IS THERE A CURE FOR AUTOIMMUNE ENCEPHALITIS?
While there is no known cure for autoimmune encephalitis, this question needs clarification. For that, we reached out to Dr. Josep Dalmau who identified the first antibody in AE, along with many other antibodies, and is a world-renown expert. Here is his explanation.
“Autoimmune encephalitides are not one but many diseases. Many patients with these diseases are cured and never have any relapses or need further treatments. As with many other diseases, some patients are cured with one type of treatment or combination of treatments, and other patients are cured with other treatments or combinations.
The fact that a disease is cured does not necessarily mean that all patients need to be treated with the same drug or “magic bullet”, it depends on the patient and the disease. These concepts apply even for cancer; there are many patients with cancer that are cured. Not all receive the same treatment. The treatment varies with the type of cancer, and even with a specific type of cancer, not all patients are treated similarly. This example applies to many different diseases.
The question can be formulated as: Are there patients with autoimmune encephalitis that are eventually cured? Answer: Yes.”
Autoimmune Encephalitis often has a single phase. Instances of spontaneous recovery without immunotherapy or tumor removal, when present, have been reported. A patient enters recovery when the disease is no longer present. However, recovery from Autoimmune Encephalitis is not without the patient experiencing abnormality following the disease or permanent deficits resulting in an acquired brain injury (ABI) because of the disease. Deficits the patient experiences in cognitive domains at the beginning of their recovery may slowly improve even years following the end of treatment. Rehabilitation plays an important role in re-learning and re-training the brain from an acquired brain injury. (See: Rehabilitation cognitive exercises). Persistent cognitive impairment observed in long-term follow-up suggests irreversible neuronal death.
Because the largest cohort study followed patients for a two-year period, and longer studies have not been produced, percentages of improvement are based on that timeline. AE has a 7% mortality rate. AE-related deaths during the acute stage or follow up after discharge from the hospital have also been noted. Even if patients survive without immunotherapy, they may suffer a slower recovery requiring prolonged hospitalization.
Treatment for AE is a marathon, not a sprint. In practice, most patients are treated with glucocorticoids, intravenous immune globulin, or plasma exchange, and if there is no clinical response, rituximab and cyclophosphamide are used. Rituximab is usually effective in cases resistant to treatment. Rituxan appears to reduce the risk of a clinical relapse, which accounts for its increasing use as an initial treatment.
The speed of recovery, degree of residual deficit, and frequency of relapse vary according to the type of autoimmune encephalitis. In a series of 577 patients with anti-NMDAR encephalitis, the most common type of AE, 53% had clinical improvement within 4 weeks, and 81% had substantial recovery (i.e., mild or no residual symptoms) at 24 months. Anti-NMDAr recovery is often protracted with long hospital admissions. One remarkable feature of NMDAR encephalitis is the prolonged recovery, with progressive improvements in cognitive domains noted for months and even years following the end of treatment. Another study showed that patients with anti-LGI1 encephalitis, the second most common type of AE, had a more rapid response to treatment but that only 70% had substantial recovery at 24 months.
Two independent predictors of good outcome included the lower severity of symptoms assessed and no need for ICU support. For all types of autoimmune encephalitides, prompt immunotherapy has been associated with a favorable outcome; spontaneous clinical improvement is infrequent.
The rapid increase in the number of syndromes and autoantibodies identified since the first antibody was identified in 2007 suggests that other autoimmune encephalitides have yet to be discovered. Antibody titers correlate imperfectly with the course of the disease and may remain detectable (albeit at a low titer) after clinical recovery.
Relapse of encephalitis was defined as the new onset or worsening of symptoms occurring after at least two months of improvement or stabilization. Patients without a tumor had a higher frequency of relapses than those with a tumor. If a tumor is found, removal is important because it expedites improvement and decreases relapses.
The frequency of clinical relapse in the encephalitides associated with antibodies against NMDAR, AMPAR, LGI1, CASPR2, or DPPX ranges from 12 to 35%. The relapse rate in NMDAR encephalitis is reported to be 12–25 %, and relapses may occur in cases of anti-LGI1 or anti-NMDAR encephalitis months to several years after the initial episode. Relapses often occur when immunotherapy is reduced or discontinued. Relapses may herald recurrence of the associated tumor or a tumor that was missed in the initial episode. Immunotherapy and treatment of the tumor, if it was missed initially, usually result in improvement.
Relapses in NMDAR Ab encephalitis are often less severe and may be mono- or pauci-symptomatic. In children, atypical presentations such as cerebellar ataxia or brainstem signs have been described. The majority of relapses occur in patients who do not have a tumor associated with NMDAR Ab encephalitis, those who received no or limited treatment for the initial episode, and those not exposed to second-line agents. Second-line immunotherapy also appears to prevent further relapses in those with a multi relapse disease course. At present, there is no clinical or paraclinical predictive marker for relapses. Although alterations in CSF Ab titers relate well to clinical changes, it is impractical and perhaps unsafe to conduct CSF analysis for predictive purposes in well patients. Changes in serum Ab titers were not well correlated with relapses. The effects of long-term immunosuppression with oral agents such as azathioprine or CellCept (mycophenolate mofetil) on relapse rate is currently unknown.
Following antibody titers in the management of patients has several limitations and rarely helps guide therapy, which should be based on clinical ﬁndings as titers are not reliable markers of disease severity, but they can sometimes predict relapses and support the use of prolonged immunotherapy for prevention.
To prevent relapses and maximize the response to acute phase therapy, maintenance immunotherapy should be instituted especially if early relapses during steroid taper occur. Commonly used drugs in this phase include oral corticosteroids, IVIG, and steroid sparing agents such as mycophenolate mofetil, azathioprine, and rituximab. There are no guidelines regarding treatment duration; maintenance therapy is typically continuing for 3 years after stability is achieved. It is important to remember that the prolonged use of immunosuppressive medications increases the risk of lymphoproliferative disorders, and they have also been associated with progressive multifocal leukoencephalopathy.
The NEOS Score, just published December 2018, accurately predicts 1-year functional status in patients with anti-NMDAR encephalitis. This score could help estimate the clinical course following diagnosis and may aid in identifying patients who could benefit from novel therapies.
During the 24-month follow-up, 45 patients (representing a 12% risk) had clinical relapses, which in 15 patients (33%) were multiple. Compared with the initial episode, (67%) relapses were less severe (as reflected by a lower mRS score measured at the stage of maximum severity), more frequently mono-symptomatic (35%), and resulted in fewer admissions (17%) to the ICU (all p<0·0001). In 16 relapses (23%) the severity of symptoms was comparable to that of the initial episode, and in (10%) was worse.