Astrocytoma mimicking the features of pheochromocytoma

Brainstem and Autonomic Nervous System Dysfunction: A Neurosurgical Point of View

Central autonomic control nuclei and pathways are mainly integrated within the brainstem, especially in the medulla oblongata. Lesions within these structures can lead to central dysautonomia.Central autonomic control structures can be damaged by tumors, during surgery, or by other neurosurgical pathologies. These may elicit clinical or subclinical autonomic complications that can constitute a serious clinical problem.The authors present a broad review of the central autonomic nervous system, its possible dysfunctions, and the relation between neurosurgery and this "not-well-known system". Preliminary results of an autonomic study of brainstem lesions that is currently being carried out by the authors are also shown.

Posterior fossa brain tumors and arterial hypertension

Hypertension caused by arterial compression of the rostral ventrolateral medulla is well described. Much less information is available on the association between neurogenic hypertension and posterior fossa brain tumors. To date, multiple reports have supported the impression that a small subpopulation of patients with posterior fossa tumors can present with arterial hypertension, and many of those patients achieved significant improvement of their hypertension after tumor resection and medullary decompression. To review the relationship between posterior fossa brain tumors and hypertension, we detail the history, basic science, and clinical reports along with an illustrative case regarding this topic.

A correlation of catecholamine and vasoactive Peptide release with hemodynamics in patients undergoing resection of arteriovenous malformations

INTRODUCTION

Control of blood pressure can be a problem for intracranial procedures. To investigate the relationship between hemodynamic variables and endogenous vasoactive substances, we studied patients undergoing resection of arteriovenous malformations (AVMs).

METHODS

This was a nonrandomized, prospective study of six patients who had resection of an intracranial AVM and six patients who had clipping of an intracranial aneurysm (ICA) that had not bled. Operative and postoperative blood pressure was controlled with sodium nitroprusside. Heart rate (HR), mean arterial pressure, pulmonary capillary wedge pressure, and cardiac index (CI) were measured after induction of anesthesia; before, during, and after hypotensive anesthesia; immediately postoperatively; and at 12, 24, and 36 hours postoperatively. Blood samples were drawn simultaneously in the AVM group to measure levels of norepinephrine, epinephrine, renin, aldosterone, vasopressin, angiotensin I, and angiotensin II and correlated with significant hemodynamic changes.

RESULTS

HR and CI increased significantly among patients with AVMs compared with patients with ICAs (p<0.001 and p=0.05, respectively). HR was significantly correlated with renin (r=0.60), norepinephrine (r=1.00), and vasopressin (r=0.66). CI was significantly correlated with epinephrine (r=1.00), renin (r=0.77), angiotensin II (r=0.71), and vasopressin (r=0.82). Patients with AVMs had a hyperdynamic state characterized by increases in HR and CI. These increases were accompanied by increased renin, norepinephrine, vasopressin, epinephrine, and angiotensin II serum concentrates.

CONCLUSIONS

There were no significant differences in blood pressure changes between patients who had resection for AVM and those who had clipping of ICA, probably due to the use of sodium nitroprusside in the AVM group. Patients with AVMs had a hyperdynamic state with increases in epinephrine, norepinephrine, angiotensin II, plasma renin activity, and vasopressin. Whether this hyperdynamic state is caused by the resection of the AVM or the use of sodium nitroprusside (SNP) cannot be concluded. Blockage of these mediators preoperatively may help control blood pressure without sodium nitroprusside.

Long-lasting improvement of arterial hypertension after surgical treatment of a foramen magnum meningioma: case report

BACKGROUND

Neurogenic arterial hypertension has been proposed to be caused by neurovascular compression in many cases. However, there is little reference to tumors causing hypertension by local compression of the vagal nerve or the ventrolateral medulla oblongata. The following case illustrates the effects of surgery for a meningioma of the foramen magnum on arterial hypertension.

CASE DESCRIPTION

A 54-year-old woman suffered from arterial hypertension for at least 7 months, for which she required a combined medical treatment regime. She suffered for 6 months from dizziness and tinnitus, more in the left ear than in the right. Neurologic examination revealed a horizontal fixation nystagmus and a mild left-sided hearing loss. Magnetic resonance imaging and computed tomographic angiography showed a contrast-enhancing tumor on the left side of the foramen magnum compressing the medulla oblongata close to the vertebral artery and vascularized by branches of the left PICA. Complete surgical extirpation was performed using a medial craniocervical approach. The tinnitus and dizziness were gone and hearing improved. Postoperatively, the arterial hypertension showed a long-lasting improvement (observation period 8 months) with only minimal medical treatment.

CONCLUSION

Based on our case, we conclude that tumors in close proximity to the ventrolateral medulla oblongata may induce neurogenic hypertension, similar to neurovascular compression.

The central autonomic network: functional organization, dysfunction, and perspective

The central autonomic network (CAN) is an integral component of an internal regulation system through which the brain controls visceromotor, neuroendocrine, pain, and behavioral responses essential for survival. It includes the insular cortex, amygdala, hypothalamus, periaqueductal gray matter, parabrachial complex, nucleus of the tractus solitarius, and ventrolateral medulla. Inputs to the CAN are multiple, including viscerosensory inputs relayed on the nucleus of the tractus solitarius and humoral inputs relayed through the circumventricular organs. The CAN controls preganglionic sympathetic and parasympathetic, neuroendocrine, respiratory, and sphincter motoneurons. The CAN is characterized by reciprocal interconnections, parallel organization, state-dependent activity, and neurochemical complexity. The insular cortex and amygdala mediate high-order autonomic control, and their involvement in seizures or stroke may produce severe cardiac arrhythmias and other autonomic manifestations. The paraventricular and other hypothalamic nuclei contain mixed neuronal populations that control specific subsets of preganglionic sympathetic and parasympathetic neurons. Hypothalamic autonomic disorders commonly produce hypothermia or hyperthermia. Hyperthermia and autonomic hyperactivity occur in patients with head trauma, hydrocephalus, neuroleptic malignant syndrome, and fatal familial insomnia. In the medulla, the nucleus of the tractus solitarius and ventrolateral medulla contain a network of respiratory, cardiovagal, and vasomotor neurons. Medullary autonomic disorders may cause orthostatic hypotension, paroxysmal hypertension, and sleep apnea. Neurologic catastrophes, such as subarachnoid hemorrhage, may produce cardiac arrhythmias, myocardial injury, hypertension, and pulmonary edema. Multiple system atrophy affects preganglionic autonomic, respiratory, and neuroendocrine outputs. The CAN may be critically involved in panic disorders, essential hypertension, obesity, and other medical conditions.

Transient and repetitive rises in blood pressure synchronized with plasma catecholamine increases after head injury. Report of two cases

The authors report two patients with repetitive episodes of acute transient rise in blood pressure synchronized with increases in plasma catecholamine after severe head injury. In both cases, the paroxysmal hypertension occurred suddenly on the 2nd day posttrauma, and its frequency declined gradually, disappearing with time. The pathophysiological basis of this peculiar clinical manifestation is discussed.

Autonomic hyperreflexia with spinal cord injury

Autonomic hyperreflexia occurs in up to 85 percent of individuals with spinal cord injuries above the major splanchnic sympathetic outflow. In such cases, paroxysmal reflex sympathetic activity develops in response to noxious stimuli below the level of the neurologic lesion. The clinical features of autonomic hyperreflexia are due largely to reflex sympathetic adrenergic and cholinergic discharges with dysfunctional supraspinal regulatory control. Cephalgia, diaphoresis, flushing, tachycardia or bradycardia, and paroxysmal hypertension are most commonly observed. Although a variety of stimuli can provoke autonomic responses of variable magnitudes, bladder and bowel distention continue to account for most episodes. Removal of the offending stimulus is important to restoring the autonomic nervous system to its baseline activity. Current understanding of the pathophysiology, clinical features, and medical management of this fascinating but potentially serious complication of spinal cord injury are reviewed.

Hypothalamic-midbrain dysregulation syndrome: hypertension, hyperthermia, hyperventilation, and decerebration

Certain decerebrate lesions of brain stem or hypothalamus induce pharmacologically reversible hypertension and hyperthermia in animals. We observed three young patients with episodic decerebration, hyperthermia, hypertension, and hyperventilation during recovery from comas of different etiologies. The shared pathology on neurologic examinations and computed tomographic scans was hypothalamic-mesencephalic dysfunction, suggesting a diencephalic-brain-stem disconnection syndrome or brain-stem release mechanism. Propranolol was the most effective drug tested, but only two patients responded, one dramatically. This novel clinical syndrome may have localizing and therapeutic significance in pediatric coma that needs to be further defined in future studies.

Evaluation and management of childhood hypertension

Hypertension in childhood is diagnosed according to age-adjusted values for each sex. It is more commonly diagnosed now than it was 2 decades ago because blood pressure is more frequently measured in children today. Surgically curable forms of hypertension are not common but usually present as moderate or severe hypertension (diastolic blood pressure greater than or equal to 110 mm Hg). Although many patients in this group are asymptomatic, some present with Bell's palsy, enlarged hearts, heart failure, encephalopathy, or stroke. Newer imaging techniques have proved particularly useful for localizing tumors, such as pheochromocytoma. Many antihypertensive drugs are now available, and therapy should be tailored to the patient's needs, with as few adverse or side effects as possible.

Cardiovascular regulation and lesions of the central nervous system

The central nervous system has an important role in the second-to-second regulation of cardiac activity and vasomotor tone. Central lesions that lead to a disturbance in autonomic activity tend to cause electrocardiographic and pathological evidence of myocardial damage, cardiac arrhythmias, and disturbances of arterial blood pressure regulation. To a great extent such cardiovascular disturbances result from alterations in sympathetic activity. Similar alterations in sympathetic activity can occur under conditions of emotional stress and precipitate cardiac arrhythmias that can themselves lead to the syndrome of sudden death. Experimental and clinical evidence suggests that central neural mechanisms may be involved in this important human syndrome, but no central lesion has yet been identified to account for it. Recent experimental evidence, derived from hypertension research, suggests that chemical disturbances in the central nervous system, without accompanying structural lesions, may be found to explain cardiovascular disturbances such as sudden death and hypertension.

Hypertension and neurofibromatosis. Case report

A 14-year-old girl with neurofibromatosis presented with severe hypertension. She was subsequently found to have a cerebellar glioblastoma multiforme and vascular lesions producing coarctation of the abdominal aorta and 50% and 95% stenosis of the left and right renal arteries respectively. No evidence of pheochromocytoma was found. After removal of the cerebellar tumor, marked amelioration of the hypertension suggested that the tumor had a major role in the pronounced elevation of her blood pressure. Patients who have both neurofibromatosis and hypertension should be carefully evaluated for these several potential lesions.

Pheochromocytoma: clinical manifestations and diagnostic tests

Pheochromocytoma accounts for about 0.1 per cent of patients with diastolic hyperstension. It mimics many diseases varying from anxiety psychoneurosis to intracranial tumors. Cardinal symptoms include sevre headache (72 to 92 per cent), sweating (60 tp 70 per cent), palpitations (51 to 73 per cent), and hypertension (> 90 per cent) of which 50 per cent is sustained, 50 per cent paroxysmal. Many drugs (phenothiazines, Saralasin, antiemetics, steroids, etc.) have been reported as precipitating factors. Patients who should be screened for pheochromocytoma include: (1) all symptomatic patients with sustained or paroxysmal hyperstension; (2) asymptomatic hypertension; (3) all patients with MEA 2a,b (hyperparathyroidism, medullary carcinoma of the thyroid, neurocutaneous lesions) and their first degree relatives, even if the latter are asymptomatic and normotensive; (4) hypertension plus diabetes mellitis or hypermetabolism; (5) hypertensive episode during induction of anesthesia or radiologic procedure; and (6) hypertensive response during histamine administration, i.e., gastric analysis. Urinary metanephrine is the single best screening test. Plasma catecholamine determination is particularly helpful when collected before and immediately after an attack. Provacative agents (histamine, glucagon, tyramine) are needed rarely. Preoperative localization of the tumor can be done with nephrotomography IVP, computerized axial tomography, ultrasound, 131-I-19-iodocholesterol scan, arteriography, venography.

The activity of the sympathetic nervous system following severe head injury

The activity of the sympathetic nervous system during the course of severe closed head injury has been evaluated in 15 patients by measuring plasma levels of epinephrine and norepinephrine. With the onset of the transition stage from midbrain syndrome to the apallic syndrome the plasma levels mainly of norepinephrine started to increase and remained high during the further course of the disease. During the remission from the apallic syndrome the elevated norepinephrine levels started to decline. The data indicate that a longlasting overactivity of the sympathetic nervous system is a characteristic feature in the course of severe head injury. As a rational therapy to protect the peripheral tissues against the consequences of a longlasting sympathetic overactivity we suggest the use of beta-adrenergic blocking agents and adrenergic neuron blocking drugs.

Increased urinary catecholamines in an infant with the diencephalic syndrome

In an infant of 15 months with the diencephalic syndrome, urinary excretion of norepinephrine was moderately raised and epinephrine greatly so. It is suggested that catecholamine secretion may be due to sympathetic stimulation at the level of the diencephalon, by a space-occupying lesion pressing on the thalamohypothalamic pathway. Some of the symptoms of the diencephalic syndrome such as euphoria, irritability, skin pallor, and hypertension may be the result of catecholamine secretion.

Phaeochromocytoma

Factors involved in the evaluation and care of patients with phaeochromocytoma have been discussed with respect to important considerations for the consulting or practising physician. Historical, physical, biochemical and other diagnostic procedures, as well as therapeutic manoeuvres have been adequately documented so that the clinician requiring additional information in depth may seek out the pertinent literature. Utilizing this manner of approach should significantly improve the care of patients with phaeochromocytoma in the hands of physicians who have not themselves had extensive experience with this disease. However, it must be emphasized that because of the potential gravity of this condition, if the physician feels insecure in the care of a patient or has further questions, he should not hesitate to seek expert advice which will benefit both the patient and himself.

Hypertension in acute neurological diseases of childhood

Five children are described who developed hypertension in relation to acute neurological disease. Possible pathophysiological mechanisms for the hypertension are considered. It is thought that the hypertension may have been related to interruption of the ascending tracts in the brain stem, leading to failure of integration between, or independent action of, the baroreceptors and osmoreceptor system. Management and treatment are discussed. Diazoxide (5 mg/kg bodyweight, given intravenously) appears to be the most effective drug for use in the acute episodes.