Succinate dehydrogenase mutations: paraganglioma imaging and at-risk population screening.

Paragangliomas are rare vascular tumours of the autonomic nervous system. They can be classified as sympathetic or parasympathetic. Sympathetic paragangliomas, which include phaeochromocytomas, tend to be functional and symptomatic. Parasympathetic paragangliomas are usually non-functional and may present with mass effect. Forty percent of paragangliomas are linked to genetic syndromes, most commonly due to mutations of the succinate dehydrogenase (SDH) enzyme complex and are collectively known as paraganglioma syndromes, of which five are described. Genetic testing is recommended for all patients, and their first-degree relatives, diagnosed with paragangliomas. When SDH mutations are discovered, biochemical screening and imaging surveillance is indicated. There is currently no consensus on imaging surveillance protocols. Most advocate full-body imaging, but the choice of technique and frequency varies. If paragangliomas are demonstrated, functional imaging to look for synchronous tumours or metastases is indicated. 2-[18F]-fluoro-2-deoxy-d-glucose (18F-FDG) positron-emission tomography (PET)-computed tomography (CT) is the technique of choice for metastatic evaluation, but [123I]-metaiodobenzylguanidine or [111In]-DTPA-octreotide scintigraphy are also utilised. Current research into emerging positron-emitting radiolabelled somatostatin analogues have yielded promising results, which is likely to be reflected in future guidelines. As genetic testing becomes increasingly prevalent, the need to answer the remaining questions regarding surveillance imaging is paramount.

MRI ankle and subtalar characteristics in haemochromatosis arthropathy: a case-control study.

AIM: To examine the magnetic resonance imaging (MRI) features of the ankle and subtalar joints that might distinguish genetic haemochromatosis (GH). MATERIALS AND METHODS: The present study was a retrospective case-control study comparing 30 MRI studies of GH patients with ankle or subtalar arthropathy with 30 matched controls with ankle pain. Anonymised images were scored using a semi-quantative tool adapted from the MRI osteoarthritis knee score. Scores were generated for bone marrow lesions size, number, and distinguishing the proportion of each lesion consisting of subchondral cyst versus oedema. Articular cartilage loss and osteophytes were documented. The primary comparator was bone marrow lesion size. Paired Student's t-test and the chi-squared test were utilised to compare outcomes. RESULTS: Bone marrow lesion/cyst size and number, presence and extent of full-thickness cartilage loss, and osteophyte scores were significantly higher in ankle joints of GH cases (p<0.01). In the middle subtalar articulation, there were significantly higher scores for full-thickness cartilage loss and extent and osteophytes in GH cases (p<0.05). There were no significant differences in the posterior subtalar articulation. CONCLUSION: The finding of both numerous and large cysts on ankle MRI should raise suspicion of GH. Other MRI features of potential diagnostic value include large osteophytes and the presence of extensive full-thickness cartilage loss in the ankle joint and middle subtalar articulation.