| Discussion: |
Shear brain injury
-Angular acceleration that involves rotation of the head on its axis, with differential movement of the skull/dura and intracranial contents, as well as shearing forces within the brain
- affects a much greater area of the brain and tends to cause more significant injury to an infant due to the infant’s relatively thin and pliable skulls, large, heavy, and unstable heads, soft brains with a high water content, and flat skull base that permits the brain to move more readily in response to acceleration-deceleration forces
- more common than coup or countrecoup injury
- with child abuse: diffuse brain edema that may be related to strangulation and suffocation
- diagnosis requires a high index of suspicion, the signs and symptoms may be mild and nonspecific (eg, vomiting, poor feeding, irritability or lethargy) or severe and even life-threatening (eg, apnea or other breathing abnormalities, coma, seizures)
- often in vegetative state despite relative absence of abnormalities in CT scans
- LP demonstrates blood (usually only indicated in patients with secondary meningitis)
- Posttraumatic seizures are more common than with contusions and with the youngest patients
- 60-70% will have multiple seizures, 20-30% will experience permanent seizures, and posttraumatic epilepsy occurs in up to 5% of all children who suffer head trauma
- loss of consciousness and respiratory arrest may occur, retinal hemorrhages are a common, but not inevitable finding, and external cutaneous bruising may or may not be present
- Unenhanced CT of the head (with brain and bone windows) is the preferred imaging study for initial evaluation in suspected cases of inflicted head trauma
- However, most injuries are nonhemorrhagic and not clearly seen by CT
- Noncontrast brain MRI is superior in documenting the full extent of intracranial injuries and may demonstrate evidence of shearing injury missed by CT
- Because MRI sometimes fails to identify acute subarachnoid or subdural hemorrhage, it is traditionally obtained three to seven days after injury. MRI is the preferred modality for identifying subacute and chronic injury because it has the highest sensitivity and specificity.
- Lesions containing only edema are better seen on MRI T2-weighted images
- Shearing lesions tend to only involve the gray-white matter interfaces and are usually ovoid or round
- Lesions are often found in the splenium of the corpus callosum, the peripheral gray-white junctions, the dorsolateral aspect of the midbrain, and the basal ganglia
- Intraventricular hemorrhage may be present secondary to shearing of the subependymal veins or the choroid plexus
- On early follow-up studies, contusions and shearing injuries appear slightly larger than they initially did and severe brain atrophy may be present long-term
- Large linear white matter shears should raise high suspicion for nonaccidental trauma
- Brain swelling is well seen by CT, but may take 24-48 hrs to develop
- CT – Edematous brain is of low density, effacement of the gray-white interfaces, deep gray matter may be hypodense or occasionally hyperdense, and the cortical sulci and basilar cisterns may be obliterated
- If the child has suffered impact to the head, contact injuries, including skull fractures, scalp hematomas, and cerebral contusions may be identified
- A skeletal survey should also be performed to rule out any associated skeletal injury
References:Castillo, Mauricio and Mukherji, Suresh. Imaging of the Pediatric Head, Neck, and Spine, 1996.
Endom, Erin and Greenbaum, Jordan. "Overview of nonaccidental head injury in infants and children," for Up to Date Online, 2005.
Mierisch, RF, Frasier, LD, Braddock, SR, et al. Retinal hemorrhages in an 8-year-old child: an uncommon presentation of abusive injury. Pediatr Emerg Care 2004; 20:118.
Ettaro, L, Berger, RP, Songer, T. Abusive head trauma in young children: characteristics and medical charges in a hospitalized population. Child Abuse Negl 2004; 28:1099
Presented by Nicholas Brewer, Creighton University Medical Student