An epidemic in Cuba of optic neuropathy, sensorineural deafness, peripheral sensory neuropathy and dorsolateral myeloneuropathy

Relationship Between Serum Brain-Derived Neurotrophic Factor and Neurotrophin-3 Levels and Hearing Thresholds in Patients With Age-Related Hearing Loss

BACKGROUND

Age-related hearing loss (ARHL) is a general term used to describe the sensorineural type of hearing loss occurring in both ears in older adults. Neurotrophins are the most promising candidates for supporting the auditory nerve by increasing neuronal survival. This study aimed to help elucidate the pathophysiology of ARHL by determining whether any relationship exists between brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) levels in serum samples from patients diagnosed with ARHL.

MATERIALS AND METHOD

Seventy-seven individuals, a study group of 41 patients diagnosed with ARHL, and a control group of 36 participants without hearing loss were evaluated. Serum samples were collected and used to measure serum BDNF and NT-3 levels with the new Nepenthe enzyme-linked immunosorbent assay method.

RESULTS

Median pure-tone average results in the 2000, 4000, and 6000 Hz ranges were 52.5 (44.3-67.3) dB HL in the ARHL group and 13.5 (11.1-17.1) dB HL in the control group. The difference was statistically significant (p = .001). Although NT-3 and BDNF levels were both lower in ARHL patients than in participants without hearing loss, only the BDNF levels were significantly (p = .002) lower. Mean left and right ear word recognition scores were also lower in ARHL patients than in control groups. The ARHL group was further divided into two subgroups based on word recognition scores to evaluate significant differences in BDNF and NT-3 levels. No statistically significant difference was observed in BDNF and NT-3 levels between these subgroups. However, there was a significant difference in word recognition scores.

CONCLUSIONS

Low BDNF levels in the ARHL group suggest that BDNF may play a role in the pathogenesis of ARHL. Patients with low (ARHL1) and high (ARHL2) word recognition scores were compared for the first time in the literature in terms of BDNF and NT-3 levels. However, the results were not statistically significant. This article is a preliminary study and was written to provide guidance for our next comprehensive project.

Strachan's syndrome and riboflavin deficiency

Strachan's syndrome comprises a triad of optic, auditory and painful sensory peripheral neuropathy. It has been recognised since the late 19th century and is presumed to result from nutritional deficiency. Patients present acute or subacutely after a period of systemic illness, weight loss or, most commonly, dietary restriction, especially veganism, which can cause riboflavin (vitamin B2) and vitamin B12 deficiencies. The syndrome is more common in people who are black British and often of Jamaican descent. We describe the clinical phenotype using a typical case example, review other endemic nutritional peripheral neuropathies and discuss the potential benefit of riboflavin as a treatment.

The effect of vitamin B12 on idiopathic tinnitus

INTRODUCTION

Tinnitus is one of the most important challenges in the field of ear, nose and throat diseases. The aim of this study was to evaluate the effect of vitamin B12 on idiopathic tinnitus.

MATERIAL AND METHODS

In this double-blind clinical trial study, 140 patients with idiopathic tinnitus were divided into two groups, the group receiving vitamin B12 and the group receiving placebo. The first group received vitamin B12 for a month and the other group received placebo. All patients filled a THI questionnaire before the participation, one month and three months after the participation. VAS evaluation questionnaires were also filled for the patients before the participation, one month and three months after the participation. The effect of vitamin B12 on tinnitus was also assessed according to hearing loss status. The two groups were also compared regarding the side effects.

RESULTS

There was no significant differences between two groups regarding age (p.value = 0.523), gender (females (p.value = 0.810) and males (p.value = 0.789), and hearing loss status (p value = 0.651). According to VAS score, there was no significant statistical differences in tinnitus severity in each group (B12 group, p.value = 0.851 and placebo group, p.value = 0.386). There was no significant statistical differences in tinnitus severity based on VAS score between two groups before the participation (p.value = 0.560), one month (p.value = 0.485) and three months (p.value = 0.254) after the participation. According to THI criterion, there was no significant statistical differences in tinnitus severity in each group (B12 group, p.value = 0.259 and placebo group, p.value = 0.521). There was no significant statistical differences in tinnitus severity based on THI score between two groups before the participation (p.value = 0.651), one month (p.value = 0.125) and three months (p.value = 0.089) after the participation. None of the patients of the two groups had any noticeable side effects. The mean of VAS and THI also had no statistically significant difference before and after the intervention in term of hearing loss status (p.value>0.05). These results were not significantly different between the two groups in term of hearing loss status (p value>0.05).

CONCLUSION

The result of this study indicated that vitamin B12 has no distinctive effect on reducing tinnitus severity.

Environmental neurology: Concepts and short history of an interdisciplinary approach to etiology, treatment and prevention

Environmental Neurology (EN), a sub-discipline of Neurology and Neurological Sciences, favors an interdisciplinary collaboration allowing a holistic approach to understanding the impact of environmental factors on the nervous system and their relationship with neurological diseases. Several examples of diseases and conditions show the large scope of subjects addressed by EN. The EN sub-discipline focuses on both individual and population issues thus joining patient care and public health, respectively. Neuropathogenesis is addressed by several major questions: How do the environment and nervous system interact? Which exogenous factors can trigger neurological disease? When, where and how do they act? What are the therapeutic implications, and how can these disorders be controlled or prevented. To answer such questions, we address the incentive for, philosophy of and methods developed by EN, which seeks to safeguard Brain Health and, thus, the quality of life.

Tropical spastic paraparesis

A large number of causative agents can result in spinal cord disorders in the tropics including etiologies similar to those of temperate regions such as trauma, spinal bone and disc lesions, tumors, epidural abscess, and congenital malformations. Yet infectious and nutritional disorders differ in their higher prevalence in tropical regions including Pott's disease; brucellosis; neuroborreliosis; various parasitic diseases such as schistosomiasis, neurocysticercosis, and eosinophilic meningitis. Notably, the retrovirus HTLV-1 is the causeof tropical spastic paraparesis/paraplegia or TSP. Nutritional causes of TSP include vitamin B and folate deficiencies, while endemic clusters of konzo and tropical ataxic myeloneuropathy occur in Africa, along with malnutrition and excessive consumption of cyanide-containing bitter cassava. Other toxic etiologies of TSP include lathyrism and fluorosis. Nutritional forms of myelopathy are associated often with optic and sensory neuropathy, hence the name tropical myeloneuropathies. Acute transverse myelopathy, seen in association with vaccination, infections, and fibrocartilaginous embolism of the nucleus pulposus, can be ubiquitous. Multiple sclerosis and optic myelopathy occur in the tropics but with lesser prevalence than in temperate regions. The advent of modern imaging in the tropics, including computed tomography and magnetic resonance imaging, has allowed better diagnosis and treatment of these conditions that are a frequent cause of death and disability. This chapter provides an overview of TSP emphasizing the most common causes with clues to diagnosis and effective therapy.

Micronutrient Deficiencies Presenting with Optic Disc Swelling Associated with or without Intracranial Hypertension: A Systematic Review

Idiopathic intracranial hypertension (IIH) is a neurological disorder characterised by optic disc swelling secondary to raised intracranial pressure (ICP) of unknown cause. Obesity is the most established and prevalent risk factor in developed countries. As obesogenic diets are high in calories and nutrient-poor, there may be associated nutritional deficiencies that contribute to the clinical presentation of IIH. Yet none, aside from iron deficiency, are currently included in the inclusion or exclusion criteria for the diagnosis of IIH. Our primary aim was to determine which micronutrient deficiencies, aside from iron deficiency, could present with optic disc swelling associated with or without intracranial hypertension that could potentially meet current IIH diagnostic criteria. To this end, we conducted a systematic search of articles published between 1 January 1980 and 18 December 2020 reporting cases of optic disc swelling associated with micronutrient deficiencies. In total, 65 cases met the eligibility criteria from initial searches: all were case reports and case series with a high risk of bias. Our findings suggest that patients with IIH or unexplained optic disc swelling ought to be screened, investigated, and treated for associated micronutrient deficiencies in vitamin A, B1 and B12; and weight loss interventions in IIH patients ought to promote better nutrition in addition to overall calorie restriction.

Association of Body Mass Index with Hearing Loss in Korean Adult Population

This study aimed to explore the relationship between body mass index (BMI) and hearing loss. We analyzed data from the Korean National Health Insurance Service Health Screening Cohort 2009−2019 (291,471 patients with hearing loss and 6,088,979 control participants). Both patient groups were subsequently divided into four groups according to BMI: <18.5 (underweight), 18.5−24.9 (normal), 25−29.9 (obese I), and ≥30 (obese II). To evaluate the relationship between BMI and hearing loss, multivariate logistic regression analysis was used, adjusting for age, sex, smoking, alcohol consumption, blood pressure, triglycerides, total cholesterol, low-density lipoprotein, proteinuria, serum creatinine, aspartate aminotransferase, alanine aminotransferase, and fasting glucose levels. The adjusted odds ratio (OR) of the underweight group for hearing loss was 1.21 (95% CI = 1.19−1.24) compared to the normal BMI group, whereas the adjusted ORs of obese I and obese II groups for hearing loss were 0.95 and 0.87, respectively. Being underweight was generally associated with an increased prevalence of hearing loss in the Korean adult population.

Visual electrophysiology in the assessment of toxicity and deficiency states affecting the visual system

Visual disturbance or visual failure due to toxicity of an ingested substance or a severe nutritional deficiency can present significant challenges for diagnosis and management, for instance, where an adverse reaction to a prescribed medicine is suspected. Objective assessment of visual function is important, particularly where structural changes in the retina or optic nerve have not yet occurred, as there may be a window of opportunity to mitigate or reverse visual loss. This paper reviews a number of clinical presentations where visual electrophysiological assessment has an important role in early diagnosis or management alongside clinical assessment and ocular imaging modalities. We highlight the importance of vitamin A deficiency as an easily detected marker for severe combined micronutrient deficiency.

Unexplained multi-sensory neuropathy syndrome in young Tanzanian adults

Background

A unique syndrome affecting young adults of unexplained hearing loss often associated with uncorrectable poor visual acuity and lower extremity numbness is endemic in Dar es Salaam. This study characterized the hearing loss, associated it with other symptoms, and gathered information on potential causes.

Methods

Forty-seven patients (23 men, 24 women) <40 years old with a symptom consistent with the syndrome, negative syphilis test, and no head injury history were recruited from Muhimbili National Hospital. 18 controls (10 men, 8 women) were recruited from the same neighborhoods as patients. Hearing ability and cochlear outer hair cell function (distortion-product otoacoustic emissions (DPOAEs)) were assessed, as were visual acuity and color vision. Peripheral neuropathy was evaluated using the Michigan Neuropathy Screening Instrument (MNSI), and physical examination. Blood C-reactive protein levels and toenail trace metal concentrations were measured. Environmental exposures were elicited using a questionnaire. Patients with at least two of the following signs were defined as having the syndrome: poor hearing with normal DPOAEs, vision not correctable to better than 20/30, or a MNSI score greater than 4.

Results

29 participants met the case definition. CRP levels did not differ between groups but manganese, cobalt and tin levels were each greater in the cases than controls. No other environmental exposure differences were noted.

Conclusions

Toenail manganese, cobalt, and tin levels were higher in those with the syndrome. These metals are potential neurotoxins suggesting a possible environmental origin for this unique and debilitating syndrome.

Thiamine deficiency disorders: a clinical perspective

Thiamine is an essential water‐soluble vitamin that plays an important role in energy metabolism. Thiamine deficiency presents many challenges to clinicians, in part due to the broad clinical spectrum, referred to as thiamine deficiency disorders (TDDs), affecting the metabolic, neurologic, cardiovascular, respiratory, gastrointestinal, and musculoskeletal systems. Concurrent illnesses and overlapping signs and symptoms with other disorders can further complicate this. As such, TDDs are frequently misdiagnosed and treatment opportunities missed, with fatal consequences or permanent neurologic sequelae. In the absence of specific diagnostic tests, a low threshold of clinical suspicion and early therapeutic thiamine is currently the best approach. Even in severe cases, rapid clinical improvement can occur within hours or days, with neurological involvement possibly requiring higher doses and a longer recovery time. Active research aims to help better identify patients with thiamine‐responsive disorders and future research is needed to determine effective dosing regimens for the various clinical presentations of TDDs. Understanding the clinical diagnosis and global burden of thiamine deficiency will help to implement national surveillance and population‐level prevention programs, with education to sensitize clinicians to TDDs. With concerted effort, the morbidity and mortality related to thiamine deficiency can be reduced.

Treatment and Outcomes in Nutritional Optic Neuropathy

PURPOSE OF REVIEW

Nutritional optic neuropathy is a potential cause of severe visual loss; however, appropriate and timely management can result in excellent visual outcomes. The purpose of this review is to outline our current understanding of the treatment and outcomes for nutritional optic neuropathy.

RECENT FINDINGS

Current understanding of nutritional optic neuropathy has been greatly aided by some well-reported and investigated epidemics of the condition, most notably the Cuban epidemic optic neuropathy of the early 1990s. More recently, there is an emerging literature surrounding nutritional deficiencies that can occur in patients who have undergone bariatric surgery. There also continues to be a stream of case reports in the literature that add to our understanding. Nutritional optic neuropathy has a great deal of overlap with toxic optic neuropathies and hereditary optic neuropathies and should not be thought of in isolation from these conditions. The mainstay of treatment for nutritional optic neuropathy involves identifying and replacing deficient nutrients as well as identifying and eliminating contributory toxins. It is also important to identify contributory genetic factors and to consider the broader social, economic and societal factors which may contribute.

Cuban Epidemic Optic Neuropathy (1991-1993) and José Saramago's Novel Blindness (1995)

PURPOSE

This article reviews the history of Cuban epidemic optic neuropathy (1991-1993), which caused visual loss, peripheral neuralgias, and other neurologic symptoms in over 50,000 persons, an incidence of almost 0.5% of the entire population. The clinical findings, etiology, and treatment are described. We then relate the Cuban epidemic to the fictional epidemic of contagious blindness depicted by Nobel Laureate José Saramago in his 1995 novel Blindness. This novel describes an unnamed modern city in which all inhabitants, except the ophthalmologist's wife, are affected with a white, not black, blindness.

DESIGN

Historical review and literary essay.

METHODS

The sources for the Cuban epidemic were an extensive review of the published literature and personal communications with physicians who treated these patients. Both authors have analyzed the novel and the critical literature about Saramago's writings.

RESULTS

Though Saramago uses the epidemic of blindness as an allegory to comment on human weakness and immorality, he may also have known of the actual Cuban epidemic. Saramago was a lifelong member of the Communist party, as well as a friend of Fidel Castro and admirer of the Cuban government. We have no proof that Blindness was influenced by the Cuban epidemic, but we find it plausible.

CONCLUSION

It is valuable to examine the real and fictional epidemics side by side, not least because Saramago's novel depicts the actions of an ophthalmologist during an epidemic of blindness. Ophthalmologists may be interested in a novel that uses the language of eyes, vision, sight, and blindness extensively.

Selective Damage to Either the “M” Or “P” Cell Pathway in Human Retinal Disease: Implications for Visual Processing

Studies in primates have shown there to be 2 main visual afferent pathways (magno and parvo) operating in parallel with different functional roles. Disease state may selectively affect one or other of these, as shown by particular sensory losses. In cases of treated Cuban tropical "neuropathy" (a retinopathy also occurs) visual acuity and achromatic contrast sensitivity are preserved although colour vision is severely affected indicating selective preservation of the "magno" pathway. In Melanoma Associated Retinopathy, red-green colour vision is preserved although achromatic contrast sensitivity for low spatial frequencies, and the detection of motion is damaged suggesting preferential damage to the "magno" pathway. Our studies illuminate two controversial aspects of the P and M systems: the role of type II parvocellular cells in colour vision and the role of M cells in detecting stimuli of low spatial and low temporal frequency.

Early childhood undernutrition increases risk of hearing loss in young adulthood in rural Nepal

Background

Prevalence of young adult hearing loss is high in low-resource societies; the reasons for this are likely complex but could involve early childhood undernutrition.

Objective

We evaluated preschool childhood stunting, wasting, and underweight as risk factors for hearing loss in young adulthood in Sarlahi District, southern Nepal.

Design

Ear health was assessed in 2006-2008 in a cohort of 2193 subjects aged 16-23 y, who as children <60 mo of age participated in a 16-mo placebo-controlled, randomized vitamin A supplementation trial from 1989 to 1991. At each of five 4-mo assessments, field staff measured children's weight, height, and mid-upper arm circumference (MUAC) and recorded validated parental history of ear discharge in the previous 7 d. Children were classified as stunted [<-2 z score height-for-age (HAZ)], underweight [<-2 z score weight-for-age (WAZ)], or wasted [<-2 z score MUAC-for-age (MUACAZ) or body mass index-for-age (BMIAZ)]. At follow-up, hearing was tested by audiometry and tympanometry, with hearing loss defined as pure-tone average >30dB in the worse ear (0.5, 1, 2, 4 kHz) and middle-ear dysfunction as abnormal tympanometric peak height (<0.3 or >1.4 mmho) or width (<50 or >110 daPa).

Results

Hearing loss, present in 5.9% (95% CI: 5.01%, 7.00%) of subjects, was associated with early childhood stunting (OR: 1.64; 95% CI: 1.10, 1.45), underweight (OR: 1.70; 95% CI: 1.18, 2.44) and wasting by BMIAZ (OR: 1.88; 95% CI: 1.19, 2.97) and MUACAZ (OR: 2.14; 95% CI: 1.47, 3.12). Abnormal tympanometry, affecting 16.6% (95% CI: 15.06%, 18.18%), was associated with underweight (OR: 1.46; 95% CI: 1.16, 1.84) and wasting by BMIAZ (OR: 1.80; 95% CI: 1.32, 2.46) and MUACAZ (OR: 1.42; 95% CI: 1.10, 1.84), but not stunting (OR: 1.18; 95% CI: 0.93, 1.49) in early childhood. Highest ORs were observed for subjects with both hearing loss and abnormal tympanometry, ranging from 1.87 to 2.24 (all lower 95% CI >1.00).

Conclusions

Early childhood undernutrition is a modifiable risk factor for early adulthood hearing loss.

Differential diagnosis of multiple sclerosis in Latin America

Improvement of multiple sclerosis (MS) diagnoses leads to earlier and correct disease management. The differential diagnostic workup for MS comprises a large variety of medical conditions. There are general guidelines and criteria for diagnosing MS worldwide, but awareness of regional differences needs to be kept in mind. Latin American patients who are screened for MS diagnoses may require an approach that is not exactly the same as that used for patients in North America, western Europe or Asia. In the present review, the conditions that are important for the differential diagnoses of MS in Latin America are reviewed. They include infections, metabolic diseases, nutritional deficits and other autoimmune conditions that physicians in charge of these patients need to be familiar with.

The interaction of malnutrition and neurologic disability in Africa

Malnutrition and neurodisability are both major public health problems in Africa. This review highlights key areas where they interact. This happens throughout life and starts with maternal malnutrition affecting fetal neurodevelopment with both immediate (eg, folate deficiency causing neural tube defects) and lifelong implications (eg, impaired cognitive function). Maternal malnutrition can also increase the risk of perinatal problems, including birth asphyxia, a major cause of neurologic damage and cerebral palsy. Macronutrient malnutrition can both cause and be caused by neurodisability. Mechanisms include decreased food intake, increased nutrient losses, and increased nutrient requirement. Specific micronutrient deficiencies can also lead to neurodisability, for example, blindness (vitamin A), intractable epilepsy (vitamin B6), and cognitive impairment (iodine and iron). Toxin ingestion (eg, from poorly processed cassava) can cause neurodisability including a peripheral polyneuropathy and a spastic paraparesis. We conclude that there is an urgent need for nutrition and disability programs to work more closely together.

Tropical myelopathies

A large number of causal agents produce spinal cord lesions in the tropics. Most etiologies found in temperate regions also occur in the tropics including trauma, herniated discs, tumors, epidural abscess, and congenital malformations. However, infectious and nutritional disorders occur with higher prevalence in tropical regions. Among the most common infectious etiologies are tuberculous Pott's disease, brucellosis, and neuroborreliosis. Parasitic diseases such as schistosomiasis, neurocysticercosis, and eosinophilic meningitis are frequent causes of nontraumatic paraplegia. The retrovirus HTLV-1 is a cause of tropical spastic paraparesis. Nutritional causes of paraparesis include deficiencies of vitamin B12 and folate; endemic clusters of konzo and tropical ataxic myeloneuropathy are associated in Africa with malnutrition and excessive consumption of cyanide-containing bitter cassava. Other toxic etiologies of tropical paraplegia include lathyrism and fluorosis. Nutritional forms of myelopathy are associated often with optic and sensory neuropathy, hence the name tropical myeloneuropathies. Acute transverse myelopathy is seen in association with vaccination, infections, and fibrocartilaginous embolism of the nucleus pulposus. Multiple sclerosis and optic myelopathy occur in the tropics but with lesser prevalence than in temperate regions. The advent of modern imaging in the tropics, including computed tomography and magnetic resonance imaging, has allowed better diagnosis and treatment of these conditions that are a frequent cause of death and disability.

Macular spectral domain optical coherence tomography findings in Tanzanian endemic optic neuropathy

Bilateral optic neuropathy in Dar es Salaam is now considered endemic and is estimated to affect 0.3-2.4% of young adults. The condition is characterized by a subacute bilateral loss of central vision of unknown aetiology. Findings of spectral domain optical coherence tomography have not previously been reported for these patients. All patients diagnosed with endemic optic neuropathy over a 2-year period at the Muhimbili National Hospital underwent spectral domain optical coherence tomography macular imaging. Scans were graded qualitatively for severity of retinal nerve fibre layer loss as well as the presence of microcystic macular changes, which have not previously been described in this condition. Of the 128 patients included (54.7% male; median age 20 years), severe retinal nerve fibre layer loss was found in 185 eyes (74.0%). There was full concordance in retinal nerve fibre layer thickness between the two eyes in 113 (91.1%) patients. Microcystic macular spaces were found in 16 (12.5%) patients and were bilateral in nine (7.0%) individuals. These changes were typically more prominent in the nasal than the temporal macula, predominantly involving the inner nuclear layer, and often occurred in an annular configuration that was evident on en face infra-red imaging, though not discernible on colour fundus photography or clinically. All patients with microcystic macular changes had severe thinning of the retinal nerve fibre layer (P = 0.02). Four patients in whom cystic spaces were demonstrated had sequential scans, and there was no detectable alteration in the configuration of these changes over a period of up to 16 months. This is the first study to document optical coherence tomography findings in endemic optic neuropathy. We have observed symmetrical severe loss of the caeco-central projection (papillomacular bundle) with otherwise well-preserved macular architecture. Also, we have observed microcystic retinal changes in a significant proportion of patients, which were associated with severe retinal nerve fibre layer loss. Similar changes have recently been reported from optical coherence tomography images of patients with multiple sclerosis, relapsing isolated optic neuritis, dominant optic atrophy, Leber's hereditary optic neuropathy and a patient with a chronic compressive optic neuropathy, supporting the hypothesis that this may be a non-specific phenomenon secondary to ganglion cell death. The correspondence of the changes to an annulus discernible on infra-red en face imaging, but not using other conventional retinal imaging techniques highlights the potential usefulness of this modality.

Concurrent outbreaks of cholera and peripheral neuropathy associated with high mortality among persons internally displaced by a volcanic eruption

BACKGROUND

In October 2004, Manam Island volcano in Papua New Guinea erupted, causing over 10 000 villagers to flee to internally displaced person (IDP) camps, including 550 from Dugulaba village. Following violence over land access in March 2010, the IDPs fled the camps, and four months later concurrent outbreaks of acute watery diarrhea and unusual neurological complaints were reported in this population.

MATERIALS AND METHODS

A retrospective case-control study was conducted to identify the risk factors for peripheral neuropathy. Rectal swabs were collected from cases of acute watery diarrhea. Hair and serum metals and metalloids were analyzed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS).

RESULTS

There were 17 deaths among the 550 village inhabitants during the outbreak period at a crude mortality rate 21-fold that of a humanitarian crisis. Vibrio cholerae O1 El Tor Ogawa was confirmed among the population. Access to community-level rehydration was crucial to mortality. Peripheral neuropathy was diagnosed among cases with neurological symptoms. A balanced diet was significantly protective against neuropathy. A dose-response relationship was seen between peripheral neuropathy and a decreasing number of micronutrient- rich foods in the diet. Deficiencies in copper, iron, selenium and zinc were identified among the cases of peripheral neuropathy.

CONCLUSIONS

Cholera likely caused the mostly preventable excess mortality. Peripheral neuropathy was not caused by cholera, but cholera may worsen existing nutritional deficiencies. The peripheral neuropathy was likely caused by complex micronutrient deficiencies linked to non-diversified diets that potentially increased the vulnerability of this population, however a new zinc-associated neuropathy could not be ruled out. Reoccurrence can be prevented by addressing the root cause of displacement and ensuring access to arable land and timely resettlement.

Nutritional disorders in tropical neurology

About three-fourths of the total world population live in the tropics but consume only 6% of worldwide food production and contribute 15% of the world's net revenue explaining the short life expectancy, high infantile mortality, and poor daily caloric intake; moreover, lack of clean drinking water and deficient sanitation promote water-borne infections, diarrhea, and risk of malabsorption that contribute to the prevalence of malnutrition in the tropics. One-third of the world's population consumes insufficient iodine increasing the risk for mental retardation and deafness due to maternal hypothyroidism. The main nutritional syndromes comprise protein-energy malnutrition (marasmus and kwashiorkor); nutritional neuropathies, myelopathies and neuromyelopathies, as well as specific deficiencies of vitamins and micronutrients including iodine, iron, zinc, and selenium.

Interrelationships of undernutrition and neurotoxicity: food for thought and research attention

The neurotoxic actions of chemical agents on humans and animals are usually studied with little consideration of the subject's nutritional status. States of protein-calorie, vitamin and/or mineral undernutrition are associated with a range of neurodevelopmental, neurological and psychiatric disorders, commonly with involvement of both the central and the peripheral nervous system. Undernutrition can modify risk for certain chemical-induced neurologic diseases, and in some cases undernutrition may be a prerequisite for neurotoxicity to surface. In addition, neurologic disease associated with undernutrition or neurotoxicity may show similarities in clinical and neuropathological expression, especially in the peripheral nervous system. The combined effects of undernutrition and chemical neurotoxicity are most relevant to people with low incomes who experience chronic hunger, parasitism and infectious disease, monotonous diets of plants with neurotoxic potential (notably cassava), environmental pollution from rapid industrial development, chronic alcohol abuse, or prolonged treatment with certain therapeutic drugs. Undernutrition alone or in combination with chemical exposure is also important in high-income societies in the setting of drug and alcohol abuse, old age, food faddism, post-bariatric surgery, and drug treatment for certain medical conditions, including cancer and tuberculosis. The nutritional demands of pregnancy and lactation increase the risk of fetal and infant undernutrition and chemical interactions therewith.

[Epidemiological profile of reported beriberi cases in Maranhão State, Brazil, 2006-2008]

This study aimed to describe the epidemiological profile of beriberi cases and related deaths reported from 2006 to 2008 in Maranhão State, Brazil. Data were obtained from beriberi notification forms at the State Health Department. The global Moran index was used to evaluate spatial auto-correlation. 1207 cases and 40 deaths were reported. The western and central regions of the State showed strong spatial auto-correlation of incidence rates. Cases and deaths were concentrated from May to August, in young men (20-40 years). Regular alcohol consumption and smoking were recorded among fatal cases. Low income and heavy labor were widespread among cases. Common symptoms were asthenia, numbness, and swollen legs, difficulty walking, and calf pain. The profile of cases and their symptoms (except swollen legs) are characteristic of dry beriberi. We recommend further studies on the resurgence of beriberi in Brazil.

Abnormalities of the optic disc

The optic disc represents the anterior end of the optic nerve, the most forward extension of the central nervous system (CNS). The optic disc gives a rare glimpse into the CNS. Hence, diseases of the CNS are often manifested on fundus examination. Abnormalities of the optic disc may reflect eye disease (such as glaucoma), problems in development (as in various syndromes), or CNS disease (such as increased intracranial pressure). Each optic nerve is composed of about 1.2 million axons deriving from the retinal ganglion cells of one eye. Optic atrophy is a morphological sequela reflecting the loss of many or all of these axons. Myriad diseases such as hereditary, metabolic, tumor, and increased intracranial pressure can lead to optic atrophy. Some diseases, such as optic disc drusen, intracranial masses, orbital tumors, ischemic optic neuropathies, inflammations, and infiltrations, can produce optic disc edema before leading to optic atrophy. A number of new imaging modalities, such as optical coherence tomography (OCT), quantitate the thickness of the peripapillary retinal nerve fiber layer as an indirect measure of axonal loss or swelling. OCT can therefore be used to quantitate pathology or the response to therapy in various generalized CNS conditions, such as multiple sclerosis.

Age-related hearing loss, vitamin B12, and folate in the elderly

OBJECTIVE

Determine the correlation between the hearing threshold and the serum levels of vitamin B12 (cobalamin) and folic acid among elderly subjects (> 60 years) with age-related hearing loss (ARHL).

STUDY DESIGN

Cross-sectional.

SETTING

Community.

SUBJECTS AND METHODS

Subjects included elderly who were found apparently healthy following repeated examination by physicians. The pure tone average (PTA) for the speech and high frequencies, and the serum folate and cobalamin were determined and the correlation found.

RESULTS

The mean ± SD values of serum folate among the subjects with normal PTA in the speech frequencies (0-30 dB) was 412.3 nmol/L ± 17.6 nmol/L, while among those with hearing loss (HL), it was 279.1 nmol/L ± 17.2 nmol/L (P = 0.01). In the high frequencies, the mean ± SD values among the subjects with normal PTA was 426.3 nmol/L ± 17.6 nmol/L, while among those with HL, it was 279.14 nmol/L ± 171.2 nmol/L. The serum cobalamin among the subjects with normal PTA within the speech frequencies was 49.7 pmol/L ± 9.4 pmol/L, while among those with speech-frequency HL, it was 42.6 pmol/L ± 10.2 pmol/L. However, for high frequencies, the mean ± SD values among the subjects with normal PTA was 47.4 pmol/L ± 7.3 pmol/L, while among those with HL, it was 41.3 pmol/L ± 9.2 pmol/L. Spearman's correlation revealed that low folate (correlation coefficient = -0.27, P = 0.01) and cyanocobalamin (correlation coefficient = -0.35, P = 0.02) were significantly associated with increasing hearing threshold in the high frequencies. After adjusting for age, serum folate (correlation coefficient = -0.01, P = 0.01) was significant, while vitamin B12 (correlation coefficient = -0.01, P = 0.74) was not.

CONCLUSION

Serum folate was significantly lower among elderly with ARHL. Trials on nutritional supplementation may substantiate the role of serum folate in ARHL.

Neurological disorders in complex humanitarian emergencies and natural disasters

Complex humanitarian emergencies include the relatively acute, severe, and overwhelming health consequences of armed conflict, food scarcity, mass displacement, and political strife. Neurological manifestations of complex humanitarian emergencies are important and underappreciated consequences of emergencies in populations worldwide. This review critically assesses the existing knowledge of the range of neurological disorders that accompany complex humanitarian emergencies and natural disasters in both the acute phase of crisis and the "long shadow" that follows.

Neurologic presentations of nutritional deficiencies

Optimal functioning of the central and peripheral nervous system is dependent on a constant supply of appropriate nutrients. The first section of this review discusses neurologic manifestations related to deficiency of key nutrients such as vitamin B(12), folate, copper, vitamin E, thiamine, and others. The second section addresses neurologic complications related to bariatric surgery. The third sections includes neurologic presentations caused by nutrient deficiencies in the setting of alcoholism. The concluding section addresses neurologic deficiency diseases that have a geographic predilection.

Nutritional optic and peripheral neuropathy: a case report

Introduction

The link between nutritional status and either optic or peripheral neuropathies is well established with tobacco, ethanol, deficiencies in thiamine, vitamin A, B12, B3 and B6 and protein-energy malnutrition all being causative.

Case presentation

We describe the case of a 32-year-old Afro-Caribbean of Jamaican origin presenting with blurred vision and a painful burning sensation in his feet. The clinical features were consistent with optic and peripheral neuropathy.

Conclusions

The patient followed a strict vegan diet and consumed no animal products. A review of the literature highlights similarities between this case and Strachan's syndrome, a combination of optic and peripheral neuropathy and cutaneous excoriation, providing further evidence for the association between this clinical presentation, dietary deficiency and, as recently postulated, previous residence in a tropical or sub-tropical climate.

Brain barrier dysfunction in Cuban epidemic optic neuropathy

BACKGROUND AND PURPOSE

There are practically no references to cerebrospinal fluid (CSF) studies in tropical or nutritional neuropathies. In the present paper we present the results of CSF studies in patients with Cuban Epidemic Optic Neuropathy (CEON) during epidemic and endemic periods, with an appraisal as to the contribution of brain barriers' function in the pathophysiology of this disease.

METHODS

Two hundred and five patients with CEON were studied during the epidemic period (1992-1993) and 12 patients outside the outbreak (1995-1997). CSF protein determination and electrophoresis were carried out, as well as serum and CSF albumin and immunoglobulin G (IgG) quantitation for calculating IgG and Q(alb) indexes, in order to evaluate intrathecal IgG synthesis and the permeability of the blood-CSF barrier (B-CSF B).

RESULTS

One fourth of the patients had increased permeability of the B-CSF B, but damage was more frequent between 16 and 60 days from onset of disease, disappearing after 120 days. B-CSF B dysfunction was more prevalent in patients with severe neurological impairment, although it was not related to the severity of ophthalmological damage. The group of patients studied outside of the outbreak (endemic period) showed similar results.

DISCUSSION

The possible association of increased permeability of the B-CSF B with oxidative stress, which lies on the basis of this epidemic outbreak, is discussed.

Environmental neurology: A promising new field of practice and research

The environment has profound influences on human health. Environment is the combination of natural (physical, chemical, biological) and cultural (sociological) conditions in which living organisms, man in particular, develop. Adaptation is the human physiological response to external factors including mechanisms such as circadian rhythms (sleep and wakefulness), biorhythms, thermoregulation, and others to adjust to changes in natural conditions (night and day, cosmic rhythms, climatic changes). Man remains vulnerable due to a number of factors: genetic, physiological, age, sex, impaired reparative or protective mechanisms, or acquired factors (risky behaviors and lifestyle, nutritional habits). Hazard is the potential of a particular factor to have a negative impact on health. Risk is the probability of that hazard occurring; it defines and measures the predictability of that hazard. A number of environmental factors have a profound influence on the pathogenesis of neurological disorders. Environmental neurology follows the classical diagnostic precepts: from symptom to syndrome in the search for etiology and individualized treatment of the patient. It also utilizes principles of epidemiology and public health, toxicology and occupational medicine; i.e., an approach by "milieu" and by specific factors or "agents." Environmental neurology offers a promising new field of practice and research.

Nutritional neuropathies

Optimal functioning of the central and peripheral nervous system is dependent on appropriate nutrients. Neurologic consequences of nutritional deficiencies are not restricted to underdeveloped countries. Multiple nutritional deficiencies can coexist. Obesity is of particular concern in the developed world. The rising rate of bariatric surgery are accompanied by neurologic complications related to nutrient deficiencies. Prognosis depends on prompt recognition and institution of appropriate therapy. This review discusses peripheral nervous system manifestations related to the deficiency of key nutrients, neurologic complications associated with bariatric surgery, and conditions that have a geographic significance associated with bariatric surgery and certain conditions that have a geographic predilection.

Is B vitamins deficiency associated with prevalence of Alzheimer's disease in Cuban elderly?

Alzheimer's disease (AD), is a major public health problem among the elderly in industrialized countries and a growing problem in developing countries. In Cuba, 14,6% of the population is older than 60 years. The AD prevalence in Cuba lies between 5,13-7,14%. Several studies have shown the relationship between the low nutritional status of B vitamins, hyperhomocysteinaemia with loss of neuro-cognitive function and AD. In studies during the epidemic neuropathy that affected Cuba between 1992-1993, B vitamins deficiency and smoking habits were strongly associated with the epidemic. Some studies in healthy adults and elderly after this epidemic have shown a sub-clinical deficiency of some B vitamins and a high prevalence of infection by Helicobacter pylori. The possibility that B vitamin deficiencies could be an additional risk factor for the high prevalence of the AD in Cuba is discussed.

A review of the biochemistry, metabolism and clinical benefits of thiamin(e) and its derivatives

Thiamin(e), also known as vitamin B1, is now known to play a fundamental role in energy metabolism. Its discovery followed from the original early research on the ‘anti-beriberi factor’ found in rice polishings. After its synthesis in 1936, it led to many years of research to find its action in treating beriberi, a lethal scourge known for thousands of years, particularly in cultures dependent on rice as a staple. This paper refers to the previously described symptomatology of beriberi, emphasizing that it differs from that in pure, experimentally induced thiamine deficiency in human subjects. Emphasis is placed on some of the more unusual manifestations of thiamine deficiency and its potential role in modern nutrition. Its biochemistry and pathophysiology are discussed and some of the less common conditions associated with thiamine deficiency are reviewed. An understanding of the role of thiamine in modern nutrition is crucial in the rapidly advancing knowledge applicable to Complementary Alternative Medicine. References are given that provide insight into the use of this vitamin in clinical conditions that are not usually associated with nutritional deficiency. The role of allithiamine and its synthetic derivatives is discussed. Thiamine plays a vital role in metabolism of glucose. Thus, emphasis is placed on the fact that ingestion of excessive simple carbohydrates automatically increases the need for this vitamin. This is referred to as high calorie malnutrition.

Receding horizons of health: biocultural approaches to public health paradoxes

Worldwide challenges to health reflect a "paradox of success," whereby both the strengths and the weaknesses of current approaches in public health, epidemiology, and biomedicine have determined the nature of the health problems we now face. In detail, we analyze and illustrate five constituent paradoxes that fuel continued health risk even in the face of success, including: (1) unmasking, (2) local biology, (3) socialization, (4) emerging and reemerging disease, and (5) savage inequity. We trace the pathways behind the paradoxes and their effects on health, and demonstrate that biocultural dynamics are involved in each. Furthermore, we track the roots of health paradox to changes that divert or disrupt pathways for production of health. These analyses contribute to an emerging literature of research and praxis on integrative biocultural models of health.

Neuro-ophthalmologic manifestations of konzo

Konzo is a permanent spastic paraparesis of acute onset attributed to the effect of cyanogenic compounds from insufficiently processed bitter cassava in combination with low protein intake. In all studies of konzo, ophthalmologic complaints have been presented but only recently systematic studies of the neuro-ophthalmologic disturbances in konzo have been done. In this review, we see that about half the patients have an optic neuropathy with decreased visual acuity, alterations of the visual fields, atrophy of the temporal part of the retinal nerve fibre layer linked with temporal pallor of the optic disk. About half of the konzo patients also have abnormal visual evoked potentials, with both delayed latency and reduced amplitude. A small number of konzo patients have an ocular motor disturbance leading to a pendular nystagmus. The severity of the neuro-ophthalmologic involvement is not parallel to the severity of the motor disturbance in konzo. This may suggest that two different pathogenic mechanisms are involved.

[Neuropathy with non-alcoholic thiamine deficiency: two cases of bladder disorders]

INTRODUCTION

Neuropathy with non-alcoholic thiamine deficiency is reported in the literature, but bladder disorders are rarely detailed.

CASE REPORTS

We report two cases of bladder disorders in neuropathy with thiamine deficiency. One patient presented with a flaccid bladder and impaired sensation; the postvoid residual volume was raised. The other patient had reduced bladder capacity, with detrusor hyperreflexia and detrusor-sphincter dyssynergia. In both cases, the bladder disorders disappeared with thiamine supplementation.

CONCLUSION

Bladder symptoms may be heterogeneous in nonalcoholic neuropathy. The prognosis is good after vitamin supplementation.

Selenium deficiency and viral infection

The discovery that the juvenile cardiomyopathy known as Keshan disease likely has a dual etiology that involves both a nutritional deficiency of the essential trace mineral selenium (Se) as well as an infection with an enterovirus provided the impetus for additional studies of relationships between nutrition and viral infection. An amyocarditic strain of coxsackievirus B3, CVB3/0, converted to virulence when it was inoculated into Se-deficient mice. This conversion was accompanied by changes in the genetic structure of the virus so that its genome closely resembled that of other known virulent CVB3 strains. Similar alterations in virulence and genomic composition of CVB3/0 could be observed in mice fed normal diets but genetically deprived of the antioxidant selenoenzyme glutathione peroxidase (knockout mice). More recent research has shown that a mild strain of influenza virus, influenza A/Bangkok/1/79, also exhibits increased virulence when given to Se-deficient mice. This increased virulence is accompanied by multiple changes in the viral genome in a segment previously thought to be relatively stable. Epidemic neuropathy in Cuba has features that suggest a combined nutritional/viral etiology. Further research, both basic and applied, is needed to assess properly the possible role of malnutrition in contributing to the emergence of novel viral diseases.

Neuro-ophthalmologic findings in konzo, an upper motor neuron disorder in Africa

PURPOSE

To investigate the neuro-ophthalmological manifestations in konzo, a non-progressive symmetric spastic para/tetraparesis of acute onset associated with consumption of insufficiently processed bitter cassava roots combined with a low protein intake.

METHODS

Twenty-one Congolese konzo patients underwent neuro-ophthalmological investigations including visual acuity testing, assessment of light pupillary reflexes, evaluation of ocular motility and deviation, direct ophthalmoscopy, and visual field perimetry. Objective refraction including retinoscopy and keratometry, and slit-lamp biomicroscopy were also done.

RESULTS

Five patients had visual impairment, and 14 had temporal pallor of the optic disc. Fourteen presented visual field defects, the most frequent being concentric constriction and peripheral defects. Overall, 11 subjects had symptoms qualifying for the diagnosis of optic neuropathy. Two had spontaneous pendular nystagmus in primary position of gaze. Visual field defects and pallor of the optic discs were found in mild, moderate and severe forms of konzo. No correlation was found between the severity of the motor disability of konzo and the extent of visual field loss.

CONCLUSIONS

Konzo was associated with optic neuropathy and a few patients had nystagmus. Although the etiopathogenesis of this optic neuropathy remains to be elucidated, the symmetry of the involvement suggests a toxic origin. We suggest that cyanide causes the neuro-ophthalmological damage in konzo. However, the optic neuropathy in konzo patients does not resemble the features of the epidemic optic neuropathy in Tanzania, Cuba or Nigeria, Leber's hereditary optic neuropathy, tobacco amblyopia or vitamin B deficiency.