Hemiplegic cerebral palsy affects movement and muscle tone on one side of the body. Often linked to perinatal stroke or one-sided brain injury, it produces asymmetric motor patterns, with one arm or leg significantly weaker than the other.
Hemiplegic cerebral palsy affects one side of the body, and it is the pattern with the most treatment evidence behind it. A meta-analysis of 42 randomized trials covering 1,454 children with unilateral cerebral palsy exists precisely because this group can be studied in a way bilateral patterns cannot: the other arm is the control.
European registers record it as unilateral spastic cerebral palsy, which puts it in the same category as a single affected limb and separates it from quadriplegic CP. That grouping is not bureaucratic. Everything below follows from one side working and the other not.
For where this sits among the rest, see the parent guide to the four main types of cerebral palsy and the overview of spastic cerebral palsy.
A focal injury to one side of the brain, producing weakness on the opposite side of the body. Of the cerebral palsy types, this is the one most often traceable to a single identifiable event.
Arterial ischemic stroke around the time of birth is the cause most specifically associated with this pattern. A clot or a blocked vessel starves one territory of the brain, the damage is focal rather than diffuse, and the resulting impairment lands on the opposite side. Other routes reach the same place: oxygen deprivation where the insult is focal rather than global, bleeding or infection in the newborn period, asymmetric white matter injury after premature birth, and malformations such as a cortical dysplasia formed while the brain was still developing.
Imaging usually confirms it. A systematic review found abnormal MRI in 334 of 388 children with cerebral palsy, 86%, with the pattern indicating when the injury occurred in 83% of them. The causes of cerebral palsy as a whole are covered separately.
Cerebral palsy is defined by an injury to the developing brain rather than by inheritance, so genetic factors belong here as susceptibility rather than cause. The one place they earn specific attention is clotting: an inherited thrombophilia is worth asking about where a perinatal stroke has been identified, because it changes what a family is told about future pregnancies. Testing sometimes returns a different diagnosis entirely, and a few of the conditions that imitate cerebral palsy early have treatments that cerebral palsy does not.
The recognized perinatal contributors are these:
One side is stiff and slow and the other works normally, which sounds like the milder situation and creates its own specific problem.
Spasticity on the affected side is velocity dependent: move the limb slowly and it can feel close to normal, move it quickly and it catches. The arm typically sits with the thumb into the palm, the forearm turned in and the wrist flexed. The leg produces toe walking on that side and a gait that grows more asymmetric the faster the child moves. Reflexes are brisk. The affected limbs are often visibly smaller, because a limb used less grows shorter and thinner, and that gap tends to widen through childhood rather than close.
The specific problem is what the good side does. It is faster at everything, so it does everything, and the affected hand drops out of the movement repertoire even where it could still contribute. That pattern, sometimes called developmental disregard, is why the arm is harder to treat than the leg: walking forces a leg into use every day, and nothing forces a hand. It is also what the main treatments below are designed to interrupt. The presentation is quite different from dyskinetic CP, where the problem is involuntary movement rather than stiffness.
Three things travel with this pattern often enough to be worth screening for rather than waiting to notice.
The sensory point is the one most often missed. A hand that cannot feel where it is will be used less regardless of how strong it becomes, and knowing that changes what a therapy plan should be aiming at.
A strong hand preference before the first birthday is the single most useful early sign, and it is the one most often explained away as early handedness.
Typical infants use both hands. A baby who consistently reaches with one and neglects the other before twelve months is usually showing weakness on the neglected side rather than precocious dexterity, and that observation is worth a referral on its own.
Beyond it, cerebral palsy can now be identified early with standardized tools. The 2017 international clinical practice guideline in JAMA Pediatrics found that before five months corrected age, term-age MRI detects risk at 86% to 89% sensitivity, the Prechtl Qualitative Assessment of General Movements at 98%, and the Hammersmith Infant Neurological Examination at 90%. The same guideline notes that topography, which is exactly the question of whether an impairment is one-sided, is harder to establish that early. See how cerebral palsy is diagnosed for the full workup and the role of MRI for the imaging side.
A child with hemiplegia usually walks, which places them at GMFCS level I or II, and that rating says almost nothing about the arm. The Manual Ability Classification System is the scale that does, grading how a child handles objects in daily life across five levels and validated for ages 4 to 18. Asking for both is reasonable, and a plan built only on the gross motor level will systematically underweight the hand.
One reassurance belongs here too. Hip displacement, which dominates management at the severe end of cerebral palsy, was found in 0% of children at GMFCS level I in a Swedish population study of 212 children, against 64% at level V. The surveillance that matters so much in quadriplegic CP is a smaller concern here.
This is the best-evidenced corner of cerebral palsy treatment, and the headline finding is not the one usually quoted. Dose matters more than method.
A meta-analysis published in Pediatrics in 2014 pooled 42 randomized or comparison trials evaluating 113 upper limb approaches in 1,454 children with unilateral cerebral palsy. Constraint-induced movement therapy, which restrains the stronger hand so the weaker one has to work, produced modest to strong effects on the movement quality and efficiency of the impaired arm compared with usual care. Set against an equal dose of bimanual training, where both hands work together on a task, the two produced similar outcomes.
Two further findings from the same review are worth as much. Goal-directed home programs had strong evidence behind them, which matters because that is the part a family runs. And block therapy on its own was judged unlikely to deliver enough dose to produce sustained change, which is a direct comment on how therapy is usually funded.
Occupational therapy carries most of the arm work, setting specific tasks a child wants to be able to do and working backwards to the movements they require. Physical therapy takes the leg, where the ankle is usually the limiting factor and a heel that will not reach the floor drives most of the gait problem.
Across 42 trials and 1,454 children with unilateral CP:
Where spasticity in the affected limb is limiting function, the options are local rather than systemic, because only one side is involved.
Oral antispastic medications fit this pattern poorly, since dosing a whole body to reach one side buys sedation for a benefit confined to two limbs. Antiseizure medication is a separate question and follows the epilepsy rather than the cerebral palsy.
Hemiplegic CP is often linked to perinatal stroke, oxygen deprivation, or trauma around the time of birth. When these events were preventable, families may have a cerebral palsy medical malpractice claim. Our team can review the case at no cost. Request a free case review.
Cerebral palsy affecting one side of the body, recorded in European registers as unilateral spastic CP. One hemisphere carries a focal injury and the weakness appears on the opposite side, so the arm and leg on that side are stiff and slow while the other side works normally.
Clinically, and the most useful early sign is a strong hand preference before the first birthday, which usually means weakness on the neglected side rather than early handedness. Before five months corrected age, term MRI detects risk at 86% to 89% sensitivity, the Prechtl General Movements Assessment at 98%, and the Hammersmith Infant Neurological Examination at 90%.
A focal injury to one side of the brain. Arterial ischemic stroke around the time of birth is the cause most specifically associated with this pattern, alongside focal oxygen deprivation, neonatal bleeds or infection, asymmetric white matter injury after preterm birth, and malformations formed during brain development.
For the arm, constraint-induced movement therapy or bimanual training. A meta-analysis of 42 trials covering 1,454 children with unilateral cerebral palsy found constraint therapy beat usual care, and matched for hours, bimanual training produced similar results, so dose matters more than which method is used. Goal-directed home programs carried strong evidence. Botulinum toxin, splinting and orthopedic surgery address spasticity locally.
Most walk and most live independent adult lives. Across cerebral palsy as a whole, two in three people will walk, three in four will talk, and one in two have normal intelligence, and hemiplegia sits at the milder end of the motor spectrum. Hip displacement, which dominates care at the severe end, was found in 0% of children at GMFCS level I in a Swedish population study.
Because the stronger side takes over. The good hand is faster at everything so it does everything, and the affected hand drops out of use even where it could contribute. That pattern is what constraint and bimanual therapy are designed to interrupt, and it is easier to interrupt before it becomes a habit.
It is unilateral, which is the whole distinction. Quadriplegic CP involves all four limbs and the trunk, dyskinetic CP produces involuntary movement rather than stiffness, and hemiplegia leaves one side working normally. That intact side is also why this pattern has more treatment evidence than any other: it provides the comparison.
Kelsey is an experienced surgical nurse who works extensively with pediatric patients and families navigating birth injuries and cerebral palsy diagnoses. She is licensed by the Missouri Board of Nursing and operates under the Nurse Licensure Compact, allowing her to practice across compact-member states. As both a mentor and patient advocate, Kelsey focuses on safety, communication, and compassionate care: helping families understand medical procedures, treatment options, and the realities of pediatric conditions.
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