Today, I review, link to, and excerpt from StatPearls‘ Posterior Reversible Encephalopathy Syndrome. Jaime E. Zelaya; Lama Al-Khoury. Last Update: October 11, 2024.
All that follows is from the above resource.
Posterior reversible encephalopathy syndrome (PRES) is a neurologic disorder that can present with multiple different symptoms such as visual disturbances, seizures, headaches, and altered mentation. It is classically diagnosed based on its imaging characteristics on MRI imaging of the brain that is most commonly seen in the parieto-occipital lobes. To avoid potential pitfalls of this treatable condition, prompt recognition and diagnosis are paramount in improving patient outcomes.
It can present with a variety of symptoms such as altered mentation or stupor, drowsiness, visual disturbances (e.g., visual hallucinations, cortical blindness, hemianopia, quadrantanopia, and diplopia), seizures (focal or general tonic-clonic), and headaches.[1] PRES can present acutely or subacutely, with symptoms developing within hours to days. Often, the presentation occurs in the context of acute uncontrolled hypertension, with systolic blood pressures ranging between 160 to 190 mmHg.[2] The name is designated to its clinical and radiographic syndrome that is inspired by (1) radiographic findings of white matter edema (i.e., hyperintense T2 signal or hypointense T1 signal on magnetic resonance imaging (MRI)), typically found in the posterior cerebrum in a symmetric fashion (although asymmetric presentations are possible); and (2) the fact that symptoms are reversible, provided that the syndrome is recognized and treated promptly. However, the name used to describe the syndrome can be misleading as the edema is not always localized necessarily to the posterior cerebral white matter as it can occur in watershed zones other than parietal-occipital regions thalamus, and sometimes in the anterior circulation.[2][3][4] Moreover, the syndrome is not always reversible. Some individuals can develop life-threatening complications, such as transforaminal cerebellar herniation and focal neurologic deficits, especially if prompt treatment is not initiated.[5][3]
History and Physical
PRES is a clinical and radiographic diagnosis and performing a thorough history and physical examination is indispensable. There are multiple different clinical presentations that can vary in severity and acuity. The most common presenting symptoms include headache (50%), encephalopathy (28%), visual disturbances like binocular diplopia, vision loss, no light perception vision, hemianopia, or quadrantanopia(39%), seizures (80%), and focal neurological deficits (10-15%).[27] Sometimes the affected individual may have changes in mental status and not provide a reliable history; therefore, obtaining collateral information from relatives, friends, or acquaintances is valuable. While only a few patients will be normotensive, up to 75% will have moderately to severely elevated blood pressure on initial presentation.[18] Some theorize that it is not the height of the blood pressure but the rapidity of the elevation, similar to the theory with febrile seizures in children, not the height of the fever, but the rapidity of its elevation. When conducting a physical examination, attention to the following should be noted: hemianopia, quadrantanopia, visual neglect, cortical blindness, horizontal gaze palsy with intact vestibulo-ocular reflex, papilledema, oral trauma (tongue biting seen during a seizure), brisk reflexes, active convulsions, and urinary and fecal incontinence.[28][29]
Evaluation
Imaging remains essential and the gold standard in the diagnosis of PRES as it cannot be made based on clinical symptoms alone.[30] A head CT is critical to assess for neurologic emergencies that can explain an acute onset of altered mentation, headache, and seizures, such as intracranial hemorrhage. An MRI of the brain without intravenous (IV) contrast is the imaging modality of choice, looking for the presence of vasogenic edema that will appear as a hyperintense signal on T2 with the fluid-attenuated inversion recovery (FLAIR) sequences helping to improve sensitivity. This is most commonly seen in the parieto-occipital lobes—although other areas can be involved, such as the temporal lobe, frontal lobe (superior frontal gyrus), cerebellum, brainstem, and deep white matter.[4] The cortex is theorized to be more involved than white matter and is more densely packed and able to resist the accumulation of edema. The MRI will also help in the evaluation of other potential diagnoses, such as hypoxic-ischemic encephalopathy, posterior circulation infarct, and primary central nervous system vasculitis.[2] When the classic posterior cerebral hemispheres are involved, what differentiates it from an infarction of the posterior cerebral artery infarction, is the sparing of the calcarine and paramedian parts of the occipital lobe. Similarly, the use of diffusion-weighted imaging (DWI) can aid in the differentiation of PRES from stroke and be either hypo- or isointense.
Vascular imaging with either a CTA or magnetic resonance angiography (MRA) of the brain, which is typically normal in PRES, can sometimes show focal vasoconstriction or vasodilation patterns present in CNS vasculitis; and magnetic resonance venography (MRV), which is also typically normal in PRES, can help exclude sagittal sinus thrombosis as a possible diagnosis.[31]
Part of the workup for PRES also includes the evaluation of potential etiologies since their identification will be crucial for management. Obtaining blood work can help evaluate electrolyte imbalances like uremia and hypomagnesemia, hypoalbuminemia, protein deficiency, and CSF studies for underlying infection (for example, herpes simplex virus type 1 or 2, which can cause herpes simplex encephalitis), and autoimmune etiologies. Blood work can also help exclude severe hypoglycemia as a potential diagnosis. A lumbar puncture is sometimes done in immunocompromised individuals or others with clinical suspicion of infection in order to assess for the presence of encephalitis.
Obtaining an electroencephalogram (EEG) in people with PRES can be helpful. For instance, if there is persistently altered mentation in the absence of tonic, clonic, or tonic-clonic movements, an individual may have subclinical seizure activity that can be captured on EEG. EEG patterns, however, are generally non-specific.[32]
Differential Diagnosis
The differential diagnosis of PRES is broad and includes the following:[2]
Prognosis
The prognosis of PRES is typically favorable if recognized and treated early, with symptom improvement or resolution in a few days to several weeks.[2][14] Visual symptoms often completely resolve, especially with early treatment of PRES, although there are some reported cases where residual visual deficits can remain (albeit improved) at 3 to 4 months after onset.[27] Although rare, it is unclear which individuals are at risk of having prolonged visual deficits and/or persistent seizures. PRES symptom irreversibility can ensue if treatment is delayed. If the amount of cerebral vasogenic edema is large, the prognosis can worsen, as the increased pressure to the surrounding blood vessels can compromise blood flow and result in ischemia.[16] In certain situations, if there is the involvement of the brainstem, the prognosis can also worsen.[16] Recurrence of PRES is possible and has been reported in individuals undergoing dialysis.[2]
Complications
Complications of PRES can develop if the disease is not treated promptly. Complications include focal neurologic deficits from ischemic injury, epilepsy, and life-threatening conditions, such as transforaminal cerebellar herniation, which is reported as one of the most common neurological complications that occur in children following hematopoietic stem cell transplantation.[5][38][5]
