The incidence of perinatal stroke is relatively common, as high as 1 in 2,300 births, but little is known about the resulting changes in the brain that eventually manifest as cerebral palsy (CP). Motor signs that indicate the infant is beginning to develop CP often do not become evident for several months after the diagnosis of perinatal stroke which delays therapy. The main purpose of this study is to examine early brain reorganization in infants 3-12 months of age corrected for prematurity with perinatal stroke using magnetic resonance imaging (MRI) and non-invasive transcranial magnetic stimulation (TMS). In addition, the association between the brain reorganization and motor outcomes of these infant participants will be identified.

In this study, the MRI scans will include diffusion tensor imaging (DTI) - an established method used to investigate the integrity of pathways in the brain that control limb movement. Infants will be scanned during nature sleeping after feeding. The real scanning time will be less than 38 minutes. TMS is a painless, non-surgical brain stimulation device which uses principles of electromagnetic induction to excite cortical tissue from outside the skull. Using TMS as a device to modulate and examine cortical excitability in children with hemiparetic CP and in adults has been conducted previously.

In this infant study, we will assess cortical excitability from the motor cortex of both the ipsilesional and contralesional hemispheres under the guidance of a frameless stereotactic neuronavigation system. Additionally, the investigators will assess infants' movement quality using an age-appropriate standardized movement assessment. This will allow the investigators to examine the relationship between measures of motor pathway integrity and early signs of potential motor impairment. We will longitudinally follow enrolled infants, and complete repeat assessments at 12- and 24-months corrected age to assess how infants develop over time after perinatal stroke. The remote follow-up will occur at 5 years or less.

Understanding the early brain reorganization before the brain has not yet largely reorganized is critical for developing efficacious early intervention. As a unique aspect of investigation, this study will combine Magnetic Resonance Imaging (MRI)/ Diffusion Tensor Imaging (DTI) and TMS to provide an additional opportunity to assess both the cortical excitability and corticospinal tract (CST) integrity in infants with perinatal stroke.

Identifying the association between laboratory assessment results and developmental outcomes is also critical. This study is to use MRI/DTI and TMS to comprehensively examine both the CST integrity and cortical excitability in infants following perinatal stroke, and to identify association with motor outcome as evaluated by movement assessment.

Inclusion Criteria for Pilot Study:

• Birth diagnosis of unilateral perinatal stroke by cranial ultrasound, computer tomography (CT) or magnetic resonance imaging (MRI)
• Corrected gestational age between 3 and 24 months of age for both infants with stroke and typically developing infants

Exclusion Criteria for Pilot Study :

• Metabolic Disorders
• Neoplasm
• Disorders of Cellular Migration and Proliferation
• Acquired Traumatic Brain Injury
• Received surgeries that may constraint current spontaneous movements
• Indwelling metal or incompatible medical devices
• Received surgeries that may constraint current spontaneous movements
• Other neurologic disorders unrelated to stroke
• Small for gestational age (SGA): Infants are smaller in size than normal for the gestational age
• Apneic episodes and syncope (known heart defects) for the safety of participants in the stud.
• Genetic disorders
• Uncontrolled seizures

Additional Inclusion Criteria for Follow-up Study:

- Previous participation in pilot study

Additional Exclusion Criteria for Follow-up Study:

- Lack of wireless internet access or computer to participate in virtual Zoom call

The pilot study portion will recruit infants with unilateral perinatal stroke between 3 to 5 months of corrected age to understand their brain reorganization after stroke.

The follow-up study portion will recruit children aged 5 years or younger who have been diagnosed with perinatal stroke and who participated in the pilot study.

All participants are included in these analyses.

Recording of adverse events will take place during TMS cortical mapping and MRI scanning of infants with perinatal stroke. Assessment of vital signs changes and pain/stress responses during both MRI and TMS assessment during visit 1 and visit 2.