eMedicine Specialties > Radiology > Brain/Spine

Brain, Contusion

Author: Denise Morales, MD, Clinical Assistant Professor, Department of Physical Medicine and Rehabilitation, Rehabilitation Institute of MI
Coauthor(s): Orlando Diaz-Daza, MD, Assistant Professor, Department of Radiology, Ben Taub General Hospital, Baylor College of Medicine; Roman Hlatky, MD, Assistant Professor, Center for Neurosurgical Sciences, The University of Texas Health Science Center; L Anne Hayman, MD, Director of Herbert J Frensley Center for Imaging Research, Professor, Departments of Radiology, Psychiatry, and Behavioral Sciences, Baylor College of Medicine
Contributor Information and Disclosures

Updated: Apr 3, 2007

Introduction

Background

Brain injury is often defined differently in published reports. Although many authors use the term brain injury to mean acute traumatic damage to the central nervous system (CNS), others use the term head injury, which allows inclusion of skull injuries, fractures, or soft tissue damage to the face or head without any obvious neurologic consequences. Kraus et al define brain injury as "physician-diagnosed physical damage from acute mechanical energy exchange resulting in concussion, hemorrhage, contusion, or laceration of the brain."¹

For excellent patient education resources, visit eMedicine's Back, Ribs, Neck, and Head Center. Also, see eMedicine's patient education article Concussion.

Pathophysiology

Brain contusions commonly are identified in patients with traumatic brain injury (TBI) and represent regions of primary neuronal and vascular injury. These edematous lesions contain punctate parenchymal hemorrhages, which are termed microhemorrhages. By definition these parenchymal bruises are found on the surfaces of the brain. Blood may extend bidirectionally into the white matter and the subdural and subarachnoid spaces.

Contusions are formed in 2 ways: direct trauma and acceleration/deceleration injury. Direct trauma causes injury at the site of impact, which is termed a coup contusion, while deceleration causes injury at a site opposite to the site of impact, which is termed a contrecoup contusion.

In the first mechanism, direct trauma, the head is not in motion. This mechanism may result in a scalp or skull injury.

The second mechanism is related to acceleration (eg, boxing injury) or deceleration (eg, motor vehicle accident), which causes the brain to strike the skull. In an event in which the head is in motion, cortical injury occurs adjacent to the floor of the anterior or posterior cranial fossa, the sphenoid wing, the petrous ridge, the convexity of the skull, and the falx or tentorium. The inferior frontal and temporal lobes are particularly vulnerable.

Gliding contusions are due to sagittal angular acceleration with abrupt stretching and tearing of the parasagittal veins, arachnoid membrane, and adjacent cerebrum. Gliding contusions occur along the superior margin of the cerebral hemispheres. Sganzerla et al concluded that the gliding contusion should be considered another type of primary brain damage brought about by acceleration/deceleration shear strains. Therefore, these authors believe that a patient with a gliding contusion will most likely have diffuse axonal injury as well.

Contusions may progress with time. CT scans often demonstrate progression over time in the size and number of contusions and the amount of hemorrhage within the contusions. Such changes are most evident over the first 24-48 hours, with one fourth of cases demonstrating delayed hemorrhage in areas that were previously free of hemorrhage.

Frequency

United States

Variations in the reported incidence may be due to different data collection methods and the diversity of the populations studied. Each year, TBI occurs in more than 800,000 people in the United States. Although 90% of patients survive the injury, 25% or more have significant residual complaints.² The National Institutes of Health (NIH) Consensus Statement 1998 estimates that 1.5-2 million Americans have a TBI each year, or an annual incidence of 100 cases per 100,000 persons.³

The National Health Interview Survey (NHIS) estimates that 1.5-2 million people have a TBI each year in the United States. Approximately 1 million of these individuals are treated in hospital emergency departments (EDs). Using self-reported data from the 1991 NHIS Injury Supplement (NHIS-I), Sosin et al estimated that 1.5 million persons had TBIs in 1991.⁴ Among these, 35% (525,000, or 216 cases per 100,000 population) received medical attention in EDs and were not admitted to the hospital.

Mortality/Morbidity

• Mortality: In 1994, more than 147,500 Americans died of traumatic injury. This figure represents approximately 6.5% of all deaths in the United States. The exact mortality rate involving significant TBI is not known, and estimates of mortality rates vary. The reported TBI mortality rate varies from 14-30 cases per 100,000 population. Thurman et al estimate the 1994 incidence rate of fatalities and hospital admissions in patients with TBIs was 91 cases per 100,000 population.⁵ Annegers et al note that the elderly population has the highest mortality rate.⁶ However, Woo et al note that the mortality rates for TBI are highest in persons aged 15-24 years.⁷ The mortality rates are as follows:
  
  
  • Persons aged 15-24 years - 33 cases per 100,000 population
  • Persons aged 65 years or older - 31 cases per 100,000 population
     
• Morbidity: A national estimate of all hospitalized and nonhospitalized nonfatal TBIs in the United States was derived from NHIS data for the years 1985-1987. Extrapolated to the 1990 US Census figure of approximately 249 million residents, the NHIS reports approximately 2 million incidents of TBIs per year. Fife concluded that only 1 of 6 persons with head injuries had an injury severe enough to warrant admission to a hospital.⁸ Since the number of individuals who seek some form of medical care from non-ED facilities is unknown, the NHIS figure of 1.975 million injuries remains an uncertain estimate of the true incidence of TBI in the entire population.

Race

Rosenthal et al note that hospital data vary widely in noting ethnicity or race in medical records; hence, the true incidence of TBI in racial or ethnic groups has yet to be determined accurately. Several studies have noted that TBI tends to occur with slightly greater frequency among minority groups.

Sex

In all studies of TBIs, men outnumber women by a ratio of at least 2:1. TBI fatalities in males are 3-4 times more frequent than in females. Rosenthal et al report a male-to-female ratio of approximately 2.0-2.8:1. Injuries from motor vehicle accidents, contact sports, and interpersonal violence are more common among males, who also have a higher rate of alcohol abuse.

Age

Studies of brain injury rates in the United States show that people aged 15-24 years are at the highest risk. Patterns in age-specific rates illustrate 2 generally high rates. Rates generally peak after age 15 years, decline after age 24 years, and continue to decline in the middle-aged years. Rates increase again in persons aged 60-65 years.

Anatomy

Anatomic diagrams depict typical locations of brain contusions. See Image 1 for schematic diagrams of sagittal, lateral, and base views of the brain depicting the areas most commonly affected by contusions and the areas occasionally affected by contusions.

Presentation

The uniform use of a clinical grading scale has improved comparisons between studies and assessment of outcome measurements. The rating system is termed the Glasgow Coma Scale (GCS).

After TBI, the first grade usually applied is a scale indicating depth of coma. The GCS has gained wide acceptance as a method of assessing severity of injury. The GCS has been tested extensively for interrater reliability and shows a high level of agreement, an issue of obvious importance when multiple observers may be observing the same patient sequentially.

On the basis of the GCS, patients may rapidly be assigned to a category of severe (score 3-8), moderate (score 9-12), or mild (score 13-15) brain injury. These categories determine the urgency of subsequent investigation and treatment. Total scores range from the lowest possible, 3, to the highest possible, 15.

The GCS is intended to assess level of consciousness and is not designed for following neurologic deficits.

GCS test response scoring is as follows:

• Eye opening
  • Opens eyes on own (spontaneous) - 4
  • Opens eyes on request (responds to speech) - 3
  • Opens eyes in response to pain - 2
  • Does not open eyes in response to pain - 1
• Best motor response
  • Follows simple commands - 6
  • Localizes pain - 5
  • Withdraws to pain - 4
  • Abnormal flexion (decorticate) - 3
  • Abnormal extension (decerebrate) - 2
  • No response to pain stimuli - 1
• Verbal response (speech)
  • Converses, is oriented - 5
  • Confused, disoriented - 4
  • Speaks, makes no sense - 3
  • Makes sounds only, no words - 2
  • Makes no noise (no speech) - 1

Preferred Examination

CT imaging is the preferred acute imaging modality because scans can be performed quickly; newer CT scanners can complete a scan within 5 minutes, with virtually no motion artifacts. CT findings help identify abnormalities that may need acute intervention. CT can be performed in the presence of life support equipment.

Limitations of Techniques

With CT scans, the true volume of neuronal damage in the contused tissue can be underestimated. The detection of superficial contusions using CT scans is hampered by artifacts from adjacent bone. MRI is more sensitive and accurate than CT for detecting contusions because of its multiplanar capability and greater sensitivity for edema.⁹

Imaging findings in brain contusions tend to vary because of the stages of evolution common to these lesions. Initially, CT findings can be normal or minimally abnormal because the partial volumes between the dense microhemorrhages and the hypodense edema can render contusions isoattenuating relative to the surrounding brain.

MRI findings typically demonstrate the lesions from the onset of injury, but many facilities cannot perform MRI on an emergent basis. In addition, MRI examination can take up to an hour to perform, and patients may require sedation to minimize motion artifacts. Not all hospitals have MRI-compatible life-support devices, and the patient's body habitus must be physically compatible with the size of the machine.

Differential Diagnoses

Other Problems to Be Considered

In the setting of trauma, radiologic findings are almost always diagnostic. Injuries to other parts of the body must not be overlooked. Accompanying diffuse intravascular coagulopathy may worsen intracranial bleeding.

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