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|LETTERS TO EDITOR
|Year : 2019 | Volume
| Issue : 1 | Page : 278-281
Microsurgical treatment of interhemispheric epidermoid: An institutional series
Sumit Bansal, Rabi N Sahu, Ashis Patnaik
Department of Neurosurgery, All India Institute of Medical Sciences, Bhubaneswar, Odisha, India
|Date of Web Publication||7-Mar-2019|
Dr. Sumit Bansal
Department of Neurosurgery, All India Institute of Medical Sciences, Bhubaneswar, Odisha
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Bansal S, Sahu RN, Patnaik A. Microsurgical treatment of interhemispheric epidermoid: An institutional series. Neurol India 2019;67:278-81
Bailey and Cushing  first described the epidermoid cyst in the early 1920s. These lesions are benign, slow growing, extra-axial, rare lesions accounting for approximately 0.5–1.5% of all brain tumors. These tumors are usually congenital, thought to arise from displaced epithelial remnants that remain after the neural tube closure. Cerebellopontine angle, petrous apex, suprasellar region, and the fourth ventricle are the usual locations, but they are very rare in the interhemispheric fissure., They usually present with seizures. Here we are sharing our experience in the management of four such cases.
From 2015 to 2016, four patients (1 female and 3 male) with an interhemispheric epidermoid were operated at our center. The patients' age ranged from 24 to 35 years. Preoperative computed tomography (CT) and magnetic resonance imaging (MRI) brain were obtained in all four patients. Histological specimens were obtained for all patients.
Out of the four patients in our series, two patients were having seizures in the preoperative period. One patient had right hemiparesis. The tumor was present predominantly on the right side in two patients and was left sided in another two patients, which helped in planning the side of craniotomy.
All four patients were operated by the interhemispheric approach. The predominant side of the tumor determined the side of craniotomy. Special care to preserve the bridging veins was taken while dissecting the interhemispheric fissure. Intermittent fixed retraction was used in all cases. The overlying cortex was retracted to reach the tumor. In the third case, there was a thin overlying cortex, so a retractor easily retracted it. Microscopic was used in all cases. Endoscopic interhemispheric approach  is well established in reducing the amount of retraction as per literature but was not used in our series due to nonavailability of endoscope in our center at that time. After excision of the tumor, the operative cavity was irrigated with saline and steroid solution. A watertight dural closure was done in all cases. The operative time ranged from 3 to 5 h (mean = 4 h). The mean blood loss in each surgery was 220 ml (range = 200–300 ml). The extent of tumor excision was total in all four cases. Perioperatively, the patients were managed with steroids, which were gradually tapered off. Postoperative CT scan was done in all four cases. Two patients had seizures in the immediate postoperative period, one of whom was managed with a second antiepileptic drug but the other patient had postictal weakness in the left lower limb (0/5), which gradually recovered over a period of time. Other two patients had an uneventful postoperative course [Table 1]. Histopathological examination of the excised tissue confirmed the diagnosis of epidermoid cyst in all four cases.[Figure 1], [Figure 2], [Figure 3], [Figure 4].
|Figure 1: (Case 1) Preoperative MRI of the brain showing that the lesion was hyperintense on T2-weighted image [axial (a), sagittal (b), coronal (c) views].Postoperative CT head [axial (d), sagittal (e), coronal (f) views] is showing a good operative cavity with no residual tumor on diffusion-weighted image (g)|
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|Figure 2: (Case 2) Preoperative MRI brain showing that the lesion was hyperintense on T2-weighted image [axial (a), sagittal (b), coronal (c) views] with restricted diffusion on diffusion-weighted image (d). Postoperative CT head (axial view) is showing a good operative cavity (e)|
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|Figure 3: (Case 3) Preoperative MRI brain showing that the lesion was hyperintense on T2-weighted image [axial (a) and coronal (c)] and hypointense on T1-weighted image [sagittal (b) views] with restricted diffusion on diffusion-weighted image (d). Postoperative MRI is showing a good operative cavity with no residual tumor on diffusion-weighted image (e)|
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|Figure 4: (Case 4) Preoperative MRI brain showing that the lesion was hyperintense on T2-weighted image [axial (a) and coronal (c)] and hypointense on T1 weighted image [sagittal (b) views]. Postoperative CT head (coronal view) is showing good operative cavity (d)|
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The follow-up period ranged from 6 months to 2 years (mean = 14.5 months). All four patients were able to return to their regular life with none or minimal neurological sequelae. Till the last follow-up, all patients were seizure-free and on continuing antiepileptics. We preferred to wait for at least 2 years with a seizure-free interval before tapering the antiepileptics. There was no mortality in our series. Only three patients had diffusion-weighted images, and the remaining patient had lost images in the follow-up period. No recurrence was noted in any patient till the last follow-up. The available published series are limited and summarized [Table 2].
These tumors are soft and slow growing, and so mould according to surrounding structures and seep in the crevices of the cisterns. The patients generally present with symptoms between the ages of 20–40 years. The patients can present with dementia secondary to obstructive hydrocephalus or manifest the local effect of the tumor such as seizures. In the present series, there was a male predominance, with the male to female ratio being 3:1, contrary to no gender preponderance in other series.
Epidermoids typically appear as low attenuation cystic masses on a CT scan due to the fluid and lipid contents. MRI appears to be the best modality for radiological evaluation of these tumors. Typically, epidermoid tumors are hypointense on T1-weighted and hyperintense on T2-weighted images. Epidermoids typically exhibit diffusion restriction on diffusion-weighted images, in contradistinction to arachnoid cysts that have an apparent diffusion coefficient similar to stationary water.
Surgical excision is the mainstay of treatment and is of low risk due to the avascular nature of the tumor. However, excision of these lesions, which appears to be easy, occasionally carries high chances of damage to nerves and vessels. If the tumor capsule is adherent to neurovascular structures, it is preferable to leave a small tag of cyst lining rather than damaging vascular and neural structures, such as the anterior cerebral artery or its branches in this region. The interhemispheric location of the lesion, bridging veins, proximity to the anterior cerebral arteries, and motor cortex make their excision challenging. Bridging veins are of utmost importance as damage may lead to severe cerebral edema and infarct.
In conclusion, interhemispheric epidermoids are rare tumors. Surgical resection is the mainstay of treatment; however, the extent of resection may be dictated by the adherence of the tumor capsule to surrounding vital structures.
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Conflicts of interest
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]