Autonomic Dysfunction Secondary to Focal Central Nervous System Disease

The autonomic nervous system syndrome may also be classified anatomically into telencephalic, diencephalic, brain stem, and spinal cord disorders ( ...Ia.b.|p...2.1:5. ).

Telencephalon Syndromes. Temporolimbic seizures may induce changes in heart rate, heart rhythm, and blood pressure. Cardiovascular manifestations of seizures include sinus tachycardia or bradyarrhythmias (including sinus arrest) with syncope. Seizure-induced ventricular tachycardia and fibrillation have been implicated in sudden death. Other autonomic manifestations of seizures include flushing, pallor, shivering, sweating, symmetrical or unilateral piloerection, visceral sensations, vomiting (ictus emeticus), and respiratory changes.'^ , y Ischemic damage to the insula

TABLE 21-5 -- LEVEL-SPECIFIC CENTRAL AUTONOMIC NERVOUS SYSTEM DISORDERS

Telencephalon Diencephalon

Brain stem

Spinal cord

Stroke

Temporolimbic seizures

Wernicke's syndrome

Episodic hyperhidrosis with hypothermia

Paroxysmal autonomic hyperactivity

Fatal familial insomnia

Iatrogenic

Neuroleptic malignant syndrome Serotonin syndrome Tumors

Vertebrobasilar disease Synngobulhia

Arnold-Chian type I malformation

Inflammation (multiple sclerosis, poliomyelitis)

Trauma

Syringomyelia

Multiple sclerosis

Tetanus

Stiff-person syndrome

has been associated with cardiac arrhythmias and contralateral hyperhidrosis. When the cingulate and paracentral cortices are involved, urinary incontinence may occur because of uninhibited bladder contractions.

Diencephalon Syndromes. Disorders affecting the hypothalamus may produce disturbances of thermoregulation, osmotic balance, endocrine function, and state of alertness.^ Chronic expanding lesions such as tumors or granulomas cause hypothermia, whereas acute lesions may cause hypothermia or hyperthermia. Wernicke's encephalopathy should be suspected in alcoholic and other malnourished patients presenting with unexplained hypothermia, particularly in the presence of disturbances of consciousness and oculomotor function. [4 Episodic hyperhidrosis with hypothermia may occur with no apparent cause, y as a manifestation of agenesis of the corpus callosum,y or during paroxysms of autonomic hyperactivity.

Although such paroxysmal autonomic hyperactivity in patients with brain tumors and other diseases of the diencephalon has been referred to as diencephalic seizures, this term is a misnomer. The EeG shows no ictal activity, and the episodes are refractory to antiepileptic drugs. Paroxysmal autonomic hyperactivity was first described in patients with tumors situated in the region of the third ventricle that caused hydrocephalus and abrupt increases in intracranial pressure. The majority of cases, however, are due to severe closed head injuries marked by episodic increases in intracranial pressure and acute hydrocephalus following sub-arachnoid hemorrhage.^

Sympathetic hyperactivity also occurs in a transmissible spongiform encephalopathy characterized by severe atrophy of the anteroventral and dorsomedial nuclei of the thalamus. This autosomal dominant disorder presents with disruption of endocrine circadian rhythms, motor dysfunction, and progressive intractable insomnia--thus its name, familial fatal insomnia (see Chapter.43 ) [46]

Brain Stem Syndromes. Cerebrovascular disease is the most common cause of dysautonomia associated with brain stem dysfunction. Transient ischemic attacks in the basilar artery territory may present with paroxysmal hypertension before any focal neurological deficit becomes apparent. Lateral medullary infarction (Wallenberg's syndrome) produces Horner's syndrome and, occasionally, more severe autonomic abnormalities such as profound bradycardia, supine hypotension, or central hypoventilation.^

Other brain stem disorders associated with autonomic dysfunction include tumors, syringobulbia, Arnold-Chiari malformation type 1, multiple sclerosis, and poliomyelitis. Brain stem tumors may present with intractable vomiting, orthostatic hypotension, or paroxysmal hypertension. Syringobulbia may produce Horner's syndrome, orthostatic hypotension, cardiovagal dysfunction, lability of arterial pressure, and central hypoventilation. y Syncope, sleep apnea, and cardiorespiratory arrest have been reported in association with the Arnold-Chiari malformation type 1. Less common manifestation of brain stem dysfunction include hypertension due to involvement of the medullary reticular formation in poliomyelitis (see Chapter^.!); autonomic hyperactivity, most likely due to disinhibition of preganglionic sympathetic and parasympathetic neurons in tetanus (see Chapterii39 ); and fulminant neurogenic pulmonary edema due to demyelination of the area surrounding the NTS in patients with multiple sclerosis (see Chapter^ ).[4]

Spinal Cord Syndrome. Traumatic spinal cord injury, particularly injury above the T5 level, is associated with severe and disabling cardiovascular, gastrointestinal, bladder, and sexual dysfunction. These patients have both supine and orthostatic hypotension and are at risk of developing bradycardia and cardiac arrest during tracheal suction or other maneuvers that activate the vagovagal reflexes. Vasopressin and the renin-angiotensin-aldosterone system have an enhanced role in maintenance of orthostatic arterial pressure in patients with spinal cord lesions. Lack of vasomotor and sudomotor thermoregulatory responses below the level of the lesion may lead to severe hypothermia or hyperthermia in response to changes in environmental temperature. Acute spinal injury or spinal shock produces a paralytic atonic bladder. The pattern of dysfunction seen in the chronic stages of disease, however, depends on the level of the lesion. Lesions above the sacral parasympathetic nucleus produce spastic bladder, commonly with detrusor-sphincter dyssynergia, whereas lesions of the conus medullaris produce a flaccid, areflexic bladder.

In patients with chronic tetraplegia with lesions at or above the T5 level, stimulation of the skin, muscle, or viscera innervated by segments below the lesion may result in a massive reflex activation of sympathetic and sacral parasympathetic outflows, referred to as autonomic dysreflexia. y Stimuli that trigger autonomic dysreflexia arise primarily from the bladder, bowel, or skin. Vasodilation above the level of the lesion produces flushing of the face, chest, and upper arms and congestion of the nasopharyngeal mucosa. There may be excessive sweating above the anesthetic dermatome, piloerection, pallor in the abdomen and lower extremities, and pupillary dilatation. Severe hypertension is a prominent feature of autonomic dysreflexia and can result in hypertensive encephalopathy or intracranial, subarachnoid, or retinal hemorrhage. The combined parasympathetic and sympathetic stimulation may cause potentially dangerous supraventricular and ventricular arrhythmias.

Multiple sclerosis (MS) may affect autonomic pathways at the level of the spinal cord, brain stem, or diencephalon. Bladder, bowel, and sexual dysfunction are prominent autonomic manifestations of MS. The pathophysiological basis of the bladder dysfunction seen in patients with MS is detrusor hyperreflexia and detrusor-sphincter dyssynergy. Subclinical abnormalities in cardiovascular sympathetic and parasympathetic function and abnormal thermoregulatory sweating detected by testing in the autonomic laboratory are common in patients with MS.

Syringomyelia produces partial interruption of sympathetic output pathways in the intermediolateral cell columns. Its autonomic manifestations include Horner's syndrome, sudomotor and vasomotor dysfunction, and trophic changes in the limbs, especially the hands.

Tetanus and the stiff-person syndrome may be associated with sympathetic hyperactivity due to lack of synaptic inhibition of preganglionic autonomic neurons. This results in hyperpyrexia, sweating, tachycardia, hypertension, tachypnea, and pupillary dilatation, usually associated with the muscle spasms.

_TABLE 21-6 -- TOPOGRAPHIC OR ORGAN RESTRICTED AUTONOMIC DISORDERS

Disorders of the Pupil Affecting parasympathetic outflow Third nerve lesion Argyll Robertson pupil Adie's pupil

Affecting sympathetic outfiow Horner's syndrome Pourfour du Petit syndrome Facial Hyperhidrosis and Flushing Gustatory sweating Harlequin syndrome Cluster headache

Vasomotor and Sudomotor Disorders of the Limb

Vasomotor disorders

Raynaud's phenomenon

Acrocyanosis

Livedo reticulans

Erythromelalgia

Essential hyperhidrosis

Complex neuropathic pain syndromes

Painful distal peripheral neuropathy

Nerve trauma (causalgia)

Undetermined and multifactorial: Complex regional pain syndrome Refex sympathetic dystrophy Neurogenic Bladder

Spastic bladder with or without detrusor-sphincter dyssynergia

Flaccid bladder

Gastrointestinal Dysmotility

Pseudo-obstruction

Sexual Dysfunction

Erectile dysfunction

Ejaculation dysfunction

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