Tuesday, June 2, 2015

30 Days to Bee Hydranencephaly Aware: Outlook = Poor

Day two of #30DaystoBEEhydranencephalyaware tackles one of the greatest misconceptions - that is delivered by unknowing medical professionals who often "google" the condition since they have such little first-hand knowledge of hydranencephaly. 

"The medical text prognosis for children with hydranencephaly, which is often given to families upon diagnosis, states: 'The outlook for children with hydranencephaly is generally poor, and many children with this disorder die before age 1. However, in rare cases, children with hydranencephaly may survive for several years or more.' The reality is reversed, that rarely does a child with this diagnosis die within the first year.

GHF is struggling to have the formal medical diagnosis altered to reflect the reality, but we have successfully changed the definition across the web in hopes of families facing the decision to give up on their child far too soon.

You can read the definition as we have reworded it in several places around the web and even in print publications, thanks to some amazing opportunities we have been presented with to author updates to various publications that recognize the outdated medical text. A couple of those places:

Pediatric Brain Foundation 
Disabled World 

The full definition, as we have submitted, has been challenged more times than I can count by medical professionals who argue that our definition is far too optimistic to be the reality of the condition. What are your thoughts?

Hydranencephaly, synonym hydroanencephaly (NORD, 2007). Hydranencephaly is a rare congenital abnormality characterized by the absence and replacement of the cerebral hemispheres with cerebrospinal fluid. It was first described by Cruveilher (1892) as “Anencephalie hydrocephalique” or “Hydroanencephalie”1. Crome and Sylvester then reviewed the disease and defined it as a congenital condition2. It is an extremely rare and unique abnormality occurring in less than 1 per 10,000 births worldwide3. It is also said to be present in 0.2% of infant autopsies, and approximately 1% of babies diagnosed clinically as hydrocephalus4. It is critical to differentiate between hydranencephaly and extreme hydrocephalus as the latter carries a potentially better prognosis5.

Hydranencephaly, synonym hydroanencephaly (NORD, 2007), is one of the various cephalic classification types of disorders. These disorders are congenital conditions that derive from either damage to, or abnormal development of, the fetal nervous system in the earliest stages of development in utero. Cephalic is the medical term for “head” or “head end of body.” These conditions do not have any definitive identifiable cause factor; instead generally attributed to a variety of hereditary or genetic conditions, but also by environmental factors such as maternal infection, pharmaceutical intake, or even exposure to high levels of radiation (NINDS, 2007). This condition possesses isolated occurrences, affecting less than 1 in 10,000 births worldwide (Kurtz & Johnson, 1999) and officially classifying hydranencephaly as a rare disorder by affecting fewer than 1 in 200,000 in the United States (Rare, 2011). Even rarer are cases of hemihydranencephaly, in which the effects of damage are unilateral and existing only on one hemisphere of the brain (Dubey, Gobinathan, et.al, 2002).

Many children live for an extended period prior to diagnosis due to no obvious symptomatic presentation at birth. Though hydranencephaly is typically a congenital disorder, it can occur as a postnatal diagnosis in the aftermath of meningitis, intracerebral infarction, and ischemia (stroke), or other traumatic brain injury (Dubey, Gobinathan, et.al, 2002).

Hydranencephaly is an extreme form of porencephaly (another rare disorder of the central nervous system which involves the existence of a cyst or cavity within the cerebral hemisphere) in which the cerebral hemispheres are absent and replaced by sacs filled with cerebrospinal fluid (NINDS, 2007) and remains the most severe form of bilateral cerebral cortical destruction. Differential diagnoses include bilaterally symmetric schizencephaly (a less destructive developmental process on the brain), severe hydrocephalus (cerebrospinal fluid excess within the skull), and alobar holoprosencephaly (a neurological developmental anomaly). Once destruction of the brain is complete, the cerebellum, midbrain, thalami, basal ganglia, choroid plexus, and portions of the occipital lobes typically remain preserved to varying degrees. 

Though the cerebral cortex is absent, in most cases the fetal head remains enlarged due to the continued production by the choroid plexus of cerebrospinal fluid that is inadequately reabsorbed causing increased intracranial pressure (Kurtz & Johnson, 1999). 

Although the exact cause of hydranencephaly remains undetermined in most cases, the most likely general cause is by vascular insult such as stroke or injury, intrauterine infections, or traumatic disorders after the first trimester of pregnancy (NINDS, 2007). In a number of cases where intrauterine infection was determined the causing factor, most involved toxoplasmosis and viral infections such as enterovirus, adenovirus, parvovirus, cytomegalic, herpes simplex, Epstein-Barr, and syncytial viruses. 

Another cause factor is determined to be monochorionic twin pregnancies, involving the death of one twin in the second trimester, which in turn causes vascular exchange to the living twin through placental circulation through twin-to-twin transfusion, causing hydranencephaly in the surviving fetus (Kurtz & Johnson, 1999). One medical journal reports hydranencephaly as an autosomal inherited disorder with an unknown mode of transmission, where an unknown blockage of the carotid artery where it enters the cranium causes obstruction and damage to the cerebral cortex. As a recessive genetic condition, both parents must carry the asymptomatic gene and pass it along to their child, a chance of roughly 25 percent. Despite determination of cause, hydranencephaly inflicts both males and females in equal numbers (NORD, 2007).

An accurate, confirmed diagnosis is generally impossible until after birth, though prenatal diagnosis using fetal ultrasonography (ultrasound) can identify characteristic physical abnormalities that exist. Through thorough clinical evaluation, via physical findings, detailed patient history, and advanced imaging techniques, such as angiogram, computerized tomography (CT scan), magnetic resonance imaging (MRI), or more rarely transillumination (shining of bright light through the skull) after birth are the most accurate diagnostic techniques (NORD, 2007). However, diagnostic literature fails to provide a clear distinction between severe obstructive hydrocephalus and hydranencephaly, leaving some children with an unsettled diagnosis (Dubey, Gobinathan, et.al, 2002).

Unfortunately, contrary to many other associated diagnoses, hydranencephaly carries a lesser positive prognosis and method of effective management. The outlook for children diagnosed with hydranencephaly is generally determined to be poor, with death occurring before the age of one (NINDS, 2007). Medical text identifies that hydranencephalic children simply have only their brain stem function remaining (Kurtz & Johnson, 1999) thus leaving formal treatment options as symptomatic and supportive. Severe hydrocephalus causing macrocephaly, a larger than average head circumference, can easily be managed by placement of a shunt (NINDS, 2007) and oftentimes displays a misdiagnosis of another lesser variation of cephalic condition (Kurtz & Johnson, 1999). Plagiocephaly, the asymmetrical distortion of the skull, is another typical associated condition that is easily managed through positioning and strengthening exercises to prevent torticollis, a constant spasm or extreme tightening of the neck muscles (Parker & Parker, 2002).

Though medical research exclusive to hydranencephaly is limited, there are research efforts in the realm of neural tube defects and prevention of congenital neurological conditions. We encourage you to research all aspects of the condition prior to settling on one aspect of the diagnosis. 

No comments:

Post a Comment

We love to hear from our audience - share your comments with us here or join us on Facebook!