Surg Neurol 39 1990;34:39-42 Dermoid Cysts of the Posterior Cranial Fossa in Children Report of Nine Cases and Review of the Literature Pierpaolo Lunardi, M.D., Paolo Missori, M.D., Franco Maria Gagliardi, M.D., and Aldo Fortuna, M.D. Department of Neurological Sciences, Neurosurgery, University "La Sapienza," Rome, Italy Lunardi P, Missori P, Gagliardi FM, Fortuna A. Dermoid cysts of the posterior cranial fossa in children. Report of nine cases and review of the literature. Surg Neurol 1990;34:39-42. Dermoids of the posterior cranial fossa in children are rare. We report the clinical and pathological data on nine children with these lesions. A mean follow-up of 17.3 years after total removal confirms the excellent prognosis irre- spective of whether the presenting symptom is meningitis or intracranial hypertension. A brief review of 39 pub- lished cases follows. KEY WORDS: Dermal sinus; Dermoid cyst; Hydrocephalus; Posterior cranial fossa tumors Introduction According to Bostroem [5], the first report of a child with a dermoid cyst of the posterior cranial fossa was by Lannelongue and Achard in 1860 [15]. The first re- ported attempt at surgical treatment was made by Horrax in 1922 [12], but it was not until 1934 that a dermoid cyst of the posterior fossa was successfully removed, from a 6-year-old girl, by Tytus and Pennybacker [27]. The relevant literature consists of isolated case reports, and there is only one series that reports the late results [17]. This article reviews published work on posterior fossa dermoid cysts in children and presents the outcome of a follow-up study of nine children who underwent surgical treatment for this disease. Summary of Cases Patient population. Between 1951 and 1988, 362 chil- dren under the age of 16 with posterior cranial fossa tumors were operated on in the Department of Neuro- Address reprint requests to: Missori Paolo, M.D., Neurochirurgia, Viale dell'UniversitA 30a, 00185 Roma, Italia. Received October 11, 1989; accepted December 19, 1989. logical Sciences of the University of Rome "La Sa- pienza." Nine (2.4%) of them had a dermoid cyst. Every patient has been traced and examined in our outpatient clinic. Clinical history, surgical treatment, and follow-up out- come. There were four boys and five girls, and their age range was 10 months to 16 years (Table 1). Clinical onset was marked by typical intracranial hypertension in five cases and by an attack of meningitis in the other four. Three patients had a complete occipital dermal sinus, two an incomplete sinus, and the other two only an occipital bony defect. At operation the dermoid cyst was turning to abscess in three patients. In two patients the dermoid cysts were in the fourth ventricle, in four they were intradural, and in the other three the cysts were intra- and extradural. Surgical removal was complete in eight patients but in one a small fragment of the capsule adhering to the floor of the fourth ventricle was left in situ. The postoperative course was uneventful in all patients, none of whom developed hydrocephalus. At follow-up, after a period ranging from 2 to 37 years (mean 17.3 years), there had been no recurrences; all the patients were living and eight were in excellent health. One patient, who had presented an oligophrenic syndrome before the operation, did not improve after it. Discussion Intracranial dermoid cyst is a rare entity, accounting for between 0.1% and 0.7% of all intracranial tumors [11], and their most common site is the posterior cranial fossa at or near the midline [3,6,11,18,25]. In our series of developmental mass lesions of the posterior cranial fossa, dermoid cysts were found only in children, in contrast to 26 epidermoid cysts found only in adults. Matson [21], in a series of 418 posterior cranial fossa tumors in children, reported 10 cases of dermoid cyst (2.4%), 9 of which were connected with a persistent sinus tract. Collecting 25 cases of posterior fossa der- © 1990 by Elsevier Science Publishing Co., Inc. 0090-3019/90/$3.50