Anaesthesia: causes, treatment and associated phenomena
When a nerve is subjected to physical pressure (such as when we fall asleep with our head on one arm, for example), abnormal sensations such as tingling or numbness are common. This phenomenon is known as paresthesia, and sometimes has a chronic and pathological character .
In this article we will describe the causes and treatment of chronic paresthesia. We will also describe in a synthetic way other similar sensory alterations, many of them characterized by the appearance of pain, unlike paresthesia.
What is paresthesia?
Paresthesia is a phenomenon that consists of the appearance of stinging, tingling, itching, numbness or burning sensations in different parts of the body . It is more common to occur in the arms, hands, legs and feet, although it does not always occur in these areas. It is usually not associated with symptoms of pain.
The term “paresthesia” comes from the Greek words “aisthesia”, which means “feeling”, and “para”, which can be translated as “abnormal”. The word began to be used regularly in the 19th century, although some earlier references can be found in classical Greek literature.
Experiences of paresthesia are relatively common in the general population, so they do not always merit consideration as a pathology or disorder. For example, it is common for such sensations to appear when a limb is numbed by sustained pressure from a nerve , as can happen when crossing the legs.
Cases of chronic paresthesia, on the other hand, are considered medical problems. This type of paresthesia occurs as a consequence of disorders affecting the central nervous system, as well as severe lesions of the peripheral nerves; when this happens it is common for paresthesia to have a painful component.
Non-pathological, transient paresthesia occurs when a nerve is under pressure and disappears soon after the pressure is interrupted. In contrast, chronic paresthesia is a sign of injury to the central or peripheral nervous system.
Transient paresthesia is also related to hyperventilation , including that which occurs in the context of panic attacks, and to infection by the herpes virus. In most cases, however, these experiences are due to unnatural body postures.
Alterations affecting the central nervous system and associated with the appearance of chronic paresthesia include multiple sclerosis, encephalitis, transverse myelitis and ischemic strokes. Tumors that press on certain regions of the brain or spinal cord can also cause this type of paresthesia.
Peripheral nerve compression syndromes are also common causes of chronic paresthesia accompanied by painful sensations. Among this group of alterations, the carpal tunnel syndrome should be highlighted, in which the median nerve is compressed inside the carpal tunnel, a group of bones in the wrist.
Other common causes of paraesthesia include diabetes, rheumatoid arthritis, circulatory problems (for example in cases of atherosclerosis), malnutrition, metabolic disorders such as diabetes and hypothyroidism, systemic lupus erythematosus, alcohol abuse and benzodiazepine withdrawal.
Treatment of this disorder
The treatment of chronic paresthesia is fundamentally aimed at correcting the ultimate causes of the alteration , which is also usually accompanied by other physical and cognitive symptoms of greater significance when it affects the central nervous system. Cases of transitory paresthesia do not require any type of intervention since they are normal phenomena.
Depending on the underlying disorder, one or the other drug will be used. Some of the most commonly used include antiviral drugs, anticonvulsants, the corticosteroid prednisone or intravenous injection of gamma globulin.
In addition, topical medications such as lidocaine are sometimes prescribed to reduce the sensations of paresthesia when they are uncomfortable or painful in themselves. Of course, this type of treatment only relieves the symptoms temporarily, but it may be necessary in cases where the cause cannot be eliminated.
Associated sensory phenomena
There are different sensory phenomena similar to paresthesia . Dysesthesia, hyperesthesia, hyperalgesia and allodynia, among others, are abnormal sensations that are produced as a consequence of certain types of stimulation.
The term “dysesthesia” is used to refer to the appearance of abnormal sensations that are unpleasant; in other words, it is a painful or annoying variant of paresthesia.
We call hyperesthesia increased pain sensitivity, i.e. a lowering of the pain threshold. This phenomenon includes allodynia and hyperalgesia.
Hyperalgesia is the increased perception of pain in the presence of painful stimuli. The source of the sensation and the sensation occur in the same sensory mode (e.g. a puncture causes mechanical pain).
Allodynia is the appearance of pain sensations in response to objectively non-painful stimuli. The sensory modality of the stimulus and sensation need not be equivalent.