[Neurophysiological diagnosis of lumbosacral radicular compression syndrome from late responses]

Lumbosacral radicular compression syndrome is a disorder that can affect anyone at some moment in their lives, regardless of their sex, age and profession. It appears more frequently in specific groups of people. Late responses constitute neurophysiological studies that allow evaluation of the functional state of the proximal portions of the peripheral nervous system, which are affected to a greater or lesser extent in the course of this pathological state. AIMS. To determine the usefulness of the F wave and H reflex in lumbosacral compressive radiculopathies at L5 and S1.

We examined 100 patients who had been clinically and imagenologically diagnosed as suffering from lumbosacral compressive radiculopathy, which was classified as being L5 and S1. Late responses (F wave and H reflex) were performed and they were compared with a group made up of 74 normal subjects.

In patients with L5 radiculopathy, the F wave was abnormal in 66.6% of the cases, where a reduction in the percentage of waves obtained from patients and prolonged minimum, average and maximum latencies predominated. In the case of patients with S1 lumbosacral compressive radiculopathies, 77.5% presented H reflex alterations and the main abnormalities were detected as being the prolongation of reduced amplitude latencies and the absence of response.

The F wave and H reflex are useful tools for evaluating patients with compressive radiculopathies at L5 and S1, respectively.