Buchbesprechungen

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Knochenbrüche bei Cardiazolkrampf-Behandlung der Schizophrenie und Ihre Verhütung

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Schmerzsyndrome des Bewegungsapparates

Clinical pain syndromes affecting the locomotor apparatus can become apparent not only in the form of nociceptive pain in the skeleto-mechanical system, but also as neurogenic pain emanating from lesions in the peripheral nerves or nerve roots or as referred pain resulting from disorders of visceral organs. The anatomical structure and basic innervation can contribute to the various characteristics of such deep pain. Within the spinal cord, visceral and somatic afferent fibres converge on nociceptive pathways, resulting in a uniform clinical pain syndrome. The differential diagnosis can be extremely difficult when attempts are made to evaluate its clinical relevance. Pain radiating from deep somatic tissues into the extremities is called "pseudoradicular" pain. Examples are encountered in the "facet syndrome" or the "myofascial pain syndrome". Various types of treatment are available for musculo-skeletal disorders, including physiotherapy, transcutaneous nerve stimulation (TENS) and trigger point infiltration. In clinical practice, however, drug therapy with peripheral analgesics and anti-inflammatory drugs is the form of therapy most often prescribed. There is no doubt that these drugs can help a great deal. However, they have only a symptomatic effect without any influence on the origin or course of the disease. Therefore, a critical evaluation of their benefits and risks is required before treatment with such drugs is instituted.     

Responses of human muscle spindle afferents during isotonic position holding and active movements

Discharge characteristics of muscle spindle primary afferents from human finger flexors were investigated during load-bearing isotonic position holding, and intentional shortening or lengthening contractions. During position holding, units mostly showed a negative relationship between muscle length and impulse rate, particularly when the load was small. When the load was increased, Ia-discharge rates increased more in the elongated than in the shortened muscle, and the inverse position response became less pronounced. During active lengthening contractions, a stretch response pattern was sometimes absent or could be abolished by increasing the load.     

Function of early and late components of the blink reflex--study of discharge behavior of single motor units

The discharge pattern of single motor units in the early (R1) and late (R2) component of the electrically evoked trigemino-facial blink reflex was investigated by means of selective EMG-recording techniques. At low rate stimulation (0,1 Hz) the stimulus threshold of motor unit discharges in R1 was clearly above that in R2. Higher stimulation rates (1 Hz) were associated with an attenuation of motor unit discharges in R2 according to the well known habituation. The same motor units, however, revealed stable discharges in R1 or even signs of facilitation. These differences of motor unit recruitment in the two components indicate that R1 cannot be simply interpreted as a protective reflex like R2. At higher stimulus intensities, the characteristical firing pattern consisted of single discharges in R1 followed by high frequency multi-discharges of the same motor units in R2. This means that the motor unit discharges in R1 do not only evoke a single twitch of the eyelids but initiate a vigorous tetanic contraction with short latency. Thus, R1 yet reveals a protective function shortening the latency of the reflex blink upon stronger stimuli on the side of the affected eye.     

Assessment of fusimotor contribution to reflex reinforcement in humans

The contribution of the fusimotor system to reflex reinforcement such as the Jendrassik manoeuvre was investigated by recording single unit activity with tungsten electrodes from muscle spindle afferent nerves in unanaesthetized normal human subjects. Muscle spindle afferent activity was recorded before, during, and after the reinforcement test. When the leg muscles remained relaxed during the Jendrassik manoeuvre, spindle activity recorded in the tibial nerve was accelerated. Also in the median nerve, activity from muscle spindle afferent fibres was increased during a remote contraction of the ipsilateral quadriceps muscle. Comparing the time course of the phasic reflex reinforcement and the muscle spindle facilitation during the remote contraction, a marked after-effect was recorded in both responses. Present results show an increased spontaneous muscle spindle activity in relaxed muscles during a remote muscle contraction, and provide evidence for the contribution of the fusimotor system to the enhancement of phasic reflexes by reinforcement manoeuvres.     

The control of isometric contractions in patients suffering from different types of hypotonia

Different forms of hypotonia, resulting from various lesions in the somatosensory system, are discussed. In order to investigate the causes of hypotonia the forearm flexors of patients were stretched and the segmental EMG responses studied. Special attention was given to parkinsonian patients who were stereotaxically operated for the relief of tremor. These patients were studied before and after their operation and their reflex responses were compared to those of normal subjects. It was found that the M2 component was always significantly larger before operation when compared to normal subjects. This could be due to high-frequency firing of single motor units during the M2 interval, as shown with single unit analysis. After operation the M2 component was significantly reduced; clinically hypotonia was observed. It is thus suggested that hypotonia observable in parkinsonians following subthalamotomy and/or thalamotomy could be the result of the decreased M2-component. Pathways which may be interrupted by the lesion are discussed and possible mechanisms mediating unusually high M2-components are mentioned. The hypothesis is forwarded that the stereotaxic lesion may selectively interfere with the static gamma drive to muscle spindles.