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 2016-09-30  Case of the week # 434  © Alberto Sosa Olavarría
Answer to the case of the week # 434
November 24, 2016 - December 8, 2016.

Alberto Sosa Olavarría
, Kristel Villanueva, Mardorys Díaz, Milagros Viloria, Jennifer Peña, Tomasa Cedeño, Mónica Pérez

Universidad de Carabobo, CEUSP, Maternidad Hospital Central Valencia, Venezuela.

Case report

A 24-year old patient (G1P0) with unremarkable history was referred to our unit for a second opinion at 21 weeks of gestation. Our ultrasound examination revealed the following findings.
The parents opted for termination of the pregnancy and the final diagnosis was sphenoid-occipital canal with oral hydromeningoencephalocele.

Images 1-8:
2D ultrasound images in different planes show a large cystic mass arising from the oral cavity. The corpus callosum was normal but we failed in identify the normal brainstem configuration.


Images 9 and 10: 3D ultrasound images show a large mass arising from the oral cavity. 


Video 1: 2D ultrasound images in different planes show a large cystic mass arising from the oral cavity. 

Images 11-16: Postmortem images revealed a large oral mass, with a cystic and solid component secondary due to persistent sphenoid-occipital canal. The content of the basal encephalocele plus meninges and cerebrospinal fluid was occipital lobe on the left side of the channel, part of the brainstem and pituitary gland (image 15). On the right side predominates meninges with bilobed cystic.  

OC; occipital lobe ; CC: corpus callosum ; T: thalamus.

The skull (cranium) develops from mesenchyme around the developing brain (21). The cranium consists of two parts: The neurocranium, a protective case for the brain and the viscerocranium, the skeleton of the face. Neurocranium covers the ventral, lateral and posterior parts of the brain as well as the ear and nose. The Neurocranium is divided in two portions: the membranous neurocranium and the cartilaginous neurocranium (chondrocranium).

The membranous neurocranium as the name implies is formed by intramembranous ossification. The mesenchymal cells is derived from neural crest and paraxial mesoderm. These cells then encircle the brain and form most of the flat bones of the skull. These flat bones are characterized by the present of bone spicules. The spicules progressively spread out from primary ossification centers toward the surface. The flat bones of the skull, like the frontal, parietal, the squamous part of the temporal, the occipital, the nasal and lacrimal bones are all membranous. At approximately the fourth week of gestation, the forebrain grows rostrocaudally and mesoderm proliferates ventrolaterally around the neuroectodermal adherence, causing the adherence to migrate dorsally and form an invagination, called the adenohypophyseal (Rathke) pouch.
During the fifth and sixth weeks of gestation, the adenohypophyseal pouch elongates, forming a narrow stalk between it and the stomodeum.

At approximately the sixth to seventh weeks of gestation, the cartilaginous sphenoid skull base develops, obliterating this adenohypophyseal stalk.

The sphenoid cartilage is composed of 2 paired presphenoid and 2 paired postsphenoid cartilages (21,22) The presphenoid cartilages fuse and later form the anterior sphenoid body, and the postsphenoid cartilages fuse to form the basisphenoid cartilage, which later becomes the posterior sphenoid body and sella turcica.

In mammals, it is possible to distinguish two components of this bone: the orbitosphenoid and the basi-post-sphenoid derive from the cephalic mesoderm whereas; the alisphenoid and the basi-pre-sphenoid are from neural crest cell origin.

The genetic control of the development of these two components is different further increasing the heterogeneity of these components (2). The sphenoid bone represents a complex structure in terms of anatomy and embryology. Indeed, is formed by the fusion of different primordia whose embryonic origins are different.

The occipital bone has both membranous and cartilaginous origin with ossification occurring as early as week 9 of fetal gestation. Its formations is dependent on complex interacts between genes and molecules with pathologies resulting from disruption of this delicate process. The formation of the occipital bone is intricate (8) and has been extensively studied with many controversial conclusions. The human occipital bone, like that of most other mammals, is ontogenetically and functionally unique when compared to others bones of the cranium. It is one of the first bones of the skull to develop and consist anatomically of four parts surrounding the foramen magnum: the basilar, squamous, and two condylar parts. The basilar part or basiocciput is formed from the fusion of four primary cranial vertebrae, which unite with the basisphenoid at the sphenooccipital synchondrosis to become the clivus (6).   

Defective fusion of the postsphenoid cartilages results in non-obliteration of the stalk between the adenohypophyseal pouch and the stomodeum and a residual canal extending from the sella turcica to the pharynx, named the persistent craniopharyngeal canal or CPC.

Craniopharyngeal canal represents a remnant of the stem of Rathke’s pouch that goes through the sphenoidal synchondrosis between the presphenoid and postsphenoid by a vertical conduct in the basisphenoid, extending from the floor of the sella turcica to the undersurface of this bone and connecting the pituitary fossa with the nasopharynx cavity. (4, 7, 9, 11, 21).

The persistent CPC has been classified into two groups based on size: large (several millimeters in diameter) and small (diameter less than 1.5 mm). The former type, also called transsphenoid canal, differs from the latter not only in its size but also in its propensity to be associated with craniofacial anomalies such as a transsphenoidal meningoencephalocele. (1, 4, 5,10,12 -16))

Basal cephaloceles are less common with an estimated incidence of 1 in 35,000 live births.
Basal encephaloceles are classified into transethmoidal, spheno-orbital, sphenomaxillary and transsphenoidal. The transsphenoidal variant accounts for 5% of basal encephaloceles (1 in 70,000 live births) (12).

Sternberg's canal is a lateral craniopharyngeal canal resulting from incomplete fusion of the greater wings of the sphenoid bone with the basisphenoid (5, 19).

In this rare case it was evident the absence of pre sphenoid, basi sphenoid and basi occipital with absence of basillary process of the occipital and anterior portion of the foramen magnum absent. The content of the basal encephalocele plus meninges and cerebrospinal fluid was occipital lobe on the left side of the channel part of the brainstem and pituitary gland. On the right side predominates meninges with bilobed cystic. The consequence of the lack of development of ossification nuclei of basilar portion of the occipital and posterior portion of the sphenoid was the existence of a channel whose measures were 3 x 2 x 5 centimeters.

Differential diagnosis with other oral fetal tumors such as epignatus, craneopharyngiomas, hamartomas, epulis , giant hemangioma language and others (3, 10, 14,17, 19). 


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19. Sosa Olavarría A.,Díaz Guerrero L., Pérez Canto G, Persistent craniopharyngeal canal © Sosa

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21. Skeletal System,



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