Paraneoplastic neurologic syndromes are a heterogeneous group of neurologic disorders associated with systemic cancer and caused by mechanisms other than metastases, metabolic and nutritional deficits, infections, coagulopathy, or side effects of cancer treatment. These syndromes may affect any part of the nervous system from cerebral cortex to neuromuscular junction and muscle, either damaging one area or multiple areas.
Limbic encephalitis refers to an inflammatory process localized to structures of the limbic system that produces cognitive impairment along with disordered perception, mood changes, and sleep disturbances. The pathology and clinical and radiological findings are often not confined to these areas, however. Both paraneoplastic and nonparaneoplastic encephalitis share many clinical features and also have some that are distinctive. Response to treatment can be dramatic but is highly variable.
This topic discusses paraneoplastic and autoimmune encephalitis. An overview of paraneoplastic syndromes and other paraneoplastic disorders are discussed separately. (See "Overview of paraneoplastic syndromes of the nervous system" and "Paraneoplastic syndromes affecting peripheral nerve and muscle" and "Paraneoplastic syndromes affecting the spinal cord and dorsal root ganglia" and "Paraneoplastic cerebellar degeneration" and "Opsoclonus myoclonus ataxia".)
CLINICAL AND PATHOLOGICAL OVERVIEW
Paraneoplastic encephalomyelitis is characterized by involvement of several areas of the nervous system, including the temporal-limbic regions, brainstem, cerebellum, spinal cord, dorsal root ganglia, and autonomic nervous system [1,2]. The distribution of disease and symptoms varies.
Pathologic examination usually reveals perivascular and interstitial inflammatory infiltrates of T lymphocytes, gliosis, neuronophagic nodules, and loss of neurons. In addition to T-cell infiltrates, B-cells preferentially cluster around vessels and may be associated with plasma cell infiltrates [3,4]. The findings are typically more extensive than symptoms would suggest and may involve any area of the central nervous system, dorsal root ganglia, or autonomic neurons.