Neuralgia: The Symptoms, Causes and Risk Factors

Neuralgia is defined as a condition of a sudden and heavy attacks of pain that follows the path of a nerve or nerves as a result of a change in neurological structure or function due to irritation or damage to the nerves without stimulating pain receptor (nociceptor) cells. the disease affects about 2%–3% of the population.

I. Symptoms
1. In the study to evaluate the symptoms of neuralgia effect on the patient with postherpetic neuralgia (PHN), scientists at Policy Analysis Inc, showed that only about one half had taken prescription medication for shingles pain during the prior week; dosages were typically low. Mean average, worst, least, and current pain caused by shingles (0- to 10-point scale) was 4.6 (+/-2.1), 6.0 (+/-2.4), 2.9 (+/-2.3), and 4.0 (+/-2.7), respectively. Mean pain interference with general activity, mood, relations with other people, sleep, and enjoyment of life (0- to 10-point scale) was 3.7 (+/-3.1), 4.3 (+/-2.9), 3.0 (+/-2.8), 3.8 (+/-2.9), and 4.5 (+/-3.1), respectively. The mean EQ-5D health index score was 0.61; respondents rated their overall health as 65.7 (+/-21.1) on a 100-point scale. PHN causes substantial pain, dysfunction, and poor health-related quality of life in older persons, many of whom might be suboptimally treated(a).

2. Mechanical allodynia and cold hyperalgesia(13)

II. Causes and Risk factors
A. Causes
1. Smoke, smell, dust and cold air
Dr. Moritsch E and  Mitschke H. in the study of Surgical elimination of endonasal triggerpoints of a trigeminal neuralgia caused by cauterization showed that a severe injury by fluid Ammonia of the nasal mucosa resulted with a strong irritation of the 1. and 2. branch of the trigeminus nerve with sudden and heavy attacks of pain. The region below the head of the right inferior nasal concha was detected as a trigger zone for smoke, smell, dust and cold air. Local anaesthesia stopped the attacks(1)

2. Chronic renal insufficiency
Chronic renal insufficiency, the slow loss of kidney function over time, are often accompanied by neuralgia. Peripheral nerve disorders distort or interrupt the messages between the brain and the rest of the body as a result of kidney damage of that can led neuralgia, as a result of waste accumulation in the blood.

3. Infection
Certain infections can lead to neuralgia
a. Facial herpes zoster infection
Occipital neuralgia is a pain syndrome which may usually be induced by spasms of the cervical muscles or trauma to the greater or lesser occipital nerves. Scientist(s) at the Kyoto University in the study of a 74-year-old male experienced sudden-onset severe headache in the occipital area showed that the pain was localized to the distribution of the right side of the greater occipital nerve, and palpation of the right greater occipital nerve reproduces the pain. He was diagnosed with occipital neuralgia according to ICHD-II criteria. A few days later, the occipital pain was followed by reddening of the skin and the appearance, of varying size, of vesicles on the right side of his face (the maxillary nerve and the mandibular nerve region). This was diagnosed as herpes zoster.(2)

b. Human immunodeficiency virus (HIV)
Dr. Louis E and the team at the Hôpital Sainte-Anne, in the study of Bilateral amyotrophic neuralgia (Parsonage Turner syndrome) with HIV seroconversion reported that a unusual case of neuralgic amyotrophy (NA) occurring during the seroconversion stage of an HIV infection. Combined with previously published cases, our observation suggests that NA associated with HIV could belong to the group of early multiplex mononeuritis. Neurologists should be aware of HIV infection when managing a patient with NA(3).

c. Lyme disease
In the report of a 55-year-old woman developed severe unilateral headaches, periocular numbness, and Horner syndrome after presenting with symptoms consistent with Lyme disease was constituted a diagnosis of Raeder paratrigeminal neuralgia(4)

d. Etc.

4. Diabetes
Diabetes are associated with  femoral neuralgia, as a result of excessive sugar levels in the blood stream. Dr. Simmat G. and the team in the study of A retrospective study allowed us to work out an original method for an essentially clinical approach of the correlation between femoral neuropathy and diabetes mellitus.(5)

5. Surgery
Certain surgery such as herniorrhaphy, appendectomy, nephrectomy, gynecological surgery, removal of bone from the inner table of the iliac crest, may increase the risk of neuralagia. In the frequent cases attributable to previous surgery the retroperitoneal resection of the nerves is advocated instead of a local revision, which is usually unsuccessful due to the impossibility of finding and restoring the fine nerves in a dense scar.(6)

6. Hypothyroidism
In the study of Painful neuropathy in subclinical hypothyroidism, Dr. Penza P, and the team at National Neurological Institute Carlo Besta showed that Subclinical hypothyroidism is a possible cause of sensory neuropathy and hormone replacement therapy can prompt nerve regeneration(7).

7. Multiple sclerosis 
Many patients with multiple sclerosis (MS) are siad to be associated with trigeminal neuralgia (TN). researchers at Università La Sapienza found that the most likely cause of MS-related TN is a pontine plaque damaging the primary afferents. Nevertheless, in some patients a neurovascular contact may act as a concurring mechanism. The other sensory disturbances, including ongoing pain and dysaesthesia, may arise from damage to the second-order neurons in the spinal trigeminal complex.(8)

8. Porphyria
Porphyrias represent a group of inherited or acquired disorders that involve enzymes that participate in heme synthesis. Acute manifestations affect the nervous system resulting in abdominal pain, vomiting, acute neuropathy, seizures, and mental disorders(9)

9. Brian and spiral tumors
In a report of Trigeminal neuralgia (TN) is often secondary to an underlying structural cause, frequently compression of the fifth nerve root by an ectatic artery. This unusual set of circumstances is an example of “action at a distance” in the nervous system, and reminds clinicians to think broadly about the various pathophysiologic mechanisms that can potentially underlie common disorders(10). Other researchers suggested Trigeminal neuralgia (TN) is occasionally caused by cerebellopontine angle (CPA) tumors. Among 243 patients presenting with TN who had been operated on in our institute, 25 (10.3%) were caused by CPA tumors, which consisted of 11 epidermoid, 9 acoustic tumors, and 5 meningiomas. Cases with TN caused by tumors were clinically investigated in comparison with those of idiopathic TN.(11)

10. Hypertension
In the study of A total of 138,492 persons with at least 2 ambulatory visits with the principal diagnosis of hypertension in 2001 were enrolled in the hypertension group. The nonhypertension group consisted of 276,984 age- and sex-matched, randomly sampled subjects without hypertension, showed that a significantly increased risk of developing TN after hypertension. Further studies are needed to elucidate the underlying mechanism of the association between hypertension and TN(12). 

11. Other causes
Neuropathic pain refers to pain that originates from pathology of the nervous system. Common causes of neuropathic pain are diabetes mellitus, reactivation of herpes zoster, nerve compression or radiculopathy, alcohol, chemotherapy or abuse of some drugs, and trigeminal neuralgia(13).

12. Etc.

B. Risk factors
1. Age, sex and migraine
In the study conducted by  University of Rochester School of Medicine and Dentistry showed that Univariate and multivariate analyses indicated that older age, female sex, presence of a prodrome, greater rash severity, and greater acute pain severity made independent contributions to identifying which patients developed PHN. Patients with subacute herpetic neuralgia who did not develop PHN were significantly younger and had less severe acute pain than postherpetic neuralgia (PHN) patients but were significantly more likely to have severe and widespread rash than patients without persisting pain.(14). Other indicated that indicate that patients with migraine(M) should also be screened for symptoms of occipital neuralgia (ON), as there may be similarities in presentation. The clinical implications of distinguishing ON + M and isolated ON include differences in treatment regimen, avoidance of inappropriate use of medical resources, and differences in long-term outcomes.(15)

2. Immunity
In a report of 821 cases of herpes zoster that met all eligibility criteria, indicated that the prevalence of postherpetic neuralgia (PHN) more than 30 days after onset of zoster was 8.0% (95% confidence interval [CI], 6.3%-10.1%) and 4.5% (95% CI, 3.2%-6.2%) after 60 days. Compared with patients younger than 50 years, individuals aged 50 years or older had a 14.7-fold higher prevalence (95% CI, 6.8-32.0) 30 days and a 27.4-fold higher prevalence (95% CI, 8.8-85.4) 60 days after developing zoster. Prodromal sensory symptoms and certain conditions associated with compromised immunity were also associated with PHN. Systemic corticosteroids before zoster and treatment of zoster with acyclovir or corticosteroids did not significantly affect the prevalence of PHN.(16)

3. Nutrient deficiency
In the study to compare the nutritional status of PHN patients with that of healthy controls, and then to identify risk factors for PHN using multivariate multiple logistic regressions, conducted by Chi Mei Medical Center,, Dr. Chen JY and the medical team showed that lower concentrations of circulating nutrients, namely vitamin C, ionised Ca or Zn, are probably a risk factor in Taiwanese patients with PHN.(17)

4. Etc.

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