Polymyositis with cytochrome C oxidase negative fibers--a pathological and clinical challenge.

Polymyositis (PM) with cytochrome C oxidase negative fibers also referred to as PM with mitochondrial pathology (PM-Mito) is characterized by the symptoms of inclusion body myositis (IBM) and by the myopathological findings of PM except for an increase of muscle fibers with insufficient mitochondrial cytochrome C oxidase activity. Few PM-Mito cases are published; mitochondrial ultrastructure has not been studied in these patients. We report 2 PM-Mito patients with later onset than usually seen in IBM and poor responsiveness to glucocorticoids. Electron microscopy of muscle fibers showed irregular mitochondrial ultrastructure. Sjögren syndrome related antinuclear antibodies (Anti-Ro and Anti-La) were found in one of the two patients but the typical clinical symptoms of Sjögren syndrome such as xerostomia and keratoconjunctivitis were absent in this patient. Taken together, our observations, viewed in conjunction with the current literature, suggest that PM-Mito is an underdiagnosed disease with a multifactorial pathogenesis that should be elucidated in further studies. We want to encourage clinicians and pathologists to consider the possibility of PM-Mito in patients with atypical PM or sIBM.

Correction to: Diagnostic accuracy of a smartphone bedside test to assess the fixation suppression of the vestibulo­ocular reflex: when nothing else matters.

The article Diagnostic accuracy of a smartphone bedside test to assess the fixation suppression of the vestibulo­ocular reflex: when nothing else matters, written by Florin Gandor, Manfred Tesch, Hannelore Neuhauser, Doreen Gruber, Hans­Jochen Heinze, Georg Ebersbach and Thomas Lempert, was originally published electronically on the publisher's internet portal on 01 June 2020 without open access.

Diagnostic accuracy of a smartphone bedside test to assess the fixation suppression of the vestibulo-ocular reflex: when nothing else matters.

OBJECTIVE: Validation of a bedside test to objectify the fixation suppression of the vestibulo-ocular reflex (FS-VOR) in patients with a cerebellar syndrome and healthy controls. METHODS: The vestibulo-ocular reflex and its fixation suppression were assessed by video-nystagmography (VNG) in 20 healthy subjects (mean age 56 ± 15) and 19 patients with a cerebellar syndrome (mean age 70 ± 11). The statistical cutoff delineating normal from pathological FS-VOR was determined at the 2.5th percentile of the normal distribution of the healthy cohort. VNG was then compared to a bedside test, where eye movements were recorded with a smartphone while patients were rotated on a swivel chair at a defined speed and amplitude. These videos were rated as normal or pathological FS-VOR by six blinded raters, and results compared to VNG. RESULTS: VNG in healthy controls showed FS-VOR with a reduction of nystagmus beats by 95.0% ± 7.2 (mean ± SD). The statistical cutoff was set at 80.6%. Cerebellar patients reduced nystagmus beats by only 26.3% ± 25.1. Inter-rater agreement of the smartphone video ratings was 85%. The sensitivity of the video ratings to detect an impaired FS-VOR was 99%, its specificity 92%. Inter-test agreement was 91%. CONCLUSION: The smartphone bedside test is an easily performed, reliable, sensitive, specific, and inexpensive alternative for assessing FS-VOR.