Long term outcome in surgically treated posterior fossa epidermoids

https://doi.org/10.1016/j.clineuro.2013.11.025Get rights and content

Abstract

Objectives

To study posterior fossa epidermoids treated surgically at our institute and to compare their long term outcome with respect to extent of surgical decompression.

Materials and methods

Retrospective analysis of 50 cases of posterior fossa epidermoid surgically treated at our institute between 1997 and 2007.

Results

The mean duration from onset of symptoms to surgery was 2.5 years. Patients with cerebellopontine angle (CPA) epidermoids presented predominantly with trigeminal neuralgia (35%) and hearing loss (29%) while patients with fourth ventricle epidermoids had features of raised intracranial pressure (ICP) and gait ataxia (69.2% each). The rate of recurrence was 9% in tumors considered totally removed and 93% in those subtotally removed. Of the 17 patients with recurrences, 3 (7.9%) underwent a second operation. The mean duration of follow up at first recurrence was 9.3 years.

Conclusion

Based on our experience, the rate of recurrence is significantly higher after subtotal removal as compared to total removal of epidermoids on long-term follow up. Symptomatic recurrence requiring re-exploration is evident only after a long duration (∼10.9 year) following primary surgery. Hence, total removal without producing new neurological deficits should be the standard goal when operating on posterior fossa epidermoid cysts.

Introduction

Epidermoid tumors account for around 1% of intracranial tumors and are known to occur at diverse locations in the neuraxis [1]. Posterior fossa epidermoids comprise a distinct entity since they insinuate across cisternal spaces, intimately involving multiple cranial nerves and vascular structures, thus making them a difficult tumor to completely resect. Attempts at total excision of the tumor capsule are often associated with significant morbidity in the postoperative period. On the other hand, partial removal risks recurrence and subsequent surgery [2]. The decision to radically remove these cysts must balance the risks of surgical complications vs the benefits gained.

We summarize our 11-year experience of surgically treated posterior fossa epidermoid tumors with the aim of reaching a consensus on the extent of tumor excision without compromising on postoperative clinical outcome and long term tumor recurrence.

Section snippets

Materials and methods

Retrospective analysis of 50 cases of posterior fossa epidermoid surgically treated at our institute between 1997 and 2007 was done. Data were collected regarding demographics, presenting signs and symptoms, management strategy, postoperative neurological complications and long term follow-up. Posterior fossa epidermoids were broadly classified based on their location into 2 groups: cerebellopontine angle (CPA) and fourth ventricle. CPA epidermoids were further sub-classified based on their

Patient demographics and clinical characteristics

Fifty patients presented with a diagnosis of posterior fossa epidermoids. All these patients were treated surgically and are evaluated in this review. There were 28 (56%) females and the age ranged between 19 and 66 years (mean 37.8 years). Clinical features at presentation depended on the tumor location as well as its extension. Patients with CPA epidermoids presented predominantly with trigeminal neuralgia, hearing loss and gait disturbance while those with lesions in the fourth ventricle had

Radiographic features

Computed tomography (CT) revealed all tumors to be hypodense with respect to brain tissue. A small area of peripheral calcification was demonstrated in 5 cases (10%), whereas subtle capsule-like enhancement was observed in 4 (8%). All patients were evaluated with magnetic resonance imaging (MRI) prior to surgery (Fig. 1, Fig. 2). Epidermoids are iso- to hypointense on T1-weighted (T1W) and hyperintense on T2-weighted (T2W) images in comparison to cerebrospinal fluid (CSF) and brain tissue.

Operative procedure

Standard operative approaches to CPA and fourth ventricle were used to achieve maximum tumor removal (Table 1). After durotomy, the tumor was visualized as a white, often cheesy mass filling the CPA or the 4th ventricle. After intracapsular tumor removal, extracapsular dissection was attempted to remove the capsule keeping in mind the adherent neurovascular structures. Often this necessitated incomplete removal of the capsule to preserve the integrity of the cranial nerves and blood vessels

Complications

There was significant improvement in trigeminal and lower cranial nerve dysfunction especially after surgery as shown in Table 3. This improvement was not noticeable in patients who had preoperative facial weakness. New onset facial nerve palsy after removal of posterior fossa epidermoid was observed in 2 patients. 2 patients had lower cranial dysfunction in the immediate postoperative period necessitating tracheostomy in one patient and gradual weaning from ventilator support in the other.

One

Long term outcome

Thirty eight patients presented to us for review on receiving our request letter. Only these patients were evaluated for long-term outcome assessment. mRS of these patients at the time of discharge and at subsequent follow up is given in Table 4. 22 belonged to Group A and 16 to Group B. Based on location of the tumor, 29 patients with primary CPA lesion and 9 patients with fourth ventricle tumor were available for analysis. The mean follow-up period was 9.4 years (range 4.8–15.3 years).

Discussion

Epidermoid cysts, also known as pearly tumors or cholesteatomas, were first described by Cruveilhier [4]. They are uncommon congenital lesions that represent 0.2–1% of all primary intracranial tumors [1] and belong to the spectrum of “tumors of disordered embryogenesis”. CPA epidermoids, being the most common location for posterior fossa epidermoids, constitute approximately 40–50% of all intracranial epidermoids and are the third most common tumors of the CPA after acoustic neuromas and

Conclusions

Based on our experience there is no compelling evidence to suggest that total removal of epidermoid results in increased morbidity and mortality. On long term follow up there was evidence to suggest that symptomatic recurrence requiring re-exploration occurs after long duration (∼10.9 year). The rate of recurrence is significantly higher after subtotal removal as compared to total removal of epidermoid. Hence, total removal should be the standard goal when operating on posterior fossa

Conflict of interest

None.

Contributions

Dr. Khursheed Ansari: Concept, drafting and revision of article. Dr. Chittur Viswanathan Gopalakrishnan: Drafting, image and manuscript revision. Dr. Suresh Nair: Drafting, image and manuscript revision. Dr. Girish Menon: Drafting, image and manuscript revision. No sponsorship/funding. No disclosures.

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