- Clinical science
Locked-in syndrome (LIS) is a rare condition caused by bilateral damage to the ventral pons, most often due to a stroke. LIS is characterized by quadriplegia and bulbar palsy, caused by the interruption of the corticospinal and corticobulbar tracts in the pons. The only remaining voluntary muscle movements include vertical eye movement and blinking. Consciousness, awareness, cognition, and sensation are preserved. Diagnosis of pontine damage is made on a CT or MRI of the brain. Preserved cognition is diagnosed via EEG and neuropsychological testing. Management in most patients includes tracheostomy, mechanical ventilation, placement of a feeding tube, and physiotherapy. Patients learn to communicate through blinking and/or eye movements and the help of computer programs/speech synthesizers. Some patients may recover a certain degree of motor control, speech, and swallowing ability.
- Ventral pontine damage/injury
Severe peripheral nervous system diseases (rare)
Locked-in syndrome is typically preceded by a loss of consciousness and subsequent coma lasting for days or weeks. The following symptoms are detected on regaining consciousness:
Paralysis of voluntary muscles
- Paralysis of all 4 limbs and torso (quadriplegia) → spasticity, ↑ deep tendon reflexes, positive bilateral
- Bulbar palsy: inability to speak; (anarthria) or swallow (dysphagia)
- Respiratory abnormalities
Preservation of the following functions
- Normal consciousness, language comprehension, cognition, and ability to make decisions
- Vertical eye movements and voluntary blinking
- Cutaneous sensation
Patients with LIS can only communicate by blinking and vertical eye movements!
- CT/MRI of the brain: : indicated in all patients to identify the underlying cause
- Indicated in all patients to rule out brain death
- Used to measure visual/auditory evoked potentials → nearly normal EEG in LIS
- Lumbar puncture: indicated if an infectious etiology or is suspected
- Performed once the patient is stable to assess cognition
- Patients communicate with eye movements or blinking in response to the test questions → normal or near-normal cognition
Demonstration of preserved cognition, vertical eye movements, and blinking in a quadriplegic, anarthric patient is diagnostic of LIS!
The differential diagnoses listed here are not exhaustive.
- In acute phase
- Supportive therapy (airway, breathing, circulation)
- Treat the underlying, often life-threatening, disorder (see “Etiology” for causes)
- In the rehabilitative phase
- Respiration: most patients require tracheostomy and mechanical ventilation
- Feeding: initially feeding tube; possibly gastrostomy
- Physiotherapy: passive stretching exercises; skeletal muscle relaxants and/or botulinum toxin for spasticity; frequent position change to avoid pressure sores
- Speech: eye-gaze sensor-controlled computer communication programs, computer/internet use; use of speech synthesizers; eyelid blinking to communicate yes/no