Poster Session: Retinal Changes Associated with Football-Related Concussions and Head Impacts.

This pilot study explored the sensitivity of retinal markers to CNS sequelae of concussive and subconcussive head hits. Three groups of college athletes were assessed at pre-season, post-season and 4-months later: Football players with a concussion history (FB+C) (n = 9), players without a concussion history (FB-C) (n = 11), and non-contact athletes (swimmers, track & field; Non-FB) (n = 12). Measures included optical coherence tomography (OCT), OCT angiography, electroretinography, and visual acuity testing. Head impacts during the season were tracked with in-helmet accelerometers. At pre-season, FB+C demonstrated thicker macular central subfields (CSF) (Hedge's g (effect size) = 1.05, p = 0.02) and retinal nerve fiber layers (RNFL) (g = 0.81, p = 0.08), relative to other athletes. Differences in CSF thickness were also observed at post-season and follow-up (gs > 1.00, ps < 0.04), reflecting their non-short-term nature. RNFL was thicker in FB+C at post-season (g = 0.93, p = 0.06) but not later. Total head impacts during the season correlated with increases in CSF thickness from baseline to follow-up only (r = -0.53, p = 0.02). High intensity head impacts in particular correlated with increases in cup-to-disc ratio at post-season and follow-up (rs > 0.53, ps < 0.03). These data suggest that concussion history is associated with retinal changes that are not short-term, and that severe head impacts are associated with acute changes whose duration is not yet known.

The role of P2Y12 in the kinetics of microglial self-renewal and maturation in the adult visual cortex in vivo.

Microglia are the brain's resident immune cells with a tremendous capacity to autonomously self-renew. Because microglial self-renewal has largely been studied using static tools, its mechanisms and kinetics are not well understood. Using chronic in vivo two-photon imaging in awake mice, we confirm that cortical microglia show limited turnover and migration under basal conditions. Following depletion, however, microglial repopulation is remarkably rapid and is sustained by the dynamic division of remaining microglia, in a manner that is largely independent of signaling through the P2Y12 receptor. Mathematical modeling of microglial division demonstrates that the observed division rates can account for the rapid repopulation observed in vivo. Additionally, newly born microglia resemble mature microglia within days of repopulation, although morphological maturation is different in newly born microglia in P2Y12 knock out mice. Our work suggests that microglia rapidly locally and that newly born microglia do not recapitulate the slow maturation seen in development but instead take on mature roles in the CNS.

Dynamics of microglia and dendritic spines in early adolescent cortex after developmental alcohol exposure.

Fetal alcohol spectrum disorder patients suffer from many cognitive disabilities. These include impaired auditory, visual, and tactile sensory information processing, making it more difficult for these patients to learn to navigate social scenarios. Rodent studies have shown that alcohol exposure during the brain growth spurt (BGS) can lead to acute neuronal apoptosis and an immunological response by microglia in the somatosensory cortex. Since microglia have critical physiological functions, including the support of excitatory synapse remodeling via interactions with dendritic spines, we sought to understand whether BGS alcohol exposure has long-term effects on microglial or dendritic spine dynamics. Using in vivo two-photon microscopy in 4-5 week old mice, we evaluated microglial functions such as process motility, the response to tissue injury, and the dynamics of physical interactions between microglial processes and dendritic spines. We also investigated potential differences in the morphology, density, or dynamics of dendritic spines in layer I/II primary sensory cortex of control and BGS alcohol exposed mice. We found that microglial process motility and contact with dendritic spines were not altered after BGS alcohol exposure. While the response of microglial processes toward tissue injury was not significantly altered by prior alcohol exposure, there was a trend suggesting that alcohol early in life may prime microglia to respond more quickly to secondary injury. Spine density, morphology, stability, and remodeling over time were not perturbed after BGS alcohol exposure. We demonstrate that after BGS alcohol exposure, the physiological functions of microglia and excitatory neurons remain intact in early adolescence.

Diagnosis and management of benign paroxysmal positional vertigo (BPPV).

There is compelling evidence that free-floating endolymph particles in the posterior semicircular canal underlie most cases of benign paroxysmal positional vertigo (BPPV). Recent pathological findings suggest that these particles are otoconia, probably displaced from the otolithic membrane in the utricle. They typically settle in the dependent posterior canal and render it sensitive to gravity. Well over 90% of patients can be successfully treated with a simple outpatient manoeuvre that moves the particles back into the utricle. We describe the various techniques for this manoeuvre, plus treatments for uncommon variants of BPPV such as that of the lateral canal. For the rare patient whose BPPV is not responsive to these manoeuvres and has severe symptoms, posterior canal occlusion surgery is a safe and highly effective procedure.

Intratympanic gentamicin for intractable Meniere's disease: 5-year follow-up.

OBJECTIVE: To determine the efficacy and morbidity of intratympanic gentamicin titration therapy on patients with incapacitating unilateral Meniere's disease. METHOD: The study consisted of a retrospective chart review and patient interviews. Sixty-eight patients had been followed for a minimum of 24 months and were reported on in an earlier study. Forty-six of these individuals were available for detailed follow-up at 5 years post-gentamicin therapy. MAIN OUTCOME MEASURES: Vertigo frequency, hearing status, personal disability ratings, and tinnitus level before and after gentamicin therapy were measured. RESULTS: Seventy-four percent of patients showed complete vertigo control and an additional 7% showed substantial vertigo control. There was also significant improvement in personal ratings of social and economic functioning. Overall, the group showed no combined statistically significant changes in any of the hearing parameters. CONCLUSION: Intratympanic gentamicin titration therapy provides excellent vertigo control, with a similarly significant improvement in both personal and occupational functioning.