Autonomic dysfunction with orthostatic hypotension

Pupil abnormalities in selected autonomic neuropathies

Examination of the pupil provides an opportunity to detect disturbances in the autonomic innervation of the eye. The pupil is frequently affected in patients with generalized autonomic neuropathies. This literature review confirms a high prevalence of sympathetic deficits and parasympathetic deficits in acute or subacute dysautonomia, diabetes, amyloidosis, pure autonomic failure, paraneoplastic syndromes, Sjögren syndrome, familial dysautonomia, and dopamine beta-hydroxylase deficiency. It confirms the relative scarcity of a pupil abnormality in patients with multiple system atrophy. There are difficulties in clinical diagnosis of pupil abnormalities and interpretation of pupil pharmacologic tests, particularly when combined sympathetic and parasympathetic deficits are present.

Disorders of the autonomic nervous system: Part 1. Pathophysiology and clinical features

Autonomic dysfunction may result from diseases that affect primarily either the central nervous system or the peripheral autonomic nervous system. The most common pathogenesis of disturbed autonomic function in central nervous system diseases is degeneration of the intermediolateral cell columns (progressive autonomic failure) or disease or damage to descending pathways that synapse on the intermediolateral column cells (spinal cord lesions, cerebrovascular disease, brainstem tumors, multiple sclerosis). The peripheral autonomic nervous system may be damaged in isolation in the acute and subacute autonomic neuropathies or in association with a generalized peripheral neuropathy. The peripheral neuropathies most likely to cause severe autonomic disturbance are those in which small myelinated and unmyelinated fibers are damaged in the baroreflex afferents, the vagal efferents to the heart, and the sympathetic efferent pathways to the mesenteric vascular bed. Acute demyelination of the sympathetic and parasympathetic nerves in the Guillain-Barré syndrome may also cause acute autonomic dysfunction. Although autonomic disturbances may occur in other types of peripheral neuropathy, they are rarely clinically important.

Effect of infused L-threo-3,4-dihydroxyphenylserine on adrenergic activity in patients with familial amyloid polyneuropathy

L-threo-3,4-dihydroxyphenylserine (DOPS), an immediate precursor amino acid of (-)-norepinephrine, was used as a pharmacological tool to investigate the pathophysiology of the peripheral sympathetic nervous system in Type 1 familial amyloid polyneuropathy. Patients with the well-established disorder showed an enhanced pressor response to L-threo-DOPS under conditions that produced no change in normal subjects. While octopamine induced a brisk pressor response, L-threo-DOPS produced a slow and prolonged change in blood pressure, with a marked concomitant increase in urinary excretion of norepinephrine. A slight increase in urinary excretion of total metanephrine was observed in both groups, but there was no significant increase in serum dopamine-beta-hydroxylase activity. Since infusion of dilute norepinephrine into patients also produced a markedly hypersensitive response, the characteristic pressor response to L-threo-DOPS was indicative of denervation supersensitivity of adrenergic receptors to norepinephrine formed enzymatically from L-threo-DOPS.