2023 Workshop Handout Bundle-Unusual NCS

Unusual NCS
Pdf Summary
The document provides an in-depth overview of various sensory nerve conduction studies and techniques, focusing on their application, measurement, and diagnostic value. Originating from a workshop presented at the 2023 AANEM Annual Meeting by Dr. Lawrence Robinson, Doug M. Ma, MD, Asa J. Wilbourn, MD, and George H. Kraft, MD, the content emphasizes the critical role of sensory conduction studies in the evaluation of peripheral nerve lesions.<br /><br />**Key Points:**<br /><br />1. **Introduction to Sensory Nerve Conduction Studies (NCS):**<br />   - Sensory NCS, established by Dawson in 1956, are vital for diagnosing peripheral neuropathies, often more sensitive than motor studies.<br />   - They detect early changes in sensory latencies and amplitudes, crucial in conditions like carpal tunnel syndrome and other nerve injuries.<br /><br />2. **Technical Considerations:**<br />   - Accurate sensory nerve action potential (SNAP) readings require considerations like limb temperature, electrode placement, and technique (orthodromic vs. antidromic).<br />   - Technical issues such as shock artifact, limb edema, and patient relaxation can affect the results.<br /><br />3. **Specific Sensory Conduction Studies:**<br />   - Detailed methodologies for studying various nerves, including dorsal cutaneous branch of the ulnar nerve, superficial radial nerve, medial and lateral antebrachial cutaneous nerves, and others, are provided.<br />   - Provides normal values and interpretation guidelines for each nerve study to differentiate between normal and pathological conditions.<br /><br />4. **Diagnostic Procedures for Carpal Tunnel Syndrome (CTS):**<br />   - Evaluates median and ulnar mixed nerve latencies, sensory latency differences, and motor latencies using techniques such as:<br />     - Median-ulnar mixed nerve latency difference.<br />     - Median-radial sensory latency difference.<br />     - Median-ulnar sensory latency difference to the ring finger.<br />     - Median-median mid-palmar sensory study.<br />     - Short segment sensory stimulation (inching).<br />   - Emphasizes the need to consider anatomical and technical variables to avoid false positives.<br /><br />5. **Combined Sensory Index (CSI):**<br />   - The CSI, integrating results from multiple tests (e.g., median-ulnar palmar, median-radial thumb, and median-ulnar ring finger differences), improves diagnostic accuracy for CTS.<br />   - Use of multiple tests reduces the rate of false positives, increasing the reliability of the diagnosis.<br /><br />6. **Concluding Notes:**<br />   - Sensory conduction studies play a critical role in localizing nerve injuries and determining the extent of nerve damage.<br />   - Consistent technique and consideration of patient-specific factors are essential for obtaining reliable data.<br /><br />This synthesis underscores the complexity and precision required in sensory nerve studies, emphasizing their indispensable role in neuromuscular and electrodiagnostic medicine.
Keywords
sensory nerve conduction studies
peripheral neuropathies
carpal tunnel syndrome
CTS
SNAP readings
technical considerations
median-ulnar latency
Combined Sensory Index
electrodiagnostic medicine
nerve injuries
AANEM Annual Meeting
CTS
carpal tunnel syndrome