Abstract & Commentary
Source: Rainville J, et al. Comparison of four tests of quadriceps strength in L3 or L4 radiculopathies. Spine. 2003;28: 2466-2471.
Thirty-three consecutive patients with l3 or l4 radiculopathy were compared to 19 controls of comparable age to determine the best method for detecting quadriceps weakness in the office setting. Controls had either L5 or S1 radiculopathy to allow for the effect that pain might have in preventing full effort. Radiculopathy was in all instances documented by magnetic resonance or computerized tomographic scan, demonstrating compression of the appropriate nerve root. Patients were excluded if they had bilateral radiculopathy, peripheral neuromuscular disease, physical signs suggesting non-organic amplification of symptoms, hip or knee arthritis, cancer, or psychiatric disorders. Four testing methods were studied: 1) The single leg sit-to-stand test, with the seated patient asked to extend one leg, hold that foot above the floor, and rise to the standing position with the other leg. The examiner could hold the patient’s hands for balance; 2) The step-up test, with the patient stepping up onto a standard 7-inch step-stool, again holding the examiner’s hands for balance; 3) The knee-flexed manual muscle test, with the patient supine, the hip flexed to 90°, the knee maximally flexed, and the patient attempting to extend the knee against the examiners resistance; and 4) The knee-extended manual muscle test, as in the knee-flexed manual muscle test but with the knee extended and the examiner trying to overcome knee extension. Reliability of findings was enhanced by a second examiner separately performing the identical examination. Statistical analysis was performed using frequency and means calculations, with kappa values calculated to determine inter-rater reliability.
The single leg sit-to-stand test was the most sensitive, with positivity in 61% (20/33). None of the controls failed this test. Knee-flexed and knee-extended manual muscle testing was positive in 42% and 9% of patients, respectively, with 1 control having weakness on the former. Step-up onto stool testing was positive in 27% of patients (9/33) but in no controls. Single-leg sit-to-stand quadriceps testing should be incorporated into the neurologic exam of suspected L3 or L4 radiculopathy where standard muscle tests fail to demonstrate quadriceps weakness. Suspected femoral neuropathy would be another scenario where this would be useful. Knee-extended manual muscle testing of the quadriceps is a waste of time.
How might sensory deficits be quantified in radiculopathy? Forty-eight patients with lumbosacral radiculopathy, secondary to magnetic resonance-documented L5 or S1 unilateral disc herniation, were examined using current perception threshold (CPT) evaluation to study A-beta, A-delta, and C fiber function.1 Using a neurometer device, 3 electric current frequencies, 2000, 250, and 5 Hz, were administered to the L5 and S1 dermatome on the dorsal side of the first and fifth metatarsal, respectively. A visual analog scale was used to score pain intensity. Eleven healthy volunteers served as controls, and both legs were studied in all subjects.
Among radiculopathy patients, CPT values were significantly higher, at all frequencies, in the affected leg compared to the contralateral leg. Compared to controls, values were higher at 2000 and 250 Hz but not at 5 Hz. No significant CPT difference was found between the left and right legs in controls for any frequency. CPT testing may be useful to quantify small-fiber sensory nerve dysfunction in patients with radiculopathy. — Michael Rubin, Associate Professor of Clinical Neurology and Neuroscience, New York Presbyterian Hospital- Cornell Campus; Assistant Editor, Neurology Alert.
1. Yamashita T, et al. Spine. 2002;27:1567-1570.