Diffuse Axonal Injury

Posted on October 11, 2011 by Tim Titolo

 Diffuse Axonal Injury

Concussion is the most minor and the most common type of Traumatic brain injury (TBI). Technically, a concussion is a short loss of consciousness in response to a head injury, but in common language the term has come to mean any minor injury to the head or brain. Traumatic brain injury (TBI), a form of acquired brain injury, occurs when a sudden trauma causes damage to the brain. TBI can result when the head suddenly and violently hits an object, or when an object pierces the skull and enters brain tissue.  

Shaken baby syndrome is a type of inflicted traumatic brain injury that happens when a baby is violently shaken. A baby has weak neck muscles and a large, heavy head. Shaking makes the fragile brain bounce back and forth inside the skull and causes bruising, swelling, and bleeding, which can lead to permanent, severe brain damage or death. Shaken Baby Syndrome is commonly used to explain how diffuse axonal injury (DAI) occurs. Diffuse Axonal Injury is injury over a more widespread area.  Diffuse axonal injury isn’t the result of a blow to the head. Instead, it results from the brain moving back and forth in the skull as a result of acceleration or deceleration. Unlike a local injury: think gunshot wound. In addition to being one of the most common types of brain injuries, it’s also one of the most devastating.

Testing includes:

  • ·        Magnetic Resonance Imaging (MRI)—This test uses magnets, radio waves, and a computer screen to show detailed cross-sections of the brain. This is the preferred test for diagnosing diffuse axonal injury.
  • ·        CT Scan—This test uses an x-ray machine and a computer monitor to show detailed images of the interior of the brain. CT scans may results in false negatives, so can’t be relied on to give definitive results when it comes to diffuse axonal injury.
  • ·        Evoked Potentials—Commonly called the SSEP, BAER, and VEP, these tests look at the visual, auditory, and sensory pathways in the brain.
  • ·        Electroencephalogram (EEG)—This test measures the electrical activity in the brain
  • ·        Positron Emission Tomography (PET) – This test measures the metabolism in the brain.

Of patients with DAI, 80% demonstrate multiple areas of injury on computed tomography (CT) scans.

Classically, DAI has been considered a primary-type injury, with damage occurring at the time of the accident. Research has shown that another component of the injury comprises the secondary factors (or delayed component). Disruption causes local axonal transport impairment and, since the axons are injured, secondary swelling occurs.  Complete detachment occurs and retraction bulbs form over a period of time after the injury.

This is very important since many physicians evaluate patients in the Emergency Room who appear cognitively intact but later go on to diminished levels of cognition. That is why hospitals give patients presenting with any hit to the head or head injury signs and symptoms a “Head Injury Checklist” on discharge. This protects the hospital in the case of a patient going on to develop head injury symptoms. Patients are instructed to watch of dizziness, fatigue and vomiting. But rarely is one discharged from a hospital aware of the latent problems or likely to follow up.

In the law, those who defend against claims of traumatic brain injury want to focus on the hospital discharge as proof that there was no “real injury.” It is important to understand the science and medicine of traumatic brain injury. You can always read more about traumatic brain injury by visiting my Brain and Spine Injury Law Blog or Titolo Law Office website.

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TBI - Traumatic Brain Injury Types

Posted on October 10, 2010 by Tim Titolo

The damage from TBI - Traumatic Brain Injury can be focal, confined to one area of the brain, or diffuse, involving more than one area of the brain. Diffuse trauma to the brain is frequently associated with concussion (a shaking of the brain in response to sudden motion of the head), diffuse axonal injury, or coma. Localized injuries may be associated with neurobehavioral manifestations, hemiparesis or other focal neurologic deficits.

Types of focal brain injury include bruising of brain tissue called a contusion and intracranial hemorrhage or hematoma, heavy bleeding in the skull. Hemorrhage, due to rupture of a blood vessel in the head, can be extra-axial, meaning it occurs within the skull but outside of the brain, or intra-axial, occurring within the brain. Extra-axial hemorrhages can be further divided into subdural hematoma, epidural hematoma, and subarachnoid hemorrhage. An epidural hematoma involves bleeding into the area between the skull and the dura. With a subdural hematoma, bleeding is confined to the area between the dura and the arachnoid membrane. A subarachnoid hemorrhage involves bleeding into the space between the surface of the brain and the arachnoid membrane that lies just above the surface of the brain, usually resulting from a tear in a blood vessel on the surface of the brain. Bleeding within the brain itself is called an intracerebral hematoma. Intra-axial bleeds are further divided into intraparenchymal hemorrhage which occurs within the brain tissue itself and intraventricular hemorrhage which occurs into the ventricular system.

TBI can result from a closed head injury or a penetrating head injury. A closed injury occurs when the head suddenly and violently hits an object but the object does not break through the skull. A penetrating injury occurs when an object pierces the skull and enters brain tissue.

As the first line of defense, the skull is particularly vulnerable to injury. Skull fractures occur when a bone in the skull cracks or breaks. A depressed skull fracture occurs when pieces of the broken skull press into the tissue of the brain. A penetrating skull fracture occurs when something pierces the skull, such as a bullet, leaving a distinct and localized traumatic injury to brain tissue. Skull fractures can cause cerebral contusion.

Another insult to the brain that can cause injury is anoxia. Anoxia is a condition in which there is an absence of oxygen supply to an organ's tissues, even if there is adequate blood flow to the tissue. Hypoxia refers to a decrease in oxygen supply rather than a complete absence of oxygen, and ischemia is inadequate blood supply, as is seen in cases in which the brain swells. In any of these cases, without adequate oxygen, a biochemical cascade called the ischemic cascade is unleashed, and the cells of the brain can die within several minutes. This type of injury is often seen in near-drowning victims, in heart attack patients (particularly those who have suffered a cardiac arrest), or in people who suffer significant blood loss from other injuries that then causes a decrease in blood flow to the brain due to circulatory (hypovolemic) shock.
 

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