Locked-in syndrome
Group of answer choices a) is associated with normal default mode network activation in resting-state functional MRI. b) causes a reduction of cerebral metabolism to about 40% of the normal value. c) is associated with occasional reaching for an object or following a command. d) is a disorder of consciousness because individuals do not show purposeful behavior.
The correct answer and explanation is:
The correct answer is b) causes a reduction of cerebral metabolism to about 40% of the normal value.
Explanation:
Locked-in syndrome is a neurological condition where patients are aware of their surroundings and conscious but cannot move or communicate due to complete paralysis of nearly all voluntary muscles in the body, except for the eyes. This syndrome typically results from damage to the brainstem, particularly the pons, which disrupts motor pathways responsible for voluntary movement.
The reduction in cerebral metabolism to about 40% of the normal value is a characteristic feature of locked-in syndrome. This decline occurs because the areas responsible for motor control are affected, but other areas of the brain, such as those involved in sensory processing and cognition, may remain relatively intact. In many cases, patients retain full cognitive function, meaning they are aware and conscious but unable to communicate or move due to the loss of motor control.
Option a is incorrect because locked-in syndrome is not associated with normal default mode network activation on resting-state functional MRI. The default mode network typically shows decreased activation during tasks that require attention and cognition, but in locked-in syndrome, the brain’s ability to initiate motor tasks is severely compromised.
Option c is misleading because individuals with locked-in syndrome do not typically show any purposeful movement like reaching for an object. The only voluntary movement that might remain in some cases is eye movement, particularly vertical eye movements or blinking.
Option d is also incorrect because locked-in syndrome does not involve a lack of purposeful behavior. Although patients cannot move or speak, they remain fully conscious and may attempt to communicate through eye movements, blinks, or other subtle gestures. Therefore, it is not classified as a disorder of consciousness.