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KEY FACTS

Terminology
- Rare disorder most commonly occurring as complication of cerebral revascularization - Other etiologies less common - Status epilepticus - MELAS
- Major increase in ipsilateral cerebral blood flow (CBF) well above normal metabolic demands
Imaging
- Ipsilateral gyral swelling, sulcal effacement in post carotid endarterectomy (CEA) patient
- ↑ CBF, cerebral blood volume (CBV) on perfusion MR (pMR), perfusion CT (pCT)
- Early draining vein, capillary blush on DSA after revascularization
Top Differential Diagnoses
- Acute cerebral ischemia-infarction
- Status epilepticus
- MELAS
- Acute hypertensive encephalopathy, PRES
- Hypercapnia
Pathology
- Cerebral hyperperfusion syndrome (CHS) probably caused by maladaptive autoregulatory mechanisms, altered cerebral hemodynamics - "Normal perfusion pressure breakthrough" - Rapid restoration of normal perfusion following revascularization → hyperperfusion in previously underperfused brain
Clinical Issues
- ~ 3% of post-CEA patients develop CHS
- Triad of unilateral headache, neurologic deficit, seizures - Variable cognitive impairment - Ipsilateral face, eye pain
Diagnostic Checklist
- Need to distinguish stroke/TIA from CHS

TERMINOLOGY

Abbreviations
- Cerebral hyperperfusion syndrome (CHS)
Synonyms
- Post-CEA hyperperfusion
- Luxury perfusion
Definitions
- Rare (3.5%) disorder most commonly occurring as complication of cerebral revascularization - Mildly ↑ cerebral blood flow (CBF) common after carotid endarterectomy (CEA), typically asymptomatic - CHS defined as ≥ 100% increase in rCBF compared to preoperative values
- Major increase in ipsilateral CBF well above normal metabolic demands - Usually following carotid revascularization procedure - Carotid endarterectomy - Angioplasty with stenting - Thrombolysis - May occur in other settings [e.g., status epilepticus, mitochondrial encephalopathy lactic acidosis and stroke-like episodes (MELAS)] - After drainage of chronic subdural hematomas

IMAGING

General Features

Best diagnostic clue

- Ipsilateral gyral swelling, sulcal effacement in post-CEA patient
- ↑ CBF, cerebral blood volume (CBV) on perfusion MR (pMR), perfusion CT (pCT)

Size
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- Variable
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Morphology
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- Follows vascular distribution
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Angiographic Findings
- Sentinel signs suggestive of maximal arteriolar dilation, disrupted cerebral autoregulation - Early draining vein in treated ischemic territory - Early contrast filling vein(s) in late arterial or capillary phase - Prominent capillary blush (luxury perfusion) denser than rest of arterial territory - Persists late into venous phase

Imaging Recommendations

Best imaging tool
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- MR with DWI, PWI
- SPECT
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Protocol advice

- Add T2* (GRE or SWI) to look for hemorrhage

CT Findings

NECT

- Gyral swelling
- Cortical effacement
- Patchy or diffuse white matter (WM) edema
        - Posterior parietooccipital lobe most common
- ± hypodensity (may occur without attenuation alterations)
- Frank hemorrhage in < 1%

CECT

- Prominent vessels with ↑ intravascular enhancement
- May demonstrate contrast extravasation in severe cases (rare)

CT perfusion - Elevated CBF, ↓ TTP

MR Findings

T1WI

- Cortical swelling
- ± mild hypointensity
- Sulci effaced

T2WI
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- Gyral swelling, hyperintensity
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FLAIR

- Hyperintense cortex
- Hyperintensity in subarachnoid spaces on postcontrast FLAIR reported 2° to blood-brain barrier (BBB) disruption

T2* GRE

- Frank hemorrhage in < 1%
- Blooming on GRE or SWI

DWI

- Usually normal, as edema is vasogenic, not cytotoxic
- ~ 25% show small foci of restricted diffusion compared to preoperative DWI

PWI

- Elevated CBV, CBF
- Prolonged MTT
        - Side-to-side difference of 3 seconds predictive of CHS

T1WI C+

- May be normal
- May show slightly increased prominence of cerebral vessels
- Parenchymal enhancement in severe cases

MRA

- Preoperative ↓ signal intensity in middle cerebral artery (MCA) may identify patients at risk for CHS

Other Modality Findings
- SPECT - N-isopropyl-p-I-123-iodoamphetamine or I-123-iomazenil SPECT - Shows hyperperfusion in ipsilateral cerebral hemisphere after surgery - CBF ≥ 100% in revascularized territory from baseline - Can be detected even in asymptomatic patients - May be correlated with long-term neuronal damage that CT, MR do not detect - May be associated with crossed cerebellar diaschisis
Ultrasonographic Findings
- Transcranial color duplex (TCD) - 1.5-2x increase in MCA flow velocity

DIFFERENTIAL DIAGNOSIS

Acute Cerebral Ischemia-Infarction
- TTP/MTT prolonged (not decreased)
- Typically shows restriction on DWI (CHS often negative)
Status Epilepticus
- Metabolic hyperperfusion in affected brain
- History of seizure helpful but may not be available
Acute Hypertensive Encephalopathy, PRES
- Failed autoregulation → hyperperfusion → endothelial injury/vasogenic edema
- Predilection for posterior circulation
- Markedly elevated blood pressure (many etiologies) - Eclampsia, preeclampsia - Chemotherapy - Renal failure - Hemolytic uremic syndrome/thrombotic thrombocytopenic purpura - Drug abuse (especially cocaine)
MELAS
- Acute oxidative phosphorylation defect
- Stroke-like episodes related to vasogenic edema, hyperperfusion, neuronal damage
- Cortical hyperintensity, enhancement
- Perform MRS in unaffected region, look for lactate
Hypercapnia
- Carbon dioxide is potent stimulator of CBF
- Vasodilatory effect on cerebral vasculature

PATHOLOGY

General Features

Etiology

- Theories
        - Impaired cerebral autoregulation
        - Damage from free radicals
        - Baroreceptor reflex breakdown
        - Trigeminovascular reflex (vasoactive neuropeptide release)
- CHS probably caused by maladaptive autoregulatory mechanisms, altered cerebral hemodynamics
        - "Normal perfusion pressure breakthrough"
                  - Chronic ischemia → impaired autoregulation
                  - Loss of normal vasoconstriction
                  - "Resistance" vessels become chronically dilated
                  - Rapid restoration of normal perfusion following revascularization → hyperperfusion in previously underperfused brain
- Cognitive impairment after CEA or angioplasty/stenting may result from
        - Cerebral embolization during dissection, stenting
        - Global cerebral hypoperfusion during carotid cross-clamping
        - Cerebral hyperperfusion syndrome

CLINICAL ISSUES

Presentation
- Most common signs/symptoms
```
- Symptoms range from mild to severe/life-threatening
- Ipsilateral headache, neurologic deficit and seizures
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- Other signs/symptoms - Variable cognitive impairment - Face, eye pain
- Timing - Peaks at 12 h after carotid angioplasty/stenting (CAS) - 6 days after CEA - Can be delayed by up to 1 month

Demographics

Age

- For postendarterectomy CHS, generally older patients
- For other etiologies (e.g., seizure, MELAS), any age

Epidemiology

- ~ 3-4% of post-CEA patients develop mild CHS
        - Highest risk = impaired cerebrovascular reserve, asymptomatic stenosis
                  - > 100% increase in CBF after treatment
        - Contralateral stenosis, chronic hypertension do not influence risk of CHS after CEA
- Covariate clinical risk factors
        - Age
        - Hypertension (especially postoperative)
        - Diabetes
        - Bilateral lesions
        - Extent of ICA stenosis
                  - High grade > low grade
        - Presence of contralateral carotid occlusion or high-grade stenosis
        - Duration of cross-clamping
        - Diminished carotid reserve
        - Poor collateral blood flow
        - Decreased cerebrovascular reactivity to acetazolamide challenge

Natural History & Prognosis
- Neurologic emergency - If not treated promptly/adequately, can cause death or severe disability
- If no intracranial hemorrhage - Usually reversible - No major tissue destruction - May result in persistent mild cognitive impairment
- 1% of CHS with intracranial hemorrhage - Poor prognosis
Treatment
- Prevention - Minimize intraoperative cerebral ischemia - Consider continuing postoperative anesthesia/continuous sedation - Strict postoperative blood pressure control - Staged angioplasty in at-risk patients can ↓ - Efficacious for patients with severe impairment of hemodynamic reserve in I-123 IMP SPECT

DIAGNOSTIC CHECKLIST

Consider
- Post-CEA/carotid artery stenting patient with neurologic deficit - Need to distinguish stroke/transient ischemic attack from CHS

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References

Selected References

Images

Selected Images

A 56-year-old man with > 70% stenosis of his proximal left cervical internal carotid artery (ICA) underwent carotid endarterectomy. A few hours after surgery, he became acutely confused and developed right-sided weakness. Perfusion source image shows markedly increased vasculature in the left hemisphere .

CT perfusion obtained in the same patient appears relatively normal, but cerebral blood flow (CBF) on the left (2a, 2b ROIs) is increased compared to the right side.

TTP in the same patient is even more striking. The abnormal side is not the right middle cerebral artery (MCA) distribution (green) but is the left side (blue) where the TTP is markedly shortened.

Axial T2 MR in the same patient shows gyral swelling, sulcal effacement, and hyperintensity in the left temporal and parietooccipital cortex/subcortical white matter , basal ganglia . DWI (not shown) was normal. This is a classic example of postcarotid endarterectomy hyperperfusion syndrome.

Anteroposterior view of DSA shows abrupt occlusion of the left MCA just distal to its origin in a patient with a sudden onset of right-sided weakness and stroke-like symptoms. Little collateral filling of the distal MCA is seen.

After superselective catheterization of the left MCA and infusion of tissue plasminogen activator for 2 hours, normal circulation was restored, as shown on this AP DSA.

Following restoration of normal blood flow in the previously occluded left MCA, the patient experienced worsening right-sided weakness and throbbing headache. Axial MR perfusion study shows elevated (red area ), not decreased, CBF in the left temporal and parietal lobes.

Axial MR perfusion in the same patient shows elevated cerebral blood volume .

Axial T1 C+ FS MR shows cerebral hyperperfusion in status epilepticus in a 52-year-old woman with left-sided weakness following prolonged seizure. Note the increased intravascular, sulcal enhancement in the right temporal lobe compared to the left hemisphere .

pMR in the same patient shows increased CBF in the right temporal lobe , corresponding to the increased intravascular enhancement noted on previous image.

Additional Images

Axial NECT in a patient with confusion, right-sided weakness following left CEA shows subtle increased hypodensity in the cortex and subcortical WM of the left parieto-occipital lobes.

Axial FLAIR MR in the same patient shows hyperintensity in the cortex and basal ganglia .

Axial DWI MR in the same patient shows no evidence of restricted diffusion.

Axial T1 C+ FS MR in the same patient shows increased vascularity in the left parieto-occipital region.

Coronal T1 C+ FS MR in the same patient shows a faint capillary blush in the same area. This was cerebral hyperperfusion syndrome.

24 KiB Raw Blame History

KEY FACTS

Terminology

Imaging

Top Differential Diagnoses

Pathology

Clinical Issues

Diagnostic Checklist

TERMINOLOGY

Abbreviations

Synonyms

Definitions

IMAGING

General Features

Best diagnostic clue

Size

Morphology

Angiographic Findings

Imaging Recommendations

Best imaging tool

Protocol advice

CT Findings

NECT

CECT

MR Findings

T1WI

T2WI

FLAIR

T2* GRE

DWI

PWI

T1WI C+

MRA

Other Modality Findings

Ultrasonographic Findings

DIFFERENTIAL DIAGNOSIS

MELAS

Hypercapnia

PATHOLOGY

General Features

Etiology

CLINICAL ISSUES

Presentation

Most common signs/symptoms

Demographics

Age

Epidemiology

Natural History & Prognosis

Treatment

DIAGNOSTIC CHECKLIST

Consider

References

Selected References

Images

Selected Images

Additional Images

24 KiB

Raw Blame History