Neil A. Busis, M.D.,
EMG Medical Advisory Board
What is an H & F
Wave and why are
they done?
What are F Waves?
When a motor nerve is stimulated and the electrical response of a muscle that it
innervates is displayed on an electromyography screen, several responses can be
observed. The initial response is the largest in amplitude and is termed the
"compound muscle action potential" (CMAP). Some time after the CMAP, several
smaller responses are seen. These are called "F-waves." Action potentials in the
motor nerve fibers that are caused by electrical stimulation actually travel in two
directions. The action potentials that travel directly from the point of stimulation to
the muscle elicit the CMAP. Some action potentials actually travel in the other
direction on the nerve fibers, all the way to the motor neuron cell bodies in the spinal
cord. These action potentials then travel back down to the nerve fibers to stimulate the
muscles a second time, after a brief delay. That is why F-waves are called "late
responses" - they are responses later than the CMAP.
What are H Waves?
When the tibial nerve is electrically stimulated behind the knee with just the right
settings, a late response is observed called the "H-reflex". H-reflexes are the
electrical equivalent of a deep tendon reflex. Late responses are valuable methods to
evaluate nerve conduction in portions of the nerve that are relatively proximal (that is,
near the spine) and, therefore, inaccessible to direct assessment using conventional
techniques.
What conditions do they diagnose?
F-wave and H-reflex studies provide information in the evaluation of
radiculopathies, plexopathies, polyneuropathies. In some cases, they may be the
only abnormal study. The physician's report should identify the nerves evaluated and
the F-wave and H-reflex characteristics.
NEIL A. BUSIS M.D.
INTRODUCTION
Dr. Busis graduated from Yale University and
went on to receive his Medical Degree from the
University of Pennsylvania School of Medicine.
He obtained his postdoctoral residency training
in Neurology at Massachusetts General
Hospital in Boston, Massachusetts.
Dr. Busis is a Board Certified Neurologist. He
received board certification in 1989 by the
American Board of Electrodiagnostic Medicine.
He also holds his specialty boards in Clinical
Neurophysiology from the American Board of
Psychiatry and Neurology.
Dr. Busis is the Director of the Neurodiagnostic
Laboratory and Chief of the Neurology
Division at UPMC Shadyside, and is a Clinical
Associate Professor of the Department of
Neurology at the University of Pittsburgh,
School of Medicine. He also is President of the
Pittsburgh Neurology Group, Inc. in Pittsburgh,
Pennsylvania.
Dr. Busis is a Consultant on Current Procedural
Terminology (CPT) coding, documentation and
reimbursement for neurological procedures. An
active member and past president of American
Association of Electrodiagnostic Medicine
(AAEM), Dr. Busis represented the AAEM on
the American Medical Association (AMA) CPT
Advisory Committee. He has represented the
American Academy of Neurology on the AMA
Relative Value Scale Update (RUC) Advisory
Committee, and the AMA Practice Expense
Advisory Committee and served as a member
of the Clinical Practice Expert Panel (CPEP) for
Evaluation and Management Codes.
(*See reverse side for definitions)
“Before this class, I was unclear about what I
was looking for on these reports. Now I feel
comfortable that I can ask the right questions
to get the best results.”
- Juletta A. Tyson
Investigative Case Manager, Travelers
Q: Can both CPTTM code 95900 (motor nerve
conduction study, without F-wave) and CPTTM
code 95903 (motor nerve conduction study, with
F-wave) be billed for the same nerve?
A: These CPTTM codes cannot be billed for the
same nerve as the reimbursement for CPTTM code
95903 includes both a Nerve Conduction Study
(NCS) and an F-wave study.
Current Connection
Clinical Definitions
Amplitude: The height of the CMAP (Compound Motor Action Potential) or SNAP
(Sensory Nerve Action Potential) obtained during nerve conduction studies measured from
baseline to peak. The motor amplitude is measured in millivolts (mV) and the sensory nerve
in microvolts (uV).
Distal Latency: A measurement of the time it takes following nerve stimulation until the
appearance of a motor or sensory potential. Latency for the motor nerve is at the beginning of
the curve and for sensory it is at the peak. Latency is usually measured in milliseconds
(msec).
Conduction Velocity: Speed of electrical conduction along a nerve expressed as meters
per second.
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In Our Next
Issue:
Radiculopathy: disease or compression of the spinal nerve root.
Neuropathy: disease of a nerve. The term describes dysfunction of one (mononeuropathy),
or many nerves (polyneuropathy or peripheral neuropathy).
Plexopathy: disease of a nerve plexus (a network of nerves) such as brachial (subclavicular)
Learn more
from another
distinguished
member of our
Medical
Advisory Board
plexopathy.
Myopathy: disease of the muscle.
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The Current Connection and a directory of open EMG states can be viewed at OCM’s website: http://www.onecallmedical.com