Neurogenic Orthostatic Hypotension and Autonomic Failure
Orthostatic hypotension (OH): fall of 20 mmHg in systolic blood pressure or 10 mmHg diastolic within 3 minutes after changing position from supine to standing or similar orthostatic challenge, such as ≥60° upright tilt. May be asymptomatic, especially in elderly. Marker of advanced autonomic failure.
Multiple System Atrophy (MSA)
Autonomic failure present in 97% patients with any form of MSA (see Chapter 115). When present early in course, condition also referred to as Shy-Drager syndrome. (Other forms of MSA: striatonigral degeneration; olivopontocerebellar atrophy.)
Clinical features: OH or syncope often first and most disabling symptom. Parkinsonism sometimes mild or absent for years after onset of autonomic failure. Other features: inspiratory stridor from vocal fold paralysis; urinary incontinence; sleep disturbance.
Laboratory data: abnormal autonomic tests (Table 137.1), anal sphincter EMG (denervation), sleep tests (e.g., sleep apnea). Supine blood levels of norepinephrine (NE) normal or slightly reduced; does not increase on head-up tilt.
Pathology: argyrophilic glial cytoplasmic inclusions in oligodendroglia, especially in CNS autonomic control centers.
Prognosis: progression to severe disability in several years. Worse prognosis than Parkinson disease with autonomic features.
Table 137.1 Tests of Autonomic Function | |||
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