**Abstract:**  
  
Short-latency somatosensory evoked potentials (SEPs) represent
electrophysiologic responses of the somatosensory pathways to stimulation.
Somatosensory testing involves the application of a series of brief electrical
stimuli over peripheral nerves (e.g., the median, peroneal, and tibial nerves)
and recording the resulting evoked potentials over proximal portions of the
nerves and central pathways which were stimulated, the plexus, spine and/or
scalp. Action potentials recorded from these sites are averaged by a computer
to improve signal clarity, and then displayed in standard formats on the
computer's screen as well as in printed form.  
  
A physician trained in interpreting clinical evoked potential studies analyzes
the waveforms. The waveforms obtained should be described by nerves being
stimulated, the recording sites, peak latencies, interpeak intervals (when
appropriate), and amplitudes of the significant components. The nerves most
commonly stimulated are the median nerves at the wrist for testing in the
upper extremity, and the posterior tibial nerve at the ankle or common
peroneal nerve (CPN) at the knee for the lower extremity.  
  
SEPs evaluate the entire somatosensory pathway from the site of stimulation up
to the cerebral cortex. It is possible to distinguish between lesions located
in the peripheral nerve, in the dorsal column spinal cord pathway, or higher
centers in the brain up through the cortex. In general, there is no need for
SEP in the diagnosis of most peripheral neuropathies, because the conventional
nerve conduction studies or needle electromyography (EMG) can identify these
types of lesions and no added information is obtained from SEP. This local
coverage determination (LCD) discusses medically necessary indications and
limitations for SEPs.  
  
 **Indications:**  
  
Medicare will consider the use of short-latency SEPs to be medically
reasonable and necessary to assist in the diagnosis of certain neuropathologic
states (as described below), in order to provide information for treatment
decisions and also for intraoperative electrophysiological monitoring during
spinal surgeries, in which there is risk of additional nerve or spinal cord
injury. However, it is not anticipated that such monitoring will be medically
necessary for the typical cervical or lumbar root decompression procedures.  
  
SEPs are used to evaluate the more proximal segments of nerves and the
integrity of the central somatosensory pathways, when abnormality of
conduction through the brain and/or brainstem, spinal cord, and/or peripheral
nerves is suspected. This utilization would include conditions such as
multiple sclerosis, cervical spondylosis with myelopathy, coma, spinal cord
trauma, myoclonus, Friedreich's ataxia, syringomyelia, spinal cord tumors,
spinal stenosis and other conditions where there is spinal cord compression.  
  
 **Limitations:**  
  
SEP studies are appropriate only when a detailed clinical history, neurologic
examination and appropriate diagnostic tests such as imaging studies,
electromyogram, and nerve conduction studies make a lesion (or lesions) of the
central somatosensory pathways a likely and reasonable differential diagnostic
possibility.  
  
Nurse practitioners, clinical nurse specialists, and physician assistants are
not defined as physicians; therefore, they may not function as supervisory
physicians under the diagnostic tests benefit. However, when these
practitioners personally perform diagnostic tests, as provided they may do so
in pursuant to State scope of practice laws and under the applicable State
requirements for physician supervision or collaboration.  
  
Reasonable and necessary services are ordered and/or furnished by qualified
personnel. Provision of interpretation and/or supervision of these tests will
be considered medically reasonable and necessary, only if performed by
appropriately trained providers.  
  
**Other Comments:**  
  
Limitation of liability and refund requirements apply when denials are likely,
whether based on medical necessity or other coverage reasons. The
provider/supplier must notify the beneficiary in writing, prior to rendering
the service, if the provider/supplier is aware that the test, item or
procedure may not be covered by Medicare. The limitation of liability and
refund requirements do not apply when the test, item or procedure is
statutorily excluded, has no Medicare benefit category or is rendered for
screening purposes.  
  
For outpatient settings other than Comprehensive Outpatient Rehabilitation
Facilities (CORFs), references to "physicians" throughout this policy include
nonphysicians, such as nurse practitioners, clinical nurse specialists and
physician assistants. Such nonphysician practitioners, with certain
exceptions, may certify, order and establish the plan of care as authorized by
State law.