Anti-LGI1 encephalitis

Page most recently updated 7 September 2026

This page focuses on the reported psychiatric associations, which may be the initial presenting manifestation, and on other clinical features that may assist the psychiatrist or primary care physician in identifying the underlying diagnosis, considered through the lenses of the diagnostic lenses framework.

Anti-LGI1 encephalitis is an autoimmune encephalitis with multisystemic involvement.

It can present with psychiatric features such as acute confusion, behavioural change, agitation, anxiety, mood symptoms, psychosis, sleep disturbance, and cognitive impairment (particularly prominent short-term memory impairment), which may precede recognition of the underlying neurological disorder.

Other characteristic features include faciobrachial dystonic seizures (brief, frequent dystonic movements affecting the face and arm, often preceding other neurological features), limbic encephalitis with rapidly progressive anterograde amnesia, seizures, altered mental status, sleep disturbance, and hyponatremia.

From a multisystemic lens perspective, clinical features in other body systems include (but are not limited to):

  • Cardiovascular: autonomic dysfunction may occur, including fluctuations in heart rate and blood pressure.

  • Renal/electrolytes: hyponatremia is a characteristic and common finding, often related to syndrome of inappropriate antidiuretic hormone secretion (SIADH).

  • Endocrine: association with malignancy, particularly thymoma in a minority of cases, although most cases are non-paraneoplastic.

Early diagnosis is important to enable prompt immunotherapy, reduce the risk of persistent cognitive impairment, seizures, and functional decline, guide investigation for associated malignancy when appropriate, and improve neurological recovery, prognosis, and quality of life.

Selected references and further reading — Multisystemic lens

Cardinal RN, Bullmore ET. The diagnosis of psychosis. Cambridge: Cambridge University Press; 2011.

Sachdev PS, Keshavan MS, editors. Secondary schizophrenia. Cambridge: Cambridge University Press; 2010.

Levenson JL, editor. The American Psychiatric Association Publishing textbook of psychosomatic medicine and consultation-liaison psychiatry. 3rd ed. Washington (DC): American Psychiatric Association Publishing; 2019.

Stern TA, Beach SR, Smith FA, Freudenreich O, Vranceau AM, Fava M, editors. Massachusetts General Hospital handbook of general hospital psychiatry. 8th ed. Philadelphia: Elsevier; 2025.

Arciniegas DB, Yudofsky SC, Hales RE, editors. The American Psychiatric Association Publishing textbook of neuropsychiatry and clinical neurosciences. 6th ed. Washington (DC): American Psychiatric Association Publishing; 2018.

Agrawal N, Faruqui R, Bodani M, editors. Oxford textbook of neuropsychiatry. Oxford: Oxford University Press; 2020.

Boland R, Verduin M, editors. Kaplan and Sadock's comprehensive textbook of psychiatry. 11th ed. Philadelphia: Wolters Kluwer; 2024.

Loscalzo J, Fauci AS, Kasper DL, Hauser SL, Longo DL, Jameson JL, editors. Harrison's principles of internal medicine. 22nd ed. New York: McGraw Hill; 2025.