What is locked-in syndrome?

Locked-In Syndrome: Definition and Clinical Features

Locked-in syndrome (LIS) is a devastating neurological condition characterized by complete paralysis of all voluntary muscles except vertical eye movements and blinking, with preserved consciousness and cognitive function. 1, 2

Core Clinical Features

The defining characteristics of LIS include:

• Quadriplegia (paralysis of all four limbs) with inability to move voluntary muscles 2, 3
• Anarthria (inability to speak) and lower cranial nerve paralysis 4
• Preserved consciousness and cognition - patients remain fully aware and alert 1, 2, 5
• Preserved vertical eye movements and upper eyelid movements - typically the only voluntary motor function remaining 2, 4
• Loss of horizontal gaze in classical presentations 3

Anatomical Basis and Etiology

LIS results from damage to specific brainstem structures:

• Ventral pons and caudal midbrain are the primary anatomical sites of injury 3
• Basilar artery occlusion causing ischemic stroke is the most common cause 3, 5
• Acute ventral pontine lesions are the typical pathological substrate 5

Clinical Subtypes

LIS is classified into three distinct subtypes based on severity 3:

• Classical LIS: Complete quadriplegia, loss of horizontal gaze, aphasia, but preserved vertical eye movements and blinking 3
• Incomplete (Partial) LIS: Some residual motor function remains beyond eye movements 3
• Complete (Total) LIS: The most severe form where patients cannot even blink or move eyes vertically, rendering them completely unable to communicate 3

Diagnostic Challenges and Critical Pitfalls

The diagnosis of LIS is frequently delayed, taking an average of 2.5 months, with some cases taking 4-6 years to recognize. 5 This represents a catastrophic failure in clinical recognition.

Key diagnostic considerations:

• More than half the time, family members - not physicians - first recognize that the patient is conscious 5
• Patients superficially resemble those in vegetative state or akinetic mutism, leading to misdiagnosis 5
• In acute LIS, eye movements may be inconsistent, very small, and easily exhausted, making communication assessment difficult 5
• Patients often remain comatose for days to weeks after the initial injury before awakening into the locked-in state 5

Differential Diagnosis

LIS must be distinguished from several conditions 6, 2:

• Vegetative state/coma: Unlike LIS, these patients lack consciousness (CPC category 4) 6
• Cognitive motor dissociation (CMD): Patients have impaired consciousness in addition to motor deficits 2
• Akinetic mutism: Characterized by lack of motivation to move or speak, rather than physical inability 2
• Locked-in plus syndrome: LIS with additional impairments of consciousness 2

Notably, the Cerebral Performance Categories classification system specifically mentions LIS as an example of severe cerebral disability (CPC 3), where patients "are paralyzed and can communicate only with their eyes" but retain at least limited cognition. 6

Communication and Rehabilitation

Establishing communication is the primary goal of rehabilitation and must begin immediately upon recognition of consciousness. 4

Communication strategies include:

• Yes/no eye-coded communication using vertical eye movements or blinking - used by 100% of chronic LIS patients 1
• Augmentative communication technology - used by 62% of patients 1
• Computer-based eye-controlled systems allowing environmental control, word processing with speech synthesis, and internet access 5

Recovery and Long-Term Outcomes

Contrary to the uniformly poor prognosis often assumed:

• 49% of chronic LIS patients recover some verbal language ability 1
• 73% recover some functional movements over time (mean 10 years post-injury) 1
• Life expectancy extends to several decades once medically stable 5
• Chronic LIS patients typically self-report meaningful quality of life, and requests for euthanasia are surprisingly infrequent 5

However, the overall prognosis remains guarded, with most patients remaining significantly disabled and requiring extensive long-term care. 3

Critical Management Principles

Medical professionals and caregivers consistently underestimate the quality of life and well-being reported by LIS patients themselves, leading to potentially harmful biases in care decisions. 2, 5

Essential management considerations:

• Only the medically stabilized, informed LIS patient is competent to consent to or refuse life-sustaining treatment - not family members or clinicians making assumptions 5
• Aggressive early interdisciplinary rehabilitation including physical therapy, communication system establishment, and psychological support is essential 2, 4
• Specific rehabilitation targets include blood pressure management, orthostatic tolerance, ventilatory support and decannulation, bowel/bladder management, and wheelchair positioning 4
• The autonomy and dignity of LIS patients must be prioritized over clinician assumptions about quality of life 2

Ethical Imperatives

Biased clinicians who assume poor quality of life may provide less aggressive medical treatment and inappropriately influence families toward withdrawal of care. 5 This represents a profound ethical violation, as LIS patients retain full cognitive capacity and personhood despite their physical limitations. 2, 5