Acute Ischemic stroke diagnosis [Neurosurgery Wiki]

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====== Acute Ischemic stroke diagnosis ======

=====  Computerized axial tomography (CAT) =====

==== Findings at various times after ischemic stroke ====

NB: These principles do not apply to small [[lacunar infarct]]s, nor to [[hemorrhagic stroke]]s (ICH). NB: CT
is normal in 8–69% of MCA strokes in the first 24 hours
((Moulin T, Cattin F, Crépin-Leblond T, et al. Early CT
Signs in Acute Middle Cerebral Artery Infarction:
Predictive Value for Subsequent Infarct Locations
and Outcome. Neurology. 1996; 47:366–375)).

▶ Hyperacute (< 6 hours after stroke). Early signs of [[infarction]] involving large areas of the [[Middle Cerebral Artery Territory]] 
correlate with poor outcome
((Marks MP, Holmgren EB, Fox AJ, et al. Evaluation of
early computed tomographic findings in acute
ischemic stroke. Stroke. 1999; 30:389–392)).

Early findings may include
((Tomandl BF, Klotz E, Handschu R, et al.
Comprehensive imaging of ischemic stroke with
multisection CT. Radiographics. 2003; 23:565–592)):

1. [[hyperdense artery sign]]: low sensitivity, but helpful if present

2. focal low attenuation within the gray matter*

3. loss of the gray-white interface*

4. attenuation of the lentiform nucleus

5. mass effect*

a) early: effacement of the cerebral sulci (often subtle)
((Wall SD, Brant-Zawadzki M, Jeffrey RB, et al. High
Frequency CT Findings Within 24 Hours After
Cerebral Infarction. AJR. 1982; 138:307–311))

b) late: midline shift in large territory infarction

6. loss of the insular ribbon sign (hypodensity involving the insular cortex, susceptible to ischemia
due to poor collaterals)

7. enhancement with IV contrast: occurs in only 33%. Stroke becomes isodense (called “masking”
effect) or hyperdense with normal brain, and, rarely, may be the only indication of infarction9
*These findings are probably due to increased water content resulting from the following: cellular
edema arising from altered cell permeability, which produces a shift of sodium and water from the
extracellular to the intracellular compartment, which also increases the extracellular osmotic pressure
causing transudation of water from capillaries into the interstitium
((Aarabi B, Long DM. Dynamics of Cerebral Edema. J
Neurosurg. 1979; 51:779–784)).

▶ 24 hrs. Most strokes can be identified as low density by this time.

▶ 1–2 wks. Strokes are sharply demarcated. In 5–10% there may be a short window (at around day
7–10) where the stroke becomes isodense, called “fogging effect.” IV contrast will usually demonstrate
these.

▶ 3 wks. Stroke approaches CSF density.

▶ Mass effect. Common between day 1 to 25. Then atrophy is usually seen by ≈ 5 wks (2 wks at the
earliest). Serial CT scans have shown that midline shift increases after ischemic stroke and reaches a
maximum 2–4 days after the insult.

▶ Calcifications. Over a long period of time (months to years) ≈ 1–2% of strokes calcify (in adults, it
is probably a much smaller fraction than this; and in peds it is higher).


==== CT ====
[[globus pallidus]](low density on CT):

===== CT perfusion =====

[[CT perfusion for acute Ischemic stroke diagnosis]].


===== Multiphase CT angiography in acute ischemic stroke =====
[[Multiphase CT angiography in acute ischemic stroke]].

===== Diffusion-weighted magnetic resonance imaging (DWI) ===== 

[[Diffusion-weighted magnetic resonance imaging for acute ischemic stroke diagnosis]].



==== Diffusion-weighted imaging in stimulated echo acquisition mode ====

Compared to standard [[EPI-DWI]], [[STEAM-DWI]] offers a more robust alternative for diagnosing [[subacute]] [[stroke]]s in areas affected by [[susceptibility artifact]]s
((Müller SJ, Khadhraoui E, Kube JMV, Langer P, Riedel CH, Voit D, Ernst M, Frahm J. Diagnostic value of diffusion-weighted [[STEAM]]-[[MRI]] in [[ischemic stroke]]. Eur J Radiol. 2021 Mar 26;139:109677. doi: 10.1016/j.ejrad.2021.109677. Epub ahead of print. PMID: 33813283.)).

see [[Diffusion-weighted imaging in stimulated echo acquisition mode]]

===== Arterial spin labeling =====

Determining the occlusion site and collateral blood flow is important in acute ischemic stroke. The purpose of the current study was to test whether arterial spin labeling (ASL) magnetic resonance imaging (MRI) could be used to identify the occlusion site and collateral perfusion, using digital subtraction angiography (DSA) as a gold standard.

Data from 521 consecutive patients who presented with acute ischemic stroke at our institution from January 2012 to September 2014 were retrospectively reviewed. Image data were included in this study if: (1) the patient presented symptoms of acute ischemic stroke; (2) MRI was performed within 24 h of symptom onset; and (3) DSA following MRI was performed (n = 32 patients). We defined proximal intra-arterial sign (IAS) on ASL as enlarged circular or linear bright hyperintense signal within the occluded artery and distal IAS as enlarged circular or linear bright hyperintense signals within arteries inside or surrounding the affected region. The presence or absence of the proximal IAS and distal IAS were assessed, along with their inter-rater agreement and consistency with the presence of occlusion site and collateral flow on DSA images.

The sensitivity and specificity for identifying occlusion site with ASL were 82.8 and 100%, respectively. Those for identifying collateral flow with ASL were 96.7 and 50%, respectively. The inter-rater reliability was excellent for proximal IAS (κ = 0.92; 95% CI 0.76-1.00) and substantial for distal IAS detection (κ = 0.78; 95% CI 0.38-1.00).

Proximal IAS and distal IAS on ASL imaging can provide important diagnostic clues for the detection of arterial occlusion sites and collateral perfusion in patients with acute ischemic stroke
((Morofuji Y, Horie N, Tateishi Y, Morikawa M, Yamaguchi S, Izumo T, Anda T,
Tsujino A, Matsuo T. Arterial Spin Labeling Magnetic Resonance Imaging Can
Identify the Occlusion Site and Collateral Perfusion in Patients with Acute
Ischemic Stroke: Comparison with Digital Subtraction Angiography. Cerebrovasc
Dis. 2019 Sep 25:1-7. doi: 10.1159/000503090. [Epub ahead of print] PubMed PMID: 
31553986.
)).

===== References =====