Electrophysiologic evaluation of myasthenia gravis and its mimics: real-world experience with single-fiber electromyography.

OBJECTIVES: In centers which routinely perform single fiber electromyography (SFEMG) for suspected myasthenia gravis (MG), the additional benefit of other neurophysiologic investigations and the frequency of myasthenia mimics has not been ascertained. We aimed to illustrate the range of neurological and non-neurological myasthenia mimics referred for evaluation, and contrast features of their electrophysiologic evaluation with confirmed MG. METHODS: We reviewed all SFEMG studies performed at our center between 1 January 2018 and 31 December 2020. Patient demographics, clinical phenotype, antibody status and final diagnosis were recorded. Electrophysiologic findings were correlated with clinical features and sensitivity analyses performed. RESULTS: A total of 528 SFEMG studies were performed, of which 213 (41%) were abnormal. A diagnosis of MG was made in 101 individuals, including 46 with ocular MG and 35 with seronegative disease. Compared to myasthenia mimics with an abnormal SFEMG, individuals with MG had higher median jitter (mean consecutive difference 61 µs vs. 42 µs, p < 0.001) and a greater percentage of abnormal pairs (61% vs. 33%, p < 0.001) on SFEMG. Repetitive nerve stimulation was abnormal in 27.1% of people with MG and was associated with a generalized clinical phenotype (OR 4.17; 95% CI 1.67-10.48). Thirteen (2%) individuals with MG had normal SFEMG, of whom 10 were in clinical remission. Functional neurological disorders, cranial nerve palsies, primary ocular disease and myopathy were frequent myasthenia mimics. CONCLUSION: SFEMG can be abnormal in a number of myasthenia mimics, and routine nerve conduction studies and electromyography should always be undertaken. In centers where SFEMG is performed routinely for the investigation of suspected MG, extensive proximal repetitive nerve stimulation can be foregone without substantially affecting diagnostic evaluation. Normal SFEMG in those with confirmed myasthenia gravis may help indicate clinical remission.

Posterior reversible leukoencephalopathy syndrome: Case series and review of the literature. / Síndrome de leucoencefalopatía posterior reversible: serie de casos y revisión de la literatura.

OBJECTIVE: To describe clinical manifestations, antecedents, comorbidities and associated treatments, imaging findings, and follow-up in patients with posterior reversible encephalopathy syndrome. METHODS: A retrospective, descriptive analysis of admitted patients was performed between June 2009 and May 2014 in a third-level care hospital. We evaluated age, sex, comorbidities, symptoms, values of blood pressure at admission, renal function, medication and time elapsed until the disappearance of symptoms. RESULTS: Thirteen patients were included. In all, 77% of them had a history of hypertension at baseline and 85% had impaired renal function. The most prevalent comorbidity was renal transplantation, and 85% had deterioration of renal function. Five of the patients had undergone renal transplantation. The most common clinical manifestation was seizures. All had subcortical lesions and bilateral parietooccipital involvement was the finding most frequently observed. CONCLUSION: This syndrome should be taken into account in the differential diagnoses of patients presenting with acute neurological syndromes and the abovementioned risk factors.