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|Year : 2021 | Volume
| Issue : 5 | Page : 1275-1276
Diagnostic Conundrum in a Posterior Fossa Lesion
Madhivanan Karthigeyan1, Kavindra Singh1, Pravin Salunke1, Neeraj Sharma2, Apinderpreet Singh1, Kirti Gupta3
1 Department of Neurosurgery, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
2 Department of Radiodiagnosis, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
3 Department of Histopathology, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, India
|Date of Submission||10-Mar-2021|
|Date of Decision||13-Mar-2021|
|Date of Acceptance||13-Jul-2021|
|Date of Web Publication||30-Oct-2021|
Associate Professor, Department of Neurosurgery, PGIMER, Sector 12, Chandigarh - 160 012
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Karthigeyan M, Singh K, Salunke P, Sharma N, Singh A, Gupta K. Diagnostic Conundrum in a Posterior Fossa Lesion. Neurol India 2021;69:1275-6
A 28-year-old man presented with complaints of headache, ataxia, and cerebellar signs for the past 2 weeks. Computed tomography (CT) scan showed a midline, hyperattenuating lesion in the posterior fossa. On magnetic resonance imaging (MRI), the lesion was T1-hyperintense, T2-remarkably hypointense, with no contrast enhancement or diffusion restriction [Figure 1]. Additionally, a small mural nodule (T1-hypo, T2-iso-hyperdense) containing calcific areas was present, and magnetic resonance (MR) spectroscopy showed lipid lactate peak at 1.3 ppm. The differentials considered were dermoid/epidermoid, craniopharyngioma, and pilocytic astrocytoma. The lesion showing dark toffee-like material was totally excised, and histopathology confirmed an epidermoid cyst (EC) [Figure 2].
|Figure 1: Noncontrast CT scan (a) shows a well-defined, intra-axial, hyperattenuating midline cerebellar lesion. On MRI, the lesion is T1 hyperintense (b), T2 markedly hypointense (c), not restricting on diffusion sequence (d) and nonenhancing (e). A mural nodule (arrow) of mixed signal intensity is evident on T2-weighted section (f) and shows faint contrast uptake (g). Sagittal cut (h) shows the lesion and osseous anomalies such as assimilated C1 arch and cervical block vertebrae; tonsillar herniation is also noted|
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|Figure 2: Intraoperative photographs. The lesion was pearly white with firm nodular portion (a) and was filled with highly viscous, toffee-like material (b). This dark-brown content corresponded to hyperattenuation on CT, and T1-hyper/T2 marked hypointensity on MRI. Clear interface with cerebellar tissue after removal of the viscous content (c)|
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Located in suprasellar/cerebellopontine angle, ECs are characteristically extra-axial, CT-hypointense, T1-hypointense, T2-hyperintense, nonenhancing, and typically show restriction on diffusion-weighted-imaging., Approximately 5.6% of ECs show atypical-features. In white epidermoid, a distinct variant, CT shows hyperdense appearance, and the T1/T2 characteristics are reversed. High protein content in combination with high viscous fluid has been cited as the reason. Another possibility for such nonconventional imaging could be a fresh bleed inside the EC cavity. In our case, besides unusual MR signals, there were few other interesting characteristics. The lesion was intra-axial and showed a mural nodule, which is exceptionally rare with EC; focal cyst wall thickening with foreign body granulation tissue secondary to leakage of the cyst contents has been the proposed etiopathogenesis. The lipid MR spectroscopy peak further compounded the imaging dilemma and can be explained by the presence of lipid contents comprising mixed triglycerides. The described imaging pattern in the index case can be shared by atypical dermoid and craniopharyngioma.
We illustrate a rare case of an atypical/white epidermoid that posed diagnostic challenge due to its imaging overlap with other less commonly encountered lesions in the posterior fossa. Such unusual radiologic presentation merits consideration for appropriate treatment planning.
Compliance with Ethical Standards
Informed consent was obtained.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]