Cortical sulcal areas in baboons (Papio hamadryas spp.) with generalized interictal epileptic discharges on scalp EEG.

Brain MRI studies in people with idiopathic generalized epilepsies demonstrate regional morphometric differences, though variable in magnitude and location. As the baboon provides an excellent electroclinical and neuroimaging model for photosensitive generalized epilepsy in humans, this study evaluated MRI volumetric and morphometric differences between baboons with interictal epileptic discharges (IEDs) on scalp EEG and baboons with normal EEG studies. Seventy-seven baboons underwent high-resolution brain MRI and scalp EEG studies. The scans were acquired using an 8-channel primate head coil (Siemens TRIO 3T scanner, Erlangen, Germany). After spatial normalization, sulcal measurements were obtained by object-based-morphology methods. One-hour scalp EEG studies were performed in animals sedated with ketamine. Thirty-eight (22F/16M) baboons had normal EEGs (IED-), while 39 (22F/17M) had generalized IEDs (IED+). The two groups were compared for age, total brain volume, and sulcal areas (Hotelling's Trace) as well as between-subjects comparison of 11 individual sulcal areas (averaged between left and right hemispheres). There were no differences between IED- and IED+ groups with respect to age or total brain (gray or white matter) volume, and multivariate tests demonstrated a marginally significant decrease of sulcal areas in IED+ baboons (p=0.075). Tests of between-subjects effects showed statistically significant decreases in the intraparietal (p=0.002), central (p=0.03) and cingulate sulci (p=0.02), and marginal decreases involving the lunate (p=0.07) and superior temporal sulci (p=0.08). Differences in sulcal areas in IED+ baboons may reflect global developmental abnormalities, while decreases of areas of specific sulci reflect anatomical markers for potential generators or cortical nodes of the networks underlying spontaneous seizures and photosensitivity in the baboon.

Effects of left frontal transcranial magnetic stimulation on depressed mood, cognition, and corticomotor threshold.

BACKGROUND: The pathophysiology of depression may include synaptic hypoactivity of left prefrontal cortex. Several groups of investigators have described improved mood associated with rapid transcranial magnetic stimulation (rTMS) but have not looked for possible cognitive side effects associated with left prefrontal magnetic stimulation. METHODS: We measured the effects of left prefrontal rTMS on mood, cognition, and motor evoked potential threshold in 10 patients with medication-resistant major depression. RESULTS: In a 2-week open trial of left prefrontal rTMS off antidepressant medications, scores on the Hamilton Rating Scale for Depression and the Beck Depression Inventory decreased by 41% and 40%, respectively. After resuming pre-rTMS antidepressant medication, improvement in mood was still significant at 1 and 3 months later. rTMS had no adverse effects on neuropsychological performance. rTMS treatments were associated with significant decreases in motor evoked potential threshold in the 9 of 10 patients who remained off psychotropic medications during the 2-week treatment period. CONCLUSIONS: These preliminary data suggest that left prefrontal rTMS is safe and improves mood in patients with medication-resistant major depression. Changes in motor evoked potential threshold suggest that prefrontal rTMS may alter brain activity at sites remote from the stimulation. Double-blind, sham-controlled studies are needed.