SEP 17, 2014
By Michael Vaphiades, DO
Neuro-Ophthalmology/Orbit
This case demonstrates that surgical decompression of cystic lesions adjacent to posterior visual pathways can result in recovery of chronic visual field loss.
A 62-year-old woman presented with a chronic left homonymous visual field defect because of a right occipital cyst. Serial visual field examination documented stable visual fields for 12 months, after which there was worsening of visual fields associated with enlargement of the cyst.
She underwent endoscopic fenestration of her intracranial cyst, resulting in reduction in size. The authors note that the surgical approach was planned using neuronavigation, and the cyst was entered on its postero-lateral aspect, thereby avoiding the optic radiations and visual cortex.
At three months postop, the patient reported marked improvement in visual fields, and automated perimetry and has remained stable over two years of follow-up.
The authors write that the physiological basis of visual improvement in this patient is unclear, but possible mechanisms include postoperative restitution of synaptic transmission and increased synaptic efficiency in the posterior visual pathways. Studies of patients with spontaneous recovery of visual fields indicate a contribution of neuronal plasticity, which is greater in partially affected areas bordering the field defect.
On visual field testing, patients may demonstrate inconsistent and variable responses to stimuli in these areas. The moderate success of visual rehabilitation in these patients suggests that partially damaged neurons can adapt even a considerable time interval after initial injury.