Cranial dermoids with risk of intra cranial extension

Dermoids result from failure of dysjunction of the cutaneous and neuroectoderm and contain epithelium, hair follicles, sebaceous glands, and other cutaneous elements. 
Nasal and midline sub-occipital (inion) dermoid cysts are more likely to be associated with a small overlying pit or tract and have a higher risk of intracranial and intradural extension (generally between the leaves of the falx cerebri or falx cerebelli, respectively).
Cysts with intracranial extension present clinically either due to recurring meningitis or, rarely, with intracranial mass effect. 
The treatment in all cases is surgical extirpation.