Electroneurography

Electrophysiology

1. ELECTRONEUROGRAPHY
Electrophysiological
Principals involved
And
Clinical Diagnosis

2. ELECTRONEUROGRAPHY:
Electroneurography is a non invasive, electro
neurological diagnostic test to measure the
conduction velocity and latency of peripheral
nerves.
It is the most accurate test for detecting and
locating peripheral nerve injury of about 100
kinds of peripheral neuropathies.
Such as Diabetic polyneuropathy, Gullain-
Barre syndrome, Carpel tunnel syndrome,
thoracic outlet syndrome

3. Working Principal:
Conduction velocity is the rate of propagation
of nerve impulse (action potential) along a
nerve fiber.
NCV determine the distance covered by AP
per unit time, NCV = lambda /time

4. Factors affecting NCV:
1. Diameter of the axon
Different peripheral
nerve fibers have
different diameters
and thus conduction
velocity of their own.
AP recorded are
Compound AP.

5. 2: MYELINATION:
Myelination induces insulation around the
fiber except small points known as nodes of
Ranvier
Thereby increases resistance across
membrane Rm but decreases its capacitance
Cm
AP are saltatory in nature

8. Other Factors
Temperature as proportional to velocity
External resistance Rl
Density of gates
Ions concentrations
Anesthetics
Anoxia

9. HOW THE TEST IS PERFORMED
STRONG BUT BRIEF STIMULATION AT ONE POINT
UNDER THE SKIN AND AT THE SAME TIME RECORDING
THE ELECTRICAL ACTIVITY AT ANOTHER POINT OF
NERVE TRAJECTORY IN THE BODY.
The response is displayed on the video monitor of
computer or cathode ray tube.
The stimulus and recordings are carried out by
the surface or disc electrodes which are placed
over the skin after applying the conducting gel.
Stimulus is felt as the electrical shock thus may
be painful.

10. Thoracic
Outlet
Syndrome

11. Observations And Diagnosis:
Sometimes EMG is combined with ENoG for
accurate diagnosis called as
electromyoneurography
Any decrease in the NCV will indicate:
1.Extent of demyelination of nerve
2. Any Conduction Block
3.Axonopathy (damage to the long
portion of a nerve cell)

12. CLASSIFICATION OF PERIPHERAL NEUROPATHIES:

13. References:
Neurophysiology:
3rdedition by R.H.Carpenter
Nerve Conduction studies:
https://backyardbrains.com/experiments/comparingNerveSpeed
https://Hmphysiology.blogspot.com
peripheral neuropathy:
Physical medicine and rehabilitation Board
review – Sara Cuccuvullo MD

14. For Further Reading:
http://openwetware.org/wiki/Lab_9:_Conduction_Velocity_of_Nerves
http://www.neurolist.com/site/emg_case.htm
Happy Reading !