Abnormal control of orbicularis oculi reflex excitability in multiple sclerosis

Christopher Cabib; Sara Llufriu; Eloy Martinez-Heras; Albert Saiz; Josep Valls-Solé

doi:10.1371/journal.pone.0103897

Abnormal control of orbicularis oculi reflex excitability in multiple sclerosis

PLoS One. 2014 Aug 1;9(8):e103897. doi: 10.1371/journal.pone.0103897. eCollection 2014.

Authors

Christopher Cabib¹, Sara Llufriu², Eloy Martinez-Heras², Albert Saiz², Josep Valls-Solé¹

Affiliations

¹ EMG Unit, Neurology Department, Hospital Clinic, Barcelona, Spain, IDIBAPS (Institut d'Investigació Augustí Pi i Sunyer), Facultat de Medicina, University of Barcelona, Barcelona, Spain.
² Center for Neuroimmunology, Neurology Department, Hospital Clínic, Barcelona, Spain, IDIBAPS (Institut d'Investigació August Pi i Sunyer), Universitat de Barcelona, Barcelona, Spain.

Abstract

Brain lesions in patients with multiple sclerosis may lead to abnormal excitability of brainstem reflex circuits because of impairment of descending control pathways. We hypothesized that such abnormality should show in the analysis of blink reflex responses in the form of asymmetries in response size. The study was done in 20 patients with relapsing-remitting multiple sclerosis and 12 matched healthy subjects. We identified first patients with latency abnormalities (AbLat). Then, we analyzed response size by calculating the R2c/R2 ratio to stimulation of either side and the mean area of the R2 responses obtained in the same side. Patients with significantly larger response size with respect to healthy subjects in at least one side were considered to have abnormal response excitability (AbEx). We also examined the blink reflex excitability recovery (BRER) and prepulse inhibition (BRIP) of either side in search for additional indices of asymmetry in response excitability. Neurophysiological data were correlated with MRI-determined brain lesion-load and volume. Eight patients were identified as AbLat (median Expanded Disability Status Scale-EDSS = 2.75) and 7 of them had ponto-medullary lesions. Nine patients were identified as AbEx (EDSS = 1.5) and only 2 of them, who also were AbLat, had ponto-medullary lesions. In AbEx patients, the abnormalities in response size were confined to one side, with a similar tendency in most variables (significantly asymmetric R1 amplitude, BRER index and BRIP percentage). AbEx patients had asymmetric distribution of hemispheral lesions, in contrast with the symmetric pattern observed in AbLat. The brainstem lesion load was significantly lower in AbEx than in AbLat patients (p = 0.04). Asymmetric abnormalities in blink reflex response excitability in patients with multiple sclerosis are associated with lesser disability and lower tissue loss than abnormalities in response latency. Testing response excitability could provide a reliable neurophysiological index of dysfunction in early stages of multiple sclerosis.

Publication types

Controlled Clinical Trial
Research Support, Non-U.S. Gov't

MeSH terms

Adult
Blinking / physiology*
Female
Humans
Magnetic Resonance Imaging
Male
Middle Aged
Multiple Sclerosis / physiopathology*

Grants and funding

The authors acknowledge the financial support from Fundació TV3 Grant 110930 to J. V. -S. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.