Posterior Reversible Encephalopathy (PRES)

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22nd Nov 2017 Medical Reference this

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Posterior Reversible Encephalopathy (PRES): A Rare Presenting Feature of Pheochromocytoma

Abstract

Hypertension in young is mostly due to secondary causes and one of them is pheochromocytoma. These are catecholamine secreting enterochromaffin tumors causing paroxysmal hypertension. Adrenal pheochromocytoma presenting as posterior reversible encephalopathy syndrome (PRES) is very rare and has not been described in literature so far. Here, we report a case of previously healthy adolescent boy, who presented with acute onset severe headache, blurring of vision, generalized tonic clonic motor seizure and altered sensorium. His blood pressure was 234/126 mm Hg. The magnetic resonance imaging (MRI) of brain showed hyperintense signal on T2-weighted and fluid attenuated inversion recovery (FLAIR) images in bilateral parietal and occipital regions. High blood pressure and classical MRI findings were consistent with the diagnosis of PRES. Abdominal ultrasonography (USG) revealed a right adrenal mass. A diagnosis of pheochromocytoma was confirmed by abdominal triple phase contrast- computed tomography (CT) and 24-hour urinary metanephrine assay. After the blood pressure was stabilized with alpha and beta blockade, adrenal tumor was surgically excised. Histopathologic examination of tissue confirmed the diagnosis of pheochromocytoma. The MRI brain showed complete resolution of hyperintense signals (T2-weighted and FLAIR images) on two-months follow-up. He was symptom free at six months and one year follow-up.

Key words: Posterior reversible encephalopathy syndrome (PRES); Reversible posterior leukoencephalopathy (RPLE); Pheochromocytoma; Hypertensive Encephalopathy; Hypertension

Abbreviations: ADC: apparent diffusion coefficient; CT: computed tomography; MRI: magnetic resonance imaging; DWI: diffusion-weighted imaging; PRES: posterior reversible encephalopathy syndrome

Introduction

Hypertension in young is mostly due to secondary causes which include renal diseases (chronic renal failure, renal artery stenosis, polycystic kidney disease), coarctation of the aorta, systemic lupus erythematosus (SLE) and endocrinopathies. Pheochromocytomas are rare catecholamine secreting enterochromaffin tumors. The patients of pheochromocytoma usually present with spells of headache, sweating and palpitations due to excessive catecholamines. The cerebral manifestation of pheochromocytoma are uncommon. Posterior reversible encephalopathy syndrome (PRES) as a presenting feature of pheochromocytoma is rare.

Case Report

A 14-year-old previously healthy boy presented in emergency department with acute onset severe holocranial headache, blurring of vision, generalized tonic clonic motor seizure followed by altered sensorium. There was no previous history of nausea, vomiting, diarrhea, flushing, excessive sweating, migraine, autoimmune and connective tissue disorders, drug abuse, toxin exposure, hypertension or diabetes mellitus. He had no similar illness in past and family history was negative. His pulse rate and blood pressure were 130 beats per minute and 234/126 mm Hg, respectively. He was confused but followed simple commands. The pupillary size and light reaction were normal on both sides. Fundus examination showed bilateral papilledema. He was moving all the four limbs equally without asymmetry on painful stimulus. Plantars were bilaterally extensor. Signs of meningeal irritation (neck rigidity and Kernig’s signs) were negative.

Complete hemogram, serum electrolyte, renal function tests and other biochemistry including thyroid function tests were normal. Serum anti-nuclear antibodies (ANA), anti-double-stranded DNA antibody (anti-dsDNA) and ELISA test for human immunodeficiency virus (HIV) were negative. X-ray chest was normal. Electrocardiography (ECG) showed tachycardia. Magnetic resonance imaging (MRI) of brain showed hyperintense signal changes on T2-weighted and fluid attenuated inversion recovery (FLAIR) images in bilateral occipito-parietal regions. No restriction was seen on diffusion-weighted images (DWI) [Figure 1]. CT angiography of brain vessels was normal. High blood pressure and classical MRI findings were consistent with the diagnosis of PRES. On further evaluation, abdominal ultrasonography (USG) showed right adrenal mass. An abdominal triple phase contrast-enhanced CT scan revealed heterogeneous, contrast enhancing adrenal gland mass lesion measuring 32 x 26 mm suggestive of pheochromocytoma [Figure 2]. The diagnosis was confirmed by 24-hour urinary metanephrine assay. The plasma aldosterone concentration (PAC) and plasma renin activity (PRA) ratio (PAC/PRA) was 10.4. The 24- hour urinary normetanephrine was 31,572 µg/24 hour (normal: 63-402 µg/24 hour), urinary metanephrine was 1,524 µg/24 hour (normal: 32-167 µg/24 hour) and plasma noradrenaline level was 18,635 pg/mL (normal: 0-400 pg/mL).

Patient was managed intensively with nitroprusside infusion to reduce blood pressure. Injectable phenytoin was administered according to body weight to control seizures. Once patient was stabilized, he was started on oral alpha-blocker prazosin (20 mg/day) followed by beta-blocker propranolol (40 mg/day). After adequate alpha and beta blockade, patient was planned for surgery and resection of adrenal mass was done. Histopathologic examination confirmed the diagnosis of pheochromocytoma without invasion of the adrenal capsule [Figure-3]. The MRI brain showed complete resolution of hyperintense signals (T2-weighted and FLAIR images) and 24-hour urine metanephrines were normal on two-months follow-up. He was asymptomatic at six months and one year follow-up.

Discussion

Pheochromocytomas are neuroendocrine tumors arising from chromaffin cells of the adrenal medulla or extra-adrenal paraganglia. The classical features like holocranial headache, palpitations, hypertension, hyperhidrosis, hyperglycemia and hypermetabolism are due to excessive catecholamines production in these tumors. The cardiac complications such as arrhythmias, myocardial infarction and sudden deaths are associated with cardiotoxic effects of high blood catecholamines levels. Pheochromocytoma is a rare cause of secondary hypertension and accounts for 0.5% to 2.0% of all causes of hypertension in children. The neurological complications (ischemic or hemorrhagic stroke) are related to increased platelet aggregation, hypertension and vasospasm due to high catecholamines levels. The various potential triggers of pheochromocytoma crisis leading to hemodynamic instability are stress, blood loss, surgery and anesthesia. The diagnosis of pheochromocytoma is confirmed by 24-hour urinary metanephrine and normetanephrine levels.

Clinical features of reversible posterior leukoencephalopathy syndrome (PRES) are acute onset headaches, vision loss, seizures and altered sensorium. It is mostly due to hypertension, however other common causes are chronic renal disease, uremic encephalopathy, ergot alkaloids, steroids, chemotherapy, vasculitis and tumors. Pheochromocytoma is one of the rare cause of PRES due to secondary hypertension. However, to the best of our knowledge, acute, life-threatening initial presentation of pheochromocytoma as PRES has not been described in literature. Magnetic resonance images (MRI) of brain typically shows hyperintense signal changes on T2-weighted and fluid attenuated inversion recovery (FLAIR) images due to vasogenic edema. It mostly involves the cortical and subcortical white matter of the parietooccipital, frontal and temporal regions. Cerebral hemorrhage, cytotoxic edema and contrast enhancement are atypical imaging findings of PRES. The parietooccipital cortex and subcortical white matter were affected in our case. Classically, these signal abnormalities are reversible on antihypertensive therapy.

The pathophysiology of PRES is still poorly understood, however, various hypothesis have been proposed. Severe hypertension causes deranged autoregulation of sympathetically mediated cerebral arterioles. It leads to increased permeability in the blood-brain barrier and causes vasogenic edema. Sympathetic innervation of the vertebrobasilar system is not as extensive or as complete as that of the anterior circulation. Therefore, PRES predominantly affects parietooccipital cortex and subcortical white matter. Other possible mechanism may be endothelial dysfunction due to circulating toxins or chemotherapy agents. There may be cerebral infarction or hemorrhage due to compromise of the microcirculation by pressure from surrounding vasogenic edema. The exact etiology of the seizure remains unknown, but may result from effects of the pheochromocytoma on reducing seizure threshold via its actions on metabolic or hypertensive parameters. Our patient had high levels of circulating catecholamines, produced autonomously by tumor. Once vasogenic edema subsided with antihypertensive therapy, all the abnormal MRI findings vanished.

Clinical topography (acute onset headache, visual blurring, seizure and altered sensorium), high blood pressure and typical MRI findings suggested diagnosis of PRES. In our patient, other differential diagnosis such as thrombocytopenic thrombotic purpura (TTP), hemolytic uremic syndrome (HUS), encephalitis, systemic lupus erythematosus (SLE), brain mass lesions and drug toxicity were ruled out by appropriate clinical and laboratory investigations. In our patient, hypertension was detected for the first time on hospital admission and before that he never had any symptoms like headache, palpitations, perspiration or diarrhea. Our patient is of clinical interest as pheochromocytoma presented with life-threatening hypertensive encephalopathy. Management of pheochromocytoma requires aggressive approach including fluid resuscitation and antihypertensive therapy (both alpha and beta blockade) followed by surgical resection of tumor.

Conclusion

Pheochromocytomas are catecholamine secreting enterochromaffin tumors causing paroxysmal hypertension. Our patient is of clinical interest as an acute, life-threatening hypertensive encephalopathy (PRES) as a presenting feature of adrenal pheochromocytoma has not been described in literature so far. Pheochromocytoma should be ruled out in every young patient with acute hypertensive encephalopathy.

Figure Legends

Figure 1. Magnetic resonance imaging (MRI) of brain showing hyperintense signals on T2-weighted and fluid-attenuated inversion recovery (FLAIR) images in parieto-occipital region. No diffusion restriction is seen. [ T1-weighted axial (A), T2-weighted axial and sagittal (B,C), FLAIR (D), diffusion weighted (DWI) (E) and corresponding apparent diffusion coefficient (ADC) (F) images]. These abnormal signals completely vanished on follow-up MRI after six weeks.

Figure 2. Triple phase contrast-enhanced computed tomography (CT) of abdomen showing heterogenous enhancing mass lesion measuring 32 x 26 mm in right adrenal gland. [Axial CT: Arterial phase (A,B), Venous phase (C) and Delayed phase (D)].

Figure 3. Hematoxylin and eosin (H&E) stained microphotographs showing large pleomorphic nuclei, abundant basophilic cytoplasm and cell-nesting pattern (zellballen pattern). [H&E stain 40x view (A), 100x view (B,C)].

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