If someone is suspected of having polioencephalitis a sample of throat secretions, stool or cerebrospinal fluid is checked for the virus. Blood tests can be done to detect antibodies against viral antigens and foreign proteins. Virus isolation is the most sensitive method and it is most likely to be isolated from stool samples. Once isolated, RT-PCR is used to differentiate naturally occurring strains from vaccine-like strains.

The virus is most often spread by person to person contact with the stool or saliva of the infected person. Two types of vaccines have been developed to prevent the occurrence and spread of the poliomyelitis virus. The first is an inactivated, or killed, form of the virus and the second is an attenuated, or weakened, form of the virus. The development of vaccines has successfully eliminated the disease from the United States. There are continued vaccination efforts in the U.S. to maintain this success rate as this disease still occurs in some areas of the world.

Because the causes of CP are varied, a broad range of preventative interventions have been investigated.

Electronic fetal monitoring has not helped to prevent CP, and in 2014 the American College of Obstetricians and Gynecologists, the Royal Australian and New Zealand College of Obstetricians and Gynaecologists, and the Society of Obstetricians and Gynaecologists of Canada have acknowledged that there are no long-term benefits of electronic fetal monitoring. Prior to this, electronic fetal monitoring was widely used to prop up obstetric litigation.

In those at risk of an early delivery, magnesium sulphate appears to decrease the risk of cerebral palsy. It is unclear if it helps those who are born at term. In those at high risk of preterm labor a review found that moderate to severe CP was reduced by the administration of magnesium sulphate, and that adverse effects on the babies from the magnesium sulphate were not significant. Mothers who received magnesium sulphate could experience side effects such as respiratory depression and nausea. Caffeine is used to treat apnea of prematurity and reduces the risk of cerebral palsy in premature babies, but there are also concerns of long term negative effects. A moderate level of evidence has been shown for giving women antibiotics during preterm labour when their waters had not broken was associated with an increased risk of cerebral palsy in the child. Additionally, allowing a preterm birth to proceed rather than trying to delay the birth also had a moderate level of evidence for increased risk of cerebral palsy in the child.

Cooling high-risk full-term babies shortly after birth may reduce disability, but this may only be useful for some forms of the brain damage that causes CP.

Diagnosis of Wernicke–Korsakoff syndrome is by clinical impression and can sometimes be confirmed by a formal neuropsychological assessment. Wernicke's encephalopathy typically presents with ataxia and nystagmus, and Korsakoff's psychosis with anterograde and retrograde amnesia and confabulation upon relevant lines of questioning.

Frequently, secondary to thiamine deficiency and subsequent cytotoxic edema in Wernicke's encephalopathy, patients will have marked degeneration of the mamillary bodies. Thiamine (vitamin B) is an essential coenzyme in carbohydrate metabolism and is also a regulator of osmotic gradient. Its deficiency may cause swelling of the intracellular space and local disruption of the blood-brain barrier. Brain tissue is very sensitive to changes in electrolytes and pressure and edema can be cytotoxic. In Wernicke's this occurs specifically in the mammillary bodies, medial thalami, tectal plate, and periaqueductal areas. Sufferers may also exhibit a dislike for sunlight and so may wish to stay indoors with the lights off. The mechanism of this degeneration is unknown, but it supports the current neurological theory that the mammillary bodies play a role in various "memory circuits" within the brain. An example of a memory circuit is the Papez circuit.

The diagnosis of cerebral palsy has historically rested on the person's history and physical examination. A general movements assessment, which involves measuring movements that occur spontaneously among those less than four months of age, appears to be most accurate. Children who are more severely affected are more likely to be noticed and diagnosed earlier. Abnormal muscle tone, delayed motor development and persistence of primitive reflexes are the main early symptoms of CP. Symptoms and diagnosis typically occur by the age of 2, although persons with milder forms of cerebral palsy may be over the age of 5, if not in adulthood, when finally diagnosed. It is a developmental disability.

Once a person is diagnosed with cerebral palsy, further diagnostic tests are optional. Neuroimaging with CT or MRI is warranted when the cause of a person's cerebral palsy has not been established. An MRI is preferred over CT due to diagnostic yield and safety. When abnormal, the neuroimaging study can suggest the timing of the initial damage. The CT or MRI is also capable of revealing treatable conditions, such as hydrocephalus, porencephaly, arteriovenous malformation, subdural hematomas and hygromas, and a vermian tumour (which a few studies suggest are present 5–22% of the time). Furthermore, an abnormal neuroimaging study indicates a high likelihood of associated conditions, such as epilepsy and intellectual disability. There is a small risk associated with sedating children in order to take a clear MRI.

The age at which CP is diagnosed is important, but there is disagreement over what is the best age to make the diagnosis. The earlier CP is diagnosed correctly, the better the opportunities are to provide the child with physical and education help, but there might be a greater chance that CP will be confused with another problem, especially if the child is 18 months of age or younger. Infants may have temporary problems with muscle tone or control that can be confused with CP, which is permanent. A metabolism disorder or tumors in the nervous system may appear to be CP; metabolic disorders, in particular, can produce brain problems that look like CP on an MRI. Disorders that deteriorate the white matter in the brain and problems that cause spasms and weakness in the legs, may be mistaken for CP when they first appear early in life. However, these disorders get worse over time, and CP does not (although it may change in character). In infancy it may not be possible to tell the difference between them. In the UK, not being able to sit independently by the age of 8 months is regarded as a clinical sign for further monitoring. Fragile X syndrome (a cause of autism and intellectual disability) and general intellectual disability must also be ruled out. Cerebral palsy specialist John McLaughlin recommends waiting until the child is 36 months of age before making a diagnosis, because by that age, motor capacity is easier to assess.

As described, Korsakoff 's syndrome usually follows or accompanies Wernicke's encephalopathy. If treated quickly, it may be possible to prevent the development of Korsakoff's syndrome with thiamine treatments. This treatment is not guaranteed to be effective and the thiamine needs to be administered adequately in both dose and duration. A study on Wernicke-Korsakoff's syndrome showed that with consistent thiamine treatment there were noticeable improvements in mental status after only 2–3 weeks of therapy. Thus, there is hope that with treatment Wernicke's encephalopathy will not necessarily progress to WKS.

In order to reduce the risk of developing WKS it is important to limit the intake of alcohol or drink in order to ensure that proper nutrition needs are met. A healthy diet is imperative for proper nutrition which, in combination with thiamine supplements, may reduce the chance of developing WKS. This prevention method may specifically help heavy drinkers who refuse to or are unable to quit.