|Year : 2012 | Volume
| Issue : 1 | Page : 61-69
Vitamin B12-homocysteine interaction and the efficacy of B12 therapy in relation to anemia and neurological disease in a North Indian population
Madhumita Premkumar1, N Gupta1, T Singh2, T Velpandian3
1 Department of Medicine, Maulana Azad Medical College and Associated Hospitals, Bahadur Shah Zafar Marg, New Delhi, India
2 Department of Pathology, Maulana Azad Medical College and Associated Hospitals, Bahadur Shah Zafar Marg, New Delhi, India
3 Department of Ocular Pharmacology, Dr. Rajendra Prasad Eye Centre, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
|Date of Submission||20-Jul-2011|
|Date of Acceptance||18-Aug-2011|
|Date of Web Publication||23-Feb-2012|
Department of Medicine, Maulana Azad Medical College and Associated Hospitals, Bahadur Shah Zafar Marg, New Delhi 110 002
Source of Support: Supported by a grant from the Indian Council of Medical Research, New Delhi, Conflict of Interest: None
| Abstract|| |
Background: Vitamin B12 deficiency leads to myriad hematological and neurological changes leading to megaloblastic anemia and disorders of the nervous system like subacute combined degeneration of the spinal cord, cognitive impairment, peripheral neuropathy, etc. In this case series, an attempt was made to investigate the neurological manifestations of patients with diagnosed vitamin B12-deficient megaloblastic anemia, determine the cause of vitamin deficiency in these cases, and monitor their response to vitamin B12 therapy. Materials and Methods: The study was conducted in a tertiary care referral teaching hospital in New Delhi during a period of over 2 years from August 2007 to December 2009. Eighty-five consecutive patients with megaloblastic anemia (MA) due to vitamin B12 deficiency were screened and a total of 28 patients with neurological and psychiatric symptoms were selected for the study. In addition to bone marrow examination, blood counts, red cell indices, and biochemical tests, assays of serum vitamin B-12, folate, and homocysteine were done. Neuroimaging by magnetic resonance studies and nerve conduction studies (NCS) was done where clinically applicable. Follow-up was done at least twice at 3 months and 6 months to assess clinical, neurological, and hematological response to vitamin B12 therapy. Results: The primary study group of MA with B12 deficiency had 85 patients. Of these, only 28 (32.9%) patients had neurological and/or psychiatric features. There were 18 male and 10 female subjects (M: F ratio being 1.8:1). The mean age was 32.80 years with a range of 18-68 years. Though the majority of MA patients (77.6%) were vegetarian, a good 22% consumed a nonvegetarian diet. Neurological manifestations included peripheral neuropathy in 14 (50%), myelopathy in 2 (7.14%), myeloneuropathy in 2 (7.14%), acute confusional state in 4 (14.28%), and cognitive impairment in 20 (71.42%) patients. Mood disturbances, anxiety, and irritability were also seen. NCS was done in 18 cases and showed demyelinating peripheral neuropathy in 12 cases and both axonal and demyelinating changes in two cases. Magnetic resonance imaging (MRI) showed four cases with the classical demyelination on spinal MRI with white matter hyper intense lesions in the posterior tracts on T2 weighted images. At 6-month follow-up with B12 therapy, 10/14 patients with neuropathy recovered completely, 2/14 had partial recovery, and 2 had poor recovery. While the cases of myelopathy had only partial recovery at 6 months, all four cases with acute confusional state recovered completely in response to B12 therapy. Conclusion: The electrodiagnostic and neuroimaging changes in vitamin B12 deficiency are consistent with focal demyelination of white matter tracts in the brain, the spinal cord, and peripheral nerves. In this case series of B12 deficiency MA, we found demyelinating peripheral neuropathy to be the predominant presenting neurological disease. However, cognitive impairment with behavioral changes was found to be common on neurological and psychiatric examination. Many of these features were found to be reversible with B12 therapy.
Keywords: Cobalamin neuropathy, LC/MS/MS, megaloblastic anemia, myeloneuropathy, vitamin B12 deficiency
|How to cite this article:|
Premkumar M, Gupta N, Singh T, Velpandian T. Vitamin B12-homocysteine interaction and the efficacy of B12 therapy in relation to anemia and neurological disease in a North Indian population. Int J Nutr Pharmacol Neurol Dis 2012;2:61-9
|How to cite this URL:|
Premkumar M, Gupta N, Singh T, Velpandian T. Vitamin B12-homocysteine interaction and the efficacy of B12 therapy in relation to anemia and neurological disease in a North Indian population. Int J Nutr Pharmacol Neurol Dis [serial online] 2012 [cited 2021 Dec 1];2:61-9. Available from: https://www.ijnpnd.com/text.asp?2012/2/1/61/93132
| Introduction|| |
Megaloblastic anemias (MA) are a morphologically similar group of hematopoietic disorders having in common a selective reduction in the rate of DNA synthesis.  Megaloblastic anemias most commonly are due to deficiency of the two major microvitamins B12 and folate. Vitamin B12 deficiency can be caused by impaired gastric or intestinal absorption, inadequate dietary intake, drugs, or congenital errors in metabolism, Zollinger Ellison syndrome, chronic pancreatitis, small bowel disorders like regional enteritis, blind loop syndrome, tropical sprue, etc., or even fish tapeworm infection, though the latter entity has not been described in India. In the pediatric population, a number of inborn errors of metabolism interfere with the cobalamin/folate pathways and may thus present as megaloblastic anemia. These include Imerslünd-Grasbeck syndrome, methylmalonic aciduria, homocystinuria, transcobalamin II deficiency, hereditary orotic aciduria, Lesch-Nyhan syndrome, etc. ,
Diet may be an important factor causing the low levels of cobalamin in our population. Vegetarianism has been held responsible for causing megaloblastic anemia in several studies, both in India and in Asian communities who have migrated to western countries.  However, any nutritional study conducted in India must be viewed within the broad context of the heterogeneity, i.e., racial, religious, ethnic, cultural, and socioeconomic differences, of its population. The north Indian diet is typically lactovegetarian and consists largely of cereals, millets, vegetables, milk, and milk products predisposing them to cobalamin deficiency. In addition to the above staple diet, the nonvegetarian population consumes occasional eggs and very rarely meat and poultry. Hence even this group is susceptible to cobalamin deficiency which can be determined by detailed dietary history and food frequency questionnaires.
In the nervous system, vitamin B12 acts as the coenzyme for methyl malonyl CoA mutase reaction which is responsible for myelin synthesis. Methylation processes are central to the biochemical basis of the neuropsychiatry of folate and B 12 deficiencies. The de novo synthesis of methionine requires vitamin B12, which aids transfer of the methyl group to homocysteine. In turn methionine is required for synthesis of S-adenosyl methionine (SAM) which is the crucial methyl donor in numerous reactions involving proteins, phospholipids, and biogenic amines. Upon transfer of the methyl group SAM is converted to S-adenosyl homocysteine (SAH) which is subsequently hydrolyzed to homocysteine and adenosine. In the case of either folate or vitamin B12 deficiency, the methionine synthase reaction is impaired [Figure 1]. Thus, neurological manifestations in MA due to B12 deficiency are attributable to pathological changes in the peripheral nerves, optic nerves, and posterior and lateral columns of the spinal cord and the brain. This results in neuropsychiatric abnormalities such as neuropathy, myelopathy, myeloneuropathy, dementia and cognitive impairment, cerebellar ataxia, optic atrophy, and psychosis and mood disturbances.  Other than these well-recognized features of B12 deficiency such as macrocytic anemia and neurological disease, more subtle changes have also been described such as osteopenia and cardiovascular disease risk associated with hyperhomocysteinemia.
|Figure 1: Interaction between vitaminB12, folate and homocysteine in one carbon transfer reactions|
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In this case series, we screened patients of megaloblastic anemia with cobalamin deficiency for neurological disease by means of clinical history and examination, psychiatric screening tools, and laboratory and electrophysiological tests to assess the burden of disease. We also sought to determine the cause of B12 deficiency in these patients due to dietary factors, autoimmunity, etc. and to document their response to cobalamin therapy with follow-up.
| Materials and Methods|| |
The study was an observational cross-sectional study conducted at a tertiary care referral hospital in New Delhi over a period of over 2 years from August 2007 to December 2009. Eighty-five consecutive patients with MA due to B12 deficiency were screened and a total of 28 patients with vitamin B12 related neuropsychiatric symptoms were selected for the case series. Written informed consent was obtained from the subjects. A proforma was used to document the clinical presentation and history including dietary factors, drugs and hematinics usage and blood transfusions. This was followed by a detailed clinical examination particularly making note of pallor, jaundice, hepatomegaly, splenomegaly and lymphadenopathy, and other features peculiar to conditions like B12-deficient anemia like hyperpigmentation of skin, knuckles, etc. Standardized neurological examination was performed in all cases with suspected neurological disease including tone, power, deep tendon reflexes, and sensory function, Romberg testing for posterior columns, gait and tandem gait. Improvement with follow-up was also documented at least twice at 3 months and 6 months after diagnosis.
Patients were screened for dementia using mini mental state examination (MMSE). The diagnosis of dementia was established on the basis of diagnostic and statistical manual (DSM IV) criteria.  In addition psychiatric complaints and depression were assessed using validated scoring systems like Beck's depression inventory (BDI) and Beck's anxiety inventory (BAI). ,
Complete blood count (CBC) with a total leukocyte count (TLC), differential count, and red blood cell indices MCV (mean corpuscular volume), MCH (mean corpuscular hemoglobin), MCHC (mean corpuscular hemoglobin concentration) and RDW (red cell distribution width) were estimated using an automatic cell counter MS9 (Autoanalyzer Melet Schloesing Laboratories, USA). A blood film was stained by the Wright stain and evaluated for red cell morphology, band forms, platelet morphology and number, and any atypical cells/parasite. Reticulocyte count using 1% brilliant cresyl blue for supravital staining was done. Liver function tests including liver enzyme levels, renal function tests, serum ferritin and lactate dehydrogenase (LDH) levels were also done in all patients.
Bone marrow examination
Bone marrow aspiration and wherever required, a trephine biopsy was performed in all patients. Further tests were carried out as warranted by the clinical context and the results of baseline investigations.
Vitamin B-12 and folate assays
The vitamins were assayed using liquid chromatography--tandem mass spectroscopy (LC-MS/MS; Instrument 4000 Q TRAP; manufactured by AB Sciex Instruments Model 1022643 G). Blood was collected in BD vacutainers (Becton Dickinson); centrifuged immediately at 2000 g × 10 minutes and serum samples were stored at -70°C till assay was done. The chromatography standard reagent for folic acid was procured from Qualigens Pharmaceuticals and cyanocobalamin from Khemi Labs. The samples were processed to get serum and solid phase extraction was done by mixing 500 μL of sample with 10 μL of internal standard (sildenafil) and processing with solvent acetonitrile and distilled water through solid phase extraction cartridges to procure the test samples for LC and mass spectroscopy. The normal range of cobalamin was 200-700 pg/ml and folate was 5.0-15 ng/ml.
Nerve conduction studies were done in 18 symptomatic patients. Pure tone audiometry was also done in patients of suspect B12 deficiency to evaluate nerve function. Magnetic resonance imaging (MRI) of the brain and/or spinal cord was done in 10 cases. Patients were treated with intramuscular B12 injections (cyanocobalamin, Neurobion forte, Merck) at a dose of 1000 microgram per day for 7 days and then once a week for 1 month and thereafter monthly injections for a minimum follow-up period of 5 months.
The measurements obtained by the above-mentioned studies were used to calculate mean values for each patient and all cases as a whole. Student's test was used for both independent variables. The paired sample t-test was performed to compare the difference of means between groups. P<0.05 was considered significant. Data were analyzed with SPSS software version 13 (SPSS, Chicago, IL).
| Results|| |
The primary study group of MA with B12 deficiency had 85 patients. Of these, only 28 (32.9%) patients had neuropsychiatric features. There were 18 male and 10 female subjects (M: F ratio being 1.8:1). The mean age was 32.80 years with a range of 18-68 years. The majority of patients belonged to lower socioeconomic background (based on income, education, and occupation). Up to 70% of them were educated up to high school.
The patients were noted to have constitutional symptoms like easy fatigability (98%), weight loss (63.5%), fever (58%), swelling of feet (22%), and shortness of breath (27.1%). Many of these patients had symptoms of abdominal fullness (75%), early satiety after meals (88%) which correlated with splenomegaly. The mean duration of symptoms at presentation was 9.8 months (range 2-14 months). All patients were pale, while icterus was seen in 5/28 (17.8%) cases. This also showed a significant correlation with indirect hyperbilirubinemia (P<0.005). Hyperpigmentation of skin, mucous membranes, and knuckles was noted in up to 10.6% and 18.8% of all patients respectively. Glossitis was present in 36.5% patients.
The presenting neurological syndromes included acute febrile delirium, postpartum sepsis with acute confusional state, myeloneuropathy, and myelopathy in two cases each. The most common presentation was distal symmetric neuropathy which was present in 14 cases. Other symptoms included behavioral abnormality in 10 (35.7%), forgetfulness in 14 (50%), paresthesias in 18 (64.2%) and difficulty in walking in 14 patients (50%). Gait disturbance was mainly attributable to sensory ataxia and led to a bed ridden state in four cases. On MMSE, mild-to-moderate cognitive impairment was noted in 20 (71.4%) patients (score 14-28, mean 18.9). Cognitive impairment was associated with behavioral abnormalities in 16/20 (80%) of patients. The behavioral abnormalities included irritability in 10, hallucination in 2, minor depression (as per DSM-IV) in 4, anxiety in 4 and delusion in 1 patient. Four patients with myelopathic symptoms had lower limb spasticity; and all had severe (Medical Research Council MRC grade II-III) weakness. Ankle reflex was absent in 14 patients. Joint position and vibration sense were impaired in 18 cases of suspected neuropathy/myeloneuropathy. We did not find any case of optic atrophy in this series. Beck's depression inventory and anxiety inventory scores were increased in four patients [Table 1].
|Table 1: Laboratory parameters in megaloblastic anemia and B12 deficiency-related neurological syndromes |
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Hematological findings and vitamin assays
The mean hemoglobin (Hb) level in all 18 patients of MA was 5.22 ± 1.62 g/dl. Hypersegmentation of neutrophils was seen in 28.2% and macrocytosis and macroovalocytosis were each seen in 34% of cases. The mean MCV was 95.18 ± 14.71 fl. In the subgroup with neurological disease, mean Hb was 5.31 ± 1.64 g/dl and the degree of macrocytosis (32.1%), hypersegmentation (35.7%) and macroovalocytosis (28.5%) was not significantly different from the whole group. Bone marrow examination confirmed the diagnosis of megaloblastic anemia showing the typical changes of cell: DNA synthesis asynchrony with giant RBC precursors which affected other cell lines as well. Vitamin assays for serum levels of B12, folate, and homocysteine were done [Figure 2] and [Figure 3]. For the purpose of this study, a range of 200-700 pg/ml for vitamin B12 and 5-15 ng/ml for folate was accepted. Mean levels of serum vitamin B12 were lower in cases with neurological disease (124 ± 96.5 pg/ml) than those without (157.58 ± 128.18 pg/ml) but the difference was not statistically significant. Mean serum folate levels were comparable in both groups being 8.87 ± 3.80 ng/ml in all MA and 9.45 ± 4.80 ng/ml in the subset with neurological disease. Cases with folate levels <5 ng/ml were excluded. Serum homocysteine levels could only be done in 38 patients including 20 with neurological disease and was found to be elevated in 36/38 (94.73%) cases. The mean level of homocysteine was 73.66 ± 36.88 μmol/l. In the subset with neurological disease, the mean level was 97.66 ± 42.48 μmol/l in 20/28 cases [Table 2].
|Table 2: Clinical, laboratory and neurophysiological changes in B12 deficiency megaloblastic anemia patients with neurological syndromes (n=28) |
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Correlation of diet with hematological parameters and vitamin assays
Though the majority of MA patients were seen among lacto vegetarians, a good 22% were on a nonvegetarian diet. There were no vegans in this study and very few patients with frequent nonvegetarian intake. The diet of most subjects comprised wheat, rice, pulses, millets, vegetables, and milk. Of the 19 nonvegetarian patients, only 3 consumed meat/poultry/fish products more than twice a week reflecting an insufficient dietary intake of B12. Vitamin B12 levels were found to be higher in the nonvegetarian population though this difference was not statistically significant. The folate and LDH levels were however significantly different between the vegetarian and nonvegetarian, folate being higher and LDH lower in the vegetarian subgroup. Another interesting fact was that 8.2% consumed tobacco and up to 22% of subjects consumed alcohol in this study though it was not significantly more common in the subgroup with neurological disease (P=0.97). Malabsorption work-up was positive in 8/28 patients. Six patients showed rapid transit on barium meal studies and gastric antral biopsy in two of these cases was positive for atrophic gastritis. Both were positive for anti parietal cell antibodies. Two patients were found to have ascariasis. We also assessed the possibility of proton pump inhibitor (PPI) therapy resulting in cobalamin deficiency in this study. A total of 23% patients received PPI drugs and while the mean cobalamin levels were lower in this group, the difference was not statistically significant (P=0.78) [Table 3].
|Table 3: Correlation of diet with laboratory parameters and vitamin assays in B12 deficiency megaloblastic anemia|
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We also performed nerve conduction studies (NCS) in 18 symptomatic individuals to screen for B12-deficient neuropathy. Sensory and motor nerves of nondominant upper and lower extremities were tested. Motor NCS were performed using stimulation of the median nerve, ulnar nerve, peroneal nerve (ankle and below and above the fibular head), and tibial nerve (ankle and popliteal fossa regions). For each motor nerve, distal motor latencies and conduction velocities were obtained or calculated. F wave latencies were obtained from median, peroneal, and tibial nerves. Sensory NCS were performed using the median, superficial peroneal, and sural nerves with sensory nerve action potentials (SNAPS), onset latency, and conduction velocity obtained or calculated. Although all participants completed electrophysiological testing, some subjects do not have complete data for all individual nerves.
Twelve out of these 18 NCSs had evidence of demyelinating peripheral neuropathy and 2 had both axonal and demyelinating changes. Peroneal and tibial nerve conduction was unrecordable in two patients and motor conduction velocity was slowed in 10 of 18 cases. Median and ulnar nerve conduction was slower in eight cases. Sural and superficial peroneal sensory conduction time was also prolonged in 10 cases. Repeat NCS was done in 8 of these 14 patients with peripheral neuropathy after 4 months of B12 therapy, all of which reverted to normal. Pure tone audiometry for cochlear function was also done, but this was normal in all 14 cases. Cochlear microphonic potential studies may be a better tool for screening B12-dependent neural dysfunction [Table 4].
|Table 4: Summary of the nerve conduction studies of patients included in our study (n=18)|
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Magnetic resonance imaging was performed in 10/28 patients. There were four cases with the classical degeneration on spinal MRI with white matter hyperintense lesions in the posterior tracts on T2 weighted images. Two adolescents who presented with febrile delirium with severe anemia also underwent MRI of the brain, but demyelination was seen in only one of these cases which reverted to normal with B12 therapy. Cranial and spinal MRI was also done in two postpartum cases with acute confusional states. In one case, cranial neuroimaging revealed demyelinating white matter lesions attributable to B12 deficiency in the cortical areas but the other case showed no specific changes. Magnetic resonance venography, which was done to exclude cortical vein thrombosis, was clear in both cases. Diffuse cerebral atrophy was seen in two cases with cognitive impairment.
Patients showed improvement in their hematological parameters soon after starting B12 therapy, with resolution of anemic symptoms of shortness of breath, fatigue, abdominal fullness, etc. The mean Hb improved to 12.48 ± 0.97 g/dl at 3 months of B12 therapy. The mean RDW was 16.95 ± 5.60 at presentation which was corrected to 12.56 ± 3.46. S. LDH was found to be elevated in 22/28 (72.58%), the mean levels being 604.85 ± 931.4 IU/l. This improved to 76.86 ± 22.4 IU/l making it a good biochemical marker for documenting response to B12 therapy. At 6-month follow-up, 10/14 patients with neuropathy recovered completely, 2/14 had partial recovery and 2 had poor recovery. All four cases of myelopathy had partial recovery at 6 months, power improving to MRC grades I-II. All four cases with acute confusional state recovered completely. Mean MMSE scores improved by 2.5-21.4 (score 16-28) points in the subset with cognitive impairment. Functional status in performance of activities of daily living had also improved. Patients also reported subjective improvement in their symptoms of memory loss, concentration, paresthesias, and gait abnormalities. Improved mood also correlated with improvement in the BDI and BAI scores of the patients who had depression at presentation. Four patients were lost to follow-up after 6 months.
| Discussion|| |
Vitamin B12 deficiency and neurological manifestations
The main systems affected in B12 deficiency are the hematopoietic bone marrow, the skin, and mucous membranes and the nervous system. Neurological manifestations in MA are attributable to pathological changes in the peripheral nerves, optic nerves, posterior and lateral columns of the spinal cord, and the brain. The classical presentation of subacute combined degeneration of the spinal cord is due to selective vulnerability of particular sets of neurons. B12 deficiency results in changes in cognition and behavior, affect and unusual manifestations in infants (neural tube defects) and adults including movement disorders, seizures and extra pyramidal syndromes.  In our study of B12 deficiency-related neurological syndromes in MA, we found 28/85 patients having neuropsychiatric manifestations including peripheral neuropathy in 14 (50%), myelopathy in 2 (7.14%), myeloneuropathy in 2 (7.14%), acute confusional state in 4 (14.28%), and cognitive impairment in 20 (71.42%) patients in various combinations and permutations. In another study from South India, myeloneuropathy (54%) was the commonest neurological manifestation, followed by myelopathy with cognitive deficiency (34%), peripheral neuropathy (9%), and dementia in 19%.  The higher frequency of cognitive impairment in our case series may be due to the selection criteria. We screened cases of B12-deficient MA for neurological disease. Other studies included cases of B12 deficiency regardless of bone marrow involvement. In a study by Healton et al., patients with B12 deficiency even without neurological signs were included.  In spite of these different criteria, all these studies have shown a high frequency of proprioceptive impairment in B12 deficiency. ,,,
Peripheral neuropathy of the demyelinating type was the most common electrodiagnostic abnormality. Diminished vibratory sensation and proprioception in the lower limbs was observed in these cases. This proprioceptive impairment was detected by abnormal sensory NCS in 14/18 (77.7%) cases in this series. This is consistent with the involvement of the posterior column in the cervicothoracic region in MRI studies of B12-deficient myeloneuropathy. 
Neurological and psychiatric manifestations of B12 deficiency include slow cerebration, confusion, memory changes, delirium, hallucinations, depression, acute psychosis, reversible mania, and schizophreniform state.  Common occurrence of cognitive impairment in our study (71% of MA with neurological features) may have been a result of the use of MMSE for screening for cognitive impairment which identified an additional 20% of patients above the 50% who complained of forgetfulness. Cognitive impairment in our study was associated with behavioral abnormalities in 33% of patients in the form of irritability, hallucinations, depression, anxiety, and delusion. In this study, we noted reversibility of these symptoms with complete recovery of neurological dysfunction in some cases after treatment with vitamin B12. A high prevalence of B12 deficiency has been associated with Alzheimer's disease. However, there is as yet insufficient evidence of any efficacy of vitamin B12 therapy in improving cognitive function in this condition. 
Vitamin B12 deficiency and dietary factors
Vegetarians constituted about 73% of the study population. However we noted a number of young patients on a nonvegetarian diet with B12 deficiency with no other risk factors and a high index of suspicion must be maintained in even in this group in the appropriate clinical scenario. Factors other than dietary deficiency may be responsible for this high prevalence of B12 deficiency which should be the focus of future studies. In our case series, the work-up for malabsortion was positive in eight cases only of which two were cases of pernicious anemia with antiparietal cell antibodies. Tropical sprue, giardiasis, and other gastrointestinal infections such as H. pylori are common in India, and these may lead to malabsorptive states and cobalamin deficiency. Therefore, clinicians need to gauge the underlying etiology for B12 deficiency, whether due to inadequate diet, drug interaction, malabsorption, genetic or familial disease, autoimmunity, etc. 
Diet assessment was done to determine whether a nonvegetarian diet excluded B12 deficiency. Our results indicate otherwise as the consumption of nonvegetarian food was infrequent in our patient population and was found to be inadequate to furnish cobalamin requirements. The role of drug interactions such as proton pump inhibitor intake also needs further investigation.
There is a changing spectrum of anemia in adults in India. Iron deficiency is the most common cause of anemia in adults leading to early detection and treatment of the same. However, megaloblastic anemia is now becoming increasingly common, a large proportion of which is due to vitamin B12 deficiency.  This also presents with numerous neurological manifestations even in the absence of hematological disease like anemia or macrocytosis.  Therefore a high index of suspicion for cobalamin deficiency is needed in patients presenting with features of peripheral neuropathy, myelopathy, cognitive decline, and acute confusional states especially among pure vegetarians and the elderly. 
While folate supplementation and mandatory food fortification has been introduced especially in target groups such as pregnant and lactating mothers, the issue of B12 therapy is largely unaddressed. Newer studies have shown that B12 deficiency is far more widespread than previously believed and in some series grossly outnumbers the folate-deficient MA cases. In addition, groups like nonvegetarians, infants, elderly patients, and even proton pump inhibitor recipients are at risk for B12 deficiency. ,
Vitamin B12 and homocysteine interaction
In our study, hyperhomocysteinemia (>15 μmol/l) was seen in 36/38 (94.7%) of the patients with MA where tests were possible. This is now considered a marker for cobalamin deficiency and correlates with disease states like premature coronary heart disease, renal failure, psychiatric disorders, and cognitive impairment as an independent risk factor. A study carried out in western India reported that 75% of a selected urban population had metabolic evidence (hyperhomocysteinemia and methylmalonic acidemia) consistent with cobalamin deficiency.  Levels of both B 12 and folate have been shown to decrease with age. In the elderly, these predispose to hyperhomocyteinemia and may in turn lead to a decline in cognition and executive functioning.  In a large survey in the United States, Asian Indians were found to have significantly higher homocysteine levels which contributed to insulin resistance and when compared with Caucasians suggesting an ethnic predisposition for hyperhomocysteinemia. 
An increased prevalence of B12 deficiency has been noted with HIV. However these cases were excluded from this study due to the myelosuppressive effect of HIV infection per se and confounding hematological and neuropathic adverse effects of antiretroviral therapy.  Further population-based studies are needed to assess the burden of occult B12 deficiency to decide whether food fortification and routine supplementation can be recommended as is being considered in other countries. , Also the underlying etiology of B12 deficiency needs to be evaluated in future studies, whether due to autoimmune, genetic, gastrointestinal disease or environmental factors. Visual evoked potentials and cochlear microphone potentials may be a more sensitive means of determining preclinical neurological disease and should be incorporated in further research.
| Conclusion|| |
The electrodiagnostic and neuroimaging changes in vitamin B12 deficiency-related neurological syndromes are consistent with focal demyelination of white matter tracts in the brain, the spinal cord, and peripheral nerves. In this case series of B12 deficiency MA, we found demyelinating peripheral neuropathy to be the predominant presenting neurological syndrome. However, on neurological and psychiatric screening and examination, cognitive impairment with behavioral changes was present in a large number of patients who had presented primarily with symptoms due to hematological disease. Conversely, patients with neurological disease may present without hematological abnormalities. Clinicians thus need to assess for B12 deficiency in either scenario as newer studies have shown that occult B12 deficiency is far more widespread than previously believed. Dietary factors, drug interactions, autoimmunity, and malabsorptive states need to be assessed and appropriate treatment and supplementation given. In this case series, we noted a marked reduction of cognitive, behavioral, and neurological dysfunction in response to B12 therapy which further highlights the necessity of assessing and correcting this deficiency in the appropriate clinical setting.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]