Locked-in syndrome

Overview

Locked-in syndrome (LIS) is a rare neurological condition in which a person is fully conscious and cognitively aware but is unable to move or speak due to complete paralysis of nearly all voluntary muscles. The only movements typically preserved are vertical eye movements and blinking. Despite profound physical limitations, individuals with LIS can hear, think, and feel pain, emotion, and sensation, making the condition particularly distressing. The syndrome most commonly results from damage to the brainstem, specifically the pons, which disrupts motor control without affecting consciousness.

Causes

Locked-in syndrome is usually caused by damage to the ventral pons in the brainstem, which contains nerve pathways responsible for transmitting motor signals from the brain to the spinal cord. Common causes include:

• Stroke – particularly a basilar artery thrombosis leading to brainstem infarction (most common cause)

• Traumatic brain injury – resulting in brainstem compression or damage

• Tumors – that press on or infiltrate the brainstem

• Demyelinating diseases – such as multiple sclerosis

• Infections – such as encephalitis or brain abscess affecting the brainstem

• Central pontine myelinolysis – often related to rapid correction of low sodium levels

Symptoms

Symptoms of locked-in syndrome develop suddenly and are often dramatic. Key features include:

• Complete paralysis of voluntary muscles – affecting limbs, trunk, face, and speech

• Preserved vertical eye movements and blinking – typically the only means of communication

• Intact consciousness and cognitive function – the individual is fully aware of their environment

• Normal sleep-wake cycles

• Preserved hearing, vision, and sensation

Patients with LIS are often initially misdiagnosed as being in a coma or vegetative state, particularly in the acute phase following injury or stroke.

Diagnosis

Diagnosing locked-in syndrome requires careful neurological assessment and imaging to confirm preserved consciousness and brain function despite paralysis. Diagnostic steps include:

• Neurological examination – observing responses to stimuli and assessing eye movements

• MRI or CT scan – to identify damage in the brainstem, especially the pons

• EEG (electroencephalogram) – to confirm wakeful brain activity

• Evoked potentials – to assess sensory pathways and brain response

• Communication trials – using eye blinks or coded eye movements to verify awareness

Treatment

There is no cure for locked-in syndrome, and treatment focuses on supportive care, rehabilitation, and improving quality of life. Management includes:

• Intensive care support – including mechanical ventilation if respiratory muscles are paralyzed

• Nutritional support – via feeding tubes if swallowing is impaired

• Physical and occupational therapy – to prevent complications like contractures and pressure sores

• Communication aids – such as eye-tracking devices, letter boards, or speech-generating computers

• Psychological support – for both patient and family to cope with the emotional impact

• Treatment of the underlying cause – such as anticoagulation for stroke or treatment of infection

Prognosis

The prognosis for locked-in syndrome is generally poor, particularly when caused by massive brainstem stroke. Many individuals remain in a near-complete state of paralysis for life. However, some patients may regain limited movement or communication abilities over time, especially with early rehabilitation and assistive technology. Cognitive function usually remains intact, allowing patients to participate in decision-making if communication is established. Lifespan varies depending on the cause and quality of medical care, and while recovery is rare, a small number of individuals have achieved partial independence with support.