# Cerebral palsy

`````{admonition} Executive summary
:class: info

**Outcome:** Diagnosis of Spastic or Dyskinetic Cerebral Palsy

**Specific to HIE?**
* No - there are several possible causes

**Which infants with HIE?**
* Cerebral palsy is only one of the possible outcomes of fetal hypoxia, so excludes lots of other outcomes

**Any other benefits or caveats not already mentioned?**
* Diagnosis is often later in childhood, may be unlikely to be in neonatal datasets

**Conclusion:** Potentially recommended.  Spastic or dyskinetic Cerebral Palsy is an important outcome in the context of HIE. However, not all HIE cases will lead to cerebral palsy, and HIE is not the only possible cause of cerebral palsy.
`````

## Cerebral palsy

'Cerebral palsy (CP) is a neurologic disability affecting body movement, muscle tone, and posture'. It 'is caused by damage or developmental defects to the areas of the brain that control the movement of the body and coordination.'[[source]](https://www.birthinjuryhelpcenter.org/cerebral-palsy.html)

There are four types:
* **Spastic CP** - most common, due to cerebral cortex damage
* **Dyskinetic CP** (i.e. athetoid CP) - due to basal ganglia damage
* **Ataxic CP** - due to cerebelum damage
* **Mixed CP** - due to multiple areas of the brain being injury[[source]](https://www.cerebralpalsycymru.org/about-cerebral-palsy/what-is-cerebral-palsy/types-of-cerebral-palsy)

## Causes

'The abnormal development of the brain or damage that leads to CP can happen before birth, during birth, within a month after birth, or during the first years of a child’s life, while the brain is still developing.' It can be classified as:
* **Congenital CP** - if related to development/damage 'that occurred **before or during birth**' - this is the majority (85-90%)
* **Acquired CP** - if related to development/damage that occurred 'more than 28 days after birth' - usually 'an infection (e.g. meningitis) or head injury'[[source]](https://www.cdc.gov/ncbddd/cp/facts.html)

'Cerebral palsy is usually caused by a problem that affects the development of a baby's brain while it's growing in the womb. These include:
* Damage to part of the brain called white matter, possibly as a result of a reduced blood or oxygen supply – this is known as **periventricular leukomalacia** (PVL)[[source]](https://www.nhs.uk/conditions/cerebral-palsy/causes/)
* **Infections** - infections during pregnancy, labour and delivery, including viral infections (eg. rubella, cytomegalovirus) and parasitic infections (eg. toxoplasmosis) - as well as 'infections of the placental membranes and amniotic fluids (chorioamnionitis)'[sources [1](https://www.nhs.uk/conditions/cerebral-palsy/causes/) and [2](https://www.birthinjuryhelpcenter.org/cerebral-palsy.html)]
* A **stroke** – where there's bleeding in the baby's brain or the blood supply to their brain is cut off
* An **injury** to the unborn baby's head'[[source]](https://www.nhs.uk/conditions/cerebral-palsy/causes/)
* **Oxygen deprivation (asphyxia)** - a 'wide range of obstetrical complications and events during pregnancy can threaten the supply of oxygen to the baby's brain'[[source]](https://www.birthinjuryhelpcenter.org/cerebral-palsy.html)

Spastic cerebral palsy is associated with '**pre-term** delivery or **prolonged moderate-intensity hypoxic events** resulting in periventricular leukomalacia and diffuse white matter injury.' Dyskinetic cerebral palsy is 'associated with basal ganglia and thalamic injuries... usually seen with brief but **profound hypoxic insults**. Patients with dyskinetic CP are more commonly **term** infants versus those with spastic CP'.[[source]](https://www.ncbi.nlm.nih.gov/books/NBK563160/)

**Premature babies** 'are 30 times more likely to be diagnosed with cerebral palsy' - this is often because 'premature babies frequently experience brain haemorrhages and periventricular leukomalacia (PVL)', which cause brain damage that can lead to cerebral palsy.[[source]](https://www.birthinjuryhelpcenter.org/cerebral-palsy.html)

'Cerebral palsy is one of the most costly neurologic disabilities because of its frequency (2/1000 births) and persistence over the life span.'[[source]](https://doi.org/10.1016%2Fj.clp.2009.07.011)

## Statistics

*The two studies below seem like good references.*

Proportion of infants with HIE who go on to have CP:
* Zhang et al. 2020 conducted a meta-analysis of 10 studies, and found the rate of CP in infants with HIE was 20.3% in RCTs and 22.2% in observational studies. Comparing infants who did and did not receive treatment, rates were 17.3% in the treated group and 23.9% in the untreated group[[source]](https://doi.org/10.3389%2Ffneur.2020.00704)

Proportion of infants with CP caused by HIE:
* Ellenberg and Nelson 2012 identified 23 studies from 1986 to 2010, and found that the proportion of CP with birth asphyxia as a precusor varied from less than 3% to over 50%.
    * The studies were hetergeneous in many regards, including in their definitions for birth asphyxia and the outcome of CP.
    * 'The very high case exposure rates linking birth asphyxia to CP can probably be attributed to several factors: the fact that the clinical picture at birth cannot specifically identify birth asphyxia; the definition of CP employed; and confusion of proximal effects - results - with causes.'
    * They recommend that if the role of birth asphyxia as an initiating factor on the causal pathway to CP is to be correctly assessed, a surrogate must be used that is relatively specific to birth asphyxia and not itself an early symptom of the developing disorder. They state that birth asphyxia is not defined based on signs of early brain injury (e.g. neonatal seizures, neonatal encephalopathy) or clinical signs that can result from a variety of etiologic factors (e.g. abnoraml FHR, meconium in amniotic fluid) - and that instead it is just based on the occurence of sentinel events like uterine rupture, major placental abruption, or cord prolpase[[source]](https://doi.org/10.1111/dmcn.12016)