Longitudinal Study of Postconcussion Syndrome: Not Everyone Recovers

Abstract

We examined recovery from postconcussion syndrome (PCS) in a series of 285 patients diagnosed with concussion based on international sport concussion criteria who received a questionnaire regarding recovery. Of 141 respondents, those with postconcussion symptoms lasting less than 3 months, a positive computed tomography (CT) and/or magnetic resonance imaging (MRI), litigants, and known Test of Memory Malingering (TOMM)-positive cases were excluded, leaving 110 eligible respondents. We found that only 27% of our population eventually recovered and 67% of those who recovered did so within the first year. Notably, no eligible respondent recovered from PCS lasting 3 years or longer. Those who did not recover (n = 80) were more likely to be non-compliant with a do-not-return-to-play recommendation (p = 0.006) but did not differ from the recovered group (n = 30) in other demographic variables, including age and sex (p ≥ 0.05). Clustergram analysis revealed that symptoms tended to appear in a predictable order, such that symptoms later in the order were more likely to be present if those earlier in the order were already present. Cox proportional hazards model analysis showed that the more symptoms reported, the longer the time to recovery (p = 7.4 × 10^-6), with each additional symptom reducing the recovery rate by approximately 20%. This is the first longitudinal PCS study to focus on PCS defined specifically as a minimum of 3 months of symptoms, negative CT and/or MRI, negative TOMM test, and no litigation. PCS may be permanent if recovery has not occurred by 3 years. Symptoms appear in a predictable order, and each additional PCS symptom reduces recovery rate by 20%. More long-term follow-up studies are needed to examine recovery from PCS.

Keywords: definitions, eligibility, and exclusions; number of symptoms; postconcussion syndrome; recovery.

FIG. 1.

Flow chart for case selection. The criteria used for case selection of the cohort beginning with 285 cases, of which 120 were ultimately selected.

FIG. 2.

Persisting symptoms. The percentage of the not recovered group (NOT-REC; n = 80) suffering from continuing somatic, affective, and cognitive symptoms. Note that in those with persisting postconcussion syndrome, the persisting symptoms were quite evenly dispersed among somatic, affective and cognitive symptoms.

FIG. 3.

Time required to recover (n = 27) and duration of persisting postconcussion syndrome (PCS; n = 77): Note that no patient recovered after 3 years.

FIG. 4.

Clustergram of patients vs. symptoms. A heat map is shown in the central area, with each column representing a patient, and each row, a symptom. A red square in a particular row and column indicates the symptom for that row was present in the patient for that column; a black square represents the absence of the symptom. Dendrograms from agglomerative clustering analyses of both patients and symptoms appear at the top and left, respectively, where they have each been divided into two constituent groups. The 29 patients who had recovered are denoted by asterisks along the bottom edge. Symptoms in Group B were reported by significantly more patients than symptoms in Group A. Patients in Group 2 reported significantly more symptoms than patients in Group 1, and also were significantly more likely to have experienced post-injury depression and anxiety, to have tried medication and psychotherapy for treatment, and to have found these treatments effective. Color image is available online at www.liebertpub.com/neu

FIG. 5.

Recovery curves for patients reporting different numbers of symptoms from a Cox proportional hazards analysis. The number of symptoms associated with each curve is shown to the right of the figure at the end of each curve, with the percentage of patients in this range shown in parentheses. Color image is available online at www.liebertpub.com/neu

FIG. C1.

The proportion of variance explained by each principal component in a Principal component analysis of symptom occurrence. Following application of a permutation test, only the first component, explaining 23.9% of the total variance, was statistically significant at p < 0.0001.

FIG. C2.

Symptom loadings on the one significant principal component. All symptoms had positive loadings in this component except for vomiting, which had a small negative weight of −0.02.