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NEUROIMAGING |
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| Ahead of print
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Enhancing spinal subdural collection in an operated case of pediatric posterior fossa ependymoma
Foram Bharat Gala1, Neeti Gupta1, Pawan Chawla2, Harshal Agarwal2, Uday Andar2
1 Department of Radiology, Bai Jerbai Wadia Hospital for Children, Mumbai, Maharashtra, India
2 Department of Neurosurgery, Bai Jerbai Wadia Hospital for Children, Mumbai, Maharashtra, India
| Date of Submission | 26-May-2021 |
| Date of Decision | 15-Aug-2021 |
| Date of Acceptance | 13-Oct-2021 |
| Date of Web Publication | 30-Jan-2023 |
Correspondence Address:
Foram Bharat Gala,
Department of Radiology, Bai Jerbai Wadia Hospital for Children, Acharya Donde Marg, Parel, Mumbai 400012, Maharashtra
India
 Source of Support: None, Conflict of Interest: None DOI: 10.4103/jpn.JPN_120_21
 Abstract | | |
Enhancing spinal subdural collections can occur post-operatively in posterior fossa tumors. These are transient, benign, do not cause spinal cord compression, and usually resolve without any intervention or active treatment. These may be misdiagnosed as leptomeningeal metastases which are typically seen in subarachnoid space and not in subdural space. The radiologist must be aware of this entity to avoid misdiagnosis. We report a case of pediatric posterior fossa ependymoma who post-operatively showed enhancing subdural collections in spinal canal.
Keywords: Enhancing spinal subdural collection, pediatric tumours, posterior fossa tumor
| Case Summary | |  |
A 4.5-year-old boy with radiological diagnosis of posterior fossa ependymoma [Figure 1] underwent suboccipital subtotal excision of lesion. On preoperative scan, there was suspicion of leptomeningeal spread of tumor due to enhancement anterior to pons and cervical cord [Figure 1]. Postoperative magnetic resonance imaging (MRI) spine was done on day 18 to evaluate for spinal metastases, which showed large enhancing intraspinal collection located in subdural space extending throughout the spinal canal. There was also new development of pseudomeningocele at the surgical site [Figure 2]. | Figure 1: Preoperative MRI scan: axial (A) and sagittal (B) T2W, axial (C), sagittal brain (D) and sagittal spine (E) postcontrast T1W images show heterogenous solid cystic tumor (arrow) extending into left cerebello-pontine angle and inferiorly into posterior cervical spine obstructing the foramen Magnum (dotted arrow). Suspicious leptomeningeal enhancement was seen in prepontine region and in anterior aspect of cervical cord (elbow arrow)
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 | Figure 2: Postoperative MRI spine: sagittal T2W (A) and postcontrast T1W sagittal (B) and axial (C–E) images superior to inferior, showing pseudomeningocele at surgical site (arrow), linear enhancing structure on sagittal images (B) mimicking leptomeningeal disease, which is actually enhancing subdural collection better seen on axial images. Note the lobulated, festooned appearance of these collections (dotted arrow).
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Postoperative enhancing spinal subdural collections have incidence of around 15.5%–23% after posterior fossa surgery. They appear hypointense on T1-weighted (T1W), hyperintense to cerebrospinal fluid (CSF) on T2-weighted (T2W) images, and show homogenous postcontrast enhancement. On sagittal and axial images, they have lobulated, festooned appearance due to attachments spanning the subdural zones.
Reduction in CSF pressure causes vasodilatation and increased permeability in the dural border cell layer (at interface between dura and arachnoid mater), causing a leak of plasma and contrast resulting in enhancing subdural collection on MRI. Cerebellar tonsillar herniation is frequently associated with postoperative subdural spinal collections. It causes sequestration of intracranial and intraspinal spaces with a resultant increase in intraspinal pressure preoperatively, which is followed by an abrupt reduction in pressure after surgery.[1] In our case, the tumor extended into the cervical spine with obstruction to the foramen magnum.
These collections are transient, benign, do not cause spinal cord compression, and usually resolve without any intervention or active treatment. If radiologist is unaware of this entity, these may be misdiagnosed as leptomeningeal metastases that are typically seen in subarachnoid space and appear as a thin linear enhancement to nodular enhancing lesions that may coat the cord.[2]
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
| References | | |
| 1. | Harreld JH, Mohammed N, Goldsberry G, Li X, Li Y, Boop F, et al. Postoperative intraspinal subdural collections after pediatric posterior fossa tumor resection: incidence, imaging, and clinical features. AJNR Am J Neuroradiol 2015;36:993-9.  |
| 2. | Wong V, Crawford JR. Extensive subdural spinal enhancement mimicking leptomeningeal disease in a young child with posterior fossa tumour following lumbar puncture and surgery. BMJ Case Rep 2014;2014:bcr2014204528. |
[Figure 1], [Figure 2]
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