In a child with a dermoid cyst causing a full‑thickness posterior skull table defect, what are the options for bony reconstruction and does the size of the defect influence the management choice?

Management of Bony Defects in Pediatric Skull Dermoid Cysts

Children with dermoid cysts causing posterior skull table defects require mandatory consultation with pediatric neurosurgery or plastic surgery for cranioplasty planning, and yes, the size and depth of the bony defect critically determines the reconstruction approach. 1

Preoperative Imaging Requirements

Before any surgical intervention, obtain both:

• CT scan to delineate the exact bony defect dimensions, full-thickness skull erosion, and intradiploic involvement – this provides essential bone detail for surgical planning 1
• MRI to identify soft-tissue tract components, epidural extension, and any intracranial dermoid components – critical for detecting deep extension that CT cannot visualize 1

Specialist Consultation Algorithm

Mandatory neurosurgical or pediatric plastic surgery consultation is required when:

• Any full-thickness skull defect is identified and reconstruction is needed 1
• Any epidural or intracranial extension is present 1
• The dermoid is midline and may communicate with the intracranial compartment 1

The American Academy of Pediatrics specifically recommends that infants, children, and adolescents with congenital malformations of skull structures, including dermoid lesions, should be referred to a pediatric plastic surgeon 2

Bony Reconstruction Options Based on Defect Size

Small Defects (No Significant Cranial Impingement)

• Primary closure without cranioplasty is typically sufficient when there is no significant bone erosion 3
• Approximately 46.5% of pediatric skull dermoid cases fall into this category 3

Moderate Defects (Partial or Full-Thickness Erosion)

• Split-thickness calvarial bone graft is the preferred reconstruction method for defects requiring cranioplasty 4
• This technique was used in 14 of 20 patients (15%) who had outer table erosion with inner table involvement 4
• Lesions requiring cranioplasty are significantly larger (mean 1.9 ± 2.81 cm) compared to those not requiring reconstruction (1.23 ± 0.98 cm) 4

Large Defects with Epidural Extension

• Neurosurgical involvement is obligatory – these cases carry risk of intracranial complications including meningitis, brain abscess, and subdural empyema 1
• Approximately 5% of pediatric skull dermoids demonstrate epidural extension 5
• En bloc resection of the dermoid cyst with the associated dermal sinus tract should be attempted in a single stage when dermal sinus tracts are present 6

Critical Size-Related Findings

The literature demonstrates a clear relationship between defect characteristics and management:

• 18.9% of cases show partial-thickness cranial erosion 5
• 29.6% demonstrate full-thickness cranial erosion 5
• 5.0% have full-thickness erosion with epidural extension 5
• Delay in surgical timing significantly correlates with increased cranial involvement (p < 0.00001) 5

Timing Considerations

Early surgical resection is strongly recommended because:

• Dermoid cysts have continuous growth capacity 5
• Delayed surgery significantly increases the risk of deeper cranial involvement 5
• The mean age at surgery in large series is 1.5 ± 2.1 years, with 48.7% operated between 1-3 years and 32.9% under 1 year 3
• Gross total resection was achieved in all cases in contemporary series with minimal complications 4, 3

Common Pitfalls to Avoid

• Never assume a dermoid cyst is superficial based on external appearance alone – imaging is mandatory to assess depth 1
• Do not delay surgery waiting for the child to grow – this increases the risk of full-thickness erosion and intracranial extension 5
• Frontal and pterional locations show significant association with bone erosion – these warrant particularly careful preoperative assessment 3
• Intradiploic cysts (present in 9.3% of cases) require special attention as they may be missed on superficial examination 3

Surgical Approach Selection

• Endoscopic approaches are favored for supraorbital and glabellar lesions (75% endoscopic vs 25% open) to improve cosmesis and limit tissue damage 4
• Open craniotomy is standard for posterior fossa and larger defects requiring cranioplasty 6, 4
• Complete excision with cranioplasty when needed achieves cure in virtually all cases with low morbidity and no surgery-related mortality in modern series 6, 4, 3