Diagnostic value of extensor digitorum brevis F-wave in L5 root compression.

The sensibility of F-wave in detecting lumbosacral radicular compression has been found to range from 65% to 18%. The present study was performed on 24 patients suffering from unilateral L5 compressive radiculopathy. The aim was to verify the reliability of extensor digitorum brevis (EDB) F-wave in the diagnosis of L5 root impairment, by using different parameters such as minimal, mean, maximal latency and the difference of these parameters between the affected and unaffected sides. In all patients conventional needle EMG was also performed bilaterally. While the needle EMG showed abnormalities in L5 innervated muscles of all patients, at least one of the different EDB F-wave parameters was found to be abnormal in only 7 patients (29.2%). Moreover no significant relation was observed between the severity of EMG and F-wave abnormalities. We conclude that conventional needle EMG appears to be the most useful electrophysiological technique in the diagnosis of L5 compressive radiculopathy, while EDB F-wave does not provide additional information.

Modulation of flexor carpi radialis H reflex by lateral tilts in man.

Static vestibular influences on upper limb flexor tone were studied in man by analyzing the changes in flexor carpi radialis H reflex area with lateral tilting of the longitudinal body axis. Ten healthy volunteers and 2 labyrinthine defective patients were tested in an experimental situation designed to minimize all afferent inputs except vestibular ones. Each subject was seated on a chair which could be tilted laterally to the left or the right from the vertical. Head and trunk were fixed upright, upper and lower limbs in half-flexed position and forearm in an intermediate position between supination and pronation. Lateral tilting was applied at random from the vertical (0 degrees control position) to left and right (4 degrees, 8 degrees, 12 degrees, 16 degrees, 20 degrees test positions). Each test position was followed by a return to 0 degrees and in each control and test position 20 consecutive H reflexes were recorded. The data observed in the normal subjects showed flexor tone inhibition in the arm which was tilted downwards and facilitation in the contralateral arm. These findings suggest that in man, like in animals, labyrinth reflexes act asymmetrically and in the opposite direction to neck reflexes.

Tonic neck reflexes on upper limb flexor tone in man.

The asymmetric tonic neck reflexes on upper limbs in man have been studied by analyzing the changes in flexor carpi radialis H-reflex amplitude following body rotation around the longitudinal axis with a stationary head. In eight normal subjects 15 consecutive H-reflexes were recorded from the right flexor carpi radialis muscle at each test position. The tested body rotation angles were 4, 8, 12, 16, and 20 degrees both to the right side and to the left side. Before and after each test position 15 H-reflexes were recorded at 0 degrees. The linear correlation coefficient r, computed by plotting the H-reflex amplitudes against the relevant body rotation angles, was significant in all the subjects. The FCR H-reflex amplitude increased with contralateral body rotation (i.e., ipsilateral head rotation) and decreased with ipsilateral body rotation (i.e., contralateral head rotation). It has been suggested that these findings, which are opposite to those observed in animal experiments, are the consequence of the acquired antigravity function of upper limb flexor muscles in man.

Influences of neck receptors on soleus motoneuron excitability in man.

We studied the influence of the asymmetric tonic neck reflexes on the excitability of the human soleus motoneuronal pool by mapping the H amplitude as a function of rotation of the body relative to the fixed head. Eight normal adult volunteers were tested. On each subject 15 consecutive H reflexes were recorded from the right soleus muscle, for each of the following test position, 4 degrees, 8 degrees, 12 degrees, 16 degrees, as well as at the control position (0 degrees), both before and after each change in body position. Our results showed that the H reflex amplitude was progressively facilitated for contralateral rotation in respect to the recording side and conversely inhibited for ipsilateral rotation. The results indicate that neck receptors of one side enhance the excitability of the contralateral soleus motoneurons and depress the ipsilateral ones.