Paraneoplastic disorders are, in general, autoimmune disorders that are triggered by tumors. These disorders are strongly cancer associated, meaning that each of these conveys a distinct risk profile for various tumors.  They involve T cell responses targeting the brain neuron.  These are called intracellular antigens (antibodies). Intracellular antibodies in Autoimmune Encephalitis attack the brain cell by seeping inside the cell.   These disorders tend to have a more malignant, severe clinical course.  Patients will show early atrophy on their MRI and tend to be in the ICU.  They may go into status epilepticus. Their EEG is typical of multi focal interictal epileptiform discharges (IEDs). So it is a wider spread disease. 

​

Since patients tend to have an underlying malignancy at the time of diagnosis, the physician will search intently for an underlying occult malignancy.  This is a cancer that is determined to be at the metastatic stage at the time of diagnosis but a primary tumor cannot be identified. The malignancy may not be found because it is microscopic so the physician will continue to screen the patient every 3 to 6 months. Tumor screening and treatment is essential to the proper management of these disorders for several reasons. 1) Treating the relevant tumor is thought to be helpful for treating the autoimmune disorder. 2) Tumor therapy and immune therapy may need to be given simultaneously and in a coordinated fashion. 3) Treatment with steroids, rituximab, or cyclophosphamide could complicate tumor diagnosis in the case of tumors like lymphoma.

​

Paraneoplastic disorders are associated with, but not caused by, the intracellular antibodies. The antibodies in these disorders are useful tumor markers, and aid the clinician as to where they need to search for an associated tumor.  For example, paraneoplastic syndromes such as cerebellar degeneration or limbic encephalitis are associated with highly specific antibodies against intracellular neuronal proteins and aggressive cytotoxic T cell responses that usually lead to irreversible functional and structural neuronal damage.

​

The prognosis tends to be poor because of the irreversible progressive neuronal cell death and neurological decline caused by these antibodies; the severity of associated cancers, and the difficulty in controlling these sorts of T-cell immune responses targeting the brain cells because they tend to not respond to immunotherapy.