Posterior fossa infected dermoid with congenital heart disease: A novel hypothesis of an unusual association.

Intracranial dermoid cysts commonly present as a discharging sinus, local swelling, mass lesion, or abscess formation. These can sometimes be found in association with congenital anomalies. The author presents two original cases of infected posterior fossa dermoid associated with congenital heart diseases (CHDs) that is very rare. The embryologic basis for this unique occurrence is reviewed, and a new hypothesis proposed. Two infants with CHD presented with infected midline posterior fossa dermoid. Excision of the dermoid cyst with the sinus tract was performed. Postoperative period was uneventful. Both the infants had undergone surgery for congenial heart disease a few months prior to the present clinical presentation with uneventful recovery. Infected posterior fossa dermoid cyst without a discharging sinus should prompt a thorough examination to detect CHD. Early diagnosis and timely management results in better outcome.

Introduction

Dermoid cysts are congenital, nonneoplastic lesions comprising of epidermal and dermal derivatives.[123] These are thought to develop from the totipotent ectodermal cells that remain within the developing neural tube.[45] Dermoid cysts have a predilection to localize along the midline and are often associated with a dermal sinus tract.[4678] Patients with discharging dermal sinus may develop bacterial meningitis or abscedation of dermoid itself[910111213] and thus present early. Noninfected dermoids usually present late with either subtle signs or as part of the syndromic association.[14] Association of cranial dermoid tumors with congenital heart disease (CHD) is not reported in the English literature.

The author reports two original cases of infected posterior fossa dermoid and their rare association with CHD. The diagnosis, management, and the embryological basis of this clinical presentation are discussed in detail.

Case Reports

Case 1

A 1-year-old male infant, a known case of total anomalous pulmonary venous circulation (TAPVC) presented with features of meningitis for one week. He had undergone corrective surgery for TAPVC three weeks prior to his presentation. On examination, he was febrile with altered sensorium. Fundoscopy showed bilateral gross papilledema. A large posterior fossa ring enhancing mass lesion with obstructive hydrocephalus [Figure 1] was seen on emergency contrast enhanced computed tomography (CECT) scan of the brain.

Figure 1

Contrast-enhanced computed tomography brain of case 1 showing (a) large ring enhancing cerebellar mass lesion causing obstructive hydrocephalus. It also reveals a hyper dense subcutaneous dermal sinus tract (b) bone window showing suboccipital midline bony defect

An emergency suboccipital craniectomy and excision of the dermoid abscess and inflamed subcutaneous nodule was done [Figure 2]. Cyst contained abundant hair and thick pus. Culture from the pus revealed coagulase negative Staphylococcus aureus. The infant had an uneventful postoperative recovery. He was given culture-based antibiotics for 6 weeks. Histological examination of the cyst confirmed the diagnosis of the dermoid tumor.

Figure 2

Clinical photograph taken after the hair clipping of case 1 showing the skin dimple (arrow) over the subcutaneous nodule without evidence of discharging sinus

Case 2

A 1-year-old male infant presented with high-grade fever associated with vomiting. On examination, he was febrile, conscious, and responding to commands. There was an inflamed nondischarging dermal nodule over suboccipital area. He was a known case of CHD with a perimembranous ventricular septal defect (VSD). He underwent closure of the defect 8 months before the presentation. He was one of the twins, born to nonconsanguineous parents. Mother had gestational diabetes mellitus (GDM) and was delivered by elective lower segment caesarean section. CECT of the brain revealed a subcutaneous nodule in the suboccipital area [Figure 3]. Blood culture revealed S. aureus infection. A subsequent magnetic resonance imaging brain revealed a posterior fossa lesion, which was continuing with the subcutaneous nodule through a bony defect [Figure 4].

Figure 3

Computed tomography brain of case 2 showing (a) subcutaneous nodule, (b) cutaneous sinus tract and (c) bone window showing the small midline bony defect

Figure 4

Noncontrast T1-weighted images magnetic resonance imaging brain scan of case 2 showing (a) small hyperintense subdural lesion with sinus tract. (b) Sinus tract continuing with the subcutaneous nodule (red arrow). (c) Sinus tract traversing through the skin (black arrow)

Elective suboccipital craniectomy and excision of the dermoid, subcutaneous nodule, and dermal sinus tract was performed. His postoperative recovery was good.

Discussion

Intracranial dermoid cysts are unusual congenital, slowly progressive tumors accounting for approximately 0.1–0.7% of all intracranial tumors.[115161718] They occur predominantly in the posterior fossa, particularly in the midline.[319202122] In about 66%, the dermoid cysts are associated with some form of dermal sinus.[4] Some of these dermoid cysts can get infected with dermal colonizing bacteria and cause deeper suppurations.[131523] Hence, congenital dermoid cysts associated with discharging sinuses, present early in childhood due to infection or abscess formation.[13]

About one-third of dermoid cysts are not related to discharging sinus. These cysts may present late in life in association with other developmental defects.[41421242526272829] Intracranial dermoid cysts can sometimes be associated with chromosomal abnormalities like Klippel–Feil syndrome.[30] There are a few case reports on dermoid cysts in association with congenital abnormalities[30] like Dandy–Walkers cyst,[4] corpus callosal agenesis,[4] and diastematobulbia.[31] Exact incidence of congenital anomalies associated with dermoid cysts is not known.[414192428313233] To the authors knowledge, this is the first case report on dermoid cyst found in association with CHD. Possible embryological basis of this association is reviewed in this paper.

Embryogenesis and hypothesis of dermoid association with congenital heart disease

Dermoid cysts are thought to arise from a defect in the closure of the neural tube during the 3rd to 5th weeks of gestation.[514] Simultaneously, development of cardiovascular system occurs during the 3rd week of intrauterine life. Cardiac progenitor cells that lie in the epiblast, immediate lateral to the primitive streak migrate through the streak to form the endocardial cushion cells. Furthermore, the neural crest cells, migrating from the edges of the neural folds in the midbrain region, contribute to the endocardial cushion formation in the atrioventricular, and conotruncal regions.[343536] An abnormality in endocardial cushion formation leads to many cardiac malformations, including ASD and VSDs, and defects involving the great vessels. Since the cells populating the endocardial cushion cells include the neural crest cells, a defect in the neural crest cells can lead to abnormal migration, proliferation or differentiation of endocardial cushion cells. This can often produce both heart and craniofacial defects in the same individual [Figure 5]. Defective neural crest or endocardial cushion cells may be because of teratogenic or genetic causes.[3537]

Figure 5

Flow chart showing the proposed embryogenic hypothesis for the association of dermoid cyst with congenital heart diseases

Association of the dermoid cyst with TAPVC in our second case could be an incidental finding. However, there are no such studies showing the teratogenic and genetic causes accounting for common cardiac and craniofacial defects. GDM was shown to be associated with these abnormalities as it happened in one of our cases.[38] Defects in the chromosome 5 and 22 are associated with isolated congenital cardiac diseases.[3940] Nevertheless, there is no proven evidence stating that the same chromosomal defects are related to neural tube defects.

To understand this unusual association better, further genetic studied are required.

Conclusions

It is wiser to consider posterior fossa dermoid cysts in all children with midline occipital skin lesions. Apart from therapeutic implications, these two cases may throw some light on the embryogenesis and the possible correlation of congenital cardiac anomalies with intracranial dermoid cysts. The exact incidence and prevalence of this unusual association needs further evaluation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.