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of tumor.
The tumors most frequently involved are small cell lung cancer
(SCLC) (~3% of patients develop PND), thymoma (15%), and
plasma cell dyscrasias associated with malignant monoclonalgammopathies (~5% to 15%). With other solid tumors, the
incidence of PND is less than 1%.2
In 60% of patients with PND, symptoms develop before the
presence of a tumor is known; the majority of thesepatients
are seen by neurologists, who should be aware that prompt
diagnosis and treatment of the tumor along with immunotherapy
may stabilize or improve the PND. In 40% of patients,
symptoms ofPND develop after the tumor diagnosis or at
tumor recurrence. In this group of patients, the differential
diagnosis is extensive because PND may mimic many other
neurological complications ofcancer or its treatment. The
diagnosis of PND has been facilitated by serological tests that
are based on the detection of antineuronal antibodies in the
patients’ serum or cerebrospinal fluid (CSF),but in at least 40%
of patients, no antibodies are detected, and in some instances,
the antibodies can be detected in patients who have cancer but
not PND.3 Therefore, although testing for theseantibodies is
useful, it does not replace the importance of a comprehensive
clinical assessment that should always rule out other complications
of cancer. In addition to the immune-mediated PNDs,patients with cancer may develop neurological symptoms from
a large and heterogeneous group of mechanisms unrelated to
metastasis; these are not further discussed but are listed in
Table 101–2.IMMUNOPATHOGENESIS OF PARANEOPLASTIC
NEUROLOGICAL DISORDERS AND EFFECTS ON
THE TUMOR
Paraneoplastic Neurological Disorders of
the Central Nervous System
Many of these disorders occur inassociation with immune
responses against intraneuronal antigens expressed by the
underlying cancer (paraneoplastic or onconeuronal antigens).
These immune responses are characterized by the presence of...