No abstract

Nitrous oxide, also known as ‘laughing gas’, is one of the most widely used recreational drugs among teenagers in the UK. Copious inhalation of nitrous oxide may increase intra-alveolar pressure, resulting in barotrauma secondary to alveolar rupture. Pneumomediastinum and subcutaneous emphysema are common clinical findings in nitrous oxide-associated barotrauma. Prolonged nitrous oxide misuse may inactivate vitamin B12 through the alteration of its metabolism, causing demyelination of the central and peripheral nervous system. A spectrum of neurological manifestations has been reported, including peripheral neuropathy, myelopathy and subacute combined degeneration of the spinal cord. Medical therapies and psychosocial interventions aiming at nitrous oxide cessation are important treatment steps to achieve partial or complete recovery from the adverse effects associated with inhalation of nitrous oxide.

Metatarsalgia is a common clinical conundrum that requires careful assessment. There are a variety of causes and understanding these can help manage the pain. These causes have different imaging characteristics and require specific imaging. By understanding core imaging principles and how they apply to causes of metatarsalgia, pathology can be more efficiently investigated. This article covers primary, secondary and iatrogenic causes of metatarsalgia with the most appropriate imaging modalities for each and the salient imaging findings. This article reviews the common forefoot pathologies and how they may be optimally radiologically investigated, with an emphasis on the key imaging findings.