Blinking: a Benign "Tic" - or Something More?

    Pediatric ophthalmologists evaluate a fair number of children with a history of spontaneously appearing, excessive eyelid blinking. We sometimes find a treatable, underlying problem; but in many cases, there are no eye abnormalities to causally explain the blinking. The tendency is to "explain" this as a "habit" behavior, speculating about some sort of transient psychological stress or inadvertent parental reinforcement. And most affected children do improve in time, though some will exhibit recurrences which often defy logical explanations.

    This was recently reviewed in a study of 99 children presenting to the Pediatric Ophthalmology Clinic at the Cullen Eye Institute in Houston (Coats, Payse, Kim: Excessive Blinking in Childhood: A Prospective Evaluation of 99 Children. Ophthalmology 108:1556, 2001). 22 of these children had associated central nervous system diseases, including seizures, brain tumors, infection, cerebral palsy, migraine, and autism among others; but  these problems were felt to be causally associated with the blinking in only 6 cases. Treatable problems included uncorrected refractive errors, strabismus, conjunctivitis, dry eye, and eyelid abnormalities. This left 33 patients who were classified as having a "habit tic" or "psychogenic" explanation for the blinking.

    Recent research at the National Institutes of Health has uncovered a possible physical explanation for at least some otherwise unexplained cases of spontaneous blinking associated with other behavioral disorders. The initial observation was an association of motor tics with a recent streptococcal infection. A "worst case scenario" had been recognized for years: Sydenham's chorea, a generalized movement disorder associated with rheumatic fever. Researchers identified children with obsessive compulsive disorder (OCD) and Tourette's syndrome appearing in the aftermath of a strep infection who shared the D8/17 trait marker for rheumatic fever with patients exhibiting classic symptoms of Sydenham's chorea. They subsequently published an article describing 50 cases with a new syndrome dubbed PANDAS, pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections. The postulated mechanism is an anti-strep antibody which cross-reacts with tissue in a major nerve relay center in the brain, the basal ganglia, inducing inflammatory nerve cell stimulation - yet another "auto-immune" phenomenon.

    The question for pediatric ophthalmologists is just how selective this process can be - and if strep is the only trigger. I have several "blinking" patients who meet the 5 defined criteria for PANDAS: presence of OCD and/or a tic disorder, prepubertal symptom onset, episodic course of symptom severity, association with GABHS infections, and association with neurological abnormalities. This leaves a much larger group who suddenly start blinking inexplicably, have no other observable physical explanation, and who gradually stop the behavior over the ensuing weeks or months. Many seem to have a history of some sort of upper respiratory infection in the days preceding onset of the blinking. The time course is intriguingly similar to post-infectious production of IgG antibodies. Could this be a PANDAS variant with other infectious or environmental agents triggering a cross-reacting anti-basal ganglia antibody in a genetically predisposed individual?

    While this sort of explanation is more appealing to me than simply applying a descriptive label to an observed behavior, it's pure speculation at this point in time. The important message is that spontaneous blinking does warrant a careful clinical investigation including non-ophthalmological tests when other neurologic or behavioral symptoms are associated.

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