An Overview of Weber's Syndrome

Weber's syndrome is a neurological condition caused by an injury to the midbrain, the uppermost section of the brainstem. It's usually caused by a stroke (infarction), but in rare cases, Weber’s syndrome can also be caused by a brain tumor, a traumatic injury, or infection.

The midbrain is already one of the smallest regions of the brain, and Weber's syndrome affects functions controlled by a small section of this region—eye movement being one. Even though this area of the brain is quite small, people with Weber’s syndrome can experience several major neurological problems.

Symptoms

Weber's syndrome can cause sudden weakness and vision changes, usually blurred or double vision and eyelid droopiness. Weakness in the muscles of the face, arms, and legs is also possible.

In the case of a stroke, eye movement, and eyelid function are affected on the side of the infarction, with weakness of the face, arm, and leg on the opposite side. For example, a left-side stroke would affect the left eye and right face, arm, and leg.

Immediately after the stroke, symptoms may be at their worst because there may be swelling in and around the brainstem, which exacerbates the effect of the event.

Causes

Weber's syndrome indicates an injury to the left, right, or both sides of the midbrain. A stroke normally affects only one side, while an infection or injury can affect one or both sides.

In the setting of a stroke, patients with Weber's syndrome usually have an interruption of blood flow through the left or right posterior cerebral artery, the main vessels supplying blood to the midbrain. This interruption can damage the third cranial nerve, a key motor nerve that helps control eye and eyelid movement.

Sometimes, if a tiny branch of the posterior cerebral artery is interrupted, then the symptoms of a stroke are milder and less extensive than they would be if the whole posterior cerebral artery was interrupted. Normally, only a branch of the artery is interrupted in Weber’s syndrome strokes, though severity can vary.

Though causes aside from stroke are rare and not well-documented, Weber's syndrome can be caused by a brain injury, tumor, infection, or some other cause that affects blood flow in the midbrain.

For example, one report showed Weber's syndrome in a patient who experienced a penetrating wound to the midbrain. Another report showed Weber's syndrome in a patient who developed tuberculoma, a rare and severe form of tuberculosis in the brain. Another case developed from an aneurysm of the midbrain blood vessels.

In these rare cases, Weber's syndrome would appear to be a diagnosis that comes after the initial malady is examined and treated. Whether Weber's syndrome resolves in these types of cases will depend on the unique circumstances.

Diagnosis

Your medical team will base your diagnosis on visible symptoms and a physical examination, but pinpointing Weber's syndrome can be tricky.

One tool that has become key in diagnosing midbrain strokes is diffusion-weighted imaging (DWI), a form of magnetic resonance imaging (MRI). In one study, combined DWI techniques improved midbrain infarction detection rates without extra time expenditure.

Note: Weber's syndrome is not the same as Sturge-Weber syndrome, a rare condition diagnosed in newborns who have abnormal blood vessels on their face that can cause stroke-like weakness.

Treatment

Any brain injury is a serious medical emergency, and urgent treatment is necessary. According to the Centers for Disease Control and Prevention (CDC), stroke patients who go to the hospital via ambulance may be diagnosed and treated faster than those who don't call 911.

After initial care that addresses the cause of your symptoms, most people experience some improvement over time because swelling and inflammation in the brain diminish.

Your healthcare provider will guide recovery depending on the specifics of your case. Physical therapy (PT) aids in stimulating healing of the brain injury will likely be a key part of treatment. PT can also optimize your ability to move the muscles of your eye (in addition to those elsewhere in your body) despite any lingering brain damage.

Recovery can take weeks, months, or years depending on the severity of your midbrain injury, and may never be total. Your healthcare provider will be able to advise you on your prognosis.

A Word From Verywell

If you have Weber's syndrome due to a stroke, that means that you may have other stroke risk factors. A thorough medical evaluation can determine which stroke risk factors you have so that you can make the lifestyle changes necessary or take the medications needed to prevent another stroke.

If you have Weber's syndrome due to another illness or problem involving the brain, you are likely to experience improvement of your symptoms if the other issue can be addressed.