Testing For Nerve Damage (Vid)

Today's post from news-medical.net (see link below) looks at common testing methods for neurological dysfunction. If you have ever been tested for nerve damage and been given a nerve damage diagnosis based on the results, you may be none the wiser coming out of the testing room than before you went in. This article explains exactly what sort of neurological testing is currently available and how each one works, so after reading it, you may be a little more enlightened as to what they were looking for. That said, many sensible doctors and neurologists can give you the same diagnosis based on your story and symptoms alone, without going to the expense of what can be an unreliable series of tests. Many people end up being given an idiopathic neuropathy diagnosis, purely based on the fact that the tests can't pin point the cause of your nerve damage and in many cases can't explain what seem to be 'negative' results. For that reason, many people leave the neurologist feeling somewhat cheated by the testing system and disbelieved and mistrusted as well. This leads to frustration on the part of the patient and delays in effective symptom treatment. Nevertheless, it's a double-edged coin because both doctor and patient may want the testing in order to prove the existence of your condition and not leave everybody in doubt. It's very unsatisfactory all round but if you are or have been tested, it's useful to know the why's and wherefore's of the tests and this article does just that.

Neurophysiology And Nerve Conduction StudiesBy Liji Thomas, MD Last Updated: Oct 31, 2016

Neurophysiology is a discipline within the health sciences which deals with the measurement and assessment of nervous system function rather than the anatomy of the nervous system. It helps to diagnose and monitor the progress of nervous disorders.

Neurophysiological assessment is performed via electrodes attached to the patient’s skin, and in many cases the patient’s cooperation is essential.





Clinical neurophysiology is a branch of this discipline which is hospital-based, and has to do with measuring neurological parameters, in a research setting, at the patient’s bedside, in intensive care units, or in a dedicated hospital laboratory. Clinical neurophysiologists test and record the function of the brain, spinal cord, spinal nerve roots, peripheral nerves (sensory and motor) and muscles, to help diagnose various disorders of the nervous system. They may use computerized imaging, magnetic, electrical, or electronic ways to record nervous activity, nerve impulse conduction, and coordination with the muscular response.

Some conditions in which this is useful include epilepsy, Parkinson’s disease, and motor neuron disease.

Tests used in neurophysiology

Diagnostic evaluations undertaken in the department of neurophysiology include:
Electroencephalogram (EEG)
Evoked Potentials (EPs)
Nerve conduction studies (NCS)
Electromyography (EMG) 

Electroencephalogram (EEG)

The EEG is a record of brain function. Electrodes are attached to the scalp in various areas, corresponding to the lobes of the brain, to pick up the electrical potentials from the cortex of the brain. This is of particular use in patients suffering from epilepsy.

Evoked potentials (EPs)

Evoked potentials occur in response to a visual stimulus. They are of use mainly in nervous diseases such as optic neuritis or multiple sclerosis.

Nerve conduction studies

In many conditions it is necessary to test the way the peripheral nervous system functions, by measuring the speed of passage of nerve impulses through the motor and sensory nerves. This is by recording the effect of applying a small electrical current to the nerves to be tested.

The test, also called a nerve conduction velocity test, helps to determine if the nerve has been damaged or destroyed.

Surface patch electrodes are attached to the skin. One supplies stimulation to the nerve. The other records the resulting nerve impulse. The speed of conduction is calculated using the distance between the electrodes and the time gap between the stimulation and the arrival of the resultant electrical impulse at the other electrode. Each nerve is tested separately.

Electromyography

Electromyography is a related test which inserts slender electrodes into the voluntary muscles, to diagnose conditions such as motor neuron disease and radiculopathy. It measures the electrical activity in the muscle fibers, and shows if the muscles or nerves are damaged, and if so, to what extent and at what location.

More specialized tests in neurophysiology include:
Ambulatory EEG for long-term monitoring
Video telemetry
Sleep studies
Monitoring patients during neurosurgical procedures, such as scoliosis surgery, where the spinal cord integrity has to be mapped throughout
Tests of visual neuron functioning

Neurophysiologists may develop a greater interest in specific areas such as epilepsy and its origin as well as corrective surgery, Parkinson’s disease and sub-thalamic nuclear ablation, and mapping the cortex in various disorders.

The responsibilities of a neurophysiologist include supervising and supporting technicians in the wards, operation theaters, and departmental laboratories. They must report EEGs and interpret EMGs to diagnose various neuromuscular conditions.

References
https://www.healthcareers.nhs.uk/explore-roles/medicine/clinical-neurophysiology
http://jnnp.bmj.com/content/76/suppl_2/ii23.full
https://www.uclh.nhs.uk/OurServices/ServiceA-Z/MEDSPEC/NPHYS/Pages/Home.aspx
http://www.uhs.nhs.uk/OurServices/Brainspineandneuromuscular/NeuromuscularWERMANS/Diagnosisandtreatment/Nerveconductionstudiesandelectromyography.aspx
http://www.hopkinsmedicine.org/healthlibrary/test_procedures/neurological/nerve_conduction_velocity_ncv_92,P07657/
 
http://www.news-medical.net/health/Neurophysiology-Nerve-Conduction-Studies.aspx