Fusimotor Nerve Function in Man

Landau, William M.

doi:10.1001/archneur.1960.00450010010002

Arch Neurol

1960

DOI: 10.1001/archneur.1960.00450010010002

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Fusimotor Nerve Function in Man

William M. Landau¹

Abstract: the last decade indicates that such a system does, indeed, exist, although not in the sense of a mechanism that produces tonic muscular contraction directly.The efferent innervation of muscle spindle tension receptors by a special group of ventral spinal root fibers was first suggested by the finding that stimulation of the small (gamma) ventral root fibers (comprising about 25% of the total in the cat) produced no further muscle shortening beyond that produced by stimulation of the large (alpha) motor fibers.… Show more

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Cited by 51 publications

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“…Selective intrathecal phenol block of spinal nerve roots was shown by Nathan (11) and by Landau et al (12) to decrease spasticity. Kjellberg et al (13) lessened rigidity in the lower limbs of parkinsonian patients by selective block of the ventral nerve roots with 5 per cent phenol.…”

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confidence: 96%

Spasmolysis: A New Technique for Treatment of Spasticity: Preliminary Report

Cooper

Hirose

1964

J American Geriatrics Society

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ANDMuscle spindles, located within voluntary muscle, have been identified as sensory organs which play a major role in the control of muscular contraction during both motion and the steady state (1-3). These spindles are now believed to have a double motor as well as a double sensory supply (4). The muscle spindle, via its sensory fibers, supplies the central nervous system with information concerning the state of the muscles, while the fusimotor element of the spindle serves as a motor regulator of incoming sensory information. These fusimotor elements are part of the gamma motor system. Impulses from the primary sensory endings of the spindle excite the alpha motor neurons monosynaptically, thus supplying the basis of the monosynaptic reflex arc. By differentially damping or suppressing this monosynaptic reflex arc, it should be possible to lessen or abolish spasticity while preserving voluntary motor activity. This communication is a preliminary report of a new technique aimed at producing a differential block of the muscle spindle. The technique consists of perfusion of the isolated lower limb with 0.2 per cent phenol; this process diff erentially lyses the gamma fibers, which are more susceptible to this agent than are the larger motor or sensory fibers.The concept of differential necrosis within the central nervous system is not new. It is seen most notably in certain neurologic diseases. For example, poliomyelitis attacks the motor neurons of the spinal cord and brain stem while sparing the sensory elements. On the other hand, the virus of herpes zoster selects the sensory ganglion cells for its destructive attack, without molesting the motor neurons.Gasser and Erlanger ( 5 ) demonstrated that nerve fibers of various size differ in their response to various blocking agents. This finding led to the differential block of spinal nerve roots by procaine or phenol for the purpose of selectively inhibiting or destroying nerve fibers of small diameter (6, 7). Since both the large afferent fibers and the large motor fibers are more resistant to phenol block than are the small fibers of the gamma motor type, it should be possible to remove gamma activity differentially without materially affecting alpha motor function. Matthews (8) demonstrated such a selective effect with regard to the stretch reflex. Walshe (9), Rushworth (10) and others have reported a similar effect on parkinsonian rigidity.Selective intrathecal phenol block of spinal nerve roots was shown by Nathan (11) and by Landau et al. (12) to decrease spasticity. Kjellberg et al. (13) lessened

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mentioning

confidence: 96%

Spasmolysis: A New Technique for Treatment of Spasticity: Preliminary Report

Cooper

Hirose

1964

J American Geriatrics Society

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Fusimotor Function

HUNT¹

1963

Arch Neurol

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Spinal shock was defined by Franz 1 as the "state of depression of spinal reflexes (hyporeflexia), generally transient in character, which occurs after transection in the bodily segments caudal to the lesion." Of several hypotheses,2,3 the most widely accepted is that of Sherrington: "Reflex depression is due to the sudden withdrawal of a continuous excitation (facilitation) which normally occurs from suprasegmental levels."4 Sherrington and Fulton observed that in monkeys spinal shock and the subsequent permanent disability are more severe and much longer lasting than in cats and dogs.5,6In man it is well known that shock is even more severe and lasts longer than in monkey.Yet neither the intrinsic mechanism of the phenomenon nor its species variations are well understood.Out of recent knowledge of the fusimotor (gamma efferent) system which functions to regulate the sensitivity of muscle stretch receptors, the idea has developed that the system is specifically disturbed in pathological states. C. C. Hunt T demonstrated that the proprioceptive (monosynaptic) stretch re¬ flex can be enhanced by stimulation of effer-ent fusimotor axons going to the spindles of the same muscle. Conversely Matthews and Rushworth 8 showed that the stretch reflex is abolished during selective block of fusi¬ motor fibers by a local anesthetic.The proposal has been made that volun¬ tary reinforcement of tendon jerks in man (Jendrassik maneuver) results from in¬ creased fusimotor activity.9·10 Others have speculated that disorders of movement, such as those of cerebellar disease, spasticity and parkinsonian rigidity and tremor, may arise out of disturbances in fusimotor tone.11"19It is a paradox of human spinal shock that the polysynaptic flexion reflex recovers ear¬ lier than the monosynaptic stretch reflex.20 This finding suggests that central synaptic transmission is not wholly depressed and that the stretch receptor path may be blocked peripherally rather than centrally. Thus the rise in stretch receptor threshold could be due to decreased tonic fusimotor activation.This series of papers seeks answers to these questions. It includes the results of examinations of the state of fusimotor tone associated with spinal shock in the cat, mon¬ key, and man, and that associated with chronic spasticity in the monkey. In the ani¬ mal studies the afferent volley in a muscle nerve activated by a constant brief stretch stimulus is used as an integrated measure of the muscle stretch receptor excitability. Since receptor sensitivity under constant load is a function of the level of activity in the spindle efferents, fusimotor tone can be measured indirectly.

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Fusimotor Function

WEAVER¹

1963

Arch Neurol

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The depression of neural activity which takes place in the distal spinal cord abruptly separated from rostral control is the classical model for interpreting the transient disturbances of neural function that follow acute lesions of the nervous system. The behavior of isolated spinal cord has been relatively easy to analyze because its afferent and efferent pathways are so accessible.Modern neurological thinking is firmly based upon the observations of spinal cord behavior made in animals by Sherrington and in man by many clinicians of his generation. The riddle of spinal shock and the even more puzzling recovery to a hyperactive state which evolves out of it are little nearer solution now than when originally described. The most widely accepted explanation of shock is that the cord's internuncial pool and final common path are depressed below normal levels of excitability by the sudden transection of descending, largely excitatory pathways.1 Some recent observations in man 2 show that the monosynaptic stretch reflex recovers earlier in the more caudal spinal segments. From this it was inferred that rostrad recovery from spinal shock may ex¬ plain the evolution from the early flexor plantar reflex seen immediately after cord section to the extensor response of the chronic state.A paradox noted in that study and docu¬ mented much earlier is that the polysynaptic plantar (flexion) reflex may be evident im¬ mediately after cord section, when the monoor oligosynaptic segmental stretch reflex of

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Fusimotor Nerve Function in Man

Cited by 51 publications

References 35 publications

Spasmolysis: A New Technique for Treatment of Spasticity: Preliminary Report

Spasmolysis: A New Technique for Treatment of Spasticity: Preliminary Report

Fusimotor Function

Fusimotor Function

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