Epidermoid Cyst of the Brainstem in 3-Year-Old Child: A Rare Case Report

Abstract

Epidermoid cysts are infrequent lesions occupying the intracranial space, comprising approximately 1–2% of all intracranial tumors. Brainstem epidermoids are exceptionally uncommon in children; up until now, only a few scattered case reports have been documented in the literature regarding this unique location. These cysts commonly arise from the inclusion of ectodermal elements during neural tube closure. Complete excision of these cysts is challenging due to their close proximity and adherence to the brainstem, which makes it difficult to achieve. As a result, recurrence of the cysts is not uncommon. We have reported a rare case of a 3-year-old with a 5-month history of progressive headache, imbalance while walking and progressive weakness in his right upper limb and lower limb along with difficulty in swallowing. On MRI Brain imaging study he had a pre-pontine epidermoid with intra-axial extension in the pons. The patient underwent retro-sigmoid/suboccipital craniotomy and microsurgical excision of the tumor, including the tumor capsule. After completing the surgery, the cavity was irrigated using a solution containing hydrocortisone and Ringer lactate to prevent the occurrence of aseptic meningitis. In the postoperative, the patient recovered without any complications, as all symptoms showed immediate improvement, and the lower cranial nerves returned to normal functioning.

Introduction

Epidermoid cysts are infrequent lesions occupying the intracranial space, comprising approximately 1–2% of all intracranial tumors. Their occurrence is even more uncommon in the pediatric age group [1–3]. The cerebellopontine angle and parasellar region are the sites where these cysts are commonly found [4–6], whereas less frequently, they may be situated within the cerebral ventricles and brain parenchyma [7, 8]. Epidermoid cysts in the posterior fossa typically originate in the lateral subarachnoid cisterns [4, 9], with occurrences involving the brainstem being infrequent and uncommon [2, 10–14].

Brainstem epidermoids are exceptionally uncommon in children; up until now, only a few scattered case reports have been documented in the literature regarding this unique location. These cysts commonly arise from the inclusion of ectodermal elements during neural tube closure. These lesions typically present in middle age, manifesting as a result of mass effect and/or hydrocephalus [15]. However, their occurrence in the pediatric age group is rarer but can still happen. The size of these cysts increases due to the accumulation of desquamated cell debris from their capsule. The primary treatment of choice is surgical resection, especially when patients present with neurological symptoms, which is a common occurrence during the initial presentation. However, complete excision of these cysts is challenging due to their close proximity and adherence to the brainstem, which makes it difficult to achieve. As a result, recurrence of the cysts is not uncommon [12]. We hereby present a rare case of 3-year-old male child with pre-pontine epidermoid with intra-axial extension in the pons.

Case Presentation

A 3-year-old boy presented with a 5-month history of insidious onset gradually progressive headache, 2-month history of imbalance while walking and progressive weakness in his right upper limb and lower limb along with difficulty in swallowing for 1 month. He was fully conscious, alert, and oriented. The fundus examination revealed no abnormalities and lower cranial nerve deficit was elicited with altered gag reflex. He had Grade 4 spastic hemiparesis on the right side. Exaggerated deep tendon reflexes were elicited in the right arm and leg. His gait exhibited a typical ataxic pattern. The rest of the neurological examination was unremarkable, showing no abnormalities.

MRI Brain revealed a well-defined extra-axial lobulated lesion in the right para-pontine, pre-pontine, and right para-medullary cistern extending to the right cerebello-pontine angle cistern and extension intra-axially into the pons. The lesion was appearing hyperintense on T2-weighted images and hypointense on T1-weighted images, there was restriction on diffusion-weighted imaging and no contrast enhancement. MR Spectroscopy revealed elevated lipids and myoinositol levels.

A right retromastoid retro-sigmoid/suboccipital craniotomy was performed, and microsurgical excision of the tumor, including the tumor capsule, was carried out. After completing the surgery, the cavity was irrigated using a solution containing hydrocortisone and Ringer lactate to prevent the occurrence of aseptic meningitis. In the postoperative, the patient recovered without any complications, as all symptoms showed immediate improvement, and the lower cranial nerves returned to normal functioning. The histopathological examination of the tumor tissue confirmed the diagnosis of an epidermoid cyst. The postoperative CT scan showed complete excision of the tumor. The patient was discharged on the 10th day after the surgery. During the follow-up at 3 months, he was in good health with no neurological deficits.

Discussion

Epidermoids were acclaimed by the French pathologist Cruveilhier, who referred to them as the “most exquisite tumors among all” due to their captivating pearly characteristics. Despite being congenital in origin, epidermoid cysts typically manifest symptoms only during early adulthood. This occurs as a consequence of the gradual build-up of desquamated cell debris from their capsule, leading to symptomatic presentation.

Epidermoid cysts are characterized as very slow-growing tumors. They are believed to originate from ectodermal remnants that persist during the closure of the neural tube, typically between the third and fifth weeks of embryonic life [5, 16–18]. The majority of epidermoid cysts exhibit a preference for lateral positioning in the extra-axial space. This is attributed to the proliferation of transplanted epithelial cell remnants, which occurs during the migration of otic vesicles or the development of neuro vasculature [9, 19]. On the other hand, a few intrinsic intra-axial epidermoid tumors are located medially, resulting from the separation of neuroectoderm from the cutaneous counterpart. In the present case, the evidence appears to corroborate the hypothesis of the cyst having a primary extra-axial origin, followed by its subsequent invasion and splitting of the brainstem. Tumour appeared to have arisen in the prepontine cistern and to have insinuated itself in the brainstem.

The epidermoid cyst is composed of three main components: an outer capsule, an epithelial layer, and in certain instances, an inner cystic fluid [4, 18]. The enlargement of the tumor is primarily caused by the accumulation of breakdown products from desquamated epithelial cells, resulting in the deposition of keratin and cholesterol in the subarachnoid space. This accumulation gives rise to the characteristic milky-white or pearly appearance of the tumor [9, 18, 20].

The growth of this tumor is believed to be linear and akin to that of the skin [17]. Consequently, if even a single tumor cell remains after resection, a tumor of the same size as the one removed could potentially recur. The recurrence may occur after a time equal to the patient’s age at the time of resection plus 9 months. Thus, if only a small amount of tumor remains after resection, the chances of experiencing a clinically significant recurrence are relatively low [4, 7, 9].

Epidermoid cysts typically produce symptoms by exerting pressure on the adjacent neural structures, and the specific symptoms experienced depend on the location of the cyst. The most frequently observed signs in posterior fossa epidermoids include hemiparesis, lower cranial nerve palsies, and gait ataxia. In addition, aseptic meningitis and increased intracranial pressure can be associated signs with epidermoid cysts. Episodes of aseptic meningitis that recur are typically caused by the spontaneous rupture or leakage of the cyst contents [12, 21–23].

Imaging

On computed tomography (CT) scan, the tumor’s appearance may vary, appearing hypodense, isodense, or occasionally spontaneously hyperdense due to its content of protein, lipid, calcium, and hemosiderin. There may also be occasional calcification, more commonly seen in dermoids. For accurate diagnosis, MRI is the preferred imaging modality. On MRI, the lesion is hypointense on T1-weighted images and hyperintense on T2-weighted images. Moreover, diffusion-weighted imaging (DWI) shows hyperintense restriction and importantly, no contrast enhancement is observed. Epidermoids exhibit hyperintensity on fluid-attenuated inversion recovery images. Occasionally, epidermoids may manifest as a lesion with low intensity on fluid-attenuated inversion recovery sequences, leading to a resemblance to arachnoid cysts. However, this ambiguity is resolved when closely analyzing the diffusion-weighted images, revealing that epidermoids exhibit a distinct brightness unlike arachnoid cysts and other tumors [24].

Treatment

The most effective treatment for symptomatic epidermoid cysts is surgical excision, and the surgical goal should be to achieve total excision whenever possible. However, given the cyst’s adherence to the brainstem, maximal safe resection is advised. Aggressively attempting total resection of the cyst wall presents a surgical challenge and carries higher risks of morbidity and mortality. Surgical decisions must prioritize achieving the maximum possible resection while minimizing postoperative neurological deficits (Fig. 1).

Fig. 1.

A Preoperative MRI of brain T2-weighted image axial section hyperintense lesion in pre-pontine cistern with intra-axial extension in the pons with central hypointensity, B preoperative MRI of brain T1-weighted image axial section hypointense lesion in pre-pontine cistern with intra-axial extension in the pons with central hyperintensity, C preoperative MRI of brain T2-weighted image coronal section hyperintense lesion intra-axial extension in the pons, D preoperative MRI of brain contrast imaging sagittal section showing no contrast enhancement of the lesion, E intra-operative image showing pearly white lesion (epidermoid cyst) on right retrosigmoid approach after cerebellar retraction, F post-operative CT brain image showing excision of the lesion with its intra-axial extension excision

It is essential to exercise caution in order to prevent the leakage of cyst contents into the subarachnoid space to reduce the risk of aseptic meningitis. We use a hydrocortisone solution for irrigation, and as a preventive measure against aseptic meningitis, perioperative systemic steroids are administered.

The primary concern following a conservative resection is the possibility of tumor recurrence. The recurrence rate falls within the range of 1–54% [3, 9, 25, 26]. However, even though tumor regrowth is a predictable outcome of partial/subtotal resections, the duration of symptom-free interval before recurrence can be remarkably lengthy. In the present case, on a 3 year follow up there was no evidence of recurrence.

Conclusion

Epidermoid cysts typically originate within the lateral subarachnoid cisterns when found in the posterior fossa, while occurrences of such cysts in the brainstem area are infrequent. Brainstem epidermoids are exceptionally uncommon, particularly among pediatric patients. The lack of observable clinical symptoms in cases of brainstem epidermoids can be attributed to neural plasticity, which takes place as the tumor infiltrates the brainstem. The authenticity of a genuine intraaxial brainstem epidermoid is uncertain. The management of brainstem epidermoid involves decompressing the cyst contents and removing the nonadherent sections of the cyst capsule. Due to the typically slow and non-aggressive growth of epidermoid tumors, the potential for complications is more significant than the benefits of attempting total resection. The recurrence that takes place after a considerable time gap following partial removal does not provide sufficient reason to justify complete removal, especially if it results in undesirable postoperative neurological deficits. The infrequency of this case and its atypical presentation led us to document and report the case.

Declarations

Conflict of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.