The branchial arches are the embryological precursors of the face, neck and pharynx. Anomalies of the branchial arches are the second most common congenital lesions of the head and neck in children, with second branchial arch anomalies by far the most common. Clinically, these congenital anomalies may present as cysts, sinus tracts, fistulae or cartilaginous remnants with typical clinical and radiological findings. We review the normal embryological development of the branchial arches and the anatomical structures of the head and neck that derive from each arch. The typical clinical and radiological appearances of both common and uncommon branchial arch abnormalities are discussed with an emphasis on branchial cleft anomalies.Key points• Anomalies of the branchial arches usually present as cysts, sinuses or fistulae.• Second branchial arch anomalies account for approximately 95 % of cases.• There are no pathognomonic imaging features so diagnosis depends on a high index of suspicion and knowledge of typical locations.• Persistent cysts, fistulae or recurrent localised infection may be due to branchial arch anomalies.• Surgical excision of the cyst or tract is the most common curative option.

BackgroundWhilst the dangers of ‘legal highs’ have been widely publicised in the media, very few cases of the neurological syndrome associated with the inhalation of nitrous oxide (N2O) have been reported. Here we set out to raise awareness of subacute degeneration of the spinal cord arising from recreational N2O use so that formal surveillance programs and public health interventions can be designed.MethodsCase series documenting the clinical and investigational features of ten consecutive cases of subacute degeneration of the spinal cord presenting to a hospital with a tertiary neurosciences service in East London.ResultsSensory disturbance in the lower (± upper) limbs was the commonest presenting feature, along with gait abnormalities and sensory ataxia. MRI imaging of the spine showed the characteristic features of dorsal column hyperintensity on T2 weighted sequences. Serum B12 levels may be normal because subacute degeneration of the spinal cord in this situation is triggered by functional rather than absolute B12 deficiency.DiscussionA high index of suspicion is required to prompt appropriate investigation, make the diagnosis and commence treatment early. This is the largest reported series of patients with subacute degeneration of the spinal cord induced by recreational use of N2O. However, the number of patients admitted to hospital likely represents the ‘tip of the iceberg’, with many less severe presentations remaining undetected. After raising awareness, attention should focus on measuring the extent of the problem, the groups affected, and devising ways to prevent potentially long-term neurological damage.

IIH is a protean syndrome caused by various potential (risk and) associative factors. Several conditions could influence the pressure regulation of CSF. An endocrine-metabolic altered homeostasis could be suggested in some IIH patients, and in this context, etiologically targeted therapies (spironolactone) should be considered.