Publications

Anatomy

Cerebral diaschisis in nAIS

Diaschisis refers to changes in brain areas functionally connected but structurally remote from primary injury. Acute diffusion weighted imaging in babies immediately after stroke (neonatal arterial ischemic stroke (nAIS)) was used to quantify cerebral diaschisis in the thalamus, corpus callosum, cerebral peduncle and caudate. While cerebral diaschisis was present in many babies, the degree of diaschisis was not related to motor outcomes. 

Srivastava R, Rajapakse T, Carlson HL, Kees J, Wei X-C, Kirton A (in press). Diffusion Imaging of Cerebral Diaschisis in Neonatal Arterial Ischemic Stroke. Pediatric Neurology. View

Thalamic diaschisis

Diaschisis refers to alterations in brain structures remote from, but connected to, stroke lesions. We measured thalamic volumes after perinatal stroke and found that ipsilesional volume loss was not associated with clinical motor function. Contralesional volume was inversely correlated with clinical motor function, suggesting the thalamus is involved in the known developmental plasticity that occurs in the contralesional hemisphere after early unilateral injury.

Craig B, Carlson HL & Kirton A. (2019). Thalamic diaschisis following perinatal stroke is associated with clinical disability. Neuroimage: Clinical, 21, 101660. View

Crossed cerebellar atrophy

We measured crossed cerebellar atrophy (CCA), a chronic cerebellar volume loss following contralateral motor pathway injury, in children after perinatal stroke. Larger ipsilesional cerebellar volume was associated with poorer cognitive and motor outcomes.

Craig B, Olsen C, Mah S, Carlson HL, Wei X-C & Kirton A (2019). Crossed cerebellar atrophy in perinatal stroke. Stroke, 50, 175-177. View

Alterations in myelination after perinatal stroke

Myelination of apparently uninjured brain in both the ipsilesional and contralesional hemispheres is decreased after perinatal stroke. Differences appear to radiate outward from the lesion. Further study is needed to determine clinical significance.

Yu S, Carlson HL, Mineyko A, Brooks BL, Kuczynski A, Hodge J, Dukelow S & Kirton A (2018). Bihemispheric alterations in myelination in children with unilateral perinatal stroke. Neuroimage: Clinical, 20, 7-15. View

Diaschisis in acute childhood AIS

We demonstrate that diffusion imaging may detect changes in brain structures remote from but connected to acute arterial ischemic stroke (AIS) lesions in children. These changes were associated with subsequent cognitive and motor outcomes.

Kirton A, Williams E, Dowling M, Mah S, Hodge J, Carlson HL, Wei X, Ichord R & PedNIHSS Investigators (2016). Diffusion imaging of cerebral diaschisis in childhood arterial ischemic stroke. International Journal of Stroke, 11(9), 1028-1035. View

Functional Connectivity

Functional connectivity of language networks

We measured organization of language networks after perinatal stroke and found that children with left hemisphere stroke may develop compensatory right-lateralization of language and that children with arterial strokes showed less connectivity than venous and controls. Lower connectivity is associated with poorer language comprehension performance and these findings may inform language interventions and instructional strategies.

Carlson HL, Sugden C, Brooks BL & Kirton A. (in press). Functional connectivity of language networks in perinatal stroke. Neuroimage: Clinical, 101861. View.

Sensorimotor functional connectivity

Resting state fMRI measures of sensorimotor functional connectivity were associated with clinical sensorimotor function in children with unilateral cerebral palsy secondary to periventricular venous infarction.

Woodward KE, Carlson HL, Kuczynski A, Saunders J, Hodge J & Kirton A (2019). Sensory-motor network functional connectivity in hemiparetic children with perinatal stroke. Neuroimage: Clinical, 21, 101670. View

Motor functional connectivity after stroke

Both arterial ischemic stroke (AIS) and periventricular venous infarction (PVI) can damage motor pathways. We investigated resulting alterations in functional motor networks and probed function. We found significant differences in both strength and laterality of motor network connections for AIS but not PVI. Function was not related to connectivity.

Saunders J, Carlson HL, Cortese F, Goodyear B & Kirton A. (2019). Imaging functional motor connectivity in children with perinatal stroke. Human Brain Mapping, 40, 1632-1642. (Our sensorimotor art is featured on the cover of this issue). View

Structural Connectivity

Motor tractography and proprioception

Using diffusion tensor imaging, we investigated the relationship between corticospinal tract diffusion properties and robotic visually guided reaching in children with hemiparetic cerebral palsy. We found that diffusion properties of the lesioned CST are altered after perinatal stroke, the degree of which correlates with specific elements of visually guided reaching performance.

Kuczynski AM, Hodge JA, Carlson HL, Lebel C, Dukelow SP, Semrau JA & Kirton A (2017). Corticospinal tract diffusion properties and robotic visually guided reaching in children with hemiparetic cerebral palsy. Human Brain Mapping, 39(3), 1130-1144. View

Sensory tractography and proprioception

We aimed to characterize the relationship between sensory (dorsal column medial lemniscus (DCML)) pathway connectivity and proprioceptive dysfunction in children with perinatal stroke using a proprioception robot. Both arterial and venous stroke groups demonstrated impairments in proprioception that correlated with lesioned hemisphere DCML tract diffusion properties.

Kuczynski AM, Carlson HL, Lebel C, Hodge JA, Dukelow SP, Semrau JA & Kirton A (2017). Sensory tractography and robot-quantified proprioception in hemiparetic children with perinatal stroke. Human Brain Mapping, 38(5), 2424-2440. View

Cortical spinal tract properties in CP

We used diffusion tensor imaging to assess corticospinal tract diffusion properties in hemiparetic children with perinatal stroke and found differences compared to peers. Correlations with disability support clinical relevance and utility in model development for personalized rehabilitation.

Hodge J, Goodyear B, Carlson HL, Wei X & Kirton A (2017). Segmental diffusion properties of the corticospinal tract and motor outcome in hemiparetic children with perinatal stroke. Journal of Child Neurology, 32(6), 550-559. View

DTI tractography in pediatric epilepsy

In a group of children with epilepsy, we isolated multiple major white matter tracts using diffusion tensor imaging tractography. We demonstrate that even in brains of children with neurological disease, tractography methods are reliable.

Carlson HL, Laliberte C, Brooks BL, Hodge J, Kirton A, Bello-Espinosa L, Hader W & Sherman EMS (2014). Reliability and variability of diffusion tensor imaging (DTI) tractography in pediatric epilepsy. Epilepsy & Behavior, 37, 116-122. View

Neurometabolites

tDCS changes neurometabolite concentrations

We found that certain brain metabolites found in the motor cortices of kids with perinatal stroke had different concentrations compared to control participants and changed after non-invasive brain stimulation (tDCS). Concentrations of some of these metabolites were also highly correlated with motor function.

Carlson HL, Ciechanski P, Harris AD, MacMaster FP, Kirton A (2018). Changes in spectroscopic biomarkers after transcranial direct current stimulation in children with perinatal stroke. Brain Stimulation, 11, 94-103. View

Spectroscopic biomarkers in kids with CP

Using magnetic resonance spectroscopy (MRS), we demonstrate that certain neurometabolites in the motor cortices of children with hemiparetic cerebral palsy are different compared to their peers. Concentrations of such neurometabolites are highly related to function, giving us a biomarker for brain plasticity after perinatal stroke.

Carlson HL, MacMaster FP, Harris AD & Kirton A (2017). Spectroscopic biomarkers of motor cortex developmental plasticity in hemiparetic children after perinatal stroke. Human Brain Mapping, 38(3), 1574-1587. View

Intervention Trials

High-definition tDCS in kids

We investigated whether high-definition transcranial direct current stimulation (HD-tDCS) can improve motor learning in children. We found enhanced motor learning effects in the trained hand but also significant spillover into the untrained hand suggesting generalization of improvements and thus potential efficacy as a rehabilitation intervention. 

Cole L, Giuffre A, Ciechanski P, Carlson HL, Zewdie E, Kuo H-C, Kirton A (2018). Effects of High-Definition and Conventional Transcranial Direct-Current Stimulation on Motor Learning in Children. Frontiers in Neuroscience, 12, 787. View

tDCS may improve motor function in kids with CP

The addition of transcranial direct current stimulation (tDCS) to intensive rehabilitation therapy may increase motor function in children with perinatal stroke and hemiparetic cerebral palsy.

Kirton A, Ciechanski P, Zewdie E, Anderson J, Nettel-Aguirre A, Carlson HL, Carsolio L, Herrero M, Quigley J, Mineyko A, Hodge J & Hill M (2017). Transcranial direct current stimulation for children with perinatal stroke and hemiparesis. Neurology, 88(3), 259-267. View

Treatment of dysphasia after childhood stroke

Intensive speech rehabilitation combined with repetitive transcranial magnetic stimulation can improve language function after childhood stroke. We report here associated multimodal imaging biomarkers.

Carlson HL, Jadavji Z, Mineyko A, Damji O, Hodge J, Saunders J, Hererro M, Nowak M, Patzelt R, Mazur-Mosiewicz A, MacMaster FP, Kirton A (2016). Treatment of dysphasia with rTMS and language therapy after childhood stroke: Multimodal imaging of plastic change. Brain & Language, 159, 23-34. View

Motor Mapping

Visualization of robotic motor mapping

A step-by-step visualized guide demonstrating how to perform transcranial magnetic stimulation (TMS) robotic motor mapping in children.

Giuffre A, Cole L, Kuo H-C, Carlson HL, Grab J, Kirton A & Zewdie E (in press). Non-invasive modulation and robotic mapping of motor cortex in the developing brain. Journal of Visualized Experiments. View

 

Robotic TMS mapping in kids

We aimed to use recently pioneered robotic TMS technology to develop an efficient, reproducible protocol to characterize cortical motor maps in a pediatric population. We demonstrated that motor map neurophysiology and its influence on developmental plasticity and therapeutic neuromodulation can be effectively explored in children.

Grab JG, Zewdie E, Carlson HL, Kuo H-C, Ciechanski P, Hodge J, Giuffre A & Kirton A. (2018). Robotic TMS mapping of motor cortex in the developing brain. Journal of Neuroscience Methods, 309, 41-54. View

Current Modeling

Current modeling during brain development

We used current modeling techniques to determine the strength and distribution of tDCS-induced electric fields (EF) in brains across the developmental period (6-43 years). We found large EF differences between children and adults that may be associated with age-related differences in skull and extra-axial space thickness, as well as developmental changes occurring in grey and white matter.

Ciechanski P, Carlson HL, Yu S & Kirton A (2018). Modeling transcranial direct-current stimulation-induced electric fields in children and adults. Frontiers in Human Neuroscience, 12, 268. View

Epilepsy and Stroke

Epileptiform discharges in sleep and cognition

We investigated whether sleep-potentiated epileptiform abnormalities are associated with worse developmental outcomes after perinatal stroke. We found that developmental outcome in language and behaviour in children with arterial perinatal stroke is associated with electrical status epilepticus in sleep and possibly treatment of EEG abnormalities can improve outcome.

Mineyko A, Qi W, Carlson HL, Bello-Espinosa L, Brooks BL & Kirton A (2017). Neuropsychological outcome in perinatal stroke associated with epileptiform discharges in sleep. The Canadian Journal of Neurological Sciences. 44(4), 358-365. View

Mild Traumatic Brain Injury

Cerebral perfusion differences post concussion

We examined cerebral blood flow (CBF) in children with different clinical recovery patterns following mild traumatic brain injury (mTBI). Symptomatic children had higher CBF. Children who "recovered" quickly, had decreased CBF suggesting that clinical recovery precedes the cerebral recovery.

Barlow KM, Marcil LD, Dewey D, Carlson HL, MacMaster FP, Brooks BL & Lebel RM (2017). Cerebral Perfusion changes in Post-Concussion Syndrome: A prospective controlled cohort study. Journal of Neurotrauma, 34(5), 996-1004. View