Symptoms of MS are unpredictable, vary from person to person, and may vary from patient to patient at different times. Some patients may experience abnormal fatigue, numbness and tingling, others may have difficulty walking due to loss of balance and muscle coordination, and others may have slurred speech, tremors, stiffness, and bowel and urinary problems. The symptoms of MS often recover completely in the early stages of the disease, but as the disease progresses, some symptoms do not recover completely, leaving sequelae that accumulate and lead to permanent, irreversible disability, including partial or complete paralysis, and non-recoverable symptoms of vision, cognition, and speech.