Locked-in syndrome
Locked-in syndrome (LIS) is a neurological condition characterized by full consciousness and awareness in individuals who experience almost complete paralysis, typically confined to limited eye movement. This condition arises from damage to the brain stem, particularly the pons, often due to traumatic injury, stroke, disease, or medication overdose. Patients may be erroneously diagnosed as being in a persistent vegetative state, complicating the identification of LIS. There are three classifications of LIS: incomplete, classic, and total locked-in syndrome, each varying in the degree of voluntary muscle control remaining. Diagnosis can be challenging, with some cases taking months or even years to confirm. Although there is no definitive treatment or cure for LIS, advancements in technology have introduced methods to facilitate communication for patients, such as systems that interpret eye movements. In rare instances, some patients may experience spontaneous recovery, but the potential for recovery largely depends on the underlying cause of the brain damage. Understanding LIS is crucial for providing appropriate care and support for affected individuals and their families.
On this Page
Subject Terms
Locked-in syndrome
Locked-in syndrome (LIS) is a medical condition in which an individual is fully conscious and aware but is almost completely paralyzed. In most cases, the patient is only able to move the voluntary muscles of the eyes. Locked-in syndrome is caused by damage to a specific part of the brain stem, typically as a result of traumatic injury, disease, medication overdose, or stroke. Patients with locked-in syndrome are often mistakenly believed to be in a persistent vegetative state. There is no known treatment or cure, though in very rare cases a patient has spontaneously recovered.
Overview
The term locked-in syndrome was first coined by neurologist Fred Plum, and it first appeared in print in his and fellow neurologist Jerome B. Posner’s Diagnosis of Stupor and Coma (1966). However, the syndrome had been known for some time before; the earliest known reference can be found in Alexandre Dumas’s novel The Count of Monte Cristo (1844–45), in which Monsieur Noirtier de Villefort is described as being paralyzed and unable to speak, communicating only through eye movements.
LIS is most often caused by damage to the lower front area of the pons, formally known as the pons Varolii, which is the part of the brain stem that connects the cerebral cortex to the medulla oblongata. Among other tasks, the pons helps coordinate communication between different parts of the brain as well as between the brain and the spinal cord, and it plays a role in enabling motor functions. Damage to this area disrupts the motor pathways controlling other parts of the body, while consciousness and awareness remain unimpaired.
LIS can be difficult to diagnose. In many cases in which the damage is caused by traumatic injury, the patient may initially be comatose, making early diagnosis impossible. Even once the patient regains consciousness, he or she may be incorrectly diagnosed as being in a minimally conscious state, a persistent vegetative state, or even a prolonged comatose state. According to a study published in 2002, the average time to diagnose LIS was two and a half months from the inciting injury, and some cases took several years to properly diagnose.
Experts have identified three basic types of LIS: incomplete locked-in syndrome, classic locked-in syndrome, and total or complete locked-in syndrome. Patients with classic LIS display the characteristics described by Plum and Posner: quadriplegia, the inability to speak, and the ability to move the eyes vertically, though not from side to side. With incomplete LIS, the patient also possesses some additional limited voluntary muscle movement, such as the ability to move his or her facial muscles. At the other end of the spectrum are patients with total LIS, who cannot even move their eyes vertically and are thus completely unable to communicate. Cases of total LIS are the most difficult to properly diagnose.
LIS is not curable, though there have been rare cases of recovery, either partial or complete. Chances for recovery depend on what caused the brain damage and whether the damage is reversible. Most treatment for LIS focuses on enabling communication. Computer technology exists by which patients may spell out words via eye movement or other minor voluntary movement, and there has been some promising research into direct brain-computer interfaces, which would enable even patients with total LIS to communicate.
Bibliography
Bruno, M., et al. “Locked-In: Don’t Judge a Book by Its Cover.” Journal of Neurology, Neurosurgery, and Psychiatry 79.1 (2008): 2. Print.
Cardwell, Michael S. “Locked-In Syndrome.” Texas Medicine 109.2 (2013): n. pag. Web. 25 Sept. 2013.
Graham-Rowe, Duncan. “Turning Thoughts into Words.” MIT Technology Review. MIT Technology Review, 23 Sept. 2010. Web. 26 Sept. 2013.
Laureys, Steven, et al. “The Locked-In Syndrome: What Is It Like to Be Conscious but Paralyzed and Voiceless?” Progress in Brain Research 150 (2005): 495–511. Print.
León-Carrión, José, et al. “The Locked-In Syndrome: A Syndrome Looking for a Therapy.” Brain Injury 16.7 (2002): 571–82. Print.
Posner, Jerome B., et al. Plum and Posner’s Diagnosis of Stupor and Coma. 4th ed. New York: Oxford UP, 2007. Print.
Schnakers, Caroline, et al. “Cognitive Function in the Locked-In Syndrome.” Journal of Neurology 255.3 (2008): 323–30. Print.
Schnakers, Caroline, et al. “Detecting Consciousness in a Total Locked-In Syndrome: An Active Event-Related Paradigm.” Neurocase 15.4 (2009): 271–77. Print.
Wilson, Barbara A., et al. “A Case Study of Locked-In Syndrome: Psychological and Personal Perspectives.” Brain Injury 25.5 (2011): 526–38. Print.