Child's Nerv Syst (1996) 12:318-322 9 Springer-Verlag 1996 Ismail H. Tekk6k Saleh S. Baeesa Michael J. Higgins Enrique C. G. Ventureyra Abscedation of posterior fossa dermoid cysts Received: 30 November 1995 I. H. Tekk6k 9 M. J. Higgins E. C. G. Ventureyra ([]) Division of Neurosurgery, Children's Hospital of Eastern Ontario, 401 Smyth Road, Ottawa, Ontario K1H 8L1, Canada Tel.: (613) 737-2316 Fax: (613) 738-4228 S. S. Baeesa 9 E. C. G. Ventureyra Division of Neurosurgery, University of Ottawa School of Medicine, Ottawa, Ontario, Canada Abstract Dermoid cysts of the pos- terior fossa are uncommon. When associated with a dermal sinus, these cysts are often diagnosed during early childhood. The main risk of such an association is contamination of the cyst leading to abscedation of the dermoid itself or formation of daughter abscesses within the cere- bellar hemisphere. We recently treated a 20-month-old girl who had a congenital dermal sinus leading to an intradural dermoid cyst. In addi- tion to the midline dermoid cyst, computerized tomography revealed an enhancing lesion extending into the adjacent left cerebellar hemi- sphere. Suboccipital craniectomy was undertaken after 2 days of exter- nal ventricular drainage, and the in- fected dermoid and adjacent cerebel- lar abscess were excised. Cultures of the operative specimen revealed Corynobacterium aquaticum, Enter- obacter sakazakii and Enterobacter cloacae, requiring 6 weeks of intra- venous antibiotic therapy consisting of ceftriaxone, penicillin and gen- tamicin. A diligent literature search revealed only 24 sporadic cases re- ported over a period of 56 years. All 24 cases were in children (mean age 17 months), and one-third were in infants under the age of 1 year. All but 1 of these patients underwent posterior fossa surgery, with mortal- ity and morbidity rates of 13% and 10%, respectively. Eleven (40%) children had suppuration within the cerebellar parenchyma, while the rest had abscedation of the dermoid cyst alone. Among the cases re- viewed S. aureus was the most com- mon agent, occurring with a prob- ability of 64%. Key issues for appro- priate management of these benign lesions are discussed. Key words Brain abscess 9 Cerebellar abscess 9 Dermoid cyst 9 Dermal sinus 9 Enterobacter cloacae. Staphylococcus aureus Introduction Dermoid cysts account for 0.1-0.7% of all intracranial space-occupying lesions [6, 10, 17, 23]. Dermoids usually become symptomatic during childhood or early adulthood [10]. These cysts originate from misplaced ectoderm dur- ing the 3rd-4th week of intrauterine life [6, 9]. In contrast to epidermoid cysts, which contain only keratinized epi- thelium and tend to occur paraxially, dermoid cysts con- tain dermal appendages, hair follicles and apocrine glands and tend to occur in the midline [6, 24]. Their most corn- mon locus is the posterior fossa, usually at the vermis, and occasionally within the IV ventricle [6, 9, 23]. Rarely, the maldevelopment generating the formation of the dermoid cyst may extend to the level of skin producing a coexist- ing dermal sinus. This tube, usually lined with epithelium, therefore contains the glandular architecture of skin, fa- vouring colonization by microorganisms. Through this communication, microorganisms may travel into the cyst with potential risk of central nervous system suppuration. Mount was the first to describe abscedation of an intracra- nial dermoid cyst in a 1-year-old female infant who had presented previously with signs and symptoms suggestive