Frequency of EMG abnormalities in idiopathic inflammatory myopathies under the EULAR/ACR classification criteria.

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.

Evaluation of diagnostic yield of the 2021 European Academy of Neurology/Peripheral Nerve Society diagnostic criteria for CIDP.

INTRODUCTION/AIMS: It is unclear whether the revised European Academy of Neurology/Peripheral Nerve Society diagnostic criteria (EAN/PNS 2021 criteria) improved the diagnostic yield for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) compared with the previous version. Therefore, this study aimed to compare the sensitivity and specificity of the EAN/PNS 2021 criteria and the European Federation of Neurological Societies/Peripheral Nerve Society 2010 diagnostic criteria (EFNS/PNS 2010 criteria), with a specific focus on the electrodiagnostic criteria. METHODS: Data of patients with clinically suspected CIDP who exhibited objective treatment response, and of those with chronic axonal neuropathies, obtained between 2009 and 2021, were extracted retrospectively from our database. Patients who underwent nerve conduction studies in at least unilateral upper and lower extremities were enrolled. We compared the sensitivity and specificity of the EAN/PNS 2021 and EFNS/PNS 2010 criteria. RESULTS: In total, 55 patients with clinically suspected CIDP and 36 patients with chronic axonal neuropathies were enrolled. When considering the "possible CIDP" category, the EAN/PNS 2021 criteria showed lower sensitivity than the EFNS/PNS 2010 criteria (78% vs. 93%, p < .05), whereas its specificity was higher (78% vs. 61%, p < .05). The lower sensitivity was caused mainly by the failure to fulfill the sensory nerve conduction criteria. The revised definition of abnormal temporal dispersion of the tibial nerve contributed markedly to the improved specificity. DISCUSSION: To improve the sensitivity of the EAN/PNS 2021 criteria, increasing the number of tested sensory nerves may be necessary.

Guillain-Barré Syndrome Mimicking Lumbar Spinal Stenosis with Segmental Weakness in L5-S1 Myotomes: Two Case Reports.

We herein report two cases of Guillain-Barré syndrome (GBS) mimicking lumbar spinal stenosis (LSS). Both cases were initially diagnosed as LSS based on prominent segmental weakness in the L5 and S1 myotomes and coexisting LSS on magnetic resonance imaging. However, neurological and electrophysiological examinations revealed abnormalities that extended to the upper extremities, although slight, prompting us to suspect GBS. Subsequently, serum antiganglioside antibodies and remarkable responsiveness to intravenous immunoglobulin therapy confirmed GBS. We suspect that the focal blood-nerve barrier disruption due to preexisting LSS might have contributed to the segmental weakness in this atypical GBS case.

[A case of acute bilateral blindness presumably caused by reversible cerebral vasoconstriction syndrome after traumatic brain injury].

A 62-year-old man was admitted to our hospital for acute bilateral blindness two days after a head injury. Hemorrhagic cerebellar infarction was found on the initial MRI, and peripheral arteries were poorly visualized on MRA. On the follow-up MRA nine days later, peripheral arteries were clearly depicted. These imaging findings suggested reversible cerebral vasoconstriction syndrome (RCVS). We started steroid pulse therapy for suspected optic neuritis with no clear response. The initial fundoscopic examination revealed no abnormalities in the optic disc, but optic nerve atrophy developed one month later. Based on the course of events, we diagnosed the patient with posterior ischemic optic neuropathy triggered by RCVS.

Different Tendencies in Muscle Ultrasound Characteristic in Amyotrophic Lateral Sclerosis and Chronic Inflammatory Demyelinating Polyradiculoneuropathy.

INTRODUCTION: The difference in muscle ultrasound (MUS) characteristics in primary axonal degeneration and demyelination has not been well established. The authors aimed to investigate the subject based on the correlation between MUS findings (echo intensity and muscle thickness) and compound muscle action potential (CMAP) amplitude in amyotrophic lateral sclerosis (ALS) and chronic inflammatory demyelinating polyradiculoneuropathy. METHODS: Fifteen patients with ALS and 16 patients with chronic inflammatory demyelinating polyradiculoneuropathy were examined. For each patient, echo intensity and muscle thickness of the abductor pollicis brevis, abductor digiti minimi, and first dorsal interosseous muscles were investigated. Compound muscle action potential amplitudes were measured by median and ulnar nerve conduction studies. RESULTS: In total, 45 muscles were evaluated in each group. The ALS group showed a linear correlation between the MUS finding and CMAP amplitude (rs = -0.70 and 0.59 for echo intensity and muscle thickness, respectively), whereas the chronic inflammatory demyelinating polyradiculoneuropathy group showed a weaker correlation than the ALS group (rs = -0.32 for echo intensity and rs = 0.34 for muscle thickness). CONCLUSIONS: The relationship between MUS abnormalities and CMAP amplitude showed different tendencies in ALS and chronic inflammatory demyelinating polyradiculoneuropathy. The results suggested that MUS abnormalities substantially reflect the muscle function in primary axonal degeneration, whereas a discrepancy between MUS findings and muscle function can be frequently seen in demyelination; specifically, MUS findings tend to be normal even though CMAP showed a reduction. These tendencies originating from underlying pathophysiology should be considered when MUS findings are used as biomarkers of disease severity.

Utility of nerve ultrasound in the management of primary neurolymphomatosis: Case report and review of the literature.

Introduction: 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. Case presentation: 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. Discussion: 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.

Tibial nerve SEPs in diagnosing lumbar spinal stenosis: The utility of segmental evaluation using P15 and N21.

Objective: To establish the utility of the additional evaluation of the P15 potential generated at the greater sciatic foramen in the tibial nerve somatosensory evoked potentials (SEPs) in diagnosing lumbar spinal stenosis (LSS). Methods: We retrospectively reviewed tibial nerve SEP findings in patients having MRI-confirmed LSS at the cauda equina or conus/epiconus region. P15 and N21 potentials were recorded and the following findings were defined as localizing abnormalities: 1) normal P15 latency either with prolonged P15-N21 interval or with absent N21; 2) decreased ratio of the N21 amplitude to P15 amplitude. As non-localizing abnormalities, N21 and P38 latencies were also evaluated. Tibial nerve F-wave findings were also investigated. Results: According to the entry criteria, 18 patients were included, 15 with cauda equina lesions and 3 with conus/epiconus lesions. Localizing abnormalities in SEPs were found in 67% of patients, achieving significantly higher sensitivity than delayed P38 latency (28%), and higher sensitivity than N21 abnormalities (39%), though this was not significant. Localizing abnormalities were observed even in 6 out of 11 patients lacking both sensory symptoms and signs. Tibial nerve F-wave was abnormal in 36% of 14 patients with F-wave examinations, whereas the localizing abnormalities in SEPs were found in 64% of the same patient population. P15 amplitude was depressed in 4 patients (22%), which may indicate the involvement of the dorsal root ganglion in LSS, although its latency was normal even for these patients. Conclusions: Tibial nerve SEPs with the recording of P15 and N21 potentials achieved sufficiently high sensitivity in diagnosing LSS. They have the advantage over F-wave in that they can localize the lesion at the cauda equina or conus/epiconus level. Significance: Tibial nerve SEPs are promising in evaluating LSS, especially in documenting sensory tract involvement in cases lacking sensory symptoms/signs.

Utility of the tibial nerve somatosensory evoked potentials in differentiating between neuromyelitis optica spectrum disorders and multiple sclerosis.

BACKGROUND: Somatosensory evoked potentials (SEPs) are widely used for the diagnosis and evaluation of neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS). However, whether the parameters of tibial nerve SEPs can help to distinguish NMOSD from MS remains unclear. Thus, the aim of this study was to investigate the utility of tibial nerve SEP parameters in differentiating patients with NMOSD and MS. METHODS: The clinical data of patients with NMOSD or MS treated in our institution between 2005 and 2021 were retrospectively extracted from our electronic database. Additional inclusion criteria were presentation with sensory symptoms in the lower extremities with corresponding lesions in the magnetic resonance images as well as available data on anti-aquaporin-4 antibodies and tibial nerve SEPs. The Z-scores of the N21-P38 interval (central sensory conduction time), P38 latency, and P38 amplitude were compared between the patients with NMOSD and MS. The relationship of disease severity with the parameters of the tibial nerve SEPs was also evaluated. RESULTS: Twenty patients with NMOSD and 13 patients with MS were enrolled. The Z-scores of the N21-P38 interval and P38 latency were significantly higher in the MS group than in the NMOSD group (p < 0.05 and p < 0.01, respectively), whereas there was no difference in the Z-scores of the P38 amplitude between the two groups. In the MS group, only the N21-P38 interval and P38 latency were significantly correlated with disease severity (p < 0.05 and p < 0.01, respectively). In contrast, none of the tibial nerve SEP parameters were significantly correlated with disease severity in the NMOSD group. CONCLUSION: Evaluation of the N21-P38 interval and P38 latency in tibial nerve SEPs potentially helps in differentiating between NMOSD and MS.

Intensive Care Unit-Acquired Weakness and Positioning-Related Peripheral Nerve Injuries in COVID-19: A Case Series of Three Patients and the Latest Literature Review.

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.

Determining C5, C6 and C7 myotomes through comparative analyses of clinical, MRI and EMG findings in cervical radiculopathy.

OBJECTIVE: There are many myotome charts in the literature, but few studies have presented actual data to support their identification. We aimed to determine C5/C6/C7 myotomes based on clinical and EMG data of patients with cervical spondylotic radiculopathy (CSR) having a single-root lesion confirmed by MRI. METHODS: Medical Research Council (MRC) scores and EMG findings were retrospectively reviewed for patients enrolled from our EMG database. RESULTS: Enrolled were 25 patients (10 C5, 6 C6, and 9 C7 CSR). In C5 CSR, weakness or denervation potentials in EMG, or both, were observed in the deltoid (Del) and infraspinatus (Isp) muscles for all patients, and in the biceps brachii (BB) and brachioradialis (BR) muscles for 9/10 and 8/9 patients, respectively. In C6 CSR, weakness of the wrist extensor and/or denervation of the extensor carpi radialis longus (ECRL)/extensor carpi radialis brevis (ECRB), and those of the pronator teres (PT) were observed for all patients. Weakness was not observed for any other muscle in C6 CSR. Denervation potentials of ECRL were found in 5/8 and 3/5 patients with C5 and C6 CSR, respectively, whereas those of ECRB were found in 1/5, 6/6, and 2/5 patients with C5, C6 and C7 CSR, respectively. In C7 CSR, weakness/denervation of the triceps brachii (TB) and denervation potentials of the flexor carpi radialis (FCR) were observed for all patients. Denervation potentials in PT and weakness/denervation of the extensor digitorum (ED) were observed in 2/9 and 4/9 patients, respectively. CONCLUSION: Suggested dominant myotomes are: C5 for the Del, Isp, BB, and BR, C5/6 for the ECRL, C6 > C7 for the ECRB and PT, and C7 for the TB and FCR. SIGNIFICANCE: The current study identified dominant myotomes that differ from the existing literature.

Appropriate window width for the "clustering index method" in the tibialis anterior muscle.

We previously reported a new quantitative analysis of single-channel surface electromyography (EMG), the "clustering index method" (CI method), in the tibialis anterior muscle, which achieved sufficiently good sensitivity to detect neurogenic or myogenic abnormalities. The window width is a fundamental parameter of the CI method, and was arbitrarily set at 15 ms in that study. In this study, we searched for the most appropriate window width using expanded patient data. The data from our previous study were reanalyzed, and new patients were enrolled. Window width in the CI method was changed from 5 to 27.5 ms with a step of 2.5 ms. For each window width, Z-score values of individual subjects were calculated and the diagnostic yield was investigated. We enrolled 67 controls, 29 subjects with neurogenic disorders, and 39 with myogenic disorders. When the window width was set at 22.5 ms, the highest sensitivity was achieved both for neurogenic (97%) and myogenic (72%) disorders, with a specificity of 97%. Seven of 10 patients with inclusion body myositis were also abnormal. Reliable results were obtained by collecting 15 epochs per subject. There are two conflicting effects that appear to be best balanced at a window width of 22.5 ms: a wider width decreases the chance that a motor unit potential (MUP) is divided into two adjacent windows, and a narrower width reduces the possibility that an MUP firing at a low-frequency is counted twice by the differential sequences. CI is promising as a non-invasive method to diagnose neuromuscular disorders.

Updated size index valid for both neurogenic and myogenic changes.

BACKGROUND: Size index (SI) is a motor unit potential (MUP) parameter in concentric needle electromyography calculated from amplitude and area/amplitude, which can sensitively discriminate between control and neurogenic MUPs. In this study, we investigated the application of SI to myogenic MUPs based on expanded data. METHODS: MUPs were collected from the biceps brachii (BB) and tibialis anterior (TA) muscles. Muscles showing unequivocal neurogenic or myogenic changes by visual inspection were selected for patients. In addition to the original SI, a revised SI (rSI) was defined using the logarithmic scale for area/amplitude. The coefficient for area/amplitude was varied and that achieving the best sensitivity both for BB and TA was selected. RESULTS: Analyzed were 1619, 340, and 498 MUPs from the BB of 26, 10, and 14 subjects (control, neurogenic, and myogenic), respectively, and 1245, 536, and 473 MUPs from the TA of 23, 18, and 13 subjects (control, neurogenic, and myogenic), respectively. For neurogenic MUPs, the original SI and the newly defined rSIn were similarly sensitive (82.1% and 81.8% sensitivity for SI and rSIn, respectively, for BB, and 68.1% and 69.6% for TA), and were more sensitive than area (72.6% for BB and 57.6% for TA), the most sensitive parameter among conventional ones. For myogenic MUPs, the sensitivity of rSIm was 9.0% for BB and 24.5% for TA, which was not significantly different from duration (7.4% for BB and 21.8% for TA), the most sensitive parameter among conventional ones. CONCLUSIONS: SI, rSIn, and rSIm are promising as new MUP parameters.

[Severe sensory-motor axonal neuropathy following diabetic ketoacidosis].

We report a case of severe sensory-motor axonal neuropathy on the lower extremities associated with diabetic ketoacidosis (DKA). A sixteen-year-old boy developed coma and admitted to our hospital. We diagnosed him with DKA based on remarkable hyperglycemia, severe acidosis with hyperketonemia. Intensive glycemic control with insulin was immediately started. He had complications of heart failure, rhabdomyolysis, and renal failure, which required intensive care including mechanical ventilation and hemodialysis. When recovered from the critical condition, he noticed severe weakness, numbness, and pain on the lower limbs, and urinary retention. On nerve conduction studies, both motor and sensory action potentials were absent. Serum anti-ganglioside antibodies were negative. Albuminocytologic dissociation was evident in the cerebrospinal fluid. MRI study revealed marked gadolinium enhancement of the cauda equina. After high-dose intravenous immunoglobulin treatment, he was relieved from leg pain, but the leg weakness and bladder bowel dysfunction did not show immediate improvement. It took approximately six months until he became able to stand and walk using ankle orthosis. Acute neuropathy is a rare complication of diabetes mellitus. Painful neuropathy is known to emerge in association with diabetic treatment, but it seldom causes severe motor disturbance. On the other hand, motor-dominant polyneuropathy has been reported to occur acutely along the treatment of DKA and hyperosmolar hyperglycemia syndrome (HHS). Present case and previous cases with DKA and HHS suggest that rapid correction of glucose level is one of the underlying factors of acute neuropathy related with diabetic treatment.

[Primary central nervous system methotrexate associated lymphoproliferative disorders in a patient with rheumatoid arthritis].

We report on a 52-year-old woman with rheumatoid arthritis (RA) who developed methotrexate associated lymphoproliferative disorders (MTX-LPD) in the central nervous system (CNS) in the course of immunosuppressive therapy for RA. The patient was admitted because of monoplegia in her left hand. She had been receiving methotrexate (MTX) for her RA for several years and etanercept had also been introduced because of a worsening of the arthritis six months before admission. Brain MRI revealed multiple lesions with enhancement scattered throughout both hemispheres. 18F-fluorodeoxyglucose-positron emission tomography/computed tomography showed abnormal accumulation suggesting malignancy in the right frontal lobe where abnormal enhancement was observed on the MRI. A brain biopsy was performed at the identified site and it confirmed diffuse large B-cell lymphoma (DLBCL). We therefore diagnosed her as MTX-LPD. According to previous reports, most MTX-LPD cases tend to show regression after the cessation of MTX. However, our case showed no regression and even needed chemotherapy. The patient had a poorer prognosis than previous cases and died 17 months after the onset. Although it is an uncommon complication, particularly in the CNS, MTX-LPD should be considered as a critical differential diagnosis if a patient receiving MTX develops central nervous system lesions. Immediate medical intervention including brain biopsy is required.