In patients without measurable autoantibody but in whom the neurologist strongly suspects a paraneoplastic syndrome, a search for cancer is indicated. It is important to recognize that an initial search for cancer may be negative even when the disorder is paraneoplastic. If the initial search does not reveal a cancer, the patient should be followed carefully, and the work-up should be repeated in several months if a strong suspicion of a paraneoplastic syndrome is still present. The treatment varies with the nature of the disorder. Because many paraneoplastic syndromes affecting the central nervous system destroy neurons, treatment often fails to improve the neurologic disorder.
Some paraneoplastic disorders resolve spontaneously.
Because these disorders sometimes resolve spontaneously, it is difficult to assess the results of treatment directed at those disorders. Unfortunately, some disorders usually do not respond to any treatment, whether directed at the tumor or at the immune system. These include most instances of PCD associated with either lung cancer or gynecologic cancers, most instances of paraneoplastic sensory neuronopathy or PEM associated with SCLC, most instances of cancer-associated retinopathy, and many of the peripheral neuropathies associated with cancer. If any treatment is to be effective against disorders that destroy neurons, it must be delivered early in the course of the disease, before the neurons are destroyed. Because the symptoms often develop subacutely, maximal damage to neurons may already have occurred by the time the neurologist sees the patient and establishes the diagnosis.