Locked-in Syndrome : Causes, Symptoms, Treatment

Locked-in syndrome is a neurological condition that can lead to complete paralysis of all the voluntary muscles except the eyes. It occurs due to damage to the brain stem, typically in the pons.⁽¹⁾

It involves:⁽²⁾

• Complete paralysis of the voluntary muscles
• Impairment in the function of the lower cranial nerves
• Whole body sensory loss
• Loss of horizontal eye movement

People with locked-in syndrome may be conscious, alert, or awake, and may have regular sleep and wake cycle but would not be able to speak and move.

The brain stem connects the cerebrum to the spinal cord and cerebellum. It is known to consist of the midbrain, pons, and medulla. It is responsible for vital body functions such as breathing and consciousness. Damage to the brain stem which may occur due to stroke or tumors may lead to locked-in syndrome.

Locked-in syndrome may happen due to damage to the central area of the pons.⁽¹⁾ The anterior pons is a horseshoe-shaped mass of fibers that connect the cerebrum to the medulla. Damage to the tissue may disrupt the motor fibers that may run from the brain to the spinal cord. It may also occur in the area of the pons that is important for speaking and facial muscle control.

The common causes of lesions in the pons include:

• Stroke can lead to a lack of blood flow and bleeding. This can lead to the locked-in syndrome.
• Traumatic brain injuries from the blunt and penetrating trauma
• Tumors growing in the anterior pons or midbrain
• Spread of infection from any other part of the body to the brain stem
• Demyelination, which is the damage to the outer covering of nerve fibers

Locked-in syndrome is more common in males than females and occurs mostly at the age of 30-50 years.

Also, those at risk of stroke or bleeding in the brain are also at risk of developing the locked-in syndrome. These people include those with hypertension, atherosclerosis, and diabetes.

People with locked-in syndrome would initially be in a coma and slowly regain consciousness. They may remain paralyzed and unable to speak. They would be bedridden and dependent only on caregivers.

Following are the activities a person with locked-in syndrome would not be able to do voluntarily or consciously:

• Limb movement
• Moving the face lower
• Breathing deeper than usual
• Chewing or swallowing
• Speaking
• Moving eyes left to right

Other symptoms may include:

• Sudden starting or stopping of breathing
• Vertigo
• Dizziness
• Poor muscle control
• Locked-in syndrome may be of 3 forms or types depending on the number of motor abilities preserved.
• Classical form in which there is total immobility. A few abilities such as blinking or vertical eye movement may be there.
• Incomplete form, which is similar to classical form with a few voluntary movements other than eye movement.
• Total immobility form in which there may be a complete loss of motor functions making a person unable to express his thoughts and needs.

The doctor reviews a person’s health history to identify the cause of the condition. A clinical evaluation is done that consist of a neurological exam to assess cranial nerve function.

There are a few tests that may be performed to rule out other possible health conditions. These include:

• CT scan and MRI
• Cerebrospinal fluid analysis
• Electrophysiologic studies
• Blood test involving sodium levels

The main goal of the treatment is to reverse the underlying cause of the locked-in syndrome i.e., stroke. The doctor ensures that the person has an adequate supply of blood and air.

The person may require a tracheostomy for breathing and a gastrostomy for feeding and drinking.

Speech therapy, physical therapy and rehabilitation therapy may be needed for established communication, maintaining voluntary respiratory muscle function, and small voluntary movements.

Locked-in syndrome may be difficult to diagnose as its symptoms may be similar to coma, catatonia, brain death, persistent vegetative state, and akinetic mutism.

People with a high risk of stroke are also at a high risk of suffering from locked-in syndrome. Most of the cases are not preventable but a person should speak with a doctor to lower the risk of its occurrence.