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Subarachnoid
haemorrhage (SAH) is a commonly encountered clinical entity necessitating
the utilization of Angiography, in further investigating patients suspected
of having aneurysms as an aetiological factor for the SAH. Conventional
Angiography has its own risks, which become even more important in the
very young and in the elderly. Multislice CT has revolutionized CT Angiography,
increasing its accuracy phenomenally. We present here -a 77-year-old female
who presented with SAH.
Multiple intracranial aneurysms were detected by CT Angiography in this
patient obviating the need for conventional Angiography and thereby its
complications. |
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Introducton
SAH is a commonly encountered clinical entity, which necessitates an angiography
in patients suspected of having an aneurysm as an aetiological factor.
Multislice CT has revolutionized CT angiography, increasing its accuracy
henomenally. Conventional angiography has its own risks, particularly
in the very young and the elderly. CT cerebral angiography was performed
on a 77-year-old female who had presented with SAH. Multiple aneurysms
were detected on this study, thus obviating the need for a conventional
angiography. |
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Case
Report
A 77 year old female presented with headache and vomiting since 2 days.
She had a sudden onset of altered sensorium for one day and was referred
for a CT scan in view of the same. She also had past h/o left hemiparesis
4 years ago, from which she had recovered completely. There was no h/o
trauma (head injury) or hypertension. CT scan of brain with cerebral angiography
was performed on a multislice sub second spiral CT scanner (Volume Zoom
Siemens EMI). The non-enhanced CT scan revealed areas of extensive SAH,
which was more prominent in the left sylvian fissure, with an intraventricular
bleed and resultant moderate hydrocephalus. The patient was further evaluated
by CT angiography to rule out a vascular lesion (aneurysm) being a cause
of the non-traumatic SAH in this patient. CT cerebral angiography evealed
a 9 mm by 8 mm sized saccular aneurysm arising from the posterior wall
of the left ICA at the site of the PCOM artery origin. The ICA beyond
this saccular aneurysm was also dilated from which the MCA and the ACA
arose. There was presence of umbilication (tit sign) at the posterior
end of the aneurysm, which was suggestive of a leaking aneurysm. Other
aneurysms were noted at the left MCA bifurcation and the SCA origin. There
was a mass effect on the left PCA due
to the aneurysm. The vertebral and the basilar arteries were normal. |
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Technique
CT angiography was performed on a multislice CT scanner (Volume Zoom Siemens).
70 ml of ionic contrast media was injected via the right antecubital vein
at the rate of 2.5 ml/sec, using a pressure injector, with an empirical
delay of 14 seconds (12-35 sec). Image acquisition was done at 1.25 collimations
and axial reconstruction at 1.25 mm slice with 0.8 - 0.7 mm interslice
gap giving an overlapping image. These axial reconstructed images were
used for image processing i.e. Maximum Intensity Projection (Fig. 1),
Surface Shaded Display and Volume Rendering (Fig. 2). |
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Fig.
1 :
MIP axial image showing a large aneurysm at the
left PCOM artery origin and small aneurysms at
the left MCA bifurcation and SACA origin. |
Fig.
2 :
Volume rendered image showing the large aneurysm
at the left PCOM artery origin. |
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DISCUSSION
Catheter Angiography is considered as the gold standard in the evaluation
of intracranial aneurysms, it has its own risks and complications (1.5-2%)1
like thrombus formation, dissection, haematoma at the site of catheter
insertion, etc. In addition it is an invasive and expensive procedure.
Elderly patients usually have atherosclerotic vessels; hence
the morbidity and mortality rates rise significantly with catheter angiography
in this age group. The volume of contrast used, especially in such patients
who may require multiple runs, particularly due to difficult immobilization
while cquisition of images, is usually significantly more than in younger
age group. These drawbacks have led to the development of non-invasive
techniques such as MR angiography, Colour Doppler Ultrasound and CT angiography.
Currently with the advent of helical CT especially Multislice CT, CT angiography
can play a major role in the detection and
characterization of aneurysms in SAH, when the patient cannot undergo
DSA due to time considerations and other complications associated with
catheter angiography.
MR angiography has several disadvantages compared to CT angiography such
as poor demonstration of calcium and bony landmarks, artifacts, etc.
Colour Doppler ultrasound is an operator dependent modality and can yield
variable results. It has its limitations in the evaluation of the intracranial
vasculature, though transcranial Doppler has been used for the same.
In our case, in the acute stage of SAH, CT angiography was very suitable
as it did not require intra arterial catheterization, the scanning time
was less (only about 30 sec as compared to 30-40 minutes in catheter angiography,
depending a lot on patient compliance), and can immediately follow the
initial unenhanced CT examination.4 Recent
studies found CT angiography to detect 90% of all aneurysms associated
with acute SAH. It has a sensitivity ranging from 87 to 100% and specificity
of 50% to 100% for detection of intracranial aneurysms.5-7 CT angiography
provides more detailed information about the dome, neck, vessel of origin
and the surrounding anatomy of the aneurysm.2 This information significantly
alters the treatment options considered for the patient. |
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CONCLUSION
CT angiography is an evolving technique with a vast potential in neuro
vascular applications, particularly in the detection of aneurysms. CT
angiography serves as a problem solving modality in the characterization
of aneurysms that conventional
angiographic techniques show to be poorly defined or inconclusive.
CT angiography gave us a confirmative diagnosis of a ruptured aneurysm
in this case of acute SAH, thus obviating the need of conventional angiography
and its associated risks. Besides being faster and less expensive, it
is more widely available, is more sensitive for mural calcium, can display
bony landmarks, and can also be used in patients with aneurysm clips and
other MR incompatible hardware. The only limitations of CT angiography
are use of intravenous contrast and radiation exposure. CT angiography
closely simulates catheter angiography as it depicts the volume of
contrast opacified vessels unlike MR angiography and Colour Doppler ultrasound,
which are highly dependent on velocity of blood fiow.
However catheter angiography provides better spatial and temporal resolution
in comparison to CT angiography. With the advent of multislice technology
and ongoing improvements in X-ray tube design, the potential of CT angiography
will be further expanded in terms of greater coverage and higher resolution. |
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REFERENCES
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WHO
GUIDELINES FOR DETECTING SARS NEED TO BE RECONSIDERED
The WHO guidelines for diagnosing SARS have an 83% accuracy in
detecting suspected cases. In an observational study of 556 people
screened for SARS in Hong Kong, Rainer and colleagues found that
the best predictor of SARS was radiological evidence of pneumonic
change, which often preceded the onset of fever. The main discriminatory
symptoms in the early stages of the disease were fever, chills,
malaise, myalgia, and rigor - not respiratory tract symptoms,
as stated in the WHO guidelines. The guidelines had a specificity
of 95% and a sensitivity of 26% for detecting SARS.
BMJ, 2003; 326 : 1354. |
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