Evidence of central and peripheral vestibular pathology in blast-related traumatic brain injury

Objective: To prospectively assay the vestibular and oculomotor systems of blast-exposed service members with traumatic brain injury (TBI). Study Design: Prospective, nonblinded, nonrandomized descriptive study. Setting: Tertiary care facility (Department of Defense Medical Center). Patients: Twenty-four service members recovering from blast-related TBI sustained in Iraq or Afghanistan. InterventionS: Focused history and physical, videonystagmography (VNG), rotational chair, cervical vestibular-evoked myogenic potentials, computerized dynamic posturography, and self-report measures. Results: Vestibular testing confirms a greater incidence of vestibular and oculomotor dysfunction in symptomatic (vestibular-like dizziness) personnel with blast-related TBI relative to asymptomatic group members. VNG in the symptomatic group revealed abnormal nystagmus or oculomotor findings in 6 of 12 subjects tested. Similarly, rotational chair testing in this group revealed evidence of both peripheral (4/12) and central (2/12) vestibular pathology. By contrast, the asymptomatic group revealed less vestibular impairment with 1 of 10 rotational chair abnormalities. The asymptomatic group was further characterized by fewer aberrant nystagmus findings (4/12 abnormal VNGs). Computerized dynamic posturography testing revealed no significant differences between groups. Self-report measures demonstrated differences between groups. Conclusion: Vestibular function testing confirms a greater incidence of peripheral vestibular hypofunction in dizzy service members with blast-related TBI relative to those who are asymptomatic. Additionally, oculomotor abnormalities and/or nystagmus consistent with central involvement were present in 10 of the 24 study participants tested. The precise cause of these findings remains unknown.