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Tremor and Clonus

Richard B. Stein, Robert G. Lee

10.1002/cphy.cp010209

Source: Supplement 2: Handbook of Physiology, The Nervous System, Motor Control

Originally published: 1981

Published online: January 2011

Full Article on Wiley Online Library



Abstract

The sections in this article are:

1 Types of Tremor and Clonus
1.1 Physiological Tremor
1.2 Pathological Tremors
1.3 Anatomic Relationships
1.4 Clonus
2 Mechanisms of Tremor
2.1 Mechanical Oscillations
2.2 Reflex Oscillations
2.3 Central Oscillations
3 Conclusions
Figure 1. Figure 1.

Supraspinal anatomical structures involved in various types of tremor. See discussion in text. Numbers identify structures involved in tremor generation or sites where lesions either produce or abolish tremor.
Figure 2. Figure 2.

A: schematic representation of mechanical oscillator consisting of mass, M, spring of stiffness, K, and dashpot with viscosity, D. B: relative magnitude of responses to forces of different frequencies (relative to the natural frequency, fn) for several values of damping ratio (0.1–1). Note that for low damping ratios (ζ ≪ 1), which occur when viscosity, D, is low according to Equation 6, the response is highly peaked, with maximum when f ∼ fn.
Figure 3. Figure 3.

A: schematic diagram of biceps muscle contracting against mass of forearm and its load. B: classic length‐tension curve of muscle. Slope of this curve gives muscle stiffness, K, which depends on muscle length and state of muscle (whether it is actively contracting or is passive). C: more complete mechanical diagram indicating interaction between components of muscle and its load.

C from Oğuztöreli and Stein 96
Figure 4. Figure 4.

A: in absence of sensory feedback, rhythmic input (at 5 Hz) from central nervous system produces a change in muscle length or limb position at same frequency as input, but filtered somewhat in amplitude (model calculation based on Fig. 3C). B: after adding sensory feedback to model, frequency approximately doubles (to nearly 11 Hz) over shown period of 1 s. See Oğuztöreli and Stein 96 for details of assumed spinal stretch reflex pathway. A saturation type of nonlinearity was included to limit or normalize range of positions to ±1 in all parts of figure. C: applying an external 9‐Hz oscillation in limb position with same amount of sensory feedback produces clear modulation in envelope with “beat” frequency near 2 Hz. D: applying brief perturbation at t = 0 in absence of sinusoidal inputs produces slowly growing reflex oscillation. Second pulse at t = 0.525 s can reset oscillation without greatly modifying amplitude.
Figure 5. Figure 5.

A: effect of brief pulse at different phases of sinusoidal oscillation in resetting oscillation. Increasing amplitude of pulse (relative amplitudes are given on right) increases degree of resetting. This is indicated by slope of linear portion of curve that increases over range of 0 to 1 for linear model.

Described in detail by Oğuztöreli and Stein 97.] B: torque pulses applied to patient with essential tremor largely reset electromyogram (EMG) peaks associated with ongoing oscillation (slope near 1). Times are given in ms relative to 240‐ms period of tremor (∼4 Hz). C: similar pulses applied to patient with parkinsonian tremor had little effect on timing of EMG peaks (slope not significantly greater than 0). Frequency of tremor was 5 Hz. D: torque pulses applied to monkey with intention tremor produced by cooling cerebellar nuclei. Intermediate degree of resetting for peaks of positive velocity is observed (slope near 0.5). A from Oğuztöreli and Stein 97; B and C from Stein, Lee, and Nichols 113; D, replotted from Villis and Hore 120
Figure 6. Figure 6.

A: independent motoneurons (indicated schematically on left) firing at less than tetanic rates (upper right) produce random fluctuations in force (lower right) that contain frequency components corresponding to their individual firing rates. B: coupling within motoneuron pool from sensory feedback (see connections from muscle spindle) or from central feedback (see connections from Renshaw cell) gradually produce more rhythmic tremor of small amplitude. C: coupling between antagonistic motoneuron pools involves mechanical linkage, which is sensed by muscle receptors and produces an alternating tremor. Note change in relative scale used in plotting tension. D: reflex connections from muscle receptors (Ia inhibitory interneurons are shown) can again increase the amplitude and rhythmicity of the tremor. Muscle not shown. E: central oscillators (mutually inhibitory interneurons which receive excitation from higher centers are shown) can have a similar effect and the relative importance of central and peripheral influences is often difficult to determine. The symbols used in all parts of the figure are as follow: motoneuron, ○; interneuron, ○; muscle spindle, —○—; excitatory synapse, −<; inhibitory synapse, —•. The times of motoneuronal firing in A to C could be produced by a number of simple neural models, and the resulting force fluctuations were computed using second‐order model of muscle 5,77.


Figure 1.

Supraspinal anatomical structures involved in various types of tremor. See discussion in text. Numbers identify structures involved in tremor generation or sites where lesions either produce or abolish tremor.



Figure 2.

A: schematic representation of mechanical oscillator consisting of mass, M, spring of stiffness, K, and dashpot with viscosity, D. B: relative magnitude of responses to forces of different frequencies (relative to the natural frequency, fn) for several values of damping ratio (0.1–1). Note that for low damping ratios (ζ ≪ 1), which occur when viscosity, D, is low according to Equation 6, the response is highly peaked, with maximum when f ∼ fn.



Figure 3.

A: schematic diagram of biceps muscle contracting against mass of forearm and its load. B: classic length‐tension curve of muscle. Slope of this curve gives muscle stiffness, K, which depends on muscle length and state of muscle (whether it is actively contracting or is passive). C: more complete mechanical diagram indicating interaction between components of muscle and its load.

C from Oğuztöreli and Stein 96


Figure 4.

A: in absence of sensory feedback, rhythmic input (at 5 Hz) from central nervous system produces a change in muscle length or limb position at same frequency as input, but filtered somewhat in amplitude (model calculation based on Fig. 3C). B: after adding sensory feedback to model, frequency approximately doubles (to nearly 11 Hz) over shown period of 1 s. See Oğuztöreli and Stein 96 for details of assumed spinal stretch reflex pathway. A saturation type of nonlinearity was included to limit or normalize range of positions to ±1 in all parts of figure. C: applying an external 9‐Hz oscillation in limb position with same amount of sensory feedback produces clear modulation in envelope with “beat” frequency near 2 Hz. D: applying brief perturbation at t = 0 in absence of sinusoidal inputs produces slowly growing reflex oscillation. Second pulse at t = 0.525 s can reset oscillation without greatly modifying amplitude.



Figure 5.

A: effect of brief pulse at different phases of sinusoidal oscillation in resetting oscillation. Increasing amplitude of pulse (relative amplitudes are given on right) increases degree of resetting. This is indicated by slope of linear portion of curve that increases over range of 0 to 1 for linear model.

Described in detail by Oğuztöreli and Stein 97.] B: torque pulses applied to patient with essential tremor largely reset electromyogram (EMG) peaks associated with ongoing oscillation (slope near 1). Times are given in ms relative to 240‐ms period of tremor (∼4 Hz). C: similar pulses applied to patient with parkinsonian tremor had little effect on timing of EMG peaks (slope not significantly greater than 0). Frequency of tremor was 5 Hz. D: torque pulses applied to monkey with intention tremor produced by cooling cerebellar nuclei. Intermediate degree of resetting for peaks of positive velocity is observed (slope near 0.5). A from Oğuztöreli and Stein 97; B and C from Stein, Lee, and Nichols 113; D, replotted from Villis and Hore 120


Figure 6.

A: independent motoneurons (indicated schematically on left) firing at less than tetanic rates (upper right) produce random fluctuations in force (lower right) that contain frequency components corresponding to their individual firing rates. B: coupling within motoneuron pool from sensory feedback (see connections from muscle spindle) or from central feedback (see connections from Renshaw cell) gradually produce more rhythmic tremor of small amplitude. C: coupling between antagonistic motoneuron pools involves mechanical linkage, which is sensed by muscle receptors and produces an alternating tremor. Note change in relative scale used in plotting tension. D: reflex connections from muscle receptors (Ia inhibitory interneurons are shown) can again increase the amplitude and rhythmicity of the tremor. Muscle not shown. E: central oscillators (mutually inhibitory interneurons which receive excitation from higher centers are shown) can have a similar effect and the relative importance of central and peripheral influences is often difficult to determine. The symbols used in all parts of the figure are as follow: motoneuron, ○; interneuron, ○; muscle spindle, —○—; excitatory synapse, −<; inhibitory synapse, —•. The times of motoneuronal firing in A to C could be produced by a number of simple neural models, and the resulting force fluctuations were computed using second‐order model of muscle 5,77.

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Article Title: Tremor and Clonus
 

How to Cite

Richard B. Stein, Robert G. Lee. Tremor and Clonus. Compr Physiol 2011, Supplement 2: Handbook of Physiology, The Nervous System, Motor Control: 325-343. First published in print 1981. doi: 10.1002/cphy.cp010209