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Anti-LGI1 Autoimmune Encephalitis

Autoimmune limbic encephalitis with faciobrachial dystonic seizures

Written by: Saygı Hospital Health Guide Editorial Board
Last updated:

This content has been compiled by the Saygı Hospital Health Guide Editorial Board and is periodically reviewed by a specialist physician.

References (5)

This content is for informational purposes only and does not constitute medical advice. You can book an appointment at our Nöroloji department. Book Appointment →

What is Anti-LGI1 Autoimmune Encephalitis?

Anti-LGI1 encephalitis is caused by IgG4-predominant antibodies against LGI1, a secreted neuronal protein that interacts with voltage-gated potassium channels.

It is the second most common autoimmune encephalitis after anti-NMDA receptor encephalitis, predominantly affecting older adults (median age 60).

Men are affected more often than women (2:1 ratio).

Faciobrachial dystonic seizures (FBDS) are pathognomonic — brief (less than 3 seconds), frequent (multiple per day) hemifacial and ipsilateral arm dystonic movements that often precede limbic encephalitis by weeks to months.

Tumor association is uncommon (less than 10 percent), unlike many other paraneoplastic encephalitides; thymoma is the most common when present.

Symptoms

Faciobrachial dystonic seizures: brief, frequent unilateral facial grimace and arm posturing
Subacute memory impairment and amnesia (anterograde memory most affected)
Behavioral changes: confusion, agitation, hallucinations, depression
Other seizure types as illness progresses: focal-aware, focal-impaired-awareness, generalized
Hyponatremia (60 percent of patients) due to syndrome of inappropriate antidiuretic hormone (SIADH)
Sleep disturbances, REM sleep behavior disorder
Autonomic dysfunction: cardiac arrhythmia, blood pressure fluctuation
Cognitive decline progressing to dementia if untreated

Risk Factors

Older age (peak 60–70)
Male sex (2:1 male predominance)
HLA-DRB1*07:01 association (strong genetic association)
Possible association with malignancy (thymoma, small cell lung cancer) in minority of cases
No clear environmental triggers identified

When to See a Doctor?

If you experience any of the following symptoms, seek medical attention promptly:

  • New-onset frequent brief unilateral facial and arm spasms (FBDS)
  • Subacute memory impairment in older adult
  • New psychiatric symptoms with confusion or seizures
  • Persistent or worsening hyponatremia of unclear cause with neurologic symptoms
  • Sleep disturbances with cognitive changes
  • Refractory seizures with concurrent cognitive decline

Treatment Methods

01
Diagnosis: CSF analysis (mild lymphocytic pleocytosis or normal), MRI (medial temporal lobe T2/FLAIR hyperintensity, basal ganglia changes), EEG (temporal slowing, FBDS may show subtle abnormalities)
02
Confirmatory: anti-LGI1 antibodies in serum and CSF (cell-based assay is gold standard, more sensitive than older voltage-gated potassium channel testing)
03
Tumor screen: chest imaging (CT, MRI, PET) to evaluate for thymoma; whole-body PET if other malignancy suspected
04
First-line immunotherapy: high-dose IV methylprednisolone (1 g daily for 5 days) plus IVIG (2 g/kg over 2–5 days) or plasma exchange
05
Continued oral corticosteroid taper over months
06
Second-line: rituximab, cyclophosphamide if inadequate response to first-line therapy or relapse
07
Antiseizure medications: carbamazepine and other sodium channel blockers often work but may not fully control FBDS without immunotherapy
08
Treat hyponatremia with fluid restriction, salt tablets, demeclocycline or tolvaptan as needed
09
Tumor treatment if thymoma or other malignancy identified
10
Prognosis: 80 percent achieve substantial recovery; cognitive deficits may persist; relapse rate 25–35 percent within 2 years
11
Long-term follow-up with neurology for relapse monitoring and cognitive rehabilitation

Which Department to Visit?

You can visit our Nöroloji department for these complaints. Our specialist physicians will create the most suitable treatment plan for you.

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Health Disclaimer: The information on this page is prepared for general informational purposes only. It does not replace medical diagnosis and treatment. Please consult your physician for your complaints. Saygı Hospital does not accept responsibility for actions taken based on the information on this page.