|Year : 2020 | Volume
| Issue : 3 | Page : 144-149
Clinical, radiological and microneurosurgical aspects in the management of intracranial epidermoid cysts: Experience with 38 cases
VV Ramesh Chandra, BC M. Prasad, Niranjan Vayyala, Rajesh Paradesi
Department of Neurosurgery, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
|Date of Submission||18-Dec-2019|
|Date of Decision||04-Apr-2020|
|Date of Acceptance||07-Apr-2020|
|Date of Web Publication||27-Oct-2020|
Assistant Professor, Department of Neurosurgery, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Objectives: There is considerable debate in the surgical management of epidermoid cyst whether gross total or subtotal resection yields better long term outcomes. We present our institutional experience in evaluating the clinical presentation, diagnosis and surgical strategy and extent of resection in the management of intracranial epidermoid cyst.
Methods: We retrospectively reviewed the case records of 38 patients with intracranial epidermoid tumors surgically treated at our institution between 2010 and 2019.
Results: A total of 38 patients who underwent surgery for intracranial epidermoid lesions were identified. Of these 17 were supratentorial, 20 were infratentorial lesions and one case lesion was extending from cerebellopontine region to middle fossa. The mean duration from onset of symptoms to surgery was 3.9 years. Cranial nerve dysfunction was noted in 73% of patients preoperatively most of them being the Cerebellopontine angle epidermoids. Total removal was achieved in 28 patients, near-total removal in 8 patients, and subtotal removal in 2 patients. 6 patients developed recurrence radiologically of them only one patient became symptomatic. Of the six 2 were patients who underwent gross total resection and the remaining 4 were from near and subtotal resection. The mean duration of follow-up was 3.8 years. The content of the tumor was pearly white/white material in all cases. complications noted in the present series were not related to the completeness of excision. Mortality was noted in one patient.
Conclusions: The present study highlights various precautions to be taken intraoperatively in the prevention of development of aseptic meningitis and concludes that total removal of epidermoids does not result in significantly increased morbidity and mortality and should be the goal of surgical treatment. However, near/subtotal resection oflesions that are densely adherent to neurovascular structures is justified, as there is no significant difference in the rate of recurrence. An endoscope can be used to assess the completeness of surgery.
Keywords: Cystic lesion of the brain, epidermoid cyst, the extent of resection
|How to cite this article:|
Ramesh Chandra V V, M. Prasad B C, Vayyala N, Paradesi R. Clinical, radiological and microneurosurgical aspects in the management of intracranial epidermoid cysts: Experience with 38 cases. J Clin Sci Res 2020;9:144-9
|How to cite this URL:|
Ramesh Chandra V V, M. Prasad B C, Vayyala N, Paradesi R. Clinical, radiological and microneurosurgical aspects in the management of intracranial epidermoid cysts: Experience with 38 cases. J Clin Sci Res [serial online] 2020 [cited 2020 Nov 25];9:144-9. Available from: https://www.jcsr.co.in/text.asp?2020/9/3/144/298951
| Introduction|| |
An epidermoid cyst (EC) is a rare, congenital extra-axial lesion which constitutes about 0.2%–2% of all brain tumours. Also known as cholesteatomas, these benign lesions grow slowly by piling of keratin and cholesterol, the degradation products of desquamated epithelial cells. Walter Dandy called EC as 'most beautiful tumour of the body' because of its smooth, glistening exterior surface. Cruveihier, a French pathologist, reported EC as pearly tumours due to their similar external appearance. The sluggish growth and soft texture of cholesterin allow growing along with the cisterns of the skull base with gradual adaptation to the neurovascular bundles. Hence, the patient is free of any symptoms in the initial period. Symptoms tend to occur due to the mass effect and compression of cranial nerves (CN). Cerebellopontine angle (CPA) and para sellar region are common sites due to the lateral movement of ectodermal cells by developing otic vesicles. As EC is sensitive neither to chemotherapy nor to radiation, surgical resection constitutes the particular treatment modality. There is continued debate regarding the extent of resection (EOR), whether gross total tumour removal (GTR) or subtotal tumour removal (STR), be chosen. Through this article, we try to put forth our institutional experience in the microneurosurgical management of EC.
| Material and Methods|| |
From January 2010 to July 2019, 38 patients with intracranial EC who underwent surgery in Sri Venkateswara Institute of Medical Sciences were included in the present study. Conservatively treated cases were excluded from our study. Symptom duration at the time of admission, imaging findings, operative findings and post-operative outcomes were retrospectively studied. All patients underwent computed tomography (CT) and magnetic resonance imaging (MRI) for pre-operative diagnosis, surgical decision-making and in subsequent outpatient visits after discharge for detecting recurrence. Although the goal of surgery was the total gross removal of the tumour, to provide a better quality of life, post excision, safeguarding neurovascular structures was given utmost importance. The EOR was categorised as total if the lesion was completely removed along with its capsule; it was termed as near-total if the entire tumour was removed, but part of capsule was left behind and it was termed as subtotal if only some part of tumour and capsule was excised. The amount of tumour removed was ascertained by verifying operative notes and follow-up imaging. CT brain was done within a day of surgery in all the 38 patients post excision to look for any bleed in the tumour bed and any other surgery-related complications. All patients were followed-up post-surgery in the neurosurgery out-patient service at our institute.
| Results|| |
Their mean age was 34.1 (range 19-56) years. The majority of the patients were in the fourth decade. Females (n = 24) out-numbered males. The average time interval from onset of symptoms to institution of surgery was 3.9 years. The mean duration of symptoms was 1.6 years for the infratentorial group to 4.8 years for the supratentorial group. Seventeen cases were supratentorial; 20 were infratentorial. In one case, the EC was involving both the supratentorial and infratentorial regions [Figure 1]. Among the supratentorial epidermoids, four cases were interhemispheric, five were basifrontal, one was suprasellar, three were intraventricular (lateral ventricle) and three were in the temporal region. Among the supratentorial cases, headache and epilepsy were common; in suprasellar cases, vision loss and vomiting were noted and in temporal cases, memory deficits were noted [Table 1]. Among infratentorial cases, 13 were in CPA and seven cases in fourth ventricle. The involvement of a group of CN and cerebellar dysfunction was common in posterior fossa EC, particularly in CPA epidermoids. Among the CPA epidermoids, TN was noted in six patients. Facial weakness and facial spasms were observed in two patients; hearing loss was recorded in two patients. [Table 2] depicts clinical features in infratentorial EC. Multiple CN deficit is a significant feature in CPA epidermoids. Six out of the 38 patients presented to emergency with features of acute hydrocephalus: four of them were taken for definitive surgery immediately and the remaining two underwent cerebrospinal fluid (CSF) diversion procedure with final surgery done at a later date. Radiological confirmation of diagnosis was done in all cases. CT showed a hypodense lesion with no enhancement on contrast. On MRI study, T1-weighted imaging (WI) lesion was hypointense and the T2-WI lesion was hyperintense. However, on diffusion weighted imaging (DWI), there was restricted diffusion, which was diagnostic.
|Figure 1: Epidermoid cyst of a patient from study (a) computed tomography scan image showing large hypodense lesion involving the middle fossa and extending infratentorially to the posterior fossa, (b) diffusion-weighted imaging of the same patient showing diffusion restriction, (c) magnetic resonance imaging sagittal cut showing extension of the lesion infratentorially to brain stem anteriorlaterally on left side, (d) immediate post-operative computed tomography scan of the same patient who underwent subtemporal excision of the cyst some part of the cyst which is anterior and lateral to brainstem was left behind which can be seen on the scan. The patient is under regular follow-up. CT=Computed tomography; MRI=Magnetic resonance imaging|
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The site and extent of EC determined the operative approach. In the case of supratentorial intraventricular epidermoid, the plan was interhemispheric transcallosal approach. Pterional approach with dissection of Sylvian fissure was used in suprasellar EC. For all CPA epidermoids, the approach was a suboccipital retrosigmoid retromastoid craniectomy [Figure 2]. Transvermian approach was preferred in the fourth ventricular EC following a midline suboccipital craniectomy. Necessary intraoperative precautions like covering exposed brain parts by cotton pledgets avoid the spillage of cystic contents into cisternal spaces, removing the EC removed in piecemeal method, gradual decompression which creates a plane between the capsule and surrounding vessels, removing the capsule by sharp dissection, not forcefully excising capsule tightly adherent to neurovascular structures were followed during to minimise the occurrence of complications. Other preventive measures during surgery included ensuring that the remaining capsule was not coagulated; continuous washing of cisternal spaces with hydrocortisone solution mixed in Ringer's lactate and post-operative steroid coverage to prevent the development of chemical meningitis. Mastoid air cells, sinus accidentally opened during craniotomy, were tightly sealed off. Endoscopic assistance was taken intraoperatively to assess the amount of tumour left. The advantage of the endoscope is it gives an improved angle of vision than the microscope and avoids the need for excessive brain retraction and reduces the need to open more dura. Any new deficit that developed in the immediate postoperative period is shown in [Table 3].
|Figure 2: Magnetic resonance imaging showing cerebellopontine angle epidermoid extending anterior to basilar artery on to the opposite side (a). Diffusion-weighted imaging showing restriction (b). Operative picture of the patient with lesion and marking of incision for undergoing retrosigmoid retromastoid suboccipital craniectomy (c). After opening of the dura and placing spathula to retract cerebellum and visualising the lesion (d). Pearly white lesion seen along with fifth and seventh cranial nerves (e).|
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Gross total resection (GTR) was not possible in 10 patients; in three cases, part of the capsule was tightly attached to the pons, so it was not excised, and in two cases, the capsule was encasing the vessels in the CPA region. Subtotal resection (STR) was done in two cases, and these two cases are in regular follow-up. There is no change in the growth pattern of residual until now. Near-total excision was done in eight cases. All these patients are also in regular follow-up. The remaining 28 cases underwent complete excision of the tumour as confirmed by MRI. In five cases, endoscope was used to assess the amount of resection. All the 38 patients underwent an immediate CT of the brain after extubation following surgery to check for any operation-related complications. Some patients with pre-operative auditory impairment did not regain auditory function even after the complete excision of the tumour. However, out of the six patients with trigeminal neuralgia (TN), four had a full recovery and the remaining two had delayed recovery. In our experience, EC patients with TN had a better prognosis. The neurological deficits present before removal of the lesion and their course are shown in [Table 4].
Average duration of of follow-up was 3.8 ± 0.3 years. Following surgery, three patients developed hydrocephalus as a sequela of meningitis; all three of them underwent CSF diversion procedures. The complication was specific to the site of a tumour in a few cases of posterior fossa EC. Short-term seventh nerve palsy, CSF leak, the formation of pseudo meningocele, CSF rhinorrhoea, diplopia and difficulty in swallowing due to lower cranial nerve palsy. Complications regarding intra-ventricular EC were post-operative seizures, and one patient had post-operative opposite side weakness, which relieved entirely in due course. One interhemispheric EC patient died due to recurrent seizures and meningitis. [Table 5] shows a comparison of the results of the present study with various studies in the literature.
|Table 5: Comparison of the present study with various other studies in literature|
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| Discussion|| |
Literature suggests most of the intracranial EC patients to be around 20–40 years of age. Our experience has been similar. While there is no mention of gender preponderance in published literature,,, females (n = 24) outnumbered males in our study. Studies,, indicate the most common location of EC to be the CPA region; we observed that 13 of the 38 patients had EC in the CPA region. Epidermoids in the spinal region are uncommon. The average duration of clinical features was less in an infratentorial group than that in the supratentorial group because of less volume of posterior fossa and compact arrangement of structures; in other words, infratentorial group of patients presented early than those in the supratentorial group, which was correlating with literature. The mean duration of symptoms in the present study was 1.6 years for the infratentorial group to 4.8 years for the supratentorial group. As EC grows very slowly, clinical features take more time to manifest. Headache, convulsions, lapses in memory and features of hydrocephalus are seen as the presenting symptoms of supratentorial epidermoids. Posterior fossa epidermoids cause symptoms due to compression on the cranial nerve and cerebellum. TN, difficulty in hearing, vertigo, headaches, double vision and seventh nerve palsy are the most common symptoms of CPA region EC. In our experience, we noted that six patients had TN and two patients had hemifacial spasms. EC can displace the vessel towards the nerve, which can compress it and may result in TN and hemifacial spasm. It can also occur due to the pushing of the nerve towards the vessel. In patients with EC, hemifacial spasm results only in the place of neurovascular conflict. At the same time, TN can also occur in the absence of EC due to arachnoid adhesions or venous pathology. The explanation behind this is the length of the Redlich–Obersteiner zone, which is affected by direct compression or displacement. The length of this zone in the fifth cranial nerve is thrice than that in the seventh cranial nerve (2.2 mm vs. 0.8 mm). This explains the increased incidence of TN in patients with EC than hemifacial spasm with EC, which is confirmed in our study also.
Further, our observations suggest that EC with TN has a better prognosis than EC patients with hemifacial spasm. Sometimes, patients with EC can attend to emergency with repeated attacks of meningitis. Although this is very uncommon, this occurs due to the release of irritant cystic contents into the cisternal spaces spontaneously (chronic aseptic meningitis). In our study, we did not encounter any such patient. The signs and symptoms of patients in this group were similar to those in literature. MRI T1W1 and T2WI of EC showed low signal and high signal intensity, respectively. DWI is essential and diagnostic in EC. DWI shows restricted diffusion and hyperintensity. This feature differentiates the EC cyst from other cystic lesions of the brain. Fluid-attenuated inversion recovery (FLAIR) and DWI can be used to determine the solid nature of EC. DWI is more informative than other MR sequences in outlining the extent of the EC. On FLAIR, the middle part of EC is hyperintense relative to the hypointense CSF. There is no enhancement of the capsule on the administration of contrast. It is essential to differentiate EC from other cystic lesions of the brain preoperatively so that while doing surgery, precautions can be taken to prevent the occurrence of aseptic meningitis. Arachnoid cyst typically occurs in the middle cranial fossa. Arachnoid cyst is hypointense on FLAIR and DWI; an EC shows a high signal on FLAIR and restricted diffusion on DWI. Dermoid and EC are benign, congenital, rare lesions of the brain. Dermoid differs in that it has an increased tendency to occur in midline and has dermal appendages like hair and teeth as its contents. Dermoid is hypodense on CT, hyperintense on T1WI and hypo-hyper on T2WI and shows restricted diffusion and increased signal intensity on FLAIR. Dermoid is a fast-growing lesion and produces symptoms at a younger age, in contrast to very sluggishly growing EC. Hydatid cyst, mostly single cystic lesion, occurs in the area of perfusion of the middle cerebral artery and large unilocular without any surrounding oedema. Daughter cysts are present in hydatid cyst on imaging and have a similar intensity to that of CSF. Classical epidermoids are black epidermoids as they are hypointense on T1WI. Rarely, atypical epidermoids are hyperintense on T1WI and hypointense on T2WI, and no restriction on diffusion is noted. These atypical epidermoids are white epidermoids. This change in intensity is due to the high viscous nature of their contents. High viscosity is due to increased protein, rich lipid (along with triglycerides) and absence of cholesterol. Typical black epidermoids are solid and have cholesterol and no triglycerides. Malignant transformation of epidermoids can be suspected when an EC shows the presence of oedema and tissue invasion, rapid growth and new enhancement on contrast. Immunohistochemistry of the malignant EC reported in the literature showed the positivity of tumour cells with P53 protein. Histological diagnosis is confirmatory.
There is no definite opinion regarding the EOR of EC in literature. In a study GTR was reported in the majority of patients with minimal morbidity, and the recurrence rate was also less. In another study GTR was not attempted, but no recurrence was reported during the follow-up period. In our experience, STR was done in 10 patients and 28 underwent GTR. The post-operative complication rate was more in patients who underwent GTR in our study. Preservation of neurovascular structures with complete removal of EC is the main aim of surgery. Still, it is difficult to achieve in all cases due to the tight attachment of capsule to structures lying beneath. A study highlighted that neurological outcome postoperatively depends on the status of pre-operative nerve function, which is similar to our study.
Intraoperatively, there may be spillage of cystic contents into cisternal spaces, causing chemical meningitis, which can be short term and can subside on its own but may be troublesome in few cases. This can be prevented by the washing of cisternal continuously intraoperatively during dissection with corticosteroid solution and usage of steroids in the post-operative period. Intraoperatively, we irrigated the operative field continuously with hydrocortisone (100 mg/1 L of RL solution). Single mortality was noted in our study; it was a case of interhemispheric EC. Death was due to seizures and chronic meningitis. To eliminate the risk of regrowth from residual, the aim was always to remove the tumour completely, but the majority of articles in the literature suggest no change in the rate of recurrences between GTR and STR of EC.
Intraoperatively using endoscope helps the operating surgeon to view the corners of the operating field to assess the amount of tumour resected. Thus, endoscope assistance reduces the need to remove more bone, and there is no need for unnecessary retraction of the brain. In a study, the authors reported their experience with endoscope-assisted microsurgery in the treatment of 205 brain tumours. The authors, did not report whether their patient population included EC or other CPA tumours. However, they, concluded that endoscope assistance might reduce the trauma related to resection and improve operative outcomes. Video-endoscope-assisted microsurgery was done only in four cases in our experience. We did not face any complications in any of these procedures due to endoscope usage. The drawback of the present study is less amount of follow-up period and research being a retrospective study; there are certain limitations.
Most of the brain tumours grow by multiplication of cells, whereas uncommon benign tumours such as EC grow slowly by the accumulation of breakdown products, desquamation of epithelial cells. EC is avascular, fragile, pearly white tumour, which is soft and irregular shaped lesion that can be easily excised. During surgical excision of most tumours on opening, the dura brain will be tense, but the brain will be lax and easily retracted, making its excision easy. Complete removal of EC is the treatment of choice with utmost care to preserve the neurovascular structures. Capsular resection is the most crucial step in GTR. Care should be taken during this step to prevent injury to the underlying structures. CPA epidermoids almost always presented with multiple neurological deficits. Most of the deficits take more time to resolve even after complete resection. Some may not resolve completely. Complete relief was noted in EC patients with TN. In CPA epidermoids, it is better to follow-up on a residual patient rather than producing a permanent neurological deficit in the pursuit of total resection as EC is very slow growing. Hence, the time taken by a recurrent tumour to produce symptoms is long. Use of steroids intraoperatively and in the post-operative period and continuous irrigation of cisterns with steroid solution intraoperatively and placing cotton pledgets over the brain can minimise the incidence of aseptic meningitis. Endoscope-assisted microsurgery can help operating surgeons by providing a vision of the operating field from a different angle, thereby reducing the need for brain retraction, and it can also help in assessing the amount of tumour still left. However, in our study, we did not try to excise the tumour with the endoscope alone.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]