Introduction/overview:
Believe it or not, shaken baby syndrome can develop from just five seconds of vigorous shaking. Shaken baby injuries typically occur in children two years old and but can be seen in children as old as five. When infants or toddlers are shaken, the brain bounces against the skull. This causes cerebral contusion as well as bleeding, pressure, and swelling within the brain. Large veins along the brain's exterior may tear, giving rise to additional bleeding and swelling as well as increased pressure; this can surely cause permanent brain damage if not death.
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Functional anatomy
1. Brain: Contains gray and white matter; composed primarily of neurons, glial cells
2. Cerebrospinal fluid: Produced in choroidplexus of brain; clear, colorless bodily fluid
3. Dura mater: Outermost of the three meningeal layers surrounding brain, spinal cord
4. Fontanelles: Soft spots on the heads of newborns; enable skull bony plates to flex
5. Pupil: Hole located in center of iris that permits entrance of light into retina
6. Retina: Lines inner surface of eye; light-sensitive layer of tissue
7. Vertebrae: Situated in dorsal aspect of torso; houses and protects spinal cord
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Input and output pathways:
Diffuse axonal injury, an effect of shaken baby syndrome, is a common, devastating form of traumatic brain injury. Diffuse axonal injury refers to pervasive lesions in the white matter tracts and is a major cause of unconsciousness as well as persistent vegetative state following head trauma. The outcome of diffuse axonal injury is often coma as ninety percent of patients suffering from DAI never regain consciousness. The disruption of axons is the primary cause of damage in diffuse axonal injury. Axonal tracts which, due to myelination, appear white and are regarded as "white matter."
When the brain experiences acceleration, shearing injury occurs. Shearing refers to the damage inflicted as tissues slide over other tissues. When the brain accelerates, areas of different densities slide over one another and stretch axons that span junctions between the white and gray matter. Two-thirds of diffuse axonal injury lesions occur where the gray and white matter intersect. White matter lesions vary in size, ranging from roughly one to fifteen millimeters and are distributed in a unique way.
Diffuse axonal injury most often affects white matter in regions including the brainstem, corpus callosum, and cerebral hemispheres. Frontal and temporal lobes, meanwhile, are the brain lobes most likely to experience injury. Other common diffuse axonal injury sites include the basal ganglia and thalamus. It is thought that these areas are more readily damaged because of the disparity in density or composition between them and the remainder of the brain. said, how might a damaged basal ganglia or thalamus influence various input and output pathways?
The three dominant ascending pathways are the anterolateral, dorsal column medial lemniscal, and the spinocerebellar pathways. The anterolateral pathway conveys pain, crude touch, and temperature information from the periphery to the brain. The spinothalamic tract, important in localizing painful or thermal stimuli, terminates in the thalamus a DAI-affected site which will now be unable to appropriately process the input it has received. The thalamus is also involved in the DCML pathway. Second order neurons travel up the brainstem and synapse within the thalamus--at the ventral posteromedial and ventral posterolateral nuclei. Third order neurons originating in the thalamus ordinarily traverse the internal capsule before synapsing in the postcentral gyrus. With severe thalamic damage however I can't see this process working quite as planned.
In addition to the three primary ascending pathways, there are four major descending pathways. These include the rubrospinal, reticulospinal, vestibulospinal (medial and lateral), and tectospinal tracts. Areas affected by diffuse axonal injury aren't as involved in these four or five pathways but because of the snags they cause in ascending pathways, output pathways will not function as they should.
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Detailed presentation:
Shaken baby syndrome involves three main medical symptoms: cerebral edema, retinal hemorrhage, and subdural hematoma; given these symptoms, doctors infer child abuse brought about by shaking of an intentional nature. In most SBS cases there are no visible signs of external trauma. SBS is oftentimes fatal and can cause significant brain damage. Estimated mortality among infants with the syndrome range from fifteen to nearly forty percent, the median being between twenty and twenty-five percent. Although half of child abuse-related deaths are due to SBS, the syndrome has nonfatal consequences and they include varying degrees of cognitive, motor, and visual impairment.
Again, characteristic SBS injuries include subdural hematoma, retinal hemorrhages, and multiple long bone fractures. Rotational injury is particularly damaging and likely to appear in shaking trauma. The injuries caused by shaking are not usually caused by impacts from normal play or falls, these being characterized by linear forces. The mechanism behind ocular abnormalities seems to be connected with vitreo-retinal traction, as vitreal movement contributes to the formation of the hemorrhage. These ocular findings, furthermore, correlate quite strongly with intracranial abnormalities.
Examination by a respected and experienced ophthalmologist is often vital in diagnosing the syndrome as certain types of ocular bleeding are characteristic. No other conditions exactly mimic SBS, but those which are to be ruled out include the following: Sudden infant death syndrome, hydrocephalus, seizure disorders, and congenital or infectious diseases like metabolic disorders and meningitis. Magnetic resonance imaging and CT scanning are both used in diagnosing the syndrome. SBS treatment involves the monitoring of intracranial pressure as well as the draining of cerebral fluid and of any hematoma. SBS prognosis depends heavily on severity, ranging from complete recovery to disability to death where the injuries are most severe; one-third of patients die, another third survive with a severe neurological condition while the final third survives in good health (cerebral palsy, hydrocephalus, learning disabilities, seizure disorders, speech disabilities and visual disorders comprise the most common neurological impairments).
Small children are obviously at high risk for SBS abuse given the significant difference in size between child and adult. Although it occurs mostly in infants under two, SBS may occur in children up to 5 years old. Caregivers at risk for growing abusive often have unreasonable expectations for the child and might display "role reversal," expecting children under their care to fulfill their personal needs. Emotional stress and substance abuse are additional risk factors for impulsiveness and even aggression in caregivers. Although it had previously been speculated that occurrences of SBS were "isolated," a history of prior abuse is often found in cases of shaken baby syndrome.
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Concluding paragraph:
In summary, SBS has been known to occur from as few as five seconds of shaking. Shaken baby injuries occur in children between two and five and are characterized by cerebral contusions, bleeding within the brain, and increases in pressure and swelling. When the toddler is shaken, its brain contacts the skull, bouncing back and forth against it. Large veins along the brain's exterior may tear, leading to yet more bleeding and swelling as well as increased pressure. This can easily cause brain damage and death.
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Key terms:
1. Blindness: Loss of useful sight; can be temporary or permanent
2. Brain: The portion of the CNS located within the skull
3. Brain swelling: Related to cerebral edema
4. Breathing: Process of respiration
5. Cerebral: Pertaining to the brain's cerebrum
6. Child abuse: Complex set of behaviors including child neglect as well as the emotional, physical, and sexual abuse of children
7. Intracranial: Within the cranium, the dome that houses and protects the brain
8. Neurological: Having to do with nerves and the nervous system
9. Prognosis: A patient's chance of recovery; the forecast of the disease's most probable outcome
10. Retinal: Involving the retina, the layer of neurons lining the back of the eye
11. Skull: A collection of bones encasing the brain which give form to the face and head
12. Spinal cord: Nerve tissue column connected to brain; lies within vertebral canal; column from which spinal nerves emerge
13. Subdural: Below the dura, the outermost of the three meninges covering the spinal cord and brain
14. Syndrome: A combination of signs and symptoms that represent a disease process
15. Trauma: An emotional or physical injury


Suggested reading:
Related diseases and conditions
1. Fracture
2. Nausea and vomiting
3. Subconjunctival hemorrhage


Quiz:
True/false:
1. True or false: It is quite common for children as old as seven (7) to exhibit symptoms of SBS.
2. True or false: Fewer than 25% of SBS cases result in death.
3. True or false: SBS can almost always be recognized simply by looking at the symptomatic child.
4. True or false: SBS can develop from as few as five (5) seconds of vigorous shaking.

Multiple guess:
Which of the following is not a characteristic SBS injury:
A. Subdural hematomas
B. Retinal hemorrhages
C. Constricted pupils
D. Multiple long bone fractures

Short answer:
1. What is one reason why caregivers might resort to abuse? Explain in at least 2-3 sentences.
2. Explain the main differences between a hemorrhage and a hematoma.
3. Explain how thalamic injury affects input and/or output pathways.


Reference list:
1. The Next Innocence Project: Shaken Baby Syndrome and the Criminal Courts. Deborah Tuerkheimer. Washington University Law Review. Volume 87 Number 1,2009
2. Centre for Forensic Science and Medicine SeminarChild Abuse - Nonaccidental Injury (NAI)presenter(s) Patrick D. Barnes Power Point Presentation. Lecture notes and references
3. Wrongful Diagnosis of Child Abuse - A Master Theory. Journal of the Royal Society of Medicine. VOLUME 98, NUMBER 6, 2005
4. British Medical Journal 2004:328:719-720 (27 March)
5. Shaken Baby Syndrome: A Questionable Scientific Syndrome and a Dangerous Legal Concept. Utah Law Review