Keywords
cerebellopontine angle - epidermoid cyst - capsule remnants
Introduction
Intracranial epidermoid cysts (ECs) are congenital benign cysts with an incidence
of 1% of all brain tumors.[1] Almost half of ECs occur in the cerebellopontine angle (CPA), accounting for 5 to
7% of tumors in this location and the third most common brain tumor after schwannomas
and meningiomas in the CPA.[2] It may occur in other locations such as the suprasellar and the temporal regions.[3]
ECs are slowly growing and may present with symptoms of elevated intracranial pressure
(ICP) or symptoms of cerebellar, brainstem, and/or cranial nerves dysfunction.[4]
MRI is the investigation of choice with diffusion-weighted imaging sequence that distinguishes
EC from arachnoid cyst.[5]
Surgery is the best treatment choice which shows good results. Surgical treatment
for these lesions appears to be difficult due to the cyst capsule's strong adherence
to surrounding structures, and its ability to invade multiple cisterns. The clinical
course after surgical resection of EC is however not clearly documented in the literature.[3]
The aim of this study was to evaluate the clinical and radiological outcomes of surgically
treated EC in the CPA region.
Materials and Methods
This study represents a retrospective review of patients surgically treated for symptomatic
EC in the CPA region in the neurosurgery department of Cairo University Hospitals
in the period January 2015 to December 2017.
The initial diagnosis was based on CT and MRI appearance and was histologically confirmed
in all cases. Data were retrospectively collected from clinical, surgical, pathological,
and radiological records.
All patients included in this study were followed-up postoperatively both clinically
and radiologically for, at least, 2 years. The follow-up period ranged from 24 to
38 months. The mean follow-up period was 28.5 months.
Clinical outcome was assessed in terms of improving and worsening of the presenting
symptoms. Radiological outcome was assessed by comparing the tumor size, brainstem
and cerebellar compression in the preoperative and postoperative images. The results
were compared with the literature.
All cases included in this study have signed our institutional consent before performing
their surgeries, including their approval of participation in any future studies.
The authors report no conflict of interest concerning the materials or methods used
in this study or the findings specified in this paper.
Results
A total of 18 cases with CPA ECs were surgically treated in our department during
the study period. Patients demography: The age of the cases ranged from 17 to 53 years,
with the mean age being 38.6 years. There was a female predominance among cases that
were included in this study as there were 11 females (61.1%) and 7 males (38.9%).
Preoperative clinical condition: all cases were symptomatic. Trigeminal neuralgia
was the most common, presenting symptoms in 11 patients (61.1%), followed by facial
nerve palsy in 5 patients (27.8%) and hearing impairment in 2 patients (11.1%). Multiple
cranial nerve affection was seen in four patients (22.2%). Headache and blurring of
vision were present in seven patients (38.9%). Ataxia was present in five patients
(27.8%).
Surgical details: All cases were operated upon by microsurgical evacuation of the
cyst contents and excision of the nonadherent parts of the capsule. Seven patients
needed ventriculoperitoneal (VP) shunt in the same setting due to the presence of
hydrocephalus.
Clinical outcome and complications: Improvement or resolution of preoperative symptoms
was seen in 13 patients (72.2%). Hearing impairment did not improve in two patients
(11.1%) in the follow-up period. Preoperative symptoms worsened in two patients (11.1%).
One patient presented with facial nerve palsy House–Brackman GII, which preoperatively
progressed to GIV postoperatively. The other patient was presenting with partial bulbar
symptoms preoperatively which increased postoperatively. New postoperative symptoms
(facial nerve palsy, House–Brackman GII) occurred in one patient presenting with trigeminal
neuralgia. During the follow-up period, symptomatic recurrence (trigeminal neuralgia)
occurred in one patient after 26 months. No cases of postoperative chemical meningitis
and/or hydrocephalus were reported in our study.
Radiological improvement regarding cerebellar and brain stem compression was seen
in all patients. Asymptomatic recurrence occurred in one case in the follow up MRI
images ([Figs. 1]
[2]
[3]).
Fig. 1 Pre- and postoperative images of a 44-year-old male presenting with ataxia and multiple
cranial nerve affection (trigeminal neuralgia for 4 months, facial nerve palsy [GII]
and partial bulbar symptoms). Postoperative images show gross total excision of the
CPA ECs with marked decrease in the preoperative brainstem and cerebellar compression.
The patient had a smooth postoperative recovery with improvement of preoperative symptoms.
CPA, cerebellopontine angle; EC, epidermoid cyst.
Fig. 2 Pre- and postoperative images of a 38-year-old male presenting with multiple cranial
nerve affection (trigeminal neuralgia for 1 year, facial nerve palsy, and hearing
impairment). Postoperative images show gross total excision of the CPA ECs. The patient
had a smooth postoperative recovery with improvement of the trigeminal and facial
nerves’ symptoms, while he showed no improvement regarding hearing. CPA, cerebellopontine
angle; EC, epidermoid cyst.
Fig. 3 Pre- and postoperative images of a 36-year-old female presenting with signs of multiple
cranial nerve affection. Postoperative images show gross total excision of the CPA
ECs. The patient had a smooth postoperative recovery with partial improvement of the
preoperative symptoms. CPA, cerebellopontine angle; EC, epidermoid cyst.
Discussion
Intracranial ECs are slowly growing, congenital anomalies occurring most commonly
in the CPA. Due to the gradual mass effect,[3] ECs symptomatize in a wide range of age (between 20 and 60 years) with peak occurrence
at around 40 years of age.[5]
[6]
[7] In our study, there was a slight female predominance compared with other studies
which reported similar incidence in both genders.[5]
[6] This may be due to the smaller number of patients in our study.
The most common presenting symptoms are trigeminal neuralgia and hearing impairment,
followed by dizziness, headaches, diplopia, and facial nerve affection.[5]
[6] Similarly, trigeminal neuralgia was the most common presenting symptom occurring
in 61%of the patients in our study group. However, facial palsy (27.8%) was a more
common symptom than hearing impairment (11.1%) in our study.
ECs are not well-circumscribed, having irregular lobulated surfaces which usually
grow and adhere to nerves and vessels or enclose them. Therefore, surgery is challenging,
and incomplete excision is common due to the interaction with critical structures,
as gross total excision can bring a high-risk of morbidity.[3] We believe that leaving the adherent part of the capsule in place is mandatory to
reduce the possibility of neurological sequelae.
Due to the linear pattern of EC growth, a symptomatic tumor recurrence may be expected
after a period comparable in length to the period between birth and the time taken
for the primary tumor to become symptomatic.[8] Although a residue of a capsule will likely result in recurrence, this will occur
many years after surgery. Berger et al[9] stated that recurring symptoms can take 30 to 40 years to develop, a finding which
supports the rationale for avoiding radical excision. Furthermore, several studies
have found no difference in the recurrence risk between totally and incompletely excised
lesions.[6]
[10] Thus, near total excision of the tumor, leaving only tiny remnants, in a middle
aged patient can be considered as clinical cure.[2]
Associated hydrocephalus is said to be uncommon due to the long-standing nature of
the lesion.[3] However, in the present study, 38.9% had hydrocephalus and required VP shunt. Similarly,
in a previously reported series, 12 out of 30 patients (40%) required shunt surgery
for hydrocephalus.[11]
The temporary worsening of symptoms is likely due to nerve manipulation or partial
damage during surgery.[3]
[10]
[12] In the previously reported studies, a relatively high-incidence of postoperative
cranial nerve dysfunction was identified which appeared to recover during the follow-up
period in most cases.[9]
[13]
[14] In our study, there was a low-incidence of cranial nerve dysfunction postoperatively,
since the adherent tumor capsule was left behind. This was observed in two (11.1%)
of our patients, where one patient progressed to House–Brackman GIV facial palsy from
GII preoperatively, which gradually improved in the follow-up period. The other patient
was presenting with partial bulbar symptoms preoperatively which increased postoperatively.
New postoperative symptoms in the form of facial nerve palsy House–Brackman GII occurred
in one patient presenting with trigeminal neuralgia which rapidly recovered.
The postoperative complication rate in our series was 16.6% with no mortalities. Close
values have been reported previously.[3]
[15]
[16] A particular clinical complication of EC is aseptic meningitis, which is due to
the spill of cholesterol crystals into the cerebrospinal pathway.[11]
[13]
[17] The incidence of aseptic meningitis ranges from 0 to 18.2%.[10]
[12] Continuous intraoperative CPA cistern irrigation with hydrocortisone solution and
delayed postoperative steroids withdrawal were recommended as potential measures to
avoid chemical meningitis.[9]
[11]
[17] In the present study, the same protocol was implemented in all patients and this
complication was not reported.
Communicating hydrocephalus may develop after meningitis or following cyst content
leakage from the surgical field.[9]
[11]
[18] There was no postoperative hydrocephalus in our series which needed CSF diversion.
We assume that regular perioperative corticosteroid administration and surgical field
irrigation with hydrocortisone solution and saline reduces the risk of postoperative
hydrocephalus development.
Follow-up MRIs are needed for recurrence assessment.[5]
[6]
[12] Most authors agree that surgery is needed in the event of a deterioration of a chronic
neurological disability or the emergence of a new impairment due to tumor growth and
not simply because of the detection of tumor regrowth in imaging studies.[2]
[6]
[12] In the present study, radiological improvement regarding cerebellar and brain stem
compression was seen in all patients. Radiological recurrence occurred in two (11.1%)
patients in the follow-up period. Symptomatic recurrence (trigeminal neuralgia) occurred
in one patient after 26 months and required reoperation. Asymptomatic recurrence occurred
in the other patient, which was detected in the follow up MRI 32 months after surgery,
and no surgery was done to this patient, as surgery is often indicated only when the
recurrent lesion is symptomatic.[18]
Conclusion
Surgical management of EC in the CPA region, leaving remnants of the capsule on blood
vessels, nerves, and brain stem can be considered as a relatively safe surgical procedure
with a good clinical outcome and low-recurrence risks.
