker during the test, which may make a popping or soft roaring noise. The EMG technician will be looking at an oscilloscope, which looks like a small TV set during the procedure.
- Testing may take 30-60 minutes.
BERA (Brainstem evoked response audiometry), ABR (Auditory brain stem response), BAER (Brainstem auditory evoked response audiometry). BERA is an electro-physiological test procedure which studies the electrical potential generated at the various levels of the auditory system starting from cochlea to cortex.
Uses of BERA:
- It is an effective screening tool for evaluating cases of deafness due to retrocochlear pathology i.e. (Acoustic schwannoma). An abnormal BERA is an indication for MRI scan. The BERA test helps us not only in identifying lesions in the 8th cranial nerve, but also the lesions in the brainstem region which affect the auditory pathway. The BERA response obtained in a particular case will depend upon the nature, location, and size of the lesion;
- Used in screening newborns for deafness
- Used for intraoperative monitoring of central and peripheral nervous system
- Monitoting patients in intensive care units
- Diagnosing suspected demyelination disorders.
A visual evoked potential is an evoked potential caused by a visual stimulus, such as an alternating checkerboard pattern on a computer screen. Responses are recorded from electrodes that are placed on the back of your head and are observed as a reading on an electroencephalogram (EEG). These responses usually originate from the occipital cortex, the area of the brain involved in receiving and interpreting visual signals.
Loss of vision (this can be painful or non-painful);
- Double vision;
- Blurred vision;
- Flashing lights;
- Alterations in colour vision; or
- Weakness of the eyes, arms or legs.
Magnetic resonance imaging (MRI) is a procedure that uses magnetic fields and radiowaves to produce an image of the body in cross sections. This enables excellent images, particularly of soft tissue such as the brain and internal organs. MRI is generally used whenever X-Ray or ultrasound examinations do not deliver clear results.
Computed Tomography (CT) has witnessed a change over the past 20 years. It is said that the use of CT for applications in radiological diagnosis during the 70s sparked a revolution in the field of medical engineering. Innovative scanners, advanced applications were introduced in the CT technology that brought about exciting breakthroughs in clinical procedures that helped in addressing various public health issues. In the Indian scenario, CT technology has today become an indispensable and integral component of routine work in clinical and medical practice, specifically in radio-diagnosis and procedures such as colonography, cancer detection and staging, lung analysis, cardiac studies and radiotherapy planning.