This is a pilot study of repetitive transcranial magnetic stimulation (rTMS) to test tolerance and efficacy in children who have hemiparesis from acquired or presumed perinatal stroke.

The investigators will begin to test the hypothesis that rTMS will be tolerated and will result in improved hand strength and mobility when compared with sham stimulation.

Aim 1: To determine whether 1 Hz rTMS applied to the hemisphere opposite the infarct (contralesional or healthy hemisphere) is tolerated by children ages 6-18 years who have chronic motor sequelae from a stroke.

Aim 2: To determine whether 8 sessions of inhibitory 1 Hz rTMS to the contralesional healthy hemisphere improves grip strength and hand mobility when compared with sham stimulation in controls.

Inclusion Criteria:

1. A history of ischemic or hemorrhagic stroke at least 6 months prior to recruitment, and causing current unilateral motor impairment of hand function (scoring 1-3 on a modified Ashworth scale; scale explained in Appendix).
2. Cerebral infarction spares the transcallosal pathways.
3. Cerebral injury confirmed by brain MRI or CT
4. Ages 6-18 years inclusive.

Exclusion Criteria:

1. The presence of an implanted device such as a pacemaker, vagal nerve stimulator, or recently implanted cardiovascular stent; arterial aneurysms; arteriovenous malformations; obstructive hydrocephalus.
2. Infarction of the cortical motor areas.
3. Presence of a brain tumor or suspected neurodegenerative disease.
4. Intractable epilepsy or a history of poorly controlled epilepsy.
5. Current use of medications that may lower seizure threshold (such as specific antipsychotics, specific antidepressants, amphetamines)
6. Hand function limited to rigid flexion or extension (score = 4 on the modified Ashworth scale)
7. Disorders causing hallucinations, delusions, or excessive anxiety or depression.
8. Pre-existing chronic pain syndromes including intractable headache and chronic daily headache.
9. Pregnancy.
10. Any sensorimotor or cognitive impairment that prevents valid responses on study measures.
11. Bilateral strokes (cerebral injuries) involving motor cortex and/or corpus callosum
12. All patients and parents must be naïve regarding the effects and sensations of rTMS (i.e., patients and/or parents with prior exposure to TMS will be excluded).
13. Subject has had a recent neurosurgical procedure involving the brain.
14. Subject suffered traumatic brain injury that places the subject at risk of seizures.