Brainstem Strokes and LIS

Brainstem strokes are the most common cause of locked-in syndrome. Understanding how brainstem strokes occur, what they affect, and how they cause LIS can help you understand the next steps with your loved one’s care.

What the Brainstem Does (and Why Damage There Is So Dangerous)

The brainstem is a small structure at the base of the brain, but it does an outsized amount of work. It controls nearly all voluntary movement, meaning any movement you choose to make, like lifting your arm or turning your head. It also controls breathing, heart rate, and swallowing.

Because so much runs through this one narrow area, even a small stroke here can cause enormous damage. A stroke in the brainstem can cut off the body’s ability to move and respond, even while the person stays fully awake and aware.

Doctors divide the brainstem into three regions:

• The midbrain
• The pons
• The medulla

Our focus is on the pons, because it’s where the stroke that leads to locked-in syndrome most often happens.

Here’s why the pons is so important. Inside it, two very different systems sit right next to each other:

• Toward the front of the pons (doctors call this the “ventral” side) are the corticospinal tracts, which are bundles of nerve fibers that carry the brain’s movement signals down to the rest of the body.
• Toward the back of the pons (the “dorsal” side) sits the reticular activating system, which is the network responsible for wakefulness and consciousness.

The Basilar Artery and How Clots Form

The basilar artery is the main blood vessel that feeds the pons. Because the ventral pons and the body’s movement pathways depend almost entirely on this one artery, a blockage here can be devastating.

How the Blockage Happens

The most common cause of locked-in syndrome overall is a vascular problem (i.e., an issue with a blood vessel), which makes up at least 75% of all reported cases. The basilar artery specifically can be affected in a few ways:

• Thrombosis: A clot forms directly inside the artery, narrowing or blocking it.
• Dissection: A tear forms in the wall of the artery. Blood can get into the tear, which narrows the vessel or blocks blood flow.
• Hemorrhage: Instead of a blockage, the vessel bleeds, and blood collects around the brainstem, putting pressure on it.

People who develop a vascular basilar artery problem often already have risk factors that make their blood vessels vulnerable, including high blood pressure, atherosclerosis (hardening and narrowing of the arteries), and diabetes. In one large review of locked-in syndrome cases published in StatPearls, nearly a third of vascular cases involved a documented history of high blood pressure.

What Happens Once Blood Flow Is Cut Off

When the basilar artery is blocked, the front portion of the brain is starved of oxygen and begins to die. This is called an infarct. Importantly, the blockage typically spares the tegmentum, the back portion of the pons. This is the anatomical reason locked-in syndrome happens the way it does: the front of the pons, which carries the brain’s movement signals, is destroyed, while the back of the pons, which helps keep a person conscious, stays intact. The result is a person who is fully aware but unable to move.

Why Brainstem Strokes Are Often Missed

Most people know the acronym FAST: Face drooping, Arm weakness, Speech difficulty, Time to call 911. It works well for many strokes. But brainstem strokes often don’t fit this pattern at all. Instead, they can cause sudden dizziness, double vision, nausea, trouble swallowing, or a loss of balance.

These symptoms can look like something far less serious, such as vertigo or a migraine. Emergency doctors see many patients with dizziness and headache every day, and most of them are not having a stroke. That reality makes it easy for a true brainstem stroke to slip past, even in a careful emergency room.

Imaging adds another layer of difficulty. A CT scan is usually the first test ordered, and it’s good at detecting bleeding, but it’s less effective at picking up small brainstem strokes. An MRI is more sensitive, but it isn’t always available right away. If the first scan looks normal, a patient can be sent home, only to return hours later with symptoms that have gotten worse, and by then, the treatment window may have closed.

The Treatment Window: Why Timing Can Decide the Outcome

Doctors have a saying that captures the urgency of stroke care: time is brain. Every minute an ischemic stroke goes untreated, 19 million brain cells die, according to Stroke. For someone experiencing a brainstem stroke, those minutes can be the difference between walking out of the hospital and living with locked-in syndrome for the rest of their life.

Modern medicine has two main tools to reopen a blocked artery, and both are highly time-sensitive:

• Clot-busting medication (tPA): This drug can dissolve a clot and restore blood flow, but only if it’s given within three and a half hours from the moment symptoms start. Not every patient qualifies for it, but when they do, the results can be life-changing.
• Mechanical thrombectomy: In some cases, doctors thread a thin catheter into the blood vessel and physically remove the clot. This procedure works best within six hours of symptom onset, though it can still help select patients up to 24 hours later.

Both treatments depend on speed at every step. The patient has to get to the hospital quickly. The medical team has to recognize the stroke, order the right imaging, and act without delay.

There’s a separate, related guideline specifically for locked-in syndrome caused by a blocked vertebral or basilar artery: restoring blood flow, whether through an IV medication or a catheter-delivered treatment, should happen within 48 hours of symptom onset.

Any hesitation along the way, whether from the family, emergency responders, or hospital staff, can cost precious time that can’t be recovered.

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When the Window Closes: The Path to Locked-In Syndrome

When a basilar artery clot isn’t treated in time, the pons loses its blood supply and the tissue there dies. This is the direct path from a missed or delayed brainstem stroke to locked-in syndrome.

The damage follows a predictable pattern, based on which structures run through that part of the brainstem:

• The corticospinal tracts, which run through the ventral pons and carry the brain’s movement signals to the rest of the body, are destroyed. This causes paralysis of all four limbs.
• Nerve fibers controlling the face, throat, and voice box are also damaged, causing the inability to speak (anarthria).
• Because the reticular activating system and the nuclei controlling vertical eye movement sit farther back or higher up, in the midbrain, they’re usually spared. This is why consciousness, hearing, and vertical eye movement often remain intact.

The result is the defining picture of locked-in syndrome: a person who is completely aware, can hear and understand everything around them, and may still be able to move their eyes up and down or blink, but who cannot speak or move their body.

Locked-in syndrome isn’t one single, uniform condition. It has three recognized forms:

• Classical: total paralysis of the limbs and face, but vertical eye movement and blinking are preserved
• Incomplete: similar to classical, but with some remaining voluntary movement
• Total: complete paralysis, including the loss of vertical eye movement and blinking, meaning even these last remaining channels of communication are gone, even though the mind is still fully intact

How Negligence Can Allow a Brainstem Stroke to Cause LIS

Even with fast recognition and excellent care, not every brainstem stroke can be reversed. But when treatment is delayed because symptoms were dismissed, that delay deserves a closer look. Missed windows can happen in several ways:

• Dizziness or double vision mistaken for a migraine or inner-ear problem
• A normal CT scan treated as the final answer instead of following up with a more sensitive MRI
• A patient sent home only to return hours later with symptoms that have grown worse

Each of these moments represents time that can’t be recovered once it’s gone, and in some cases, that lost time is the difference between recovery and a lifetime with locked-in syndrome.

If your family is facing locked-in syndrome after a stroke, we review cases to help determine whether the outcome may have been preventable. There’s no upfront cost and no obligation to move forward—just a conversation to help you understand what happened and what your options may be.

Get Answers When You’re Ready

Brainstem strokes don’t always look like strokes, but recognizing them quickly and following up with the right imaging can mean the difference between recovery and locked-in syndrome. If your family has been affected, you don’t have to make sense of it alone. The locked-in syndrome attorneys at Newsome Law are happy to review your case, free of charge, and with no obligation.

Read more about Rich Newsome

Rich Newsome

Catastrophic Injury Locked-In Syndrome Attorney

Rich Newsome is a dedicated attorney specializing in catastrophic injury and medical malpractice cases. With over 25 years of experience, she is committed to advocating for victims and their families, ensuring they receive the justice and compensation they deserve.