Vitamin B12, cobalamin, is indispensable for humans owing to its participation in two biochemical reactions: the conversion of l-methylmalonyl coenzyme A to succinyl coenzyme A, and the formation of methionine by methylation of homocysteine. Eukaryotes, encompassing plants, fungi, animals and humans, do not synthesise vitamin B12, in contrast to prokaryotes. Humans must consume it in their diet. The most important sources include meat, milk and dairy products, fish, shellfish and eggs. Due to this, vegetarians are at risk to develop a vitamin B12 deficiency and it is recommended that they consume fortified food. Vitamin B12 behaves differently to most vitamins of the B complex in several aspects, e.g. it is more stable, has a very specific mechanism of absorption and is stored in large amounts in the organism. This review summarises all its biological aspects (including its structure and natural sources as well as its stability in food, pharmacokinetics and physiological function) as well as causes, symptoms, diagnosis (with a summary of analytical methods for its measurement), prevention and treatment of its deficiency, and its pharmacological use and potential toxicity.

Patients with neuropathic pain are heterogeneous in pathophysiology, etiology, and clinical presentation. Signs and symptoms are determined by the nature of the injury and factors such as genetics, sex, prior injury, age, culture, and environment. Basic science has provided general information about pain etiology by studying the consequences of peripheral injury in rodent models. This is associated with the release of inflammatory cytokines, chemokines, and growth factors that sensitize sensory nerve endings, alter gene expression, promote post-translational modification of proteins, and alter ion channel function. This leads to spontaneous activity in primary afferent neurons that is crucial for the onset and persistence of pain and the release of secondary mediators such as colony-stimulating factor 1 from primary afferent terminals. These promote the release of tertiary mediators such as brain-derived neurotrophic factor and interleukin-1β from microglia and astrocytes. Tertiary mediators facilitate the transmission of nociceptive information at the spinal, thalamic, and cortical levels. For the most part, these findings have failed to identify new therapeutic approaches. More recent basic science has better mirrored the clinical situation by addressing the pathophysiology associated with specific types of injury, refinement of methodology, and attention to various contributory factors such as sex. Improved quantification of sensory profiles in each patient and their distribution into defined clusters may improve translation between basic science and clinical practice. If such quantification can be traced back to cellular and molecular aspects of pathophysiology, this may lead to personalized medicine approaches that dictate a rational therapeutic approach for each individual.

Levodopa-carbidopa intestinal gel infusion (LCIG) is an established therapy for advanced Parkinson disease (PD), resulting in a significant improvement of quality of life. With increased LCIG adoption worldwide, potential complications due to abnormal vitamin absorption or metabolism have been reported in these patients. Neurologists are unfamiliar with vitamins physiology and pathophysiological mechanisms in case of their deficiency. Unfortunately, clinical and laboratory guidelines related to vitamin monitoring and supplementation in the context of treatment with LCIG are not available. We herein summarize the current knowledge on three vitamins that are reduced with LCIG therapy reporting on their physiology, laboratory testing, and clinical impact of their deficiency/excess. In addition, we proposed an opinion-based recommendation for clinicians treating LCIG patients. Patients and caregivers should be informed about the risk of vitamin deficiency. Vitamin B12, homocysteine, and methylmalonic acid (MMA) should be tested before starting LCIG, six months after and once/year thereafter. Vitamin B6 and folate testing is not universally available but it should be considered if homocysteine is elevated but MMA and/or total vitamin B12 are normal. Prophylaxis of vitamin deficiency should be started as soon as LCIG is implemented, possibly even before. Dietary recommendations are enough in most patients although a subgroup of patients is at higher risk and should receive Vitamin B12 regularly and cycles of B6. Finally, once diagnosed a vitamin deficiency should be readily treated and accompanied by clinical and laboratory monitoring. Resistant cases should receive non-oral routes of administration and possibly discontinue LCIG, even temporarily.

The World Cancer Research Fund and American Institute for Cancer Research (WCRF/AICR) advise cancer survivors to follow their lifestyle recommendations for cancer prevention. Adhering to these recommendations may have beneficial effects on patient-reported outcomes after a cancer diagnosis, but evidence is scarce. We aimed to assess associations of the individual dietary WCRF/AICR recommendations regarding fruit and vegetables, fibre, fast foods, red and processed meat, sugar-sweetened drinks and alcohol consumption with patient-reported outcomes in colorectal cancer (CRC) survivors. Cross-sectional data of 150 stage I–III CRC survivors, 2–10 years post-diagnosis, were used. Dietary intake was measured by 7-d dietary records. Validated questionnaires were used to measure health-related quality of life (HRQoL), fatigue and neuropathy. Confounder-adjusted linear regression models were used to analyse associations of each WCRF/AICR dietary recommendation with patient-reported outcomes. Higher vegetable intake (per 50 g) was associated with better global QoL (β 2·6; 95 % CI 0·6, 4·7), better physical functioning (3·3; 1·2, 5·5) and lower levels of fatigue (−4·5; −7·6, −1·4). Higher fruit and vegetables intake (per 100 g) was associated with better physical functioning (3·2; 0·8, 5·5) and higher intake of energy-dense food (per 100 kJ/100 g) with worse physical functioning (−4·2; −7·1, −1·2). No associations of dietary recommendations with neuropathy were found. These findings suggest that adhering to specific dietary WCRF/AICR recommendations is associated with better HRQoL and less fatigue in CRC survivors. Although the recommendations regarding healthy dietary habits may be beneficial for the well-being of CRC survivors, longitudinal research is warranted to gain insight into the direction of associations.

Introduction: Lewis–Sumner syndrome (LSS) is a demyelinating peripheral neuropathy described in 1982. Methods: We reviewed the charts of nine LSS patients in neurological care for their symptoms, response to different treatment regimens, and pattern of nerve involvement. Results: One patient had an Adie’s pupil. Every patient studied had median nerve involvement. Seven of nine patients required intravenous immunoglobulin (IVIg) therapy and all showed improvement with IVIg. Four of nine patients received oral steroid therapy and had some improvement. Two of nine patients received azathioprine to little effect. Two of nine patients experienced significant trauma while receiving neurological follow-up and their symptoms worsened to a clinically significant degree afterward. Discussion: We noticed a possible association between trauma and symptom severity in cases of LSS with preexisting neurological follow-up. We hypothesize that physical trauma exacerbates LSS. To our knowledge, this is an unreported phenomenon.