There is insufficient evidence to support a strong, moderate or weak strength recommendation about the accuracy of screening for diagnosis of pTBI.

• Given limited accuracy, routine plain x-rays are not recommended in the screening of pTBI.

In the absence of direct scientific evidence, EXPERT CONSENSUS concluded that:

• CT scanning is recommended to screen patients for pTBI. (100% consensus)

No evidence or expert opinion supported distinct recommendations based on patient gender, age, wounding mechanism, or military vs. civilian context.

pTBI has one of the highest case fatality rates among all injury types. Mortality rates exceeding 90% have been reported for patients with GSW to the head in some studies. pTBI is not always obvious, as can be the case with nail gun injuries and when a stabbing implement is removed after causing injury. Consequently, it is crucial to screen patients for penetrating head wounds upon their arrival at the ED to prevent morbidity and mortality later during their hospital stay. Screening methods vary and can include standard CT scans, plain radiography, and physical examinations. The exploration of new and evolving technologies, such as blood-based biomarkers is still in its early stages, with insufficient evidence to assess their efficacy fully. Thus, imaging modalities and physical examinations remain the most thoroughly researched and effective tools for the initial screening of pTBI.

The first edition of the pTBI guidelines did not address the use of screening modalities.16 The prior guidelines did address the use of CT scan for the evaluation of patients with penetrating brain injury. They stated:

This recommendation was made at the option level based on 23 class III studies.38-40,61,64-81 These studies were all retrospective in nature and describe the merits and limitations of available diagnostic imaging studies, but do not directly discuss the imaging modalities affect on outcomes. Those 23 studies were excluded from consideration in these guidelines based on the methodology used. The 23 studies cited in the last guideline did not include a diagnostic accuracy which was the basis of the key question under consideration. Additionally, many of those earlier studies were from the pre-CT era or compared plain films to CT. There were no studies that compared CT to another "gold standard" thus eliminating them as possible considerations for a key question defined by diagnostic accuracy. It also deserves mention that in the first edition of these guidelines numerous CT findings were associated with poorer prognosis which provides further support for the importance of CT imaging.

Only one study, published by Exadaktylos et al, was identified as meeting inclusion criteria that was pertinent to the key question on attempting to identify the best tools for screening and diagnosis of pTBI in the prehospital and ED setting82 (Table 6). The non-randomized study included 179 patients with stab wounds to the head, attending a trauma unit in Switzerland. They performed anterior-posterior and lateral view skull radiographs on all patients who later underwent head CT to diagnose penetration of the skull. The study reported skull X-rays identified 35 penetrating skull injuries, while follow-up CT identified 128. Assuming X-ray did not identify any false positive penetrating injuries (i.e., penetrating injuries on X-ray that were later identified as non-penetrating on CT), resulted in a sensitivity of X-ray of 27.34%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 35.42%. This study is rated high risk of bias given unclear reporting with a need to assume no false positive cases. This study provides very low strength evidence that X-ray plain films are not accurate at identifying trauma patients who have a penetrating injury.

Seven non-randomized studies, not meeting inclusion criteria because they did not report diagnostic accuracy data, are reported here for completeness.10,58,83-87 The studies ranged in sample size from 30 to 7762; four studies (57%) included over 600 patients, with the other three including less than 100.58,85,87 All but one study was conducted in civilian populations;10 four in the United States, and one each in Germany, Turkey, and Austria.

Six studies reported the Glasgow Coma Scale (GCS) score by those with penetrating and those without penetrating head injuries, four reported this as a percent meeting specific GCS scores or ranges of scores, while one reported median scores58 and the other appears to report mean scores (though the study does not report the unit of measure)85 (Table 7). All studies reported more patients with pTBI GCS scores of 3, 3 to 5, or 3 to 8 and more patients with blunt head injuries had GCS scores of 9 to 15, 13 to 15, and 14 to 15; two studies reported these differences as statistically significant. One study reported a higher median GCS score in those with blunt injuries compared with pTBI (median, blunt vs pTBI: 15 vs 11, P < .05) and another reported higher mean (implied mean, unit not reported) GCS scores at admission with blunt injuries compared with pTBI (mean GCS, blunt vs pTBI: 11.3 vs 3.3, P < .05).

Two studies (N = 816) reported the Injury Severity Score (ISS) for those with penetrating and those without penetrating head injuries (Table 8). The first by Demetriades et al (N = 760) reported there was no difference in scores between types of head injury (mean ISS, pTBI vs blunt: 27 vs 26, P = .18 overall and N = 497, 22 vs 23, P = .92 when excluding those who were dead on arrival or had extracranial injuries.84 The second study by Icer et al (N = 56) did not report statistical significance (median ISS, pTBI vs blunt: 25 vs 9).58 The Icer study (N = 56) also reported the Revised Trauma Score (RTS) and Trauma Score-Injury Severity Score (TRISS), with no differences in median scores between those with pTBI and those without (RTS, pTBI vs blunt: 30 vs 26; TRISS, pTBI vs blunt: 91 vs 99.2).58 In addition, the Icer study (N = 56) reported no differences in pupil light reflex between those with pTBI and those without.58 Demetriades et al (N = 760) reported no differences in the rate of hypotension between those with pTBI and those without (systolic blood pressure <90 mm Hg, pTBI vs blunt: 12% vs 10%, P = .37).84

The management and initial assessment of patients with suspected pTBI in the field, austere environments, or even in the ED presents significant challenges. The lack of specific tools for the screening and diagnosis of pTBI beyond standard trauma evaluations underscores a critical gap in emergency medical care. Despite the high mortality rates associated with pTBI, particularly those resulting from GSW to the head - where mortality rates can exceed 90% - there remains a substantial need for improved diagnostic and screening methodologies.

The importance of considering pTBI in any patient with an altered mental status or when a detailed history is not obtainable cannot be overstated. pTBI, especially, can be elusive and difficult to identify without a thorough and specific examination. The risk of overlooking such injuries is catastrophic, necessitating a high index of suspicion and a meticulous physical examination. This is true not only in uncontrolled field settings but also within the more structured environment of an ED.

Currently, imaging modalities such as CT scans and plain radiography, along with physical examinations, are the most reliable and researched methods for the initial screening of pTBI. These techniques, however, may not always be readily available in prehospital or austere settings, highlighting the urgent need for portable, efficient, and effective diagnostic tools.

Emerging technologies, including blood-based biomarkers, hold promise for the future of pTBI diagnosis. Nonetheless, these innovations are still in the nascent stages of development, with insufficient evidence to fully validate their efficacy. The potential of such technologies could revolutionize the way pTBI is diagnosed, especially in environments where traditional imaging equipment is not accessible. The discussion around the need for specific tools for pTBI screening and diagnosis in the field and austere environments, as well as in emergency settings, is not just academic - it is a matter of life and death. The current evidence base is lacking in robust studies that evaluate the effectiveness of various modalities and tools for this purpose. The high case fatality rates associated with penetrating head wounds demand an aggressive approach to screening and diagnosis, emphasizing the importance of ongoing research and innovation in this field.

Future studies should focus on evaluating the accuracy of various screening tools and diagnostic methods in identifying pTBI. This includes traditional assessments like the Glasgow Coma Scale and pupil response, as well as potential biomarkers (e.g., s100b, UCH-L1, GFAP, tau, NSE, neurofilament/NF-1, cytokines, SNP, EEG) that could offer novel insights into brain injury. Additionally, the effectiveness and precision of imaging techniques such as MRI, CT scans, and plain films in detecting pTBI need thorough investigation. Comparing these modalities against established standards will help elucidate their reliability and feasibility, especially in settings where resources are limited.