Dizziness Directly Influences Postconcussion Symptoms and Is Predictive of Poorer Mental Health in UK Military Personnel: A Retrospective Analysis.

OBJECTIVE: To investigate the contribution of dizziness to postconcussion symptoms, depression, and anxiety symptoms. SETTING: Mild traumatic brain injury (mTBI) service, Defence Medical Rehabilitation Centre, Stanford Hall. PARTICIPANTS: Two hundred eighty-three UK military personnel from the Royal Navy, Royal Airforce, Royal Marines, and British Army. DESIGN: A retrospective analysis of data from the Ministry of Defence medical records database. MAIN MEASURES: Sixteen-item Rivermead Post Concussion Symptoms Questionnaire, Generalized Anxiety Disorder 7-item scale, Patient Health Questionnaire-9, The Dizziness Handicap Inventory. RESULTS: Injuries from sports or falls were the most common mechanism of mTBI, accounting for 23%, respectively. Chi-square analysis indicated that individuals with dizziness and postconcussion symptoms (PCS) had greater severity of PCS, depression, and anxiety than those with PCS alone. Mediation analysis showed dizziness directly and independently influenced the severity of PCS, despite the indirect effects of mediating depression and anxiety symptoms. CONCLUSION: Comorbid dizziness and PCS were predictive of poorer mental health compared with PCS alone. In addition, dizziness directly influenced the severity of PCS irrespective of the indirect effects of mental health symptoms. These observations suggest that treating dizziness with vestibular rehabilitation may improve PCS and mental health.

Neuropsychiatric Outcomes in UK Military Veterans With Mild Traumatic Brain Injury and Vestibular Dysfunction.

OBJECTIVE: To estimate the frequency of vestibular dysfunction following blunt, blast, and combined blunt and blast mild traumatic brain injury (mTBI) and thereon assess the long-term impact of vestibular dysfunction on neurobehavioral function and disability independently of comorbid psychiatric symptoms. SETTING: Combat Stress residential and Veterans' Outreach drop-in centers for psychological support. PARTICIPANTS: One hundred sixty-two help-seeking UK military veterans. MAIN MEASURES: Self-reported frequency and severity of mTBI (using the Ohio State TBI Identification Method), Vertigo Symptom Scale, PTSD Checklist for DSM-5, Kessler Psychological Distress Scale (K10), Neurobehavioral Symptom Inventory, Headache Impact Test (HIT6), Memory Complaints Inventory, World Health Organization Disability Assessment Schedule II short version (WHODAS 2.0). RESULTS: Seventy-two percent of the sample reported 1 or more mTBIs over their lifetime. Chi-square analyses indicated that vestibular disturbance, which affected 69% of participants, was equally prevalent following blunt (59%) or blast (47%) injury and most prevalent following blunt and blast combined (83%). Mediation analysis indicated that when posttraumatic stress disorder, depression, and anxiety were taken into account, vestibular dysfunction in participants with mTBI was directly and independently associated with increased postconcussive symptoms and functional disability. CONCLUSION: Vestibular dysfunction is common after combined blunt and blast mTBI and singularly predictive of poor long-term mental health. From a treatment perspective, vestibular rehabilitation may provide relief from postconcussive symptoms other than dizziness and imbalance.

Synchronised vestibular signals increase the P300 event-related potential elicited by auditory oddballs.

The perception of beat within an auditory rhythm can be facilitated when accompanied by synchronised movements. Electrophysiological investigation shows that this facilitatory effect is associated with a larger P300 amplitude. It has remained unclear, however, which movement-related processes drive this P300 effect. To investigate whether vestibular signals play a role, we administered alternating, sub-sensory (mean=.3mA) galvanic current to the vestibular nerves of participants while they counted the number of oddballs presented in a stream of tones played at a rate of 1Hz. Consistent with a vestibular effect, the P300 elicited by the oddballs was increased during stimulation relative to a sham condition, but only when the frequency of the alternating current matched that at which the tones were played. This finding supports the general idea that the vestibular system is involved in audio-motor synchronisation and is the first to show by electrophysiological means that it influences cognitive processes involved in beat perception.