Locked-in Syndrome,  Unresponsive Wakefulness Syndrome, and Brain Imaging

Overview

• These conditions involve severe neurological impairment but differ in awareness and motor function.

Locked-in Syndrome

• Characteristics:
  • GCS score (3-8), low scores can be similar to coma and misleading, as low motor impairment scores hide patient’s awareness.
  • Patient is awake, aware, and fully conscious but completely paralyzed.
  • No voluntary movement or speech; communication sometimes possible through eye movements.
  • Often brainstem functions (breathing, heartbeat) remain intact.
  • Presence of brainstem reflexes (e.g., pupil, corneal, gag, doll’s eye, oculocephalic) and cerebral brain activity can help distinguish Locked-In Syndrome from coma.
• Cause:
  • Damage to brainstem (often the pons).
  • Cerebral cortex preserved.
• Case example:
  • Jean-Dominique Beauby, a columnist, was paralyzed from stroke affecting the brainstem, resulting in Locked-In syndrome, but communicated via blinking.
  • Using eye movements and brain-imaging, he communicated complex ideas and even authored a book, “The Diving Bell and the Buttefly”.
• Assessment via Imaging:
  • EEG and functional MRI can detect brain activity.
  • Patients showing awake and responsive states can be distinguished from coma or unresponsive wakefulness syndrome states.
• Research:
  • Imaging brain activity during imagined tasks allows a patient to answer yes/no questions.
  • During fMRI, patent is asked to :
    • Imagine walking in a room to “say yes”: activates spatial/motor areas (answer “yes”).
    • Imagine playing tennis to “say no”: activates motor areas (answer “no”).
  • Helps facilitate communication with patient
  • Helps detect patient’s awareness and emotional responses.

 Unresponsive Wakefulness Syndrome (UWS)

• Features:
  • Appears awake, eyes are open, but no awareness.
  • No responses to verbal or painful stimuli.
  • Unresponsive Wakefulness Syndrome describes patients who are awake but consciousness is absent.
  • Requires long-term care; some patients recover, others do not.
  • Formerly known as Vegetative State
• Causes
  • Usually results from severe trauma or cerebral hypoxia (lack of oxygen):
    • Brain tissue, especially cerebral hemispheres, is extensively damaged.
    • The brainstem remains intact:
      • Autonomic functions such as heart rate, breathing, blood pressure are maintained.
    • The reticular activating system (RAS) remains functional, allowing wakefulness.

Imaging Techniques and Findings

• MRI:
  • Shows lack of activity in cerebral hemispheres.
• EEG:
  • Shows absence of cortical activity.
• PET scans:
  • Show reduced or absent activity in higher brain centers.

• Brain – reduced activity:
  • Indicates extensive damage to thinking and feeling regions.
  • Brain no longer perceives or interprets sensory information.

Clinical Features

• Wakefulness:
  • Eyes are open, often tracking movements.
  • Can follow reflexive movements.
• Lack of awareness:
  • No response to questions or commands.
  • No appropriate responses despite apparent wakefulness.
• Reflexes:
  • Pupillary, corneal, gag, and oculocephalic reflexes are usually intact.
• Behavior:
  • Not able to perceive or respond meaningfully.
  • No cognitive or emotional processing.

Functional Status

• Patients can breathe independently and maintain blood pressure.
• May be bedridden and require caregiving.
• Some may recover; about 50% show improvement within one month.
• Others remain permanently in UWS.

Duration and Prognosis

• Can persist months to years.
• Temporary (less than 1 month): Often improves.
• Persistent or long-term:
  • Likely to remain for months or years.
• Recovery chances decrease over time.

Glasgow Coma Scale and UWS

• Scores can range from 3–9:
• Usually lower end of the scale, indicating more severe impairment.

Brain Imaging and Function Summary

• PET scans:
  • Show activity levels.
  • Normal: High activity in brain at rest.
  • Locked-in: Activity preserved in cerebral cortex (awake, conscious).
  • Unresponsive Wakefulness Syndrome: Activity significantly decreased.
  • Minimally conscious: Small, impaired activity.

Summary Table

Practical Applications

• Imaging helps differentiate between coma, locked-in, and UWS states.
• Communication possible via brain-controlled interfaces in locked-in syndrome.
• Understanding brain function guides treatment and prognosis.