[Dermal sinus and dermoid cyst revealed by abscess formation in posterior fossa. Report of 2 pediatric cases and review of the litterature].

Cranial dermal sinus, usually associated with dermoid cyst, is the persistance of an abnormal embryonal communication between the skin and the central nervous system. It may be the source of intracranial infection, most often a meningitis and rarely an abscess formation. Two cases of little girls (18 months and 2 years) having dermal sinus with dermoid cyst revealed by cerebellar abscess formations are reported. In the first case there were multiple cerebellar abscesses with hydrocephalus leading to a raised intracranial pressure. In the second case there was an abscess formation adjacent to the dermoid cyst. CT scan showed cysts and abscesses but MRI, achieved in the second case, was useful in demonstrating the sinus tract as well as the associated cyst and abscess. The two patients underwent a posterior fossa surgery with antibiotic therapy. In the first case abscess drainage and ventricular external drainage were necessary before sinus and cyst excision. Two months after surgery the two patients were neurologically intact and developping well. Surgery with total excision of dermal sinus and dermoid cyst, even sometimes difficult, must be preferred to the simple abscess drainage and antibiotic therapy.