Frequency Responses to Visual Tracking Stimuli May Be Affected by Concussion.

Human visual tracking performance is known to be reduced with an increase of the target's speed and oscillation frequency, but changes in brain states following a concussion may alter these frequency responses. The goal of this study was to characterize and compare frequency-dependent smooth pursuit velocity degradation in normal subjects and patients who had chronic postconcussion symptoms, and also examine cases of acutely concussed patients. Eye movements were recorded while subjects tracked a target that moved along a circular trajectory of 10° radius at 0.33, 0.40, or 0.67 Hz. Performance was characterized by the gain of smooth pursuit velocity, with reduced gain indicating reduced performance. The difference between normal and chronic patient groups in the pattern of decrease in the gain of horizontal smooth pursuit velocity as a function of the stimulus frequency reflected patients performing more poorly than normal subjects at 0.4 Hz while both groups performing similarly at 0.33 or 0.67 Hz. The performance of acute patients may represent yet another type of frequency response. The findings suggest that there may be ranges of stimulus frequencies that differentiate the effects of concussion from normal individuals.

Pathology of spinal ependymomas: an institutional experience over 25 years in 134 patients.

BACKGROUND: Ependymomas constitute approximately 40% of primary intraspinal tumors. Current World Health Organization (WHO) grading may not correlate with observed progression-free survival (PFS). OBJECTIVE: This retrospective study of prospectively collected data examines whether PFS is influenced by the histological grade or by the extent of resection. It also analyzes the usage and effectiveness of postoperative adjuvant radiotherapy. METHODS: We reviewed 134 consecutive patients with ependymomas of all grades. Pathology slides were re-reviewed and the histological grades were confirmed by a single neuropathologist. Postoperative residual or recurrence was evaluated with follow-up magnetic resonance imaging. RESULTS: There were 85 male and 49 female patients, ranging from 10 to 79 (median 41) years of age. Thirty patients had WHO grade I tumors, 101 had grade II tumors, and 3 had grade III tumors. Kaplan-Meier analysis of PFS demonstrated a mean duration of 6 years for grade I, 14.9 years for grade II, and 3.7 years for grade III (P < .001). In grade II ependymomas, mean PFS was 11.2 years with subtotal resection and 17.8 years with gross total resection (P < .01). PFS of patients who underwent subtotal resection was not significantly changed by adjuvant radiotherapy (P < .36). CONCLUSION: Patients with grade II ependymoma have significantly longer PFS than patients with grade I ependymoma. The extent of resection did not affect PFS in grade I ependymoma but it did in grade II. Contrary to its higher grade, WHO grade II ependymoma carries a better prognosis than WHO grade I ependymoma.