The current technique taught for examining the muscles of the upper limb does not differentiate between the various causes of weakness in the arm, in particular peripheral nerve and nerve root lesions. The 5.3.5 rule describes examining the muscles in a specific order: 5 at the shoulder, 3 at the elbow and 5 at the wrist and hand. The examiner records the number of the weak muscles. They then consult the tables to determine the cause of the weakness. This rule enables the diagnosis of all peripheral nerve and nerve root problems (radiculopathy) that cause weakness in the arm. It does not require detailed knowledge of neuroanatomy. It does require the examiner to learn how to examine each muscle so that they do not miss weakness or ‘detect’ weakness when there is none.
- peripheral nerve lesion
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Funding PG receives royalties from his book Clinical Neurology: A Primer and receives money from subscriptions to his educational website, www.understandingneurology.com. He does not have any links to the pharmaceutical industry.
Competing interests None declared.
Patient consent for publication Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
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