Jin-Il CHUNG, M.D. Department of Radiology, Suncheon Pyunghwa Hospital,

1. Cerebral Hyperperfusion Syndrome Following Intracranial Revascularization: Anatomic and Pathophysiologic Considerations Jin-Il CHUNG, M.D. Department of Radiology, Suncheon Pyunghwa Hospital, Suncheon, Republic of Korea

2. Cerebral Hyperperfusion Syndrome (CHS) Rare, but not uncommon Potentially serious complication after cerebral revascularizations including carotid endarterectomy (CEA), carotid artery stenting (CAS), and intracranial angioplasty or stenting Hemorrhagic complications after cerebral revascularizations; uncommon, but can be fatal and devastating when it develops Pathophysiologic mechanisms of CHS; believed to occur following restoration of blood flow with impaired autoregulation (endothelial dysfunction mediated by free oxygen radicals) due to chronic hypoperfusion into brain tissues Symptoms of CHS; headache, hypertension, focal reversible neurologic deficits or focal seizures resulting from abruptly increased cerebral perfusion Introduction

3. Cerebral Hyperperfusion Syndrome (CHS) Management of CHS; requires immediate and aggressive blood pressure control to prevent possible intracerebral hemorrhages Imaging findings of CHS; vasogenic edema, small focal hemorrhages, and large size ICH Exact mechanisms of CHS; not been clearly elucidated, although some risk factors(diminished cerebrovascular reserve) might precipitate the complications Cerebrovascular venous structures; often revealed as less expanded appearances with chronic hypoperfusion Tentative mechanisms of CHS, which related with cerebrovascular venous anatomy Introduction

4. Intracranial Angioplasy; Left MCA M1 segment (F/65) Medically refractory, intracranial atherosclerotic stenosis IntracranialRevascularization of left MCA M1 segment with 1.5 mm PTCA (undersized) balloon with meticulous procedural cautions including 014 microguidewire (300 cm) exchange technique 3D Rotational Angiography (Innova 3100, GE Medical Systems) with 3D MPR before and after angioplasty Before Angioplasty After Angioplasty Case Reports

5. Intracranial Angioplasy; Left MCA M1 segment (F/65) Immediate CT Post 3 Days, Follow-up MRI Case Reports

6. Intracranial Angioplasy; Left MCA M1 segment (F/65) Before Angioplasty After Angioplasty Before Angioplasty After Angioplasty Case Reports

7. Intracranial Angioplasy; Left MCA M1 segment (F/65) Before Angioplasty After Angioplasty Case Reports

8. Intracranial Stenting; Basilar artery (M/56) Before Stenting Medically refractory, symptomatic high grade intracranial atherosclerotic stenosis IntracranialRevascularization of Basilar artery with 3.5 mm bare metallic coronary stent with meticulous procedural cautions including 014 microguidewire (300 cm) exchange technique 3D Rotational Angiography (Innova 3100, GE Medical Systems) with 3D MPR before and after stenting After Stenting Case Reports

9. Intracranial Stenting; Basilar artery (M/56) Immediate CT Post 3 Days, Follow-up MRI Case Reports

10. Intracranial Stenting; Basilar artery (M/56) Post 3 Days, Follow-up MRI FLAIR with DWI & ADC map image Case Reports

11. Intracranial Stenting; Basilar artery (M/56) Before Stenting anterior Median, anterior pontine vein Both Interpeduncular veins, drain upwardly and often called as pontomesencephalic veins Posterior or Communicating vein BVR(Basal vein of Rosenthal) Lateral mesencephalic vein (LMV) Transverse pontine vein (posterior group) Veins of posterior surface of pons Precentral vein After Stenting posterior Case Reports

12. Before Stenting Intracranial Stenting; Basilar artery (M/56) anterior Median, anterior pontine vein Both Interpeduncular veins, drain upwardly and often called as pontomesencephalic veins Posterior or Communicating vein Thalamogeniculate veins • Lateral mesencephalic vein (LMV) BVR(Basal vein of Rosenthal) Transverse pontine vein (posterior group) Veins of posterior surface of pons Precentral vein After Stenting posterior Case Reports

13. Intracranial Stenting; Basilar artery (M/56) Before Stenting After Stenting Case Reports

14. Intracranial Stenting; Basilar artery (M/56) Before Stenting After Stenting After Stenting Case Reports

15. Both Interpeduncular Vein Basal Vein of Rosenthal(BVR) Lateral Mesencephalic Vein Superior Petrosal Vein Precentral Vein Human Brain Stem Vessels, 2005, Henri M. Duvemoy General Arrangement of the Superficial Arteries and Veins of the Brain Stem, p.31 Case Reports

16. Cerebral Hyperperfusion Syndrome (CHS) Both patients were managed with the diagnosis of acute CHS Strict BP monitoring with a plan to maintain the systolic BP between 90-140mmHg Follow-up CT scan revealed resolution of edema and patients showed no residual neurologic deficits Results

17. Cerebral Hyperperfusion Syndrome (CHS) Diagnosis of CHS following intracranial revascularization (angioplasty and stenting) should be confirmed by imaging studies under the impression by neurologic examinations During revascularization procedures, can identify the secondary venous recruitments and redirected venous engorgements related with directly increased cerebral perfusions and blood flows Recruited and engorged venous structures, which were not delineated before the procedures due to longstanding hypoperfused brain parenchymal changes or chronic ischemia Probable pathophysiologic mechanisms of CHS; related with abruptly increased cerebral perfusion pressures of perfusion pressure break-through phenomenon of hypoperfused brain tissues Conclusion

18. Cerebral Hyperperfusion Syndrome (CHS) Therefore, secondary venous recruitments and engorgements could be explained as the potential venous reservoir preventing intracranial hypertensions, which always occurs after intracranial revascularizations Follow-up angiography exams should be compared with the immediate post-control revascularization angiography to verify the venous adaptations However, we can suggest that venous recruitments could be a one of favorable causative factors which might prevent the fatal hemorrhagic complications Conclusion