Neurophysiological Testing
Neurophysiological Testing
Accurate diagnosis is a critical in proper medical treatment decision making. At the Miami Back Institute we utilize state of the art diagnostic testing procedures to provide our physicians with the tools to make the correct diagnosis and best treatment decisions for our patients. Neurophysiological testing is an important component in this process.
Neurophysiological Testing
- Electromyogram (EMG) Testing
- Nerve Conduction Velocity
- Evoked Potentials (EP)
- Somatosensory Evoked Potentials
- Dermatosensory Evoked Potentials
- H-Reflex
- Electroencephalograms (EEG)
Electromyogram (EMG)
This test, most commonly performed by neurologists involves measuring the conduction and signals across nerves and muscles. It is usually ordered to diagnose a neuropathy (nerve dysfunction) such as seen in nerve damage or neurologic disease. The test may be best suited to assess nerve disruption and recovery after trauma but can be helpful in differentiating between peripheral nerve problems (diabetes, crush injury) and more central nerve problems (nerve root compression, spinal cord injury).
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NCV— Nerve Conduction Velocity
NCV tests the peripheral nervous system to the arms, legs, and face. This test checks both sensory and motor nerve fibers. Nerve conduction velocity studies diagnose different entrapment neuropathies, such as carpal tunnel syndrome, as well as ulnar, radial, peroneal, femoral, posterior tibial, and peripheral neuropathies. The test checks axonal loss, demyelination of the peripheral nerves, and conduction blocks. It is useful in diagnosing anterior horn cell diseases, as seen in amyotrophic lateral sclerosis, and neuromuscular junction problems, such as myasthenia gravis. The test differentiates inherited neuropathies such as Charcot-Marie-Tooth and Dejerine-Sottas entrapment neuropathies (avoiding multiple unnecessary surgeries).
The EMG / NCV can provide the following information:
- Presence of a nerve injury
- Age of the nerve injury (acute vs. chronic process)
- Area of the nerve injury (proximal vs. distal)
- Severity of the nerve injury
- Whether the nerve is healing
NCVs aid in the evaluation of:
- Herniated Disks
- Peripheral neuropathies
- Numbness and tingling
- Pain in the extremities
- Atrophy
- Entrapment neuropathies
- Thoracic outlet syndrome
- Radiculopathies
- Carpal tunnel syndrome
- Tarsal tunnel syndrome
- Trauma to nerves
- Motor/sensory deficits
- Hot/cold sensation
- Neuritis
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EP— Evoked Potentials
Evoked potentials measure nerve impulses as they travel along the central nervous system. The three primary evoked potential modalities are somatosensory, auditory, and visual. Each of these involves a different nerve pathway.
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SSEP— Somatosensory Evoked Potential
Mixed nerve somatosensory evoked potentials test both sensory and motor nerve fibers in the peripheral nervous system to the spinal cord. In an upper profile (cervical and extremities), the pure sensory nerves and myelin sheath which ascend to the sensory cortex in the central nervous system can be tested by means of interpeak measurements. This test determines if there are any demyelinating lesions in the peripheral nerves. Brachial plexus or central nervous system medial, ulnar, and radial nerves can be tested with this procedure. The lower profile (lumbar and extremities) SSEP usually studies the posterior tibial nerve.
SSEPs aid in the evaluation of:
- Abnormal skin sensation
- Nerve root compression
- Spinal cord tumor
- Spinal trauma or injury
- Cervicobrachial syndrome
- Thoracic outlet syndrome
- Multiple sclerosis
- Herniated discs
- Radiculopathy
- Neuritis
- Myelopathy
- Numbness and tingling
- Burning sensation
- Diabetes
- Plexopathy
Other tests that complement the SSEP:
- Dermatosensory evoked potential (DEP)
- Nerve conduction velocity (NCV)
- Musculoskeletal or spinal ultrasound
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DEP— Dermatosensory Evoked Potential
This is a test of specific nerve roots. The upper profile (cervical and extremities) usually includes C6, C7, and C8 nerve roots. The lower profile (lumbar and extremities) usually includes L4, L5, and S1 nerve roots. This is a very valuable diagnostic procedure for trauma patients where one suspects radiculopathy. In most trauma cases, the sensory nerves are affected before the motor fibers, and a dermatosensory study can aid in diagnosing an early radiculopathy.
DEPs aid in the evaluation of:
- Carpal Tunnel Syndrome
- Thoracic outlet syndrome
- Plexus stretch injury
- Nerve root irritation-Motor/sensory deficits
- Cord injury
- Neuritis
- Radiculitis
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H-reflex Study
Tests the response of muscle stretch receptors, nerve conduction, spinal neuron activity, and muscle contractions. A useful neurodiagnostic test for the diagnosing of an S1 radiculopathy.
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Electroencephalograms (EEG)
EEGs are often necessary to rule out seizure activity and to look for focal slowing of the brain that would indicate injury of the brain.
Uses of Neurophysiological Testing
NCV, needle EMG and SSEP testing are proven procedures valuable in diagnosing many neurological conditions.
Back Injuries
Lumbosacral Radiculopathy
Neck Injuries
Cervical Radiculopathy
Peripheral Polyneuropathies
Diabetes
Repetitive Motion Injuries
Carpal Tunnel
Nerve Compressions / Entrapments:
Ulnar Neuropathy
Peroneal Neuropathy
- Tarsal Tunnel
- Carpal Tunnel
- Femoral Neuropathy
- Facial Nerve Palsy
- Thoracic Outlet Syndrome
- Pronator Teres Syndrome
NCV and EMG testing is useful in differentiating between and/or diagnosing many neurological disorders. SSEP testing is useful in testing the integrity of the sensory or afferent pathways of the nervous system.
Common disorders of a COMPRESSIVE nature include:
CARPAL TUNNEL SYNDROME (CTS): CTS is a median nerve compression at the level of the wrist. This compression is usually caused by excessive use or repetitive wrist movements. i.e. typing, heavy labor.... Ganglion cysts may also contribute to this disorder. CTS is common among peripheral polyneuropathy patients. i.e. diabetics. The patient may present with numbness, tingling, or pain in the wrist area or first three digits. Some patients have difficulty grasping objects or more commonly find themselves dropping things. Patients often complain of hand numbness at night that awakens them from sleep. This symptom generally goes unreported since patients believe that they 'slept on their hand wrong'.
ULNAR NEUROPATHY: Ulnar neuropathy is an ulnar nerve compression most commonly found at the level of the elbow. The patient usually presents with numbness or tingling in the fourth and fifth digits. Weakness of the ulnar innervated hand muscles may also occur. Ganglions are often the cause for an ulnar nerve compression at the level of the wrist.
PERONEAL NEUROPATHY: (Foot Drop) Peroneal neuropathy is a compression of the peroneal nerve at the level of the fibular head. These patients present with an irregular gait caused by a foot drop or loss of extensor control of the digits. This injury can be traumatic in nature or is seen in patients who sit with their legs crossed or squat for long periods of time. This is commonly seen in patients who are bedridden for long periods of time or have had their leg immobilized during a surgery.
TARSAL TUNNEL SYNDROME (TTS): TTS is a compression of the tibial nerve at the level of the ankle. This lesion can be caused by ankle trauma, ganglion cysts, or tenosynovitis. This syndrome is difficult to diagnose in peripheral polyneuropathy patients. Patients usually present with numbness and or pain in the sole or digits of the foot. Some patients experience weakness in the intrinsic foot muscles.
RADICULOPATHY: Cervical or Lumbosacral Radiculopathies are compressions of one or more nerve roots at the spinal level. Radiculopathies can be caused by bulged or herniated discs, arthritic changes of the spine, tumors, or traumatic root avulsion. Patients usually present with pain radiating from the spine into the extremities and/or numbness and tingling in dermatomal patterns.
GENERALIZED DISORDERS:
POLYNEUROPATHY: The most common polyneuropathy is an acquired peripheral polyneuropathy. The most common is caused by diabetes, but renal disease, alcoholism, toxic insults, nutritional disorders, and malignancies are also common. The patient presents usually with sensory changes in a 'glove and stocking' distribution. Weakness in distal muscles is common as well as hyporeflexia. It is important to note that patients with polyneuropathies are very susceptible to entrapment or compressive neuropathies. Many of these superimposed compressive neuropathies are overlooked due to the underlying nerve damage caused by their peripheral polyneuropathy. Some polyneuropathies are inherited.
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