A subgroup of COVID-19 patients requires intensive respiratory care. The prolonged immobilization and aggressive treatments predispose these patients to develop intensive care unit-acquired weakness (ICUAW). Furthermore, this condition could increase the chance of positioning-related peripheral nerve injuries. On the basis of the latest literature review, we describe a case series of three patients with COVID-19 who developed ICUAW complicated by positioning-related peripheral nerve injuries Every patient presented sensorimotor axonal polyneuropathy and concomitant myopathy in electrophysiological studies. Furthermore, muscle MRI helped the diagnosis of ICUAW, showing massive damage predominantly in the proximal muscles. Notably, nerve ultrasound detected positioning-related peripheral nerve injuries, even though the concomitant ICUAW substantially masked their clinical features. During the acute phase of severe COVID-19 infection, most medical attention tends to be assigned to critical care management, and neuromuscular complications such as ICUAW and positioning-related peripheral nerve injuries could be underestimated. Hence, when starting post-ICU care for COVID-19 cases, the combination of electrophysiological and imaging studies will aid appropriate evaluation on the patients with COVID-19-related ICUAW.

症例は52歳女性．関節リウマチのためメトトレキサートを使用していた．左手脱力で受診しMRIで大脳の多発性病変が認められ，脳生検にてびまん性大細胞型B細胞リンパ腫が証明された．メトトレキサートの使用歴からメトトレキサート関連リンパ増殖性疾患（methotrexate associated lymphoproliferative disorders; MTX-LPD）と診断された．MTX-LPDはMTX休薬のみで改善することが特徴とされるが本例では改善はなく，化学療法の効果も限定的で死に至った．中枢神経のMTX-LPDは非常に稀であるが，免疫抑制剤使用中の合併症の一つとして認知しておく必要がある．

Primary neurolymphomatosis (NL) is a critical differential diagnosis of asymmetric multiple mononeuropathy and radiculoplexopathy. Its diagnosis is often challenging due to the lack of typical clinical signs of systemic lymphoma. We report a case of primary NL where nerve ultrasound (NUS) played an important role in the diagnosis and follow-up of the disease. A 52-year-old man developed asymmetric painful multiple mononeuropathy in the right upper limb with cranial nerve involvement. After being referred to our department, the patient underwent NUS, which revealed marked enlargement and increased vascularity in the right upper limb nerves, brachial plexus, and cervical nerve roots. Furthermore, an epineural hypoechoic mass, a characteristic finding of NL, was seen in the right median nerve. These NUS findings prompted us to perform 18F-fluorodeoxyglucose positron emission tomography/computed tomography and a subsequent biopsy on the right axillary lymph node, confirming NL. Notably, the NUS abnormalities dramatically subsided, demonstrating the effectiveness of chemotherapy. The diagnostic utility of NUS for NL has been documented by many recent reports. Additionally, NUS can work as a quick follow-up tool for NL, as seen in our case.

The European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) classification criteria for idiopathic inflammatory myopathies (IIM) have been widely used in recent times. However, no studies have focused on electromyography (EMG) findings of IIM, considering the criteria. This study aimed to elucidate the frequency of EMG abnormalities, particularly fibrillation potentials and positive sharp waves (Fib/PSW), the most objective EMG findings of IIM. Clinical and EMG records of adult patients who were clinically diagnosed with polymyositis (PM), dermatomyositis (DM), amyopathic DM (ADM), or inclusion body myositis (IBM) were retrospectively reviewed and classified according to the EULAR/ACR classification criteria. The frequency of Fib/PSW in EMG was investigated in the recruited cases. Seventy-nine patients with clinically diagnosed IIM (44 with PM, 17 with DM, 7 with ADM, and 11 with IBM) were recruited. After classification using EULAR/ACR, 75 satisfied definite or probable IIM (61 and 14, respectively), and the frequency of Fib/PSW in this group was 95%. Furthermore, the remaining 4 patients with insufficient IIM probability also showed Fib/PSW. Fib/PSW may also be seen in cases with insufficient IIM probability not satisfying the criteria. EMG may help detect muscle involvement in these cases through Fib/PSW.