Paraneoplastic syndromes are autoimmune in nature and represent a cross-reactivity between antibodies produced in response to neoplasms and normal tissue. Neurologic paraneoplastic syndromes include limbic encephalitis, cerebellar degeneration, retinal degeneration, opsoclonus-myoclonus, neuromuscular syndromes, neuropathies, and myopathies. These are diagnostically challenging for 2 reasons. First, at the time of onset of neurologic symptoms, the underlying cancer may not have been manifested clinically. It is not unusual for paraneoplastic syndromes to precede the detection of a systemic cancer by months or years. Second, paraneoplastic syndromes can be difficult to diagnose because of their similarity to other neurologic disorders that can mimic paraneoplastic syndromes. Treatment of the primary malignancy may reverse the course of the paraneoplastic syndrome.
Limbic encephalitis is characterized by subacute progressive cognitive changes, including affective symptoms and memory impairment. Men are affected more often than women. The major differential diagnosis is herpes simplex virus encephalitis. In addition, small cell lung cancer and testicular cancer are the most common malignancies associated with limbic encephalitis. In all, 2% to 3% of patients with small cell lung cancer will develop this neurologic complication. An immunologic or viral role in the pathophysiology has been suggested.
Zuheir al Kawi from Riyadh Armed Forces Hospital, Saudi Arabia, reported serial MRI findings in a 25-year-old man with limbic encephalitis. The neurologic symptoms began several months after orchiectomy for nonmetastatic testicular malignancy. MRI of the brain performed over 4 months showed bilateral progressive asymmetric hyperintense lesions on T2-weighted images in medial temporal gray matter structures. No enhancement was detected with gadolinium. Lesions led to atrophy of the temporal lobe. PET scanning revealed hypermetabolism of the lesions. This study should lead to increased recognition of limbic encephalitis.
Medscape Neurology. 2003;5(1) © 2003 Medscape
Cite this: Highlights of the 26th Annual Meeting of the American Society of Neuroimaging - Medscape - Mar 27, 2003.