Introduction Rituximab is occasionally used by neurologists in treatment–resistant immune–mediated disease. Enterovirus encephalitis is a potential complication of treatment with rituximab that can be treated with intravenous immunoglobulin (IvIg). Reports of this complication have almost exclusively been in hematology/oncology literature. We describe such a case to increase the neurology community's awareness of this complication and its potential treatment with IvIg.

Case Report A 72 year old female presented to the neurology service following an unwitnessed collapse. She had a history of a pancreatic large B cell lymphoma the previous year for which she had received 6 cycles of R–CHOP therapy (rituximab with cyclophosphamide, doxorubicin, vincristine and prednisone). She was admitted to hospital but no cause for collapse was found. She declined cognitively over the following months and was readmitted. She continued to deteriorate in hospital and developed acute onset of left sided weakness, neglect and homonymous hemianopia. She talked incessantly even when nobody was with her. She then developed epilepsy partialis continua. This was successfully treated with phenytoin and levetiracetam. MRI showed signal change in the thalamus and motor cortex on the right. EEG showed right sided PLEDs. Her CSF PCR for enterovirus was positive. Based on this she was treated with intravenous immunoglobulin and made a dramatic recovery.

Discussion Enterovirus encephalitis is a recognised complication of rituximab treatment. However, it has thus far been largely reported in haematology and oncology journals. Rituximab is being used more frequently by neurologists and it is important to be aware of this complication as it can be successfully treated. The difficulty in making a prompt diagnosis of enteroviral meningoencephalitis lies in its presentation with non–specific neurological symptoms and a low index of suspicion.¹ Also, early on in the disease the viral load in the CSF may be low and therefore difficult to detect. Rituximab is a chimeric anti–CD20 monoclonal antibody. It induces a long lasting depletion of B cells that can lead to agammaglobulinaemia, predisposing patients to infection.² Enterovirus causes a lytic infection that is controlled by neutralizing antibodies. An intact humoral immune system is necessary to prevent infection.³ Intravenous immunoglobulin is a recognised treatment for enterovirus encephalitis. It is thought to work by restoring neutralising antibodies.³ Finally, our patient developed epilepsy partialis continua that has to the best of our knowledge, not been previously reported in enterovirus encephalitis.

Conclusion As rituximab is increasingly used, neurologists are likely to encounter more patients with this rare complication and should be aware that it may develop. In addition it has a unique treatment (intravenous immunoglobulin) that can result in dramatic recovery.