Limitations of Head CT in Detecting Traumatic Brain Injury

Imaging Limitations of CT

CT scans frequently miss microhemorrhages that are only visible with susceptibility‑weighted MRI sequences, indicating that a normal CT does not rule out these subtle injuries. 1
A normal CT does not completely exclude traumatic brain injury, especially for mild or diffuse injury patterns such as diffuse axonal injury. 1

In approximately 25 % of pediatric patients with suspected brain injury, MRI reveals clinically relevant findings that are not seen on CT, supporting the use of MRI when CT is incongruent with the clinical picture. 1
Diffusion‑weighted imaging (DWI) is the most sensitive MRI technique during the acute phase (first few days) because cytotoxic edema produces restricted water diffusion, making DWI essential for early detection of injury. 1

Patients with mild TBI (Glasgow Coma Scale 14‑15) can be discharged safely after a 6‑hour observation period if both the clinical exam and CT are normal, yet they remain at risk for later cognitive, psychosocial, and neurobehavioral problems even when imaging is unremarkable. 2
Up to 1.5 % of patients with a GCS 15 may deteriorate after the initial assessment, and 57 % of these deteriorations occur within the first 24 hours, independent of the initial CT findings. 2

Written discharge instructions and involvement of a responsible third party are crucial because 23 % of mild TBI patients poorly recall verbal instructions, increasing the risk of missed complications despite a normal CT. 2

Head CT remains the first‑line imaging modality because it rapidly identifies life‑threatening lesions that require immediate neurosurgical intervention. 3
Less than 1 % of mild TBI patients with a GCS 15 have lesions that ultimately need neurosurgical treatment, underscoring the high negative predictive value of a normal CT for surgically actionable injuries. 3