Teaching Case

A patient with a history of recent head trauma presented in a deep coma.

A 36-year-old male patient with a recent severe head trauma that occurred during an “inside-car” traffic accident (probably causing a severe acceleration-deceleration and rotational injury) came to the hospital in a deep coma state. A computed tomography of the cranium was performed, and multiple petechial to intermediate-sized hemorrhagic foci with hyperdense characteristics were detected within the thalami, partially mesencephalon, and subcortical white matter. A cranial MRI was performed on a 1.5T MRI scanner, with SE T1, FSE T2, FLAIR sequences in sagittal, axial and coronal planes 4 days later since the deep coma state did not change. The hemorrhagic foci were hyperintense on T1-weighted, and hypointense on T2-weighted and FLAIR sequences, representing intracellular methemoglobin (early subacute phase). The thalami and posterior corpus callosum were heterogeneously hyperintense on T2-weighted and FLAIR sequences, representing associated contusion. The patient died on the 5th day of admission to the hospital.

Diffuse axonal injuries or shearing injuries constitute the second most common type of traumatic injury of the brain. The acceleration/deceleration injury or shaking of the brain causes impaired axoplasmic transport, axonal swelling, and disconnection, thus, a state of axonal transection.

Diffuse axonal injury is frequently observed near interfaces between tissues of different consistency, so that shearing forces develop when rotation or acceleration/deceleration forces impart different velocities and momentum to parenchyma on each side of the tissue boundary. The most common locations of shearing injuries are grey-white matter junctions in the frontal and temporal lobes, corpus callosum, fornix, brainstem, basal ganglia, and internal capsule. The size of shearing injuries may range from a few millimetres to several centimetres. The lesions are commonly microscopic and non-haemorrhagic, however up to 50% of shearing injuries may be haemorrhagic. MRI is much more sensitive than CT studies of the cranium in detecting diffuse axonal injuries. CT studies demonstrate petechial haemorrhages in 20-50% of cases. MRI examinations show multiple foci with variable signal intensities, depending most importantly on the age of the haemorrhagic areas.

The most common clinical presentation of patients is with immediate coma following traumatic insult, with a variable course ranging from mild sequelae through severe sequelae to death.