Mateusz Gładysz FESSH prep

FESSH prep Compressive neuropathies ulnar neuropathy — electrodiagnostic evaluation

Electrodiagnostic findings in ulnar neuropathy at the elbow

Last reviewed v1.0

FESSH-016Compressive neuropathies●●○ intermediate

Regarding the electrodiagnostic evaluation of ulnar neuropathy at the elbow, which of the following statements are true?

  1. 1.Focal slowing of motor conduction velocity across the elbow is the principal electrodiagnostic feature of early demyelinating ulnar neuropathy at the elbow.

  2. 2.Reduced distal compound muscle action potential (CMAP) amplitude, particularly when accompanied by needle-EMG denervation, supports motor axonal loss and more advanced ulnar neuropathy.

  3. 3.Standard nerve conduction studies, performed in a fixed elbow position, may yield false-negative results in patients with intermittent or position-dependent ulnar nerve compression.

  4. 4.Needle electromyography detects denervation potentials — fibrillations and positive sharp waves — in ulnar-innervated muscles, supporting axonal involvement.

  5. 5.Short-segment (inching) conduction studies localise the site of ulnar nerve compression at the elbow more precisely than standard 10-cm across-elbow studies.

FESSH marking: +1 per correct statement, 0 for blank, −1 for incorrect. Click the same TRUE/FALSE button twice to clear it.

Question ID
FESSH-016
First published
Last reviewed
Version
v1.0
Answer key and explanations — open after answering

  1. 1. Focal slowing of motor conduction velocity across the elbow is the principal electrodiagnostic feature of early demyelinating ulnar neuropathy at the elbow.

    True

    The AAEM practice parameter recommends recording from abductor digiti minimi or first dorsal interosseous with the elbow flexed at approximately 90° and a short across-elbow segment of 10 cm. A drop in conduction velocity exceeding approximately 10 m/s across the elbow segment compared with the forearm segment is considered abnormal and reflects focal demyelination.

    • American Association of Electrodiagnostic Medicine, Campbell WW. Practice parameter for electrodiagnostic studies in ulnar neuropathy at the elbow: summary statement. Muscle Nerve Suppl. 1999;(8):S171-S205. PMID 16921634
    • Campbell WW, Carroll C, Landau ME. Ulnar neuropathy at the elbow: Five new things. Neurol Clin Pract. 2015;5(1):35-41. PMID 29443185

  2. 2. Reduced distal compound muscle action potential (CMAP) amplitude, particularly when accompanied by needle-EMG denervation, supports motor axonal loss and more advanced ulnar neuropathy.

    True

    CMAP amplitude at distal stimulation reflects the functioning motor axons supplying the recorded muscle. A low distal amplitude, particularly with needle-EMG denervation in ulnar-innervated intrinsics, supports axonal loss. An amplitude drop only across the elbow may instead reflect conduction block or temporal dispersion and should not be equated with motor axonal loss.

    • Power HA, Sharma K, El-Haj M, Moore AM, Patterson MM, Mackinnon SE. Compound muscle action potential amplitude predicts the severity of cubital tunnel syndrome. J Bone Joint Surg Am. 2019;101(8):730-738. PMID 30994591
    • American Association of Electrodiagnostic Medicine, Campbell WW. Practice parameter for electrodiagnostic studies in ulnar neuropathy at the elbow: summary statement. Muscle Nerve Suppl. 1999;(8):S171-S205. PMID 16921634

  3. 3. Standard nerve conduction studies, performed in a fixed elbow position, may yield false-negative results in patients with intermittent or position-dependent ulnar nerve compression.

    True

    Nerve conduction studies record a single static condition. Intermittent dislocation or position-dependent compression — for example a snapping nerve or anconeus epitrochlearis — may not produce demonstrable conduction abnormalities at rest. Ultrasound and dynamic ultrasonographic assessment complement electrodiagnostics in such cases.

    • Campbell WW, Carroll C, Landau ME. Ulnar neuropathy at the elbow: Five new things. Neurol Clin Pract. 2015;5(1):35-41. PMID 29443185
    • Mezian K, Jačisko J, Kaiser R, Machač S, Steyerová P, Sobotová K, et al.. Ulnar neuropathy at the elbow: from ultrasound scanning to treatment. Front Neurol. 2021;12:661441. PMID 34054704

  4. 4. Needle electromyography detects denervation potentials — fibrillations and positive sharp waves — in ulnar-innervated muscles, supporting axonal involvement.

    True

    Spontaneous activity (fibrillations, positive sharp waves) appears in denervated muscle fibres approximately two to three weeks after axonal injury. Needle examination of first dorsal interosseous, abductor digiti minimi and ulnar-innervated forearm muscles helps localise the lesion and quantify axonal loss.

    • American Association of Electrodiagnostic Medicine, Campbell WW. Practice parameter for electrodiagnostic studies in ulnar neuropathy at the elbow: summary statement. Muscle Nerve Suppl. 1999;(8):S171-S205. PMID 16921634
    • Campbell WW, Carroll C, Landau ME. Ulnar neuropathy at the elbow: Five new things. Neurol Clin Pract. 2015;5(1):35-41. PMID 29443185

  5. 5. Short-segment (inching) conduction studies localise the site of ulnar nerve compression at the elbow more precisely than standard 10-cm across-elbow studies.

    True

    Inching studies stimulate the nerve at 1- or 2-cm intervals across the elbow, identifying focal latency jumps or amplitude drops at the site of compression — typically the retroepicondylar groove or humeroulnar arcade. The AAEM parameter validates short-segment studies as superior for localisation when standard studies confirm a lesion at the elbow.

    • Campbell WW, Pridgeon RM, Sahni KS. Short segment incremental studies in the evaluation of ulnar neuropathy at the elbow. Muscle Nerve. 1992;15(9):1050-4. PMID 1518514
    • Campbell WW, Carroll C, Landau ME. Ulnar neuropathy at the elbow: Five new things. Neurol Clin Pract. 2015;5(1):35-41. PMID 29443185