Sensitivity of modern computed tomography in detecting ... › sites › default › files ›...
1
Introduction The traditional diagnostic pathway for suspected non-traumatic subarachnoid haemorrhage (SAH) is unenhanced CT brain followed by lumbar puncture (LP) if scan negative. Requirement for lumbar puncture, with the current availability of modern multidetector CT, has been challenged in some studies. Aims • To determine sensitivity of modern CT brain (CTB) in detecting SAH in our hospital • To ascertain in negative CTB cases: reporting of CT limitations, rate of LP and use of further neuroimaging Methods • Retrospective January 2015 – July 2016 • Adult patients undergoing CTB with clinical query of acute non-traumatic SAH: time from onset of symptoms when available, scan result from verified report, if comment on limitation of CTB, whether LP performed, xanthochromia result and relevant further imaging results were recorded Results Total 343 CTB in 329 patients. Age range: 16-95 years Time Symptom onset to imaging timeframe: 0-42 days, median 2 days, (0-5 days in positive scans) Scan Result • 313 no acute finding (91.2%) • 15 positive - SAH (4.4%) • 15 positive - other pathology Figure 1. In 313 negative scans Lumbar puncture Successful lumbar puncture was carried out in 187 patients (60%) Xanthochromia result • negative 166/187 • high bilirubin only 6/187** • positive 1/187 (0.5%) (figure 4) • unhelpful/not done 14/187 (table 1) Table 1 Unhelpful xanthochromia result Not requested or not done on specimen 6 Too much oxyhaemoglobin to detect bilirubin and SAH not excluded 5 Insufficient or clotted specimen 2 Negative but at time frame (4 weeks) cannot exclude 1 Total 14 Further Imaging Of those with no LP (126) or unhelpful xanthochromia result (14), 21 and 5 patients respectively (18.5%) had some form of further relevant neuroimaging (table 2) with no occult SAH cases found. Reported Limitations Limitations of CT and/or recommendation for subsequent LP were mentioned in 145/313 cases (46%). No statistical correlation with LP uptake. Table 2 Further neuroimaging in patients with negative CTB and no LP or useful xanthochromia result MRI 11 CT-Angiogram (CT-A) 5 MRI and MR angiogram (MRA) 4 CT-A and MRI 2 CT-Venogram (CT-V) 1 CT-A, CT-V and MRI 1 CT-A, MRI and MRA 1 MR Venogram and CT-V 1 Total 26 **Isolated bilirubin rise would not normally be seen within the first week of SAH and there are other well known causes. 5/6 were accounted for by significantly high CSF protein or high serum bilirubin with 3 having negative MRI or CT-A while the 6th patient was known to be scanned within 1 day of symptoms. Sensitivity of modern computed tomography in detecting acute subarachnoid haemorrhage Dr Claire McArthur 1 , Dr Scott Blackwell 2 1. Dept Radiology, 2. Dept Biochemistry University Hospital Crosshouse, Kilmarnock, Ayrshire. KA2 0BE. Figure 2. True positive. 37 year old female presenting at least 5 days following sudden onset of headache with superimposed exacerbation and associated hypertension. CT shows right convexity SAH with corresponding FLAIR hyperintensity, Further drug history and neuroimaging work-up suggested a diagnosis of reversible cerebral vasoconstriction syndrome. Figure 3. True positive. 42 year old male with sudden onset headache. Time interval unrecorded. Subtle right sylvian fissure SAH and rounded hyperdensity in region of right PCOM with aneurysm demonstrated here on CT-A. *Figure 4. False negative. 71 year old man presenting 5 days following onset of thunderclap headache. Reported as no acute findings but positive xanthochromia and in retrospect subtle extra-axial hyperdensities bilaterally on CT. Subsequent MRI demonstrates some subtle FLAIR hyperintensity in a left parietal sulcus with several foci of subarachnoid hypointensity bilaterally on gradient echo images. No aetiology found for SAH on subsequent CT-A, MRI, MRA or DSA. Diagnostic Test Evaluation • Sensitivity of CTB for SAH in our cohort, encompassing the 15 positive cases and the 199 negative scans with either definitive xanthochromia result or further negative vascular imaging/ MRI, is 94% (CI 70-100%). • Specificity is 100% (CI 98-100%). • Negative predictive value is 99.5% (CI 97-100%). • If the initially false negative case with positive xanthochromia but positive imaging on review (and no aetiology of SAH found) is excluded, sensitivity is 100% (CI 78-100%). Figure 5. Summary Conclusion Modern CT is a highly sensitive tool for detecting SAH. Sensitivity was between 94-100% in our relatively small cohort with one false negative on initial reporting. In cases with negative CTB, LP uptake was 60% while a moderate number with no LP or xanthochromia result had further relevant negative imaging (18.5%).Limitations of CT was mentioned in 46%. The role of lumbar puncture in patients with suspected non-traumatic SAH remains in question. Negative Positive SAH Positive other 343 Scans 15 positive SAH 15 other pathology 313 negative CTB 187 lumbar puncture 126 no lumbar puncture 173 definitive xanthochromia result 14 no useful xanthochromia result 166 negative 6 high bilirubin only** 1 positive* (figure 4) 5 subsequent negative relevant neuroimaging 21 subsequent negative relevant neuroimaging 2 3 4
Transcript of Sensitivity of modern computed tomography in detecting ... › sites › default › files ›...
Introduction
The traditional diagnostic pathway for suspected non-traumatic subarachnoid haemorrhage (SAH) is unenhanced CT brain followed by lumbar puncture (LP) if scan negative. Requirement for lumbar puncture, with the current availability of modern multidetector CT, has been challenged in some studies.
Aims
• To determine sensitivity of modern CT brain (CTB) in detecting SAH in our hospital• To ascertain in negative CTB cases: reporting of CT limitations, rate of LP and use of further
neuroimaging
Methods
• Retrospective January 2015 – July 2016 • Adult patients undergoing CTB with clinical query of acute non-traumatic SAH: time from
onset of symptoms when available, scan result from verified report, if comment on limitation of CTB, whether LP performed, xanthochromia result and relevant further imaging results were recorded
Results
Total 343 CTB in 329 patients. Age range: 16-95 years
Time Symptom onset to imaging timeframe: 0-42 days, median 2 days, (0-5 days in positive scans)
Scan Result •313noacutefinding(91.2%)•15positive-SAH(4.4%)•15positive-otherpathology
Figure 1.
In 313 negative scans
Lumbar punctureSuccessfullumbarpuncturewascarriedoutin187patients(60%)
Xanthochromia result• negative 166/187• high bilirubin only 6/187** • positive 1/187(0.5%)(figure4)• unhelpful/not done 14/187 (table 1)
Table 1Unhelpful xanthochromia result
Not requested or not done on specimen 6Too much oxyhaemoglobin to detect bilirubin and SAH not excluded 5Insufficient or clotted specimen 2Negative but at time frame (4 weeks) cannot exclude 1Total 14
Further ImagingOf those with no LP (126) or unhelpful xanthochromia result (14), 21 and 5 patients respectively (18.5%)hadsomeformoffurtherrelevantneuroimaging(table2)withnooccultSAHcasesfound.
Reported LimitationsLimitations of CT and/or recommendation for subsequent LP were mentioned in 145/313 cases (46%).NostatisticalcorrelationwithLPuptake.
Table 2Further neuroimaging in patients with negative CTB and no LP or useful xanthochromia resultMRI 11CT-Angiogram (CT-A) 5MRI and MR angiogram (MRA) 4CT-A and MRI 2CT-Venogram (CT-V) 1CT-A, CT-V and MRI 1CT-A, MRI and MRA 1MR Venogram and CT-V 1Total 26
**Isolated bilirubin rise would not normally be seen within the first week of SAH and there are other well known causes. 5/6 were accounted for by significantly high CSF protein or high serum bilirubin with 3 having negative MRI or CT-A while the 6th patient was known to be scanned within 1 day of symptoms.
Sensitivity of modern computed tomography in detecting acute subarachnoid haemorrhage
Dr Claire McArthur1, Dr Scott Blackwell2 1. Dept Radiology, 2. Dept BiochemistryUniversity Hospital Crosshouse, Kilmarnock, Ayrshire. KA2 0BE.
Figure 2. True positive. 37 year old female presenting at least 5 days following sudden onset of headache with superimposed exacerbation and associated hypertension. CT shows right convexity SAH with corresponding FLAIR hyperintensity, Further drug history and neuroimaging work-up suggested a diagnosis of reversible cerebral vasoconstriction syndrome.
Figure 3. True positive. 42 year old male with sudden onset headache. Time interval unrecorded. Subtle right sylvian fissure SAH and rounded hyperdensity in region of right PCOM with aneurysm demonstrated here on CT-A.
*Figure 4. False negative. 71 year old man presenting 5 days following onset of thunderclap headache. Reported as no acute findings but positive xanthochromia and in retrospect subtle extra-axial hyperdensities bilaterally on CT. Subsequent MRI demonstrates some subtle FLAIR hyperintensity in a left parietal sulcus with several foci of subarachnoid hypointensity bilaterally on gradient echo images. No aetiology found for SAH on subsequent CT-A, MRI, MRA or DSA.
Diagnostic Test Evaluation
• Sensitivity of CTB for SAH in our cohort, encompassing the 15 positive cases and the 199 negative scans with either definitive xanthochromia result or further negative vascular imaging/MRI,is94%(CI70-100%).
• Specificityis100%(CI98-100%).• Negativepredictivevalueis99.5%(CI97-100%).• If the initially false negative case with positive xanthochromia but positive imaging on review
(andnoaetiologyofSAHfound)isexcluded,sensitivityis100%(CI78-100%).
Figure 5.Summary
Conclusion
ModernCTisahighlysensitivetoolfordetectingSAH.Sensitivitywasbetween94-100%inourrelatively small cohort with one false negative on initial reporting. In cases with negative CTB, LP uptakewas60%whileamoderatenumberwithnoLPorxanthochromiaresulthadfurtherrelevantnegativeimaging(18.5%).LimitationsofCTwasmentionedin46%.
The role of lumbar puncture in patients with suspected non-traumatic SAH remains in question.
Negative
Positive SAH
Positive other
343 Scans
15 positive SAH 15 other pathology313 negative CTB
187 lumbar puncture 126 no lumbar puncture
173definitive
xanthochromiaresult
14 no useful
xanthochromia result
166 negative
6high bilirubin
only** 1positive*(figure 4)
5subsequent negative
relevant neuroimaging
21subsequent negative
relevant neuroimaging
2
3
4
