Pure endoscopic removal of epidermoid tumors of the cerebellopontine angle

Applying the Full Endoscopic Keyhole Technique to CPA Lesions: A Single-Center Study

In recent years, endoscopy has become an increasingly common tool used during neurosurgical procedures. However, its application in treating cerebellopontine angle (CPA) lesions has not progressed as rapidly. In this study, the authors present their initial experience with surgically treating CPA lesions using a fully endoscopic keyhole retrosigmoid approach. They conducted a retrospective analysis of clinical data from patients who underwent endoscopic keyhole CPA surgery at their center between May 2017 and April 2022. They provide a comprehensive explanation of this method and an overview of the strategies that have been developed to achieve better clinical outcomes. The study included 107 patients, consisting of 10 cases of vestibular schwannoma, 21 cases of epidermoid cyst, 32 cases of trigeminal neuralgia, and 44 cases of hemifacial spasm. The authors analyzed the clinicodemographic details of the patients. Among the 31 tumor cases, gross total resection was achieved in 25 patients (80.6%), while near-total resection was performed in 6 patients (19.4%). In patients with trigeminal neuralgia, facial pain resolved in 31 out of 32 patients (96.9%). Similarly, facial convulsions disappeared or were relieved in all 44 patients (100%) with hemifacial spasms after the operation. Postoperative complications included facial nerve paresis (n=9, 8.4%), with improvement observed in 6 cases during follow-up, transient facial hypoesthesia (n=3, 2.8%), cerebrospinal fluid rhinorrhea (n=3, 2.8%), transient abducens paresis (n=1, 0.9%), and postoperative hemorrhage (n=1, 0.9%). Endoscopy provides improved deep illumination and, combined with close-up observation, enhances the visualization of structures within the CPA region. The fully endoscopic keyhole technique is a safe and effective method for managing CPA lesions.

Endoscopic endonasal resection of an epidermoid cyst in the cavernous sinus: A case report and literature review

Background

Epidermoid cysts of cavernous sinus (CS) are rare congenital neoplasms of the central nervous system. In previous literature reports, the treatment for CS epidermoid cysts was mainly microsurgical resection, and the surgical methods included simple microsurgery and endoscope-assisted microsurgery. The present case report demonstrates the first case of complete resection of a CS epidermoid cyst by a simple endoscopic endonasal transcavernous (EET) approach.

Case presentation

A 54-year-old woman presented with chronic persistent headaches and occasional syncope. Brain MRI demonstrated a space-occupying lesion of the left CS, and digital substruction angiography (DSA) showed a small aneurysm at the beginning of the left ophthalmic artery. Thrombotic therapy of carotid-ophthalmic aneurysms was performed first, and the patient underwent resection of the CS lesion secondary. Considering the location of the lesion and the neuroendoscopy technology and experience of the doctor, we made bold innovations and used an EET approach to achieve complete resection of the lesion. The postoperative pathological results were consistent with the characteristics of epidermoid cyst. During the 1-year follow up, the patient showed no apparent signs of recurrence on head MRI.

Conclusion

Epidermoid cyst of cavernous sinus is a rare benign occupying lesion in cavernous sinus. Reviewing the previous literature, the main treatment is microneurosurgery, and neuroendoscopy is only used as an auxiliary equipment. We present the first case of complete endoscopic resection of CS epidermoid cyst by EET approach according to CARE guidelines, aiming to share the new surgical plan for CS epidermoid cyst and provide more surgical options for this disease for neurosurgery colleagues.

Combined endoscopic and exoscopic resection of intracranial epidermoid cysts

OBJECTIVE

This article aims at introducing an endoscopic-exoscopic technique for the resection of epidermoid cysts.

METHODS

We retrospectively analyzed the intracranial epidermoid cysts patients who received whole course combined endoscopic and exoscopic resection between 2017 and 2020 at our institution, to explore the benefit of combined endoscopic and exoscopic resection of intracranial epidermoid cysts and evaluated the clinical utility of endoscopic-exoscopic technique.

RESULTS

A total of 17 patients were enrolled in the study. Of all patients, 6 patients (6/17, 35.3%) underwent total resection, 10 patients (10/17, 58.8%) underwent subtotal resection (residual capsule and/or) and 1 patient (1/17, 5.9%) underwent partial resection. Postoperative surgical complications were seen in 3 patients (3/17, 17.6%), including intracranial infection in 2 patients （2/17, 11.8%） , and a delayed postoperative hematoma observed in the seventh day after operation for 1 patient (1/17, 5.9%), who was treated in a conservative manner and recovered smoothly from the hemorrhage. The median follow-up time was 33.3 months (range 14.5-54.5 months). During the follow-up period, there was no recurrence of the tumors that received total resection. 2 patients developed residual tumor regrowth but did not show any symptom therefore no further surgery was required.

CONCLUSIONS

Endoscopic-exoscopic technique is safe and efficient in the resection of intracranial epidermoid cysts with panoramic views and superior maneuverability. With further development and accumulation of practical experiences, the endoscopic-exoscopic technique can also be applied in the resection of other intracranial tumors.

Assessment of epidermoid cyst with trigeminal neuralgia before neuroendoscopy: A high-resolution MR study based on 3D-FIESTA and MR angiography

PURPOSE

To assess the value of preoperative 3D-FIESTA and MR angiography (MRA) in endoscopic resection of epidermoid cysts presenting with trigeminal neuralgia (TN).

METHODS

3D-FIESTA and MRA were performed before neuroendoscopy in 32 cases of epidermoid cysts with TN, and the tumors were grouped into types A, B, C, and D according to the relationship between the tumor and adjacent nerves and arteries (Hitoshi Kobata's classification). Evaluation of the neuroendoscopic resectability of different types of tumors, included gross total tumor removal (GTR), subtotal tumor removal (STR), and partial tumor removal (PTR). During the 5-year follow-up, symptoms were assessed based on facial pain relief using the Barrow Neurological Institute (BNI) score.

RESULTS

The coincidence rate between MRI classification of the tumor and the operation was 100%. Type B tumors were the most common (18/32, 56.3%). Type A tumors showed the highest resectability (9/9, 100%), followed by type B tumors (14/18, 77.8%). Moreover, microvascular decompression was performed in all 4 cases of type C and 1 case of type D tumors. During follow-up, 23 patients showed marked improvement in symptoms (15, 8 of BNI I or II), 8 cases showed partial improvement (BNI III), and only 1 case of type C tumor was associated with poor facial pain relief, which recurred 5 years later (BNI IV).

CONCLUSIONS

Preoperative high-resolution MR can accurately analyze the relationship between epidermoid cysts and adjacent nerves and arteries. It could act as a powerful tool in the evaluation of tumor resectability and the prognosis of surgery.

Cerebellopontine Angle Epidermoids: Comparative Results of Microscopic and Endoscopic Excision Using the Retromastoid Approach”

Background Densely packed neurovascular structures, often times inseparable capsular adhesions and sometimes a multicompartmental tumor extension, make surgical excision of cerebellopontine angle epidermoids (CPEs) a challenging task. A simultaneous or an exclusive endoscopic visualization has added a new dimension to the classical microscopic approaches to these tumors recently.

Methods Eighty-six patients (age: 31.6 ± 11.7 years, M:F = 1:1) were included. Nineteen patients (22.1%) had a multicompartmental tumor. Tumor extension was classified into five subtypes. Sixty-two patients underwent a pure microscopic approach (72%) out of which 10 patients (16%) underwent an endoscope-assisted surgery (11.6%) and 24 patients (28%) underwent an endoscope-controlled excision. Surgical outcomes were retrospectively analyzed.

Results Headache (53.4%), hearing loss (46.5%), and trigeminal neuralgia (41.8%) were the leading symptoms. Interestingly, 21% of the patients had at least one preexisting cranial nerve deficit. Endoscopic assistance helped in removing an unseen tumor lobule in 3 of 10 patients (30%). Pure endoscopic approach significantly reduced the hospital stay from 9.2 to 7.3 days (p = 0.012), and had a statistically insignificant yet a clearly noticeable lesser incidence of subtotal tumor excision (0 vs. 10%, p = 0.18) with comparable cranial nerve deficits but with a higher postoperative cerebrospinal fluid (CSF) leak rate (29% vs. 4.8%, p = 0.004).

Conclusion Endoscope assistance in CPE surgery is a useful addition to conventional microscopic retromastoid approach. Pure endoscopic excision in CPE is feasible, associated with a lesser duration of hospital stay, better extent of excision in selected cases, and it has a comparable cranial nerve morbidity profile albeit with a higher rate of CSF leak.

Posterior fossa epidermoid tumors: a single-center study and proposed classification system

BACKGROUND

Epidermoid tumors of the cerebellopontine angle and posterior fossa account for approximately 1% of all intracranial tumors. Classifications that may guide surgical planning in the current neurosurgical practice are lacking. This study aimed to focus on the surgical outcome and suggest a classification system that may aid neurosurgeons in determining the goal of resection to minimize morbidity and mortality rates.

METHODS

The study population comprised patients who underwent surgery and follow-up for tissue-proven epidermoid tumors between 2015 and 2020. Patients' data, including demographic features, clinical symptomatology, the extent of surgical resection, and postoperative outcomes, were retrospectively evaluated. A new classification system was designed based on the anatomical-radiological findings and was evaluated in terms of clinical symptomatology, radiological features, surgical approach, and postoperative outcomes.

RESULTS

The patient population comprised 22 women (57.9%) and 16 men (42.1%), with a mean age of 34.9 years. A practical classification system based on the radiological-anatomical vertical (1, 2, and 3) and horizontal (a, b, and c) tumor extensions was designed. No significant differences were found in the patients in terms of sex/age. The most commonly observed symptom was gait disturbance (34.2%). The preoperative tumor diameter was significantly larger in the subtotal resection (STR) group than in the gross total resection (GTR) and near-total resection (NTR) groups. Significantly more cistern involvement was observed in the STR group than in the GTR group. The GTR, NTR, and STR rates were higher in grade 1, 3, and 2 cases, respectively. The subgroup 'a' was correlated with higher resection rates (GTR and NTR), whereas the subgroup 'b' was correlated with STR.

CONCLUSIONS

Our suggested classification system represents a simple and practical model that may guide neurosurgeons in predicting the goal of resection during surgical planning and in minimizing potential morbidity.

Endoscopic retrosigmoid keyhole approach in cerebellopontine angle tumors. A surgical cohort

INTRODUCTION AND OBJECTIVES

To determine the safety and efficacy of endoscopic keyhole surgery in patients with cerebellopontine angle tumours.

MATERIALS AND METHODS

This was a retrospective study of patients with cerebellopontine angled tumours treated by fully endoscopic retrosigmoid keyhole approach in a tertiary centre during a period of four years. Preoperative, transoperative and postoperative variables were analysed.

RESULTS

A number of 40 patients were included. The age average was 49.4 years and male/female proportion was 0.4-1. We found 31 vestibular schwannomas (77.5%), five meningiomas (12.5%), two cholesteatomas (5.0%) and two metastases (5.0%). Vestibular schwannomas Hannover type IIIb, IVa and IVb predominated. The surgical resection was total or near-total 92.5% of patients. Hearing preservation rate was 62.5% and acceptable facial function nerve function rate was 80% after six months. Hospital stay was 7.5 days. The total or near total resection and functionally preservation rate was high. Complications were unusual.

CONCLUSIONS

Endoscopic retrosigmoid keyhole approach represented a safe and efficient procedure in selected patients with cerebellopontine angle tumours.

Endoscopic Keyhole Approach for Intracranial Epidermoid

Objective  In contemporary neurosurgical practice, keyhole endoscopic approach has established its role in various neurosurgical pathologies. Intracranial epidermoid is an ideal pathology for endoscopic keyhole approach as epidermoid is well encapsulated, extra-axial, avascular, and easily suckable. The objective of this study is to share our experience of endoscopic keyhole approach for intracranial epidermoids at various locations as a new minimally invasive neurosurgical approach to deal with these lesions. Materials and Methods  We conducted a retrospective study on 26 patients who underwent keyhole pure endoscopic excision of intracranial epidermoid between July 2015 and December 2019. Patient's demographics, clinical features, radiological imaging, and postoperative complications were noted. Follow-up outcome of preoperative symptoms and postoperative complications were also analyzed. Results  The mean age of the study population was 30.5 years with a mean follow-up of 30 months. The common presenting features were headache, hearing loss, and trigeminal neuralgic pain. Gross total resection was achieved in 73.1% cases, while near total resection and subtotal resection were achieved in 19.2 and 7.7% cases, respectively. In the follow-up, maximal improvement was seen in trigeminal neuralgic pain (83%) and headache (66.7%). Major postoperative complications were facial nerve paresis, lower cranial nerve paresis, and transient facial hypoesthesia, most of which improved over time. None of the patients required resurgery till date. Statistical Analysis  Patients' data were analyzed using SPSS software version 23 (Statistical Package for Social Sciences, IBM, Chicago, United States). Conclusion  This study demonstrates that with careful patient selection, endoscopic keyhole excision of epidermoid is a good alternative to conventional microsurgical excision with comparable surgical and functional outcomes.

Importance of appropriate surgical approach selection for radical resection of cerebellopontine angle epidermoid cysts with preservation of cranial nerve functions: our experience of 54 cases

BACKGROUND

Although many reports state that only the lateral suboccipital retrosigmoid approach (LSO) should be used for removal of cerebellopontine angle (CPA) epidermoid cysts, it is preferable to use various surgical approaches as appropriate for each patient, for radical resection with an optimal operative field under direct visualization, and for the preservation of cranial nerve (CN) functions. In the present study, we hence focused on the importance of surgical approach selection for removal of CPA epidermoid cysts and analyzed the results of CPA epidermoid cysts after surgery in our series.

METHODS

Fifty-four patients who underwent surgery for CPA epidermoid cysts were retrospectively analyzed, regarding their surgical approaches, removal rates, preservation rates of CN function 1 year after surgery, and recurrence. Surgical approaches were selected for patients according to the size and extension of the tumor.

RESULTS

Surgical approaches consisted of LSO (20 cases), anterior transpetrosal approach (ATP; 3 cases), combined transpetrosal approach (27 cases), and ATP + LSO (4 cases). Mean tumor content removal and capsule removal rates were 97.4% and 78.3%, respectively. Preservation rates of facial nerve function and useful hearing were 94.4% and 90.7%, respectively. The mean postoperative follow-up time was 62.8 months, and there were two cases of recurrence requiring reoperation about 10 years after surgery.

CONCLUSIONS

For CPA epidermoid cyst surgeries, selection of the appropriate surgical approach for each patient and radical resection with an optimal operative field under direct visualization enable tumor removal without the need for reoperation for a long time, with preservation of CN functions.

Endoscopic retrosigmoid keyhole approach in cerebellopontine angle tumors. A surgical cohort

INTRODUCTION AND OBJECTIVES

To determine the safety and efficacy of endoscopic keyhole surgery in patients with cerebellopontine angle tumors.

MATERIALS AND METHODS

This was a retrospective study of patients with cerebellopontine angled tumors treated by fully endoscopic retrosigmoid keyhole approach in a tertiary center during a period of four years. Preoperative, transoperative and postoperative variables were analyzed.

RESULTS

A number of 40 patients were included. The age average was 49.4 years and male/female proportion was 0.4-1. We found 31 vestibular schwannomas (77.5%), five meningiomas (12,5%), two cholesteatomas (5,0%) and two metastases (5.0%). Vestibular schwannomas Hannover type IIIb, IVa and IVb predominated. The surgical resection was total or near-total 92.5% of patients. Hearing preservation rate was 62.5% and acceptable facial function nerve function rate was 80% after six months. Hospital stay was 7.5 days. The total or near total resection and functionally preservation rate was high. Complications were unusual.

CONCLUSIONS

Endoscopic retrosigmoid keyhole approach represented a safe and efficient procedure in selected patients with cerebellopontine angle tumors.

Extent of resection of epidermoid tumors and risk of recurrence: case report and meta-analysis

OBJECTIVE

Intracranial epidermoid tumors are slow-growing, histologically benign tumors of epithelial cellular origin that can be symptomatic because of their size and mass effect. Neurosurgical resection, while the treatment of choice, can be quite challenging due to locations where these lesions commonly occur and their association with critical neurovascular structures. As such, subtotal resection (STR) rather than gross-total resection (GTR) can often be performed, rendering residual and recurrent tumor potentially problematic. The authors present a case of a 28-year-old man who underwent STR followed by aggressive repeat resection for regrowth, and they report the results of the largest meta-analysis to date of epidermoid tumors to compare recurrence rates for STR and GTR.

METHODS

The authors conducted a systemic review of PubMed, Web of Science, and the Cochrane Collaboration following the PRISMA guidelines. They then conducted a proportional meta-analysis to compare the pooled recurrence rates between STR and GTR in the included studies. The authors developed fixed- and mixed-effect models to estimate the pooled proportions of recurrence among patients undergoing STR or GTR. They also investigated the relationship between recurrence rate and follow-up time in the previous studies using linear regression and natural cubic spline models.

RESULTS

Overall, 27 studies with 691 patients met the inclusion criteria; of these, 293 (42%) underwent STR and 398 (58%) received GTR. The average recurrence rate for all procedures was 11%. The proportional meta-analysis showed that the pooled recurrence rate after STR (21%) was 7 times greater than the rate after GTR (3%). The average recurrence rate for studies with longer follow-up durations (≥ 4.4 years) (17.4%) was significantly higher than the average recurrence rate for studies with shorter follow-up durations (< 4.4 years) (5.7%). The cutoff point of 4.4 years was selected based on the significant relationship between the recurrence rate of both STR and GTR and follow-up durations in the included studies (p = 0.008).

CONCLUSIONS

STR is associated with a significantly higher rate of epidermoid tumor recurrence compared to GTR. Attempts at GTR should be made during the initial surgery with efforts to optimize success. Surgical expertise, as well as the use of adjuncts, such as intraoperative MRI and neuromonitoring, may increase the likelihood of completing a safe GTR and decreasing the long-term risk of recurrence. The most common surgical complications were transient cranial nerve palsies, occurring equally in STR and GTR cases when reported. In all postoperative epidermoid tumor cases, but particularly following STR, close follow-up with serial MRI, even years after surgery, is recommended.

Clinical Features and Surgical Management of Cerebellopontine Angle Cholesteatoma That Presented as Trigeminal Neuralgia

BACKGROUND

It is difficult to differentiate patients with cerebellopontine angle (CPA) cholesteatoma and patients with primary trigeminal neuralgia just according to early symptoms. We aimed to explore the clinical characteristics, early diagnosis, and microneurosurgical techniques for CPA cholesteatoma that presented as trigeminal neuralgia.

METHODS

The data of 26 patients who complained trigeminal neuralgia with CPA cholesteatoma between January 2009 and December 2015 were collected and studied retrospectively, they were diagnosed by magnetic resonance imaging preoperatively and confirmed by pathology postoperatively. All the tumors were resected through a retrosigmoidal approach. In 26 cases, 14 patients who underwent cholesteatoma resection and microvascular decompression were assigned to group A and 12 patients who underwent only cholesteatoma resection were assigned to group B. The clinical features and surgical results between groups A and B were compared. The complications and surgical results were followed up, and surgical techniques were summarized.

RESULTS

All patients presented as trigeminal neuralgia at the same side of the cholesteatoma. There was no statistical difference between the 2 groups in clinical features and surgical results between groups A and B. All patients with cholesteatoma showed clear and significant imaging characteristics. The tumors were totally removed in 18 patients and subtotally removed in 8 patients. Pain relief was satisfactory in all patients. Surgical complications included transient aseptic meningitis in 2 patients, facial numbness in 2 patients, mild tinnitus in 2 patients, mild and facial weakness in 1 patient. No death, hematoma, or acute hydrocephalus were reported in this series. During the follow-up of 12-80 months, no patient experienced recurrence of pain or tumor.

CONCLUSIONS

Cholesteatoma of the cerebellopontine angle often presented as trigeminal neuralgia. Magnetic resonance imaging is helpful for early diagnosis according to its distinct signal. Surgical treatment is often the first choice, the neuralgia relief was satisfactory after operation. Microvascular decompression is recommended simultaneously if some offending vessels were founded during the surgical resection of the tumor.

Combined microsurgical and endoscopic technique for removal of extensive intracranial epidermoids

Background

Intracranial epidermoid tumors are challenging lesions because they grow along the subarachnoid spaces around delicate neurovascular structures and often extend from one compartment to another. The purpose of this study was to determine the usefulness of endoscopic assistance in the microsurgical resection of these lesions, in which total resection is therapy of choice.

Methods

A total of 48 cases of intracranial epidermoids were treated by combined microscopic and endoscopic techniques. Initially, the tumor was removed under the microscope and after ensuring maximum excision, the endoscope was used to find out and excise any residual tumor.

Results

Out of these 48 cases complete excision was achieved in 44 cases and subtotal excision in four patients. Postoperative complications were seen in 17 patients, but none of the complications was attributed to the use of endoscope. Overall use of endoscope benefited 79% of cases.

Conclusion

We recommend combined microsurgical and endoscopic approach to achieve complete/maximum resection of extensive intracranial epidermoid tumors.

Primary Epidermoid Tumors of the Cerebellopontine Angle: A Review of 47 Cases

OBJECTIVE

To analyze disease presentation, treatment, and clinical course of a consecutive series of patients with primary cerebellopontine angle (CPA) epidermoids.

PATIENTS

Forty-seven consecutive patients with previously untreated CPA epidermoids.

INTERVENTION(S)

Observation and microsurgery.

MAIN OUTCOME MEASURES

Disease- and treatment-associated morbidity, recurrence.

RESULTS

Forty-seven patients (mean age 39 years; 53% women) were analyzed and the average duration of follow-up was 42 months. The most common presenting symptom was headache (27; 57%); 13 (28%) exhibited preoperative asymmetric sensorineural hearing loss, 3 (6%) facial nerve paresis, and 3 (6%) hemifacial spasm. Thirteen patients (28%) were initially observed over a mean interval of 56 months; however, five experienced disease progression requiring operation. Thirty-nine patients (83%) underwent surgical resection; 18 (46%) received gross total, 5 (13%) near total, and 16 (41%) aggressive subtotal resection. Three patients (8%) recurred at a median of 53 months; two after subtotal and one after gross total resection. Ninety-three percent of patients with useful hearing maintained serviceable hearing following treatment and one patient (3%) experienced mild long-term postoperative facial nerve paresis (HB II/VI). All patients with preoperative facial nerve paresis recovered normal function postoperatively. There were no episodes of stroke or death.

CONCLUSIONS

Surgical intervention is effective in alleviating symptoms of cranial neuropathy and brainstem compression from CPA epidermoids. Gross total resection is preferred; however, aggressive subtotal removal should be considered with adherent or extensive disease as reoperation rates are low, even in the setting of aggressive subtotal resection. Conservative observation with serial imaging is a viable initial strategy in asymptomatic or minimally symptomatic patients.

Endoscopic-Assisted Median Aperture Approach for Resection of Fourth Ventricular Tumor and Confirmation of Patency of Cerebral Aqueduct Using an Adjustable-Angle Endoscope: Technical Case Report

BACKGROUND AND IMPORTANCE: Open microsurgical approaches to the roof of the fourth ventricle via a telovelar approach typically require cerebellar retraction and/or splitting of the vermis and may be associated with postoperative neurological morbidities. In this case report and technical note, we describe the use of an adjustable-angle endoscope inserted into the median aperture via suboccipital craniotomy, resulting in enhanced visualization of the roof of the fourth ventricle and cerebral aqueduct and maximal safe tumor resection.

CLINICAL PRESENTATION: A 49-yr-old woman with obstructive hydrocephalus and a fourth ventricular mass that was not fully visible with the use of an operative microscope.

CONCLUSION: Direct visualization of the roof of the fourth ventricle, including the superior medullary velum and cerebral aqueduct, can be facilitated with an adjustable angle endoscope inserted into the median aperture via suboccipital craniotomy to minimize the degree of telovelar dissection and vermis splitting.

Endoscopic Treatment of a Third Ventricular Epidermoid Cyst

Epidermoid cyst is a benign and congenital lesion of ectodermal origin. Traditionally, microsurgical techniques are used to treat these lesions, and their occurrence in the third ventricle is rare. Here, the authors report a case of epidermoid cyst in the third ventricle that presented with signs and symptoms of intracranial hypertension, which was treated safely and effectively using neuroendoscopic surgery.

Cerebellopontine angle epidermoid cysts: clinical presentations and surgical outcome

Epidermoid cysts constitute less than 1% of intracranial tumors with the majority of them involving cerebellopontine angle (CPA). Although several mechanisms for cranial nerve dysfunction due to these tumors have been proposed, no direct evaluation for hyper- or hypoactive dysfunction has been done. In this case series, pathophysiology of cranial nerve dysfunction in CPA epidermoid cysts was evaluated with special attention to a new mechanism of capsule strangulation caused by stratified tumor capsule. Twenty-two cases with epidermoid cysts of CPA micro-neurosurgically treated in our departments since 2005 were reviewed. Clinical status of the patients before the surgery and post-operative functional outcome were recorded. Available data from the English literature were summarized for comparison. Mass reduction of cyst contents in most cases was usually associated with prompt and marked improvement of the symptoms suggesting neuroapraxia caused by compression of the tumor content and/or mild ischemia. Among them, two cases showed strangulation of the affected nerves by the tumor capsule whose preoperative dysfunction did not improve after surgery in spite of meticulous microsurgical removal of the lesion. Involved facial and abducent nerves in these two cases showed distortion of nerve axis and nerve atrophy distal to the strangulation site. We report the first direct evidence of etiology of cranial nerve dysfunction caused by cerebellopontine angle epidermoid tumors. Young age and rapidly progressive neurological deficit might be the characteristics for strangulation of the affected nerves by the cyst capsule. Even though the number of cases might be limited, immediate decompression and release of the strangulating band might be urged in such patients to prevent irreversible deficits.