=====Spinal subdural hygroma=====
Spinal [[subdural hygroma]] has been associated with [[intracranial hypotension]] or as a complication of [[spinal surgery]]
((Schievink WI.Spontaneous spinal cerebrospinal fluid leaks. Cephalalgia 2008;28:1345–56.))
((Luetmer PH, Schwartz KM, Eckel LJ, et al. When should I do dynamic CT myelography? Predicting fast spinal CSF leaks in patients with spontaneous intracranial hypotension. AJNR Am J Neuroradiol 2012;33:690–4.)).


====Case reports====
===2016===
A report describes the circumstances of a patient with a [[cauda equina syndrome]] due to the development of a lumbar subdural CSF collection with ventral displacement of the [[cauda equina]] shortly following [[Posterior fossa decompression for Chiari type 1 deformity]] (CM-I). This unusual, but clinically significant, complication was successfully treated with percutaneous drainage of the extraarachnoid CSF collection. Although there are a few cases of intracranial [[subdural hygroma]] developing after surgery for CM-I, often attributed to a pinhole opening in the arachnoid, as far as the authors can determine, a [[spinal subdural hygroma]] associated with surgery for CM-I has not been recognized
((Darwish HA, Oldfield EH. Lumbar subdural cerebrospinal fluid collection with
acute cauda equina syndrome after posterior fossa decompression for Chiari
malformation Type I: case report. J Neurosurg Spine. 2016 Sep;25(3):328-31. doi: 
10.3171/2016.2.SPINE151480. Epub 2016 Apr 15. PubMed PMID: 27081710.
)).
===2014===
Spontaneous resolution of idiopathic lumbar subdural hygroma
((Yi CK, Biega TJ, Burgos RM. Spontaneous resolution of idiopathic lumbar
subdural hygroma on CT myelography and lumbar spine MRI. BMJ Case Rep. 2014 Aug
22;2014. pii: bcr2014206223. doi: 10.1136/bcr-2014-206223. PubMed PMID: 25150244;
PubMed Central PMCID: PMC4154029.
)).

===2012===
Two cases of symptomatic, post-lumbar surgery cauda equina compression due to formation of a dissecting subdural extra-arachnoid cerebrospinal fluid (CSF) collection (hygroma) under tension. In both cases, a small inadvertent durotomy was sustained during the initial surgery. Surgical re-exploration confirmed a tension subdural extra-arachnoid hygroma due to one-way flow of CSF through a pinhole puncture in the arachnoid. The mechanism and clinico-radiological features of this rare post-operative complication are discussed
((Singleton WG, Ramnarine D, Patel N, Wigfield C. Post-operative spinal subdural
extra-arachnoid hygroma causing cauda equina compression: a report of two cases. 
Br J Neurosurg. 2012 Jun;26(3):429-31. doi: 10.3109/02688697.2011.625063. Epub
2011 Nov 15. PubMed PMID: 22085250.
)).