Teaching Case

An 8year male child presented with a soft cystic swelling in the scalp in the area of the anterior fontanelle. It was tense on crying and was nontransilluminant. The parents complained of a gradual increase in size since birth.

CT scan of the head was done which showed a cystic swelling in the region of the anterior fontanelle under the subgalleal tissue. There was indentation with an impression on the frontal and parietal bones at the region of anterior fontanelle. The fonatnelle itself was closed without any no obvious erosion or beveling at the margins.

MR was done to evaluate the deeper extent of the lesion and it showed that the lesion is located deeper to the subgalleal tissue of the scalp and superficial to the skull. No communication with the intracranial tissue was seen. No infiltration of the superior sagittal sinus was seen. The cyst had T2 hyperintense fluid which showed suppression on FLAIR images. Some globular areas of hyperintensity were seen within the cyst fluid on T2 fat-suppressed images which were iso to hyperintense on T1 likely suggesting solid/fatty contents. Superior sagittal sinus was patent. 

Background

Anterior fontanelle inclusion cysts or Adeloye-Odeku Disease are cystic lesions overlying the anterior fontanelle without communication with the underlying intracranial compartment. Anterior fontanelle inclusion cysts are formed due to sequestration of epidermal rests at the third to fifth week of gestation [1]. Cyst lining is mainly stratified squamous epithelium contain fluid[1]. Sometimes, they contain skin appendages (hair, sebaceous glands) in which case they can be classified as dermoids. When epidermal cells a found, these cysts should be considered epidermoid cysts.

Clinical Perspective

Anterior fontanelle inclusion cysts account for only 0.1–0.2% of all skull lesions[2,3,4]. These inclusion cysts generally present in 1st year of life and show progressive enlargement in size. Most cases present at 3–6 months as a gradually increasing scalp swelling.[2,3,5,6,7,8]

Although the term congenital dermoid inclusion cyst is more common some of these lesions do not contain any secondary skin appendages and represent epidermoid cysts[1]

Imaging Perspective

These cysts are rather rare and they should be investigated thoroughly by MRI. In case of unavailability of MRI, CT should be used as an alternative imaging modality. Imaging is mainly done to look for infiltration into the superior sagittal sinus or any invasion into the brain parenchyma. Invasion of the superior sagittal sinus changes the surgical approach and may require perioperative blood transfusion[9].

Outcome

Surgical excision is the usual line of treatment and complete resection is curative.  A generous coronal incision is usually given and dissection is done from the periphery to midline. Dissection of the attachment on the superior sagittal sinus is done last. Any tear in the superior sagittal sinus or the dura is repaired by a muscle patch. [9]

Teaching Points

Inclusion cysts are rare in occurrence in the area of the anterior fontanelle. The most important consideration while dealing with these cysts is whether they show intracranial extension or infiltration into intracranial structures. Pre-operative imaging is of utmost importance to avoid surgical complications. This case report is about a year male child with scalp swelling.

Differential diagnosis list:

1. Vascular malformations show internal vascularities, arterial feeders and draining veins.
2. Venous malformation which is another differential of cytic lesions may show phleboliths inside.
3. Sinus pericranii – they show communication with the intracranial venous system which is the chief differentiating factor from inclusion cysts
4. Cystic Langerhans cell histiocytosis: They usually cause beveling of the margins of the skull. Other skull lesions, pituitary and vertebral involvement also play a role in the diagnosis.
5. Meningocele/ cephalocele: frank communication with the intracranial component can be visible on MRI