Diagnosis and differentiation of spastic hypertonia

If muscle weakness is caused by a lesion in the pyramidal system, it generally manifests as spastic increased muscle tone. When the patient moves, he or she may not be able to open the range of motion normally, and his or her muscles may become stiff and trembling. Clinically, the diagnosis of spastic hypertonia may be confused with diseases such as myotonia congenita and tetany, and should be carefully differentiated.

Damage to the central nervous system due to various reasons can cause increased spastic muscle tone. Spastic hypertonia is associated with damage to the pyramidal tract, and spinal reflexes are facilitated. Pyramidal system lesions manifest as spastic increased muscle tone, which is characterized by selective increase in muscle tone. The upper limbs are mainly affected by the adductors, flexors and pronators, while the lower limbs are mainly affected by the extensors. The tone of the flexors of the upper limbs and the extensors of the lower limbs is significantly increased. The resistance of the joints in passive movement is greater at the beginning and becomes smaller at the end, which is the so-called jackknife-like increase in muscle tone. Spastic hypertonia has nothing to do with "spasm," which simply refers to an involuntary muscle contraction.

Diagnosis of spastic hypertonia

Muscle tension measurement: Young children often undergo the following tests:

① Hardness: When muscle tension increases, muscle hardness increases, and passive movement causes a feeling of tightness and hardness. When muscle tone is low, the muscles feel soft to the touch and there is no feeling of resistance during passive movement.

② Swinging degree: Fix the proximal end of the limb, make the distal joint and limb swing, and observe the swing amplitude. When the muscle tension increases, the swinging degree is small, and when the muscle tension is low, there is no resistance and the swinging degree is large.

③Joint extension: observe the extension and flexion angles when the joints are passively extended and flexed. When muscle tone is high, joint flexion and extension are limited, while when muscle tone is low, joint flexion and extension are excessive.

Older children can also use the modified Ashworth spasticity rating method.

Differential diagnosis of spastic hypertonia

The diagnosis of spastic hypertonia should be differentiated from the following symptoms:

1. Congenital paramyotonia: also known as Eulenberg disease. This disease only causes increased muscle tone during exercise, while muscle tone is normal when at rest. The disease causes increased muscle tone and muscle rigidity at the beginning of exercise, which returns to normal after repeated exercise. The muscles feel peculiarly tough and rubbery when palpated, which becomes more obvious when the muscles contract rigidly after mechanical stimulation.

2. Stiffman syndrome: an epileptic spasm of unknown cause. The muscle tension of the neck muscles, trunk, spine, and abdominal muscles increases significantly, causing pain when stimulated by external stimuli. Percussion, sound, light, and mental stress can induce and aggravate the condition, usually starting from the proximal limbs and spreading toward the body, with normal muscle strength and tendon reflexes. The stiffness disappears during sleep.

3. Increased myotonic tension: The resistance encountered by patients during passive limb movement is generally smaller than that of spastic patients, but it has nothing to do with the length of the muscle at the time, that is, the contraction shape, and there is no difference between the extensors and flexors. Regardless of the speed, amplitude, or direction of the movement, the same resistance is encountered. This increase in muscle tone is called lead pipe rigidity. If it is accompanied by tremor and causes alternating loose and tight changes, it is called gear rigidity.

4. Tetany: Low blood calcium is the main cause of this disease. Increased muscle tone is mainly seen in the distal limbs and may occasionally spread to the trunk.