The impact of etiology in lesion-symptom mapping - A direct comparison between tumor and stroke.

INTRODUCTION: Lesion-symptom mapping is a key tool in understanding the relationship between brain structures and behavior. However, the behavioral consequences of lesions from different etiologies may vary because of how they affect brain tissue and how they are distributed. The inclusion of different etiologies would increase the statistical power but has been critically debated. Meanwhile, findings from lesion studies are a valuable resource for clinicians and used across different etiologies. Therefore, the main objective of the present study was to directly compare lesion-symptom maps for memory and language functions from two populations, a tumor versus a stroke population. METHODS: Data from two different studies were combined. Both the brain tumor (N = 196) and stroke (N = 147) patient populations underwent neuropsychological testing and an MRI, pre-operatively for the tumor population and within three months after stroke. For this study, we selected two internationally widely used standardized cognitive tasks, the Rey Auditory Verbal Learning Test and the Verbal Fluency Test. We used a state-of-the-art machine learning-based, multivariate voxel-wise approach to produce lesion-symptom maps for these cognitive tasks for both populations separately and combined. RESULTS: Our lesion-symptom mapping results for the separate patient populations largely followed the expected neuroanatomical pattern based on previous literature. Substantial differences in lesion distribution hindered direct comparison. Still, in brain areas with adequate coverage in both groups, considerable LSM differences between the two populations were present for both memory and fluency tasks. Post-hoc analyses of these locations confirmed that the cognitive consequences of focal brain damage varied between etiologies. CONCLUSION: The differences in the lesion-symptom maps between the stroke and tumor population could partly be explained by differences in lesion volume and topography. Despite these methodological limitations, both the lesion-symptom mapping results and the post-hoc analyses confirmed that etiology matters when investigating the cognitive consequences of lesions with lesion-symptom mapping. Therefore, caution is advised with generalizing lesion-symptom results across etiologies.

A randomized controlled study comparing the endocrine effects of pulsatile intravenous gonadotropin-releasing hormone after gonadotropin-releasing hormone agonist pretreatment versus clomiphene citrate in patients with polycystic ovary syndrome.

OBJECTIVE: To compare the endocrine changes in the follicular phase in infertile patients with polycystic ovary syndrome (PCOS) treated with either pulsatile IV GnRH after GnRH-agonist (GnRH-a) down-regulation or clomiphene citrate (CC). DESIGN: Subgroup analysis within a randomized, controlled, multicenter study. SETTING: Women referred to the Infertility Clinic, Catharina Hospital Eindhoven, The Netherlands. PATIENT(S): Twenty-eight infertile patients with PCOS. INTERVENTIONs): Patients were randomly assigned to pulsatile IV GnRH (10-20 microgram/90 min) after GnRH-a down-regulation or CC (50-150 mg; cycle days 3-7). Patients were monitored on alternate days with ovarian sonography and serum concentrations of E(2), LH, and FSH. Serum P and sonography confirmed ovulation. MAIN OUTCOME MEASURE(S): Serum concentrations of E(2), LH, and FSH were assessed before treatment was started and after each ovarian sonography. RESULT(S): In ovulatory cycles, no statistically significant differences were observed during the follicular phase comparing serum concentrations of E(2), LH, and FSH between the treatments. However, a significant increase in LH occurred in the GnRH group. CONCLUSION(S): No significant endocrine differences were observed between GnRH and CC treatment. However, there was a significant increase in the serum LH concentration during the follicular phase in the GnRH group. Increments of LH in the GnRH group may be due to recovery of endogenous LH secretion.