Can testing of six individual muscles represent a screening approach to upper limb neuropathic conditions?

Abstract

Background: It has previously been demonstrated that an extensive upper limb neurological examination of individual muscle function, sensation in homonymous innervated territories, and nerve trunk allodynia is reliable and that the outcome reflects symptoms. Since this approach may appear complicated and time consuming, this study deals with the value of an examination limited to manual testing of only six muscles.

Methods: Two examiners blinded to symptom status performed manual muscle testing of six muscles in 82 upper limbs with or without pain, weakness, and/or numbness/tingling. The six muscles represent three antagonist pairs (pectoralis major/posterior deltoid, biceps/triceps, and radial flexor of wrist/short radial extensor of wrist). The inter-rater reliability of detecting muscular weaknesses and the relation of weakness to the mentioned symptoms were analysed by kappa-statistics.

Results: The two examiners recognized weaknesses in 48 and 55 limbs, respectively, with moderate agreement (median kappa = 0.58). Out of these, 35 and 32 limbs, respectively, were symptomatic. There was good correlation between findings and symptoms for one examiner (kappa = 0.61) and fair correlation for the other one (kappa = 0.33). Both reached high sensitivity (0.92, 0.84) but less satisfactory specificity (0.70, 0.50). Weaknesses agreed upon by the two examiners correlated moderately with symptoms (kappa = 0.57).

Conclusions: Weakness in one or more muscles was present in almost all symptomatic limbs but in many non-symptomatic limbs as well. Manual testing of six muscles may represent a useful screening approach to upper limb neuropathic conditions, but a confirmative diagnosis requires further assessment.

Figure 1

Roots, brachial plexus, and upper limb peripheral nerves. Overview and innervation of the selected six upper limb muscles.

Figure 2

Standard posture I. Testing of the pectoral muscle. The arrow illustrates the direction of the examiner’s force against the patient’s resistance. The posterior deltoid muscle works as the antagonist.

Figure 3

Standard posture I. Testing of the posterior deltoid muscle. The arrow illustrates the direction of the examiner’s force against the patient’s resistance. The pectoral muscle works as the antagonist.

Figure 4

Standard posture II. Testing of the biceps brachii muscle. The arrow illustrates the direction of the examiner’s force against the patient’s resistance. The triceps muscle works as the antagonist.

Figure 5

Standard posture II. Testing of the triceps muscle. The arrow illustrates the direction of the examiner’s force against the patient’s resistance. The biceps brachii muscle works as the antagonist.

Figure 6

Standard posture III. Testing of the flexor carpi radialis muscle. The arrow illustrates the direction of the examiner’s force against the patient’s resistance. The short extensor of wrist muscle works as the antagonist.

Figure 7

Standard posture III. Testing of the extensor carpi radialis brevis muscle. The arrow illustrates the direction of the examiner’s force against the patient’s resistance. The flexor carpi radialis muscle works as the antagonist.