The role of perfusion CT in identifying stroke mimics in the emergency room: a case of status epilepticus presenting with perfusion CT alterations
© Guerrero et al; licensee Springer. 2012
Received: 7 November 2011
Accepted: 20 January 2012
Published: 20 January 2012
Emergency medicine physicians are often faced with the challenging task of differentiating true acute ischemic strokes from stroke mimics. We present a case that was initially diagnosed as acute stroke. However, perfusion CT and EEG eventually led to the final diagnosis of status epilepticus. This case further asserts the role of CT perfusion in the evaluation of patients with stroke mimics in the emergency room setting.
The differentiation between stroke and seizure can be a clinically arduous task for both emergency medicine physicians and neurologists [1, 2]. Patients with diseases that mimic stroke account for one-fifth of patients with brain attacks . Imaging may therefore be critical in making a diagnosis in the acute setting. Seizure is one condition that can mimic a stroke. Commonly, patients with Todd's paralysis or those with nonconvulsive status epilepticus can be clinically indistinct from those with acute stroke. Further complicating the clinical scenario, seizure may also be a presenting sign of stroke . Recently the time frame for standard treatment of acute stroke with IV tissue plasminogen activator was expanded from 3 h to 4.5 h from ictus onset . Although this extension of time is supported by the American Heart Association, it is not FDA approved and comes with a different set of relative contraindications. Intravenous thrombolytics are not without the risk of complications, including intracranial hemorrhage . Non-contrast CT (NCCT) of the head is the current gold standard in excluding intracranial hemorrhage prior to administration of intravenous thrombolysis. However, NCCT has a limited role in differentiating those patients with stroke from those with seizure. Although current guidelines advocate only NCCT as the imaging modality of choice in the initial evaluation of acute stroke, this case illustrates the importance of CT perfusion studies in the radiographic evaluation of brain attack patients in order to avoid misdiagnosis and inadvertent treatment of non-stroke patients with thrombolytic therapy. Furthermore, whereas hypoperfusion related to strokes has been widely investigated by CT-perfusion imaging [6, 7], this case demonstrates the hyperperfusion state often seen on perfusion CT in emergency room patients with epilepsy. We describe an interesting case of a patient presenting to the Shands Hospital at the University of Florida emergency room with a homonymous hemianopsia and alterations on perfusion CT related to hyperglycemia-induced occipital status epilepticus.
Stroke mimics account for 5-30% of "brain attacks." Of those patients receiving thrombolytic therapy in the European Cooperative Acute Stroke Study II (ECASS II), 17% were ultimately shown to not have had strokes . Common conditions such as migraine, epilepsy with and without Todd's paralysis, hypoglycemia, and sinus thrombosis can often mimic stroke [9, 10]. Unfortunately, NCCT is not a sensitive radiographic tool in detecting stroke because parenchymal changes do not usually appear early in the course of acute stroke [1, 11]. MRI would offer good accuracy and sensitivity in such cases . However, it is often not utilized because of its decreased availability in contrast to the short acquisition time and wide availability for NCCT in the emergency room setting.
There are data supporting the use of CT perfusion in acute stroke management . Relative MTT and absolute CBV are CT perfusion parameters that help define areas of infarct from areas of penumbra . Its use has also been investigated for the diagnosis of seizures [13, 14]. Hauf et al. demonstrated that perfusion CT is a useful tool in accelerating the diagnosis of nonconvulsive status epilepticus with a sensitivity of 78% . In this case, cortical hyperperfusion was observed as reflected by a decrease in mean transient time (MTT) and a concomitant increase in cerebral blood volume (CBV) and flow (CBF) (Figure 1). This is compatible with previous data demonstrating increased CBV and CBF values in the seizure onset zone as well as in the regions with ictal spread . This hyperperfusion state during the ictal state has also been shown with SPECT and f-MRI in patients with focal epilepsy [16, 17].
CT perfusion has the advantages of routine availability, short acquisition time, and quantitative results. This case further supports the role of CT perfusion in the emergency room setting when assessing stroke patients for thrombolytics. Although patients with stroke mimics infrequently receive thrombolytics and their treatment generally does not lead to harmful complications , CT perfusion may spare patients with status epilepticus from the misguided treatment of intravenous thrombolysis. PCT may also qualify as a complementary diagnostic tool in patients presenting to the emergency room with altered mental status in which stroke is also a consideration for etiology.
In summary, perfusion CT can serve an important role in differentiating acute stroke from an unusual presentation of status epilepticus in the emergency room setting.
Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
WG and HD are both fourth year Neurology residents at the University of Florida. SE is Associate Professor of Neurology, Clinical Director, Adult Neurology Comprehensive Epilepsy Program, and Medical Director, UF & Shands Epilepsy Monitoring Unit.
Publication of this article was funded in part by the University of Florida Open-Access Publishing Fund.
non-contrast CT head, MTT: mean transit time. CBV: cerebral blood volume, CBF: cerebral blood flow, SPECT: single-photon emission computed tomography, f-MRI: functional magnetic resonance imaging.
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