Locked-in syndrome is a rare neurological disorder in which there is complete paralysis of all voluntary muscles except for the ones that control the movements of the eyes. Individuals with locked-in syndrome are conscious and awake, but have no ability to produce movements (outside of eye movement) or to speak (aphonia). Cognitive function is usually unaffected. Communication is possible through eye movements or blinking. Locked-in syndrome is caused by damaged to the pons, a part of the brainstem that contains nerve fibers that relay information to other areas of the brain.
Individuals with locked-in syndrome classically cannot consciously or voluntarily chew, swallow, breathe, speak, or produce any movements other than those involving the eyes or eyelids. In some cases, affected individuals can move their eyes up and down (vertically), but not side-to-side (horizontally). Affected individuals are bedridden and completely reliant on carers. Despite physical paralysis, cognitive function is unaffected.
Individuals with locked-in syndrome are fully alert and aware of their environment. They can hear, see and have preserved sleep-wake cycles. Affected individuals can communicate through purposeful movements of their eyes or blinking or both. They can comprehend people talking or reading to them.
Individuals with locked-in syndrome often initially are comatose before gradually regaining consciousness, but remain paralysed and unable to speak.
Locked-in syndrome is most often caused by damage to a specific part of the brainstem known as the pons. The pons contains important neuronal pathways between the cerebrum, spinal cord and cerebellum. In locked-in syndrome there is an interruption of all the motor fibers running from grey matter in the brain via the spinal cord to the body’s muscles and also damage to the centres in the brainstem important for facial control and speaking.
Damage to the pons most often results from tissue loss due to lack of blood flow (infarct) or bleeding (hemorrhage) – less frequently it can be caused by trauma. An infarct can be caused by several different conditions such as a blood clot (thrombosis) or stroke. Additional conditions that can cause locked-in syndrome include infection in certain portions of the brain, tumours, loss of the protective insulation (myelin) that surrounds nerve cells (myelinolysis), inflammation of the nerves (polymyositis), and certain disorders such as amyotrophic lateral sclerosis (ALS).
Locked-in syndrome is a rare neurological disorder that affects males and females in equal numbers.and can affect individuals of all ages including children, but most often is seen in adults more at risk for brain stroke and bleeding. Because cases of locked-in syndrome may go unrecognized or misdiagnosed, it is difficult to determine the actual number of individuals who have had the disorder in the general population.
Symptoms of the following disorders can be similar to those of locked-in syndrome. Comparisons may be useful for a differential diagnosis.
Locked-in syndrome is also called pseudo-coma because affected individuals are conscious but make little body movement – like unconscious “eyes-closed” coma patients or unconscious “eye-open” vegetative state patients.
A variety of conditions can cause symptoms or a clinical picture that is similar to locked-in syndrome. These disorders or conditions include Guillain-Barre syndrome, myasthenia gravis, poliomyelitis, polyneuritis or bilateral brainstem tumors. As said, locked-in syndrome can be mistaken for a vegetative state that may occur secondary to trauma or a variety of different conditions, especially if affected individuals have visual or hearing loss making the diagnosis more difficult.
Often affected individuals in the beginning may need an artificial aid for breathing and will have a tracheotomy (a tube going in the airway via a small hole in the throat).
Feeding and drinking will not be possible via the mouth (it may cause respiratory infection by running into the lungs rather than stomach) and hence will need to be assured via a small tube inserted in the stomach called a percutaneous entral gastrostomy (PEG).
Devices to aid in communication and other assistive technologies have proven beneficial as well as allowing individuals to become active members of society. Infrared eye tracking devices now permit affected individuals to use a computer with artificial voice, control their environment, surf on the internet and send email.
Recent studies and articles in the medical literature have noted that despite significant motor disability affected individuals can retain a good quality of life. In addition, quality of life is unrelated to the degree of physical impairment. With advances in care and assistive technologies, individuals with locked-in syndrome can become productive members of society.