Visuoperceptive impairment in adult patients with occipital lobe epilepsies

The cognitive profile of occipital lobe epilepsy and the selective association of left temporal lobe hypometabolism with verbal memory impairment

We investigated the cognitive profile of structural occipital lobe epilepsy (OLE) and whether verbal memory impairment is selectively associated with left temporal lobe hypometabolism on [18F]-fluorodeoxyglucose positron emission tomography (FDG-PET). Nine patients with OLE, ages 8-29 years, completed presurgical neuropsychological assessment. Composite measures were calculated for intelligence quotient (IQ), speed, attention, verbal memory, nonverbal memory, and executive functioning. In addition, the Wisconsin Card Sorting Test (WCST) was used as a specific measure of frontal lobe functioning. Presurgical FDG-PET was analyzed with statistical parametric mapping in 8 patients relative to 16 healthy volunteers. Mild impairments were evident for IQ, speed, attention, and executive functioning. Four patients demonstrated moderate or severe verbal memory impairment. Temporal lobe hypometabolism was found in seven of eight patients. Poorer verbal memory was associated with left temporal lobe hypometabolism (p = 0.002), which was stronger (p = 0.03 and p = 0.005, respectively) than the association of left temporal lobe hypometabolism with executive functioning or with performance on the WCST. OLE is associated with widespread cognitive comorbidity, suggesting cortical dysfunction beyond the occipital lobe. Verbal memory impairment is selectively associated with left temporal lobe hypometabolism in OLE, supporting a link between neuropsychological dysfunction and remote hypometabolism in focal epilepsy.

Visuoperceptual and visuospatial abilities prior to and after anterior temporal lobectomy: a case study

We describe a patient who presented with temporal lobe epilepsy and a seizure onset pattern in the right temporo-occipital area. Structural MRI revealed sclerosis in the right hippocampus. A comprehensive presurgical neuropsychological assessment allowed us to disentangle deficits in visual object recognition and visual imagery from well-preserved spatial capacities. Following a right temporal lobectomy, the patient remained seizure free, and 1 year postsurgery, the patient's scores on object recognition and imagery were in the normal range. Our findings suggest that visual object recognition and visual imagery are sustained by cortical areas located in proximity to the temporo-occipital ventral pathway and that perceptual and imagery spatial processing is subserved as well by anatomically close mechanisms. Furthermore, the results seem to indicate that nonlesional paroxysmal activity in the posterior temporal lobe can cause chronic dysfunctions of the visual system and that it may be reversible with effective seizure control.