Abstract
We read with great interest the article by Maheshwarappa et al. 1 In this era of ever increasing utilization of medical imaging, 2 Maheshwarappa et al’s work investigated the value of repeat head computed tomography (CT) in patients with mild traumatic brain injury (TBI) and isolated traumatic subarachnoid hemorrhage (tSAH). This study is novel in its patient selection, with both inter-facility transfer and inpatient/outpatient follow-up subgroups, representing 2 important settings and time points of the disease progression when repeat head CT scans typically occur.
By examining the results of repeat head CT scans of 101 patients in the transfer subgroup and 140 patients in the follow-up subgroup, the article demonstrates that worsening SAH on the repeat head CT is uncommon in this patient population in the time-frames of both hours and weeks. Furthermore, in a small number of (5) scans that indeed showed increased SAH, the imaging finding did not change the clinical management or lead to neurosurgical intervention. These results are significant considering that a large proportion of the patients (54.6%) were on anticoagulation, and a small subset of patients with new neurological symptoms (8 scans) also demonstrated stable SAH on the repeat scans.
The authors conducted an analysis of unnecessary cost and radiation associated with the nonmanagement-modifying repeat head CT scans. The quoted cost for the head CT scans appears to be high by Canadian standards, but nevertheless radiology service is a finite resource. The practice of ordering unnecessary CT scans not backed up by evidence in medical research can have an even higher non-financial cost in the form of taking away scarce resources from other patients.
Although the number of patients demonstrating increased SAH on the repeat scan is small (5), it can be valuable to examine the clinical circumstances of these patients to identify potential factors for risk stratification in this patient population with a generally low likelihood of deterioration. Ideally, this can also be further investigated in future larger prospective studies to allow a sufficient number of cases for adequate statistical power.
The article would also benefit from further clarity regarding the patient selection process, particularly regarding patients in the transfer subgroup. Were there any patients who had a pre-transfer CT scan but did not receive a repeat post-transfer scan? If yes, how many were they, and why were the repeat scans not requested? Also, did any of the patients in the transfer subgroup develop “new neurological symptoms,” or were they excluded because of the exclusion criterion “neurological deterioration”?
Along with previous publications, Maheshwarappa et al’s study again highlighted the limited value of repeat head CT in patients with mild TBI and isolated tSAH, and validated this point in both transfer and follow-up patient subgroups. Future prospective multi-center studies with a larger sample size will be helpful to enhance this conclusion. Meanwhile, discussions with our emergency medicine, neurology, and neurosurgery colleagues will help radiologists to refine imaging guidelines and to develop consensus in clinical practice.