Landau-Kleffner syndrome

Landau-Kleffner syndrome (LKS), also called acquired epileptic aphasia, is a childhood epilepsy-aphasia syndrome. A child who had acquired language loses the ability to understand spoken language and may also lose expressive language. The current International League Against Epilepsy classification describes LKS as the language-predominant subtype of epileptic encephalopathy with spike-wave activation in sleep (EE-SWAS).1

Recognizing the pattern

• Language regression may be gradual or abrupt. Auditory verbal agnosia can make a child seem deaf because speech no longer carries meaning.
• Hearing testing may be normal even when spoken-language understanding is severely affected.
• Sleep activates the epileptiform EEG abnormalities; an awake EEG alone may miss the characteristic pattern.
• Clinical seizures can occur, but they are not required. Some children with LKS have no recognized seizures.1
• Attention, behavior, learning, and participation may change alongside the language loss, but the profile varies.

New loss of language or other developmental skills needs prompt pediatric, neurologic, hearing, and speech-language evaluation. A prolonged seizure, repeated seizures without recovery, injury, or breathing difficulty requires emergency care.

Evaluation

Diagnosis is based on the developmental and language history together with EEG findings, particularly during non-REM sleep. Assessment commonly includes:

• detailed documentation of skills before, during, and after regression;
• receptive, expressive, pragmatic, speech, literacy, and nonverbal cognitive assessment;
• formal audiology to distinguish hearing loss from auditory-language impairment;
• awake and sleep EEG interpreted by a clinician experienced in pediatric epilepsy;
• brain MRI and other testing when the history or examination suggests another cause.

Some people across the epilepsy-aphasia spectrum have a pathogenic GRIN2A variant, but LKS is not synonymous with GRIN2A-related disorder and many individuals have no identified genetic cause. Genetics evaluation should be selected from the individual and family history.2

Treatment and follow-up

Care should be coordinated by pediatric epilepsy and communication specialists. Clinicians may use antiseizure medication, corticosteroids or other immune-directed treatment, and rarely epilepsy surgery in selected treatment-resistant cases. Evidence is limited: a Cochrane review found no randomized-trial evidence that could support or refute particular drug treatments for LKS or related sleep-activated epileptic encephalopathy.3 A drug, dose, diet, or operation should not be chosen from a general condition page.

Track language, learning, seizures, sleep, behavior, and EEG over time. Improvement in visible seizures does not by itself show that the sleep EEG or language disorder has resolved. Language outcomes vary, and support may remain necessary even after epileptiform activity improves.1

Communication and education

Communication support should start while medical evaluation and treatment are underway. Spoken-language loss does not establish loss of intelligence, intent, literacy, or the ability to learn through visual modes.

An individualized plan may include:

• written language, pictures, drawing, gesture, sign, visual schedules, and speech-generating AAC;
• reduced spoken-language load and visual access to instructions and classroom content;
• assessment of reading and spelling as possible communication strengths;
• vocabulary for pain, seizures, emotions, school participation, and social connection;
• partner training and a consistent way to communicate across home, school, and health care.

Do not prescribe touch, switches, symbols, or eye gaze from the diagnosis. Match language representation and access to observed ability and reassess as skills change. AAC has no cognitive or age prerequisite and can support language without preventing speech recovery.4 For evaluation, trials, funding, and implementation, use the AAC device acquisition guide.

Coding note

Do not treat ICD-10-CM G40.803 as an LKS-specific code. FY2026 ICD-10-CM defines it as “other epilepsy, intractable, with status epilepticus.” The appropriate epilepsy code depends on the documented seizure syndrome, intractability, and status-epilepticus history.5

Sources

1. Specchio et al. ILAE classification and definition of epilepsy syndromes with onset in childhood — current syndrome terminology and diagnostic framework (2022; PMID 35503717).
2. GeneReviews: GRIN2A-Related Disorders — epilepsy-aphasia spectrum, genetic interpretation, clinical seizures, and language features.
3. Cochrane: Pharmacological treatment for CSWS and Landau-Kleffner syndrome — treatment-evidence limitations (2020).
4. American Speech-Language-Hearing Association: Augmentative and Alternative Communication — multimodal, individualized, no-prerequisite AAC guidance.
5. Centers for Medicare & Medicaid Services: FY2026 ICD-10-CM definitions — G40.803 descriptor.

Review boundary

This guide does not diagnose LKS, interpret an EEG, or select epilepsy treatment. Active regression and seizure concerns require direct review by pediatric neurology, audiology, and speech-language clinicians; education and AAC plans should be based on direct assessment.