Visual Function 20 Years After Childhood Hemispherectomy for Intractable Epilepsy

Abstract

To investigate visual function in adults post hemispherectomy in childhood. Noncomparative case series. All participants underwent visual acuity, binocular function, visual field, optical coherence tomography (OCT) of the retinal nerve fiber layer (RNFL), and monocular pattern reversal visually evoked potentials (prVEP). Six adults who had a hemispherectomy in childhood (median 21.5 years postoperative). Comparison was made of visual acuity, visual field height, global RNFL thickness, and prVEP amplitude evoked by full- and half-field stimulation. Comparison of the eye ipsilateral to the side of surgery to the contralateral eye was achieved employing paired t tests to the visual function measures. All participants had homonymous hemianopia. The residual seeing visual field was constricted in all cases when compared with normative data despite crossing the midline into the blind hemifield in 11 of 12 eyes. This observation was supported by prVEP to stimuli presented in the blind half field. The height of the visual field was smaller in the eye contralateral to the side of surgery compared with the ipsilateral side (P= .047). Visual acuity and RNFL thickness also showed greater diminution in the contralateral eye (P= .040 and P=.0004). Divergent strabismus was found in 4 participants with greater field loss. Adults post hemispherectomy in childhood may have better visual function in the eye ipsilateral to the side of the hemispherectomy compared with the contralateral eye. Possible mechanisms of the interocular difference are discussed. Though visual fields and prVEP responses demonstrate evidence of reorganization into the blind half field, they also reveal significant unexpected constriction of the functional field.