Seronegative autoimmune encephalitis

Arulmary^1*, Sofiya Chandra Prasanna²

¹Nursing Incharge, Kauvery Hospital, Alwarpet, Chennai, Tamil Nadu

²Clinical Instructor, Kauvery Hospital, Alwarpet, Chennai, Tamil Nadu

*Correspondence

Introduction

Autoimmune encephalitis is an inflammatory brain disorder caused by an immune-mediated attack on neuronal tissue. It can present with neurological, cognitive, behavioural and psychiatric manifestations. Early recognition and timely initiation of immunotherapy are important for improving neurological outcomes.

Seronegative autoimmune encephalitis refers to cases in which clinical features and supporting investigations suggest autoimmune encephalitis despite negative antibody testing. Therefore, a negative antibody panel does not exclude the diagnosis.

Case Presentation

Patient name: Ms. Y

Age/Sex: 27 years / Female

Presenting complaints:

Incoherent speech
Increased tinnitus
Lack of sleep for the past few months
Complete insomnia for 2 days
Sudden behavioural changes
Difficulty walking without support.

History of Present Illness

The patient presented with incoherent speech and increased tinnitus, associated with insomnia for several days. Despite receiving clonazepam, there was no significant improvement in sleep. Subsequently, the patient developed sudden behavioural changes.

The behavioural changes included agitation, irritability, and refusal of medication, irrelevant talking and threatening behaviour towards the attender. The patient also demonstrated reduced cooperation with the healthcare team.

Clinical Examination

General Examination

The patient was conscious but disoriented and had incoherent speech.

Neurological examination revealed:

Vertical and horizontal nystagmus
Repetitive eye movements
Tinnitus
Ataxic gait
Positive finger-nose test indicating ataxia
Myoclonic jerks while walking
Difficulty ambulating without support

Vital Signs

Temperature	98°F
Pulse	92/min
Respiratory rate	22/min
Blood pressure	130/72 mmHg
SpO₂	99% on room air

Psychological and Behavioural Symptoms

The patient exhibited

Agitation
Irritability
Refusal of medication
Threatening behaviour towards the attender
Irrelevant talking
Poor cooperation
Episodes of inappropriate behaviour

The patient also expressed statements suggesting a lack of insight into the condition and displayed self-harm-related verbal responses.

Investigations

Blood Investigations

The following investigations were performed:

Complete blood count

C-reactive protein
ESR
Serum levetiracetam level
Oxcarbazepine metabolite level
Coagulation profile
Urine porphyrin

CSF Analysis

CSF analysis showed:
Mild lymphocytic pleocytosis
Elevated protein
Viral panel findings as documented

Autoimmune Panel

The autoimmune evaluation included:

NMDA receptor antibody
LGI1 antibody
CASPR2 antibody

The antibody testing was negative, supporting the consideration of seronegative autoimmune encephalitis in the presence of compatible clinical features and investigations.

Radiological Findings

MRI Brain

MRI brain demonstrated:

Hyper intensity involving the bilateral temporal lobes
Findings suggestive of encephalitis
The MRI study of the individual accompanying patient was documented as normal.

EEG

EEG demonstrated:

Diffuse slowing
Intermittent epileptiform discharges

PET-CT

PET-CT demonstrated:
Hypometabolism in the frontal region
Cerebellar hypometabolism
Occipital hypometabolism

Differential Diagnosis

The following differential diagnoses were considered:

Herpes simplex encephalitis
Metabolic encephalopathy
Psychiatric disorders
Toxic encephalopathy
Paraneoplastic encephalitis

Final Diagnosis

Based on the clinical presentation, neurological findings, MRI and EEG findings, exclusion of infectious causes, and response to immunotherapy, the final diagnosis was:

Seronegative Autoimmune Encephalitis with associated:

Seizure disorder
Hypothyroidism

Medical Management

The patient was managed with:

IV methylprednisolone: 1 g/day for 5 days
IVIG therapy
Antiepileptic medications
Supportive care

Medications Documented

Drug Name	Dose	Frequency
Tab. Lacosamide	100 mg	OD
Tab. Brivaracetam	450 mg	BD
Inj. Solu-Medrol	500 mg IV	OD
Inj. Clexane	0.4 mg SC	OD
Tab. Quetiapine	25 mg	OD
Inj. Noctophil	800 mg	BD
IVIG	Total 3 days	Approximately 30 mg/day as documented

The medication doses and schedules above are transcribed from the handwritten case notes and should be verified against the patient’s medication chart before formal publication.

Nursing Management

The major nursing interventions included:

Neurological Monitoring

Regular assessment of level of consciousness and orientation
Monitoring neurological status
Assessment for changes in behaviour and cognition
Monitoring for worsening neurological symptoms.

Seizure Precautions

Maintain a safe environment
Keep necessary emergency equipment readily available
Observe for seizure activity
Administer antiepileptic medications as prescribed

Fall Prevention

Assist the patient during ambulation
Provide support while walking
Maintain a safe environment
Monitor closely because of ataxia and myoclonic jerks

Medication Administration

Administer prescribed immunotherapy and antiepileptic medications
Monitor for therapeutic response and adverse effects
Ensure medication compliance

Family Education

Explain the patient’s condition and treatment plan
Educate the family regarding seizure and fall precautions
Encourage cooperation with the treatment team
Provide emotional support to the patient and family

Patient Outcome

Following treatment, the patient demonstrated:

Gradual improvement in cognition
No further seizures
Improved orientation
Improvement in neurological status
Transition from IV treatment to oral steroids

Planned neuro-rehabilitation follow-up.

Discussion

Seronegative autoimmune encephalitis can be challenging to diagnose because specific neuronal antibodies may be absent despite a clinical presentation strongly suggestive of an autoimmune process.

This case highlights the importance of maintaining a high clinical suspicion when patients present with rapidly evolving behavioural, psychiatric, cognitive and neurological manifestations. Important learning points from the case include:

Negative antibody testing does not exclude autoimmune encephalitis. Early diagnosis is crucial for initiating appropriate treatment. Prompt immunotherapy can improve prognosis.

A multidisciplinary approach is important for managing neurological, psychiatric, behavioural and functional complications.

Seizure and fall precautions are essential during the acute phase.

Conclusion

Seronegative autoimmune encephalitis is a challenging neurological condition that requires careful clinical assessment and a high index of suspicion. Diagnosis should be based on the overall clinical presentation and supportive investigations rather than antibody results alone. In this case, the patient’s neurological and behavioural manifestations, MRI and EEG findings, exclusion of other causes, and response to immunotherapy supported the diagnosis. Early treatment and comprehensive nursing care contributed to gradual neurological and cognitive recovery. Timely intervention, appropriate immunotherapy, neurological monitoring, seizure prevention, fall prevention and multidisciplinary management are essential for achieving favourable outcomes.

Seronegative autoimmune encephalitis

Seronegative autoimmune encephalitis

Arulmary1*, Sofiya Chandra Prasanna2

Nightingale Journals

Arulmary^1*, Sofiya Chandra Prasanna²