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Posterior Reversible Encephalopathy Syndrome: Study of Common Associations and Varying Imaging Features |
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Madhav Hegde, Naveen Raj MB 1. Associate Professor, Department of Radiology, Sambhram Institute of Medical Sciences and Research, Kolar, Karnataka, India. 2. Senior Resident, Department of Radiology, Subbaiah Institute of Medical Sciences, Purley, Shivamogga, Karnataka, India. |
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Correspondence Address : Dr. Madhav Hegde, D1003, The Gardens Apartment, No. 9 , KP Agrahara, Magadi Road, Bengaluru-560023, Karnataka, India. E-mail: docmadhavhegde@gmail.com |
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| ABSTRACT |  | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
: Introduction: Posterior Reversible Encephalopathy Synd-rome (PRES) is a clinically bewildering encephalopathy syndrome which can be encountered in emergency room or in an already hospitalised patient. Its occurrence and mechanisms have been widely published mainly in the population of patients with transplant necessitated immunosuppression and not many studies have been carried out in the setting of many other risk factors. Aim: To study the frequency of primary clinical conditions causing or associated with PRES in general radiology practice. To study the frequency and distribution of abnormal findings in specific regions of brain. Materials and Methods: Radiology database of a free-standing imaging center and a multi-specialty hospital was scrutinised for reports citing PRES, hypertensive encephalopathy, eclampsia, renal disorders or any state of neurotoxicity on brain imaging, between July 2011 and June 2015. Reports showing complete or partial PRES pattern on imaging during the clinical neurotoxic syndrome were included in the study. Results: Total 84 patients were identified with PRES, out of them 80 were adults (mean age- 40.48±13.03 years). Among them 56 were men, 24 were women. There were four children (mean age- 12±2.19 years; with renovascular hypertension due to Takayasu’s arteritis). Twenty patients were normotensive and four patients were positive for Human Immunodeficiency Virus (HIV). Conclusion: There are many causes and associations of PRES but all of them are ‘systemic’ in nature. Spectrum of these systemic diseases may vary in population/practice. Hypertension is not an absolute requirement for diagnosis of PRES though it is the strongest association. Non posterior (non parieto-occipital) locations being frequent it is advisable to drop ‘posterior’ component from its name. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Keywords : Eclampsia, Reversible leukoencephalopathy, Seizure | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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DOI and Others :
DOI: 10.7860/IJARS/2018/36527:2408
Date of Publishing: Jul 01, 2018 Financial OR OTHER COMPETING INTERESTS: None. |
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| INTRODUCTION |
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PRES is a clinically bewildering encephalopathy syndrome which can be encountered in emergency room or in an already hospitalised patient. Contrary to its name, it can leave behind irreversible brain damage during the course of recovery. However, its etio pathogenesis has not been completely established (1),(2),(3),(4),(5). Its occurrence and mechanisms have been widely published mainly in the population of patients with transplant necessitated immunosuppression and not many studies have been carried out in the setting of many other risk factors (2),(6).There is also limited data on the frequency of occurrence in various clinical risk factors and the pattern of regional distributions of lesions in brain parenchyma in various systemic associations responsible for PRES (7). | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Material and Methods |
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This retrospective study was conducted to identify clinical associations and regional brain parenchyma distribution of imaging findings of PRES in general population. Radiology database of Departments of Radiology of Medcorre Diagnostics and Trinity Hospital, Bengaluru, India, was scrutinised for reports citing PRES, hypertensive encephalopathy, eclampsia, renal disorders or any state of neurotoxicity on brain imaging, between July 2011 and June 2015. Reports showing complete or partial PRES pattern on imaging during the clinical neurotoxic syndrome were analysed. When more than one clinical association were present, the clinically dominant association was considered. Reports of patients with earlier radiologically established brain parenchymal changes like ischaemia, dural sinus thrombosis, and traumatic brain parenchymal injury on imaging and deranged coagulation profile were excluded from the study. However, one trauma patient with earlier normal baseline imaging on the day of trauma was also included in the study. Permission from local ethics committee was obtained and no written consent from the patients were obtained. Computed Tomography (CT) was obtained when clinical contexts demanded quick imaging diagnosis. Whenever clinical stabilisation was achieved, these patients were subjected to MRI evaluation. Eighteen patients had undergone CT and among eight of them CT was the only imaging modality carried out and the rest 10 underwent MR subsequently. MRI was performed at 1.5T (Interaand Achieva, Philips, Nether-lands). Although, parameters (TE, TR, flip angle) varied from patient to patient, they were in accordance with standard imaging practice. In all patients T1WI, T2WI, Fluid Attenuated Inversion Recovery (FLAIR), diffusion weighted MR imaging, gradient sequences were employed in transverse plane. In addition to these T2 sagittal, FLAIR coronal images were also obtained. Gadolinium (0.1 mmol/kg) based contrast study was carried out whenever required. Statistical analysis Analysis was done by SPSS Software Version 21.0. Unpaired Student’s t-test was used and p-value of <0.05 was considered to be statistically significant. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Results |
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Total 20 patients had abnormal signal intensities in infratentorial brain parenchyma and in four of them brainstem involvement was noticed while 16 had cerebellar involvement. Four patients had unilateral brain parenchymal abnormalities. Twelve patients had intracranial haemorrhage, which was subarachnoid in location and these patients were normotensives. None of these patients had intraparenchymal haemorrhage (Table/Fig 1). Among the 20 normotensives, 16 patients had renal disease and four patients had sepsis. Strongest association between the occurrence of PRES and systemic condition was essential hypertension. Twenty patients had renal disease and four patients each had sepsis, HIV, renovascular hypertension, pregnancy induced hypertension (Table/Fig 2). In four patients, foci of restricted diffusion were noticed. In 4 patients, signal intensity changes were not appreciated in T1W images. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Discussion |
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The epidemiology of PRES has not been established; however, it has been reported across the age of 4-90. It is predominantly reported in women (2). In our study, the mean age was 40.48±13.03 years and females accounted for 33.3% (pregnancy induced hypertension accounted for 4.8%) of the total study population, and this may be due to the nature of our practice which did not include obstetric care. However, earlier studies have revealed female preponderance even after excluding set of pregnancy induced hypertension (1),(8). There were four children (mean age 12± 2.19 years). We employed CT and /or MRI for neuroimaging (9). In our study, 4 HIV-positive patients who presented with clinical symptoms of headache and visual symptoms showed hyperintense (FLAIR) lesions in right cerebellar hemisphere, posterior aspect of bilateral temporal lobes, and bilateral parieto-occipital regions (10). In the holo hemispheric (Table/Fig 3) (a), watershed pattern, vasogenic oedema presents in a linear pattern. This linear edema is seen along the watershed or anastomotic border zone of anterior and posterior cerebral arteries and lateral hemispheric middle cerebral artery branches. In another patient with accelerated hypertension presented with predominant visual disturbances, we observed subtle superior frontal sulcus pattern (Table/Fig 3) (b). MRI also showed bilateral strong FLAIR hyperintensities in parieto-occipital region. CT findings (Table/Fig 3) (c,d), are often normal and nonspecific (2),(11). CT-scan is best suited for patients who are not either stable enough or not able to co-operate during longer MRI study. It lacks sensitivity in diagnosing PRES (12). MRI (particularly T2-FLAIR) is the preferred and correct choice of imaging technique for diagnosing PRES (2),(6),(14). Low intensity foci on T1W images were not demonstrated in only four patients, although bright signals were particularly well seen on FLAIR images. MR angiography may show patterns resembling vasculopathy (focal vasoconstriction/vasodilation and diffuse vasoconstriction) (14). Since, MR angiogram (Table/Fig 4) (a) was not a part of routine brain imaging protocol, in our study not all the patients were evaluated with the same. Twelve patients in our study had subarachnoid haemorrhage (Table/Fig 4) (b) which was mild and predominantly frontal in distribution and bilateral. None of the patients had intrapernchymal haemorrhage. Earlier study has noted increased incidence of parenhymal haematoma in patients with solid organ transplantations and immunosuppression (15). This corresponds well with the fact that none of our patients had any transplantation and subsequent immunosuppression therapy. In our study, most common pattern was of posterior occipito parietal pattern with 66.7% contribution (Table/Fig 1). This finding is consistent with the with recent study done in a pediatric population (16). Next common pattern was of superior frontal sulcus (38.1%), incidence of which was higher compared to earlier cited study. Temporal lobe lesion abnormality accounted for 14.3%. Parieto-occipital region was the most commonly involved region, followed by frontal lobe, temporal lobe and cerebellum (Table/Fig 4) (c), Involvement of frontal lobe, temporal lobe and cerebellum was relatively common. Isolated involvement of brainstem (Table/Fig 4) (d),(Table/Fig 5) (a), deep white matter, basal ganglia was infrequent. Khan SJ et al., did not observe any central variant of PRES (16). We derive that less common patterns like superior sulcus and central type are more common with adult risk factors than ones in pediatric population. Partial or asymmetric expressions of the primary patterns are also described in literature [17,18]. In our study, four patients with uncontrolled essential hypertension had unilateral occipital lesion owing to acute fluctuation of blood pressure. Four of the patients in our study had area of restricted diffusion (of size 10×12 mm) in unilateral occipital region, indicating irreversible cytotoxic oedema (19). In this study, we found classic clinical scenarios such as hypertension, renal disease, sepsis, and eclampsia (Table/Fig 2), to be associated with PRES (20),(21),(22),(23). Six of the patients who had subarachnoid haemorrhage (Table/Fig 5) (b), had renal parenchymal disease. Common clinical presentations were seizures, confusion, headache, visual disturbance. Imaging features of intra-cranial hypertension was not observed in any of our patients. Takayasu’s arteritis can be a cause of PRES (24). None of our patients had clinical features of spinal involvement. There was not a single case of transplant related immunomodulation or autoimmune connective tissue disease in the series. HIV was the only immune system related dominant scenario. Limitation In addition to intrinsic limitation of a retrospective study of limited data set, study was limited by coexisting risk factors and only dominant was considered. Pharmacological agents received during or prior to the diagnosis were not considered. Degree of severity of risk factor (e.g., systemic blood pressure measurements), general wellbeing during the illness were also ignored. Study is an early attempt to relate various systemic factors with type and locations PRES and this would help radiologist to suspect the systemic cause triggering PRES. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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