Role of Magnetic Resonance Imaging in Acute Head Injury Patients with Normal Computed Tomography Brain Findings

ABSTRACT

Background:

Traumatic brain injury (TBI) is a major cause of morbidity and mortality. Computed tomography (CT) is the first-line imaging modality in acute head injury; however, patients with altered neurological status may show normal CT findings. Magnetic resonance imaging (MRI), with superior soft-tissue contrast, can detect subtle intracranial injuries missed on CT.

Aim:

To evaluate the role of MRI in head injury patients with altered Glasgow Coma Scale (GCS) scores and normal CT findings.

Materials and Methods:

This hospital-based cross-sectional study was conducted in the Department of Radiology, Aarupadai Veedu Medical College and Hospital, Puducherry, from November 2023 to May 2024. Ninety-two patients aged 18–60 years with acute traumatic head injury, altered GCS, and normal CT brain findings were included. MRI was performed using a 1.5-T scanner with T1 Weighted Imaging (T1W), T2 Weighted Imaging (T2W), T2 Fluid Attenuated Inversion Recovery (T2-FLAIR), Diffusion Weighted Imaging (DWI), and Susceptibility Weighted Imaging (SWI) sequences. MRI findings were correlated with GCS scores. Data were analyzed using descriptive statistics and Chi-square test, with P < 0.05 considered significant.

Results:

MRI detected small contusions (81.5%), edema (80.4%), thin SDH (60.9%), microhemorrhages (48.9%), nonhemorrhagic DAI (46.7%), hemorrhagic DAI (34.8%), brainstem injury (41.3%), and thin SAH (28.3%). Hemorrhagic DAI, nonhemorrhagic DAI, microhemorrhages, and edema showed significant association with GCS scores (P < 0.05).

Conclusion:

MRI is an essential complementary modality in acute head injury with normal CT findings, improving diagnostic accuracy, prognostication, and clinical management.

INTRODUCTION

Head injury remains a major public health problem worldwide and is a leading cause of mortality and long-term disability, particularly among young and middle-aged individuals. In India, the burden of traumatic brain injury (TBI) is substantial, with a reported prevalence of 25.7 per 1,000 population.[1] Road traffic accidents account for the majority of cases, followed by falls, and hospital-based studies report mortality rates of approximately 20–22%, underscoring the significant socioeconomic and healthcare impact of TBI.[2] Neuroimaging is central to the evaluation of head injury. Computed tomography (CT) is the primary imaging modality in the acute setting due to its rapid availability and effectiveness in detecting skull fractures, intracranial hemorrhage, cerebral edema, and herniation.[3] CT-based scoring systems are widely used for prognostication. However, CT has limited sensitivity for subtle parenchymal injuries, and a considerable proportion of patients with persistent neurological symptoms may demonstrate normal CT findings, raising concerns of underdiagnosis.[4]

Magnetic resonance imaging (MRI), with superior soft-tissue contrast, offers improved detection of occult injuries such as diffuse axonal injury (DAI), microhemorrhages, nonhemorrhagic contusions, and ischemic changes using sequences including T1W, T2W, FLAIR, DWI, and SWI.[5] Early identification of these lesions is crucial for explaining ongoing symptoms, refining prognosis, and guiding management. The present study evaluates the role of MRI in acute head injury patients with normal CT findings.

MATERIALS AND METHODS

This hospital-based cross-sectional study was conducted in the Department of Radiology, Aarupadai Veedu Medical College and Hospital, Kirumampakam, Puducherry, from November 2023 to May 2024. Ethical approval was obtained from the Institutional Human Ethics Committee (IHEC No.: AV/IHEC/2024/090), and written informed consent was obtained from all participants. Ninety-two patients aged 18–60 years with acute TBI, altered GCS, and normal noncontrast CT brain findings were included using purposive sampling. Patients with nontraumatic pathology, CT-detected parenchymal abnormalities, pregnancy, or contraindications to CT or MRI were excluded. Sample size was calculated based on the study by Lindberg et al., assuming 96% MRI sensitivity, 4% precision, 5% significance level, and 90% power.[6] CT imaging was performed using a 16-slice GE Brivo CT-385 scanner, followed by MRI on a 1.5-T Philips Achieva system using T1W, T2W, T2-FLAIR, DWI, and SWI sequences. Clinical details and MRI findings were documented systematically. Data were analyzed using SPSS version 26.0 with descriptive statistics and the Chi-square test; P < 0.05 was considered statistically significant.

RESULTS

Table 1 depicts hemorrhagic and nonhemorrhagic diffuse axonal injury showed a significant association with GCS scores (P = 0.001), with a higher prevalence in patients with moderate and severe GCS. Both injury types were uncommon in mild head injury, indicating greater severity with worsening neurological status.

Table 1.

Association of Glasgow Coma Scale score between hemorrhagic diffuse axonal injury and nonhemorrhagic diffuse axonal injury among the study participants

GCS Score	Hemorrhagic Diffuse axonal injury		P
	Present	Absent
Mild	0	16	0.001*
Moderate	19	39
Severe	13	5
GCS Score	Nonhemorrhagic Diffuse axonal injury		P
	Present	Absent
Mild	1	15	0.001*
Moderate	29	29
Severe	13	5

*Significant. GCS=Glasgow Coma Scale

Table 2 depicts microhemorrhages, which showed a statistically significant association with GCS, occurring more frequently in patients with moderate and severe head injury (P = 0.007). In contrast, small contusions showed no significant association with GCS scores (P = 0.32).

Table 2.

Association of Glasgow Coma Scale score between microhemorrhage and small contusion among the study participants

GCS Score	Microhemorrhage		P
	Present	Absent
Mild	4	12	0.007*
Moderate	27	31
Severe	14	4
GCS Score	Small contusion		P
	Present	Absent
Mild	15	1	0.32
Moderate	45	13
Severe	15	3

*Significant. GCS=Glasgow Coma Scale

Table 3 depicts cerebral edema, which showed a significant association with GCS, being more frequent in patients with moderate and severe head injury (P = 0.04). In contrast, brainstem injury was not significantly associated with GCS scores (P = 0.32).

Table 3.

Association of Glasgow Coma Scale score between edema and brain stem injury among the study participants

GCS Score	Edema		P
	Present	Absent
Mild	16	0	0.04*
Moderate	46	12
Severe	12	6
GCS Score	Brain Stem injury		P
	Present	Absent
Mild	5	11	0.32
Moderate	23	35
Severe	10	8

*Significant. GCS=Glasgow Coma Scale

Table 4 shows that thin subarachnoid hemorrhage and thin subdural hemorrhage were not statistically significantly associated with GCS scores (P = 0.79 and P = 0.51, respectively). These findings were observed across all GCS categories without a clear relationship to injury severity.

Table 4.

Association of Glasgow Coma Scale score between thin SAH and thin SDH among the study participants

GCS Score	Thin SAH		P
	Present	Absent
Mild	5	11	0.79
Moderate	15	43
Severe	6	12
GCS Score	Thin SDH		P
	Present	Absent
Mild	11	5	0.51
Moderate	36	22
Severe	9	9

*Significant. GCS=Glasgow Coma Scale

DISCUSSION

In the present study, hemorrhagic and nonhemorrhagic DAI were predominantly observed in patients with moderate and severe head injury, with minimal occurrence in mild cases, demonstrating a strong correlation between axonal injury and neurological severity. The study conducted by Adams et al. in 1989 and Javeed et al. in 2021 has similar findings reported that DAI was most commonly observed in patients with moderate to severe TBI, with very few cases in mild injuries, demonstrating the correlation between neurological severity and axonal damage.[7,8] The study conducted by Hilario et al. in 2025 has similar study findings, reporting that nonhemorrhagic DAI was primarily seen in patients with moderate and severe TBI, while it was uncommon in mild cases, highlighting the correlation between injury severity and axonal damage.[9]

Microhemorrhages were frequently detected in moderate to severe TBI, whereas small contusions were identified across all GCS categories, underscoring the superior sensitivity of MRI in detecting subtle parenchymal injuries even in mild head injury. Cerebral edema was commonly observed, particularly in mild to moderate injuries, supporting previous evidence that MRI can identify early parenchymal changes not visible on CT. The study conducted by Irimia et al. in 2018 has similar findings which found that microhemorrhages were more frequently seen in patients with moderate to severe TBI, with very few cases in mild injuries.[10] The study conducted by Wintermark et al. in 2015 has similar study findings noting that small contusions were frequently detected on MRI even in patients with mild TBI and normal CT scans, highlighting MRI’s superior sensitivity in identifying minor parenchymal injuries.[11]

Thin subarachnoid and subdural hemorrhages were present across all grades of head injury without a clear association with GCS severity, aligning with studies demonstrating MRI detection of thin extra-axial bleeds despite normal CT findings. The study conducted by Zusman et al. in 2020 found similar study findings that MRI detected cerebral edema in a substantial proportion of patients with mild to moderate TBI who had normal CT scans, emphasizing that MRI is more sensitive in identifying early parenchymal changes.[12] The study conducted by Kim et al. in 2013 has similar study findings noting that thin SDH could be detected on MRI in patients with normal CT scans across all GCS categories, particularly in cases of mild to moderate TBI.[13]

Brainstem injuries were more prevalent in moderate and severe cases, consistent with prior literature highlighting MRI’s ability to detect critical brainstem lesions missed on CT. The study conducted by Shanmuganathan et al. in 2004 has similar study findings noting that brain stem lesions were often identified on MRI in patients with moderate to severe TBI who had normal CT scans, emphasizing the sensitivity of MRI in detecting injuries in critical regions of the brain that are easily missed on CT.[14]

CONCLUSION

The present study demonstrates that MRI is a highly valuable modality for detecting subtle intracranial injuries in acute head trauma patients with normal CT findings. Although CT is the first-line investigation, it may miss lesions such as DAI, microhemorrhages, small contusions, brainstem injuries, and early cerebral edema, which were effectively identified on MRI in this study. MRI-detected hemorrhagic and nonhemorrhagic DAI, microhemorrhages, and cerebral edema showed a significant association with lower GCS scores, particularly in moderate and severe head injuries. In contrast, small contusions and thin SAH or SDH were observed across all GCS categories, indicating that subtle injuries may be present even in clinically mild cases. Early MRI, preferably within 24–48 h of injury, is therefore crucial for timely diagnosis, appropriate management, and prevention of long-term complications, establishing MRI as an essential complementary tool in acute head injury evaluation.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.