What is a pain stimulus for one person does not automatically have to be so for another. A particularly pronounced pain sensation does not automatically have disease value. If, on the other hand, there is hardly any pain sensation, hypalgesia may be present. In this case, it is a disorder of the nociceptors.
What is hypalgesia?
The first instance of human pain sensation is sensory cells of the skin sense. These sensory cells correspond to nociceptors. These are free nerve endings of sensitive neurons of the spinal cord. Nociceptors are located in all pain-sensitive body tissues and provide feedback to the central nervous system about tissue damage. In addition to surface pain on the skin, nociceptors report deep pain of muscles and bones as well as pain in organs. The sensitivity of the receptors is related to the pain threshold. Nociception is to some extent individual. Therefore, an increased or decreased sensation of pain does not automatically have to be related to a disease. Above a certain threshold, however, abnormal pain perception is associated with disease value. One such phenomenon is hypalgesia. In this phenomenon, the sensation of pain is greatly reduced. Allodynia, in which the sensation of pain is exaggerated due to over-reactive nociceptors, is to be distinguished from this. Both phenomena are referred to as sensitivity disorders and, as such, are often associated with neurogenic diseases.
Causes
The cause of hypalgesia and thus reduced pain sensation is often neurologic disease. If the sensation of pain is reduced because of nerve damage in the peripheral nervous system, the nociceptors do respond to pain stimuli by forming an action potential. However, due to a peripherally impaired pathway, the excitation does not reach the central nervous system and thus does not pass into consciousness. Peripheral nerve damage includes polyneuropathies, in which nerves of the peripheral nervous system demyelinate. Myelin insulates nerve conductions, protecting them from loss of excitation. In polyneuropathies, myelin around peripheral nerves is degraded. Primary causes of this phenomenon may be infections, metabolic disorders such as diabetes mellitus, previous trauma, inflammation, poisoning, or malnutrition. If hypalgesia is based on damage to the central nervous system, this damage may be inflammation, tumors, or degenerative phenomena. Inflammations in the spinal cord or the brain areas for pain processing, for example, are often caused by the autoimmune diseaseMultiple Sclerosis. Spinal cord infarctions, strokes or herniated discs can also cause centrally mediated sensory disturbances. There does not necessarily have to be a physical cause. Psychoneuroses can also cause hypalgesia.
Symptoms, complaints, and signs
A patient with hypalgesia does not perceive pain stimuli as painful up to an unusually high intensity. With this manifestation, the affected person suffers from the symptom of a superordinate disease. All further symptoms thus depend on the primary cause of the sensory disturbance. If the disturbed pain sensation is associated with lesions in the brain or spinal cord, for example, the affected person often complains of more or less severe headaches or backaches, especially in the case of inflammations in the central nervous system. Depending on the cause, hypalgesia may be associated with further sensory disturbances in the sense of reduced sensation of other sensory qualities. For example, general temperature sensation or touch sensation may be impaired at the same time. Hypalgesia can also be accompanied by sensory disturbances such as general numbness of certain areas of the body. Contrary to what many people assume, numbness does not automatically have to be associated with hypalgesia and can, for example, exclusively affect the sensation of touch or temperature. If there are no other neurological symptoms besides hypalgesia, psychoneurosis due to a “paralyzing” event is the most likely cause. Hypalgesia in this context may be an expression of psychic insensibility. Often, a psychologically induced loss of pain sensitivity is thus caused by an extreme pain experience.
Diagnosis and course of the disease
The diagnosis of hypalgesia is usually made by the neurologist. During sensitivity tests, the neurologist checks all qualities of the skin sense. Diagnosed hypalgesia should not be taken as an actual diagnosis. The diagnosis does not stand until the primary cause of hypalgesia is identified and thus the sensitivity disorder is traced to a primary disease. For example, centrally mediated hypalgesia is attributed to disease or pathological processes in the central nervous system during the diagnostic process. To classify the cause of hypalgesia, the physician resorts to imaging procedures and nerve conduction tests. If there is no lesion in either the central or peripheral nervous system, the sensory disturbance is a psychosomatic phenomenon.
Complications
Hypalgesia results in significant sensory disturbances in the patient. These disturbances lead to a false or insufficient perception of the sensation of pain. As a rule, hypalgesia causes the affected person to fail to recognize certain complaints and delays treatment of the diseases. As a result, various complaints and complications can develop if various diseases or infections are discovered and treated late. Different areas may become numb or completely paralyzed. In some cases, this results in restricted movement for the patient. It is not uncommon for those affected to suffer from pain in the head and back. This pain can also spread to other regions of the body and cause discomfort there. In some cases, the patient’s sense of temperature is also severely restricted by hypalgesia, so that burns can occur. Treatment of hypalgesia does not lead to further complications. It proceeds with the help of antibiotics or surgical interventions. In some cases, therapies are also necessary to restore the sensitivity of the affected person. Life expectancy is not usually affected by hypalgesia.
When should you see a doctor?
If severe painful stimuli and insensations occur repeatedly that cannot be attributed to any specific cause, hypalgesia may be underlying. A physician must be consulted if the discomfort does not subside on its own or rapidly increases in intensity. If other symptoms, such as sensory disturbances or numbness, occur, it is best to consult a doctor immediately. The same applies to disturbed temperature sensation and even fever. Medical advice is needed at the latest when serious complications develop. For example, pronounced movement restrictions, chronic headaches or back pain, and persistent numbness must be clarified. People suffering from nerve damage are particularly susceptible to the symptoms of hypalgesia. So are people with tumors, degenerative conditions or autoimmune diseases such as multiple sclerosis. Anyone who belongs to these risk groups should consult a doctor immediately with the complaints mentioned. The right contact person is the family doctor or a neurologist. If the symptoms are severe, the emergency physician should be called or the patient must go to a hospital immediately.
Treatment and therapy
Treatment of hypalgesia depends on the primary cause. For example, in diabetic polyneuropathy, optimal glycemic control of the patient takes a central value in treatment. Infectious polyneuropathy requires drug treatment of the causative infection, such as the administration of antibiotics. From peripheral nerve damage, patients can often make an approximate full recovery once the cause is removed. With causative lesions in the central nervous system, complete recovery often fails to occur. An exception to this may exist with tumor-related hypalgesia. In this case, removal of the tumor can lead to restoration of pain sensation. With degenerative causes, restoration is not possible. In the case of causally inflammatory lesions of the central nervous system, the inflammation must first be brought under control by the administration of medication. Injuries to the central nervous system leave scars. The affected nerve tissue is thus permanently impaired in its function and cannot fully recover due to the high degree of specialization.However, the functions of the defective tissue can possibly be transferred to the neighboring nerve cells in the course of sensitivity therapy. In psychologically induced hypalgesia, psychotherapeutic care is used to process the triggering event.
Outlook and prognosis
Depending on the type and severity of hypalgesia, persistent symptoms may be added, severely limiting the quality of life. The prognosis is positive for mildly pronounced sensory disturbances. In such cases, drug treatment is often sufficient to reduce the symptoms to such an extent that a normal life is possible. In cases of severe hypalgesia with severe headache and back pain, complete recovery is unlikely. Patients are often impaired throughout their lives and require assistance with daily living later in life. In the worst case, serious diseases are not detected in time as a result of impaired pain perception. Any infections or internal diseases are then sometimes already far advanced and are potentially fatal. If temperature perception is also disturbed, burns and frostbite and the associated consequences can also occur. These considerable limitations often also lead to the development of psychological complaints, which in turn reduce the quality of life. However, life expectancy is not normally reduced by hypalgesia. Nevertheless, early and comprehensive treatment is necessary in any case. Drug therapy, combined with physiotherapy and behavioral therapy, can provide a positive prognosis.
Prevention
Physically induced hypalgesia can be prevented only to the extent that degenerative, infectious, and autoimmunologic diseases, cancers, hypoxia, and trauma to nervous tissue can be prevented: that is, hardly at all. Psychologically induced hypalgesia, on the other hand, can be prevented by processing stressful events.
Follow-up
In the case of hypalgesia, follow-up care focuses on regular consultations with the specialist. The physician will ask the patient about current pain levels and adjust medications as needed. In most cases, this is not necessary, as hypalgesia is usually treatable and will resolve on its own once therapy for the causative condition is complete. Accordingly, progress monitoring only needs to take place monthly and later every six months. If no further insensitivity to pain is detected, visits to the doctor can be discontinued. Because the disease often causes psychological complaints, psychological treatment is advisable following therapy. The same applies if the reduced pain sensation is due to a psychological illness. In this case, the patient should consult a therapist and, if necessary, attend a self-help group. Which measures are appropriate in detail always depends on the intensity of the illness and requires initial consultation with a specialist. In the case of chronic complaints, such as those that can occur with neurological diseases, comprehensive therapeutic support is necessary in any case. The patient must also take medication and have the medication regularly adjusted to the current state of health. Hypalgesia, unlike allodynia, usually has physical causes that need to be identified. Depending on the nature of the condition, this can sometimes take several months or even years.
Here’s what you can do yourself
In the case of hypalgesia, the first step is to determine the causative condition. Depending on which condition triggers the restricted pain sensation, various self-help measures can be taken. If it is a diabetic polyneuropathy, the focus is on adjusting the blood glucose level. The affected person must pay attention to the body’s own signals and possibly also keep a complaints diary in order to quickly achieve an optimal value that no longer causes any complaints. Infectious polyneuropathy must be treated with medication in any case. Natural remedies with antibiotic effect support the medical administration of antibiotics. In the case of degenerative causes, complete restoration of pain sensitivity is not possible. The focus is on reducing the discomfort as much as possible. This can be achieved, for example, through sensitivity therapy and alternative measures such as acupuncture, massages or cold and heat therapy.Since illnesses and injuries in the affected area can only be perceived to a limited extent, regular visits to the doctor are also indicated. In the case of psychologically induced hypalgesia, the affected person should also seek psychotherapeutic care. In conversation with a therapist, the triggering event can be processed, which normally also reduces the complaints.
