Brought to you by
ECR 2013 / C-0060
Encephaloceles and menignoencephaloceles of the base of the skull: imaging, differential diagnosis and pictorial essay.
Congress: ECR 2013
Poster No.: C-0060
Type: Educational Exhibit
Keywords: Neuroradiology brain, MR, CT, Surgery, Hernia
Authors: S. Pollice1, R. Stanzione1, F. Quinto2, N. Maggialetti3, M. Maiorano4, T. Scarabino5; 1Andria/IT, 2Corato/IT, 3Molfetta/IT, 4Andria (BA)/IT, 5S.Giovanni Rotondo/IT
DOI:10.1594/ecr2013/C-0060

Imaging findings OR Procedure details

TRANS-SPHENOIDAL MENINGOENCEPHALOCELES

 

The trans-sphenoidal variant is the most common among encephaloceles of the base with an annual incidence of about 1 in every 700,000 live births.

Pollock has proposed the following etiological theories to explain its occurrence: lack of fusion of the ossification centers, increased intraventricular pressure with progressive erosion of the underlying bone or postnatal enlargement of small bony dehiscences, persistence of the cranio-pharyngeal canal.

 

THE CRANIO-PHARINGEAL CHANNEL OR STERNBERG'S CHANNEL


The persistence of this channel is a rare entity described for the first time from Landzert in 1868. It 'was reported in 5-10% of live births and approximately 0.42% of the asymptomatic population.

 

The channel has an oval or circular shape, through the body of the sphenoid from the midline of the floor of the sella turcica down until the nasopharynx at the junction between the vomer and rostrum of the sphenoid.


Currarino et al have divided this anomaly into two different subtypes in relation to their size: small channel or pitutitary channel with a maximum width of about 15 mm and larger channel, most frequently related to encephaloceles and other abnormalities of the midline.

 

The cause of the persistence of the channel is quite controversial: some authors support the hypothesis that the channel is the remnant of the ascending path followed by Rathke pouch  through the sphenoid from the nasopharynx to the sella turcica. This hypothesis is supported by histological studies have found that the presence of normal and abnormal pituitary tissue within the channel, from case reports describing the presence of sub-sellar or nasopharinx craniopharyngiomas associated with this anomaly or case reports describing the presence of intra-sphenoidal pituitary tissue.
Other authors simply assert that the cranio-pharyngeal canal is the remnant of a vascular channel containing a small artery and  veins embedded in a stromal connective tissue.

 

SPHENOID BONE EMBRIOLOGY

However, to correctly understand the embryological origin of the cranio-pharyngeal canal it is useful to recall the sphenoid bone embryology.

During embryological development the anterior sphenoid bone (presphenoid), the lesser wings, the posterior sphenoid bone (basisphenoid), the greater wings and the lateral pterygoid processes are built up first as independent cartilaginous precursors. Ossification starts at the third month of foetal life. While the presphenoid, lesser wings and basisphenoid, as well as the greater wings and pterygoid processes, fuse at the time of birth, only a weak cartilaginous union between the greater wings and the presphenoid/basisphenoid has been found in neonates. Bony fusion of the greater wings with the presphenoid/basisphenoid starts in its anterior portion. Posteriorly fusion can be incomplete, creating a lateral craniopharyngeal canal. This canal was mentioned by Sternberg in 1888 . While Sternberg consistently found this canal in children at the age of 3 to 4 years, he described an incidence of only 4% in adults.  A congenital bony defect resulting from incomplete fusion of the different sphenoid bone components can communicate with the sphenoid sinus after the necessary pneumatization has taken place. 

 

SYMPTOMS 

Symptoms are unilateral rhinorrhea, malfunction of the gland associated with its compression, unexplained hypophysectomy after adenoidectomy, recurrent meningitis after removal of nasopharyngeal mass.

 

IMAGING

Diagnostic imaging makes use of CT scan with window to show the bone defect and MRI expecially in differential diagnosis and to highlight the type of herniated tissue and its relationship to adjacent structures. CT cisternography, 3D reconstrcted CT scan an MRI provide excellent three-dimensional definition of the lesion useful for diagnosis and surgical planning.

 

SURGICAL TREATMENT

Surgical treatment consists of two approaches: transcranial and trans-palatal. The first method allows a good repositioning of the herniated tissue with closure of the defect with a periosteal flap with or without bone fragment.
The transpalatal approach is characterized by reduced invasiveness, often also the coexistence of a cleft palate makes this approach much more easier. Most frequent complications of this technique are infections.

 

 

TRANS-ETHMOIDAL MENINGOENCEPHALOCELES


The trans-ethmoid variant is due to a defect of the cribriform lamina, usually small and unilateral. This defect may have a congenital, traumatic, post-surgical or spontaneous origin.

The congenital forms are more frequently associated with encephaloceles and other craniofacial anomalies (lacrimal duct obstruction, agenesis of the corpus callosum).

The herniated tissue includes portions of the frontal lobes and olfactory apparatus and simulates the presence of polyps.

 

Almost one half of basal meningoencephaloceles are identified during the first year of life due to the presence of an intranasal mass lesion with manifestations such as nasal obstruction, nasal discharge, mouth breathing and snoring, and/or associated anomalies such as hypertelorism, cleft lip and palate, bifid nose, and coloboma. The presence of an intranasal mass with pulsation synchronous with the pulse and/or respiration in a newborn or young child indicates occult basal encephalocele, since nasal polyps are most uncommon in this age group.

 

SYMPTOMS

Common symptoms include: intermittent unilateral rhinorrhea, headache, nasal obstruction, olfactory disorders, recurrent meningitis and seizures.

 

IMAGING

Diagnostic imaging makes use of CT scan with window to show the bone defect and MRI expecially in differential diagnosis and to highlight the type of herniated tissue and its relationship to adjacent structures. CT cisternography, 3D reconstrcted CT scan an MRI provide excellent three-dimensional definition of the lesion useful for diagnosis and surgical planning.

 

SURGICAL TREATMENT

Surgical treatment involves endoscopic endonasal approach. The bone defect is repaired with a layer of fat intradural, epidural layer of bone and a flap of vascularized nasal mucosa. Required is the subsequent balloon compression. This repair with multilayer graft is presently preferred for to block the loss of cerebrospinal fluid but also to reinforce the base of the skull and prevent recurring encephaloceles. 

 

 

SPHENO-ETHMOIDAL MENINGOENCEPHALOCELES

The spheno-ethmoidal variant consists of a defect in ethmoid and sphenoid bone with encephalocele in the posterior nasal fossa.

 

SPHENO-ORBITAL MENINGOENCEPHALOCELES

The spheno-maxillary variant consists of herniation of meninges and tissue through the superior orbital fissure.

POSTER ACTIONS Add bookmark Contact presenter Send to a friend Download pdf
SHARE THIS POSTER
2 clicks for more privacy: On the first click the button will be activated and you can then share the poster with a second click.

This website uses cookies. Learn more