Nontraumatic convexity intradiploic arachnoid cyst

Area of Science:

• Neurosurgery
• Radiology
• Pathology

Background:

• Intradiploic arachnoid cysts are rare, benign lesions occurring within the diploë of the skull.
• They can present with varied radiological findings, often mimicking other bone pathologies.
• Understanding their presentation is crucial for accurate diagnosis and management.

Observation:

• A 63-year-old male presented with an unusual nontraumatic intradiploic arachnoid cyst.
• Radiography revealed an osteolytic lesion; CT showed inner table defect and widened diploë; MRI confirmed a cerebrospinal fluid-filled cyst.
• Histological examination of bone and arachnoid tissue showed no abnormalities.

Findings:

• The case highlights an intradiploic arachnoid cyst in the frontotemporal convexity, an uncommon location.
• Imaging findings included a circular osteolytic lesion, inner table defect, widened diploë, thinned outer table, and a cerebrospinal fluid-containing cyst.
• Bone scintigraphy showed no abnormal uptake, and histology was unremarkable.

Implications:

• This case underscores the diagnostic challenges posed by intradiploic arachnoid cysts, particularly atypical presentations.
• The typical presentation involves parasagittal, multiple, well-demarcated osteolytic lesions in the elderly.
• Diagnosis may necessitate exploratory surgery due to the unclear clinical features and potential for misdiagnosis based solely on imaging.