Abnormal Control of Orbicularis Oculi Reflex Excitability in Multiple Sclerosis

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.

Defective sensorimotor integration in preparation for reaction time tasks in patients with multiple sclerosis

“…The present study was part of an extensive neurophysiological study of a cohort of 20 patients with relapsing-remitting MS, prospectively selected from the outpatient MS clinic of the Hospital Clinic of Barcelona. Other features of the same patients have been reported elsewhere (Cabib et al 2014;Llufriu et al 2012) or are under preparation. Patients were diagnosed according to the criteria of Polman and Rudick (2010) and recruited if they were ambulatory, had low-to-moderate scores on the Expanded Disability Status Scale (EDSS; 0 -6.0) (Kutzke 1983), had no clinically relevant limb paresis, were under stable immunomodulatory treatment, and were relapse and steroid free for at least 1 mo before inclusion.…”

Effect of Aging, Gender and Sensory Stimulation of TRPV1 Receptors with Capsaicin on Spontaneous Swallowing Frequency in Patients with Oropharyngeal Dysphagia: A Proof-of-Concept Study

“…Excitatory supranuclear influences are proportional to brain excitability. This has been well documented in neurophysiological studies on the blink reflexes in patients with stroke or multiple sclerosis [ 7 , 8 ], and it is hypothesized that the nerve control of spontaneous swallowing could be similar. The SSF in healthy volunteers is 1.32 swallows/min [ 9 ], which decreases to approximately 0.6 swallows/min in older people without swallowing impairments [ 10 ].…”

“…The hypothesis that the neural control of spontaneous swallowing depends on the CPG and could be similar to that described for the blink reflex [ 2 , 3 , 7 , 8 ], leads to peripheral neurostimulation strategies as a possible treatment to improve SSF. One of the most used chemical strategies to improve swallow response is capsaicin stimulation.…”

Clinical utility of contact heat evoked potentials (CHEPs) in a case of mentalis nerve lesion

“…Data were analyzed by taking into consideration reference values of our own department, published in pertinent literature ( Valls-Solé, 2005 , Valls-Solé and Deuschl, 2006 , Cabib et al, 2014 , Granovsky et al, 2016 ). Side-to-side maximum differences in healthy subjects were available for comparison for the blink reflex R2 latency (5.0 ms, respectively, according to Valls-Solé and Deuschl, 2006 ), and for the CHEPs N2 latency (88.7 ms) and N2/P2 amplitude (15.0 μV), according to Granovsky et al (2016) .…”