abnormal muscle tone

abnormal muscle tone classification and clinical features

1. Muscle tone Dr.Satish K Pimpale PT MPTh in Neurosciences

2. Definition Tone is the resistance offered by muscles to continuous passive stretch (Brooks1986) Muscle tone can be defined clinically as the resistance that is encountered when the joint of a relaxed patient is moved passively (Maria Strokes)

3. Muscle tone degree of residual contraction in normally innervated ,resting muscles, or steady contraction. Resistance is due to number of factors. Physical inertia Intrinsic mechanical elastic stiffness of muscle and connective tissue. Reflex muscle contraction caused by muscle stretch

4. In a relaxed human subject with no neurological deficit, the resistance to passive movement is due to the mechanical factors such as the : Compliance of muscle Tendons Ligaments Joints rather than neural mechanism

5. Clinically muscle tone may be abnormally increased or decreased Hypertonia Hypotonia Dystonia

6. Hypertonia Spasticity and rigidity There are two rare types of hypertonia Gegenhaltan Alpha rigidity

7. Spasticity Spasticity may be defined as a velocity dependent increase in resistance to passive stretch of a muscle with exagggerated tendon reflex resulting from hyperexcitability of the stretch reflex as one component of the Upper motor neuron

8. Spasticity -arises from injury to the corticofugal pathways (pyramidal tracts)a Occurs as a part of UMN syndrome. Loss of inhibitory control on LMN results in disordered spinal segmental reflexes Increase alpha motor neuron excitability Increase spindle Ia Flexor reflex afferent excitability Altered synaptic activity Decrease presynaptic Ia inhibition rate

9. Additional sign and symtoms Brisk tendon reflex Involuntary flexor and extensor spasms Clonus Babinski’s sign Exaggerated cutaneous reflexes Loss of precise autonomic control Dyssynergic movement patterns Abnormal timing Paresis Loss of dexterity and fatigability

10. Chronic spasticity is associated with Contracture Abnormal posture Deformity Functional limitation

11. Clinical features Spasticity is recognised clinically by The characteristic pattern of involvement of certain muscle groups. The increase responsiveness of muscle to strecth Markedly increase tendon reflex

12. Spasticity predominately affects the antigravity muscles i.e The flexors of the arms and The extensors of the legs. As a result the arms tend to assume a flexed and a pronated posture while the legs are usually held in extended and adducted

13. In spasticy resistance increase with increase in amplitude and velocity of strecth .thus the larger and quicker the stretch ,the stronger the resistance of the spastic muscle. Initially stretch produces high resistance followed by a sudden inhibition or letting go of resistance , followed by a sudden inhibition or letting go of resistance ,termed the clasp knife response.

14. Clonus It is characterized by spasmodic alternation of muscular contraction and relaxation in response to sustained stretch of a spastic muscle. Clonus is most commonly seen in the ankle and characterised by excess or inappropriate motor activity.

15. Pathophysiology of spasticity

16. Rigidity Clinically defined as increased resistance to stretch and the inability to achieve complete muscle relaxation The stiffness or involuntary muscle contraction is maintained throughout the ROM ,relatively independent of velocity of stretch and for as long as the stretch is maintained.

17. Factors contribute to rigidity Inability of the patient to relax and completely eliminate activity in the muscles Increase stiffness due to altered viscoelastic properties of the muscles. Abnormal co- activition of agonist and antagonist muscle group. Increase stretch reflex.

18. Decerebrate and decorticate rigidity are abnormal posture associated with coma. The decerebrate and decorticate posturing would be more appropriate

19. Opisthamus Strong and sustained contraction of the extensor muscles of the neck and trunk The patient assumes a rigid hyperextended posture.

20. Gegenhalten rigidity Elderly patient Unable to relax limb during examination Appears to Resist voluntarily but unable to prevent such movement and therefore not voluntory resistance Caused by damage to frontal lobe and also associated with CVA and Neurodegenerative condition

21. Alpha rigidity Increase in tone of both flexors and extensors Tendon reflex absent or reduced Increase motor unit excitability

22. Clinical feature Increased resistance to relatively slowly imposed passive movement Present in both flexor and extensor. Rigidity originating from basal ganglia lesions is characterised by resistance to passive movement involving both agonist and antagonist muscles. Stiffness ,inflexibility and functional limitation Cardinal feature of extrapyramidal syndrome

23. Hypotonia Hypotonia or flaccidity are the terms used to define decreased or absent muscular. Resistance to passive movement is diminished,stretch reflexes are absent and limbs are easily moved . Hyperextensibility of joints is common LMN lesions affecting the anterior horn cell or peripheral nerve produce decreased or absent tone along with associated symptoms of paralysis,muscle fasciculations and fibrillation….

24. … with denervation and neurogenic atrophy ,decreased tone is also associated with UMN lesion affecting the cerebellum or pyramidal tracts . These may be temporary states ,termed spinal shock or cerebral shock,depending on the location of the lesion. The duration of the CNS depression that occurs with shock is highly variable lasting days or weeks.

25. SUMMARY

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