Spinal subdural hygroma has been associated with intracranial hypotension or as a complication of spinal surgery ^{1) 2)}.

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 ³⁾.

Spontaneous resolution of idiopathic lumbar subdural hygroma ⁴⁾.

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 ⁵⁾.