Rigor is a stiffness of the muscles that is subject to control by the central nervous system and results from simultaneous activation of muscles and their counterparts. Rigor is the symptom of extrapyramidal or pyramidal lesions in the CNS and thus may be associated with Parkinson’s disease, for example. Therapy consists primarily of physical and occupational therapy.
What is rigor?
Muscles have a basic tension, also known as resting tone. Thus, at rest, skeletal muscles are neither contracted nor fully relaxed. In a condition called rigor, the basic tension of skeletal muscles is increased. The result is muscle rigidity or stiffness of the muscles. Rigor is based on a centrally controlled and simultaneous activation of individual muscles and their antagonists. As such, the antagonists of individual skeletal muscles are referred to. Muscle activation in rigor thus corresponds to agonist-antagonist co-activation. In addition to a feeling of stiffness, patients with rigor often describe pulling sensations in the affected area. A special form of rigor is the so-called cogwheel phenomenon, in which the muscles of a passively moved extremity give way in a jerky manner. The cogwheel phenomenon refers to disorders in the extrapyramidal system of the central nervous system.
Causes
The causes of all forms of rigor are found in the central nervous system. Muscles have a certain basic tension that is regulated by different areas of the central nervous system. In addition to the pyramidal system, the extrapyramidal system is involved in this regulation. All muscle information for contraction of muscles and muscle groups travels to the target organs via the cerebral cortex-spinal cord pathways. These pathways correspond to the pyramidal pathways, which are grouped together in the pyramidal system. Movement information can also be conducted extrapyramidally, reaching the spinal cord by other means. The pyramidal and extrapyramidal systems interact with each other. In most cases, rigor is preceded by dysfunction in the extrapyramidal system. For example, the cogwheel phenomenon is often based on dopamine deficiency and resulting dysfunction, as seen in Parkinson’s disease. Patients with rigor suffer from the leading symptom of muscle rigidity. In cogwheel phenomenon, this rigor affects exclusively passive movements. Other forms of rigor affect only active movements. The end result of muscle rigidity is impaired movement and, in some cases, coordination problems. One of the earliest signs of rigidity is decreased arm movement when walking. In some cases, pain and discomfort are present in addition to rigidity. The insensations are often due to compression of sensitive nerves in the muscles. In individual cases, the movement disorders can promote a tendency to fall. In some cases, patients develop camptocormia during the course of rigor. This postural anomaly is understood by medicine as an involuntary active forward flexion movement of the trunk area. The cause of this phenomenon is the dyston involuntary contraction of the trunk flexor muscles. This contraction increases specifically when the body is in an upright position, so that the camptocormia usually occurs when the patient is standing. All other symptoms depend on the particular cause of the rigor. In the context of Parkinson’s disease, for example, resting tremor and akinesia are among the most relevant symptoms.
Diseases with this symptom
- Parkinson’s disease
- Multiple sclerosis
Diagnosis and course
The diagnosis on a rigor is made by measuring the resting tonus. For measurement, for example, an EMG can be used, which makes the state of tension objectifiable. In addition, a neurological examination takes place as part of the diagnostic process. In this examination, the rigor is detected in the lying or sitting patient. This detection is particularly successful in the case of the cogwheel phenomenon. The physician passively moves the individual joints and asks the patient to relax the muscles. In rigor or cogwheel phenomenon, the physician feels the waxy rigidity of the muscles in the form of a uniformly tenacious resistance. Unlike spastic phenomena, the resistance does not depend on the speed of movement. If the patient actively moves the limb of the other side, the resistance on the passively moved side increases even more.In the case of cogwheel phenomenon, the rigor is characterized by interruptions during this examination. To identify the primary cause of the rigor, the physician subsequently arranges for imaging procedures, among other things. Prognosis depends on the cause of the rigor.
Complications
Muscle stiffness, or rigor, develops primarily in Parkinson’s disease. Another possible complication of Parkinson’s disease is freezing, in which the affected person freezes in mid-motion. On the contrary, it can also lead to excessive, involuntary movements of the arms and legs or the trunk (hyperkinesia), which increases the risk of injury to the affected person and also to the environment. Furthermore, Parkinson’s patients may experience circulatory disturbances, which can lead to severe dizziness or even unconsciousness, for example, from lying down to standing up. In addition, the affected person may experience weakness of the bladder or rectum, so that he or she becomes incontinent and thus in need of care. In addition, Parkinson’s can lead to depression due to the reduction in quality of life. This can lead to an increase in alcohol and drug consumption, and depressives are also prone to suicidal thoughts. A rare and feared complication of Parkinson’s disease is akinetic crisis. In this, the symptoms worsen and the affected person suffers from total muscle stiffness or even extreme rigor. This can lead to a complete inability to move, which can also affect the speech and respiratory muscles. This can also be accompanied by overheating of the body.
When should you see a doctor?
To get a proper diagnosis, sufferers should see a doctor if they suspect rigor. Self-diagnosis using tests or checklists from the Internet is not sufficient. Usually, patients first consult their primary care physician. If necessary, the family doctor can then issue a referral to a specialist. If the symptom is new, patients suffering from Parkinson’s should also inform their treating specialist about the appearance of the rigor. This is usually a neurologist or psychiatrist. In Germany, however, patients do not necessarily need a referral to see a neurologist. Depending on how good the local medical care situation is, waiting times for an appointment can vary greatly. An appointment with a general practitioner is often quicker and in some cases can already provide an initial assessment of the symptoms. In some cities, there are also specialized outpatient clinics, which are often affiliated with a larger clinic. Some of these specialized treatment centers also make appointments for diagnosis and treatment of suspected Parkinson’s disease. Since rigor is a core symptom of Parkinson’s, a professional diagnosis by a physician is advisable in any case.
Treatment and therapy
Therapy for rigor also depends on the primary cause of the disorder. In any case, however, physical and occupational therapy steps count toward therapy. There can be no causal therapy. All rigor has a central nervous cause and damage to the central nervous system is irreversible to some degree in most cases. Accordingly, occupational therapy and physical therapy are not causal but symptomatic treatments. In therapy forms, the aim is to at least alleviate the rigor or to help the patient manage the symptom. In occupational therapy, for example, the patient learns how to use possible aids so that he or she can get through everyday life independently for as long as possible, even with severe rigor. Above all, everyday movements are trained as part of the therapy. In some circumstances, drug treatment steps may also be considered to induce the central nervous system to reduce tonicity.
Outlook and prognosis
In the case of rigor, the prognosis depends largely on the cause of the muscle stiffness. If the rigor is based on Parkinson’s disease, the symptoms can be alleviated by physical and occupational therapy, but damage that has already occurred is irreversible in most cases. There is therefore no prospect of a complete recovery, but further complaints can at least be alleviated by early measures.In the course of the disease, there are usually further symptoms such as an altered gait, a lack of blinking or a decrease in voice volume, which can worsen the prognosis accordingly. Corresponding symptoms continue to develop with the progression of the underlying Parkinson’s disease and increase in intensity and spread until it finally comes to severe paralysis symptoms and later to the death of the affected person. The prospect of a cure is given in the case of rigor resulting from an injury or accident. Then, surgical intervention may be able to restore the original muscle performance without causing secondary symptoms. Initial signs of rigor should be promptly evaluated by a physician because of its severity.
Prevention
Rigor is a symptom of pyramidal or extrapyramidal damage to the central nervous system. Thus, rigor can be prevented only to the extent that lesions in the central nervous system can be prevented. For example, no preventive measures are available against diseases such as multiple sclerosis. For this reason, rigor can never be fully prevented.
What you can do yourself
In the case of rigor, it may be helpful to perform appropriate exercises outside of physical therapy sessions. The prerequisite for this, however, is that the exercises are performed cleanly and consultation with the treating therapist takes place beforehand. Otherwise, there is a risk of worsening symptoms or overloading. Only properly performed exercises are able to improve the daily lives of those affected. Nevertheless, the possibilities to take action on one’s own in case of rigor are rather limited. It is only possible to supplement or support existing treatment approaches. Since rigor is not infrequently accompanied by irreversible damage to the central nervous system, those affected must orient their daily lives according to the disease. This must be accepted. Everyday movements should be carried out despite the restrictions. If assistive devices are used, they must be mastered. In addition, psychological aspects must also be taken into account in the daily lives of those affected. After all, the diagnosis of rigor brings with it numerous changes. Since these are mostly irreversible, the path of acceptance is usually the easiest. It is therefore advisable to come to terms with the new circumstances of life mentally as well. Consultation with a psychologist or psychiatrist can assist in this process.