Posterior Reversible Encephalopathy Syndrome

What is Posterior Reversible Encephalopathy Syndrome?

A neurotoxic condition in which atypical brain imaging finding is a classic feature caused by multiple complex ailments including eclampsia (epileptic mother get seizure attacks during pregnancy and affects foetus), solid organ transplantation, allogeneic (genetically dissimilar) bone marrow transplantation, adverse effect of large dose chemotherapy inclusion, autoimmune diseases, and unique brain imaging pattern is termed as posterior reversible encephalopathy syndrome is clinically termed as Posterior Reversible Encephalopathy Syndrome (PRES). More precisely the diagnostic angiography analysis conducted in PRES has been demonstrated that PRES is a widespread reversible central nervous system disorder resultant of endothelial dysfunction^1,2,3.

Symptoms

All symptoms related to Posterior Reversible Encephalopathy Syndrome are not specific, as these may associate with other nervous system disorder. The symptoms are not chronic in nature, but acute or sub-acute type. The included symptoms are:

• Headaches
• Distorted mental condition
• Fatigue and somnolence and that may be progressed to bewilderment and coma.
• Convulsions, the nature of the seizure is status epilepticus
• Blurred vision
• Hemianopia (blindness half-field of vision)
• Visual neglect
• Hallucinations
• Cortical visual impairment.
• Imaging diagnosis provide following signs like papilloedema, hemorrhages and exudates to indicate neurotoxic condition
• Hypertension (increased blood pressure)

The severity of the symptoms is not same for every individual. For example, the visual impairment varies from man to man like some may experience only blurred vision, whereas some have cortical blindness. Status epilepticus is a more common convulsive seizure, but the seizure pattern may change as nonconvulsive status epilepticus.  Therefore, in Posterior Reversible Encephalopathy Syndrome, the symptomatic analysis is not sufficient to diagnosis, but imaging report obtain from MRI essentially provides a classic clinical presentation to diagnose the disease^2,3,4,5.

Pathology

The exact pathophysiology of the PRES is still unclear, But the majority of the experts believe severe hypertension interfere with the brain auto-regulation. Brain autoregulation assists in maintaining intracerebral pressure by regulating dilatation and constriction of cerebral vessels followed with adequate tissue perfusion. Uncontrolled hypertension 9above mean blood pressure 150 – 160 mmHg)increases tissue perfusion and simultaneously damages cerebral blood vessels. The consequences of this cause vasogenic edema due to interstitial extravasation of fluids and proteins. The condition becomes irreversible in the case of enhancement of mean arterial pressures above 200 mmHg.

Alternatively, some researchers also assume that systemic inflammatory condition is responsible for endothelial dysfunction. This concept is generated as eclampsia, sepsis, autoimmune disease and transplantation are associated with the systemic inflammatory condition. These pre-inflammatory conditions can interfere with brain autoregulation and the resultant of this onset of PRES^3,4,6.

Diagnosis

Computer Tomography (CT)

CT imaging is provided a quick evaluation. This imaging tool can exclude the possibility of the space-occupying lesions and cerebral hemorrhage, which can also provide a similar type of symptoms. Computer Tomography may also reveal arterial ischemia or thrombosis and venous sinus thrombosis, though the result is not considered purely reliable. The CT scan in PRES detection is not provided assured result, as sometime this imaging tool gives normal result even in presence of PRES.

Magnetic Resonance Imaging (MRI)

Classic MRI imaging tool can describe the abnormalities present in vascular areas of occipital and parietal lobes. The abnormalities affect white matter of the nervous tissue and found typical features like asymmetrical alterations, hemorrhage, an isolated association of the frontal lobe and cortical lesions. It is difficult to distinguish between PRES and other vascular conditions through standard MRI device. But using of specialized device and technique can useful to detect ischemia, edema, inflammation or subtle hemorrhage.

Both CT scan and MRI can detect venous sinus thrombosis. But the selection of diagnosis tool and process are very important in the detection of PRES. The consideration of kidney-related adverse effects provided by some contrast media is another vital point during conduction of diagnosis process. No nephrotoxic contrast is used in Magnetic resonance venography, therefore the negligible possibility of the onset of kidney-related adverse effects.

Angiography

It can detect vessel thrombosis, vasculitis, and dissection if associated with PRES.

Electroencephalography (EEG)

EEG is a standard diagnostic tool to recognize subclinical seizures and also provide the possible other causes, which can cause of encephalopathy.

Lumbar puncture

It can identify any infection or subarachnoid hemorrhage, but test result may be erratic and showed normal at the initial step of the disease or commencement of antibiotic therapy³.

Management

There is no specific medical intervention is available to treat PRES management. But it is expected that the quick management of causative factor can provide faster recovery and prevents related complications. The included management process are

• Hypertension management process
• Withdrawal of the triggering
• Antiepileptic drug incorporation for seizure treatment
• Anesthetic medication and ventilation is required to control generalized status epilepticus
• Corticosteroid drugs are used to treat vasogenic edema (though no practical implication behind this)^3,4.

Prognosis

The prognosis depends upon management plan, usually, an uncontrolled seizure can be manageable with anesthesia. Severe hypertension is controlled with an antihypertensive agent and peritoneal dialysis. The incorporation of these therapeutic managements usually provides rapid recovery of the patient. Anticonvulsive treatment incorporation also assists rapid recovery in case of uncomplicated PRES. Dialysis may recommend for repeated PRES incidence. Close monitoring of blood pressure is always important to get good prognosis in PRES^3,4.

References

1. W.S. Bartynskia; Posterior Reversible Encephalopathy Syndrome, Part 2: Controversies Surrounding Pathophysiology of Vasogenic Edema; Published online before print April 10, 2008, doi: 10.3174/ajnr.A0929AJNR June 2008 29: 1043-1049; Online available at http://www.ajnr.org/content/29/6/1043.full
2. Dr. Laurence Knott, Dr. Laurence Knott; (2016); Posterior Leukoencephalopathy Syndrome; Online available at http://patient.info/in/doctor/posterior-leukoencephalopathy-syndrome
3. Esther V. Hobson, Ian Craven, S. Catrin Blank; Posterior Reversible Encephalopathy Syndrome: A Truly Treatable Neurologic Illness; Perit Dial Int. 2012 Nov-Dec; 32(6): 590–594. doi: 10.3747/pdi.2012.00152; https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3524908/
4. Roth C, Ferbert A. The posterior reversible encephalopathy syndrome: what’s certain, what’s new? Pract Neurol 2011; 11:136–44
5. Kozak OS, Wijdicks EF, Manno EM, Miley JT, Rabinstein AA. Status epilepticus as initial manifestation of posterior reversible encephalopathy syndrome. Neurology 2007; 69:894–7
6. Bartynski W. Posterior reversible encephalopathy syndrome, part 2: controversies surrounding pathophysiology of vasogenic edema. AJNR Am J Neuroradiol 2008; 29:1043–9