Abstract

Background: Primary intracranial cholesteatomas are rare, benign lesions of keratinizing squamous epithelium, often arising from middle ear extension. However, their occurrence in the thalamus is exceptionally rare, with only one prior case reported.

Case Description: A 48-year-old male presented with progressive headaches over 3 years and difficulty with upward gaze. Neurological examination revealed bilateral upward gaze palsy. Magnetic resonance imaging demonstrated an intra-axial cystic mass with a solid component in the right thalamus extending to the midbrain, causing obstructive hydrocephalus. A craniotomy with subtotal tumor resection was performed. Histopathology confirmed cholesteatoma. Postoperatively, the patient’s symptoms improved, but hydrocephalus recurred, necessitating an endoscopic third ventriculostomy. Five months later, imaging showed an increase in residual mass size, but further, surgical intervention was declined due to financial constraints. The patient continued outpatient follow-up and maintained functional independence despite persistent symptoms.

Conclusion: Thalamic cholesteatomas are rare and diagnostically challenging. Their deep-seated location complicates surgical resection, often necessitating subtotal removal to preserve neurological function. Close postoperative monitoring is essential due to the high recurrence risk. Further research is needed to optimize diagnostic strategies and explore alternative treatment approaches for these rare lesions.

Keywords: Hydrocephalus, Intracranial cholesteatoma, Neurosurgical management, Surgical resection, Thalamic tumor

INTRODUCTION

Intracranial cholesteatomas are rare, benign lesions characterized by keratinizing squamous epithelium, typically arising from middle ear extension.[ 8 , 17 , 21 ] Primary intracranial cholesteatomas, particularly in the thalamus, are exceptionally rare, with only one previously reported case.[ 21 ] These lesions present diagnostic challenges due to nonspecific clinical and imaging features, often mimicking other cystic tumors. Surgical resection is the primary treatment, aiming for complete removal to minimize recurrence.[ 4 , 21 ] However, deep-seated locations like the thalamus complicate total resection due to proximity to critical structures. Recurrence remains a concern, and no effective nonsurgical treatments currently exist.

We report a case of a 48-year-old male with a primary intracranial cholesteatoma in the thalamus, highlighting diagnostic complexities, surgical management, and clinical outcomes.

CASE PRESENTATION

History

A 48-year-old male patient presented with complaints of headaches that had been ongoing for the past 3 years. The headache symptoms had worsened over the past 2 months, characterized by a sensation of heavy pressure. The patient had attempted to alleviate the pain using over-the-counter analgesics, which provided only temporary relief. In addition, the patient reported difficulty moving both eyes upward. There were no accompanying symptoms such as nausea, vomiting, seizures, muscle weakness, sensory disturbances, blurred vision, hearing loss, or balance issues. The patient had no history of malignancy or family history of similar complaints.

Examination

From the physical examination, the patient’s Visual Analog Scale was recorded at 5/10, and the Karnofsky Performance Scale score was 90/100. No abnormalities were observed on physical examination, including in the ear, nose, and throat region. Both ears appeared normal, with no abnormalities in the tympanic membrane or masses in the ear canals. Neurological examination revealed bilateral upward gaze palsy in both eyes. Magnetic resonance imaging (MRI) of the head demonstrated an intra-axial supratentorial cystic mass with a solid component located in the right thalamus extending to the right midbrain, compressing and narrowing the third ventricle, resulting in noncommunicating hydrocephalus [ Figures 1a - f ]. This finding suggests a primary cerebral tumor, with an initial diagnosis of suspected pilocytic astrocytoma. The patient is planned to undergo craniotomy for tumor removal.

Figure 1:

Brain magnetic resonance imaging showing a well-defined intra-axial cystic mass with a solid component located in the right thalamus extending to the midbrain, measuring approximately 3.9×2.2×4.4 cm. (a-c) shows the hypointense mass with rim contrast enhancement in axial, coronal, and sagittal T1-weighted images, respectively. (d) displays a hyperintense signal on axial T2-weighted imaging. (e) depicts the mass on an axial fluid-attenuated inversion recovery image. (f) shows restricted diffusion in the solid component of the mass on diffusion-weighted images.

Operative procedure

The procedure was carried out with the patient in a park bench position tilted to the right, with the lesion area positioned inferiorly. The head was fixed using a headholder, aligned with the body. A linear incision was made in the parietal region corresponding to the tumor’s location. Following the scalp incision, a craniotomy was performed, extending 4 cm laterally to the right of the midline and spanning a total length of 5 cm. The final cut, made using a craniotome, connected the burr holes along the midline sinus to allow rapid access in case of accidental tearing. Bone drilling was performed with great care to preserve the superior sagittal sinus. After completing the craniotomy, an interhemispheric approach was utilized. The midline structures were accessed while carefully maintaining the integrity of all bridging veins. At the depth between the falx and the parietal lobe, the corpus callosum and both pericallosal arteries were identified. A callosotomy approximately 1.5 cm in length was performed. Upon entering the right thalamus, a pearly white, soft mass was identified [ Figure 2a ]. A subtotal resection was performed, leaving a small portion of the mass around the midbrain area to avoid damaging critical surrounding structures. Tissue samples were taken and sent for histopathological examination. The procedure concluded with the placement of an external ventricular drain (EVD) at the surgical site to provide temporary cerebrospinal fluid (CSF) drainage. The dura mater, bone flap, and scalp were then closed in layers.

Figure 2:

Histopathological findings. (a) Intraoperative view showing a pearly white, soft mass. (b and c) demonstrate the mass lacking epithelial lining and containing keratin material arranged in a lamellar pattern (H&E stain; ×40 and ×100 magnification). (d) shows focal mild lymphoplasmacytic inflammatory cell infiltration (H&E stain; ×200 magnification). H&E: Hematoxylin and eosin

Histopathologic findings

On histopathological examination of the resected tissue, fragments were observed lacking epithelial lining, containing keratin material arranged in a lamellar pattern [ Figures 2b and c]. Scattered among these were focal areas of mild lymphoplasmacytic inflammatory cell infiltration [ Figure 2d ]. No malignant cells were identified in the specimen. Based on the findings, the histopathological characteristics are consistent with cholesteatoma.

Postoperative management

The patient underwent a follow-up head computed tomography (CT) scan 4 days postoperation, which revealed a residual mass and pneumocephalus in the right and left ventricles [ Figures 3a - c ]. The EVD catheter was maintained until day 5, after which a ventriculoperitoneal shunt was placed at the right Kocher’s point. The patient was hospitalized for 8 days, during which their symptoms reportedly improved. The residual mass was regularly monitored. Follow-up examinations by an otorhinolaryngologist showed no abnormalities in either ear. Two months later, the patient presented with complaints of headache. A head CT scan revealed a persistent residual mass accompanied by hydrocephalus, predominantly with dilation of the left lateral ventricle [ Figures 3d - f ]. The patient underwent an endoscopic third ventriculostomy, after which their clinical condition reportedly improved. Five months postoperatively, the patient arrived at the emergency department with worsening headaches over the past week. A head CT scan showed an increase in the size of the residual mass compared to previous imaging, along with dilation of the left lateral ventricle [ Figures 3g - i ]. An MRI and repeat tumor resection were planned; however, the patient and their family declined further intervention due to financial constraints. The patient continued to receive regular follow-up care at the outpatient clinic for the following year. During this period, their headaches reportedly improved, and they were able to resume daily activities independently.

Figure 3:

Follow-up postoperative head computed tomography (CT) scans. (a-c) show residual mass in the surgical bed of the right thalamus and midbrain with pneumocephalus, as seen in axial, coronal, and sagittal views, respectively, on the CT scan performed 4 days postoperatively. (d-f) show residual mass with hydrocephalus, predominantly with dilation of the left lateral ventricle, in axial, coronal, and sagittal views, respectively, on the CT scan conducted 2 months later. (g-i) reveal an increase in the size of the residual mass with dilation of the left lateral ventricle in axial, coronal, and sagittal views, respectively, on the CT scan performed 5 months postoperatively.

DISCUSSION

Cholesteatoma is a benign yet locally aggressive mass resulting from the abnormal accumulation of squamous epithelium in the middle ear.[ 8 , 17 , 21 ] In most cases, this condition is associated with chronic otitis media and arises within the temporal bone.[ 11 , 21 ] Cholesteatomas can also develop in other locations, including the central nervous system. Intracranial cholesteatomas are rare, with only a few reported cases in the literature.[ 1 , 4 , 6 , 11 , 12 , 19 ] Most intracranial cases arise from the extension of the mass from the middle ear into the intracranial cavity, commonly involving areas such as the cerebellopontine angle, temporal lobe, and sellar region.[ 3 , 9 , 15 ] To date, primary cholesteatoma in the thalamus has been reported in only one case, making our report the second of its kind globally.[ 21 ] The exact pathophysiology underlying the primary occurrence of cholesteatoma in this location remains unclear. The rarity of such cases poses significant challenges in diagnosis and management due to nonspecific imaging findings that mimic other lesions.

The thalamus is a complex brain structure essential for sensory processing, motor regulation, and consciousness. Lesions in this region can lead to sensory abnormalities, motor disturbances, and behavioral changes.[ 21 ] Patients with cholesteatoma involving the middle ear often present with symptoms depending on disease severity, such as conductive hearing loss, tympanic membrane perforation, mastoiditis, disequilibrium due to lateral semicircular canal involvement, and otorrhea.[ 10 , 18 ] Severe cases may result in sensorineural hearing loss, headaches, facial nerve paralysis, altered consciousness, nuchal rigidity, intracranial abscesses, or hydrocephalus.[ 11 , 18 ] Intracranial extension can stretch the dura mater in the middle cranial fossa, causing headaches. Thorough otological examination is crucial to detect cholesteatoma growth in the middle ear and assess possible intracranial extension. Key findings include abnormalities in the external auditory canal, otorrhea, or tympanic membrane perforation, with cholesteatoma appearing as a pearly white mass behind the tympanic membrane. Hearing tests, including Weber, Rinne, and audiometry, can confirm abnormalities.[ 11 ] In our case, the patient presented with headache and difficulty moving the eyes, without any abnormalities detected in the ears or hearing function.

Imaging revealed a nonspecific appearance of the cholesteatoma, characterized by hypointense and isointense components relative to gray matter on T1-weighted/fluid-attenuated inversion recovery sequences, hyperintensity on T2-weighted imaging, rim contrast enhancement on postcontrast studies, and restricted diffusion in the solid component on diffusion-weighted imaging (DWI)/apparent diffusion coefficient. These findings suggested a supratentorial intra-axial cystic mass with solid components in the right thalamus extending to the midbrain. The nonspecific imaging findings complicated diagnosis, resembling other cystic lesions such as epidermoid cysts, pilocytic astrocytomas, and other astrocytomas.[ 7 , 14 ] Similarly, Zhang et al. reported mixed signal intensity on T1- and T2-weighted images, restricted diffusion on DWI, and ring enhancement on postcontrast T1-weighted images, which are not specific to thalamic cholesteatomas and can be seen in other lesions.[ 21 ] The pathophysiological basis for the atypical imaging findings is not well understood. One hypothesis is the high vascular supply of the thalamus, which may cause atypical imaging patterns due to disrupted blood flow and diffuse infiltration.[ 21 ] In addition, calcifications at the mass margins and the composition of cholesteatomas, including squamous epithelium and keratin, contribute to inflammatory processes and tissue injury, altering MRI signal intensity.[ 5 , 20 ]

Differential diagnoses for thalamic cholesteatoma include epidermoid cysts, dermoid cysts, arachnoid cysts, gliomas, and metastatic tumors. The presence of calcifications and cystic components on imaging can help differentiate thalamic cholesteatoma from other lesions. However, a definitive diagnosis requires histopathological examination. Histopathological examination of cholesteatomas reveals a scaly, shiny white mass with limited blood supply and encapsulation. Microscopically, keratinizing stratified squamous epithelium and keratin debris without cellular components can be observed, as in our case.[ 4 , 11 , 21 ]

The primary and only treatment for intracranial cholesteatoma is surgical resection, with the goal of achieving total tumor removal to minimize the risk of recurrence. Radiotherapy and chemotherapy had no role in the treatment of cholesteatoma.[ 4 , 21 ] Lesions located in accessible regions, such as the cerebellopontine angle and temporal bone, are often amenable to complete resection. In our case, the tumor’s location in the thalamus rendered total resection unfeasible due to extensive infiltration and involvement of critical structures. Instead, we performed subtotal tumor removal and obtained a biopsy to confirm the diagnosis. A small portion of the tumor was intentionally left to avoid damage to adjacent nerves and vital structures.

In this case, we use the interhemispheric approach because the tumor was located at the thalamus near the third ventricle. The interhemispheric approach was the shortest corridor to an area near the third ventricle. It provides adequate visualization of the area surrounding the third ventricle, and it avoids many of the risks associated with alternate approaches, such as memory loss, mutism, and seizures. The risk of this approach is injury to the sagittal sinus and disconnection syndrome if extensive damage to the corpus callosum is done.[ 16 ] Additionally, cerebrospinal fluid (CSF) diversion procedures were performed to manage hydrocephalus resulting from tumor-related obstruction.

Deep-seated tumors also had complexity in their treatment due to anatomical location. The approach to deep-seated tumors was various. For tumors at the sellar region, a pterional approach or endoscopic transsphenoid endonasal approach could be used. For tumors at the fourth ventricle, the telovelar approach can be used. Intracranial tumors sometimes are unresectable due to eloquent location at adherent to vital structures such as brainstem or major vessels. Stereotactic biopsy can be used to confirm tumor cells and morphology to determine the next alternative management, such as stereotactic radiosurgery, radiotherapy, or chemotherapy.[ 2 ]

The patient demonstrated significant postoperative improvement but continued to experience hydrocephalus and recurrent headaches 2 months later. While most patients achieve favorable outcomes without significant sequelae, particularly following total tumor removal, malignant transformation of cholesteatomas remains exceedingly rare.[ 4 ] However, recurrence rates for cholesteatomas can reach up to 71% in some series.[ 18 ] It is important to note that these figures primarily reflect middle ear cholesteatomas, as specific data for primary intracranial cholesteatomas are unavailable due to their rarity. In cases of recurrence, resection remains the treatment of choice. To date, no effective nonsurgical treatments, including radiotherapy or chemotherapy, have been established for either initial or recurrent cases.[ 13 ]

CONCLUSION

Primary intracranial cholesteatomas, especially those in the thalamus, are rare and challenging to diagnose and manage. In this case, nonspecific symptoms and imaging led to a delayed diagnosis, which was confirmed histopathologically. Surgical resection remains the primary treatment, though subtotal resection was necessary due to the tumor’s location near critical structures. Despite initial improvement, the patient experienced recurrent hydrocephalus and headaches, managed with CSF diversion. Recurrence rates for cholesteatoma are high, particularly in middle ear cases, but specific data for intracranial cases are limited. Further research is needed to enhance diagnosis and treatment strategies for these rare lesions.

Ethical approval:

Institutional Review Board approval is not required.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

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