Carpal Tunnel Syndrome
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Understanding Pain and Numbness in the Hand:
Carpal Tunnel Syndrome: Pain, tingling, and numbness in the hand are often linked to carpal tunnel syndrome, a condition caused by pressure on the median nerve within the wrist. This can affect grip strength and daily activities, making early recognition and management crucial. Study the educational content and videos then scroll to bottom and click the button to be taken to the test. Upon Successful Completion (1.0 CEU) Certificate Awarded) |
Carpal Tunnel Syndrome:
Carpal Tunnel Syndrome (CTS) is a widespread and often debilitating condition that affects the hand and wrist. It arises due to the compression of the median nerve as it travels through the carpal tunnel, a narrow passageway located in the wrist. This syndrome is one of the most common nerve entrapment disorders, impacting individuals across various occupations and lifestyles. Understanding its causes, symptoms, diagnosis, treatment, and prevention is essential for effective management and improving quality of life.
Electrodiagnostic (EDX) studies play a crucial role in pinpointing median nerve abnormalities at the wrist, assessing their severity, and ruling out other conditions that may resemble carpal tunnel syndrome (CTS). However, both clinical and electrodiagnostic (EDX) evaluations are prone to challenges that may result in diagnostic errors. Achieving accurate results requires thorough clinical assessment and meticulous attention to technical factors and EDX methodologies. This review focuses on the diagnostic approaches for CTS, highlighting frequent pitfalls encountered in clinical practice and EDX procedures.
Anatomy and Function of the Carpal Tunnel
The carpal tunnel is a rigid, fibro-osseous passageway located at the base of the palm, serving as a conduit for the median nerve and nine flexor tendons that control finger and thumb movement. This narrow structure is formed by the carpal bones, which create the floor and lateral walls, and the transverse carpal ligament (TCL), a strong fibrous band of connective tissue that forms the roof. Due to the inflexible nature of these structures, the carpal tunnel has minimal capacity to expand or accommodate increased pressure.
The tunnel measures approximately 2.5 cm (about 1 inch) in width and varies in depth. It extends from the distal row of carpal bones to the proximal aspect of the palm, where it provides passage for crucial neurovascular and musculoskeletal components.
Median Nerve: Structure and Function
The median nerve is a vital component of the peripheral nervous system and plays a central role in both sensory and motor functions of the hand. It originates from the brachial plexus, specifically from nerve roots C5-T1, which merge to form a single nerve traveling along the arm. The median nerve descends the upper arm without innervating structures until it crosses the cubital fossa at the elbow. From there, it enters the anterior forearm, giving rise to the anterior interosseous nerve, which supplies deep flexor muscles.
Upon reaching the wrist, the median nerve traverses the carpal tunnel, where it is particularly susceptible to compression due to the confined anatomical space. Within the hand, the nerve branches into sensory and motor components:
The motor branch of the median nerve
(recurrent branch) is particularly significant, as it enables precise grip strength and dexterity. Injury or compression of this nerve can lead to functional impairments, including weakened grip, atrophy of the thenar eminence, and loss of fine motor coordination.
Flexor Tendons and Their Role in Hand Movement
Alongside the median nerve, the carpal tunnel accommodates nine flexor tendons, which facilitate finger and thumb movements. These tendons are enclosed in synovial sheaths that reduce friction and allow smooth gliding during flexion and extension. The tendons include:
These tendons are crucial for grasping, pinching, and overall dexterity. Due to their close proximity within the confined tunnel, inflammation, swelling, or synovial thickening can contribute to increased pressure, potentially compressing the median nerve.
Pathophysiology of Carpal Tunnel Syndrome
(CTS) Carpal Tunnel Syndrome is the most common compressive neuropathy of the upper limb, resulting from chronic pressure on the median nerve within the carpal tunnel. This compression can stem from increased intracarpal pressure, typically due to inflammation, fluid retention, repetitive strain, trauma, or systemic conditions such as:
The increased intracompartmental pressure leads to ischemia of the median nerve, resulting in sensory deficits, motor impairment, and, in chronic cases, nerve degeneration.
Clinical Symptoms Include:
Diagnosis and Management Diagnostic Evaluation:
Treatment Options:
Technical/Clinical testing information regarding Electrophysiological Studies – Nerve conduction studies (NCS)
Measuring the speed of electrical signals through the median nerve to detect delays caused by compression.
Nerve conduction studies (NCS) are highly reliable, with high sensitivity. These studies are valuable for confirming the clinical diagnosis, evaluating severity, and identifying or excluding coexisting conditions.
To ensure accurate results, performing NCS requires strict adherence to proper techniques and careful management of potential pitfalls during the procedure. Common errors, such as incorrect electrode placement, inaccurate distance measurements, improper stimulation sites, misaligned cathode-anode orientation, inappropriate stimulus intensity, or incorrect filter settings, must be identified and resolved during the test. These errors are often undetectable during the interpretation of the data, making real-time vigilance critical. Additionally, because many CTS cases are detected by comparing relative differences in nerve latencies, close attention to both physiological and technical factors is essential for the validity of the results.
False-negative results, where mild CTS cases are missed, are less detrimental than false-positive diagnoses, where normal individuals are incorrectly labeled with CTS. A false-positive diagnosis can lead to unnecessary treatments or interventions. To minimize this risk, it is recommended to confirm CTS with at least two comparative tests showing relatively prolonged median nerve latencies.
Median nerve slowing at the wrist, however, can sometimes be an incidental finding in asymptomatic individuals, such as workers performing repetitive tasks, diabetics, or those with demyelinating neuropathies. When this is observed, the findings should be reported as "median neuropathy at the wrist" rather than "CTS" unless the clinical presentation aligns with CTS. The correlation between clinical symptoms and NCS findings is crucial to determine whether the observed nerve abnormality is consistent with CTS or represents an incidental or unrelated condition. This approach also ensures the identification of any overlapping or additional conditions that may influence the patient’s presentation.
Electrophysiologic Assessment of Carpal Tunnel Syndrome (CTS): A Clinical Perspective
Carpal Tunnel Syndrome (CTS) is a prevalent neuropathic disorder resulting from median nerve compression at the wrist. Electrophysiologic testing is crucial for confirming the diagnosis, determining severity, and ruling out alternative neuropathic conditions. A structured approach involving nerve conduction studies (NCS) and electromyography (EMG) helps distinguish CTS from other conditions like brachial plexopathy, cervical radiculopathy, and polyneuropathy.
Goals of Electrophysiologic Testing
Nerve Conduction Studies (NCS)
CTS primarily involves focal demyelination, with possible secondary axonal loss in severe cases. The hallmark electrophysiologic feature of CTS is conduction delay across the carpal tunnel.
Standard NCS for CTS Evaluation:
Diagnostic Indicators: CTS is suggested when:
Advanced NCS Techniques for CTS Diagnosis
Electromyography (EMG) and Differential Considerations EMG plays a role in:
Management ApproachesNon-Surgical Treatment Early intervention can alleviate symptoms and slow disease progression.
Surgical Intervention Surgery is considered when:
Carpal Tunnel Release (CTR): This procedure involves cutting the transverse carpal ligament to relieve pressure on the median nerve, performed via:
Recovery and Prognosis
Complications and Long-Term Outlook
Conclusion The carpal tunnel is a crucial anatomical passageway that facilitates the function of the median nerve and flexor tendons, essential for hand movement and sensory perception. Given its rigid boundaries, any condition that alters its internal dynamics can compromise median nerve function, leading to carpal tunnel syndrome. Early recognition and appropriate intervention are critical for preventing long-term deficits and preserving hand function. Electrophysiologic testing remains the gold standard for CTS diagnosis, aiding in differentiation from other neuropathies. Early detection and appropriate treatment, whether conservative or surgical, are critical in preventing long-term disability and optimizing patient outcomes.
Technical Aspects for Neurodiagnostic Clinicians in performing Nerve Conduction Studies for Carpal Tunnel.
Prepare room/equipment
Origin: C6-C7 roots, upper and middle trunk and lateral cord of the brachial plexus, median nerve.
Carpal Tunnel Syndrome (CTS) is a widespread and often debilitating condition that affects the hand and wrist. It arises due to the compression of the median nerve as it travels through the carpal tunnel, a narrow passageway located in the wrist. This syndrome is one of the most common nerve entrapment disorders, impacting individuals across various occupations and lifestyles. Understanding its causes, symptoms, diagnosis, treatment, and prevention is essential for effective management and improving quality of life.
Electrodiagnostic (EDX) studies play a crucial role in pinpointing median nerve abnormalities at the wrist, assessing their severity, and ruling out other conditions that may resemble carpal tunnel syndrome (CTS). However, both clinical and electrodiagnostic (EDX) evaluations are prone to challenges that may result in diagnostic errors. Achieving accurate results requires thorough clinical assessment and meticulous attention to technical factors and EDX methodologies. This review focuses on the diagnostic approaches for CTS, highlighting frequent pitfalls encountered in clinical practice and EDX procedures.
Anatomy and Function of the Carpal Tunnel
The carpal tunnel is a rigid, fibro-osseous passageway located at the base of the palm, serving as a conduit for the median nerve and nine flexor tendons that control finger and thumb movement. This narrow structure is formed by the carpal bones, which create the floor and lateral walls, and the transverse carpal ligament (TCL), a strong fibrous band of connective tissue that forms the roof. Due to the inflexible nature of these structures, the carpal tunnel has minimal capacity to expand or accommodate increased pressure.
The tunnel measures approximately 2.5 cm (about 1 inch) in width and varies in depth. It extends from the distal row of carpal bones to the proximal aspect of the palm, where it provides passage for crucial neurovascular and musculoskeletal components.
Median Nerve: Structure and Function
The median nerve is a vital component of the peripheral nervous system and plays a central role in both sensory and motor functions of the hand. It originates from the brachial plexus, specifically from nerve roots C5-T1, which merge to form a single nerve traveling along the arm. The median nerve descends the upper arm without innervating structures until it crosses the cubital fossa at the elbow. From there, it enters the anterior forearm, giving rise to the anterior interosseous nerve, which supplies deep flexor muscles.
Upon reaching the wrist, the median nerve traverses the carpal tunnel, where it is particularly susceptible to compression due to the confined anatomical space. Within the hand, the nerve branches into sensory and motor components:
- Sensory Function: Provides sensation to the palmar aspect of the thumb, index finger, middle finger, and the radial half of the ring finger. It also supplies the corresponding nail beds and distal dorsal surfaces of these fingers.
- Motor Function: Controls the thenar muscles (abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis), which facilitate thumb opposition, abduction, and flexion. It also innervates the lateral two lumbricals, contributing to fine motor control of the index and middle fingers.
The motor branch of the median nerve
(recurrent branch) is particularly significant, as it enables precise grip strength and dexterity. Injury or compression of this nerve can lead to functional impairments, including weakened grip, atrophy of the thenar eminence, and loss of fine motor coordination.
Flexor Tendons and Their Role in Hand Movement
Alongside the median nerve, the carpal tunnel accommodates nine flexor tendons, which facilitate finger and thumb movements. These tendons are enclosed in synovial sheaths that reduce friction and allow smooth gliding during flexion and extension. The tendons include:
- Four flexor digitorum superficialis (FDS) tendons – responsible for flexion of the middle phalanges of the fingers.
- Four flexor digitorum profundus (FDP) tendons – responsible for flexion of the distal phalanges of the fingers.
- One flexor pollicis longus (FPL) tendon – responsible for thumb flexion.
These tendons are crucial for grasping, pinching, and overall dexterity. Due to their close proximity within the confined tunnel, inflammation, swelling, or synovial thickening can contribute to increased pressure, potentially compressing the median nerve.
Pathophysiology of Carpal Tunnel Syndrome
(CTS) Carpal Tunnel Syndrome is the most common compressive neuropathy of the upper limb, resulting from chronic pressure on the median nerve within the carpal tunnel. This compression can stem from increased intracarpal pressure, typically due to inflammation, fluid retention, repetitive strain, trauma, or systemic conditions such as:
- Rheumatoid arthritis and inflammatory arthritis – Synovial proliferation leads to increased tendon sheath swelling.
- Diabetes mellitus – Causes nerve ischemia and contributes to neuropathy.
- Hypothyroidism – Results in mucopolysaccharide deposition in the perineural tissues.
- Pregnancy – Leads to fluid retention and increased pressure within the tunnel.
- Repetitive hand movements – Occupational and lifestyle factors (e.g., typing, assembly line work, prolonged wrist flexion) can contribute to microtrauma and inflammation.
The increased intracompartmental pressure leads to ischemia of the median nerve, resulting in sensory deficits, motor impairment, and, in chronic cases, nerve degeneration.
Clinical Symptoms Include:
- Numbness, tingling, or burning pain in the median nerve distribution.
- Nocturnal symptoms, often worsening at night due to fluid redistribution.
- Weakness in thumb opposition and grip strength (e.g., difficulty holding small objects).
- Thenar muscle atrophy in advanced cases.
- Positive Phalen’s test and Tinel’s sign (clinical diagnostic maneuvers).
Diagnosis and Management Diagnostic Evaluation:
- Clinical Examination – Including Phalen’s test, Tinel’s sign, and Durkan’s compression test.
- Electrophysiological Studies – Nerve conduction studies (NCS) and electromyography (EMG) to assess median nerve function and detect abnormalities.
- Ultrasound and MRI – Used to visualize nerve swelling, tendon thickening, or space-occupying lesions.
Treatment Options:
- Conservative Management:
- Activity modification (avoiding repetitive wrist movements).
- Wrist splinting (neutral position, particularly at night).
- NSAIDs and corticosteroid injections for inflammation control.
- Physical Therapy:
- Nerve gliding exercises to improve mobility.
- Ergonomic adjustments in workplace settings.
- Surgical Intervention:
- Carpal tunnel release (CTR) surgery in refractory cases. This involves transecting the transverse carpal ligament to relieve pressure on the median nerve.
Technical/Clinical testing information regarding Electrophysiological Studies – Nerve conduction studies (NCS)
Measuring the speed of electrical signals through the median nerve to detect delays caused by compression.
Nerve conduction studies (NCS) are highly reliable, with high sensitivity. These studies are valuable for confirming the clinical diagnosis, evaluating severity, and identifying or excluding coexisting conditions.
To ensure accurate results, performing NCS requires strict adherence to proper techniques and careful management of potential pitfalls during the procedure. Common errors, such as incorrect electrode placement, inaccurate distance measurements, improper stimulation sites, misaligned cathode-anode orientation, inappropriate stimulus intensity, or incorrect filter settings, must be identified and resolved during the test. These errors are often undetectable during the interpretation of the data, making real-time vigilance critical. Additionally, because many CTS cases are detected by comparing relative differences in nerve latencies, close attention to both physiological and technical factors is essential for the validity of the results.
False-negative results, where mild CTS cases are missed, are less detrimental than false-positive diagnoses, where normal individuals are incorrectly labeled with CTS. A false-positive diagnosis can lead to unnecessary treatments or interventions. To minimize this risk, it is recommended to confirm CTS with at least two comparative tests showing relatively prolonged median nerve latencies.
Median nerve slowing at the wrist, however, can sometimes be an incidental finding in asymptomatic individuals, such as workers performing repetitive tasks, diabetics, or those with demyelinating neuropathies. When this is observed, the findings should be reported as "median neuropathy at the wrist" rather than "CTS" unless the clinical presentation aligns with CTS. The correlation between clinical symptoms and NCS findings is crucial to determine whether the observed nerve abnormality is consistent with CTS or represents an incidental or unrelated condition. This approach also ensures the identification of any overlapping or additional conditions that may influence the patient’s presentation.
Electrophysiologic Assessment of Carpal Tunnel Syndrome (CTS): A Clinical Perspective
Carpal Tunnel Syndrome (CTS) is a prevalent neuropathic disorder resulting from median nerve compression at the wrist. Electrophysiologic testing is crucial for confirming the diagnosis, determining severity, and ruling out alternative neuropathic conditions. A structured approach involving nerve conduction studies (NCS) and electromyography (EMG) helps distinguish CTS from other conditions like brachial plexopathy, cervical radiculopathy, and polyneuropathy.
Goals of Electrophysiologic Testing
- Identify focal slowing or conduction block of median nerve fibers at the carpal tunnel.
- Rule out median neuropathy at the elbow.
- Exclude brachial plexopathy affecting median nerve fibers.
- Differentiate from cervical radiculopathy, particularly at C6 and C7.
- Assess whether median nerve slowing at the wrist exceeds the expected changes in cases of concurrent polyneuropathy.
Nerve Conduction Studies (NCS)
CTS primarily involves focal demyelination, with possible secondary axonal loss in severe cases. The hallmark electrophysiologic feature of CTS is conduction delay across the carpal tunnel.
Standard NCS for CTS Evaluation:
- Median sensory response – Recording from digit 2 or 3, with stimulation at the wrist. (#1 image below)
- Ulnar sensory response – Recording from digit 5, with stimulation at the wrist. (#2 image below)
- Median motor study – Recording from abductor pollicis brevis (APB), stimulating at wrist & antecubital fossa. (#3 image below)
- Ulnar motor study – Recording from abductor digiti minimi (ADM), with stimulation at wrist & different levels around the elbow. (#4 image below)
- Median and ulnar F-wave studies – Assessing proximal conduction.
- Radial sensory response – Recording from the anatomical snuffbox, with stimulation over the lateral radius.
Diagnostic Indicators: CTS is suggested when:
- The median nerve exhibits significant conduction delay at the wrist, evidenced by prolonged distal motor and sensory latencies.
- F-wave latencies are increased.
- Reduced median compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) amplitudes suggest axonal loss or conduction block.
- Normal ulnar and radial sensory responses help rule out brachial plexopathy or generalized polyneuropathy.
Advanced NCS Techniques for CTS Diagnosis
- Median-to-Ulnar Comparative Studies:
- Palm-to-wrist latency comparisons.
- Lumbrical-interossei distal motor latency comparison.
- Sensory latency comparison at digit 4 between median and ulnar nerves.
- Median-to-Radial Comparative Studies:
- Sensory latency comparison at digit 1.
- Segmental Median Sensory Study:
- Measuring wrist-to-palm conduction velocity to detect segmental slowing.
Electromyography (EMG) and Differential Considerations EMG plays a role in:
- Evaluating axonal loss by detecting denervation in the abductor pollicis brevis.
- Differentiating CTS from conditions such as cervical radiculopathy, brachial plexopathy, or motor neuron disease.
Management ApproachesNon-Surgical Treatment Early intervention can alleviate symptoms and slow disease progression.
- Bracing or Splinting:
- Nighttime wrist immobilization in a neutral position minimizes nerve compression.
- NSAIDs:
- Anti-inflammatory medications like ibuprofen may provide symptom relief.
- Activity Modification:
- Ergonomic adjustments can help minimize repetitive wrist strain.
- Nerve Gliding Exercises:
- Enhancing nerve mobility can reduce symptoms.
- Corticosteroid Injections:
- Offers temporary relief from inflammation.
- Platelet-Rich Plasma (PRP) Injections:
- Potential benefits have been noted, but long-term efficacy is still debated.
Surgical Intervention Surgery is considered when:
- Symptoms persist despite conservative management.
- There is significant motor or sensory impairment.
- EMG indicates severe axonal degeneration.
Carpal Tunnel Release (CTR): This procedure involves cutting the transverse carpal ligament to relieve pressure on the median nerve, performed via:
- Open release surgery – A traditional technique involving a small incision.
- Endoscopic release surgery – A minimally invasive method promoting quicker recovery.
Recovery and Prognosis
- Pain and Swelling:
- Managed through NSAIDs and hand elevation.
- Grip and Pinch Strength:
- Typically restored within 2–3 months, though delayed recovery may indicate pre-existing nerve damage.
- Sensory Improvement:
- Gradual improvement occurs over months, potentially taking up to a year in severe cases.
Complications and Long-Term Outlook
- Potential Complications:
- Infection, bleeding, scar sensitivity, or incomplete decompression.
- Long-Term Recovery:
- Most patients experience significant symptom relief, but severe nerve damage may limit full recovery.
- Recurrence:
- Rare but possible, occasionally requiring additional treatment.
Conclusion The carpal tunnel is a crucial anatomical passageway that facilitates the function of the median nerve and flexor tendons, essential for hand movement and sensory perception. Given its rigid boundaries, any condition that alters its internal dynamics can compromise median nerve function, leading to carpal tunnel syndrome. Early recognition and appropriate intervention are critical for preventing long-term deficits and preserving hand function. Electrophysiologic testing remains the gold standard for CTS diagnosis, aiding in differentiation from other neuropathies. Early detection and appropriate treatment, whether conservative or surgical, are critical in preventing long-term disability and optimizing patient outcomes.
Technical Aspects for Neurodiagnostic Clinicians in performing Nerve Conduction Studies for Carpal Tunnel.
Prepare room/equipment
- Room Ready.
- Patient information and history obtained.
- Review Clinical order and patients symptoms and determine where to start.
- Choose test. Some labs start with Sensory and some start with Motor refer to your labs protocols.
- Position patient per the specific test protocol. (See Below)
- Ensure extremity is at right temp (Above 31c lower extremities and 32c upper).
- Ensure tested area is clean.
- Place electrodes at appropriate locations as per test protocol. (Below)
- Ensure artifact is at a minimum.
- Start with low intensity and go up (assure supra-max) waveform.
- Ensure clear and clean waveforms are obtained.
- Ensure all waveforms are marked correctly and complete test.
- Ensure proper temperature.
- Ensure proper measurements.
- Ensure proper electrode placement.
- Ensure stimulating cathode to active.
- Ensure max-stimulation is adequate for full potential; be aware of volume conduction.
- Ensure artifacts are lessened by cleaning the skin, good electrodes, repositioning the patient or moving the wires or unplugging unnecessary equipment. Also, watch for Gel-shorts or bridging.
- Ensure proper placement of waveform-cursors/markers for clear and concise reporting.
Origin: C6-C7 roots, upper and middle trunk and lateral cord of the brachial plexus, median nerve.
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Image 1
Median Nerve Sensory Study (Antidromic) Position: Patient supine arm out (Palm Up) Temp check: Above 32c Measurement: (S1) 11-14cm Wrist – 2nd Digit. Stimulating: Median Nerve at wrist (S1) 11-14cm proximal active recorder Recording: Active on index finger with reference distal. Ground Electrode: Located on dorsum of hand or palm. Machine Settings: Sensory Nerve (Median) Sensitivity -20 uV/division, LLF 20Hz HFF 2kHz, Sweep speed-1 msec/division Normal Amplitude >20 uV Normal Conduction Velocity >50 m/s Normal Distal Peak Latency <3.5 ms |
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Image 2
Ulnar Nerve Sensory Study (Antidromic) Position: Patient supine arm out (Palm Up) Temp check: Above 32c Measurement: (S1) 11-14cm Wrist – 5th Digit. Stimulating: Ulnar Nerve at wrist (S1) 11-14cm proximal active recorder Ground Electrode: Located on dorsum of hand or palm. Stimulating: Ulnar nerve groove between ulna bone and flexor carpi ulnaris. (14cm proximal active) Recording: Active on fifth digit with reference distal. Machine Settings: Sensory Nerve (Median) Sensitivity -20 uV/division, LLF 20Hz HFF 2kHz, Sweep speed-1 msec/division. Normal Amplitude >17 uV Normal Conduction Velocity >50 m/s Normal Distal Peak Latency <3.1 ms |
Image 3
Median Nerve Motor Study (Antidromic)
Position: Patient supine arm out (Palm Up)
Temp check: Above 32c
Measurement: 8cm Wrist - APB
Stimulating: (S1) Over median nerve 8cm proximal active electrode. Measure from APB to mid-wrist-crease then proximal with cathode distal anode.
Stimulating: (S2) Cathode is placed medial to the brachial artery in the antecubital region with anode proximal.
Recording: Active on the belly of Abductor Pollicis Brevis (APB) with reference distal the first metacarpophalangeal joint.
Ground Electrode: Located on dorsum of hand.
Machine Settings: Motor Nerve (Median) Sensitivity -5 mV/division, LLF 2-3Hz
HFF 10kHz, Sweep speed-2 msec/division.
Normal Amplitude >4.0 mV
Normal Conduction Velocity >49 m/s
Normal Distal Latency <4.4 ms
Median Nerve Motor Study (Antidromic)
Position: Patient supine arm out (Palm Up)
Temp check: Above 32c
Measurement: 8cm Wrist - APB
Stimulating: (S1) Over median nerve 8cm proximal active electrode. Measure from APB to mid-wrist-crease then proximal with cathode distal anode.
Stimulating: (S2) Cathode is placed medial to the brachial artery in the antecubital region with anode proximal.
Recording: Active on the belly of Abductor Pollicis Brevis (APB) with reference distal the first metacarpophalangeal joint.
Ground Electrode: Located on dorsum of hand.
Machine Settings: Motor Nerve (Median) Sensitivity -5 mV/division, LLF 2-3Hz
HFF 10kHz, Sweep speed-2 msec/division.
Normal Amplitude >4.0 mV
Normal Conduction Velocity >49 m/s
Normal Distal Latency <4.4 ms
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Image 4
Ulnar Nerve Motor Study (Antidromic) Position: Patient laying supine with arm out at 45 degrees with palm facing up. The elbow should be at 90 degrees. Temp check: Above 32c Measurement: 8cm Wrist – ADM and at elbow (10cm below to above elbow). Stimulating: (S1) Wrist, Cathode placement is 8cm proximal the active recorder at ADM. Stimulating: (S2) Below elbow, Cathode placement is 3cm distal medial epicondyle with anode proximal. Stimulating: (S3) Above elbow, Cathode placement is 7cm proximal medial epicondyle or 10cm proximal (S2) Recording: Active placed on the belly of Abductor Digiti Minimi (ADM) with reference distal 5th metacarpophalangeal joint. Ground Electrode: Located on dorsum of hand or near active points if artifact presents. Machine Settings: Motor Nerve (Ulnar) Sensitivity -5 mV/division, LLF 2-3Hz HFF 10kHz, Sweep speed-2 msec/division. Normal Amplitude >6.0 mV Normal Conduction Velocity >49 m/s Normal Distal Latency <3.3 ms |
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Median/Ulnar Nerve Palmer Sensory Study Position: Patient supine arm out (Palm Up) Temp check: Above 32c Measurement: 8cm Wrist - Median Palm and 8cm Wrist - Ulnar Palm Stimulating: Median Palm 8cm distal the active recording & Ulnar Palm (Web space between 4th & 5th digits) 8cm distal the active located at wrist. Recording: Active at wrist over median nerve proximal to crease with reference proximal 3cm. For the Ulnar - Active at wrist over ulnar nerve proximal to crease with reference proximal 3cm. Ground Electrode: Located on dorsum of hand or palm Machine Settings: Sensory Nerve (Median) Sensitivity -10 uV/division, LLF 20Hz HFF 2kHz, Sweep speed-1 msec/division. Normal difference between Median & Ulnar Palmer Latency is >0.4 ms |
Median/Ulnar Digit 4 Sensory Study (Antidromic)
Position: Patient supine arm out (Palm Up)
Temp check: Above 32c
Measurement: 12cm Wrist – 4th Digit (For both Median & Ulnar)
Stimulating: (S1) Median Nerve at wrist / (S2) Ulnar Nerve at Wrist
Recording: Active on ring finger (digit 4) with reference distally 3-4cm.
Ground Electrode: Located on dorsum of hand or palm.
Machine Settings: Sensory Nerve (Median/Ulnar) Sensitivity -20 uV/division, LLF 20Hz
HFF 2kHz, Sweep speed-1 msec/division.
Normal difference between Median & Ulnar Latency is >0.5 ms
Position: Patient supine arm out (Palm Up)
Temp check: Above 32c
Measurement: 12cm Wrist – 4th Digit (For both Median & Ulnar)
Stimulating: (S1) Median Nerve at wrist / (S2) Ulnar Nerve at Wrist
Recording: Active on ring finger (digit 4) with reference distally 3-4cm.
Ground Electrode: Located on dorsum of hand or palm.
Machine Settings: Sensory Nerve (Median/Ulnar) Sensitivity -20 uV/division, LLF 20Hz
HFF 2kHz, Sweep speed-1 msec/division.
Normal difference between Median & Ulnar Latency is >0.5 ms
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Median/Radial Digit 1 (Thumb) Sensory Study (Antidromic)
Position: Patient supine arm out (Palm Up) Temp check: Above 32c Measurement: 10cm Wrist – Digit 1 (For both Median & Radial) Stimulating: (S1) Radial Nerve at wrist / (S2) Median Nerve at Wrist Recording: Active on Thumb (digit 1) with reference distally 3-4cm. Ground Electrode: Located on dorsum of hand or palm. Machine Settings: Sensory Nerve (Median/Ulnar) Sensitivity -20 uV/division, LLF 20Hz HFF 2kHz, Sweep speed-1 msec/division. Normal difference between Median & Radial Latency is >0.4 ms |
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Median / Ulnar Lumbrical-Interossei Study (Antidromic)
Position: Patient supine arm out (Palm Up) Temp check: Above 32c Measurement: 10cm Median & Radial Wrist - Interossei Muscle Stimulating: (S1) Wrist over median nerve 10cm proximal to the active recording electrode. (S2) Wrist over ulnar nerve 10cm proximal to the active recording electrode. Recording: (R1) First palmer interosseous just lateral third metacarpal. (R2) placed distally over the metacarpophalangeal joint. Ground Electrode: Located on dorsum of hand. Machine Settings: Sensitivity -5 mV/division, LLF 2-3Hz HFF 10kHz, Sweep speed-2 msec/division. Normal difference between Median & Ulnar Latency is >0.5 ms |
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