Leonardo I. Valentin, MD, Luis Rodriguez-Ruiz, MD
Department of Obstetrics and Gynecology, Department of Radiology, Ponce School of Medicine and Health Sciences, Ponce, PR, USA.

Abstract
We present a case of alobar holoprosencephaly, a complex human brain malformation, identified by obstetric sonogram at 23 weeks gestation in a G1P0 mother. Alobar holoprosencephaly is recognized as the most severe variant of the condition within the entire spectrum of holoprosencephaly. Fetal karyotype analysis was performed, which showed a fetus with an abnormality on chromosome 17. Two infectious processes, during the first trimester of pregnancy, were environmental risk factors identified. At the time of this report gestation was in progress and further genetic studies were pending. To our knowledge this case presents a unique association of environmental risk factors and a genetic abnormality never reported in a case of alobar holoprosencephaly.

Case Report
We present the findings of a screening fetal ultrasound performed at 23 weeks gestation in 23 years old, grava 1, para 0 patient. Patient reported a negative past medical history negative except for gastroesophageal reflux disease and allergic rhinitis. Patient denied use of alcohol, tobacco or illicit drugs. In addition, no significant family history was present for genetic disease or congenital anomalies. Screening for sexually transmitted disease was negative.
The prenatal history for this patient was positive for two infectious processes early in pregnancy. For the first visit, retrospectively calculated at 2 weeks gestational age, the patient came to clinic reporting sore throat and ear discomfort for which patient was evaluated and treated with oral antibiotics. Next visit was at 6 weeks gestational age—during which pregnancy was confirmed with a ß-hCG—in which patient reported generalized malaise and body aches. Patient also reported an episode of fever and chills the night before. Upon examination upper respiratory tract infection was confirmed. Guaifenesin and acetaminophen were prescribed for upper respiratory tract infection symptoms. Based upon patient's reported LMP 45 days previously, this correlates with a gestational age of 6 weeks 3 days.
On the obstetric ultrasound performed at 23 weeks gestation, findings consistent with severe facial deformities were noticed (Fig.1). These included a single primitive ventricle (Fig.2), cleft palate (Fig.1), hypotelorism and absence of the interhemispheric fissure (Fig.4). Biparietal diameter of 7.12 cm was recorded, a measurement large for gestational age.  On a posterior view a lesion suggestive of a spinal pathology was also noted (Fig. 3). The imaging findings are consistent with a diagnosis of alobar holoprosencephaly, the most severe form of holoprosencephaly.
After detection of craniofacial malformations consistent with alobar holoprosencephaly, parents were oriented on prognosis. Outcome and prognosis issues like facial deformities, learning disabilities and survival risk due to endocrine and neurological complications after birth were addressed. Counseling regarding termination and genetic screening was given. Patient decided to continue pregnancy. Fetal chromosomal analysis was performed in which karyotype showed additional genetic material on chromosome 17. Parents will be evaluated for chromosomal translocations. At the time of this report, gestation was in progress and MRI imaging was not available due to insurance constraints.

Discussion
Holoprosencephaly (HPE) is a malformation of the brain, which is thought to be a consequence of an interruption in the normal growth and differentiation of the embryo. Although the precise mechanism of this defect is yet unknown it is thought to occur between the third and eighth week of development. The etiology is quite heterogeneous, since genetic and environmental factors have been identified. These range from chromosomal abnormalities, viral infections early in pregnancy, teratogenic substances and prenatal radiation to endocrine disorders (1). Up to 25%-50% of individuals with HPE will have a numerical or structural chromosomal abnormality. The most common risk factor/teratogen known to cause HPE in humans is maternal diabetes mellitus. Infants of diabetic mothers have a 1% risk, about a 200-fold increase, for HPE (2).
The prevalence of HPE is of about 1.3 in 10,000 births. The incidence of HPE has male:female ratio of 1.4/1 (3).
When the embryo fails to develop and to undergo the process of septation of the midline central nervous system HPE can occur. The normal process involves the migration of neural crest cells along the neural tube. These cells move and arrange in predetermined positions in order to complete the closure of the rostral and caudal neuropores. The primordial brain normally divides into two hemispheres. When a disturbance of this intricate process occurs fusion or failure of septation can occur in several of the central nervous system structures. This failure of septation includes ventricles and cerebral hemispheres.
Several types and gradation of HPE exist. Although the pathology is thought to be a continuum and clear distinction is not always possible, four general variants are usually recognized. Based on the degree of separation these variants are categorized as: lobar, semilobar, alobar. A Middle Interhemispheric Variant (MIHV) in which the posterior frontal and parietal lobes are not entirely separated has also been described (4).
Lobar HPE is considered a mild presentation of the condition, in which the right and left ventricles are separated and fusion is only seen on the prefrontal cortex. Semilobar as the name implies present with partial separation, but a single ventricle.
Total absence of midline forebrain division, presence of a primitive ventricle and fusion of cerebral hemispheres characterizes Alobar HPE, the most severe form. Neonates with alobar HPE frequently expire soon after birth (5).
The initial diagnosis in patients with no previous history of HPE or genetic abnormalities (low-risk patients) is done by prenatal ultrasound. Although ultrasound is the screening test of choice as well as the initial diagnostic test during the prenatal period, the MRI is considered to be the confirmatory test for holoprosencephaly in the postnatal period. CT-Scan has also been used for postnatal testing, but MRI remains the preferred method.
Prenatal ultrasound can detect anomalies of the central nervous system and a facial deformity of severe HPE as early as the first trimester, but is less sensitive for detection of milder forms of HPE.  Therefore, the use of prenatal MRI has been increasing for diagnosis of the milder forms of HPE after suspicion on ultrasound findings. Molecular analysis screening should be used for high-risk cases, with previous history of HPE. Moreover, the genetic heterogeneity and multihit origin of the cases linked to mutations make the task of genetic counseling a very difficult one. In addition, a study found that 13% apparently sporadic cases could have recurrence (6)(7).
The care of a child with HPE requires a multidisciplinary approach. Prognosis depends upon different complications the child can present at birth including: endocrine disorders, cardiorespiratory alterations, and/or seizures. Some reports suggest seizures occur in 52% of the cases. While, diabetes insipidus has been described to occur in about 72% of the cases. In that same study, by Plawner and colleagues, temperature instability occurred in 32% of the cases (8). Physical and occupational therapy is recommended, as for children with other brain defects. It is important to have in mind that some these children with milder cases of HPE may only have mild learning and/or behavior problems with few motor impairments. Therefore, some children with HPE will have a long life span, learn, and have meaningful lives.
Clinicians must be prepared to offer parental counseling about this condition. Counseling should mention that most HPE cases have an uncertain etiology and prognosis. Genetic screening should be encouraged in all cases, even when environmental risk factors have been identified. This multifactorial scenario makes the task of prenatal diagnosis and counseling on HPE a particularly challenging and difficult one for both the clinician and parents.

REFERENCES

1.    Barr M Jr, Hanson JW, Currey K, Sharp S, Toriello H, Schmickel RD, Wilson GN. Holoprosencephaly in infants of diabetic mothers. J Pediatr. 1983; 102: 565–8.    
2.    Croen LA, Shaw GM, Lammer EJ. Risk factors for cytogenetically normal holoprosencephaly in California: a population-based case-control study. Am J Med Genet. 2000;90:320–325.
3.    Blaas, HG, Eriksson, AG, Salvesen, KA, Isaksen, CV. Brains and faces in holoprosencephaly: pre- and postnatal description of 30 cases. Ultrasound Obstet Gynecol 2002; 19:24.
4.    Picone, O, Hirt, R, Suarez, B, et al. Prenatal diagnosis of a possible new middle interhemispheric variant of holoprosencephaly using sonographic and magnetic resonance imaging. Ultrasound Obstet Gynecol 2006; 28:229.
5.    Dubourg C, Bendavid C, Pasquier L, et al. Holoprosencephaly Orphanet J Rare Dis. Feb 2 2007;2:8.
6.    Odent S, Le Marec B, Munnich A, Le Merrer M, Bonaiti-Pellie C. Segregation analysis in nonsyndromic holoprosencephaly. Am J Med Genet. 1998;77:139–143.
7.    Alex M.-C. Wong, Larissa T. Bilaniuk, K.-K. Ng, Y.-L. Chang, A.-S. Chao, Y.-Y. Wai. Lobar holoprosencephaly: prenatal MR diagnosis with postnatal MR correlation. Prenatal Diagnosis. 2005; 25: 296-299
8.    Plawner, L.L., Delgado, M.R., Miller, V.S., Levey, E.B., Kinsman, S.L., Barkovich, A.J., Simon, E.M., Clegg, N.J., Sweet, V.T., Stashinko, E.E., Hahn, J. S. Neuroanatomy of holoprosencephaly as predictor of function: Beyond the face predicting the brain. Neurology 2002 59: 1058-1066

FIGURES


 
Figure 1: Obstetric Ultrasound at 23 weeks gestation depicting multiple facial deformities suggestive of holoprosencephaly.


 
Figure 2. Obstetric Ultrasound at 23 weeks gestation view of biparietal diameter measurements.
 
Figure 3. Prenatal ultrasound view, at 23 weeks, of fetus spine depicting
 possible spinal lesion.

 
Figure 4. Obstetric ultrasound view of the head of fetus at 23 weeks gestation.

ABBREVIATIONS
HPE = Holoprosencephaly
US = Ultrasound

QUESTIONS
Teaching Point:  Ultrasound Detection of Craniofacial Pathology can be related with the brain malformation known as Holoprosencephaly. HPE is a rare brain malformation in which the Alobar subtype is the most severe presentation.

1) Which of the following is the most severe form of HPE ?
a)    Lobar
b)    Semilobar
c)    Alobar
d)    Middle Interhemispheric Variant (MIHV)
e)    All are equally severe
Correct Answer: c

Explanation: Severity is related to the degree of fusion, and inversely proportional to the degree of separation.
A. Lobar HPE is considered a mild presentation of the condition, in which the right and left ventricles are separated and fusion is only seen on the prefrontal cortex.
B. Semilobar as the name implies present with partial separation, but a single ventricle.
C. Alobar, the most severe, in which there is a single ventricle and no separation of the cerebral hemispheres
D. Middle Interhemispheric Variant (MIHV) in which the posterior frontal and parietal lobes are not entirely separated
E. As seen from above explanations, every classification carries a different prognosis.

2) The most common risk factor associated with HPE in humans is:
a)    Maternal hypercholesterolemia
b)    Viral infection
c)    Bacterial infection
d)    Maternal diabetes mellitus
e)    None of the above
Correct Answer: d
Explanation:
 Of the above, maternal diabetes mellitus has been identified as the most common human teratogen linked to HPE. Maternal hypocholesterolemia not hypercholesterolemia, is thought to predispose to HPE. All other answer choices have been associated with HPE, but are not the most common cause.

3) Question: Which of the answer choices is false? Sonographic findings seen in HPE include:
a)    Snowstorm pattern (false)
b)    Hypotelorism (true)
c)    Primitive ventricle (true)
d)    Cleft palate (true)
e)    Cyclopia (true)
Explanation
Snowstorm pattern on US is not a characteristic finding of HPE, this finding is usually associated with hydatiform moles.
4) Which the following is the most common complication of newborns with HPE?
a)    Seizures
b)    Limb amputation
c)    Diabetes insipidus
d)    Temperature instability
e)    Diabetes mellitus
Correct Answer: C
Explanation: Diabetes insipidus has been described to occur in about 72% of the cases. While seizures are commonly described in HPE, reports indicated that they occur in 52% of the cases. Limb amputation is not commonly associated with HPE. Temperature instability has been report to occur in 32% of the cases. Diabetes mellitus is not a commonly associated complication with the HPE patient.

5) The preferred confirmatory test for Holoprosencephaly is
a)    CT- Scan
b)     MRI
c)     Ultrasound
d)     X-Ray
Correct Answer: B
Explanation:
Although ultrasound is the screening test of choice as well as the initial diagnostic test during the prenatal period, the MRI is considered to be the confirmatory test for holoprosencephaly in the postnatal period. This applies more for cases of semilobar and lobar variants in which the diagnosis cannot be determined with certainty by ultrasound imaging. MRI is not necessary in cases of evident alobar holoprosencephaly on ultrasound. CT-Scan would be an alternative to MRI for postnatal testing. The use of prenatal MRI has been increasing for diagnosis of the milder forms of HPE after suspicious ultrasound findings.