Pediatric stroke has been increasingly recognized over the past couple of years. However the process of diagnosis, methods of management and overall consequences are not fully understood yet. This is especially true in regard to language development. It is well established that having a pediatric stroke can lead to a language impairment later in life but the severity of the impairment is not fully understood yet. Studies addressing the effect of pediatric stroke on language have yielded conflicting results. However, in order to understand these effects we must first understand the different types of pediatric stroke as well as the risk factors associated with them.
The different types of pediatric stroke can be categorized by the age of the child. A perinatal stroke occurs in utero or in the first month of life. When a pediatric stroke occurs after the first month of life it is termed as a childhood stroke. The chance of having a perinatal stroke is significantly higher than having a childhood stroke. The lifetime risk of stroke is actually highest during the perinatal period of life (Felling et al. 2017). Strokes also differ in whether they are classified as ischemic or hemorrhagic. During an ischemic stroke a blood clot forms and prevents blood from flowing to the blocked part of the brain. Hemorrhagic strokes occur when a blood vessel in the brain breaks and blood is spilled into the surrounding tissue. Pediatric strokes are more commonly ischemic than hemorrhagic (Roach et al. 2008). There is a diverse range of risk factors in regard to pediatric stroke and there is some variation between the perinatal period and later childhood. Risk factors for perinatal stroke include cardiac disorders, perinatal asphyxia and most significantly, maternal and placental disorders Thrombosis is often the source of perinatal stroke. Thrombosis is clotting of the blood and it can occur at the placenta (Felling et al. 2017).
Some of the most significant risk factors for both perinatal and childhood strokes are preexisting illnesses such as cardiac disease or Sickle Cell Disease. Stroke is a one of the major complications of Sickle Cell Disease. In comparison, rates of stroke in children with Sickle Cell Disease are a lot higher than they are in children not diagnosed with disease (Roach et al. 2008). Cardiac disease is another significant risk factor. It is present within 2-31% of children who suffer from a pediatric stroke (Felling et al.2017). The different types of pediatric stroke as well as some the most significant risk factors are pretty well established. However what the long-term consequences of having a pediatric stroke are is still not fully understood.
Children who survive a pediatric stroke can potentially develop long-term disabilities such as cognitive and sensory impairments. Again, language development is a cognitive function that can often be impaired by the event of a pediatric stroke. However several studies have found that children who have survived a perinatal stroke are able to normally develop language after a short initial delay (Woolpert et al. 2016). However the question of whether these recovered language skills can be maintained as the brain matures has yielded conflicting results.
A study conducted by Ballantyne Spilkin, Hesselink, and Trauner (2008) aimed to understand the stability of intellectual and language functioning during development in children who had a perinatal stroke. They did longitudinal testing of cognitive abilities on twenty-nine preschool to school-age children who survived a perinatal stroke and 38 control participants. All participants were administered the Wechsler Intelligence Scale for Children-Revised (WISC-R) (Wechsler, 1974), the Wide Range Achievement Test-Revised (WRAT-R) (Jastak and Wilkinson, 1984), the Clinical Evaluation of Language Fundamentals-Revised (CELF-R) (Semel et al., 1987) and/or the Peabody Picture Vocabulary Test-Revised (Ballantyne et al. 2008).
Results of the study showed no evidence of decline in cognitive function over time. These results support the idea that the brain has the capacity for plasticity. Plasticity refers to the brain’s ability to adapt and reorganize after a brain injury like a stroke. It allows the brain to recover from injury and continue to develop cognitive functions such as language. The study also found that, unlike in adult-onset stroke, there was no difference in cognitive performance in regard to which hemisphere the lesions were. Instead they found that children who experienced seizures after perinatal stroke performed significantly poorer on all of the cognitive and language tests (Ballantyne et al. 2008). Overall this study supports the idea that there is ongoing plasticity in the developing brain following a perinatal stroke and that this plasticity allows for stability of cognitive functions like language over time.
Another study by Chapman et al. (2003) compared discourse ability in children who had a stroke with a control group of children who suffered an orthopedic injury. An orthopedic control group was used because they shared similarities to child stroke patients in regard to early medical trauma and physical stigmata. Chapman and colleagues (2003) acknowledged that children with stroke are able to demonstrate a full recovery and subsequent normal development of language. However they also note that this level of plasticity may only refer to vocabulary and grammatical functions of language. The study aimed to understand if the same level of plasticity was present in more challenging language measures, such as those evaluated by discourse. Discourse refers to the ability for one to write or speak about a topic.
During this study both groups were instructed to listen to a story and then retell it in as much detail as possible. All participants were then asked give a lesson that could be learned from the story. Results of the study found that the children in the stroke group produced significantly shorter sentences compared to the orthopedic control group. Children in the stroke group also produced fewer core propositions needed to produce a well-organized narrative. They also produced lower-level concrete interpretations of the stories. These results support the view that even though children with stroke are able to make remarkable recoveries in regard to basic language development they are at greater risk for poorer discourse outcomes. The reason for this might be because the brain is less efficient at compensating for more complex cognitive functions when it comes to language (Chapman et al. 2003). The results of this study conflict with the findings of Ballantyne and colleagues (2008). The fact that these studies yield conflicting findings shows that more research needs to be done to better understand how children with stroke fare over time in regard to plasticity and language development.
Another study conducted by Woolpert and Reilly (2016) sought to evaluate writing performance in children who had survived a perinatal stroke. Writing is dependent on language and is cognitively challenging. Participants of the experiment included 42 children who had a perinatal stroke and a control group of 60 typically developing (TD) children. All participants were given two tasks. During the first task the children were shown a picture where several things are going on at once. The picture shows a boy stealing cookies while his mother is washing dishes in an overflowing sink. The children were asked to describe everything they saw in the picture and then write down their description. In the second task the children were asked to talk about a time that made them feel sad or mad and describe how it started, what happened and how ended. They were then asked to write their narrative down (Woolpert et al. 2016).
Results of the study showed that children with perinatal strokes made significantly more spelling errors than their TD peers. They also scored below their TD peers on decoding and spelling. These results support the idea that children with perinatal stroke have slight but persistent deficits when it comes to more challenging functions of language. Woolpert and Reilly (2016) also found that there was no significant effects in regard to which hemisphere the lesion was in. A lesion is any abnormal damage in the tissue of an organism and they are often a result of a stroke. It is well established that adults who have acquired left hemisphere lesions have severe language impairments. However the effect they have on children who have had a perinatal stroke are less clear.
Holland et al. (2007) conducted a study where pediatric patients who had a left hemispheric perinatal stroke were examined using fMRI and the verb generation task to understand patterns of language organizations. During the task participants heard a noun every five-seconds and were instructed to covertly generate as many verbs associated with noun as possible during the 5 second interval. Results of this study showed several differences in the activation patterns between the stroke group and typically developing group of children. Most significantly the activation in the stroke group was concentrated in the frontal lobe of the right hemisphere. These results support the idea that if the left hemisphere is damaged early in language development, language processes and mechanisms can be reorganized to the right hemisphere (Holland et al.2007). The fact the brain can successfully reorganize something as complex as language processes is a prominent example of early brain plasticity. However the key to this phenomenon might be due to how young the children are (Lidzba et al. 2017).
Lidzba and colleagues (2017) were interesting in finding out if there was a time-window for successful right-hemispheric language organization after damage to the left hemisphere had occurred. Participants of the study consisted of children between the ages of 4 weeks and 18 years who all had left-hemispheric brain lesions. All patients or their families were sent questionnaires on persisting language problems. Patients who reported “moderate” or “no” persisting language problems were invited for an fMRI. After the fMRI scans were performed two age-limits for successful right-hemispheric language reorganization could be seen. Results showed that when lesions were acquired before the age of two, right-lateralization of language was present. When lesions occurred between the ages of 2 and 5 bilateral language representation was present. Results also showed that when lesions occurred after the age of 5 language problems persisted. The results could explain why children with perinatal stroke often do not have any persisting language impairments (Lidzba et al. 2017).
The risk of stroke is highest during the perinatal period of life (Woolpert et al. 2016). The long-lasting effects on language development of both perinatal and childhood stroke still need to be researched further. However due to the studies mentioned above, as well as many other ones, we are able to understand far more than we did several decades ago.
References:
Angela , B. O., Spilkin, A. M., Hesselink, J., & Trainer, D. A. (2008). Plasticity in the developing brain: intellectual, language and academic functions in children with ischaemic perinatal stroke. doi:10.1093/brain/awn176
Felling, R. J., Sun, L. R., Maxwell, E. C., Goldenberg, N., & Bernard, T. (2017). Pediatric arterial ischemic stroke: Epidemiology, risk factors, and management. Elsevier Inc. doi:10.1016/j.bcmd.2017.03.003
Holland , S. K., Vannest, J., Mecoli, M., Jacola, L. M., Tillema, J., Karunanayaka, P. R., . . . Byars, A. W. (2007). Functional MRI of Language Lateralization During Development in Children. Retrieved December 5, 2017.
Lidzba, K., Küpper, H., Kluger, G., & Staudt, M. (2017). The time window for successful right-hemispheric language reorganization in children. Elsevier Inc. doi:10.1016/j.ejpn.2017.06.001
Roach , S., Golomb, M. R., Adams, R., J., Daniels, S., DeVeber, G., . . . Smith, E. R. (2008). Management of Stroke in Infants and Children. American Heart Associations Inc. doi:10.1161/STROKEAHA.108.189696
Sandra, C. B., J. E., Gamino, J. F., McGlothlin, J. H., & Cliff, S. N. (2003). Discourse Plasticity in Children After Stroke: Age at Injury and Lesion Effects. Elsevier Inc., 29. doi:10.1016/S0887-8994(03)00012-2
Woolpert, D., & Reilly, J. S. (2016). Investigating the extent of neuroplasticity: Writing in children with perinatal stroke. Elsevier Inc., 105-118. Retrieved December 5, 2017.
