Awake perimetry testing for occipital epilepsy surgery

Abstract

In the literature, there are few reports that provide a detailed account on the technique of visual electrocortical stimulation in the setting of resective surgery for occipital epilepsy. In this technical note, the authors describe how a 26-year-old male with long-standing occipital epilepsy underwent resective surgery under awake conditions, using electrocortical stimulation of the occipital lobe, with the aid of a laser pointer and a perimetry chart on a stand within his visual field. The eloquent primary visual cortex was found to overlap with the seizure onset zone that was previously determined with subdural electrodes. A maximum functionally safe resection was performed, rendering the patient seizure free as of his last follow-up at 20 months, with no visual field impairment.

Evolution of patients with surgically treated drug-resistant occipital lobe epilepsy

“…To date, there is no randomized clinical trial on the surgical treatment of occipital epilepsy and the available case series show a significant results variability, due to their small sample size and the heterogeneity of their patients. [ 8 , 11 ]…”

“…[ 8 ] The patient’s visual status and the degree of postoperative visual deficit that is considered acceptable should therefore be discussed between patient and surgeon before the intervention. [ 11 ]…”

Visual Mapping for Tumor Resection: A Proof of Concept of a New Intraoperative Task and A Systematic Review of the Literature

“…One article used bipolar and monopolar mapping suction Probe, bipolar parameters were near as the abovementioned, and monopolar intensity was started at 4mA with a further 4mA increase up to 20mA maximum. The remaining article used monopolar stimulation with 3,5mA intensity and just cortical mapped is reported, without subcortical DES (41). Despite the homogeneity in the technique and stimulation parameters, five different intraoperative tasks were described:…”

“…A. Subjective sensations (10,18,41): Mentioned in three articles, this technique is based purely on the patient's phenomena on its visual field, such as flashes, shadows, darkened, or image distortion. In one case, a laser was given to the patient to mark the area of the visual field sensations on a perimetry chart (41).…”