Neuralgia

NEURALGIA (from Greek neuron - nerve and algos - pain), a symptom complex characterized by pain that occurs or intensifies in paroxysms and spreads along the trunk of a nerve or its branches. The pain is caused by an irritating process, the localization of which can be quite varied, and accordingly, a number of neuralgias are distinguished: 1) extrafascicular or terminal neuralgias with the localization of irritation in the terminal branches of the nerve; 2) fascicular neuralgias with the localization of irritation in the nerve trunks themselves; 3) ganglionic neuralgias with the localization of irritation in the corresponding ganglia (intervertebral ganglia, Gasserian ganglion, etc.); 4) radicular neuralgias, or radiculalgias, with the localization of irritation in the posterior roots of the spinal cord, in the sensory roots of the cranial nerves; 5) central neuralgias, spinal, brainstem, cerebral, especially thalamic, with the localization of irritation in the corresponding apparatuses; 6) reflex neuralgias, arising through the irradiation of irritation from some visceral organ (see Head's zones). Etiology. Neuropathic predisposition undoubtedly has great significance. Among other general etiological factors, sex and age should be especially noted. Men fall ill significantly more often than women. In childhood, neuralgia is very rare; it predominantly affects the elderly. The tendency toward neuralgia increases significantly during pregnancy, in the postpartum period, during the climacteric period, and in old age. Among the factors directly causing neuralgia, one should name, as in the etiology of neuritis, infectious diseases, exogenous and endogenous intoxications, trauma, and cooling. Of acute infections, neuralgia is most often accompanied by influenza; but they can also be caused by any other infectious disease. An epidemic spread of neuralgia is also possible, especially intercostal (herpes zoster). Of particular interest from a therapeutic point of view is malarial neuralgia, often characterized by an intermittent course with regular intervals. The action of infections is apparently reduced to the action of toxins released by the infectious agent, which directly irritate the peripheral nerves. In general, intoxications occupy a large place in the etiology of neuralgia. Very often, gouty diathesis and arthritism lie at the basis of neuralgia. The toxic origin of neuralgia in diabetes is also undoubted. The influence of alcohol (chronic alcoholism), arsenic, and a whole range of occupational poisons (especially lead, but also copper, mercury, etc.) on the occurrence of neuralgia is well known. Arteriosclerosis (lesion of the vasa nervorum, disruption of the nutrition of nerve trunks) is of great importance in its occurrence. Neuralgia in cachectic states, in anemias, and in old age, where the influences of both arteriosclerosis, cachexia, and endogenous intoxications combine, should be explained by nutritional disturbances and, in part, by endogenous intoxication. Cold-related factors and local strain are of great importance. Neuralgia is very often connected to occupational hazards because of this; the frequency of ischialgia in foundry workers, in train drivers (the simultaneous effect of constant standing and sharp changes in ambient temperature), the frequency of neuralgia (neuralgia cervico-brachialis) in typists, etc., is well known. Furthermore, one should note the role of traumatizing factors, and among them, especially irregularities of the skeletal system (spina bifida, spondyloarthritis, spondylosis, cervical ribs, sacralization of L_v, etc.), due to which the corresponding nerve trunks or roots are directly irritated. Finally, one should keep in mind the possibility of the reflex occurrence of neuralgia, especially via a reflex from internal organs. It is very essential when discussing the question of the origin of neuralgia in each individual case not to lose sight of the fact that, for the most part, the occurrence of the disease is caused not by one single cause, but by a whole series of competing causes. The presence of bone changes (spina bifida, etc.) creates unfavorable conditions for the position of the nerve trunk. However, for a long time, this unfavorable position may not manifest itself in any way, and only the addition of a new unfavorable factor (overexertion, cooling, infection, intoxication, deterioration of nutrition), and sometimes a series of these factors, causes the occurrence of neuralgia. Identifying the significance of each of these factors in each individual case represents a task of great practical importance, since its resolution is a necessary prerequisite for the application of correct therapeutic and preventive measures. Pathological anatomy and pathogenesis. In relatively recent times, neuralgia was contrasted with neuritis as a disease without an anatomical substrate. Even at the present time, there is an attempt to separate symptomatic neuritis from neuralgia (see below), assuming, however, that here, as there, it is a matter of an organic process and the difference is mainly quantitative. Pathological-anatomical observations are generally quite scarce and relate mainly to surgical, rather than autopsy material. The changes, where they were observed at all, amounted to edema of the nerve trunk, its redness, adhesion to surrounding tissues, especially to the sheath, proliferation of the peri- and endoneurium, dilation of the peri- and endoneural spaces, and dilation of blood vessels—in a word, changes characteristic of interstitial neuritis. However, there are undoubtedly cases where anatomical examination does not reveal pathological changes in the nerve trunks. The pathogenesis of neuralgia in such cases is not fully clarified; apparently, it is a matter of nutritional disturbances in the nerve trunks, in their sheaths, in the nervi nervorum, insufficient to cause persistent anatomical changes, but quite sufficient to create irritation of the nerve trunk and result in neuralgic phenomena. Reflex neuralgias occupy a special position in terms of pathogenesis. Symptomatology and course. The main, often the only symptom of neuralgia is pain spreading along the course of the corresponding nerve trunk, which is very characteristic of them and is one of the most important distinguishing features from pain of other origins (psychalgia, myositic and joint pain, etc.). The character of the pain can be different; for the most part, they are sharp, shooting, tearing, combined with a sensation of burning. It is characteristic for them to appear in paroxysms, developing either spontaneously, without any visible reason, or under the influence of movements, change of position, or light touch. Often, the appearance of paroxysms reveals a regular character: they occur at a specific time, at specific hours, only at night (so-called nyctalgia, neuralgia nocturna, hypnalgia, which is caused by sleep), etc. Malarial neuralgia is characterized by a particularly typical intermittent course, but periodicity can also be observed in other neuralgias, for example, in post-influenza neuralgia. In the intervals between paroxysms, the patient either feels no pain at all or, more often (especially in prolonged cases), only slight dull pain. And during the paroxysm itself, the pain is not entirely uniform, but for the most part, comes in jolts. The duration of each paroxysm is very different: from a few minutes to several hours. Paroxysms are often accompanied by vasomotor, secretory, and motor phenomena: pallor or redness of the skin, local hyperhidrosis, lacrimation and salivation (trigeminal neuralgia), tic-like twitching in the area of facial muscles (tic douloureux), or the development of spasm in them. In rare cases, local edema develops, sometimes erythema, local persistent dilation of vessels. The close connection of herpes zoster (see) with neuralgia is well known. The most frequent neuralgia is neuralgia of the sciatic nerve, sciatica (see). Next, one should name trigeminal neuralgia, or prosopalgia (see Trigeminus nerve), one of the most persistent and agonizing neuralgias; intercostal neuralgia; neuralgia of the cervicobrachial plexus, which is often an occupational disease (porters of heavy loads, typists, etc.); occipital neuralgia, spreading along the course of the greater occipital nerve, less often also along the course of the lesser occipital nerve and the nervus auricularis magnus, more often bilateral than unilateral, neuralgia occipito-cervicalis; notalgia (pain in the back); brachialgia, or neuralgia brachialis (neuralgia of the brachial plexus); femoral neuralgia; talalgia (pain in the heel); visceral neuralgias (e.g., mesogastralgia, neuralgic pain in the abdominal region); agonizing and persistent amputation neuralgia (in the area of the stump in amputation neuroma); panalgia, characterized by pain throughout the body (for the most part of hysterical origin). As a rule, in neuralgia, tenderness to pressure on nerve trunks is observed at special points characteristic of each neuralgia, so-called Valleix points. These points correspond to the place where nerve trunks or their branches exit from bone canals or, in general, to those places where the nerve trunk can be directly pressed against a bone. Tenderness of Valleix points usually exists not only during paroxysms but also during intervals, and therein lies their great diagnostic value.

Often neuralgia is accompanied by hyperesthesia of the skin in the area innervated by the corresponding nerve. Frequently, at the height of an attack, irradiation of pain is observed into nearby areas (into the ramus infraorbitalis in neuralgia of the rami supraorbitalis) or even into distant areas (into the intercostal nerve in prosopalgia, etc.). A severe attack can lead, via reflex, to general symptoms, to a slowing of the pulse, to vomiting, etc. Prolonged and severe neuralgia can entail a disturbance of the general condition, lead to the development of cachexia, disturbances on the part of the psyche, and in exceptional cases, even to the development of pronounced psychoses (neuralgische Vesanie of old authors). The course of neuralgia is highly variable and changes from case to case. For the most part, beginning acutely, neuralgia subsequently takes on a protracted course, sometimes for whole years. Attacks of pain can, at the same time, recur just as frequently as at the beginning of the disease. In other cases, the free intervals lengthen, and sometimes painful seizures appear only as rare episodes. In some cases, neuralgia takes a favorable course altogether, lasts for several weeks, sometimes even days, and then disappears without a trace. It is necessary, however, to remember that neuralgia is highly prone to recurrences, and therefore the prognosis in these cases should be made with a certain amount of caution. The diagnosis of neuralgia is far from always an easy task. As already indicated, the distinction between neuralgia and neuritis can often be made only very conditionally, since mild forms of neuritis often proceed under the guise of neuralgia. As distinctive signs speaking definitely in favor of neuritis, one should consider the addition to the pain, in the subsequent course, of atrophic and paretic phenomena, weakening or extinction of reflexes, the emergence of anesthesias or hypesthesias, i.e., deficiency phenomena, which should not be present in true neuralgia, since the latter represents a manifestation of a purely irritative, and not a destructive, process. Further characteristic of neuralgia is tenderness to pressure of Valleix's points, whereas in neuritis, there is tenderness of the entire nerve trunk or a large part of it. The distinction of neuralgia from vasomotor local neuroses of the extremities (acroneuroses) does not present great difficulties. True, the latter (acromelalgia or erythromelalgia, Raynaud's disease) are characterized primarily by severe pain, however, the pain in them is localized not along the course of the nerve trunk, but in the distal parts of the extremities; there is an absence of tenderness of Valleix's points, and vasomotor and trophic disorders are sharply expressed. Intercostal neuralgia may give rise to the thought of the presence of attacks of angina pectoris. The distinctive signs are the absence in angina pectoris of typical painful points, and the specific sensation of compression of the chest and the proximity of death. One must not, however, forget that angina pectoris can sometimes be a causal factor in the emergence of intercostal neuralgia, so that the presence of the signs of the latter is not yet absolute proof of the absence of attacks of angina pectoris in a given case. Frequently, neuralgia appears as an initial symptom of some organic lesion of the central nervous system; inflammatory conditions in the area of the roots and meninges, neoplasms of the spinal cord, specific meningomyelitis, tabes, etc., especially debut in this way, which obliges one to subject every case of neuralgia to the most complete and detailed examination possible. Significant difficulties can be presented by the differential diagnosis of neuralgia from psychalgia or pseudoneuralgia, i.e., from pain depending on autosuggestion or conditioned by other psychogenic factors. Of great importance here is the distribution of pain in cases of true neuralgia along the course of the nerve trunk, while, for example, in hysterical topalgia, pain is observed in a limited area without connection to any specific nerve trunk, etc. Also essentially important is the presence of Valleix's points, and in ischialgia, the presence of Lasègue's sign. The same signs have significance for distinguishing neuralgia from simulated pain. The prognosis is generally quite favorable if one is dealing with fresh cases, with neuralgia that has arisen as a result of acute infections, especially in young age, with a good general condition. The prognosis is significantly worse in toxic neuralgia, in old age, in general cachexia, in neuropathic predisposition, and in bone changes that sustain the disease. The prognosis is significantly worsened by the circumstance that neuralgia is highly prone to recurrences. Treatment and preventive measures. Treatment is to a significant extent determined by the etiology of neuralgia in each individual case. Thus, malarial neuralgia must be treated systematically with quinine and arsenic; neuralgia in arthritis with atophan, diet, and alkalis; neuralgia in diabetes with a special diet; neuralgia in anemia and cachexia with treatment of these latter and the causes inducing them; neuralgia in preceding syphilis with the indispensable application of specific therapy, even if the connection with syphilis is not entirely clear; occupational neuralgia with corresponding preventive measures (removal from harmful production, etc.). But general therapy also has great significance, especially physiotherapeutic measures. Here, first of all, one should name thermal procedures: treatment with blue light, applicable even in a home setting, treatment with light-electric baths, treatment with diathermy, and especially treatment at health resorts (Odessa, Lipetsk, Slavyansk, Yevpatoria, Pyatigorsk, etc.) with mud and brine baths, which often yield an excellent therapeutic effect even in chronic cases. Next follows electrotherapy: treatment with direct current, faradic current, and especially with cataphoresis [ionogalvanization (aconitine, antipyrine, cocaine, chloroform)]. In some cases, massage is useful, especially in cases of ischialgia. Good results in many cases are given by counter-irritant therapy—the application of Empl. vesicatorium, especially in the form of a long strip along the tract of the nerve, or cauterization with a Paquelin apparatus. From medicinal therapy, besides the special agents mentioned above, recourse is had to salicylates (Natr. salicyl., Antipyrin, Aspirin, Pyramidonum, and especially mixtures of these agents). The use of morphine or pantopon is permissible only in the most exceptional cases in view of the danger of habituation to these preparations. Pain-soothing ointments with chloroform, belladonna, henbane oil, opium, cocaine, veratrine, mesotan, etc., are often used. Apparently, good results are often obtained from the use of Vaccineurin proposed by Dölken (3 times a week from 0.02 to 0.1 cm³ with a gradual increase in dose), as well as other vaccines and protein therapy. In those cases where the indicated measures do not lead to the goal, one has to turn to surgical treatment. This includes, first of all, perineural injections of osmic or carbolic acid and treatment according to Schlosser and Lange. Schlosser's method is the deep injection of 1.5–4.0 cm³ of 80% alcohol into the nerve (into the area of the foramen rotundum or foramen ovale in prosopalgia, etc.). A later modification, often yielding good results, is the injection of alcohol into the peripheral branches (e.g., into the r. supraorbitalis, etc.). Lange's method consists of the perineural injection of 60–80 cm³ of a 1% solution of β-eucaine or tropacocaine. In stubborn cases of lumboischialgia (radiculalgia), recourse is sometimes had to rachicocainization, i.e., the injection of cocaine into the subarachnoid space, or to epidural injections. Finally, operative intervention may also be required: transection of the nerve trunk, nerve extraction (exeresis), extirpation of the Gasserian ganglion, transection of the trigeminal nerve root between the Gasserian ganglion and the pons Varolii, and transection of the posterior roots of the spinal cord. Preventive measures in relation to neuralgia come down to organizational measures in production that eliminate or weaken the corresponding harmful influences of occupational intoxications (Pb, Hg, Cu, etc.), sharp changes in temperature, etc. In those cases where neuralgia is already present, a change of profession is of great importance, which, it is true, often presents great difficulties.