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All of the following statements about Diffuse Axonal Injury (DAI) are true Except: (AI 2009)

A Caused by shearing force

B Predominant white matter hemorrhages, in basal ganglion and corpus callosum

C Increased Intracranial tension is seen in all cases

D Most common at junction of grey and white matter

Ans. C

Increased Intracranial tension is seen in all cases

Diffuse Axonal Injury (DAI)

1). Diffuse axonal injury represents the presence of wide spread axonal damage (white matter) in both hemispheres, secondary to severe head injury

2). DAI results from application of severe acceleration / deceleration or angular rotational to the brain which results in injuries to the axons by a shearing force shear injuries

Pathobiological Features

1). Focal (irreversible) disruption of axons (white matter) at multiple places in both hemispheres (occurs at the moment of injury) white matter tears

2). These white matter tears may be haemorrhagic or non-hemorrhagic

3). When non haemorrhagic they are edematous (Non haemorrhagic lesions are not detected by CT scan but may be recognized on MRI as it picks up edema)

4). The most frequent location of tears is in the white matter at the junction of GREY and white matter

Frequent location of tears

1). Lobar white matter at junction of Grey and white matter (commonest location) - Frontal/ Temporal lobe > Parietal lobe /Occipital lobes

2). Corpus Callosum (Second most commonly involved location)

3). Brain stem (Third most commonly involved location)

Clinical presentation

1). Clinical presentations may however range from symptoms of concussion to coma

2). Loss of consciousness is a common finding and DAI is the commonest cause of post traumatic vegetative state

3). Raised intracranial tension may or may not be associated


1). Many of these injuries are likely to go undetected by any imaging modality

2). DAI may be recognized on CT scan and MRI (MRI > CT scan)

CT scan

1). CT scan often fails to recognize DAI lesions because most lesions are small and non haemorrhagic (CT scan is often normal)

2). CT scan can usually detect only those lesions that are large and haemorrhagic

MRI: MRI is more sensitive than CT scan for detecting DAI MRI can recognize smaller lesion than CT scan and also non haemorrhagic lesions from associated edema

Prognosis: Diffuse Axonal injury carries an extremely poor prognosis

Extra Edge:

Raised intracranial tension may be present in cases of Diffuse Axonal injury (DAI) but it is not seen in all cases of DAI. The presence of raised ICT is not needed for a diagnosis of DAI

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