Paraneoplastic neurologic disorders (PNDs) are cancer-related syndromes that can affect any part of the nervous system; caused by mechanisms other than metastasis or by complications of cancer such as coagulopathy, stroke, metabolic and nutritional conditions, infections, and side effects of cancer therapy. In 60% of pts the neurologic symptoms precede cancer diagnosis. PNDs occur in 0.5-1% of all cancer pts, but they occur in 2-3% of pts with neuroblastoma or small cell lung cancer (SCLC), and in 30-50% of pts with thymoma or sclerotic myeloma.
Recognition of a distinctive paraneoplastic syndrome (Table 79-1 Paraneoplastic Syndromes of the Nervous System) should prompt a search for cancer, because treatment of tumor may improve the course of PNDs; many of these disorders also occur without cancer. Diagnosis is based on the clinical pattern, exclusion of other cancer-related disorders, confirmatory serum or CSF antibodies, or occasionally electrodiagnostic testing. Most PNDs are mediated by immune responses triggered by neuronal proteins expressed by tumors. PNDs associated with immune responses against intracellular antigens often respond poorly to treatment (Table 79-2 Antibodies to Intracellular Antigens, Syndromes, and Associated Cancers), whereas those associated with antibodies to synaptic or neuronal cell surface proteins are more responsive to immunotherapy (Table 79-3 Antibodies to Cell Surface or Synaptic Antigens, Syndromes, and Associated Tumors). For any type of PND, if antibody testing is negative, the diagnosis rests on the demonstration of cancer and the exclusion of other cancer-related or independent disorders. Combined whole-body CT and PET scans often uncover tumors undetected by other tests.
MRI and CSF studies are important to rule out neurologic complications due to direct spread of cancer. In most PNDs the MRI findings are nonspecific. CSF findings typically consist of mild to moderate pleocytosis (<200 mononuclear cells, predominantly lymphocytes), an increase in the protein concentration, and a variable presence of oligoclonal bands.
Paraneoplastic Encephalomyelitis and Focal Encephalitis With Antibodies Against Intracellular Neuronal Proteins
Encephalomyelitis describes an inflammatory process with multifocal involvement of the nervous system (Table 79-2 Antibodies to Intracellular Antigens, Syndromes, and Associated Cancers). Clinical manifestations depend on area involved, and syndromes may occur alone or in combination.
TREATMENT | ||
Encephalomyelitis and Focal EncephalitisMost respond poorly to treatment. Stabilization of symptoms or partial neurologic improvement may occur, particularly if there is a satisfactory response of the tumor to treatment. Controlled trials of therapy are lacking; therapies aimed to remove antibodies against intracellular antigens, such as intravenous immunoglobulin (IVIg) or plasma exchange, usually fail. The main concern should be to treat the tumor and consider immunotherapies, such as cyclophosphamide or tacrolimus, aimed at controlling pathogenic cytotoxic T-cell responses. |
Encephalitides With Antibodies to Cell-Surface or Synaptic Proteins
These are a growing group of disorders that can occur with or without tumor association (Table 79-3 Antibodies to Cell Surface or Synaptic Antigens, Syndromes, and Associated Tumors). An example is N-methyl-D-aspartate (NMDA) receptor autoantibodies that present as a virus-like syndrome followed by a prominent psychiatric disturbance with involuntary movements; in young women, ovarian teratomas are frequently present. Relapses may occur. Despite dramatic severity at times, pts usually respond to treatment of the tumor (if found) and immunotherapy.
Encephalitis with leucine-rich glioma-inactivated 1 (LGI1) antibodies predominates in pts aged >50 years and frequently presents with memory loss and seizures (limbic encephalopathy), with hyponatremia and sleep dysfunction. In some pts, the encephalitis is preceded by or occurs with myoclonic-like movements called faciobrachial dystonic seizures.
Encephalitis with contactin-associated protein-like 2 (Caspr2) antibodies predominates in pts aged >50 years and is associated with Morvan's syndrome (encephalitis, insomnia, confusion, hallucinations, autonomic dysfunction, and neuromyotonia), or a form of encephalitis with three or more of the following core symptoms: encephalopathy, cerebellar symptoms, peripheral nervous system hyperexcitability, dysautonomia, insomnia, neuropathic pain, or weight loss.
Encephalitis with ;-aminobutyric acid type B (GABAB) receptor antibodies is usually associated with limbic encephalitis and seizures. In rare instances, pts develop cerebellar symptoms and opsoclonus.
Encephalitis with GABAA receptor antibodies associates with prominent seizures and status epilepticus, often requiring pharmacologically induced coma.
Encephalitis with AMPA receptor antibodies affects middle-aged women, who develop acute limbic dysfunction or, less frequently, prominent psychiatric symptoms; 70% of the pts have an underlying tumor in the lung, breast, or thymus. Neurologic relapses may occur; not necessarily associated with tumor recurrence.
TREATMENT | ||
Encephalitides with Antibodies to Cell-Surface or Synaptic ProteinsMost pts respond to immunotherapy and treatment of the tumor (if appropriate). Although there are no standardized treatment protocols, the most frequent approach employs progressive escalation of immunotherapy using first a combination of glucocorticoids, IVIg or plasma exchange, and if there is no response, either rituximab or cyclophosphamide. |
These disorders may develop anytime during the course of the neoplastic disease. Serum and urine immunofixation studies should be considered in pts with peripheral neuropathy of unknown cause; detection of a monoclonal gammopathy suggests the need for additional studies to uncover a B cell or plasma cell malignancy. If demyelinating features predominate (Chap. 196 Peripheral Neuropathies, Including Guillain-Barré Syndrome), IVIg, plasma exchange, or glucocorticoids may improve symptoms.
Myasthenia gravis is discussed in Chap. 197 Myasthenia Gravis and dermatomyositis in Chap. 198 Muscle Diseases.
Section 6. Hematology and Oncology