Brain Injuries; Cerebral Concussion, causes and treatment

Brain Injuries

Cerebral concussion is an injury associated with virtually every sport and with a host of work and recreational activities. Whether on the sideline, athletic training room, or clinical/hospital environment, a thorough and consistent approach to evaluating athletes suspected of a concussion will aid in improving clinical diagnoses and return-to-play decisions. However, when a head injury is suspected, the nature and severity of the injury must first be determined in order to develop an appropriate management plan. An injury that at first appears to be a concussion could actually involve more serious pathology. The athletic trainer should be skilled in the early detection and diagnosis of these injuries and in follow-up evaluation procedures.

Brain Injuries

Pathomechanics of Brain Injuries

Cerebral concussion can be defined as any transient neurological dysfunction resulting from an applied force to the head. A forceful blow to the resting movable head usually produces maximum brain injury beneath the point of cranial impact. This is known as a coup injury. A moving head hitting against an unyielding object usually produces maximum brain injury opposite the site of cranial impact (contrecoup injury) as the brain rebounds within the cranium.When the head is accelerated prior to impact, the brain lags toward the trailing surface, thus squeezing away the cerebrospinal fluid (CSF) and allowing for the shearing forces to be maximal at this site. This brain lag actually thickens the layer of CSF under the point of impact, which explains the lack of coup injury in the moving head injury. However, when the head is stationary prior to impact, there is neither brain lag nor disproportionate distribution of CSF, accounting for the absence of contrecoup injury and the presence of coup injury. Many sport-related concussions involve a combined coup–contrecoup mechanism but are not considered to be necessarily more serious than an isolated coup or contrecoup injury. If a skull fracture is present, the first two scenarios do not pertain because the bone itself may absorb much of the trauma energy or may directly injure the brain tissue. If the energy absorption is transient, a linear fracture may result; if the absorption is permanent, a depressed fracture may result. Focal lesions are most common at the anterior tips and the inferior surfaces of the frontal and temporal lobes because the associated cranial bones have irregular surfaces. Three types of stresses can be generated by an applied force when considering injury to the brain: compressive, tensile, and shearing. 

Compression involves a crushing force whereby the tissue cannot absorb any additional force or load. 

Tension involves pulling or stretching of tissue, and shearing involves a force that moves across the parallel organization of the tissue. Uniform compressive stresses are fairly well tolerated by neural tissue, but shearing stresses are very poorly tolerated. sensitivity to light or noise, loss of consciousness, blurred vision, difficulty remembering, or difficulty concentrating.  It is often reported that there is no universal agreement on the standard definition or nature of concussion; however, agreement does exist on several features that incorporate clinical, pathologic, and biomechanical injury constructs associated with head injury:

Types of Pathology

Several other terms are used to describe the injury, the most global being traumatic brain injury (TBI), which can be classified into two types: focal and diffuse. Focal brain injuries are posttraumatic intracranial mass lesions that may include subdural hematomas, epidural hematomas, cerebral contusions, and intracerebral hemorrhages and hematomas. These are considered uncommon in sport but are serious injuries. The athletic trainer must be able to detect signs of clinical deterioration or worsening symptoms during serial assessments to classify the injury and manage it appropriately. Signs and symptoms of these focal vascular emergencies can include loss of consciousness, cranial-nerve deficits, mental-status deterioration, and worsening symptoms. Concern for a significant focal injury should also be raised if the signs or symptoms arise after an initial lucid period in which the athlete seemed normal.

Diffuse brain injuries can result in widespread or global disruption of neurological function and are not usually associated with macroscopically visible brain lesions except in the most severe cases.Most diffuse injuries involve an acceleration–deceleration motion, either within a linear plane or in a rotational direction, or both. In these cases, lesions are caused by the brain essentially being shaken within the skull.The brain is suspended within the skull in CSF and has several dural attachments to bony ridges that make up the inner contours of the skull. With a linear acceleration–deceleration mechanism (side to side or front to back), the brain experiences a sudden momentum change that can result in tissue damage. The key elements of injury mechanism are the velocity of the head before impact, the time over which the force is applied, and the magnitude of the force. Rotational acceleration–deceleration injuries are believed to be the primary injury mechanism for the most severe diffuse brain injuries. Structural diffuse brain injury (diffuse axonal injury, or DAI) is the most severe type of diffuse injury because axonal disruption occurs, typically resulting in disturbance of cognitive functions, such as concentration and memory. In its most severe form, DAI can disrupt the brain stem centers responsible for breathing, heart rate, and wakefulness.Cerebral concussion, the most common sport-related TBI, can best be classified as a mild diffuse injury and is often referred to as mild traumatic brain injury (MTBI).

The injury involves an acceleration–deceleration mechanism in which a blow to the head or the head striking an object results in one or more of the following conditions: headache, nausea, vomiting, dizziness, balance problems, feeling “slowed down,” fatigue, trouble sleeping, drowsiness,

1. Concussion is caused by a direct blow to the head or elsewhere on the body, resulting in a sudden

mechanical loading of the head that generates turbulent rotatory and other movements of the cerebral hemispheres.

2. These collisions or impacts between the cortex and bony walls of the skull typically cause an immediate

and short-lived impairment of neurological function involving a variety of symptoms. In some cases the symptomatology is longer lasting and results in a condition known as postconcussion syndrome.

3. Concussion may cause neuropathological changes or temporary deformation of tissue; however, the acute clinical symptoms largely reflect a functional disturbance rather than a structural injury.

4. Concussion may cause a gradient of clinical syndromes that may or may not involve loss of consciousness (LOC). Resolution of the clinical and cognitive symptoms often follows a sequential course but is dependent on a number of factors including magnitude of the impact to the head and the individual’s concussion history.

5. Concussion is most often associated with normal results on conventional neuroimaging studies, such as magnetic resonance imaging (MRI) or computed tomography (CT) scan.

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