Intravenous immunoglobulins for treatment of severe COVID-19-related acute encephalopathy

Coronavirus disease 2019 (COVID-19) patients on intensive care units (ICU) frequently present with acute encephalopathy that appears to be distinct from other ICU-related encephalopathies regarding higher incidence, longer duration, and increased severity including autonomous dysregulation and non-satisfactory response to neuroleptic drugs [1]. According to the updated nomenclature of delirium and acute encephalopathy, we use the term acute encephalopathy to describe a rapidly developing pathobiological brain process, expressed clinically as delirium, subsyndromal delirium or coma with partly additional neurological findings such as extrapyramidal signs or seizures [2]. This type of acute encephalopathy is associated with delayed recovery, weaning failure, prolonged ICU or hospital stay, or even impaired clinical outcome. First reports found positive responses of COVID-19-associated encephalopathy to immunotherapy [3–5] that supported the hypothesis of a possible inflammatory pathomechanism [6]. However, this encephalopathy might still be misjudged by intensivists as poorly treatable with limited prognosis, risking premature withdrawal of ICU therapy or even end-of-life decisions in affected patients. Therefore, our case series demonstrates a promising and rapid effect of intravenous immunoglobulins (IVIg) on otherwise treatment-refractory acute encephalopathy in COVID-19 patients on ICU. This retrospective, single-center case series included 12 patients with critical courses of COVID-19 requiring treatment at ICU, who developed a severe encephalopathy (leading to clinical presentation of hyperand/or hypoactive delirium [2]) of at least 1 week without satisfactory response to neuroleptic drugs and/or even sedatives. These patients were treated with 2 g/kg IVIg over 3–5 days as off-label, individual medical treatment. The dosage of IVIg was chosen pragmatically according to established therapeutic regimens in other neurological autoimmune-mediated diseases. Other causes of encephalopathy such as increased blood levels of sedative medication, intoxication, metabolic changes (abnormal electrolyte concentrations, hyperuricemia, hepatic encephalopathy, hypoor hyperglycemia), Shufan Huo and Caroline Ferse have contributed equally.


Dear Sirs,
Coronavirus disease 2019 (COVID-19) patients on intensive care units (ICU) frequently present with acute encephalopathy that appears to be distinct from other ICU-related encephalopathies regarding higher incidence, longer duration, and increased severity including autonomous dysregulation and non-satisfactory response to neuroleptic drugs [1]. According to the updated nomenclature of delirium and acute encephalopathy, we use the term acute encephalopathy to describe a rapidly developing pathobiological brain process, expressed clinically as delirium, subsyndromal delirium or coma with partly additional neurological findings such as extrapyramidal signs or seizures [2]. This type of acute encephalopathy is associated with delayed recovery, weaning failure, prolonged ICU or hospital stay, or even impaired clinical outcome.
First reports found positive responses of COVID-19-associated encephalopathy to immunotherapy [3][4][5] that supported the hypothesis of a possible inflammatory pathomechanism [6]. However, this encephalopathy might still be misjudged by intensivists as poorly treatable with limited prognosis, risking premature withdrawal of ICU therapy or even end-of-life decisions in affected patients. Therefore, our case series demonstrates a promising and rapid effect of intravenous immunoglobulins (IVIg) on otherwise treatment-refractory acute encephalopathy in COVID-19 patients on ICU.
This retrospective, single-center case series included 12 patients with critical courses of COVID-19 requiring treatment at ICU, who developed a severe encephalopathy (leading to clinical presentation of hyper-and/or hypoactive delirium [2]) of at least 1 week without satisfactory response to neuroleptic drugs and/or even sedatives. These patients were treated with 2 g/kg IVIg over 3-5 days as off-label, individual medical treatment. The dosage of IVIg was chosen pragmatically according to established therapeutic regimens in other neurological autoimmune-mediated diseases.
Other causes of encephalopathy such as increased blood levels of sedative medication, intoxication, metabolic changes (abnormal electrolyte concentrations, hyperuricemia, hepatic encephalopathy, hypo-or hyperglycemia), sepsis with fever, hypothermia, shock or hypoxia were excluded. All patients received treatment with 6 mg dexamethasone for at least 10 days according to the RECOVERY study protocol [7].
Clinical neurological outcome was continuously evaluated by a neurologist and reported immediately before initiation and after termination of IVIg therapy and at discharge. Outcomes were assessed by Confusion Assessment Method for ICU (CAM-ICU), Richmond Agitation-Sedation Scale (RASS), Glasgow Coma Scale (GCS), Glasgow Outcome Scale (GOS) and modified Rankin Scale (mRS). Standardized scores were primarily ascertained by the treating neurologist. In case of missing data, scores were obtained from the daily routine assessment by the ICU nurses.
Cerebral CT or MRI showed none or only unspecific findings, but no abnormalities explaining the observed encephalopathy (Table 3). CSF was taken in 11 patients. In accordance with a recently published study about CSF findings in COVID-19 [9], eight of our patients showed blood brain barrier (BBB) dysfunction and all yielded normal cell counts and negative PCR for common pathogens including SARS-CoV-2. Furthermore, nine patients displayed either lowtiter antineuronal antibodies in serum (Myelin, CASPR2, NMDAR, Yo), or IgG binding of unknown specificity in indirect immunofluorescence of blood and CSF on unfixed murine brain sections, or both (Table 3). Increased neurofilament light-chain values in serum and CSF of all investigated patients (measured in n = 11 of 12) reflected relevant neuronal degeneration or damage.
This case series demonstrates a therapeutic effect of IVIg in treatment-refractory COVID-19-associated acute Table 1 Clinical presentation and duration of the disease Clinical features (pulmonary superinfection, invasive ventilation, proning, vvECMO, hepatic failure, RRT, sepsis, catecholamine therapy) are listed as "+" if they occurred at any time during the ICU stay. The term "delirium" is used in this manuscript to describe the clinical presentation of acute encephalopathy [2]. Before IVIg treatment, other sources of encephalopathy such as sepsis or hepatic failure were excluded at the time of clinical presentation of delirium, see exclusion criteria. For patients #10 and #12, the total duration of hospital stay could not be determined due to missing information about previous treatments in other hospitals. While 11 patients had at least one known cardiovascular risk factor, patient #4, who presented with known myasthenia gravis, did not. Patient #9 additionally suffered from stage II pulmonary sarcoidosis. Overall, most patients were severely affected by multiple complications (e.g., sepsis in 11, need for invasive ventilation in 11, renal failure with need of replacement therapy in nine, vvECMO in two patients)    All findings were measured after occurrence of acute encephalopathy and prior to IVIg administration except IL-6 levels, which were determined every second day throughout the ICU stay. Cerebral imaging only showed nonspecific pathologies including small ischemic strokes or intracerebral bleedings with no clinical correlation. Such imaging alterations are frequently seen in COVID-19 patients due to their higher risk of cerebral vasculopathy, especially in patients treated with vvECMO-therapy. But also activation of the coagulation system in COVID-19 patients predisposes them to thrombotic events of the brain and other organs. Patient #4 had a blood contamination in lumbar puncture with an increased CSF cell count of 7/µl and 1000 erythrocytes/µl.
In all other patients CSF cell count and cytology were normal (< 5/µl, lymphocytes). Part of the CSF samples of patient #10 coagulated due to blood contamination, which is why some laboratory information is missing Oligoclonal bands are reported as follows: type 1: Normal CSF, type 2: Oligoclonal IgG restricted to CSF, type 3: Oligoclonal IgG in CSF with additional identical bands in CSF and serum encephalopathy. The pathophysiology of this entity remains speculative, but IVIg response points towards an immunemediated mechanism, possibly succeeding COVID-19-induced cytokine release syndrome with BBB dysfunction and macrophage immigration or microglia activation, well in line with a neuroinflammatory hypothesis of COVID-19-associated acute encephalopathy [10]. The high frequency of intrathecal antineuronal antibodies detected by indirect immunofluorescence is in line with previous publications [8,11] and might be a surrogate marker for autoimmunemediated mechanisms, but whether they reflect specific or unspecific binding against CNS target epitopes causing acute encephalopathy currently remains open; especially since similar findings can be detected in asymptomatic persons. Immune-regulatory effects of IVIg are pleiotropic and involve Fc-receptor binding on macrophages and microglia, inflammation suppression including cytokines and chemokines, and transformation of activated microglia into a protective phenotype leading to reduction of neuronal cell death [12].
To date, one report described positive effects of IVIg on COVID-19-associated acute encephalopathy in five patients, but the therapeutic regimen overlapped with Tocilizumab and standardized methodology was lacking [13].
In our well-characterized cohort using standardized scores documenting responders and non-responders, natural remission coinciding the suspected IVIg effects cannot be excluded, but the long preceding interval without progress and the rapid improvement after IVIg initiation suggest a causal relationship. Due to the retrospective nature of our report and the individual treatment attempt as ultima ratio therapy, a control group without IVIg treatment is lacking.
Unresponsiveness in three cases remains unexplained and might indicate variability in pathophysiological mechanisms of encephalopathy. Interestingly, IVIg non-responders presented very high NfL levels in serum and CSF that might also reflect a more intense neuronal damage leading to a more severe encephalopathy than in responders. Moreover, considering the fatal sepsis development in non-responders, the neurological improvement after IVIg therapy might have been masked by general disease severity with multi-organ failure. Of note, patient #1 started to improve within 1 day after beginning of IVIg treatment, which could be a coincidence. However, a more impressive and, thus, clearly definable improvement was seen 3-4 days after treatment of IVIg, which is why we tend to attribute the clinical change to our therapy.
In conclusion, IVIg are a promising immunotherapy for severe treatment-refractory COVID-19-associated acute encephalopathy. Further prospective controlled studies are required to validate safety and efficacy, monitor long-term outcome, and explore the mechanisms of the therapeutic IVIg effect.
Author contributions: All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by SH, CF, CF and FS. The first draft of the manuscript was written by SH and CF and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Data availability Anonymized data will be shared upon request from any qualified investigator.

Conflicts of interest
The authors have no competing interests to declare that are relevant to the content of this article.
Ethics approval All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study was approved by the Bioethics Committee of the Medical University of A Charité-Universitätsmedizin Berlin (EA4/187/021).

Consent to publish
All patients or their legal guardians have consented to the submission of the case report to the journal.
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