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Mannitol reduces optic nerve sheath diameter and ICP in traumatic brain injury patientsUltrasound Shows Brain Pressure Dropping Fast After Treatment

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Key Takeaway
Consider ONSD monitoring with mannitol in TBI, but note observational evidence.

This prospective cohort study enrolled 71 patients with traumatic brain injury admitted to the Neurocritical Care Unit of the First People’s Hospital of Changde. The intervention involved dynamic monitoring of optic nerve sheath diameter (ONSD) and mannitol infusion, with comparisons made before and 20 minutes after mannitol administration. The primary outcome was the relationship between ONSD and intracranial pressure (ICP).

Main results showed that ONSD decreased from 6.39 (6.13, 6.73) mm to 4.94 (4.71, 5.61) mm (p = 0.021), and ICP decreased from 35 (32, 41) mmHg to 21 (17, 28) mmHg (p = 0.010). No effect sizes or absolute numbers were reported for these changes. The study did not assess secondary outcomes.

Safety and tolerability data, including adverse events, serious adverse events, and discontinuations, were not reported. Limitations were not specified in the input, but the observational cohort design and lack of a control group beyond pre-infusion measurements constrain causal conclusions. Funding and conflicts of interest were not reported.

Practice relevance was not reported, but the findings may inform clinicians about short-term ONSD and ICP reductions with mannitol in this setting. However, the evidence is preliminary due to the single-center, observational nature and absence of safety data, warranting cautious interpretation in clinical decision-making.

The Heavy Weight on Your Brain

Imagine your brain is a sponge inside a hard skull. When you get a bad head injury, fluid builds up. This creates pressure that squeezes the brain.

Doctors call this intracranial pressure. If it gets too high, it can stop blood from flowing to the brain. This can cause permanent damage or even death.

Right now, doctors often use a special tube to measure this pressure directly. But putting a tube in the brain is risky. It can cause bleeding or infection.

Many hospitals want a safer way to check on patients. They need a method that is quick and does not require surgery.

A New Way to Check

For years, doctors have used an ultrasound probe on the eye. They look at the optic nerve sheath. This is the tube that protects the nerve leading to the brain.

Think of the optic nerve sheath like a balloon. When pressure inside the skull goes up, the balloon gets bigger. When pressure goes down, the balloon shrinks.

But here is the twist. Old studies said this only worked when pressure was very high. Doctors thought it was useless for lower pressure levels.

This new research changes that thinking. It shows the method works even when pressure is not at its worst.

The optic nerve sits right behind the eye. It is easy to see with an ultrasound.

When pressure rises, the fluid pushes against the nerve. The sheath around the nerve stretches out. It becomes wider.

When doctors give medicine to lower the pressure, the fluid drains away. The sheath relaxes and gets narrower again.

It is like a traffic jam on a highway. When too many cars are stuck, the road looks crowded. When traffic clears, the road opens up.

The optic nerve sheath acts like that road. It tells doctors exactly how crowded the space around the brain is.

Researchers looked at 71 patients with serious head injuries. These patients were already in the intensive care unit.

They had tubes in their brains to measure pressure directly. This gave them the "gold standard" number to compare against.

Doctors used a small ultrasound probe on both eyes. They took a picture before giving medicine. Then they waited 20 minutes.

After the medicine, called mannitol, they took another picture. Mannitol helps pull fluid out of the brain.

They compared the width of the sheath before and after. They also compared the pressure numbers from the tube.

The Surprising Results

The results were clear and strong. Before the medicine, the sheath was wide. The pressure was very high.

After the medicine, the sheath got much smaller. The pressure dropped significantly too.

The numbers matched perfectly. When the ultrasound showed a smaller sheath, the pressure tube agreed.

This means doctors can trust the ultrasound. It gives a real-time picture of what is happening inside the skull.

This doesn't mean this treatment is available yet.

What This Means for Patients

This is a huge step forward for safety. It means doctors can check pressure without poking the brain again.

It also means they can catch problems faster. If the medicine does not work, the ultrasound will show it immediately.

Patients do not need to wait for a risky procedure to get answers.

However, this tool is not for everyone yet. It needs more testing in different hospitals.

The Catch

The study only looked at patients who already had tubes in their brains. We do not know if the ultrasound works without the tube yet.

Also, the study happened in one hospital. Different machines might give slightly different pictures.

Doctors need to train their teams to use the probe correctly. It takes practice to get good pictures every time.

What Happens Next

Researchers will now test this on patients who do not have tubes. They want to see if it works for everyone.

They will also try to find out exactly how wide the sheath needs to be to say pressure is safe.

If this works, it could change how hospitals treat head injuries. It would make care safer and faster.

It would also help doctors in smaller towns who do not have expensive monitoring equipment.

The goal is simple. Give patients the best care possible with the least amount of risk.

This new way of looking at the brain brings us closer to that goal. It turns a complex problem into a simple scan.

Study Details

Study typeCohort
EvidenceLevel 3
PublishedApr 2026
View Original Abstract ↓
ObjectiveTo explore the role of dynamic monitoring of optic nerve sheath diameter (ONSD) in the assessment of intracranial pressure (ICP) in patients with traumatic brain injury (TBI).MethodsA prospective study was conducted on patients with traumatic brain injury admitted to the Neurocritical Care Unit of the First People’s Hospital of Changde between 01/06/2024 and 30/09/2025. All enrolled patients underwent invasive ICP monitoring. A 14–5 MHz ultrasound probe was used to measure the ONSD in both eyes, with ICP values recorded simultaneously during ONSD measurements. Data were collected both before and 20 min after mannitol infusion administration. The Wilcoxon signed-rank test was used to compare ONSD and ICP before and after mannitol infusion, and Spearman correlation analysis was performed to assess their relationship.ResultsA total of 71 TBI patients were enrolled in this study, including 37 males and 34 females, with a mean age of 57.1 ± 14.0 years. After mannitol infusion, ONSD significantly decreased from 6.39 (6.13, 6.73) mm to 4.94 (4.71, 5.61) mm (p = 0.021). Concurrently, ICP decreased from 35 (32, 41) mmHg to 21 (17, 28) mmHg, with a statistically significant difference (p = 0.010). Both ICP and ONSD were significantly lower after mannitol infusion compared to before infusion (p
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