Objective: Recent evidence of persistent reporting of symptoms after mild Traumatic Brain Injury (mTBI) has come under question, with the suggestion that participants may be over-reporting symptoms more generally. This study set out to determine the proportion of people reporting atypical symptoms and to explore the relationship between acute (1 month) atypical symptom reporting and perceptions of recovery and experience of typical symptoms following mTBI.

Methodology: Data was drawn from the longitudinal population-based Brain Injury Incidence and Outcomes New Zealand (NZ) in the Community (BIONIC) study that was conducted in the Hamilton and Waikato districts. Cases included patients who had experienced a traumatic brain injury between the 1 st March 2010 and 28th February 2011. Cases were identified from the ACC database, community healthcare services, such as general practitioners (GPs) and physiotherapists, hospital admissions and discharges, sports clubs, concussion clinics and self-referrals. Participants completed the Rivermead Post-Concussion Questionnaire (RPQ) assessment at one month (n = 261) and twelve months post-injury (n = 193), in addition to data on a series of distractor (atypical) symptoms. Typical symptoms generally relate to post-concussion symptoms, while atypical symptoms do not form part of a concussion clinical presentation. Characteristics of the sample were analysed and the proportion of participants reporting atypical and typical mTBI symptoms were explored at both timepoints. T-tests were used when data satisfied parametric assumptions; if not satisfied, the Chi square tests tested non-parametric equivalent statistics (for nominal/categorical variables). The significance level was set at p <0.05. A regression analysis determined whether increased atypical symptoms reported at one month predicted persistent symptoms and perceptions of recovery at twelve months.

Results: Data was available for n = 261 participants at one month and n = 193 at twelve months. Atypical symptoms were reportedly experienced by 25% of participants at one month and 16% of participants at twelve months. Atypical symptom reporting was higher in females than males. Sex, ethnicity, atypical symptoms and typical symptoms at one month following mTBI were significantly predictive of the one-year outcome, explaining 46% in the variance in typical post-concussion symptoms and 31 % of the variation in perceptions of recovery.

Conclusion: One in four people reported atypical symptoms in the acute phase (intense symptoms at one month) post-injury, which reduced over time (twelve months). However, the models did not explain all the variance in the outcome, and other factors are likely to influence outcomes from mTBI. Given links to symptom reporting and perceptions of recovery at twelve months post-injury, acute atypical symptom reporting could be a red flag to indicate those who may experience poorer long-term outcomes and require additional support to facilitate recovery.