Locked-in syndrome

Clinical priority: A person who appears unresponsive may be awake but unable to produce a visible motor response. Establishing a dependable communication signal and repeatedly assessing awareness are urgent parts of care.

Locked-in syndrome (LiS) is an acquired neurological state in which severe paralysis and loss of speech prevent ordinary movement and communication while wakefulness and awareness are preserved. The classic form most often follows injury to the ventral pons and retains vertical eye movement or blinking. Cognitive function can be difficult to measure and is not necessarily uniform, particularly when lesions extend beyond the pons. Schnetzer et al., 2023; Voity et al., 2024

Quick reference

Precise population incidence and prevalence are not established. LiS can occur at different ages and should not be described as having an equal sex distribution without supporting population data.

Clinical forms and causes

The commonly used classification distinguishes:

• Classic LiS: quadriplegia and anarthria with preserved consciousness and vertical eye movement or blinking.
• Incomplete LiS: the classic features plus another voluntary movement, which may be small but functionally important.
• Complete or total LiS: no observable voluntary movement. Specialized, repeated assessment is needed because behavioral communication may be absent.

The usual anatomical basis is bilateral interruption of corticospinal and corticobulbar pathways in the ventral pons. Pontine infarction or hemorrhage is most common. Trauma, demyelination, tumor, infection, and other brainstem injury can produce LiS or a similar clinical state. Severe peripheral neuromuscular disorders and medication effects can mimic profound motor disconnection and belong in the differential diagnosis. Smith and Delargy, 2005; Schnetzer et al., 2023

Locked-in syndrome is not ordinarily a genetic syndrome. Genetic testing is not a routine diagnostic test for an acquired pontine locked-in state; it may be appropriate only when the history suggests a separate inherited neurological disorder.

Recognition and diagnosis

Diagnosis combines neurological examination with investigation of the cause. A single normal EEG does not confirm intact cognition, and absent limb movement does not establish absent awareness.

Important steps include:

1. Look repeatedly for a reproducible response using vertical and horizontal gaze, blink, facial movement, head movement, finger or toe movement, or another residual action.
2. Establish a clear yes, no, and no response / uncertain code. Verify it with questions whose answers are already known before using it for clinical decisions.
3. Assess arousal, hearing, vision, language comprehension, attention, fatigue, medication effects, and motor consistency over more than one session when possible.
4. Use MRI or CT and vascular imaging to identify pontine or other causal lesions. EEG, evoked potentials, electromyography, nerve-conduction studies, or advanced imaging may answer specific differential questions, but no single test replaces the clinical assessment.
5. Distinguish LiS from coma, unresponsive wakefulness syndrome, minimally conscious state, akinetic mutism, severe aphasia or apraxia, and profound neuromuscular paralysis.

Family or staff may notice meaningful eye responses before they are recognized during a brief examination. Record the response method prominently and make it available across settings. Smith and Delargy, 2005

Communication and AAC

Functional communication is a primary rehabilitation goal, not an optional later step. Begin with the least demanding reliable method and keep a backup available.

Assessment

An SLP, occupational therapist, assistive-technology specialist, and the person should evaluate:

• the most reliable voluntary movement and its range, speed, endurance, and consistency;
• visual acuity, visual field, diplopia, gaze range, fixation, and calibration tolerance;
• hearing, language, literacy, cognition, alertness, and fatigue;
• positioning, respiratory status, secretion management, and environmental noise or glare; and
• communication priorities, languages, preferred topics, privacy, and settings.

Do not limit access assessment to eye gaze. In a rehabilitation series, individualized systems used small movements of the thumb, chin, head, or other body parts as well as the eyes. Söderholm et al., 2001

Low-tech communication

• Start with an agreed yes/no/uncertain signal.
• Use partner-assisted scanning of choices, words, or a frequency-ordered alphabet when direct selection is not reliable.
• Consider an eye-transfer board when gaze direction is consistent and the communication partner can align it accurately.
• Provide pain, positioning, suction, urgent-care, and personal-needs vocabulary immediately.
• Confirm important messages by repeating them back and asking the person to verify.

Electronic access

• Eye tracking may support typing, speech output, messaging, and environmental control when gaze and calibration are reliable.
• A switch can be placed for any repeatable movement and used with scanning software.
• Direct touch, mouse, head tracking, or speech control is relevant only when that movement or voice is actually available in incomplete LiS.
• Adjust dwell time, target size, layout, prediction, and rest periods to reduce errors and fatigue.
• Brain-computer interfaces remain an emerging option, especially for complete LiS; access, training burden, reliability, and clinical availability vary. They should not replace a usable lower-technology method. Voity et al., 2024

Communication-partner practice

• Address the person directly and allow enough response time.
• Say the available choices before scanning them.
• Do not guess after an ambiguous response; return to the last confirmed point.
• Offer a way to correct, cancel, request a break, and indicate that the message is not listed.
• Preserve privacy and obtain consent through the person's established communication method.

Medical and rehabilitation management

Acute treatment is directed at the cause, such as time-sensitive stroke care when eligible. Support may include airway and ventilation management, nutrition and individualized swallowing assessment, prevention of pressure injury and venous thrombosis, bladder and bowel care, infection prevention, eye care, pain and spasticity management, and psychological support.

Early interdisciplinary rehabilitation should address communication, positioning, mobility, contracture prevention, respiratory function, self-care, environmental control, and family or caregiver training. Swallowing and respiratory abilities vary; feeding tubes and long-term ventilation are not universal requirements. Recovery also varies with cause, lesion extent, complications, and time. Even a small recovered movement can materially change independent access and should trigger AAC reassessment. Smith and Delargy, 2005; Schnetzer et al., 2023

Autonomy, mental health, and quality of life

Screen for pain, anxiety, depression, sleep problems, and emotional lability using an accessible response method. Clinicians and families should not infer a person's quality of life from motor disability alone. Longitudinal and cross-sectional studies show substantial individual variation and demonstrate that some people with chronic LiS report satisfactory well-being. Include the person directly in care, research, and life-sustaining-treatment decisions whenever decision-making capacity can be established. Bruno et al., 2011; Rousseau et al., 2015

References

1. Schnetzer L, et al. Locked-in syndrome revisited. Therapeutic Advances in Neurological Disorders. 2023;16. PMID 37006459 · Free full text · DOI 10.1177/17562864231160873
2. Voity K, et al. Update on how to approach a patient with locked-in syndrome and their communication ability. Brain Sciences. 2024;14:92. PMID 38248307 · Free full text · DOI 10.3390/brainsci14010092
3. Smith E, Delargy M. Locked-in syndrome. BMJ. 2005;330:406–409. Free full text · DOI 10.1136/bmj.330.7488.406
4. Söderholm S, Meinander M, Alaranta H. Augmentative and alternative communication methods in locked-in syndrome. Journal of Rehabilitation Medicine. 2001;33:235–239. Full text · DOI 10.1080/165019701750419644
5. Bruno M-A, et al. A survey on self-assessed well-being in a cohort of chronic locked-in syndrome patients. BMJ Open. 2011;1:e000039. PMID 22021735 · Free full text · DOI 10.1136/bmjopen-2010-000039
6. Rousseau M-C, et al. Quality of life in patients with locked-in syndrome: evolution over a 6-year period. Orphanet Journal of Rare Diseases. 2015;10:88. PMID 26187655 · Free full text · DOI 10.1186/s13023-015-0304-z
7. ICD-10-CM G83.5 — Locked-in state. Code descriptor; confirm against the current official CMS ICD-10-CM files for the care year.