Clinical Studies
Immediate Neurocognitive Effects of Concussion

RESULTS

FIGURE 1. SAC form (from, McCrea M, Randolph C, Kelly JP: The Standardized Assessment of Concussion (SAC): Manual for Administration, Scoring and Interpretation. Waukesha, CNS, Inc., 2000, ed 2 [31]).

2) Immediate Memory: (all 3 trials are completed regardless of score on trial 1 & 2; total score equals sum across all 3 trials)

List	Trial 1	Trial 2	Trial 3
Word 1	0    1	0    1	0    1
Word 2	0    1	0 1	0 1
Word 3	0 1	0 1	0 1
Word 4	0 1	0 1	0 1
Word 5	0 1	0 1	0 1
Total

Immediate Memory Total Score____/ 15

(Note: Subject is not informed of Delayed Recall testing of memory)

NEUROLOGICAL SCREENING:

Loss of Consciousness: (occurrence, duration)

Retrograde and & Posttraumatic Amnesia:
(recall of events pre- and post-injury)

Strength:

Sensation:

Coordination:

3)Concentration:

Digits Backward (If correct, go to next string length.
If incorrect, read trial 2. Stop after incorrect on both trials)

4-9-3	6-2-9	_________0 1
3-8-1-4	3-2-7-9	_________0 1
6-2-9-7-1	1-5-2-8-6	_________0 1
7-1-8-4-6-2	5-3-9-1-4-8	_________0 1

Months in reverse order: (entire sequence correct for 1 point)
Dec-Nov-Oct-Sep-Aug-Jul
Jun-May-Apr-Mar-Feb-Jan_________0 1

Concentration Total Score________/ 5

Exertional Maneuvers
(when appropriate):

5 jumping jacks
5 push-ups
5 sit-ups
5 knee-bends

4) Delayed Recall

Word 101
Word 201
Word 301
Word 401
Word 501

Delayed Recall Total Score ______/ 5

Summary of Total Scores:

Orientation_______________/ 5
Immediate Memory_________/ 1
Concentration_____________/ 5
Delayed Recall_____________/ 5

Overall Total Score_______/30

Immediate neurocognitive effects of concussion

The mean SAC total score for all injured subjects immediately after injury was significantly less than the mean score for the larger population of participants who underwent preseason baseline testing at the start of the study [t(1,1280) = 14.02, P < 0.0001]. Scores for injured subjects were also less than the population mean baseline scores for noninjured subjects for the orientation, immediate memory, concentration, and delayed recall subtests of the SAC (Table 2). Similarly, paired-sample t tests revealed that the mean SAC total score for injured subjects who had undergone preseason baseline testing was significantly lower than baseline immediately after injury [t(1,44) = -10.07, P < 0.0001]. Mean scores for this group were also significantly lower immediately after injury for all four of the SAC subtests (Table 3).

Collectively, 95.6% of all injured subjects in the baseline protocol demonstrated lower SAC total scores at the time of injury, compared with their preinjury baseline scores, and 88.9% scored >2 points below their preinjury baseline SAC performance scores. No subject demonstrated an increase in SAC score at the time of injury, relative to baseline performance. Additionally, 84% of injured subjects scored below the population mean for the larger group of noninjured subjects in the study.

Early neurocognitive recovery

Figure 2 illustrates the significant decrease in SAC scores immediately after injury and the gradual slope of the cognitive recovery curve later after injury. The mean SAC score for injured subjects 15 minutes after injury (mean, 24.65; standard deviation, 4.95) remained significantly below the preseason baseline value [t(1,36) = -2.19, P = 0.035], but no significant impairment was detected with the SAC 48 hours or 90 days after injury. Scores for the immediate memory [t(1,36) = -2.43, P = 0.020] and delayed recall [t(1,36) = -2.83, P = 0.008] subtests of the SAC remained significantly below normal baseline values 15 minutes after injury but not 48 hours or 90 days after injury. No significant deficits were detected with the orientation and concentration subtests after the immediate postinjury assessment. A slight increase from the baseline SAC total score reached statistical significance at the 48-hour [mean, 27.33; standard deviation, 2.31; t(1,77) = 3.45; P = 0.001] and 90-day [mean, 28.28; standard deviation, 1.36; t(1,38) = 8.53; P < 0.0001] assessment points.

Effects of LOC and PTA on cognitive functioning

Table 1. Sample Characteristics for Baseline and No-baseline Protocols^a

^a SAC, Standardized Assessment of Concussion.
^b Statistics comparing subjects in the baseline and no-baseline protocols.
^c Values for injured sample are mean 6 standard deviation.
^d Statistics comparing baseline scores for injured and noninjured subjects.

Table 2. Standardized Assessment of Concussion Scores for Noninjured Subjects at Baseline and Injured Subjects Immediately after Concussion^a

^a SAC, Standardized Assessment of Concussion. Values are mean 6 standard deviation.
^b Statistically significant.

Table 3. Standardized Assessment of Concussion Scores for Injured Subjects at Baseline and Immediately after Concussion^a

^a SAC, Standardized Assessment of Concussion. Values are mean 6 standard deviation.
^b Statistically significant.

FIGURE 2. Mean SAC total scores for all injured subjects at preseason baseline, the time of injury, and 15 minutes, 48 hours, and 90 days after injury.

The three clinical groups performed significantly differently from each other on the SAC immediately after concussion, with the LOC group being most severely impaired and the no LOC/no PTA group being least impaired [F(2,88) = 53.08, P < 0.0001]. Post hoc comparisons with the Bonferroni correction revealed that the LOC group scored significantly lower than both the no LOC/no PTA group (mean difference, 11.86; P < 0.0001) and the PTA group (mean difference, 8.36; P < 0.0001). The PTA group also scored significantly below the no LOC/no PTA group immediately after injury (mean difference, 3.50; P = 0.007). Mean SAC scores for the three clinical groups and a summary of group differences are presented in Table 4.

On average, total scores immediately after injury were 2.43 points below the population baseline mean for the no LOC/no PTA group [t(1,75) = -8.22, P < 0.0001], 5.93 points lower than the population baseline mean for the PTA group [t(1,7) = -4.79, P = 0.002], and 14.29 points lower than the population baseline mean for the LOC group [t(1,6) = -6.53, P = 0.001]. One hundred percent of the LOC and PTA groups achieved SAC scores at the time of injury that were at least 2 points lower than their preinjury baseline performance scores, compared with 87.5% of the no LOC/no PTA group. Seventy percent of the no LOC/no PTA group achieved a score of <24 (10th percentile of the SAC normative baseline distribution) on the SAC immediately after injury, compared with 100% of the PTA group and 100% of the LOC group. Eight percent of the no LOC/no PTA group, 50% of the PTA group, and 100% of the LOC group scored <20 (1st percentile of the normative distribution) at the time of injury.

Figure 3 illustrates the pattern of immediate neurocognitive impairment and postinjury recovery, as measured by SAC scores, for subjects from the no LOC/no PTA, PTA, and LOC groups. Small sample sizes for the PTA and LOC groups and missing data at baseline times and at various follow-up points restricted formal statistical analysis, but these data graphically illustrate the magnitude of impairment immediately after concussion and the slope of the postinjury recovery curve for subjects with or without LOC and PTA.

Next section: Discussion and Conclusion