Outcome of Surgery on Neurocognitive Functioning in Patients with Otic Capsule Defects

Abstract

There are two forms of otic capsule defect: Perilymph Fistula (PLF), a tear that typically occurs in the round window; and Superior Semicircular Canal Dehiscence (SCD), a thinning or absence of bone between the otic capsule and the brain. Symptoms of either may comprise mild to severe disturbances in the vestibular and auditory systems. These may be accompanied by various cognitive inefficiencies. Neurotologists, Grimm, Hemenway, LeBray, and Black (1989) measured cognitive efficiency pre- surgery in 38 adults who had acquired PLF. Assessment revealed difficulty in: verbal and visual memory; attention/concentration; and mental flexibility. Despite their research, the reality of PLF remains controversial (Hornibrook, 2012; Hughes, Sismanis & House, 1990) as at present, there is no objective means of providing a firm diagnosis. In contrast, objective diagnostic tests can corroborate an SCD, yet no research has been conducted concerning cognitive functioning. This study mirrors Grimm et al.’s attempt to substantiate cognitive difficulties in patients with otic capsule defects. Participants were recruited through the Ear and Skull Base Center, at Legacy Research Institute, in Portland, Oregon. The sample consisted of eighteen participants, including five adolescents. The treatment plan included these pre and post-surgical neuropsychological assessments: intelligence, attention/concentration, processing speed, working memory, and mental flexibility. Assessments were administered six to one week(s) prior to surgery; two to three months following surgery; and nine to twelve months later. Scores were analyzed using analysis of variance for repeated measures. Similar to the findings of Grimm et al, pretest scores suggested possible impairment in cognitive functioning. Overall post-operative results indicated significant improvement in both cognitive and emotional functioning for PLF patients. Cognitive and emotional gains showed large effect sizes for the PLF participants, but more modest gains for the SCD participants. Although otic capsule defects affect a small segment of the population, its continued examination may have broader applications. SCD patients have similar patterns of cognitive function, however they have earlier brain reorganization and less dramatic changes post-operatively. Conversely, as PLF typically develops later, results demonstrated dramatic post-operative changes. This information may be helpful in diagnosing, monitoring, and developing comprehensive rehabilitation plans.