Locked-in syndrome is a state of wakefulness and awareness with quadriplegia and paralysis of the lower cranial nerves, resulting in inability to show facial expression, move, speak, or communicate, except by coded eye movements.
Locked-in syndrome typically results from a stroke (pontine hemorrhage or infarct) that causes quadriplegia and disrupts and damages the lower cranial nerves and the centers that control horizontal gaze. Other disorders that result in severe widespread motor paralysis (eg, Guillain-Barré syndrome) and cancers that involve the posterior fossa and the pons are less common causes.
Locked-in syndrome can also result from infection, tumors, toxins, trauma, arteriovenous malformations, and opioid use.
Symptoms and Signs of Locked-In Syndrome
Patients with locked-in syndrome have intact cognitive function and are awake, with eye opening and normal sleep-wake cycles. They can hear and see. However, they cannot move their lower face, chew, swallow, speak, breathe, move their limbs, or move their eyes laterally. Vertical eye movement is possible; patients can open and close their eyes or blink a specific number of times to answer questions.
Diagnosis of Locked-In Syndrome
Clinical evaluation
Diagnosis of locked-in syndrome is primarily clinical. Because patients lack the motor responses (eg, withdrawal from painful stimuli) usually used to measure responsiveness, they may be mistakenly thought to be unconscious. Thus, all patients who cannot move should have their comprehension tested by requesting eye blinking or vertical eye movements.
As in vegetative state, neuroimaging is indicated to rule out treatable disorders. Brain imaging with CT or MRI is done and helps identify the pontine abnormality. Positron emission tomography (PET), single-photon emission computed tomography (SPECT), functional MRI, or evoked responses may be done to further assess cerebral function if the diagnosis is in doubt.
In patients with locked-in syndrome, electroencephalography (EEG) shows normal sleep-wake patterns.
Prognosis for Locked-In Syndrome
Prognosis for patients with locked-in syndrome depends on the cause and the subsequent level of support provided. For example, locked-in syndrome due to transient ischemia or a small stroke in the vertebrobasilar artery distribution may resolve completely. When the cause (eg, Guillain-Barré syndrome) is partly reversible, recovery can occur over months but is seldom complete.
Favorable prognostic features include
Early recovery of lateral eye movements
Early recovery of evoked potentials in response to magnetic stimulation of the motor cortex
Irreversible or progressive disorders (eg, cancers that involve the posterior fossa and the pons) are usually fatal.
Treatment of Locked-In Syndrome
Supportive care
Communication training
Supportive care is the mainstay of treatment for patients with locked-in syndrome and should include the following:
Preventing systemic complications due to immobilization (eg, pneumonia, urinary tract infection, thromboembolic disease)
Providing good nutrition
Providing physical therapy to prevent limb contractures
There is no specific treatment for locked-in syndrome.
Because cognitive function is intact and communication is possible, patients should make their own health care decisions.
Speech therapists may help establish a communication code using eye blinks or movements.
Some patients with locked-in syndrome communicate with each other via the Internet using a computer terminal controlled by eye movements and other means. Newly developed brain-computer interfaces may help restore the ability of patients with locked-in syndrome to communicate (1).
Treatment reference
1. Milekovic T, Sarma AA, Bacher D, et al: Stable long-term BCI-enabled communication in ALS and locked-in syndrome using LFP signals. J Neurophysiol 120 (1):343–360, 2018.
