Porth's Essentials of Pathophysiology, 4e

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Nervous System

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with previous relapsing-remitting disease. Primary progressive disease is characterized by nearly continu- ous neurologic deterioration from onset of symptoms. The progressive relapsing category of disease involves gradual neurologic deterioration from the onset of symptoms but with subsequent superimposed relapses. Diagnosis andTreatment The diagnosis of MS is based on evidence of CNS lesions that are disseminated in time and space (i.e., occur in different parts of the CNS at least 3 months apart), with no explanation for the disease process. 46,47,51 MRI, which is a sensitive diagnostic tool that is an adjunct to clinical diagnosis, can detect lesions even when CT scans appear normal. A computer-assisted method of MRI can measure lesion size. Many new areas of myelin abnormality are asymptomatic. Serial MRI studies can be done to detect asymptomatic lesions, monitor the progress of existing lesions, and evaluate the effective- ness of treatment. Although MRI can be used to pro- vide evidence of disseminated lesions in persons with the disease, normal findings do not exclude the diagnosis. Electrophysiologic evaluations (e.g., evoked potential studies) and CT scans may assist in the identification and documentation of lesions. Most treatment measures for MS are directed at modifying the course and managing the primary symp- toms of the disease. 46,47 The variability in symptoms, unpredictable course, and lack of specific diagnostic methods has made the evaluation and treatment of MS difficult. Persons who are minimally affected by the dis- order require no specific treatment. The person should be encouraged to maintain as healthy a lifestyle as pos- sible, including good nutrition and adequate rest and relaxation. Physical therapy may help maintain muscle tone. Every effort should be made to avoid excessive fatigue, physical deterioration, emotional stress, viral infections, and extremes of environmental temperature, which may precipitate an exacerbation of the disease. The pharmacologic agents used in the treatment of MS fall into three categories: those used to (1) treat acute attacks or initial demyelinating episodes, (2) mod- ify the course of the disease, and (3) treat symptoms of the disorder. 46 Corticosteroids are the mainstay of treat- ment for acute attacks of MS. These agents are thought to reduce the inflammation, improve nerve conduction, and exert important immunologic effects. Long-term administration does not, however, appear to alter the course of the disease and can have harmful side effects. Adrenocorticotropic hormone (ACTH) also may be used in the treatment of MS. Plasmapheresis has also proved beneficial in some cases. 46 Disease-modifying agents include interferon- β and glatiramer acetate. 46,47,52 These agents have shown some benefit in reducing exacerbations in persons with relaps- ing-remitting MS. Interferon- β is a cytokine that acts as an immune enhancer. Two forms have been approved by the FDA for treatment of MS—interferon- β 1a and interferon- β 1b. Both are administered by injection, and both are usually well tolerated. Glatiramer acetate is a

synthetic polypeptide that simulates parts of the myelin basic protein. Although the exact mechanism of action is unknown, the drug appears to block myelin-damaging T cells by acting as a myelin decoy. The drug is given daily by subcutaneous injection. Mitoxantrone, an anti- cancer drug, is recommended for persons with wors- ening forms of the disease. Because it is an anticancer drug, it is recommended that it only be administered by experienced health care professionals. Other promising therapies that focus on immune-mediated disease mech- anisms are in development. Among the medications used to manage the chronic problems associated with MS are dantrolene, baclofen, or diazepam for spasticity; cholinergic drugs for bladder problems; and antidepressant drugs for depression. Vertebral and Spinal Cord Injury Spinal cord injury (SCI) represents damage to the neural elements of the spinal cord. Spinal cord injury is primar- ily a disorder of young people, with nearly half of all inju- ries occurring in the 16- to 30-year-old age group. 53 The most common cause of SCI is motor vehicle accidents, followed by falls, violence (primarily gunshot wounds), and recreational sporting activities. 53 Life expectancy for persons with SCI continues to increase, but is somewhat below life expectancy for people without SCI. Most SCIs involve damage to the vertebral column or supporting ligaments as well as the spinal cord. Because of extensive tract systems that connect sensory affer- ent neurons and LMNs with higher brain centers, SCIs commonly involve both sensory and motor function. Although the discussion in this section of the chapter focuses on traumatic SCI, much of the content is appli- cable to SCI caused by other disorders, such as congeni- tal deformities (e.g., spina bifida), tumors, ischemia and infarction, and bone disease with pathologic fractures of the vertebrae. Injury to theVertebral Column Injuries to the vertebral column include fractures, dis- locations, and subluxations. A fracture can occur at any part of the bony vertebrae, causing fragmentation of the bone. It most often involves the pedicle, lamina, or processes (e.g., facets, see Fig. 36-9). Dislocation or subluxation (partial dislocation) injury causes the ver- tebral bodies to become displaced, with one overriding another and preventing correct alignment of the verte- bral column. Damage to the ligaments or bony verte- brae may make the spine unstable. In an unstable spine, further unguarded movement of the spinal column can impinge on the spinal canal, causing compression or overstretching of neural tissue. Most injuries result from some combination of com- pressive force or bending movements. 18 Flexion inju- ries occur when forward bending of the spinal column exceeds the limits of normal movement. Typical flexion injuries result, for example, when the head is struck from behind, as in a fall with the back of the head as the point of impact. Extension injuries occur with excessive