Orchiectomy for suspected microscopic tumor in patients with anti-Ma2-associated encephalitis

Paraneoplastic syndromes of the CNS

Major advances in the management of paraneoplastic neurologic disorders (PND) include the detection of new antineuronal antibodies, the improved characterisation of known syndromes, the discovery of new syndromes, and the use of CT and PET to reveal the associated tumours at an early stage. In addition, the definition of useful clinical criteria has facilitated the early recognition and treatment of these disorders. In this article, we review some classic concepts about PND and recent clinical and immunological developments, focusing on paraneoplastic cerebellar degeneration, opsoclonus-myoclonus, and encephalitides affecting the limbic system.

Paraneoplastic neurological syndromes: diagnosis and treatment

PURPOSE OF REVIEW

The most relevant advances in the field of paraneoplastic neurological syndromes are described, with special emphasis on particular clinical-immunological associations and practical issues for the diagnosis and treatment of these disorders.

RECENT FINDINGS

Paraneoplastic neurological syndromes may present with classical neurological symptoms or less frequently with symptoms that do not initially raise suspicion of these disorders. Recent examples include patients who present with epilepsia partialis continua or frontal disequilibrium associated with Hu antibodies, hypersommnia and anti-Ma2 antibodies, Devic's syndrome and CV2/CRMP5 antibodies and a syndrome characterized by psychiatric features and central hypoventilation in young women with anti-N-methyl-D-aspartate receptor antibodies. The cause of the neuronal damage is still open to debate. The recent description of antibodies against membrane proteins in opsoclonus or encephalitis associated with teratoma strongly suggests that antibodies may be responsible for the clinical features in some cases. Early diagnosis and effective treatment of the tumor remain the best options to improve or stabilize the syndrome. Immunotherapy, including rituximab, seems effective in those cases associated with functional damage.

SUMMARY

Neurologists must be aware of neurological syndromes that may have a paraneoplastic origin. Detection of onconeural antibodies is crucial to make the correct diagnosis. Immunotherapy should be used, although the impact of the treatment is unclear in cases with irreversible neuronal damage.

Limbic encephalitis and variants: classification, diagnosis and treatment

BACKGROUND AND OBJECTIVE

Recent studies suggest that a substantial number of patients with autoimmune limbic encephalitis may improve if properly diagnosed and treated. This is due, in part, to the increasing recognition of disorders that associate with antibodies to neuronal cell membrane antigens. This review focuses in these disorders, framed in a clinically useful immunologic classification of limbic encephalitis.

REVIEW SUMMARY

Patients with limbic encephalitis usually present with rapidly progressive short-term memory deficits, psychiatric symptoms, and seizures. After excluding viral and systemic autoimmune disorders, many patients with limbic encephalitis (paraneoplastic or not) have cerebrospinal fluid inflammatory findings, EEG or MRI abnormalities in the temporal lobes, and antineuronal antibodies. These antibodies are directed against 2 broad categories of antigens: (1) intracellular or classic paraneoplastic antigens, including Hu, Ma2, CV2/CRMP5, and amphiphysin among others, and (2) cell membrane antigens, including voltage-gated potassium channels, N-methyl-D-aspartate receptor, and others expressed in the neuropil of hippocampus and cerebellum (pending characterization). Whereas the disorders related to the first category of antibodies associate with cancer (lung, testis and other), prominent brain infiltrates of cytotoxic T-cells, and limited response to treatment, the disorders related to the second category of antibodies associate less frequently with cancer (thymoma, teratoma), seem to be antibody-mediated, and respond significantly better to immunotherapy.

CONCLUSIONS

Once considered an extremely rare disorder, almost always related to cancer, and refractory to treatment, limbic encephalitis is now regarded as a relatively frequent disorder, often unrelated to cancer, and with clinical-immunologic variants that respond to treatment.

Rapidly progressive dementia

Rapidly progressive dementias (RPDs) are neurologic conditions that develop subacutely over weeks to months or, rarely, acutely over days. In contrast to most dementing conditions that take years to progress to death, RPD quickly can be fatal. It is critical to evaluate patients who have RPD without delay, usually in a hospital setting, as they may have a treatable condition. This review discusses a differential diagnostic approach to RPD, emphasizing neurodegenerative, toxic and metabolic, infectious, autoimmune, neoplastic, and other conditions to consider.