The present study aimed to determine whether TIS affects the degree of functional recovery in TASDH patients who required emergency craniotomy and removal of acute subdural hematoma. Various statistics were used in this study. Between the functional and poor recovery groups, only TIS showed a significant difference (Table 1). When a multivariate logistic regression model was applied, TIS and midline shift ≥ 10 mm on brain CT scan had a significant effect on functional recovery (Table 2). TIS was further analyzed with the ROC curve. To greatly improve the chance of achieving good functional recovery, the analysis result revealed that TIS should be within 2 hours and 57.5 minutes.
In previous studies, such as that of Dent et al. (1995), counter-intuitive results have shown that a shorter TIS is correlated to poor functional recovery [2, 17]. However, such event is attributed to the existence of significant selection bias because patients with more severe injuries are more likely to undergo earlier surgery. This selection bias will certainly skew the results. Dent et al. (1995) have shown that patients who had surgery within 4 hours were more likely to have a lower Glasgow coma scale score, more severe intracranial injuries, and greater incidence of brain herniation than those who had surgery after 4 hours. To prevent a similar bias, only patients who had a coma scale score of 3–8, those younger than 70 years, and those who did not have additional structural brain injury other than TASDH were included. Moreover, patients with torso injuries were excluded as such conditions are commonly accompanied with hypotension and additional systemic complication. A multivariate logistic regression analysis that includes multiple variables will significantly reduce the likelihood of selection bias.
In the hypothesis of Mathai et al. (2010), the onset of life-threatening brain swelling in patients with severe TBI occurs between 2–3 hours after the injury and may be attributed to the osmotic load exerted by the breakdown of debris in the membrane and cytoplasmic structures [13]. In the report of Haselsberger et al. (1988), the surgical outcomes of TASDH patients were influenced by preoperative consciousness status [5]. When the time interval between onset of coma and surgical decompression exceeded 2 hours, the mortality rate increases from 47–80%. Meanwhile, Seelig et al. (1981) have reported an increase in mortality rate from 30–90% if TIS exceeds 4 hours [15]. Our study is similar to the previous study; however, the current study focused on the functional outcomes of TASDH patients who were in coma and required emergency surgical operation. Our statistical analyses revealed that TIS was a significant factor and that the threshold time for surgery on TASDH patients must be assessed to achieve functional recovery.
With regard to the factors influencing outcomes, the impact of age and coma scale on functional recovery have been studied most frequently in the past [6, 7, 12]. Our data did not show that younger patients or those with a higher coma scale score were more likely to obtain better outcomes (Table 1), and this result may be attributed to two reasons. First, only 70 sets of data were included in our study, which may be considered a small sample size. Second, based on our exclusion criteria, 19 patients who were older than 70 years (n = 8, severe neurological deficit; n = 7, vegetative state; n = 4, dead) and 16 patients with a coma scale score of 3 or 4 with bilateral pupil dilatation (n = 3, vegetative state; n = 13, dead) were not included. Thus, age and coma scale score were considered not significant factors.
According to our multivariate logistic regression analysis, midline shift ≥ 10 mm on brain CT scan was another significant variable (Table 2). A patient with midline shift ≥ 5 mm on brain CT scan will experience prominent elevated ICP requiring surgical intervention [1]. In our study, we hypothesized that midline shift ≥ 10 mm on brain CT scan is associated with poor outcomes. The Rotterdam CT score is another tool that can be used to predict long-term outcomes via brain CT scan [10, 11]. A higher Rotterdam score indicated a more severe brain injury, which is correlated to poor outcomes. To the best of our knowledge, this report first showed that midline shift ≥ 10 mm on brain CT scan was associated with poor outcomes.
As with all studies, the present study had some limitations. It had a small sample size and was conducted at a single center. Some exclusion criteria were also applied to age and coma scale score. Nevertheless, this study can be helpful in understanding the importance of TIS in patients with TBI and can provide valuable contributions in future-related studies.
The time lapse from injury was considered a critical factor based on the study of Seelig et al. (1981) in 1981. However, several authors have obtained different conclusions [8, 9, 11, 17, 21, 22]. Our study included TASDH patients who were surgically treated from 2008 to 2015. With the use of the exclusion criteria, we believe that our sample is reasonable and that some obvious selection biases were eliminated. Thus, TIS is an important factor for the functional recovery of TASDH patients. Midline shift ≥ 10 mm on brain CT scan is another important factor associated with poor recovery.