Anesthesia for Multiple Sclerosis

MULTIPLE SCLEROSIS

Preoperative Considerations

Multiple sclerosis (MS) is characterized by revers-ible demyelination at random and multiple sites in the brain and spinal cord; chronic inflammation, however, eventually produces scarring (gliosis). The disease may be an autoimmune disorder that is ini-tiated by a viral infection. It primarily affects patients between 20 and 40 years of age, with a 2:1 female predominance, and typically follows an unpredict-able course of frequent attacks and remissions. With time, remissions become less complete, and the dis-ease progresses to incapacitation; almost 50% of patients will require help with walking within 15 years of diagnosis. Clinical manifestations depend on the sites affected, but frequently include sensory disturbances (paresthesias), visual prob-lems (optic neuritis and diplopia), and motor weak-ness. Symptoms develop over the course of days and remit over weeks to months. Early diagnosis of exacerbations can often be confirmed by analysis of cerebrospinal fluid and magnetic resonance imag-ing. Remyelination is limited and often fails to occur. Moreover, axonal loss can develop. Changes in neurological function seem to be related to changes in axonal conduction. Conduction can occur across demyelinated axons, but seems to be affected by multiple factors, particularly temperature. Increases in body temperature cause exacerbation of symptoms.

The treatment of MS may be primarily symp-tomatic or used in an attempt to arrest the disease process. Diazepam, dantrolene, or baclofen, and, in refractory cases, an intrathecal delivery system for baclofen are used to control spasticity; bethanechol and other anticholinergics are useful for urinary retention. Painful dysesthesia may respond to car-bamazepine, phenytoin, or antidepressants. Glu-cocorticoids may decrease the severity and duration of acute attacks. Corticosteroid-resistant relapses may respond to five to seven courses of plasma exchange offered on alternate days. Interferon has also been used to treat MS. Immunosuppression with azathioprine or cyclophosphamide may also be attempted to halt disease progression. Mito-xantrone is used for relapsing and progressive MS. The systemic effects of these therapies on coagu-lation and immunologic and cardiac function should be reviewed preoperatively.

Anesthetic Considerations

The effect of stress, anesthesia, and surgery on the course of MS is controversial. Overall, the effect of anesthesia is unpredictable. Elective surgery should be avoided during relapse, regardless of the anesthetic technique employed. The preoperative consent record should document counseling of the patient to the effect that the stress of surgery and anesthesia might worsen the symptoms. Spinal anesthesia has been associated with exacerbation of the disease; however, the entire surgery/delivery/anesthetic process may likewise lead to exacerba-tions. Peripheral nerve blocks are less of a concern because MS is a disease of the central nervous system; however, patients may also have periph-eral neuropathies. Epidural and other regional techniques seem to have no adverse effect on the course of the disease. No specific interactions with general anesthetics are recognized. Patients with advanced disease may have a labile cardiovascular system due to autonomic dysfunction. In the set-ting of paresis or paralysis, succinylcholine should be avoided because of hyperkalemia. Regardless of the anesthetic technique employed, increases in body temperature should be avoided. Irrespective of anesthetic technique, patients may experience a worsening of symptoms perioperatively and should be counseled accordingly.