Electrophysiology Flashcards
(17 cards)
Was ist eine EMG?
It is a term used in two ways:
- As a general description of the combination of NCS and needle EMG testing.
- More specifically, to describe the needle electrode recording performed to assess the function of motor units.
EMG steht für Elektromyographie.
Was ist eine NCS?
NCS may be performed on either sensory or motor nerves. From the skin surface, a brief electrical stimulus is applied to the nerve of interest, and the evoked electrical signal is recorded distally from another point in the nerve in the case of a sensory nerve or from the innervated muscle in the case of a motor nerve; the evoked responses are known as SNAP or CMAP, respectively.
NCS steht für Nervenleitgeschwindigkeit.
Nennen Sie andere Arten elektrodiagnostischer Tests.
-
Repetitive stimulation studies
- Somatosensory evoked potentials
- Other less frequently used tests include single-fiber EMG, motor-evoked potentials, and nerve root stimulation.
Was ist eine motorische Einheit?
A motor unit includes the motor neuron found within the anterior horn of the spinal cord, its axon, the neuromuscular junction, and the associated muscle fibers supplied by the axon.
Was sind die klinischen Indikationen für eine EMG?
An EMG should be ordered to determine the localization and severity of a suspected neuromuscular disorder. The NCS and needle EMG are almost always performed together in reputable laboratories. Testing can distinguish between neurogenic, myopathic, and neuromuscular junction disorders.
Was sind häufige Erkrankungen der Nerven?
Peripheral nerve conditions can be acquired or genetically mediated. Examples of genetic conditions include the hereditary sensory and motor neuropathies. Acquired peripheral neuropathies can stem from conditions such as diabetes, toxins, inflammatory disorders, or metabolic disturbances.
Beschreiben Sie drei Haupttypen von Nervenverletzungen.
- Neuropraxia is the functional loss of conduction without anatomic change of the axon, usually due to focal demyelination.
- In axonotmesis, the axonal continuity is lost.
- Neurotmesis results from separation of the entire nerve, including its supporting connective tissue.
Was ist das Innervationsverhältnis?
For each motor axon, there are a variable number of associated muscle fibers. The innervation ratio of the extraocular muscles is typically 1:3, whereas the gastrocnemius can be as high as 1:2000.
Was sind häufige Erkrankungen der Muskeln?
Muscle disease can be acquired or genetically mediated. Acquired muscle diseases such as inflammatory myopathies are most often proximal and symmetrical in distribution.
Beschreiben Sie die Komponenten einer Nadel-EMG-Untersuchung.
Insertional/spontaneous activity: An EMG needle inserted into a normal muscle should evoke brief electrical discharges of muscle fibers.
Motor unit analysis: Parameters include amplitude, duration, number of phases, and firing pattern of the MUAPs.
Recruitment: Reflects the underlying health of the motor units.
Wie unterscheiden sich Faszikulationen, Fibrillationen und positive sharp waves in der Nadel-EMG?
A fasciculation potential is an involuntary firing of an entire motor unit. A fibrillation potential is an involuntary contraction of a single muscle fiber. Positive sharp wave potentials are similar to fibrillation potentials but with an initial positive deflection.
Tabelle 10.1: EMG-Befunde für normale und denervierte Muskeln
ELECTROMYOGRAPHY FINDINGS | NORMAL | ACUTE DENERVATION | CHRONIC DENERVATION/REINNERVATION |
|—————————–|———–|———————-|———————————–|
| Spontaneous activity | None | Fibrillations, positive sharp waves | None |
| Motor unit action potential morphology | Normal | Normal | Large amplitude, long duration, polyphasia |
| Recruitment | Normal | Reduced | Reduced |
Tabelle 10.2: EMG-Befunde für normale Muskeln und myopathische Erkrankungen
ELECTROMYOGRAPHY FINDINGS | NORMAL MUSCLE | MYOPATHY |
|—————————–|——————|————-|
| Spontaneous activity | None | Variable fibrillations, positive sharp waves |
| Motor unit action potential morphology | Normal | Small amplitude, short duration, polyphasia |
| Recruitment | Normal | Early |
Warum wird die Temperatur während einer elektrodiagnostischen Untersuchung aufgezeichnet?
Nerve conduction velocities drop by 1.5 to 2.5 m/s per °C reduction. Failure to warm the limb can result in false-positive studies.
Was ist die F-Welle?
The F-wave is a delayed motor potential recorded by stimulating a motor nerve in the distal extremity. Abnormal F-waves can indicate proximal nerve disease.
Wie wird der sensorische Teil des peripheren Nervensystems getestet?
Sensory NCS are the primary means to test the integrity of the sensory nerves. The amplitude of SNAP, its point of onset, and its peak can be compared with standardized values.
Tabelle 10.3: Nervenabnormalitäten und mögliche Differentialdiagnosen
PERIPHERAL NERVE SYNDROME | DIFFERENTIAL DIAGNOSIS |
|—————————–|————————–|
| Carpal tunnel syndrome | C6 to C7 radiculopathy |
| Ulnar entrapment at the elbow | C8 radiculopathy |
| Radial nerve palsy | C7 radiculopathy |
