-Acta

Acta Neurochir (Wien) (1990) 102:33-37

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Ncurochlrurglca 9 by Springer-Verlag 1990

Intradiploic Epidermoid Cysts of the Skull: Report of 10 Cases and Review of the Literature P. Ciappetta, M. Artico, M. Salvati, A. Raco, and F. M. Gagliardi Department of Neurological Sciences, Section of Neurosurgery, University of Rome "La Sapienza", Rome, Italy

Summary Intradiploic epidermoid cysts, fairly uncommon lesions in neurosurgical practice, are, as a rule, benign and slow-growing. Some attain great size, producing major neurological signs. Correct radiological assessment and complete removal of the tumour and its capsule are essential for adequate surgical treatment and good long-term prognosis. We report ten cases of intradiploic epidermoid cysts of the skull, three of which were giant lesions and one malignant, and analyze the clinicopathological and radiological features and treatment of these lesions in the light of the most important published data. Keywords: Computed tomography; epidermoid cyst; malignant epidermoid; skull neoplasm.

Introduction P r i m a r y i n t r a d i p l o i c e p i d e r m o i d t u m o u r s o f the skull are relatively u n c o m m o n . T h e first r e p o r t dates b a c k to Mfiller 32. By 1957 K l e i n s a s s e r a n d A l b r e c h t 24 h a d g a t h e r e d m o r e t h a n 100 cases a n d R o t h 4~ in 1964 cited m o r e t h a n 150. A c c o r d i n g to the literature accessible to us, the t o t a l n u m b e r o f cases r e p o r t e d to d a t e m a y be e s t i m a t e d at 223 l-s, 7, 9 is, 17, 18, 22 24, 26-29, 31, 35, 36, 38-43, 46, 47 W e p r e s e n t o u r experience in the surgical t r e a t m e n t o f 10 cases, 3 o f which have a l r e a d y been r e p o r t e d 19' 20, o f i n t r a d i p l o i c e p i d e r m o i d cysts t h a t c a m e to o u r a t t e n t i o n b e t w e e n 1952 a n d 1987 a n d c o n s i d e r their clinical features, p r o g n o s i s a n d t r e a t m e n t with reference to the p u b l i s h e d d a t a a v a i l a b l e to us.

Clinical Material and Methods Table i summarizes the clinical data of the 10 patients of our series. Plain X-rays of the skull, performed in all cases, imaged the epidermoid cyst as an osteolytic lesion with well-defined, sometimes sclerotic, margins (Figs. 1A, 1B, 5A) developing within the diploe.

In 6 cases (n. 1, 2, 5, 7, 9, 10) the mass tended to develop intracranially and in 3 of these caused intracranial hypertension. Two of the latter thk-ee lesions (n. 2 and 7) were giant epidermoid cysts developing mainly within the skull, their growth being associated with a progressive increase in intracranial pressure and focal neurological signs. CT scanning, done in 6 cases, demonstrated the existence of a full-thickness lesion of the diploe (Figs. 2, 3, 4, 5B), demarcating it precisely. In the case of the malignant lesion (n. 7) the CT scan supplied a good image of the extent of the tumour (Fig. 3). Removal was apparently total in all cases. The follow-up ranges from 1 to 25 years with a mean of 8.8 years. There were no recurrences, except in the case of the malignant lesion, in which despite a course of radiotherapy (45 Gy to the lesion) a recurrence developed 10 years later; this required removal, which was apparently total. The patient's genera1 health and neurological status one year after the second operation are satisfactory. The other patients are leading a normal life with the exception of one dead 11 years after the operation, from other causes.

Discussion I n t r a d i p l o i c e p i d e r m o i d cysts are less frequent t h a n the i n t r a d u r a l variety, are s l o w - g r o w i n g a n d have a predilection for certain areas o f the skull, n a m e l y the frontal, p a r i e t a l a n d occipital bones 21' 24, 42, 46. Skand a l a k i s etal. 41 gave the following frequencies o f inv o l v e m e n t : b o t h tables 4 6 % , o u t e r table only 31%, b o t h tables a n d d u r a m a t e r 10%, inner table 7 % , i n n e r table a n d d u r a m a t e r 3 %, inner table, d u r a m a t e r a n d brain 3%. These t u m o u r s m a y occur at a n y age f r o m the first to the seventh decades o f life with a m e a n age o f 32 to 38 years 3~ 41. T h e r e is no clear sex preference. F i r s t to p u t f o r w a r d a t h e o r y o f the origin o f epid e r m o i d s was V o n R e m a k 45 w h o in 1854 p o s t u l a t e d their genesis f r o m f r a g m e n t s o f epithelial tissue t h a t h a d m i g r a t e d d u r i n g e m b r y o n i c d e v e l o p m e n t . Since

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P. Ciappetta etal. : Intradiploic Epidermoid Cysts of the Skull

Table 1. Clinical Findings in 10 Patients with Intradiploie Epidevmoid Cyst Case

Age/sex

Location

Lenght of history

Clinical features

X-ray film

CT

Removal

Follow-up

I

16m*/M

Bregmatic

6m

Local swelling

Osteolysis

--

Total

Good-25 y

2

40 y~

Rt Occipital

7y

Headache, vomiting, dizziness; giant les.

Osteolysis

--

Total

Good-I0 y

3

10 m/M

Bregmatic

7m

Local swelling

Osteolysis

--

Total

Good-20 y

4

24 y/F

Rt. Pariet.

10 y

Frontal pain

Osteolysis

yes

Total

Good- 1 y

5

57 y/M

Lt Orbit

10 y

Lt Exophthalmos optic atrophy giant les.

Osteolysis

--

Total

Good-3 y

6

14 y/F

Lt Temporal

2y

Local swelling

Osteolysis

yes

Total

Good-15 y

7

45 y/M

Rt Temp.-Par.Occipital

1y

Headache, vomiting; giant les.

Bony eros.

yes

App. total

Recurrence after 10y

8

21 y/F

Lt Frontal

1y

Local swelling, frontal pain

Osteolysis

yes

Total

Good-2 y

9

18 y/M

Rt Frontal

12 y

Local swelling, headache Osteolysis

yes

Total

Good-1 y

10

23 y/F

Lt Occipital

1y

Local swelling, headache

yes

Total

Good-1 y

Osteolysis

m* = months; y~ = years.

then there have been n u m e r o u s theories r e g a r d i n g the p a t h o g e n e s i s o f these t u m o u r s . T h e c u r r e n t view is t h a t epithelial r e m n a n t s e r r o n e o u s l y d e t a c h f r o m the n e u r a l g r o o v e b e t w e e n the t h i r d a n d fifth e m b r y o n i c weeks. T h e i r d e p o s i t i o n in e c t o d e r m a l structures ( b r a i n a n d

Fig. 1. Case n. 10. Plain X-ray films in A-P view (A) and lateral view (B) showing the osteolysis of the occipital bone

skin) d e t e r m i n e s the g r o w t h o f e p i d u r a l , i n t r a d i p l o i c a n d e p i c r a n i a l t u m o u r s in the midline. T h e inclusion o f cell nidi in the s e c o n d a r y vesicles d u r i n g the fifth week o f e m b r y o n i c life explains a lateral localization. I n t r a d i p l o i c e p i d e r m o i d cysts are usually small o r fairly small b u t large lesions do occur, a s s o c i a t e d with signs o f i n t r a c r a n i a l h y p e r t e n s i o n a n d focal n e u r o l o g ical signs. These lesions are, as a rule, benign but, rarely,

P. Ciappetta el al. : Intradiploic Epidermoid Cysts of the Skull

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Fig. 2. Case n. 10. CT scan of the same patient demonstrating the bony defect and the sclerotic edge typical of the epidermoid cyst

Fig. 3. Case n. 7. CT appearance of a malignant epidermoid tumour originating from the skull which shows a huge intradural extension

Fig. 5. Case n. 4. Plain X-ray film in lateral view (A) and CT scan (B) show multiple defects of the parietal bone

they may present malignant transformation, especially in the event of partial removal or of recurrence 25' 41, 43, 46, 47

Fig. 4. Case n. 8. The CT scan shows a lytic lesion with well-defined borders involving both the tables and being in contiguity with the dura mater

There may be little or no clinical evidence apart from a painless swelling below the scalp, occasionally associated with a palpable bone defect 6' 21, 42 The slow course and mainly extradural growth of these tumours allows them to attain considerable size without producing neurological symptoms 34. Headache and focal epileptic seizures are among the most frequent symptoms. An intracranial hypertension syndrome develops in the case of large tumours, classified as giant epidermoids, and is usually accompanied by focal neurological signs 7' 27, 30, 33, 35, 37 Intradiploic epidermoid cysts have a characteristic

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radiological pattern, first described by Cushing in 192212 , namely an area o f bone destruction, o f lower density than the surrounding bone, with s m o o t h sclerotic margins. In the purely intradiploic cases a central radiolucent image appears between the two tables, which appear separated. C T scanning affords an excellent definition o f site, size and limits o f these lesionsl0, 15, helping to identify exactly the zones o f thinning or o f a gap between the tables and at the same time showing up any calcifications and the status o f the underlying cerebral parenchyma. A n g i o g r a p h y is o f limited value as it provides only generic evidence o f an extracerebral nonvascular lesion 1i. A c c o r d i n g to Cushing 12 the aim o f surgery is complete removal o f the t u m o u r together with its capsule, which must be carefully dissected f r o m the bone and dura mater. He further stated that it is preferable to p e r f o r m the c r a n i o t o m y at the periphery o f the t u m o u r , passing t h r o u g h n o r m a l bone and avoiding d a m a g e to the capsule 7. T h o r o u g h curettage o f the dura m a t e r is often necessary to free it f r o m material o f the epiderm o i d cyst wall 7' 19, 34. Sometimes complete removal involves excision o f dura mater adhering tightly to the t u m o u r capsule, followed by dural repair 19. Complete removal is essential to prevent further progression o f the erosive lesion, the risk o f infection and o f aseptic meningitis 46. Incomplete removal o f the t u m o u r wall is followed by recurrence 12' 21, 37, 41, 46 while total removal is associated with a g o o d prognosis with p e r m a n e n t cure and minimal operative mortality v' 10, 16, 2o, 3o W h e n removal requires extensive excision o f bone, skull repair with acrylic cement 7' 10,44 m a y be necessary to close the b o n y gap. This m a y be done at the same time as removal 7 but in our experience it is best done a few m o n t h s later s, as performed in two giant lesions o f our series. I n the rare cases o f malignant epidermoid cyst (13 cases described to date) the prognosis is very poor. I n their review o f the literature Y a n a i etal. 47 distinguish two classes o f these t u m o u r s : those n o t previously operated on and those in which malignant t r a n s f o r m a t i o n takes place after subsequent operations because o f recurrence o f a partially removed lesion. In the former case the localization o f the mass is intradural and in the latter extradural. Only two patients operated on for malignant epidermoid cyst have survived47; to these m u s t n o w be added one o f our patients (case n. 7). A c c o r d i n g to Yanai et al.47 selection o f the proper quality o f X-rays has p r o d u c e d g o o d results, as in our

P. Ciappetta et al. : Intradiploic Epidermoid Cysts of the Skull

case. They consider that regional .intra-arterial perfusion with cytotoxic and chemotherapeutic agents (alone or combined with surgery and radiotherapy) used in the treatment o f s q u a m o u s cell carcinoma might be o f value also in malignant epidermoids.

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Correspondence and Reprints: Pasquale Ciappetta, M.D., Universit~ di Roma "La Sapienza", Dipartimento di Scienze Neurologiche, Sezione di Neurochirurgia, Viale dell'Universit~ 30/A, 100185 Roma, Italy.