Recomendados
Recomendados
Más contenido relacionado
La actualidad más candente
La actualidad más candente (20)
Similar a Intraoperative Electromyography (EMG)
Similar a Intraoperative Electromyography (EMG) (20)
Más de Anurag Tewari MD
Más de Anurag Tewari MD (19)
Último
Último (20)
Intraoperative Electromyography (EMG)
- 1. EMG ANURAG TEWARI MD Intraoperative Electromyography
- 3. Intraoperative Electromyography • 1666: Francesco Redi: Muscles of Electric Ray Fish generated electricity • • 1792: Luigi Galvani: “electricity ” could initiate muscle contraction Luigi Galvani 1773-1798 AnuragTewariMD
- 4. Intraoperative Electromyography • 1849: Emil du Bois-Reymond: possible to record electrical activity during voluntary muscle contraction • 1890: Étienne-Jules Marey: first actual recording, and introduced the term electromyography • 1922: Gasser & Erlanger: used ‘oscilloscope’ to show electrical signals from muscles Erlanger discovered that the velocity of action potentials was directly proportional to the diameter of the nerve fiber AnuragTewariMD
- 5. Intraoperative Electromyography Electro Myo Graphy Involving Electricity Relating to Muscle Technique of producing images ELECTRICAL STUDY OF MUSCLE FUNCTION Measurement of electrical signals within the skeletal muscle with two electrodes AnuragTewariMD
- 6. Intraoperative Electromyography • EMG is performed using an instrument called an ELECTROMYOGRAPH • To produce a record called an ELECTROMYOGRAM • The EMG signal is the electrical manifestation of the neuromuscular activation associated with a contracting muscle AnuragTewariMD
- 7. Intraoperative Electromyography EMG is the detection, amplification, recording, processing, analysis and interpretation of the electrical signal produced by the contraction of a muscle
- 8. Intraoperative Electromyography • Thus EMG is a BIOMEDICAL SIGNAL • Biomedical signal means a collective electrical signal acquired from any organ that represents a physical variable of interest • This signal is normally a function of time and is describable in terms of its AMPLITUDE, FREQUENCY, and PHASE • Amplitude: quantity which expresses the level of signal activity • Phase: the net excursion of the amplitude of a signal in either the positive or negative direction. AnuragTewariMD
- 9. Intraoperative Electromyography Skeletal Muscle Fiber AnuragTewariMD
- 10. EMG recording • The EMG is recorded by using a electrode placed on the muscle • The electrical activity measured by each muscle electrode and the ground electrode are sent to an amplifier • The amplifier eliminates random voltages caused by electrical noise by subtracting the signal from the ground electrode from the muscle electrode, producing the raw EMG AnuragTewariMD
- 11. EMG • An EMG is the summation of action potentials from the muscle fibers under the electrodes placed on the skin.
- 12. EMG • The more muscles that fire, the greater the amount of action potentials recorded and the greater the EMG reading AnuragTewariMD
- 13. Intraoperative Electromyography • EMG recordings provide essentially instantaneous feedback to the surgeon regarding the effects of his or her actions • EMG can be monitored in any muscle accessible to • Needle • Wire • Surface electrode AnuragTewariMD
- 14. Needle or wire electrodes inserted in the contracting muscle record individual Motor Unit Action Potential (MUAP) • Depending on the type of electrode used and its location, the recorded action potentials can be the result of the activity of a number of muscle fibers • Small (1–3) • Moderate (15–20) • Large (more than 20) AnuragTewariMD
- 15. Intraoperative Electromyography EMG records Compound Muscle Action Potential (CMAPs) in response to spontaneous or electrically stimulated activation of • Cranial Nerve • Spinal Nerve • Ventral Root CMAP is the synchronous activation of a group of motor neurons within a nerve bundle by brief electrical stimulation, producing a composite activity in the target muscles AnuragTewariMD
- 16. MOTOR UNIT The Nerve Muscle Functional Unit A motor unit is made up of a alpha motor neuron and the skeletal muscle fibers innervated by that motor neuron's axonal terminals A single axon may innervate a few or many individual muscle (5-5000) A single axon may innervate as few as three muscle fibers (as in eye muscles) or more than 500 (as in the gastrocnemius) AnuragTewariMD
- 17. MOTOR UNIT A Motor Unit is activated when stimulation of an individual axon sufficiently reaches the threshold for action potential firing AnuragTewariMD
- 18. Motor Unit Action Potential • After the motor unit is stimulated, its pulse is recorded by the electrode and displayed as an action potential, known as a Motor Unit Action Potential MUAP is a compound potential representing the sum of the individual action potentials generated in the few muscle fibers of the unit that are within the pick up range of the recording electrode AnuragTewariMD
- 19. Motor Unit Action Potential • MUAP is the basis of intraoperative EMG recording • Motor unit action potential (MUAP) varies based on muscle, age • Duration often shorter in proximal muscles • Amplitude greater in adults than children (bigger fibers) • MUAP size larger in older individuals (probably from dropout of motor units with some “normal” reinnervation) •
- 20. MUAP parameters Duration, Spike Duration, Turns, and Phases AnuragTewariMD
- 21. Factors that Effect MUAP • Technical Factors • Type of the needle electrode • Characteristics of recording surface • Electrical Characteristics of the cable • Preamplifier & Amplifier • Method of recording • Physiological Factors • Age of the patient • Muscle Examined • Temperature AnuragTewariMD
- 22. Muscles Commonly Used in EMG Monitoring AnuragTewariMD
- 23. Muscles Commonly Used in EMG Monitoring Each spinal root innervates many muscles (and this group of muscles is termed the myotome for that root) Conversely, most muscles are innervated by multiple spinal roots AnuragTewariMD
- 24. Cranial Nerve EMG CN III, IV, VI CN V CN VII CN IX CN X CN XI CN XII Masseter, Temporalis Extra Ocular Muscles Frontalis, Orbicularis Oculi, Orbicularis Oris, Mentalis, etc Stylopharyngeus Pharyngeal and laryngeal muscles Sternocleidomastoid, Trapezius Tongue AnuragTewariMD
- 25. Spinal Root Myotomes for Upper extremity EMG C1 C2 C3 C4 C5 C6 C7 Sternocleidomastoid None Trapezius, Sternocleidomastoid Trapezius, Levator Scapulae Deltoid, Biceps Biceps, Triceps, Brachioradialis, Flexor carpi radialis (FCR) Triceps, Flexor carpi radialis (FCR), Forearm extensors, Pronator Teres C7 Triceps, Ulnar Forearm ms, All Intrinsic Muscles (APB, ADM) AnuragTewariMD
- 26. Spinal Root Myotomes for Thoracic EMG T1 T2 –T6 T6-T8 T8-T10 T10-T12 Intercostal Muscles, Paraspinal Muscles Intrinsic Hand muscless, Flexor Carpi Ulnaris Upper Rectus Abdominis, Intercostal Muscles, Paraspinal Muscles Middle Rectus Abdominis, Intercostal Muscles, Paraspinal Muscles Lower Rectus Abdominis, Intercostal Muscles, Paraspinal Muscles AnuragTewariMD
- 27. AnuragTewariMD Spinal Root Myotomes for Lower extremity EMG L1 L2 L3 L4 L5 S1 S2 Iliopsoas, Adductor Longus, Quadriceps, Adductor Magnus Quadratus Lumborum, Paraspinal Cremaster ±Iliopsoas ± Internal Oblique Quadriceps, Adductor Longus, Iliopsoas, Adductor Magnus Quadriceps, Adductor Longus, Adductor Magnus, Iliopsoas, Tibialis, Anterior, Peroneous Longus, Adductor Magnus Gastrocnemius, Abductor Hallicus Gastrocnemius, Abductor Hallicus S2-S5 Anal Sphincter, Urethral Sphincter
- 29. C5, C6 = Biceps & Brachioradialis C7, C8 = Triceps S1, S2 = Ankle Jerk L3, L4 = Knee Jerk 1-2 Buckle my shoe 3-4 Kick the door 5-6 Pick up sticks 7-8 Shut the gate AnuragTewariMD
- 31. Intraoperative Electromyography EMG monitoring is most effective in cases where nerve injury results from REPETITIVE mechanical irritation of a nerve AnuragTewariMD
- 32. When surgical irritation of axons is sufficient Axonal depolarization results Activation of the muscle fibers innervated by those axons Depolarization of a single axon leads to single MUAP Recorded as a “SPIKE” on EMG AnuragTewariMD
- 33. Intraoperative Electromyography • Irritation triggers motor units in a variety of patterns that are influenced by • The pre-existing condition of the nerve • The degree and mechanism of neural irritation • The integrity of the neuromuscular function AnuragTewariMD
- 34. Analysis of EMG • QUALITATIVE ANALYSIS • Visual inspection of the record • QUANTITATIVE ANALYSIS • Amplitude, Duration, & Frequency • Power Spectrum Analysis AnuragTewariMD
- 35. Types of EMG • EMG can be recorded from either • Surface electrodes • Needles placed into the muscle • EMG is of two types • Spontaneous EMG • Triggered EMG AnuragTewariMD
- 36. Types of EMG • Spontaneous EMG (S-EMG) • Passive muscle recording for purpose of detecting cranial nerve or nerve root irritation • Triggered EMG (T-EMG) • Electrical stimulation of neural elements/hardware for purpose of assessing function AnuragTewariMD
- 37. Spontaneous EMG (S-EMG) • S-EMG is used as a means of monitoring cranial and spinal nerves during surgery • Proper selection of the muscles is key to success of S-EMG recording AnuragTewariMD
- 38. Spontaneous EMG (S-EMG) • Impending injury to cranial or spinal nerve by • Stretch • Compression • Mechanical Irritation • Leads to increase firing which is detectable as CMAPs in monitored muscle groups • ISCHEMIA usually does not induce action potential firing • Poorly detected by EMG AnuragTewariMD
- 39. Spontaneous EMG (S-EMG) • S-EMG differs from other IONM modalities • Normal state is lack of response • Due to absence of any muscle activity • Indicating a normal healthy nerve has not become activated as a result of surgical stimulation • If preexisting nerve root irritation is present, the baseline EMG recording will often contain low amplitude periodic firing AnuragTewariMD
- 40. Spontaneous EMG (S-EMG) • Clinical significance of EMG firing is considered proportional to • Frequency • Amplitude • Persistence AnuragTewariMD
- 41. Spontaneous EMG (S-EMG) • Waveform occurring at high frequency and increased amplitude indicate multiple motor units involvement • Warning of an impending injury • Co-relate with surgical event • Retractor placement • Hardware insertion Should revert to baseline with cessation of causative action If not it means injury to the has occurred AnuragTewariMD
- 42. Spontaneous EMG (S-EMG) • S-EMG SPIKES • Random activation of one or a few motor units during surgery • Not clinically significant AnuragTewariMD
- 43. Spontaneous EMG (S-EMG) • S-EMG BURSTS • Random activation of several motor units • Spikes and Bursts indicate proximity to neural elements and useful guide for surgical navigation AnuragTewariMD
- 44. Spontaneous EMG (S-EMG) • Spike and Bursts are distinguished by • Longer duration (milliseconds) • Polyphasic as opposed to biphasic AnuragTewariMD
- 45. Spontaneous EMG (S-EMG) • S-EMG TRAINS • Repetitive and prolonged/sustained firing on one or more motor units • Lasting from seconds to minutes • The duration of time a nerve is activated is dependent on the degree of nerve irritation • Significant nerve irritation or nerve damage can produce neurotonic discharges in which no individual muscle action potential is distinguishable • Report to the surgeon immediately AnuragTewariMD
- 46. AnuragTewariMD
- 47. Triggered EMG • T-EMG is used to • Identify a nerve or nerve root of interest • Assess the functional integrity of a nerve or nerve root • Assess the placement of pedicle screws AnuragTewariMD
- 48. Triggered EMG • Identification of nerves or nerve roots • A healthy neural tissue should stimulate at an intensity of less than 2mA and produce a recordable CMAP • T-EMG is best accomplished by handheld bipolar probe AnuragTewariMD
- 49. Triggered EMG • A bipolar probe will reduce the size of current field and increase the specificity of stimulation • Square wave pulses • Pulse width of 50-100μs • Delivered @ approximately 2 pulses/ second • The latency is dependent on the distance between the stimulation and recording site AnuragTewariMD
- 50. Triggered EMG • Assessing the functional integrity of a nerve or nerve root • Direct electrical stimulation is also used to access the health and function of a nerve root • Healthy nerves have a stimulation threshold well under 2mA and often under 1mA AnuragTewariMD
- 51. Pedicle Screw Triggered EMG • Spinal instrumentation must be anchored to the vertebral column in order to provide support and allow bony fusion • Screws are often placed in the pedicle to provide anchor • If mal-positioned, they impinge on exiting nerve roots, causing RADICULOPATHY AnuragTewariMD
- 52. Pedicle Screw Triggered EMG If the hole drilled in the pedicle, perforates the wall A low-impedance pathway is created between stimulation, within the hole, and nearby exiting nerve roots A relatively low level of electrical stimulation activates these nerve roots Resultant activity recorded from their corresponding muscles Thus the integrity of the pedicle can be assessed based on the minimum level of electrical current needed to activate nearby nerve roots AnuragTewariMD
- 54. Pedicle Screw Triggered EMG • Stimulating Pedicle Screws Pedicle holes and screws should be electrically tested to assess for perforation of the pedicle wall AnuragTewariMD
- 55. Threshold Values for Pedicle Screw Triggered EMG • Stimulating Pedicle Screws • Threshold Values Indicating the Likelihood of Pedicle Screw Mal-positioning Perforation Probable Perforation Possible Perforation Unlikely Hole <5mA 5-7mA >7mA Screw <7mA 7-10mA >10mA AnuragTewariMD
- 56. EMG “burst” • A brief period of polyphasic EMG activity representing the near simultaneous activation of multiple axons (motor units) AnuragTewariMD
- 57. EMG “train” • Repetitive firing of one or more motor units lasting from a second to minutes AnuragTewariMD
- 58. A minor burst of activity occurring as a lumbar root is manipulated AnuragTewariMD
- 59. A more intense burst occurring on the background of an ongoing train of activity AnuragTewariMD
- 60. Intense ongoing trains of activity from multiple motor units (ASYNCHRONOUS ACTIVITY) AnuragTewariMD
- 61. Residual train of activity as the effect of nerve root irritation wanes AnuragTewariMD
- 62. An interference pattern in the left gastrocnemius muscle after inadvertent trauma to the corresponding nerve root AnuragTewariMD
- 63. AnuragTewariMD
- 64. Neuropathic vs. Myopathic EMG Neuropathic Disease Myopathic Disease Decreased Action Potential Duration Decreased Motor Unit number in the muscles Reduced Area to Amplitude ratio of the action potential Increased Action Potential Duration Decreased Motor Unit number in the muscles Twice as normal action potential AMPLITUDE AnuragTewariMD
- 65. AnuragTewariMD
- 66. AnuragTewariMD