Intracranial Injuries

All infants and children suspected of having an intracranial injury must undergo cranial computed tomography (CT) and/or magnetic resonance imaging (MRI). Ultrasonography (ultrasound) also may reveal intracranial abnormalities, but it does not provide imaging that is adequate for excluding or fully evaluating intracranial injury. CT has been the accepted method for initial evaluation of intracranial injury in child abuse, and was recently described as the key diagnostic study for identifying or confirming shaken baby syndrome. The advantages of this method of diagnostic imaging are:

• Speed — A CT scan requires from 5 to 15 minutes, in comparison to 30 minutes for an MRI scan. CT is also usually more readily available than MRI.
  
  
• Cost — A CT scan costs less than an MRI scan. The cost of CT is approximately two-thirds the cost of MRI (however, technological refinements may further reduce the time and cost of MRI).
  
  
• Better imaging of bone (although skull fractures are better detected by conventional radiographic techniques).
  
  
• Better detection of subarachnoid hemorrhage (bleeding into the ventricles—the cavities within the brain—and into the fluid that normally surrounds the brain), although MRI appears to provide a better indication of the ages of the areas of hemorrhage.

However, the extent of injuries may sometimes be underestimated by CT imaging. Preliminary studies indicate that MRI is substantially more sensitive than CT in identifying and characterizing most intracranial conditions resulting from abusive assaults. In patients with minimal external signs of injury, the increased sensitivity of MRI may provide evidence for shaking-induced injury that is not obtainable by CT scanning. MRI provides superior imaging of small subdural hematomas (blood clots), which may be the only objective imaging evidence of child abuse. Other types of intracranial injury—contusions on the cerebral cortex, cerebral edema, hypertension, injuries involving the posterior fossa (the internal base of the skull), and white-matter injuries—are also better imaged using MRI, as are conditions involving the spinal cord.

In addition to greater imaging sensitivity, MRI provides the following advantages over CT:

• Increased contrast resolution (clarity) — The visual impact of an MRI scan can lead to greater appreciation of the findings of abuse in a courtroom situation.
  
  
• Absence of ionizing radiation — This makes MRI especially attractive for repeated examinations of the brain and for use in children.
  
  
• Multiplanar imaging — Altering the magnetic field allows images to be obtained in multiple planes of view without repositioning the patient.

MRI should be performed in all cases of suspected intracranial injury when CT does not adequately explain the clinical findings. MRI examination is also indicated for children who exhibit chronic alterations in central nervous system (CNS) function and for infants who have symptoms of shaken baby syndrome but no clinical evidence of CNS injury. Because MRI may miss recent collections of blood if the examination is performed too soon after the injury, it should be delayed until several days after the suspected traumatic event.