New Imaging Techniques Show Longer-Term Effects of TBI

BANGKOK, THAILAND – New imaging techniques might help to explain the disabling symptoms that can plague patients with traumatic brain injury long after their acute problems have resolved, and eventually guide the best choice for medical therapy, Dr. Ramon Diaz-Arrastia said at the World Congress of Neurology.

Imaging techniques that are now well established in other areas of neurology–such as diffusion-weighted and susceptibility-weighted MR imaging–are now being used to show that brain injuries leave permanent, life-altering marks behind after the contusions and hematomas have healed.

These findings might have both immediate and long-range benefits, said Dr. Diaz-Arrastia, a professor of neurology at the University of Texas Southwestern Medical Center, Dallas.

In the future, imaging the post-TBI brain might help guide medical treatment choices and monitor drugs' effectiveness.

So far, nearly 30 drugs have provided effective neuroprotection in animal models of TBI, he said. However, none that has undergone testing in well-designed phase III trials has proven beneficial to humans.

Part of the problem might be the heterogeneity of human brain injury, Dr. Diaz-Arrastia said. There are many subtypes of TBI, yet “from the point of view of the clinical trials, all patients who present in a coma [after a brain injury] are treated the same way, even though the injuries can be very different, with very different prognoses.”

Susceptibility-weighted imaging (SWI) is one technique being studied in TBI patients. It measures the paramagnetic shift of intravascular deoxyhemoglobin and methemoglobin, amplifying the appearance of microhemorrhages and making them much easier to identify. “SWI picks up 640% more lesions and 200% more lesion volume than does gradient-recall echo,” Dr. Diaz-Arrastia said, referring to work by Dr. Karen Tong from Loma Linda (Calif.) University.

SWI is very good at identifying diffuse microvascular injury, a marker for diffuse axonal injury that is usually invisible on computed axial tomography. “The only problem is that SWI may be overly sensitive,” he said.

Diffusion-weighted imaging (DWI), which is well established in the stroke world, is understudied in TBI, probably because it's a challenge to perform magnetic resonance imaging on these acutely ill patients. But this technique provides detailed information about the makeup of lesions.

Diffusion tensor imaging shows how water tracks along the axons, giving a good view of white matter lesions. Follow-up scans on TBI patients have shown tantalizing clues to the possible causes of their long-term problems.

Another technique moving into trauma field is quantitative volumetric assessment of the cortical field. “We have found that the brain shrinks overall after a severe traumatic injury, but that not all structures shrink at the same rate. Some cortical regions shrink very little, while others appear particularly sensitive to injury.” This finding makes sense given the cognitive and mood issues that TBI patients can experience, he said.

Susceptibility-weighted imaging picks up 640% more lesions than does gradient-recall echo.

Source DR. DIAZ-ARRASTIA

BANGKOK, THAILAND – New imaging techniques might help to explain the disabling symptoms that can plague patients with traumatic brain injury long after their acute problems have resolved, and eventually guide the best choice for medical therapy, Dr. Ramon Diaz-Arrastia said at the World Congress of Neurology.

Imaging techniques that are now well established in other areas of neurology–such as diffusion-weighted and susceptibility-weighted MR imaging–are now being used to show that brain injuries leave permanent, life-altering marks behind after the contusions and hematomas have healed.

These findings might have both immediate and long-range benefits, said Dr. Diaz-Arrastia, a professor of neurology at the University of Texas Southwestern Medical Center, Dallas.

In the future, imaging the post-TBI brain might help guide medical treatment choices and monitor drugs' effectiveness.

So far, nearly 30 drugs have provided effective neuroprotection in animal models of TBI, he said. However, none that has undergone testing in well-designed phase III trials has proven beneficial to humans.

Part of the problem might be the heterogeneity of human brain injury, Dr. Diaz-Arrastia said. There are many subtypes of TBI, yet “from the point of view of the clinical trials, all patients who present in a coma [after a brain injury] are treated the same way, even though the injuries can be very different, with very different prognoses.”

Susceptibility-weighted imaging (SWI) is one technique being studied in TBI patients. It measures the paramagnetic shift of intravascular deoxyhemoglobin and methemoglobin, amplifying the appearance of microhemorrhages and making them much easier to identify. “SWI picks up 640% more lesions and 200% more lesion volume than does gradient-recall echo,” Dr. Diaz-Arrastia said, referring to work by Dr. Karen Tong from Loma Linda (Calif.) University.

SWI is very good at identifying diffuse microvascular injury, a marker for diffuse axonal injury that is usually invisible on computed axial tomography. “The only problem is that SWI may be overly sensitive,” he said.

Diffusion-weighted imaging (DWI), which is well established in the stroke world, is understudied in TBI, probably because it's a challenge to perform magnetic resonance imaging on these acutely ill patients. But this technique provides detailed information about the makeup of lesions.

Diffusion tensor imaging shows how water tracks along the axons, giving a good view of white matter lesions. Follow-up scans on TBI patients have shown tantalizing clues to the possible causes of their long-term problems.

Another technique moving into trauma field is quantitative volumetric assessment of the cortical field. “We have found that the brain shrinks overall after a severe traumatic injury, but that not all structures shrink at the same rate. Some cortical regions shrink very little, while others appear particularly sensitive to injury.” This finding makes sense given the cognitive and mood issues that TBI patients can experience, he said.

Susceptibility-weighted imaging picks up 640% more lesions than does gradient-recall echo.

Source DR. DIAZ-ARRASTIA

BANGKOK, THAILAND – New imaging techniques might help to explain the disabling symptoms that can plague patients with traumatic brain injury long after their acute problems have resolved, and eventually guide the best choice for medical therapy, Dr. Ramon Diaz-Arrastia said at the World Congress of Neurology.

Imaging techniques that are now well established in other areas of neurology–such as diffusion-weighted and susceptibility-weighted MR imaging–are now being used to show that brain injuries leave permanent, life-altering marks behind after the contusions and hematomas have healed.

These findings might have both immediate and long-range benefits, said Dr. Diaz-Arrastia, a professor of neurology at the University of Texas Southwestern Medical Center, Dallas.

In the future, imaging the post-TBI brain might help guide medical treatment choices and monitor drugs' effectiveness.

So far, nearly 30 drugs have provided effective neuroprotection in animal models of TBI, he said. However, none that has undergone testing in well-designed phase III trials has proven beneficial to humans.

Part of the problem might be the heterogeneity of human brain injury, Dr. Diaz-Arrastia said. There are many subtypes of TBI, yet “from the point of view of the clinical trials, all patients who present in a coma [after a brain injury] are treated the same way, even though the injuries can be very different, with very different prognoses.”

Susceptibility-weighted imaging (SWI) is one technique being studied in TBI patients. It measures the paramagnetic shift of intravascular deoxyhemoglobin and methemoglobin, amplifying the appearance of microhemorrhages and making them much easier to identify. “SWI picks up 640% more lesions and 200% more lesion volume than does gradient-recall echo,” Dr. Diaz-Arrastia said, referring to work by Dr. Karen Tong from Loma Linda (Calif.) University.

SWI is very good at identifying diffuse microvascular injury, a marker for diffuse axonal injury that is usually invisible on computed axial tomography. “The only problem is that SWI may be overly sensitive,” he said.

Diffusion-weighted imaging (DWI), which is well established in the stroke world, is understudied in TBI, probably because it's a challenge to perform magnetic resonance imaging on these acutely ill patients. But this technique provides detailed information about the makeup of lesions.

Diffusion tensor imaging shows how water tracks along the axons, giving a good view of white matter lesions. Follow-up scans on TBI patients have shown tantalizing clues to the possible causes of their long-term problems.

Another technique moving into trauma field is quantitative volumetric assessment of the cortical field. “We have found that the brain shrinks overall after a severe traumatic injury, but that not all structures shrink at the same rate. Some cortical regions shrink very little, while others appear particularly sensitive to injury.” This finding makes sense given the cognitive and mood issues that TBI patients can experience, he said.

Susceptibility-weighted imaging picks up 640% more lesions than does gradient-recall echo.

Source DR. DIAZ-ARRASTIA