CASE 38: ORTHOSTATIC SYNCOPE
Following a year of erectile dysfunction and nocturnal urinary frequency, a 57-year-old man experiences blurred vision during exercise. Over the next several months, his symptoms increase; when he stands for more than a few minutes or walks a few hundred yards, he experiences constriction of his visual fields and loss of color perception followed by lightheadedness and diffuse weakness. If he does not then sit down, he loses consciousness. Neither pallor nor sweating precedes syncope. Over the next year, he develops slowly progressive facial immobility and bradykinesia but not tremor, ataxia, or dysarthria.
On examination, there is reduced facial expression and spontaneous blinking, and his limbs are mildly bradykinetic and rigid. When he is supine, his blood pressure is 130/80 mm Hg and his pulse rate is 76/minute; when he stands, his blood pressure falls to 95/40 mm Hg, his pulse rate does not change, and he experiences his usual dizziness and blurred vision. With the Valsalva maneuver—forcibly exhaling against a closed glottis—there is neither an increase nor a decrease in heart rate or blood pressure. Body warming with a heating cradle fails to produce sweating. Bladder catheterization after voiding reveals nearly 200 mL of residual urine, and slow instillation of fluid into the bladder produces an urge to void but reduced reflex contraction.
Basal levels of plasma norepinephrine are normal but fail to rise on standing. Subcutaneous injection of 0.25 mg of epinephrine produces a normal pressor and tachycardic response. Computed tomographic scan of the head, electromyography, and cerebrospinal fluid are normal.
Treatment of his postural syncope includes sleeping with his head elevated, wearing an elastic garment that compresses the lower abdomen, and daily oral administration of 9α-fluorohydrocortisone. His urinary retention is treated with oral bethanechol.
Although this patient has mild symptoms of parkinsonism (see Case 35), his functional disability is the result of autonomic dysfunction (Figure 13–1). Erectile dysfunction and bladder distention with a preserved sense of urinary urgency reflect efferent parasympathetic dysfunction. A fall in blood pressure greater than 30/15 mm Hg on standing and failure of the heart rate to increase when his blood pressure drops or during the Valsalva maneuver reflect sympathetic dysfunction, which theoretically could involve either the afferent or the efferent limb of the reflex arc. Failure to sweat in response to body warming indicates impairment of the efferent sympathetic pathway, which theoretically could be anywhere from the hypothalamus to the postganglionic peripheral sympathetic nerves.
Sympathetic and parasympathetic divisions of the autonomic motor system. The sympathetic ganglia lie close to the spinal column and supply virtually every tissue in the body. Some tissues, such as skeletal muscle, are regulated only indirectly through their arterial blood supply. The parasympathetic ganglia are located near their targets, which do not include the skin or skeletal muscle. (Reproduced with permission ...