T-reflex studies in human upper limb muscles during voluntary contraction: normative data and diagnostic value for cervical radiculopathy.

OBJECTIVE

To evaluate the diagnostic utility of the T reflexes elicited from the upper limb muscles during standardized volitional contraction monitored by a real-time integrating electromyographic analyzer.

DESIGN

Prospective descriptive study.

SETTING

Department of orthopedic surgery at a university hospital.

PARTICIPANTS

Healthy subjects (n=80) evenly distributed across decades of age from 21 to 79 years, and 12 consecutive patients with a single cervical root lesion based on clinical and magnetic resonance imaging studies and diagnostic block.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Using a special hammer, which externally triggers the sweep on skin contact, we evoked T reflexes in the biceps (C5), brachioradialis (C6), triceps (C7), and the first dorsal interosseous muscles (C8).

RESULTS

Simultaneous regression analyses yielded clinically useful upper limits of normative values for latencies, side-to-side differences, and amplitude ratios adjusted to age and arm span. Comparison of the T reflexes between the 2 sides localized the solitary root lesions with a high sensitivity (92%), specificity (81%), and accuracy (83%). T-reflex studies proved helpful to localize the lesion even in patients who solely complained of upper limb pain.

CONCLUSIONS

The T reflexes with a standardized facilitation of the upper limb muscles provide a clinically useful, noninvasive measure to localize the C5 to C8 radiculopathies. This study contributes in reassessing the currently underused T reflex as an electrodiagnostic technique.