A 34-year-old woman came to the emergency department because of headaches and transient visual obscurations. The transient visual obscurations began 1 month before presentation and the headaches began 8 days previously. She had a history of untreated hypertension and migraine headaches. Visual acuity was 20/50 in the right eye and 20/400 in the left eye. A 1.2 log-unit left relative afferent pupillary defect was present. Visual fields to confrontation were full in the right eye and there was inferior constriction in the left eye. External and anterior segment examinations and intraocular pressures were normal in both eyes. There was bilateral optic disc edema with surrounding cotton wool spots as well as cotton wool spots, exudates, dot-and-blot, and flame hemorrhages in both maculae.
Neurologic examination was normal, but the patient's blood pressure was 238/172 mm Hg. Computed tomography of the brain without contrast showed diffuse cerebral edema with transtentorial and tonsillar herniation. Serum creatinine was 1.48 mg/dL (normal: 0.57–1.11 mg/dL) consistent with acute renal injury. In the presence of acute end-organ damage with retinopathy, nephropathy, and central nervous system involvement on neuroimaging, she was diagnosed with hypertensive emergency.
Initial magnetic resonance imaging (MRI) of the brain, performed without contrast, showed extensive T2 and fluid-attenuated inversion recovery (FLAIR) abnormalities and diffusion restriction throughout the white matter of both cerebral and cerebellar hemisphere and the pons. There also were findings of increased intracranial pressure with diffuse loss of sulcation, cerebellar tonsillar herniation to 11 mm below the foramen magnum, posterior flattening of the globes, and intraocular protrusion of the optic discs (Fig. 1). The differential diagnosis for this constellation of imaging findings included hypoxic–ischemic encephalopathy, atypical posterior reversible encephalopathy syndrome (PRES), metabolic derangement, toxic exposure, acute disseminated encephalomyelitis, or atypical demyelinating disease.
The patient was admitted to the neurocritical care service and underwent treatment for systemic hypertension and placement of an external ventricular drain. Intracranial pressure was not measured.
Evaluation of demyelinating and autoimmune disease was negative. Repeat MRI of the brain without contrast 6 days after presentation demonstrated marked improvement in the degree of white matter abnormalities both supra- and intratentorially, most consistent with PRES. On T2 imaging, there was increased signal in the intraorbital segment of the left optic nerve anterior to the optic canal (Fig. 2A). Diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) sequences map demonstrated restricted diffusion (Fig. 2B, C). These imaging findings were felt to be most consistent with an acute left posterior ischemic optic neuropathy.
After 3 weeks of treatment for hypertension, the patient's visual acuity was 20/20 in the right eye and 20/30 in the left eye. There was a left relative pupillary defect, but optic disc edema and hypertensive retinopathy were resolving. Two months after discharge, follow-up imaging showed complete resolution of the T2 and FLAIR white matter abnormalities and resolution of the T2 and DWI optic nerve abnormalities of the left optic nerves.
Sadda et al (1) summarized the clinical settings for the occurrence of posterior ischemic optic neuropathy to include:
- The perioperative period following a variety of surgical procedures felt to be secondary to anemia from excessive blood loss and associated hypovolemic hypotension
- Giant cell (temporal) arteritis causing inflammatory narrowing of the vasculature of the optic nerve, resulting in ischemic injury
- Non-arteritic atherosclerotic vascular disease secondary to the systemic risk factors of hypertension, diabetes mellitus, hypercholesterolemia, cardiac disease, and cerebrovascular disease.
In addition to these clinical settings, there also are reports of PION associated with use of sildenafil (2), and Wegener disease (3). The imaging findings in PION have been previously documented, and include restricted diffusion on DWI similar to our case (4–7). Neuroimaging abnormalities in patients with PRES are typically distributed in the parieto-occipital regions followed by the frontal lobes, inferior temporo-occipital junctions, and cerebellum. Atypical cases involve the deep white matter and brainstem and rarely demonstrate diffusion restriction or findings of elevated intracranial pressure. While our patient did have imaging findings atypical for PRES, her presentation, clinical course, and response to treatment were consistent with this diagnosis.
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