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What is SBS?

What kinds of injuries happen?

by Staff   5.28.2007

Common injuries from a shaking episode include but are not limited to the following:

Brain Injuries
During a shaking episode, the infant's brain moves back and forth in a figure-eight motion. This movement creates acceleration-deceleration forces on the brain. This force causes blood vessels to break and blood to spill into the spaces between the brain and its protective covers. Subdural hemorrhages are seen in 90% - 98% of SBS cases (Duhaime et al 1987) and subarachnoid hemorrhages are seen in approximately 83%, as well as in most autopsy cases (Gilles & Nelson 1998). Epidural hemorrhages, bleeding between the outermost protective cover and skull and subgaleal hemorrhages, bleeding between the scalp and skull, are occasionally seen when shaking is accompanied by impact.

Hemorrhages often increase pressure in the brain producing other injuries. The extra pressure squishes the brain inside the skull causing it to swell - cerebral edema. This in turn can cause other injuries such as hypoxia - lack of oxygen in the brain, ischemia - lack of oxygenated blood in the brain, infarction - tissue death, and encephalomalacia - brain softening. It is these secondary injuries that can cause the most devastating impact on infants such as cerebral palsy and death.

In addition to blood vessels breaking, a shaking episode can also create traumatic axonal injury. The axons are part of the neurons that are responsible for receiving and sending messages needed for breathing, thinking, heart functioning, etc. During the shaking episode, these axons can stretch and tear which damages the neurons to such an extent that the brain can stop functioning properly and these neurons can die.

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Eye Injuries
The same acceleration-deceleration forces that create brain injuries also cause injuries in and around the eye. The increased movement and pressure in the vessels of the eyes form retinal hemorrhages. This type of eye injury is seen in 70% - 85% of SBS cases (Tzioumi 1998; Levin 1990). There are different types of hemorrhages depending on their size and location. Retinal hemorrhages in the outside part of the eye look like flames and are therefore called flame or splinter hemorrhages. Those that are in the deeper tissues of the eye are round in shape and are labeled dot or blot hemorrhages, depending on their size. Hemorrhages on the outside of the retina or over a blood vessel are called preretinal hemorrhages. Retinal hemorrhages are generally spread out and can appear in either one or both eyes. Another severe eye injury resulting from shaking is the splitting of the retina, known as retinoschisis. Damage to the surrounding eye muscles and optic nerves are also common. Contrary to the above outline of eye damage, blindness usually does not occur because of damage to the eye itself, but rather from brain damage in the occipital region of the brain and the optic nerve.

Read the segment on Eye Injuries from an expert at Toronto's Hospital for Sick Children.

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Skeletal Injuries
Besides injuries to the brain and eyes, shaken baby syndrome can result in other trauma such as bone fractures.

Approximately 33% of skull fractures found in children under the age of two are abuse related (Hobbs 1984). The most common type of fracture is linear (horizontal) and the most common location is in the parietal area for both abuse and accidental cases (80 - 90% from abuse) (Leventhal et al 1993; Meservy et al 1987). Skull fractures that are multiple and found on both sides are more commonly non-accidental (Meservy et al 1987). Since specific skull fractures cannot confirm abuse, its presentation must be compared with the victim's history.

It is a natural behaviour to pick up an infant by the chest from a prone position or carry them with at least one hand on the chest area. When a caregiver loses control, this easily translates into grabbing a child by the rib area and shaking the infant, resulting in rib fractures. This type of fracture is more common in victims under the age of one (Bulloch et al 2000) as well as cases resulting in death (Kleinman et al 1995).

During a shaking episode, long bone fractures can occur with sudden pulling, jerking or twisting of the infant's arms and legs. Classic metaphyseal lesions (CML) occur when these strains are sent to the metaphysis and cartilaginous epiphysis of the long bones. CML's are common in abuse (Kleinman & Marks 1998). Two types of metaphyseal fractures are corner fractures and bucket-handle fractures, named after their appearance on X-rays.

Other types of skeletal injuries include but are not limited to:

Subperiosteal hemorrhage: when the periosteum, the connective tissue surrounding most bones, is separated from the bones causing blood to spill between the bone and the periosteum. This may also be accompanied by bone fractures.

Diaphyseal fractures: spiral fractures of a major long bone such as the upper arm or the thigh.

Distal clavicular / acromial fracture: twisting forces to the arm which are similar to corner fractures.

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Accidental vs. Non-Accidental Injury
The injuries referred to above are commonly seen in shaken baby syndrome cases, but they can also occur during accidents. Car accidents can cause brain injuries and internal bleeding, however, these injuries more commonly occur in different parts of the brain than SBS. For example, it is more common to see an epidural hemorrhage (bleeding between the outermost protective cover and skull) in a car crash than a subdural hemorrhage (bleeding between the brain and its protective cover) as seen in abuse. Eye injuries can be caused by severe accidents, birth trauma or birth defects, but these findings are rare and also commonly occur in different parts of the eye than SBS. Skeletal injuries can happen from accidental falls, but are not usually accompanied by severe brain damage. The important thing to keep in mind is that when injuries occur by accident, the history of events is very clear.

SBS can often be overlooked as the symptoms can be non-specific, similar to the flu. As reported by Jenny and colleagues (1999), more than 30% of cases in emergency wards during their study were missed. The most commonly missed infants were from intact Caucasian families with an infant under the age of 6 months. Caregivers of children displaying SBS symptoms only offer reasons for the injury approximately 36% of the time (Keenan et al 2004). Usually those that do admit to shaking the infant claim they only used mild forces which do not match the infant?s severe injuries.

Read the segment on Susected SBS from an expert at BC Children's Hospital.

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Long-Term Consequences of SBS
Psychological disabilities such as mood swings, anxiety, depression and behavioural issues (Luis & Mittenberg 2002).

Cognitive disabilities including learning difficulties, planning impairment, memory loss and developmental delays.

Physical disabilities such as muscle spasms, partial or total blindness, hearing impairment, paralysis, cerebral palsy and seizures (Barlow et al 2005).

Even infants considered "normal" when they leave the hospital may show cognitive and behavioural problems before starting grade-school (Bonnier et al 1995).

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Prognosis
22% - 30% are considered "well" (show no signs of health or developmental injury at the time of leaving the hospital) (Bonnier et al 1995; King et al 2003; Rosenthal et al 1990; Jayawant et al 1998).

30% - 55% suffer ongoing brain injury (King et al 2003; Rosenthal et al 1990; Jayawant et al 1998).

65% - 67% suffer ongoing eye injury (King et al 2003; Iverson 1998).

Approximately 85% need ongoing multidisciplinary care (King et al 2003).

19% - 23% die in hospital (King et al 2003; Fitzpatrick 1998).

Read the segment on Rehabilitation from an expert at Sunny Hill Health Centre for Children.

References



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