Skull Base Surgery of the Posterior Fossa

172

nerve when performing the tentorial cut by iden-
tifying the nerve before completing the cut.
When dissecting the middle fossa portion, care
must be taken not to injure the oculomotor nerve,
posterior cerebral artery, or posterior communi-
cating artery. The adherent portion of the cyst
wall should be kept in place, with no attempt to
pull or dissect it, because these lesions are
benign and slow growing. Any residual tumor
can be monitored with serial imaging
postoperatively.
In cases where the epidermoid cyst wall is liq-
uefied or ruptured, and the cyst contents are
spilled in the arachnoid space, the risk of aseptic
meningitis is high. The reported incidence of this
complication is as high as 18.2% [ 7 ]. Preoperative
steroid administration, intraoperative surgical
field irrigation with normal saline and hydrocor-
tisone solution [ 30 , 33 ], and long-term postoper-
ative steroid administration have been advocated
in these patients [ 7 , 8 , 17 ].

Surgical Outcome

The rate of gross total resection for posterior

fossa epidermoid cysts varies widely in the litera-

ture. It is evident in the contemporary series for

posterior fossa epidermoid cysts that complete

resection is achievable in no more than 75% of

the cases (Table 12.1). In one study, the reported

recurrence-free survival rates for gross total

resection and subtotal resection after 13 years of

follow-up were 95% and 65%, respectively [ 33 ].

In another study, the recurrence-free survival for

gross total resection and subtotal resection after

15 years of follow-up were 91% and 7%, respec-

tively [ 11 ]. Fourth ventricle epidermoid has a

higher rate for gross total removal when com-

pared with CPA epidermoid cysts.

A perioperative mortality rate related to neu-

rovascular structure injuries for posterior fossa

epidermoid cysts of 2–12% was reported in the

literature published before 2002; however,

advancement in microsurgical techniques and

Table 12.1 A summary for the major publications of the CPA and PF epidermoid cyst

Author Location

No. of

cases Total removal (%) Mortality Recurrence (%)

Follow-up

(years)

Sabin et al. (1987) C PA 20 5 5 10 6

Salazar et al. (1987) C PA 17 0 6 24 6.8

Yamakawa et al.

(1989)

C PA 15 47 6.6 20 8

Yasargil et al. (1989) C PA 22 97 0 0 5.7

De Souza et al. (1989) C PA 27 18 3 14.8 15 (max)

Lunardi et al. (1990) C PA 17 35 12 30 9

Samii et al. (1996) C PA 40 75 2.5 7.5 5.7

Doyle et al. (1996) C PA 13 54 0 31 8.6

Brunori et al. (1997) C PA 12 33 0 17 6.5

Mohanty et al. (1997) C PA 25 48 8 0 3.5

Talacchi et al. (1998) PF 28 57 3 30 8.6

Kobata et al. (2002) C PA 30 57 0 10 11.5

Scheifer et al. (2006) C PA 24 54.1 0 25 4.3

Safavi-abbasi et al.

(2008)

C PA 12 75 0 25 2.25

Gopalakrishnan et al.

(2014)

PF 50 62 0 44.7 9.4

Czernicki et al. (2015) C PA 17 29.4 0 29.4 9

Hasegawa et al. (2016) C PA 22 81.8 (total/

near-total)

0 – 9

Yawn et al. (2016) C PA 47 46 0 8 3.5

G. Alzhrani and W.T. Couldwell