Cerebral hyperperfusion syndrome remains under-recognized

Abstract

We read with interest the report by Kearny et al. [1] entitled ‘‘Autoimmune encephalopathy presenting as a ‘posterior circulation stroke’’. Herein, the authors present a 73-year-old woman with acute onset of aphasia and right arm weakness with a normal CT of the brain 12 h after admission. Diffusion-weighted magnetic resonance imaging (DW MRI) 2 days later showed increased signal in the left hippocampus, amygdala, and the pulvinar region of the thalamus. Symptoms improved over 1 month. The patient received a diagnosis of ‘posterior circulation stroke’ but this was subsequently changed to ‘autoimmune encephalitis’ when she developed steroid-responsive encephalopathy and seizures 1.5 months later. Having identified high voltage-gated potassium channel antibody (VGKC abs) levels, the authors concluded that this was the first reported case of VGKC abs-positive limbic encephalitis with a stroke-like onset. Whereas we have no doubt that the patient indeed fulfilled the diagnostic criteria for VGKC abs-associated encephalitis in the later stage, we also believe that her initial history rather suggests a different diagnosis. First, the DW MRI changes in the mesial temporal lobe cannot explain the aphasia and right arm weakness. These deficits are compatible with a middle artery, not a posterior circulation, syndrome. Second, the authors state that the patient developed aphasia and right arm weakness 5 days after endarterectomy for a high-degree left carotid artery stenosis. Although no further clinical details are provided, this presentation and the lack of relevant findings on the CT and DW MRI are highly suggestive of cerebral hyperperfusion syndrome (CHS). CHS is a rare but well-described entity in patients after carotid endarterectomy or carotid angioplasty with stenting. Patients may present with headache (often ipsilateral to the site of intervention), confusion, and decreased consciousness, as well as focal neurological deficits and seizures corresponding to the vascular territory of the recanalized artery. CHS can be monosymptomatic and short-lived or, if associated with complications such as intracerebral hemorrhage, fatal [2, 3]. Whereas carotid angioplasty with stenting is associated with development of CHS within a few hours, CHS following carotid endarterectomy typically peaks around the sixth postoperative day as in the present patient [3]. Elevated systemic blood pressure, impairment of cerebral autoregulation, and disruption of the blood–brain barrier are believed to provoke reperfusion injury [2, 4]. As reported in another recent issue of the Journal of Neurology, CT (and MRI) brain perfusion shows elevated regional tissue perfusion and thereby assists in differentiating CHS from postoperative transitory cerebral ischemia [5]. CHS is best prevented by firm periand postprocedural blood pressure control. Treatment apart from lowering of blood pressure is mainly supportive according to standard neurointensive care protocols including, if necessary, lowering the intracranial pressure, evacuating intracranial hematoma, and providing antiepileptic drugs [2, 3]. However, awareness of CHS is the key to diagnosis and treatment. We therefore provide this commentary in order to stress the point that CHS remains under-recognized.