What is the pathophysiology of the spastic stage of hemiplegic shoulder pain?

Updated: Feb 08, 2019
  • Author: Robert Gould, DO; Chief Editor: Stephen Kishner, MD, MHA  more...
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Answer

As stroke recovery evolves, flaccidity may progress to spasticity. Cailliet explained that normally, the brainstem contains upper extremity (UE) flexor patterns and lower extremity (LE) extensor patterns that are refined and coordinated by the premotor and neocortexes. [10] Following a stroke, the connections that control these reflexes can be interrupted, resulting in the release of these basic patterns and the evolution of spasticity and synergy patterns.

If the neurologic deficits become severe enough, primitive tonic neck reflexes may develop. When such neck reflexes are present, the elbow extends when the head turns toward the affected side, and the elbow flexes when the head turns away. The presence of primitive tonic neck reflexes is considered to be prognostically unfavorable for motor recovery.

The first evidence of UE spasticity is internal rotation of the humerus from the subscapularis and pectoralis major; there is debate as to which muscle contributes more strongly to this pattern. The pattern may then progress into the forearm pronators (ie, pronator quadratus, pronator teres, flexor carpi radialis).

Spastic involvement of the rhomboids leads to scapular depression and downward rotation, while the latissimus dorsi contributes to adduction, extension, and internal rotation of the humerus. Biceps brachii spasticity further depresses the head of the humerus and flexes the elbow.

Teasell noted that as spasticity and synergy evolve, there is a failure of the antagonist muscles to relax when the agonist muscles contract, thus creating cocontraction. [4] For example, during internal rotation, excessive spasticity of the internal rotators of the humerus (ie, subscapularis, pectoralis major, latissimus, teres major) overwhelms the external rotators (ie, supraspinatus, infraspinatus, teres minor).

The muscles causing downward and outward rotation of the scapula, the rhomboids, overwhelm the trapezius and serratus anterior muscles. Spastic, unilateral paraspinal muscles overwhelm those on the contralateral side, causing lateral flexion of the spine toward the affected side.


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