- 1 Encephalocele Definition
- 2 What is an Encephalocele?
- 3 What is a Brain Encephalocele?
- 4 What is Occipital Encephalocele?
- 5 What is Anterior Encephalocele?
- 6 What Causes Encephaloceles?
- 7 How is Encephalocele Detected and Diagnosed?
- 8 Encephalocele Repair
- 9 Encephalocele Prognosis
- 10 Occipital Encephalocele Survival Rate
An encephalocele is a sac-like hernial protrusion of part of the brain through an opening in the skull. The word is derived from the Greek enkephalos meaning “brain” and kele indicating “hernia”.
What is an Encephalocele?
This condition is a birth defect, one of several referred to as neural tube defects. It is generally considered to originate during the first month of pregnancy at the time when the brain and spinal cord become fully encapsulated within a strong tube-like structure, hence the name neural tube defect. In some cases, this closure is incomplete.
Perhaps the best-known example of a neural tube defect is the condition spina bifida in which the problem occurs in the lower spine. In the case of chiari malformation brain tissue protrudes into the spinal canal. The term encephalocele however is reserved for protrusions of the brain through openings in the skull.
It is well known that the skull is composed of various different bones which grow together and ossify as the embryo develops into a foetus and the ossification is normally almost complete at the time of parturition although the skulls of newborn babies inevitably still have a “soft spot”. Unfortunately, there are cases where the bones of the skull fail to properly join together resulting in openings almost invariably along the centre-line of the skull. These openings then allow for parts of the brain to protrude.
In the case of normal development, the brain is constrained within the cranial cavity but where openings are present there is no such constraint and it can grow unhindered. Encephaloceles can occur anywhere along this central line and may be found at the rear of the head, occipital encephalocele, the top of the head, or at the front of the head, often occurring around the position where the nose meets the forehead. These anterior encephaloceles are usually given more specific names depending on their precise location such as nasofrontal, nasoethmoidal or naso-orbital but in practice there can be a degree of overlap between such descriptions.
What is a Brain Encephalocele?
Despite the rarity of this condition, encephaloceles are known by many different names. The name brain encephalocele is easily understood but in reality the word brain is actually superfluous as encephalo- already refers to the involvement of the brain. The condition is also commonly referred to as: cranium bifidum, craniocele, cephalocele and encephalomyeloceles. In cases where the hernia does not contain any brain matter, being filled with meninges and cerebrospinal fluid, it may be referred to as meningoencephocele.
What is Occipital Encephalocele?
The posterior or occipital encephalocele, is numerically the most common type estimated to account for around 80% of all cases. Females are slightly more likely to have this condition than males. Genetics may also play a part and in the western hemisphere, this is the prevalent form of encephalocele whereas in eastern Asia, the anterior form is more often encountered. Encephaloceles of this type can be very large, in some cases even larger than the baby’s head. The head by comparison may be unusually small. The actual amount of brain matter present within the encephalocele is not necessarily directly related to its size but this location does give rise to problems of the nervous system which should not be underestimated. Hydrocephalus (water on the brain) may accompany this condition in newborn babies. Other problems may include spastic paraplegia (weakness of the arms and legs), delayed growth and development, intellectual impairment, seizures, vision problems and poor coordination. Corrective surgery is usually possible but in many cases, the symptoms may persist even after surgery.
The actual amount of brain matter present within the encephalocele is not necessarily directly related to its size but this location does give rise to problems of the nervous system which should not be underestimated. Hydrocephalus (water on the brain) may accompany this condition in newborn babies. Other problems may include spastic paraplegia (weakness of the arms and legs), delayed growth and development, intellectual impairment, seizures, vision problems and poor coordination. Corrective surgery is usually possible but in many cases, the symptoms may persist even after surgery.
What is Anterior Encephalocele?
As its name suggests, anterior encephalocele affects the front of the skull. In this case, the opening is often located near to the upper part of the nose resulting in a growth on the face. Due to the complex nature of the bones in this area, surgical removal can prove extremely challenging. The good news is that encephaloceles of this type do not normally contain any brain matter, being comprised of cerebrospinal fluid and meninges. Problems affecting the nervous system are rare and the success rate of such surgery is close to 100%.
What Causes Encephaloceles?
There is no simple answer as to what causes this rare condition. There are suggestions that some toxins or infections may increase the probabilities and some anti-seizure medications could also play a part. It is known that some vitamin deficiencies (folic acid) can increase spina bifida risks and so these factors may also be relevant to encephaloceles. Family history could also be considered with an increased risk if previous cases of spina bifida or anencephaly have occurred. Other conditions often accompany encephaloceles such as a cleft palate or hydrocephalus and 13 to 44% also have a chromosonal abnormality. In short, there is no way to predict or prevent this distressing condition.
How is Encephalocele Detected and Diagnosed?
In most cases, encephaloceles are detected during routine scans. In severe cases, a termination of the pregnancy may be regarded as the kindest measure. It must be pointed out that this serious condition means that few of the affected infants survive a full-length pregnancy with around 80% being stillborn. Of the 20% that are born alive, half perish shortly afterwards. Of those that do survive, diagnosis is usually immediately obvious but in some relatively minor encephaloceles, the hernia may be hidden such as in the nasal cavity and may evade detection at the time of birth.
The surgical repair of an encephalocele is usually performed within the first four months of the child’s life. It is rarely carried out immediately after birth and is usually only done so when there is a lack of skin covering or membranes posing a grave risk of infections or brain dehydration. Each case is different but the general procedure includes a craniotomy (opening of the skull), repositioning of the herniated matter back into place and closing the offending opening using bone or synthetic structural materials.
This is a serious condition and without treatment prognosis is poor. Even following a successful surgical repair, the prognosis must remain guarded. With many types of encephaloceles, the symptoms, as described above, may persist and cause lifelong disability. Frontal encephaloceles rarely give rise to long-term nervous system problems but, due to their position, can cause facial problems such as nose lengthening which can persist after encephalocele removal requiring further surgery at a later date.
Occipital Encephalocele Survival Rate
Occiptal encephaloceles are considered to offer a fairly poor prognosis with lasting ill-effects being the norm rather than the exception. The survival rate is often quoted as being around 55% but in reality the majority of these affected babies die before birth and, due to the severity of their condition, around 50% of the live births suffer neonatal deaths. This condition is often accompanied by other equally serious disorders and, where successful treatment is impossible, it is sometimes sadly the only option to offer palliative care to prevent any unnecessary suffering. Of those who survive, around 75% suffer some degree of mental impairment. There are of course notable exceptions and full and complete recoveries have been recorded so it is always sensible to hope for the best but be prepared for a less than perfect outcome.