Overview

Locked-in Syndrome (LiS) is a rare but serious condition. In LIS, you remain fully aware and awake, but you cannot move any of your voluntary muscles except for blinking or moving your eyes. This most often happens when the pons, a part of the brain stem that connects the brain to the body, is damaged–commonly from a stroke. However, other rare causes, such as tumours or infections in the brainstem, can also lead to LiS.¹ Understanding these rare causes is important because it affects how the condition is diagnosed, managed, and treated, and it influences patient outcomes. 

Understanding locked-in syndrome and brainstem anatomy

Locked-in Syndrome often begins with a period of coma. Over time, a person may start to regain awareness, recognise words, wake and sleep normally, blink and move their eyes, but is still unable to move the rest of their body.¹

Doctors recognise three main forms:¹

• Classic form of LiS – this is where you cannot move your body and muscles at all, apart from your eyes, but you remain fully aware
• An incomplete form of LiS – similar to the classic form, but you may have slight movement in one or more body parts.
• Total immobility form of LiS – this is where you cannot move any of your muscles or body, not even in your eyes, but you remain aware. This is sometimes mistaken for a coma or ‘vegetative state’ until tests such as an electroencephalogram (EEG)  confirm brain activity

Signs and symptoms of locked-in syndrome

People with LiS typically cannot:

• Chew or Swallow
• Move facial muscles
• Speak or move their body  

However, they can usually:

• Blink or move their eyes up and down (depending on the form of LiS))

• Hear
• Sleep and wake 
• Understand conversations 
• Think and reason clearly

What causes locked-in syndrome?

To understand LiS, we need to look at the brainstem–the part of the brain that connects the brain to the spinal cord. The brainstem has three main parts: the midbrain, the pons, and the medulla. This controls basic body  functions like breathing, heartbeat, and movement.^1,2

The pons, found in the middle of the brainstem, play a key role in controlling movement. It contains pathways that send signals from the brain to the body.. If the pons is damaged, these signals can't get through, leading to paralysis and loss of speech.¹

The most common cause of damage to your pons is from a stroke, of which there are two types:

Ischemic stroke-when a blood clot forms in one of your blood vessels in your brain, which cuts off blood supply and oxygen to the brain.

Haemorrhagic stroke-when an artery starts to bleed into your brain.¹

However, other causes include:¹

• Infection
• Tumours
• Trauma or head injury
• Demyelination, which is where you lose the protective layer that surrounds your nerve cells
• Inflammation of the nerves in the brain (polymyositis)³
• Substance abuse/misuse
• Conditions such as Guillain-Barre syndrome or motor neuron disease (ALS)

These less common causes can also lead to damage in the brainstem, including the pons, resulting in LiS.

Tumours in the brainstem: A rare cause of locked-in syndrome

Locked-in syndrome is usually caused by stroke, but in rare cases, a brain tumour in the brainstem can lead to the same result.  

These tumours can be: 

• Intrinsic, meaning they grow inside the brainstem
• Extrinsic, meaning they grow from nearby tissues and press into the brainstem.

The types of brainstem tumours linked to LiS include:

• Gliomas and astrocytomas – tumours that grow  from the brain’s own support cells²
• Diffuse Intrinsic Pontine Gliomas (DIPG) – a rare aggressive tumour of the pons, usually seen in children, that grows in the pons⁴
• Focal gliomas – slower-growing tumours that develop in one location of the brainstem (but less often in the pons)⁴

These tumours can cause LiS when they press or damage important nerve pathways in the pons. The corticospinal and corticobulbar tracts carry movement signals from your brain to your muscles.¹ When these are affected, you may lose the ability to move or speak, but still remain aware. Swelling from the tumour, known as oedema, can increase pressure in the brainstem and worsen symptoms.

Although rare, several medical reports have confirmed that brainstem tumours, especially pontine gliomas, have caused LiS in some people. ^5,6 Unfortunately, LiS caused by a tumour often has poorer outcomes than stroke-related cases, especially when the tumour is too aggressive or inoperable. Recovery depends heavily on the type of tumour, its location, how early it is detected and how it can be treated.

Diagnosing a tumour-related LiS can be difficult because it may look like a stroke or even a neurological disease like multiple sclerosis. MRI scans are the best tool for spotting tumours in the brainstem. Recognising signs such as headaches and numbness or weakness in the face quickly is vital to begin surgery or treatment and give patients the best possible chance before a situation like LiS can occur.^1,2

Infections that can lead to locked-in syndrome

While very rare, certain infections in the brainstem can cause locked-in syndrome by damaging the nerves that control movement and speech.

Bacterial infections

• Tuberculosis (especially when it spreads to the brain – called tubercular meningitis)⁷
• Listeria (a foodborne infection that can spread to the brain in vulnerable people)⁸
• Bacterial meningitis (inflammation of the membranes surrounding the brain and spinal cord)⁹

Viral infections

• Herpes simplex (HSV)– which can cause inflammation in the brainstem¹⁰
• Enteroviruses have been found to cause inflammation in the brainstem, especially in cases of brainstem encephalitis.¹¹

When these infections reach the brainstem, the body’s immune system can trigger inflammation, swelling, tissue damage, or even abscesses (pockets of pus). These changes can damage the brain’s motor pathways in the brainstem, especially the corticospinal and corticobulbar tracts, which control movement and communication to the muscles. If these pathways are damaged, a person can be fully conscious but unable to move or speak.

Although rare, there have been documented cases of infections being linked to LiS. For example, a child with an enterovirus started declining in consciousness and ended up with LiS. Tuberculosis, especially in the form of tubercular meningitis, was found to be a cause of locked-in syndrome in a child. These infections often occur in individuals with specific risk factors such as a compromised immune system or delayed access to care.^7,11

Diagnosing infections in the brainstem

Diagnosis often involves

• MRI or CT scans to look for swelling, inflammation, or abscesses
• Lumbar puncture to test the fluid around the brain and detect signs of infection
• Blood tests or PCR (genetic) tests to identify specific viruses or bacteria^1,9

It’s crucial to recognise early symptoms of serious infections such as fever, nausea, headache, or confusion and get urgent medical help. Early treatment can prevent the infection from spreading to the brainstem and leading to serious outcomes like locked-in syndrome.

Treatment and recovery in locked-in syndrome

Locked-in Syndrome (LiS) is a serious condition, and unfortunately, there is no cure. However, in some cases, partial recovery is possible– especially if LiS is not caused by stroke or infection. A small number of people are even able to regain movement and return to daily activities, though this is rare. When LiS is caused by tumours in the brainstem, recovery is usually much harder. This is because brainstem tumours are often:

• Located in areas that are difficult to operate in
• Aggressive in how they grow
• Less responsive to treatment

Treating the underlying cause

Treatment for LiS always starts by trying to treat the underlying problem:

• Tumours: may be treated with surgery, radiotherapy, or chemotherapy, depending on the size, location, and type of tumour
• Infections: are usually treated with antibiotics (for bacterial infections), antivirals, and sometimes steroids to reduce swelling

Supporting the patient’s quality of life

Even when full recovery isn’t possible, supportive care helps patients stay healthy and communicate, including:

• A feeding tube (G-tube) for nutrition and hydration
• A breathing tube (tracheostomy) if the person cannot breathe properly on their own
• Physiotherapy to help prevent muscle stiffness or bed sores
• Speech and communication therapy, so patients can use eye movements or blinking to express their thoughts

These treatments can help prevent complications, improve quality of life, and support the person’s independence in whatever ways possible.

Summary

Locked-in Syndrome (LiS) is a rare and serious neurological condition where a person is fully paralysed except for eye movements and is still conscious. It is usually caused by stroke-related damage to the brainstem, but tumours and infections can also lead to LiS by damaging important nerve pathways. Tumours like gliomas or astrocytomas and infections like meningitis or tuberculosis may trigger LiS, although these causes are rare. Prognosis varies depending on the cause and if it is treatable such as in some cases of infection, some may partially or fully recover. In other cases such as in cases of LiS caused by tumour, patients usually do not recover.

FAQ’s

What is locked-in syndrome, and how is it different from a coma?

Locked-in Syndrome (LiS) is a rare condition where someone is completely aware and awake, but unable to move or speak, except for limited eye movements (usually blinking or moving the eyes up and down).

Unlike a coma, where a person is unconscious, people with LiS can hear, think, and understand everything — they just can’t respond in the usual ways.

Can brain tumours really cause locked-in syndrome?

Yes, although it’s rare, tumours in the brainstem — especially those affecting an area called the pons — can lead to LiS. Tumours such as gliomas or astrocytomas can press on or damage the nerves that control movement, leading to the full-body paralysis seen in LiS. These cases tend to be harder to treat than LiS caused by stroke.

How do infections lead to locked-in syndrome?

Certain infections, like meningitis, tuberculosis, or viral encephalitis, can spread to the brainstem and cause inflammation or swelling. This can damage the nerve pathways responsible for movement. In rare cases, this damage can result in LiS. Quick treatment of infections is important to avoid severe complications like this.

Can people with locked-in syndrome recover?

Recovery depends on the cause of LiS. Some people with LiS caused by stroke or infection may regain some movement or communication abilities, especially with therapy. However, when LiS is caused by a tumour, especially an aggressive one, recovery is less likely. Each case is different, and early diagnosis can make a big difference.

How do people with LiS communicate?

Since most people with LiS can still move their eyes, doctors and families use eye-tracking systems, blinking codes, or specialised communication devices. With the right support, many people with LiS are able to express their thoughts, make choices, and stay connected to loved ones.