Musculus extensor digitorum brevis is clinical and electrophysiological marker for L5/S1 radicular lesions

In clinical electromyography (EMG) musculus extensor digitorum brevis (MEDB) is known as "the marker" for L5/sl radiculopathy. Radiculopathy is mainly sensory syndrome in which the pain appears in innervation's zone of one or more spinal nerves. Moreover, in clinical practice it is also known that radiculopathy is not only sensory disorders but also may be followed by muscle weakness and atrophy. Since atrophy of MEDB is often seen clinical feature in careful neurological exam of the patients with lumbosacral radiculopathy, it is made attempt to determine usefulness of this sign, for clinical diagnosis of radicular lesions. For this purpose 100 patients with lumbosacral radiculopathy and MEDB atrophy and 100 patients with low back pain have been studied. Control group consisted of 50 healthy volunteers. The patients underwent neurological examination, CT scan of lumbosacral region and EMG including motor conduction velocity (MCV) of deep peroneal nerve (DPN), F-wave and H-reflex analysis. The most patients in first group had moderate and severe radicular lesions of radix L5/sl proved by EMG examination. MCV in DPN on atrophy side was 43.4+/- 2.65 m/sec, and on side without MEDB atrophy 47.18 +/- 1.63 m/sec (p < 0.001). MCV in control group was significantly higher then in both group of patients (left side - 47.65 +/- 1.53 m7sec: right side--47.70 +/- 1.59 m/sec) (p < 0.001). Significant correlation between the MEDB atrophy and MCV (r = -0.67) and F-wave latency (r = 0.86) and H-reflex latency (r = 0.87) has been proved. It is concluded that MEDB atrophy is very important parameter in clinical evaluation of patients with lumbosacral radiculopathy and could be clinical and electrophysiological marker for L5/Sl radicular lesions.