CONTRIBUTION OF NEUROMUSCULAR IMPAIRMENT TO PHYSICAL FUNCTIONAL STATUS IN PATIENTS WITH LUMBAR SPINAL STENOSIS

Objective. To evaluate the relationship between neuromuscular impairme nt and physical functional status in patients with lumbar spinal steno sis. Methods. Cross sectional analysis of 217 consecutive patients wit h lumbar spinal stenosis referred to 3 teaching hospitals. Physical fu nctional status was measured with the physical dimension of the Sickne ss Impact Profile (P-SIP). Physical and radiological findings were abs tracted from clinical records. The neuromuscular findings included pin sensation, strength, deep tendon reflexes and vibration. They were ag gregated in a neuromuscular impairment index (NMI). Univariate relatio nships of the P-SIP and the NMI were analyzed with nonparametric metho ds. The determinants of physical functional status were evaluated usin g multiple linear regression models. Results. In 148 patients with com plete clinical data, objective weakness of the lower extremity as meas ured at rest was not related to physical functional status in univaria te analyses. Decreased vibration was common and was associated with ba lance disturbance and reduced physical functional status, reflecting t he importance of proprioception loss. In the multivariate regression a nalysis, neuromuscular deficit explained only 2.5% of the variance in physical functional status. The primary determinants of physical funct ional status were pain, depression, comorbid conditions and work statu s. Conclusion. While neuromuscular impairment is an indispensable feat ure of the diagnostic evaluation, its value in assessing outcome is li mited. The decision whether to intervene surgically in patients withou t cauda equina syndrome or rapidly progressive neurological deficits s hould therefore be driven by pain and physical disability rather than the degree of neuromuscular impairment.