CONGENITAL PERIODIC ALTERNATING NYSTAGMUS - DIAGNOSIS AND MANAGEMENT

Purpose: The purpose of the study is to investigate diagnostic criteri a and treatment methods for patients with congenital periodic alternat ing nystagmus (PAN), Methods: A retrospective analysis was performed o f clinical findings and serial eye movement recordings of patients wit h congenital PAN. Eighteen patients observed from 1983 through 1996 an d diagnosed with congenital PAN are included. Five of these have ocula r or oculocutaneous albinism, Nine of the 18 patients were treated, Th ree had Kestenbaum operations before referral to the authors, one was treated with baclofen, and five had large recessions of the four horiz ontal recti, The studied parameters included visual acuity (VA) and ab normal head posture (AHP); temporal aspects of PAN cycle, nystagmus wa veforms, frequency, amplitude, and velocity; as well as mean foveation fraction, a mean percentage of the nystagmus cycle spent at retinal s lip velocities less than 10 degrees per second, Results: The authors d iagnosed PAN in 9% of patients with congenital nystagmus, although mos t had not been diagnosed with PAN before referral, despite changing ny stagmus. Sixteen patients had AHP, typically shifting, The PAN cycle w as of variable duration, often with asymmetric right- and left-beating components. Although horizontal jerk nystagmus with accelerating slow phase was predominant, other waveforms were encountered in the active phase of PAN, in the quiet phase (close to null zone), similar, but l ess intense, oscillations than those in the active phase were characte ristic. Half of the patients showed a combination of waveforms in both phases. Baclofen treatment was unsuccessful. Patients who had Kestenb aum procedures remained with AHP in the original or opposite direction , without change in nystagmus or VA. Large recessions of four horizont al recti proved uncomplicated, This treatment improved, at least for s everal years, AHP and VA and caused favorable changes in nystagmus par ameters in ail patients, Mean foveation fractions increased significan tly after surgery. Conclusions: Congenital PAN often is underdiagnosed . Differing waveforms may indicate PAN. Evaluation of nystagmus, espec ially before surgery, for at least 3 minutes, preferably with eye move ment recordings, is necessary to diagnose PAN and perhaps prevent Kest enbaum procedures, which seem inappropriate Large horizontal recti rec essions seem to provide safe and promising treatment.