Locked-in syndrome is a rare neurological disorder wherein the voluntary muscles of the body are paralyzed, with the exception of the muscles that control the movement of the eyes. The following HealthHearty write-up provides information on this condition.
|Locked-in syndrome is a rare medical condition that might be observed in around 1% of people affected by a brainstem stroke. Quadriplegia (inability to move both the arms and legs due to paralysis) and anarthria (inability to speak) are characteristic signs of this condition.|
The American Congress of Rehabilitation Medicine describes locked-in syndrome (LIS) as a medical condition that is characterized by preserved awareness, relatively intact cognitive functions, and the ability to communicate while being paralyzed and voiceless. LIS must not be confused with persistent vegetative state.
A condition signifying extreme motor impairment, LIS has been categorized into Complete/Total LIS, Classic LIS, and Incomplete LIS. Though quadriplegia and anarthria are observed in people affected by Classic and Total LIS, communication through vertical eye movements and blinking is only possible in case of Classic LIS. In case of Incomplete LIS, the patient may recover some voluntary movements along with the eye movements.
Also referred to as pseudocoma, LIS is often associated with strokes affecting the brainstem, which is the posterior section of the brain connecting the cerebrum with the spinal cord. It comprises the medulla oblongata, pons, and midbrain.
➟ Though LIS is quite rare, a traumatic injury or non-traumatic brain damage, that leads to an ischemic or hemorrhagic lesion of the pons, is likely to cause LIS. Ventral pontine lesions could occur in the event of obstruction of blood supply due to the presence of a tumor or damage to the vertebral or basilar artery.
➟ Central pontine myelinolysis, which is a neurological disease characterized by severe damage to the myelin sheath of nerve cells in the pons, could also be a contributing factor.
The interruption of the corticospinal tract by the lesion gives rise to quadriplegia, whereas the injury to the corticobulbar tract paralyzes the muscles that are involved in speech and vocalization, thereby leading to anarthria. The patient is able to blink and open the eyes as the supranuclear motor pathways are intact.
In 1995, the American Congress of Rehabilitation Medicine described five criteria for defining this syndrome. These include:
➟ Sustained eyes opening and preserved vertical eye movement
➟ Preserved higher cortical functions
➟ Aphonia or severe hypophonia
➟ Primary mode of communication that uses vertical eye movements or blinking
People affected by LIS are fully conscious and aware of their surroundings. They have normal sleep-wake patterns. When a person is comatose, he is said to be in a state of unresponsiveness, with no awareness of self, as well as his surroundings. Affected individuals are unconscious, and lie with their eyes closed.
An individual is said to be in a vegetative state, if he remains unaware of self and surroundings, even after coming out of coma. This could be a transitional period, wherein partial or total recovery might take place. The vegetative state is referred to as persistent, if it lasts more than a month. Persistent vegetative state is characterized by the loss of cognitive function, however, non-cognitive function and normal sleep patterns are retained.
The patient is said to be in a permanent vegetative state, if signs of awareness are not observed one year after a traumatic brain injury or three months after a non-traumatic brain damage occurring due to the lack of oxygen. Unlike the vegetative state where there is loss of cognitive function, people with LIS are able to perceive and think.
Prognosis and life expectancy may depend on various factors. Life expectancy increases if this condition is diagnosed early, and appropriate medical care is provided. Good neurological prognosis is linked with the recovery of horizontal eye movements before the first four weeks. The 10-year and 20-year survival rates for patients who have medically stabilized in the locked-in state for more than a year are 83% and 40% respectively. Though there is less likelihood of the patient recovering significant motor functions, the use of assistive devices can improve the patient’s ability to communicate.
Communication is possible in some cases wherein sufficient voluntary eye movement has been observed. In such cases, a communication partner can read out or point to the letters on a letter board. The patient chooses the letter by blinking when the right letter is recited or pointed to on an alphabet board. Messages can be spelled out in this manner. It is also possible to get ‘yes’ and ‘no’ answers from patients by using an eye-tracking system that uses a digital camera with a laptop for monitoring the change in the size of pupils. Functional neuromuscular stimulation is another technique wherein muscle groups are stimulated with electrodes.
Access to eye-tracking systems, speech-generating devices, or other assistive devices that help in communication can certainly improve the quality of life of people affected by locked-in syndrome. If treatment enables the patient to move even one finger, he can operate assistive devices, which can help him communicate. Hopefully, ongoing research on brain-computer interfacing might help the patients communicate more easily, and even become mobile in future.
Disclaimer: This HealthHearty article is for informative purposes only, and should not be replaced for the advice of a medical professional.