Contrecoup Brain Injury

Etiology

Contrecoup injuries typically occur when the moving head strikes a stationary object, in contrast to a coup injury that is associated with a moving object impacting a stationary head. Classic evidence of both coup and contrecoup injuries is an intracerebral hemorrhage or contusion that develops in a focal area identified on a computed tomography (CT) scan or magnetic resonance imaging of the brain. Contrecoup lesions occur due to forces within the intracranial cavity that are not directly related to the site of the focal blow. Instead, these lesions arise from the stress placed on the brain due to the force of the impact on a head that is already in motion. After the head receives the initial impact, the brain rebounds in the opposite direction, resulting in a second impact site that can cause brain injury.

Four theories have been proposed to explain the mechanism of contrecoup injury—positive pressure theory, negative pressure or cavitation theory, rotational shear stress theory, and angular acceleration theory.[10] According to the positive pressure theory, stress occurs when the brain lags behind the initial movement of the skull, followed by compression of the brain against the stationary, irregular skull on the opposite side.[2][11] The moving brain strikes the opposite side of the skull, typically at bony prominences, resulting in a contusion. The negative pressure or cavitation theory suggests that the movement of the brain in one direction generates stress in the opposite area of the brain, causing damage to the cerebral tissue at that site. The rotational shear stress theory incorporates rotation of the brain with the displacement along the axis of the trauma.[2][11] The angular acceleration theory postulates that the brain is tethered in certain regions, such as the brainstem, making other areas more susceptible to greater acceleration and deceleration forces within the brain.[2][12][13]

The difference in the density between the brain and the cerebrospinal fluid has been proposed as another mechanism for a contrecoup injury.[10] According to this theory, the brain moves away from the impact site, resulting in an injury on the opposite side of the skull. During an impact, the denser cerebrospinal fluid moves toward the site of the skull impact, displacing the less dense brain in the opposite direction. The fact that no single explanation accounts for all aspects of a contrecoup injury may imply that a combination of mechanisms contributes to the resulting contrecoup injury. The actual injury to the brain often occurs near the irregular surface of the temporal fossa and in the region beneath the frontal lobes. Notably, the severity of the injury at the contrecoup site is greater than that occurring at the coup site. Several case reports have documented contrecoup injuries occurring in the absence of coup injuries.[14]

Epidemiology

A contrecoup brain injury is a type of traumatic brain injury that may coexist with other types of trauma in a patient. Falls and vehicular accidents are the most common traumatic etiologies. These injuries are more prevalent in younger males, with a more even gender distribution occurring in older adults. Intracerebral hemorrhage occurs in 13% to 48% of adults with traumatic brain injury. Of these patients, 13% to 77% have contrecoup hemorrhages, which most often occur with an occipital and temporal site of skull impact.[13] Pediatric contrecoup injuries identified before the age of 4 are rare; however, the frequency increases rapidly with age.[1] This rarity in younger children is due to the elasticity of the bone and the presence of open sutures in infants.

Pathophysiology

The location of contrecoup brain injuries has been the subject of several studies that often produce conflicting results. One study found that temporal bone injuries correlated most strongly with contrecoup injuries occurring in the temporal lobe on the opposite side of the head.[14] Another study found that posterior impact injuries in the occipital location were most likely to cause contrecoup injuries in the frontal or temporal lobe areas.[15][16][15] Many of these patients were older and fell backwards. Some authors define a contrecoup brain injury by identifying a location more than 90° from the site of the coup impact,[13] suggesting that many contrecoup lesions are not exactly opposite to the site of the coup impact. There is an association between posterior impact sites and temporal intracerebral hemorrhage for contrecoup lesions. A frontal impact typically generates hemorrhages in the area of the initial anterior impact. Lateral contrecoup intracerebral hemorrhage is more likely to demonstrate hemorrhagic progression compared to the frontal and posterior locations of the contrecoup injury.[13]

The contrecoup brain injury has also been implicated in contralateral extra-axial skull pathology secondary to the trauma. One case report describes a case of mild head injury in which a skull fracture was noted on the opposite side of the head from the site of impact of the fall.[17] The contralateral fracture had no impact on that side. The authors proposed that the force of the impact caused local bending of the skull, with no fracture at the site of the impact, where the force was then transmitted through the skull to the opposite side, causing the fracture. There are also reports of epidural hematomas being located in a contralateral location opposite to the side of the trauma.[18][19][20][19] These contrecoup epidural hematomas were occasionally accompanied by an epidural hematoma at the site of impact, but not invariably.[21] In some cases, the contrecoup epidural hematoma was larger than the epidural hemorrhage associated with the coup impact. The dura mater may have detached from the inner table of the skull, and the small dural arteries may have caused the accumulation of blood.[2]

History and Physical

The primary aspect of the clinical history involves a thorough evaluation of the circumstances surrounding the trauma and any other significant contributing details. There is typically a history of head impact directly opposite the area of the brain that is injured. This impact site can be subtle and sometimes is not easily identified. The neurological findings depend on the exact location of the contrecoup injury. Altered mental status is a common clinical finding. Most frontal lobe lesions do not present with specific clinical findings. Patients may just be disoriented and confused. Temporal lobe injury can produce speech alterations or hemiparesis. Some patients present with seizures.

Evaluation

Patients with traumatic brain injury require a comprehensive evaluation for general trauma. All patients should be treated with advanced trauma life support measures. A detailed neurological examination is mandatory. A head CT scan without contrast administration is performed for the initial evaluation of brain injury. Cervical spine x-rays or a cervical CT scan should be performed to exclude any associated cervical fractures that can result from a fall.

Treatment / Management

The treatment of a contrecoup brain injury is dependent on the severity of the injury. For lesions that do not require immediate surgical intervention, such as evacuation or decompression, close clinical monitoring with repeat head CT at 12 or 24 hours is essential. More frequent CT scans at 6 to 8 hours may be appropriate if there is a concern for hemorrhagic progression. Patients with a decreased neurological status and a Glasgow coma scale of 8 or less should undergo intracranial pressure monitoring and be treated according to the trauma guidelines.[22] Some patients may require surgery, depending on neurological examination findings and the type and severity of the injury. The intervention may only require evacuation of the hematoma but can also be more extensive and involve a lobectomy or decompressive hemicraniectomy. Patients require antiepileptic medication administration for 7 days, according to current trauma guidelines. Contrecoup brain injury is a manifestation of traumatic brain injury and must be considered with other types of brain injury and in the presence of different body sites of traumatic injury.

Differential Diagnosis

The primary differential diagnosis for a contrecoup injury is diffuse axonal injury. In diffuse axonal injury, petechial hemorrhages develop at the gray-white matter junction, corpus callosum, and brainstem. This condition results from traumatic acceleration/deceleration or rotational injuries rather than from direct impact to the skull. Diffuse axonal injury is a frequent cause of persistent vegetative state in affected patients.[23][24]

Prognosis

The prognosis for a contrecoup injury varies depending on the extent of the involved areas and the presence of other types of head injuries, such as subarachnoid hemorrhage, diffuse axonal injury, and different types of traumatic brain injury. A report found that the outcome at 6 months was favorable in 48% of cases.[13]

Complications

Traumatic brain injury can lead to various neurological deficits, some of which may be permanent. The type of neurological deficit depends on the area of the brain affected by the contrecoup injury. Without prompt and appropriate management, contrecoup injuries may lead to serious complications, including coma or death.