Case Report

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American Journal of Emergency Medicine

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American Journal of Emergency Medicine 33 (2015) 131.e5-131.e7

Hypertensive brain stem encephalopathy

Abstract

A 48-year-old man presented with headache and extreme hypertension. Computed tomography showed diffuse brain stem hypodensity. Magnetic resonance imaging revealed diffuse brain stem vasogenic edema. Hypertensive brain stem encephalopathy is an uncommon manifestation of hypertensive encephalopathy, which classically occurs at parietooccipital white matter. Because of its atypical location, the diagnosis can be challenging. Moreover, the coexistence of hypertension and brain stem edema could also direct clinicians toward a diagnosis of Ischemic infarction, leading to a completely contradictory treatment goal.

Hypertension remains one of the most common disease processes in patients presenting to emergency department. Hypertensive emergency refers to a spectrum of end-organ damage caused by Uncontrolled hypertension, in which hypertensive encephalopathy is included. On neuroimaging, posterior cerebral white matter edema, with or without accompanying gray matter involvement, is typically seen in most cases. We present a patient of hypertensive encepha- lopathy, with uncommon brain stem predominance.

A 48-year-old man, with history of hypertension, liver cirrhosis, and end-stage renal disease on regular hemodialysis, complained of headache and dizziness for 1 week. His Blood pressure surged up to 194/127 mm Hg on presentation despite long-term medication of valsartan. He denied vomiting, ataxia, or impaired visual acuity. A thorough physical examination failed to demonstrate focal neurologic deficit. Laboratory data showed unremarkable electrolyte profiles. Computed tomography (CT) (Fig. 1) revealed remarkable brain stem hypodensity, indicative of brain stem edema. Magnetic resonance imaging showed diffuse hyperintensities at midbrain, pons, and cerebral peduncles as well as superior and middle cerebellar peduncles on T2-weighted image (T2WI) (Fig. 2A) and T2-weighted fluid-attenuated inversion recovery images (Fig. 2B); however, the corresponding involved regions were isointense on both diffusion- weighted image (DWI) (Fig. 2C) and apparent diffusion coefficient (ADC) (Fig. 2D) maps. Based on clinical presentations and image findings, the brain stem edema is most likely to be vasogenic, and the diagnosis of hypertensive brain stem encephalopathy was made. The patient was hospitalized for the following 2 weeks for hypertension control. Magnetic resonance imaging after 1 month revealed gradual resolution of the Brain edema, accompanied with remission of headache. Hypertensive encephalopathy is thought to be caused by impaired Cerebrovascular autoregulation after an extreme hypertensive epi- sode. The symptoms of headache, consciousness impairment, seizure, visual abnormalities, nausea, or vomiting are typical of hypertensive encephalopathy in conjunction with presence of hypertension [1]; however, none of them are specific. When clinically in doubt,

neuroimaing may offer additional diagnostic clues. Typical imaging feature of hypertensive encephalopathy is parietooccipital white matter edema, which occurs in 98% of patients [2]. The term Posterior Reversible Encephalopathy Syndrome or reversible posterior leukoence- phalopathy syndrome has been adopted since various medical conditions all contribute to similar imaging characteristics of posterior cerebral parenchymal edema, including hypertension, eclampsia, uremia, and immunosuppressive therapy for organ transplantation [1,3].

In contrast, the diagnosis of hypertensive brain stem encephalop- athy remains challenging for emergency physicians, attributing to its atypical lesion location. As in this case, coexistence of Elevated blood pressure and brain stem edema on initial CT scan, instead of typical posterior cerebral white matter edema, may baffle clinicians toward other considerations such as brain stem ischemic infarction, leading to a completely contradictory hypertension treatment goal [4]. Confu- sion with brain stem glioma or brain stem encephalitis was also reported [5].

Fig. 1. Brain CT showed generalized hypodensity at brain stem.

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Fig. 2. T2-weighted spin echo image on axial view (A) and T2-weighted fluid-attenuated inversion recovery on sagittal view (B) showed hyperintensity at midbrain, pons, and cerebral peduncle as well as superior and middle cerebellar peduncles; however, the corresponding regions were isointense on both DWI (C) and ADC (D). The findings indicate that there is vasogenic edema of brain stem.

Although it is usually reversible if treated early, irreversible neurologic sequelae could occur if early recognition and adequate treatment cannot be achieved. It is important to perform a sophisticated neurologic examination when hypertensive brain stem encephalopathy is suspected. It was reported that patients of hypertensive brain stem encephalopathy have no associated focal neurologic deficits, a distinct clinical feature in dismissing ischemic brain stem infarction, as in our case [6]. On neuroimaging, the areas of edematous brain stem can be identified on T2WI; however, it is important to carefully examine the involved areas with following DWI and ADC maps because presence of cytotoxic edema is not a typical feature and should be ruled out. Despite prominent brain stem edema on T2WI, there should be minimal or no restricted water diffusion on DWI and ADC maps to rule out possibility of ischemic stroke with confidence.

The short-term goal for treating hypertensive emergency is to reduce the systolic BP by 10% to 15%, but no more than 25%, within the first hour, and to lower the BP down to 160/100 mm Hg within the first 6 hours. A too rapid correction in BP could aggravate cerebral perfusion and promote ischemia in clinical setting of an already vulnerable autoregulation. In addition, when choosing an appropriate antihypertensive drug, intravenous administration of a short-acting agent is recommended. Drugs of choice include labetolol, nicardipine, fenoldopam, or nitroprusside, based on availability and individualized considerations of the patient’s medical condition.

In summary, although hypertensive brain stem encephalopathy is a potentially reversible syndrome, permanent brain damage may still occur if Timely diagnosis and adequate treatment cannot be delivered. Patient’s clinical presentations may be nonspecific. In particular, resemblance of ischemic brain stem infarction in clinical symptoms

and images remains a major challenge to emergency physicians because hypertension treatment goals are different. A detailed Neurological examination, followed by brain imaging, may facilitate early recognition.

Pen-Yuan Liao, MD

Department of Emergency Medicine and Department of Medical Imaging

Taipei Medical university hospital, Taipei, Taiwan E-mail address: [email protected]

Chien-Chang Lee, MD, PhD

Department of Emergency Medicine, National Taiwan

University Hospital, Taipei, Taiwan E-mail address: [email protected]

Cheng-Yu Chen, MD

Department of Medical Imaging, Taipei Medical University Hospital

Taipei, Taiwan Imaging research center, Taipei Medical University, Taipei, Taiwan

Corresponding author

E-mail address: [email protected] http://dx.doi.org/10.1016/j.ajem.2014.06.032

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