Objective: To determine the incidence and etiology of lower motor neuron (LMN) vs upper motor neuron (UMN) lesions in patients with complete thoracic and lumbar spinal cord injuries (SCI).
Design: Retrospective chart review.
Setting: A regional Model Spinal Cord Injury System center.
Methods: A consecutive sample of medical records of patients with lower thoracic and upper lumbar (T7-L3) complete SCI admitted from 1979 through 1996 was systematically reviewed. Of the 306 patients evaluated, 156 subjects met inclusion criteria. The incidence and etiology of LMN vs UMN lesions were determined for the following neurologic levels: T7-T9, T10-T12, L1-L3. Lesions were classified as LMN, UMN, or mixed on the basis of the presence or absence of (1) the bulbocavernosus reflex, (2) lower limb deep tendon reflexes below the neurologic level of injury, and (3) the Babinski sign.
Results: The incidences of LMN, UMN, and mixed lesions in the T7-T9, T10-T12, and L1-L3 groups were as follows: T7-T9 group (7.3% LMN, 85.5% UMN, 7.3% mixed), T10-T12 group (57% LMN, 17.7% UMN, 25.3% mixed),L1-L3 group (95.5% LMN, 0.0% UMN, 4.5% mixed). Etiology of injury did not significantly influence the likelihood of a LMN lesion.
Conclusions: One cannot determine the type of lesion (UMN vs LMN) on the basis of the neurological level of injury. A detailed clinical examination, including sacral reflexes, is required. This has important prognostic and therapeutic implications for bowel, bladder, and sexual function, as well as mobility. Distinguishing UMN lesions from LMN lesions is also essential for evaluating new interventions in clinical trials for UMN pathology.