Hypertonia - Causes and Symptoms

Definition

Hypertonia is a pathological increase in muscle tone, easily visible or recognizable by touch. This sign manifests itself as a stiffening that makes passive stretching of the muscles difficult.

Hypertonia is also found in resting conditions and can also be translated into the inappropriate activity of antagonist muscles (extensors and flexors) and in the inability to fractionate the execution of a movement.

This manifestation can be located in a specific anatomical district or generalized to the structures of a system or apparatus.

Hypertonia can be of two types:

Pyramidal : arises in the presence of a lesion of the pyramidal pathway (bundle of nerve fibers responsible for voluntary movements), therefore it can be found in the context of various pathological conditions, such as amyotrophic lateral sclerosis (ALS), syringomyelia and spinal cord compressions. The pyramidal hypertonia affects the flexor muscles of the upper limbs and the extensors of the lower limbs: if the doctor tries to move a patient's limb, a resistance gradually builds up, until suddenly ceasing as soon as the part is released ( spastic rigidity with the "jack knife" phenomenon). When the muscular hypertonicity is particularly accentuated, we speak of spasticity.
Extrapyramidal : this form of hypertonia, also known as plastic stiffness, is due to a malfunction of the extrapyramidal system (motor nerve pathway which usually depends on muscle tone and postural control of the body). Extrapyramidal hypertonia affects both the flexor and extensor muscles, so the resistance opposed to passive mobilization is exercised with a constant force and no return of the stretched segment to the starting position is observed. Plastic hypertonia is typically found in Parkinson's disease.