78. Shy-Drager Syndrome
Definition
Shy-Drager syndrome (SDS) is a sporadic, rare, progressive neurodegenerative disease characterized by features of parkinsonism, autonomic failure, and cerebellar or pyramidal dysfunction. Shy-Drager syndrome is also known as striatonigral degeneration, olivopontocerebellar atrophy, and multiple system atrophy.
Incidence
In the United States, the frequency of SDS is about 2:100,000 to 15:100,000. The frequency in other countries varies considerably. Men are more likely to be stricken than women, by a 3:1 to 9:1 ratio. Disease onset typically occurs between the ages of 52 and 55 years. The disease progresses over a period of 1 to 18 years, with a mean survival of 6 to 9.5 years.
Etiology
The cause of SDS is not known. There have been anecdotal suggestions of exposure to environmental toxins or trauma as causative agents, but none have been confirmed. Changes to the interomediolateral cell column have been documented as well as widespread brain anomalies. Neuronal losses have been documented in several brain regions.
Areas of Neuronal Loss in Shy-Drager Syndrome
• Basal ganglia
• Cerebellum
• Hypothalamus
• Locus ceruleus
• Nucleus of Edinger-Westphal
• Pons
• Substantia nigra
• Thalamus
• Vestibular complex
Signs and Symptoms
• Anhidrosis
• Ataxia
• Bowel dysfunction
• Bradykinesia
• Cardiac dysrhythmias
• Central sleep apnea
• Cerebellar uncoordination
• Chronic orthostatic hypotension
• Constipation
• Coarse leg tremors
• Dysdiadokinesia (inability to perform rapid, alternating movements)
• Dysmetria
• Episodic unconsciousness
• Erectile dysfunction
• Eye movement abnormalities
• Fasciculations
• Generalized neurologic dysfunction
• Muscle rigidity
• Muscle wasting
• Nausea
• Obstructive sleep apnea
• Paradoxical supine hypertension
• Truncal instability
• Urinary incontinence
• Vocal cord paralysis or dysfunction
Medical Management
There is no medical therapeutic measure, pharmacologic or nonpharmacologic, that can alter the course of Shy-Drager syndrome. It cannot be halted, reversed, or cured. Treatment measures are aimed at symptomatic relief. Orthostatic hypotension is a sentinel symptom for SDS patients and can dramatically interfere with a patient’s daily life. Patients can incorporate various mechanical maneuvers to drastically reduce, if not alleviate, episodes of orthostatic hypotension (e.g., leg-crossing, squatting, abdominal compression, placing one foot on a chair). Paradoxical supine hypertension is a frequently occurring entity associated with SDS. To avoid the supine hypertension, patients are instructed not to lie down during the day. Sleeping at night with the head of the bed elevated about 30 degrees helps reduce the hypertension and the degree of orthostatic hypotension. There are several medications that may be used to treat orthostatic hypotension, such as fludrocortisone acetate, midodrine, dihydroxyphenylserine, epoetin alpha, indomethacin or ibuprofen, diphenhydramine, cimetidine, somastatin, octreotide, or desmopressin. The applicability of these pharmacologic interventions is limited by the supine hypertension. Patients who have profound bradycardia may have an atrial pacemaker inserted to treat the bradycardia and orthostatic hypotension.
The movement disorder of SDS may be treated with levodopa, dopaminergic agonists, anticholinergics, or amantadine. The response to these medications is usually favorable. The response produced is not as favorable, however, as that seen in patients with classic Parkinson’s disease.
Complications
• Changes in alertness
• Delusions
• Disorientation
• Dizziness
• Hallucinations
• Injuries due to falls or syncope
• Involuntary movements
• Loss of mental function
• Nausea
• Progressive loss of ability to ambulate or care for self
• Severe confusion
• Side effects of medications for symptom alleviation
• Vomiting
Anesthesia Implications
Hemodynamic stability must be foremost in the mind of the anesthetist caring for the patient with SDS. The first step toward fostering the patient’s hemodynamic stability should be to ensure optimization of the patient’s fludrocortisone therapy. Perioperatively the patient should be invasively monitored with interarterial cannulization as well as central venous pressure and/or pulmonary artery catheterization, depending on the complexity of the intended surgery, to guide fluid resuscitation and blood loss replacement. Crystalloids, colloids (fluid expanders), and blood or blood products should be given to preserve normotension by maintaining normovolemia because the patient’s response to vasoactive amines is unpredictable. The autonomic denervation that occurs with this disease process produces sympathetic hypersensitivity. As a result, vasoactive amines must be administered judiciously to treat intraoperative hypotension using significantly reduced doses.
Supine hypertension, which is common with this disease, has been treated with labetalol, but the response reported was minimal. However, administration of hydralazine to treat supine hypertension produced a profound hypotension that could only be rectified with a vasopressin infusion. The supine hypertension does respond quite favorably to either a sodium nitroprusside infusion or transdermal nitroglycerin application.
Regional anesthesia is effective in patients with SDS. Patients with SDS tolerate the regional anesthesia–induced sympathectomy considerably better (i.e., without the hypo-tension generally observed) than unaffected patients, possibly because they are already experiencing a constant sympathectomy as a result of the disease process.
General anesthesia can be achieved and maintained with any of the volatile agents. There have been no reports of unexpected untoward effects from any of the currently available anesthetic agents. The anesthetist should keep in mind that central sleep apnea, obstructive sleep apnea, and stridor are all commonly seen in patients with SDS. Prior planning, understanding, and cooperation with the patient are required with regard to extubation at the end of surgery, particularly for a patient with a history of either form of sleep apnea or with a history of stridor. The anesthetist may wish to somewhat reduce the dose of benzodiazepine and/or opioid because of the heightened potential for respiratory embarrassment. It may be prudent to arrange for an overnight observation in the intensive care unit so that the patient’s respiratory status can be closely monitored for the first 24 hours postoperatively.
