Magnetic Resonance Imaging and Proton Magnetic Resonance Spectroscopy of Intracranial Epidermoid Tumors

Strategies for intraoperative management of the trigeminal nerve and long-term follow-up outcomes in patients with trigeminal neuralgia secondary to an intracranial epidermoid cyst

Background

Epidermoid cysts (ECs) are one of the most common causes of secondary trigeminal neuralgia (TGN). However, most previous studies have primarily focused on whether complete tumor resection was achieved, and few studies have discussed the primary goal of pain relief.

Objective

The present study provides intraoperative strategies for trigeminal nerve (TN) management in patients with TGN secondary to an EC and observed long-term follow-up outcomes.

Methods

A total of 69 patients with TGN secondary to an EC at our hospitals were included (January 2011–June 2021). The same surgical team performed all surgeries using a retrosigmoid approach. After EC removal, different methods for TN management were used, including microvascular decompression (MVD), sharp capsulectomy, nerve combing and embedded cholesterol crystal excision. The epidemiological, clinical, and surgical data were extracted.

Results

The total EC removal rate was 92.8% (64/69). All patients achieved initial pain relief postoperatively, and 12 patients (17.4%) experienced varying degrees of hemifacial hypesthesia, which was relieved within 3–6 months. Three patients (4.3%) reported partial pain recurrence within a median follow-up period of 5.5 (0.5–10.5) years, which was relieved completely after low-dose carbamazepine administration.

Conclusion

The primary goal of surgical tumor removal for patients with TGN secondary to an EC is relief of the main symptom of tormenting pain. The selection of an appropriate strategy for TN, including MVD, sharp capsulectomy, nerve combing or embedded cholesterol crystal excision, should depend on the patient's situation.

Correlation of radiological features of white epidermoid cysts with histopathological findings

Epidermoid cysts are benign congenital extra-axial lesions commonly found in the posterior fossa. These lesions have a characteristic imaging appearance on computed tomography (CT) scan and magnetic resonance imaging (MRI), but occasionally they may exhibit atypical radiological features, showing unusual hyperintensity on T1-weighted images (T1WI). Currently, such atypical appearance is referred to as white epidermoid. We present the imaging features of 5 cases of white epidermoid cyst and discuss the possible underlying etiology of this unusual radiological appearance. We retrospectively searched our electronic radiology database from January 2005 to December 2015 for all intracranial epidermoid cysts, which were confirmed either by typical MRI appearance or histopathological examination. All white epidermoid cases were evaluated with non-enhanced CT scan and multisequential MRI. Histopathological correlation was carried out in four white epidermoid cases. A total of 61 patients with epidermoid cyst were found, of those 5 (8%) were considered white epidermoids. These consisted of 3 females and 2 males, ranging in age between 31–63 years (average age was 51.8 years). Three patients had lesions located in the posterior fossa. The 2 other patients had lesions in the suprasellar region, with extension to the right middle cranial fossa in one. All 5 lesions were hyperdense on CT scan and hyperintense on T1WI. One patient demonstrated evidence of transformation of a classic epidermoid to a white epidermoid after partial resection. Histopathologically, cholesterol clefts were seen in 3 epidermoid cysts, each which also showed microcalcifications, proteinaceous material or melanin. Hemorrhage was demonstrated in one additional lesion. White epidermoid cyst is an unusual intracranial lesion that should be considered when encountered with an extra-axial T1 hyperintense lesion. The cause of this hyperintensity is not clearly understood, but the presence of cholesterol, microcalcifications, proteinaceous content and rarely hemorrhage or melanin may be contributing factors.

Unusual Intraparenchymal Pontomedullary Epidermoid Cyst in a 2-Year-Old Child: A Case Report and Review of the Literature

BACKGROUND

Intrinsic brainstem epidermoid cysts are rare, benign, slow-growing lesions. Their eloquence precludes complete excision; however, subtotal resection often will result in prolonged or sometimes permanent relief of presenting symptoms and signs. We describe an unusual case and review the literature of this pathology in the pediatric population.

CASE DESCRIPTION

We report an intra-axial pontine epidermoid cyst in a 2-year-old girl who presented with developmental delay, multiple cranial nerve palsies, and pneumonia. Magnetic resonance imaging demonstrated an intrinsic pontine lesion with partial restricted diffusion and an enhancing plaque, the latter not typically seen in congenital lesions like epidermoid. However, gross surgical inspection and histopathology confirmed an epidermoid.

CONCLUSIONS

Our case, supported by the literature, shows that brain stem epidermoid cysts may have atypical radiologic characteristics and that near-total resection remains safe and can improve outcome.

A case report of rim enhancing lesion at the orbital apex

We report a case of partial third nerve palsy resulting from a cystic lesion located at the orbital apex. Imaging was suggestive of cystic schwanomma but histopathology of the lesion confirmed epidermoid cyst, which is a rare tumour of the orbit.

Intracranial Intra-arachnoid Diverticula and Cyst-like Abnormalities of the Brain

Primary intracranial cystic or cyst-like lesions include intra-arachnoid, epidermoid, dermoid, and choroid plexus cysts. Differentiation of these cystic lesions can usually be accomplished by imaging studies alone; however, some cysts are similar in appearance and require histopathology for definitive diagnosis. Clinical signs often reflect the location of the cysts within the intracranial cavity rather than the type of cyst. If clinical signs are significant and progressive, surgical removal is warranted and may be successful, although cystic contents could be harmful if allowed to contact surrounding brain parenchyma or meninges.

Epidermoid cyst with unusual magnetic resonance characteristics and spinal extension

Intracranial epidermoid cysts are generally located in the cerebellopontine and parasellar areas and appear hypo-dense on computed tomography and hypo-intense on T1-weighted magnetic resonance imaging. We report a case of an unusual epidermoid cyst of the cerebellopontine angle extending into the upper cervical canal that appeared hyper-dense on computed tomography scanning, hyper-intense on T1-weighted magnetic resonance (MR) images, and hypo-intense on T2-weighted MR images.

Large cerebello-pontine epidermoid tumor in a child

Cerebellopontine angle lesions are more commonly found in adults; however, they are uncommon in children. 13 year female child presented with progressive cerebellar signs and decreased hearing in left ear. Magnetic resonance imaging was suggestive of left cerebello-pontine angle epidermoid tumor that was treated surgically. In this rare case we discuss the imaging findings and review the relevant literature.

Epidermoid cyst with a metabolite pattern mimicking a brain abscess. A magnetic resonance spectroscopy study

BACKGROUND AND PURPOSE

Intracranial epidermal cysts are benign uncommon lesions. Such lesions arise from an inclusion of an ectodermal element during neural tube closure, in which dermal elements become trapped in the suture line, diploe, meninges, or scalp. Reports have extensively demonstrated the typical magnetic resonance (MR) spectra with the presence of large lactate signals with a virtual absence of healthy brain metabolites.

METHODS

A 20-year-old male patient with a parietal lobe brain lesion was studied by magnetic resonance imaging and magnetic resonance spectroscopy in a 1.5-T Philips scanner.

RESULTS

The lesion presented atypical MR spectra with presence of alanine (1.46 ppm), lactate (1.31 ppm), and amino acids such as valine, isoleucine (0.97 ppm), and glicine (3.52 ppm). No evidence of normal parenchyma tissue metabolites (N-acetylaspartate, creatine, and choline) or succinate and acetate signals was observed. This spectral pattern was unexpected being proposed the differential diagnosis of brain abscess versus epidermoid cyst. Finally, surgical total excision biopsy confirmed the diagnosis of epidermal cyst.

CONCLUSIONS

In this report, we describe a case of an epidermal cyst with an unusual metabolic pattern observed by magnetic resonance spectroscopy mimicking a brain abscess.

Imaging of cerebellopontine angle lesions: an update. Part 2: intra-axial lesions, skull base lesions that may invade the CPA region, and non-enhancing extra-axial lesions

Computed tomography (CT) and magnetic resonance (MR) imaging reliably demonstrate typical features of vestibular schwannomas or meningiomas in the vast majority of mass lesions responsible for cerebellopontine angle (CPA) syndrome. However, a large variety of unusual lesions can also be encountered in the CPA. Covering the entire spectrum of lesions potentially found in the CPA, these articles explain the pertinent neuroimaging features that radiologists need to know to make clinically relevant diagnoses in these cases, including data from diffusion- and perfusion-weighted imaging or MR spectroscopy, when available. A diagnostic algorithm based on the lesion's site of origin, shape and margins, density, signal intensity and contrast material uptake is also proposed. Non-enhancing extra-axial CPA masses are cystic (epidermoid cyst, arachnoid cyst, neurenteric cyst) or contain fat (dermoid cyst, lipoma). Tumours can also extend into the CPA by extension from the skull base (paraganglioma, chondromatous tumours, chordoma, cholesterol granuloma, endolymphatic sac tumour). Finally, brain stem or ventricular tumours can present with a significant exophytic component in the CPA that may be difficult to differentiate from an extra-axial lesion (lymphoma, hemangioblastoma, choroid plexus papilloma, ependymoma, glioma, medulloblastoma, dysembryoplastic neuroepithelial tumour).

Invasive Cerebrospinal Fluid Cysts and Cephaloceles of the Petrous Apex

OBJECTIVE

To describe the presentation, diagnostic evaluation, and surgical management of petrous apex cerebrospinal fluid (CSF) cysts and cephaloceles.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Six patients with symptomatic CSF cysts or cephaloceles.

INTERVENTION(S)

All patients underwent operative intervention.

MAIN OUTCOME MEASURE(S)

Presentation, imaging characteristics, operative findings, surgical approach, resolution of symptoms, and complications.

RESULTS

Six patients presented with various neurotologic symptoms including vertigo, otalgia, diplopia, meningitis, hearing loss, and retroorbital headaches. Four lesions were centered within the anterior petrous apex and were classified as a cephalocele originating from Meckel's cave. The remaining two lesions were arachnoid cysts that involved the posterior petrous apex. Cysts and cephaloceles both demonstrated bone erosion on computed tomography and were hyperintense on T2-weighted magnetic resonance imaging and isointense or hypointense on T1-weighted magnetic resonance imaging. A variety of surgical approaches was used to treat these lesions. Preoperative symptoms were improved in five of six cases. One patient developed a postoperative CSF leak that resolved with conservative measures.

CONCLUSION

Petrous apex CSF cysts and cephaloceles may present with a variety of neurotologic symptoms. Imaging often helps narrow the differential diagnosis, but these lesions can still be confused with other erosive skull base lesions such as cholesterol granulomas, epidermoids, or tumors. Optimal treatment of symptomatic posterior petrous apex CSF cysts is marsupialization via a posterior fossa approach (i.e., retrosigmoid or retrolabyrinthine). A middle fossa approach with obliteration of the anterior petrous apex may be used to treat symptomatic CSF cephaloceles arising from Meckel's cave.

Identification of diffuse and focal brain lesions by clinical magnetic resonance spectroscopy

The purpose of this paper is to facilitate the comparison of magnetic resonance (MR) spectra acquired from unknown brain lesions with published spectra in order to help identify unknown lesions in clinical settings. The paper includes lists of references for published MR spectra of various brain diseases, including pyogenic abscesses, encephalitis (herpes simplex, Rasmussen's and subacute sclerosing panencephalitis), neurocysticercosis, tuberculoma, cysts (arachnoid, epidermoid and hydatid), acute disseminated encephalomyelitis (ADEM), adrenoleukodystrophy (ALD), Alexander disease, Canavan's disease, Krabbe disease (globoid cell leukodystrophy), Leigh's disease, megalencephalic leukoencephalopathy with cysts, metachromatic leukodystrophy (MLD), Pelizaeus-Merzbacher disease, Zellweger syndrome, HIV-associated lesions [cryptococcus, lymphoma, toxoplasmosis and progressive multifocal leukoencephalopathy (PML)], hydrocephalus and tuberous sclerosis. Each list includes information on the echo time(s) (TE) of the published spectra, whether a control spectrum is shown, whether the corresponding image and voxel position are shown and the patient ages if known. The references are listed in the approximate order of usefulness, based on spectral quality, number of spectra, range of echo times and whether the voxel positions are shown. Spectra of Zellweger syndrome, cryptococcal infection, toxoplasmosis and lymphoma are included, along with a spectrum showing propanediol (propylene glycol).