Faculty Bibliography

Objective: The Mobile Universal Lexicon Evaluation System (MULES) is a new test of rapid picture naming that is under investigation in youth, collegiate and professional athlete cohorts as a concussion screening tool. The purpose of this study is to determine the ocular motor underpinnings, including saccade characteristics, required to perform this vision-based performance measure. Background: The MULES includes 54 color photographs of fruits, objects and animals. It has demonstrated excellent feasibility for administration among adult volunteers and in cohorts of athletes of all ages at pre-season baseline. MULES likely captures a more extensive vision network in the brain compared to rapid number naming, integrating saccades, color perception and object identification. Video-oculographic studies of the King-Devick (K-D) test of rapid number naming demonstrate prolonged inter-saccadic intervals (ISI) among individuals with longer testing times. Design/Methods: Participants underwent testing with the paper-based MULES as well as the computer screen-based version (eMULES) designed for simultaneous testing with infrared-based video-oculography (Eye Link 1000+). Saccade velocity, duration and the inter-saccadic interval were measured. Results: Among adult volunteers (n=23, aged 19-45) and patients with recent concussion (n=6, aged 17-43), those with the greatest number of saccades had the longest eMULES completion times ( f0 . 48 , p=0.008). In this cohort, prolonged ISI was not associated with greater eMULES testing times (AS=0.06, p=0.76). Conclusions: Longer testing times for the MULES likely reflect greater numbers of saccades rather than prolongation of the ISI. This pattern may reflect greater degrees of cognitive activity and visual pathway complexity for picture compared to number naming. Underlying dynamics for eye movements are likely to differ between the MULES and K-D, supporting complementary roles for each in concussion assessment

Objective: Speeded Saccadic Eye Movement Predicts Symbol Digit Modalities Test Performance in Multiple Sclerosis Background: Multiple sclerosis is an autoimmune demyelinating disease with estimates of cognitive impairment above 30% in pediatric and 50% in adult patients. The SDMT, a widely-used screening tool that measures speeded information processing, has been used to track cognitive decline in MS. The K-D test is a brief measure of saccadic eye movement speed using a timed number naming test, commonly used for the detection of mild traumatic brain injury. Here, we tested the sensitivity of the K-D test in MS and its association with performance on the SDMT. Design/Methods: Adult and pediatric patients with clinically-definite MS were consecutively recruited through the NYU Langone MS Comprehensive Care Center. All participants completed the SDMT and K-D at a single visit. Results: A total of 30 participants completed the assessments ranging in age from 13 to 72 years (mean 38 +/- 19 years), were 74% female, and with an EDSS range 0.0 to 6.5. Relative to age normative data, the K-D indicated greater impairment than the SDMT (74% vs. 48%, respectively). Controlling for age, both tests were significantly correlated (r=0.44, p =0.02), demonstrating a close contribution of oculomotor function to SDMT performance. Conclusions: The K-D test is sensitive to detecting impairment in MS across the lifespan. Performance on the SDMT is closely associated with oculomotor function in MS

Objective: To compare video-oculography performed by EyeTribe versus EyeLink during a rapid number naming task. Background: With increasing accessibility of portable, economical, video-based, infrared eye trackers, such as EyeTribe, there is growing interest in eye movement recordings, including in the setting of sports-related concussion. However, prior to implementation, there is a primary need to establish the validity of these low-resolution (30-60 Hz) eye trackers via comparison with high-resolution (500-1000 Hz) devices such as EyeLink. Design/Methods: A convenience sample of 30 controls performed a digitized version of the King-Devick (K-D) test with EyeTribe and EyeLink eye movement recordings. Results: Signal loss and tracings inconsistent with eye movement physiology were common with EyeTribe. Saccade main sequence parameters (fit to decaying exponentials) were significantly different for the two devices (reported as best-fit parameter and 95% confidence interval). Peak velocity versus amplitude relationships revealed a main sequence asymptote of 1674degree/s (CI: 1527, 1852degree/s) for EyeTribe vs. 506degree/s (CI: 499, 513degree/s) for EyeLink and a time constant of 102.9degree (CI: 93.5,115.7degree) for EyeTribe vs. 6.1degree (CI: 5.3, 6.3degree) for EyeLink. Duration versus amplitude relationships also demonstrated significant differences, with an asymptote of 62.7ms (CI: 61.0, 64.3ms) for EyeTribe vs. 83.2ms (CI: 82.2, 84.4ms) for EyeLink and time constant of 4.9degree (CI: 4.6, 5.3degree) for EyeTribe vs. 13.8degree (CI: 13.6, 14.1degree) for EyeLink. Total number of saccades to complete the K-D was significantly lower with EyeTribe, with an average of 110.2 vs. 120.5 saccades recorded by EyeTribe and EyeLink respectively (paired t-test, p=0.001). There was no significant difference in the inter-saccadic interval, despite a discrepancy of 42ms between devices. Conclusions: The EyeTribe device was unable to capture valid saccade data during rapid number naming. Caution is advised regarding the implementation of eye trackers with low temporal resolution for objective saccade assessment or sideline concussion screening

Objective: To describe a case of gaze-position dependent opsoclonus and discuss potential localization. Background: Opsoclonus is characterized by bursts of involuntary, back-to-back saccades without an intersaccadic interval at frequency of 10-25 Hz in horizontal, vertical, and torsional planes. Opsoclonus with gaze-directional selectivity has been rarely described. Design/Methods: We report a 50 year-old man who sustained a concussion three years prior followed by postconcussive headaches and disequilibrium. Exam revealed very small amplitude oscillations in left gaze that could not be further characterized on clinical exam. Different larger amplitude horizontal oscillations were present with convergence. There were no other posterior fossa signs. Brain MRI was unremarkable. Results: Video-oculography demonstrated opsoclonus predominantly in left gaze [median amplitude 5 deg (range <1- 11 deg), frequency 30 Hz] and during leftward smooth pursuit, which improved [median amplitude 2 deg (range < 1-10 deg), frequency 10 Hz] as post-concussive symptoms improved. Conclusions: This case demonstrates opsoclonus with eye position selectivity in post-concussive syndrome. Various theories of opsoclonus exist, including lesions of saccade burst, omnipause, or cerebellar fastigial pause neurons which project to brainstem burst neurons. Ultimately, all of these lead to increased excitability in the inherently unstable saccade generators. Burst and omnipause neuron firing rates are not influenced by eye position. The leftward gaze-dependence in our case supports dysfunction of cerebellar dorsal vermis Purkinje cells leading to disinhibition of the fastigial ocular motor nucleus, as vermal pause neurons have gaze-directional selectivity. Vermal pause neurons exhibit a pause of discharge immediately before and during contralateral saccades. Thus, selective dysfunction, possibly related to concussion-related membrane instability, could create an imbalance in burst neuron excitability, resulting in triggering of unidirectional opsoclonus. Further, our patient's saccade system may be inherently prone to oscillations given the presence of larger amplitude horizontal oscillations consistent with 'voluntary flutter', which persisted when leftward opsoclonus improved

Objective: This study introduces the Mobile Universal Lexicon Evaluation System (MULES), a new vision-based test of rapid picture naming, in a cohort of youth and collegiate athletes at pre-season concussion testing. Background: Vision-based measures of rapid number naming (King-Devick [K-D]) have improved the sensitivity of sports-related concussion screening. K-D requires saccades and vergence, measuring aspects of frontal, parietal and brainstem centers. We developed the MULES to capture a more extensive vision network, integrating saccades, color perception, and object identification. Design/Methods: We administered MULES and K-D to youth and collegiate athletes during pre-season baseline testing. Sports for 2016-17 included ice hockey, football, soccer, volleyball and wrestling. Test administration order was randomized. Results: Among 165 athletes (age 14+/-5 years, range 6-24, 25% female), average K-D times (59.9+/-29.7 seconds) were similar to MULES (57.9+/-20.4 seconds). Higher K-D times predicted greater MULES times, accounting for age (p<0.001, linear regression). Age was itself a predictor of K-D and MULES time scores, with longer times noted for younger participants (p<0.001). Faster times with increasing age were noted primarily among athletes <16 years for K-D and <15 years for MULES. MULES showed greater degrees of improvement between two baseline trials (57.9 vs. 51.2 seconds, p<0.0001, paired t-test), vs. K-D (59.9 vs. 58.3 seconds, p=0.01). Conclusions: A complex task, the MULES test of rapid picture naming involves a more extensive visual network that captures not only rapid saccades but color perception and the characterization of objects. Color recognition is early in object processing and requires area V4 and the inferior temporal projections. In contrast, rapid number naming appears to engage a specific area of the inferior temporal cortex. Both tests use the centers responsible for initiating and sequencing saccadic eye movements, and will be further examined in our youth and collegiate cohorts during this athletic season for their ability to detect concussion