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Wednesday, January 07, 2009

Diffuse Axonal Injury is characterized by all except Increased Intracranial tension is seen in all cases

Question 75
Diffuse Axonal Injury is characterized by all except
a.       Due to Shearing Force
b.      Predominant white matter haemorrhages, in basal ganglia and corpus collosum
c.       Increased Intracranial tension is seen in all cases
d.      Most common at junction of grey & white matter
Answer
c. Increased Intracranial tension is seen in all cases
Reference
Harrison 16th Edition Page 2448
Nelson 15th Edition Chap 551
Sabiston: Chapter 41
QTDF
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Status
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Discussion
Rotation of the brain within the skull may lead to tearing of axons within the white matter of the brain, causing diffuse axonal injury. According to the theory of Ommaya and Gennarelli, mild injuries damage only subcortical axons, but increases in the rotational force involve progressively deeper areas of brain. There is little cerebral swelling and no increased intracranial pressure associated with this form of brain injury. A computed tomographic (CT) scan made immediately following such an injury may demonstrate hemorrhage in the corpus callosum and the superolateral aspect of the brain stem, but the remainder of the brain appears relatively normal, even though the patient may manifest severe neurologic damage. Months after the injury, the CT scan demonstrates that the bulk of the white matter is reduced. Magnetic resonance imaging (MRI) demonstrates diffuse, small, focal abnormalities limited to white matter tracts.
Explanation
Self Explanatory
Comments
The presence of widespread axonal damage of both hemispheres, a state called diffuse axonal injury, has been proposed as the explanation of persistent coma or vegetative state, but small ischemic-hemorrhagic lesions in the midbrain and low diencephalon are as often the cause.
Tips
Only severe shearing lesions that contain blood are visualized by CT, usually in the corpus callosum and centrum semiovale (; however, within days of the injury, MRI scan demonstrates such lesions throughout the white matter, especially with the use of gradient echo MRI sequences.

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