Holoprosencephaly is a brain development abnormality where the brain does not properly separate into the left and right hemispheres. This disorder also affects the development of the face as well as that of the head. Holoprosencephaly is categorized into four types with the level of severity being the distinguishing factor among the four classes.
From the least to most severe they include middle interhemispheric variant (MIHV), lobar, semi-lobar, and Alobar. Generally, you can tell the severity of the brain defect judging by the degree of the severity of the facial defect. As such, individuals that are most severely affected by Holoprosencephaly feature one central eye – the condition is referred to as cyclopia – and a tubular nasal structure – referred to as proboscis – which is located above the eye.
The less severe forms of these conditions feature a partially divided brain. The eyes are also set close together. Other common symptoms of Holoprosencephaly include pituitary gland disorders and intellectual disability. Holoprosencephaly can result from a mutation in any of some 14 different genes as well as chromosome abnormalities or teratogens (agents that cause birth defects). It could also be a subsequent consequence of various unique genetic syndromes.
1. Seizures
A seizure is described as the sudden and uncontrollable electrical disturbance inside the brain. This disturbance causes an individual to experience changes in their feelings, behavior, movement, and level of consciousness. A tendency to having recurrent seizures is referred to as epilepsy.
There are a variety of seizure types; all varying in severity. The different types of seizures are classified according to how and where they begin in the brain. A seizure typically lasts between half a minute to two minutes.
Focal seizures are as a result of abnormal electrical activity in a particular area within the brain and they may occur with or without loss of awareness or consciousness. The symptoms of a focal seizure are similar to that of a migraine.
A generalized seizure is one that appears to involve all parts of your brain and include: absence seizures, tonic seizures, atonic seizures, clonic seizures, and myoclonic seizures.
[nextpage title=“Next” ]2. Hydrocephalus
This is a condition characterized by the buildup of fluid in ventricles deep inside the brain. This excess fluid consequently causes excess pressure on the brain.
Typically, cerebrospinal fluid is supposed to flow through the ventricles and bathe the spinal column and brain. However, the pressure resulting from the excess cerebrospinal fluid as a result of hydrocephalus can cause damage to brain tissues as well as causing a range of brain function impairments.
Hydrocephalus can occur in people of all ages. However, it most commonly occurs in infants or adults over the age of 60. Surgical treatment is usually employed to restore and maintain the normal levels of cerebrospinal fluid in the brain.
The common signs of hydrocephalus in infants include:
• A bulging on top of the head
• A rapid increase in the size of the head
• A head that is unusually large.
[nextpage title=“Next” ]3. Neural Tube Defects
The neural tube is a structure that occurs early during the embryonic stage and is what gives rise to the CNS (central nervous system). Thus a neural tube defect (NTD) is the abnormal development of this structure.
NTDs are the leading cause of infant disabilities and deaths among birth defects. Note that all pregnancies are at risk of neural tube defects. If an NTD is not prevalent in the family history, the other common risk factor is type 1 diabetes in the mother. NTDs can be avoided if the mother consumes folic acid supplements during the earlier weeks of the pregnancy. Folic acid does not completely eliminate the possibility of developing an NTD and it is, therefore, important to undergo routine prenatal screening.
[nextpage title=“Next” ]4. Pituitary Dysfunction
The pituitary gland is the pea-sized organ that sits on the base of the brain and is referred to as the body’s ‘master gland.’ It is responsible for producing various hormones that are vital for certain body processes. Also, it stimulates other glands to produce their hormones.
The hormones produced by the pituitary gland include:
• Prolactin. Responsible for stimulating breast milk production.
• Growth Hormone. Responsible for stimulating growth during childhood.
• Adrenocorticotropin. Stimulates cortisol production. Cortisol is vital for our survival as it maintains blood sugar and blood pressure levels as well as enhancing our recovery after an injury or illness.
• Thyroid stimulating hormone. This hormone regulates our bodies’ metabolism.
A pituitary dysfunction implies the gland won’t perform the above functions properly which means the individual is likely to suffer from an inability to: grow, maintain blood glucose and pressure levels, recover from illnesses, and balance their metabolism.
[nextpage title=“Next” ]5. Extremely Short Stature
Extremely short stature is a direct consequence of growth hormone deficiency, which in turn, is caused by pituitary dysfunction.
Holoprosencephaly may cause the pituitary gland to develop poorly thus leading to a growth hormone deficiency.
Apart from extremely short stature, other signs of growth hormone deficiency include having younger and rounder faces and being chubby. Additionally, these individuals exhibit reduced bone strength as well as lacking stamina and constantly feeling tired. They also tend to have high levels of cholesterol and fat in their blood. This predisposes them to a greater risk of heart disease and diabetes.
[nextpage title=“Next” ]6. Feeding Problems
Most children with severe forms of Holoprosencephaly have a problem with feeding and swallowing. These issues are often linked to the child’s degree of motor impairment. Language and speech therapy, as well as putting a feeding tube (gastronomy tube) directly into the stomach, may assist in alleviating the feeding problems as well as reducing the risk of having the food accidentally find its way into the lungs instead of passing through the esophagus and into the stomach. If such an incident happens, the child will be at risk of developing recurring respiratory problems in addition to having a poor nutritional intake.
[nextpage title=“Next” ]7. Developmental Delays
Developmental delays refer to the delay in reaching the thinking, motor skills, and, language milestones.
Fine and gross motor skill delays are what you can use to tell whether there are any developmental delays in a child. Fine motor skills will involve small movements such as holding a crayon or toy. Gross motor skills involve larger movements such as throwing things or climbing stairs.
A typical healthy child should be able to raise their head by 3 months, sit up by 6, and walk well by their second birthday. Failure to achieve the above may be an indication of developmental delay as a result of Holoprosencephaly.
[nextpage title=“Next” ]8. Intellectual Disability
Holoprosencephaly typically causes intellectual disability in a child. This is because of improper brain development and, as such, their brains might not function within the required range of adaptive and intellectual functioning. Intellectual disability used to be known as mental retardation in the past.
The symptoms of intellectual disability may include:
• Sitting, crawling, and walking later than other children
• Issues with learning how to talk or speak
• Not meeting intellectual standards
• Lack of curiosity
• Memory issues
• Learning difficulties
• Inability to comprehend the consequence of their actions
• Tendency towards self-injury
• Passivity
• Dependency
• Attention seeking behavior
• Aggression
In the prediction and maximization of the prognosis of a child with Holoprosencephaly, sustained care by a specialist such as a pediatric neurologist is essential in providing a realistic and balanced prognosis that will allow for appropriate treatment.
