Evoked potential studies are recorded electrical responses to stimulation of a sensory system. When a sensory impulse reaches the brain, a specific Electroencephalographic (EEG) response is produced (evoked) in the cortical area appropriate to the modality and site of the stimulus. By computer averaging techniques, the evoked responses of repetitive stimuli can be separated from the spontaneous EEG activity. Evoked potentials are clinically useful in evaluating the functional integrity of the somatosensory or special sensory pathways. Different latencies and wave patterns help to localize lesions ranging from the end organ through the nervous system to the cerebral cortex. Often defects in these pathways are not otherwise evident. Evoked potentials are also used to monitor neural pathways when patients are anesthetized during surgery and to document brain death. The following are tests that evaluate potentials evoked by stimulation of the peripheral or cranial nerves:
SEPs/SERs evaluate the pathways from nerves in the extremities through the spinal cord, to the brainstem or cerebral cortex upon stimulation of peripheral axon. Some conditions where SEPs have demonstrated usefulness include, but are not limited to the following: spinal cord trauma; subacute combined degeneration; non-traumatic spinal cord lesions, e.g., cervical spondylosis; multiple sclerosis; spinocerebellar degeneration; myoclonus; coma; and intraoperative monitoring of spinal cord, brainstem and brain sensory tracts.
SEP has an advantage in that it evaluates the entire somatosensory pathway and it is possible to distinguish between lesions located in the peripheral nerve, in the dorsal column pathway, or both. There is no need for SEP in the diagnosis of most neuropathies because the conventional nerve conduction study can identify them and no added information is obtained from SEP.
VEPs/VERs evaluate the visual nervous system pathways from the eyes to the occipital cortex of the brain. VER or VEP involves stimulation of the retina and optic nerve with a shifting checkerboard pattern or flash method. This external visual stimulus causes measurable electrical activity in neurons within the visual pathways. This is called the Visual Evoked Response (VER) and is recorded by electroencephalography electrodes located over the occiput. Using special computer techniques, the evoked responses measured over multiple trials are amplified and averaged. A characteristic waveform is produced. With pattern-shift VER, the waveform normally appears as a straight line with a single positive peak (100 msec after stimulus presentation). Abnormalities in this characteristic waveform may be seen in a variety of pathologic processes involving the optic nerve and its radiations. Pattern-shift VER is a highly sensitive means of documenting lesions in the visual system. It is especially useful when the disease process is subclinical, e.g., ophthalmologic exam is normal and patient lacks visual symptoms.
BAEPs/BAERs evaluate the auditory nerve pathways from the ears through the brain stem. A clicking sound is presented to one ear at a time. The electrical activity of this signal is recorded by electrodes on the scalp. The averaged response is displayed as a waveform that contains peaks and troughs, which correspond to various points along the hearing pathway. The time between these peaks is measured and compared to normal data. A delay in a component of the response might indicate an abnormality at specific anatomic sites in the acoustic nerve or brainstem.
Somatosensory Evoked Potentials (SEP) (CPT codes 95925, 95926, 95927) are appropriate for the following indications:
- Spinal cord trauma.
- Degenerative, non-traumatic spinal cord lesions.
- Cervical spondylosis.
- Multiple sclerosis.
- Spinocerebellar degeneration.
- Asymmetric hearing loss.
- Unilateral tinnitus.
- Sudden hearing loss.
- Suspected cerebellopontine angle tumor.
- Suspected demyelinating disorder.
- Suspected functional hearing loss.
- Ototoxic drug therapy monitoring including chemotherapy or antibiotics.
- Suspected auditory neuropathy.
- Suspected acoustic neuroma.
- Posterior fossa surgery.
- Cochlear implant.
- Cochlear implant.
- Confirm diagnosis of multiple sclerosis when clinical criteria are inconclusive.
- Detect optic neuritis at an early, subclinical stage.
- Evaluate diseases of the optic nerve, such as:
- Ischemic optic neuropathy.
- Pseudotumor cerebri.
- Toxic amblyopias.
- Nutritional amblyopias.
- Neoplasms compressing the anterior visual pathways.
- Evaluate optic nerve injury.
- Hysterical blindness (to rule out).
- Monitor the visual system during optic nerve (or related) surgery (monitoring of short-latency evoked potential studies).
- Safe and effective.
- Not experimental or investigational (exception: routine costs of qualifying clinical trial services with dates of service on or after September 19, 2000, which meet the requirements of the clinical trials NCD are considered reasonable and necessary).
- Appropriate, including the duration and frequency that is considered appropriate for the service, in terms of whether it is:
- Furnished in accordance with accepted standards of medical practice for the diagnosis or treatment of the patient’s condition or to improve the function of a malformed body member.
- Furnished in a setting appropriate to the patient’s medical needs and condition.
- Ordered and furnished by qualified personnel.
- One that meets, but does not exceed, the patient’s medical need.
- At least as beneficial as an existing and available medically appropriate alternative.
Providers are reminded to refer to the long descriptors of the CPT codes in their CPT book. The American Medical Association (AMA) and the Centers for Medicare & Medicaid Services (CMS) require the use of short CPT descriptors in policies published on the Web.
C motor evoked, uppr limbs
C motor evoked, lwr limbs
Visual evoked potential test
Meningococcal optic neuritis
Encephalomyelitis due to rubella
Other specified mosquito-borne viral encephalitis
Russian spring-summer (taiga) encephalitis
Tick-borne viral encephalitis
Viral encephalitis transmitted by other and unspecified arthropods
Malignant neoplasm of vertebral column excluding sacrum and coccyx
Malignant neoplasm of cranial nerves
Malignant neoplasm of other specified sites of nervous system
Secondary malignant neoplasm of brain and spinal cord
Benign neoplasm of brain
Benign neoplasm of other specified sites of nervous system
Neoplasm of uncertain behavior of pituitary gland and craniopharyngeal duct
Neoplasm of uncertain behavior of brain and spinal cord
Neoplasm of uncertain behavior of other and unspecified parts of nervous system
Neoplasm of unspecified nature of brain
Other degenerative diseases of the basal ganglia
Other acquired torsion dystonia
Other spinocerebellar diseases
Syringomyelia and syringobulbia
Acute (transverse) myelitis nos
Other demyelinating diseases of central nervous system
Flaccid hemiplegia and hemiparesis affecting unspecified side
Spastic hemiplegia and hemiparesis affecting unspecified side
Other specified hemiplegia and hemiparesis affecting unspecified side
Unspecified hemiplegia and hemiparesis affecting unspecified side
Other specified infantile cerebral palsy
Benign intracranial hypertension
Other specified trigeminal nerve disorders
Other facial nerve disorders
Disorders of olfactory (1st) nerve
Disorders of other cranial nerves
Unspecified disorder of cranial nerves
Brachial plexus lesions
Other nerve root and plexus disorders
Carpal tunnel syndrome
Other mononeuritis of upper limb
Lesion of sciatic nerve
Causalgia of lower limb
Other mononeuritis of lower limb
Mononeuritis of lower limb unspecified
Hereditary peripheral neuropathy
Other specified idiopathic peripheral neuropathy
Acute infective polyneuritis
Chronic inflammatory demyelinating polyneuritis
Other inflammatory and toxic neuropathy
Unspecified inflammatory and toxic neuropathies
Myasthenic syndromes in diseases classified elsewhere
Other specified myoneural disorders
Subjective visual disturbance unspecified
Binocular vision disorder unspecified
Visual field defect unspecified
Other color vision deficiencies
Night blindness unspecified
Other night blindness
Other specified visual disturbances
Optic atrophy unspecified
Drusen of optic disc
Optic neuritis unspecified
Other optic neuritis
Ischemic optic neuropathy
Other disorders of optic nerve
Disorders of optic chiasm associated with pituitary neoplasms and disorders
Disorders of other visual pathways associated with neoplasms
Disorders of visual cortex associated with neoplasms
Unspecified disorder of optic nerve and visual pathways
Meniere’s disease unspecified
Peripheral vertigo unspecified
Other peripheral vertigo
Vertigo of central origin
Labyrinthine fistula unspecified
Labyrinthine fistula of combined sites
Labyrinthine dysfunction unspecified
Other forms and combinations of labyrinthine dysfunction
Other disorders of labyrinth
Degenerative and vascular disorders unspecified
Noise effects on inner ear unspecified
Sudden hearing loss unspecified
Abnormal auditory perception unspecified
Disorders of acoustic nerve
Other disorders of ear
Conductive hearing loss
Conductive hearing loss of combined types
Sensorineural hearing loss unspecified
Central hearing loss, bilateral
Sensorineural hearing loss of combined types, bilateral
Mixed conductive and sensorineural hearing loss
Deaf mutism not elsewhere classifiable
Nontraumatic extradural hemorrhage
Unspecified intracranial hemorrhage
Occlusion and stenosis of basilar artery
Occlusion and stenosis of carotid artery
Occlusion and stenosis of vertebral artery
Occlusion and stenosis of multiple and bilateral precerebral arteries
Occlusion and stenosis of other specified precerebral artery
Occlusion and stenosis of unspecified precerebral artery
Cerebral artery occlusion unspecified
Basilar artery syndrome
Other specified transient cerebral ischemias
Cerebral aneurysm nonruptured
Dissection of aorta aneurysm unspecified site
Thoracic aneurysm ruptured
Aortic aneurysm of unspecified site without rupture
Cervical spondylosis with myelopathy
Spondylosis with myelopathy thoracic region
Spondylosis of unspecified site with myelopathy
Intervertebral disc disorder with myelopathy
Other disorders of cervical region
Adolescent postural kyphosis
Kyphosis (acquired) (postural)
Other kyphosis acquired
Lordosis (acquired) (postural)
Other lordosis acquired
Scoliosis (and kyphoscoliosis) idiopathic
Other kyphoscoliosis and scoliosis
Unspecified curvature of spine associated with other conditions
Other curvatures of spine associated with other conditions
Spina bifida unspecified region with hydrocephalus
Spina bifida unspecified region without hydrocephalus
Persistent vegetative state
Dizziness and giddiness
Abnormality of gait
Disturbance of skin sensation
Nonspecific abnormal response to unspecified nerve stimulation
Other nonspecific abnormal results of function study of peripheral nervous system and special senses
Closed fracture of c1-c4 level
Open fracture of c1-c4 level
Closed fracture of t1-t6 level
Open fracture of t1-t6 level
Closed fracture of lumbar spine
Closed fracture of sacrum and coccyx
Closed fracture of sacrum and coccyx with other spinal cord injury
Open fracture of sacrum and coccyx with unspecified spinal cord injury
Open fracture of sacrum and coccyx with other spinal cord injury
Closed fracture of unspecified vertebra with spinal cord injury
Concussion with prolonged loss of consciousness without return to pre-existing conscious level
Cortex (cerebral) contusion without open intracranial wound state of consciousness unspecified
Cortex (cerebral) contusion without open intracranial wound with concussion unspecified
Cortex (cerebral) contusion with open intracranial wound
Cortex (cerebral) contusion with open intracranial wound with concussion, unspecified
Cortex (cerebral) laceration without open intracranial wound with state of consciousness unspecified
Cortex (cerebral) laceration without open intracranial wound with concussion unspecified
Cortex (cerebral) laceration with open intracranial wound with state of consciousness unspecified
Cortex (cerebral) laceration with open intracranial wound with concussion unspecified
Cerebellar or brain stem contusion without open intracranial wound with state of consciousness unspecified
Cerebellar or brain stem contusion without open intracranial wound with concussion unspecified
Cerebellar or brain stem contusion with open intracranial wound with state of consciousness unspecified
Cerebellar or brain stem contusion with open intracranial wound with concussion unspecified
Cerebellar or brain stem laceration without open intracranial wound with state of consciousness unspecified
Cerebellar or brain stem laceration without open intracranial wound with concussion unspecified
Cerebellar or brain stem laceration with open intracranial wound with state of consciousness unspecified
Cerebellar or brain stem laceration with open intracranial wound with concussion unspecified
Other and unspecified cerebral laceration and contusion without open intracranial wound with state of consciousness unspecified
Other and unspecified cerebral laceration and contusion without open intracranial wound with concussion unspecified
Other and unspecified cerebral laceration and contusion with open intracranial wound with state of consciousness unspecified
Other and unspecified cerebral laceration and contusion with open intracranial wound with concussion unspecified
Subarachnoid hemorrhage following injury without open intracranial wound with state of consciousness unspecified
Subarachnoid hemorrhage following injury without open intracranial wound with concussion unspecified
Subarachnoid hemorrhage following injury with open intracranial wound with state of consciousness unspecified
Subarachnoid hemorrhage following injury with open intracranial wound with concussion unspecified
Subdural hemorrhage following injury without open intracranial wound with state of consciousness unspecified
Subdural hemorrhage following injury without open intracranial wound with concussion unspecified
Subdural hemorrhage following injury with open intracranial wound with state of consciousness unspecified
Subdural hemorrhage following injury with open intracranial wound with concussion unspecified
Extradural hemorrhage following injury without open intracranial wound with state of consciousness unspecified
Extradural hemorrhage following injury without open intracranial wound with concussion unspecified
Extradural hemorrhage following injury with open intracranial wound with state of consciousness unspecified
Extradural hemorrhage following injury with open intracranial wound with concussion unspecified
Other and unspecified intracranial hemorrhage following injury without open intracranial wound with state of consciousness unspecified
Other and unspecified intracranial hemorrhage following injury without open intracranial wound with concussion unspecified
Other and unspecified intracranial hemorrhage following injury with open intracranial wound with state of consciousness unspecified
Other and unspecified intracranial hemorrhage following injury with open intracranial wound with concussion unspecified
Late effect of injury to cranial nerve
Optic nerve injury
Injury to unspecified optic nerve and pathways
C1-c4 level spinal cord injury unspecified
T1-t6 level spinal cord injury unspecified
Lumbar spinal cord injury without spinal bone injury
Multiple sites of spinal cord injury without spinal bone injury
Injury to cervical nerve root and spinal plexus
Injury to multiple sites of nerve roots and spinal plexus
Injury to cervical sympathetic nerve excluding shoulder and pelvic girdles
Injury to other specified nerve(s) of trunk excluding shoulder and pelvic girdles
Injury to axillary nerve
Injury to sciatic nerve
Injury to multiple nerves of pelvic girdle and lower limb
Injury to superficial nerves of head and neck
Injury to multiple nerves in several parts
Long-term (current) use of antibiotics
Long-term (current) use of other medications