La esposa emancipada

Haemorrhagic transformation of an infarct:

•

Can be diffi cult to distinguish from primary intracerebral haemorrhage

•

An infarct is more likely if there is a wedge- shaped abnormality extending to the cortex or small area of hyperdensity within a larger low attenuation area.

Arteriovenous malformation:

•

Multiple dilated veins and arteries separated by intervening brain tissue

•

MRI demonstrates multiple fl ow voids with serpentine contrast enhancement without signifi cant brain parenchymal enhancement

•

Usually an incidental fi nding without prece- ding haemorrhage, but arteriovenous malfor- mations do occur in the basal ganglia, and this can be diffi cult to distinguish.

Venous infarction:

•

More commonly haemorrhagic than arterial infarction, and aff ects the white matter rather than the cortex

•

Sometimes, but not always, an adjacent throm- bosed sinus can be seen.

Haemorrhagic neoplasm:

•

Can be primary or secondary

•

Mixed signal intensities with enhancing components.

Notes

Spontaneous intracranial haemorrhage is the second most common cause of stroke after ischa- emic stroke and is usually hypertensive in aetio- logy in adults.

On CT, hyperacute haematoma will appear of high density except in the context of severe anaemia. Over time, the density decreases, with the clot

becoming isodense to brain over a period of weeks.

Bibliography

Dainer HM, Smirniotopoulos JG. Neuroimaging of hemor- rhage and vascular malformations. Semin Neurol 2008; 28(4):533–547

176

4 Neurological Imaging

4.20 Traumatic Brain Injury

Fig. 4.20.1

Fig. 4.20.2

Fig. 4.20.3

Fig. 4.20.4

Clinical History

A 20-year-old motorcyclist has been involved in a road traffi c accident and has a Glasgow Coma Score of 3

(Figs. 4.20.1–4.20.5).

Ideal Summary

These are unenhanced axial CT images on brain parenchymal and bony windows. There are exten- sive, bilateral, haemorrhagic contusions within the

RZ Sidhu_9783131662910_2013_Section 4.indd 176

4.20 Traumatic Brain Injury

Fig. 4.20.5

Fig. 4.20.6

temporal lobes (Fig. 4.20.3, arrows). In addition, there is a shallow acute subdural haematoma over- lying the right frontoparietal convexity (Fig. 4.20.1, arrow), with widespread subarachnoid blood. There is signifi cant mass eff ect with midline shift to the left and eff acement of the right lateral ventricle (Fig. 4.20.2, arrow). On review of the bony windows, there is a complex comminuted fracture through the left parietal bone that extends to involve the petrous temporal bone (Figs. 4.20.4 and 4.20.5, arrows). On

closer inspection, there is apparent disruption of the left incudomalleal joint and haemotympanum (Fig. 4.20.4, arrowhead). There is high-density blood in the sinuses, and I would like to review the remaining images carefully for evidence of orbital fracture. The fi ndings are in keeping with severe traumatic brain injury. In our institution, this pati- ent would be managed in a neurointensive unit with neurosurgical input.

178

4 Neurological Imaging

Take your time and look at all of the available imaging. Do not be rushed into talking about the fi rst thing that you notice and then altering your interpretation when something more important is evident.

Describe each compartment of the head fully before moving onto the next section:

•

Brain parenchyma

•

Extra-axial compartment—subarachnoid and sub- and extradural layers

•

Bony skull

•

Soft tissue

The order of the compartments is up to you; just make sure you are comfortable with each section before moving on.

Comment on the primary abnormality and then the sequelae:

•

Intraparenchymal or extra-axial haemorrhage, which causes a mass eff ect (midline shift, and eff acement of the ventricular system or basal cisterns)

•

Petrous temporal bone fractures, causing ossi- cular disruption.

Remember the patterns of trauma:

•

Diff use axonal injury = grey–white matter junction

•

Cerebral contusions = frontal and temporal lobes. Comment on complications:

•

Herniation—tonsillar, uncal, and subfalcine

•

Hydrocephalus

•

Possible ossicular disruption, cerebrospinal fl uid (CSF) leak, and orbital entrapment. Always ask for imaging with bone windows if this

has not already been provided; only comment on fractures when these images are available. Are there any abnormalities that require urgent

intervention? If so, summarise and tell the examiner what you would recommend at your institution—usually neurosurgical referral.

Diff erential Diagnosis

There are no diff erentials for the above imaging fi ndings in the context of trauma.

Notes

CT is the mainstay of imaging in the assessment of head injury and is primarily used to identify pati- ents who may require intervention, neurosurgical or otherwise.

MRI may subsequently be employed to identify further lesions where the clinical—radiological image does not match, or to characterise unexp- lained abnormalities initially found on CT. Subarachnoid haemorrhage:

•

This is seen on CT as high density in the sub- arachnoid spaces.

•

On MRI, blood may be isointense with brain parenchyma, producing a “dirty” CSF picture.

•

Fluid-attenuated inversion recovery sequences are more sensitive than CT in the detection of small-volume subarachnoid blood.

Cerebral contusions:

•

These occur in typical locations where the brain parenchyma lies adjacent to a “rough” bony surface or a dural fold.

•

Classic locations are the temporal lobes (tem- poral pole, inferior surface), frontal lobes (frontal pole, inferior surface), and parasagittal parenchyma.

•

Look for contusions underlying a skull fracture. Diff use axonal injury:

•

The initial CT is normal in 50 to 80%.

•

Typical locations at the grey–white matter junction of the frontotemporal lobes, corpus callosum, and upper brainstem.

•

MRI is more sensitive than CT for the detec- tion of lesions—gradient-echo imaging is the sequence of choice in many institutions.

Bibliography

Provenzale JM. Imaging of traumatic brain injury: a review of the recent medical literature. AJR Am J Roentgenol 2010;194(1):16–19

RZ Sidhu_9783131662910_2013_Section 4.indd 178

180

In document École des Hautes Études en Sciences Sociales (página 105-111)