Blink reflex discloses CNS dysfunction in neurologically asymptomatic patients with systemic sclerosis

Objective: To investigate trigeminal-nerve, brain-stem, and brain function, in order to disclose a possible nervous system involvement in neurologically asymptomatic systemic sclerosis (SSc) patients. Methods: Using a standard electromyographic (EMG) technique, we recorded the early (R1) and late (R2) components of the blink reflex in 35 SSc patients with no history or signs of cranial-nerve impairment and 20 control subjects. SSc patients were classified as limited or diffuse SSc and also evaluated for disease duration, autoantibody pattern (ANA, ACA, Scl70) and skin score (by Rodnan modified method). Results: Whereas no SSc patients had an abnormal R1, six (18%) had delayed R2 responses. We found no correlation between R2 latency and clinical or laboratory data. Conclusions: Whereas previous studies reported both R1 and R2 abnormalities (reasonably due to trigeminal neuropathy) in symptomatic SSc patients, we found selective abnormalities of the R2 components in asymptomatic patients. The selective R2 abnormality is secondary to a central dysfunction, either because of a direct impairment of the polysynaptic circuits in the medulla, or because of a decreased cortico-reticular drive on these circuits. The lack of overt trigeminal symptoms in our patients favours a suprasegmental dysfunction, possibly due to microvascular lesions disseminated in the subcortical white matter.