Cause of Concussion with Persisting Symptoms is Associated with Long-Term Recovery and Symptom Type, Duration, and Number in a Longitudinal Cohort of 600 Patients.

It is important for patients and clinicians to know the potential for recovery from concussion as soon as possible after injury, especially in patients who do not recover completely in the first month and suffer from concussion with persisting concussion symptoms (C+PCS). We assessed the association between the causes of concussion and recovery from C+PCS in a consecutive retrospective and prospective cohort of 600 patients referred to the Canadian Concussion Center (CCC) at Toronto Western Hospital. Data was obtained from clinical records and follow-up questionnaires and not from a standardised database. A novel method was used to assess long-term recovery, and multivariable Cox PH models were used to assess relationships between cause of concussion and time to recovery. We examined the subsequent recovery of patients who had not recovered after at least one month from the time of concussion. Patients were grouped into the following four causes: sports and recreation (S&R, n=312, 52%); motor vehicle collisions (MVC, n=103, 17%); falls (n=100, 17%); and being struck by an object including violence (SBOV, n=85, 14%). The MVC group had the highest percentage of females (75.7%), the oldest participants (median:40.0 [IQR:30.5-49.0] years), the most symptoms (median:11.0 [IQR:8.5-15.0]) and the longest symptom duration (median:28.0 [IQR:12.0-56.00] months). In contrast, the S&R group had the highest percentage of males (58.1%), the youngest participants (median:20.0 [IQR:17.0-30.0] years), the best recovery outcome, and shortest symptom duration (median:22.0 [IQR:8.0-49.5] months). Significant differences among the four causes included age (p<0.001), sex (p<0.001), number of previous concussions (p<0.001), history of psychiatric disorders (p=0.002) and migraine (p=0.001). Recovery from concussion was categorised into three groups: 1. Complete Recovery occurred in only 60 (10%) patients with median time 8.0 [IQR:3.5-18.0] months and included 42 S&R, 7 MVC, 8 falls, and 3 SBOV; 2. Incomplete Recovery occurred in 408 (68.0%) patients with persisting median symptom time of 5.0 [IQR:2.0 - 12.0] months; and 3. Unknown Recovery occurred in 132 (22.0%) patients and was due to lack of follow-up. In summary, the cause of C+PCS was associated with the type, number, and duration of symptoms and time required for recovery, although all causes of C+PCS produced prolonged symptoms in a large percentage of patients which emphasizes the importance of concussions as a public health concern requiring improved prevention and treatment strategies.