You are working one evening when EMS brings in a "Code Stroke" patient. He is a 60-something year old male who has aphasia and confusion. His wife arrives and states that the symptoms began following an episode of whole body shaking associated with loss of consciousness. Further history reveals that the patient had a left sided carotid endarterectomy 5 days ago. The patient's systolic blood pressure is 220. An emergent head CT is obtained.
What is your diagnosis? What is your further workup and management?
Scroll down for the case conclusion.
Final diagnosis: Cerebral Hyperperfusion syndrome
Case Conclusion: The head CT shows a left frontal SAH. The patient’s blood pressure was unresponsive to labetolol, so he was started on a nicardipine drip for blood pressure control and admitted to the ICU. He had a cerebral angiogram performed which demonstrated enlargement of the patient’s left ACA, MCA and PCA suggesting loss of autoregulation in these regions due to patient’s prior chronic occlusion. His symptoms improved and he was discharged to home on a regimen of labetolol and clonidine for blood pressure control.
Learning Points: Carotid hyperperfusion is a clinical syndrome with a wide variability of clinical presentations ranging in severity from unilateral headache to seizures to intracranial hemorrhage . It occurs following reconstitution of carotid blood flow, either with carotid endartectomy (CEA) or carotid artery stenting. It is a rare though serious complication, occurring in 1-7% of post CEA patients with a 0.4 – 0.79 % incidence of intracranial hemorrhage.
The underlying pathophysiology of cerebral hyperperfusion syndrome is a compromise of cerebral autoregulation. In healthy individuals, cerebral blood flow remains constant as long as systemic blood pressure remains between 70 and 150 mmHg . Cerebral blood flow is the byproduct determined by the cerebral perfusion pressure (CPP) divided by cerebral vascular resistance (CVR):
CBF = CPP/CVR
CPP is equal to the Mean arterial pressure- intracranial pressure and thus can increase in the face of increased blood pressure or decrease with increased intracranial pressure. When CPP increases, vasoconstriction of the small arteries or arterioles increases CVR to maintain constant CBF. The myogenic response of the carotids is regulated by the stretch reflex, where increases in arterial pressure cause contraction of smooth muscle and decrease blood flow. Chronic hypertension shifts both the lower and upper limits of autoregulation to higher levels, thus increasing the chance of hypoperfusion with a rapid decrease in blood pressure.
In addition vasconstriction due to increases in CPP, the cerebral vasculature constricts in response to hypocapnia, increased oxygen carrying capacity, and decreased metabolic demand of brain cells.
In patients with carotid artery stenosis, however, chronic ischemic conditions compromise the reactivity of the cerebral vasculature . Much like overstretching an elastic piece of clothing, chronic maximal dilation of the arterioles to maintain cerebral blood flow eventually damages the smooth muscle cells so that they are less able to constrict effectively and increases membrane permeablity. Thus, when normal blood flow is reconstituted, patients can develop cerebral edema and even hemorrhage, leading to the clinical presentation of headache, seizure, and focal neurologic deficits.
In patients with cerebral hyperperfusion syndrome, blood flow is pressure-dependent. Therefore, the treatment centers around tight blood pressure control, with a goal SBP of < 120-140 mmHg . As far as which agents to use, agents that decrease blood pressure by vasodilation (calcium-channel blockers, nitrates) should theoretically be avoid as they can actually increase cerebral blood flow. Labetolol has both beta-antagonistic and alpha-antagonistic properties, decreases cerebral blood flow and is recommended as first-line therapy. In general, patients have aggressive blood pressure treatment for at least 6 months, at which point cerebral autoregulation is usually restored.
Case Conclusion by Maia Dorsett (@maiadorsett)
1. Lieb, M., Shah, U., & Hines, G. L. (2012). Cerebral hyperperfusion syndrome after carotid intervention: a review. Cardiology in review, 20(2), 84-89.
2. Powers, W. “Autoregulation and Hemodynamics in Human Cerebrovascular Disease.” Cerebral Revascularization, 1, 3-18.