First described by Bastian in 1867, posttraumatic syringomyelia (PTS) refers to the development and progression of a cyst filled with cerebrospinal fluid (CSF) within the spinal cord. PTS is a relatively infrequent, but potentially devastating, complication following traumatic spinal cord injury (SCI). PTS is characterized clinically by the often insidious progression of pain and loss of sensorimotor function that may manifest many years after traumatic SCI. If left untreated, PTS can result in loss of function, chronic pain, respiratory failure, or death. (See images below.)
The pathophysiology is not understood fully (see Causes). Formation of a cavity within the spinal cord is common after traumatic SCI. Factors related to initial cavity formation include liquefaction of intraparenchymal hematoma, ischemia due to tethering, arterial or venous obstruction, release of intracellular lysosomal enzymes and excitatory amino acids, and mechanical damage from cord compression. Cavity formation alone is not considered PTS.
In PTS, cavity formation is followed by enlargement and extension of the cystic cavity. Rostral or caudal cyst extension may occur due to turbulent CSF flow or a "one-way valve" phenomenon that allows CSF into, but not out of, the cyst cavity. Tethering of the spinal cord, which results in impaired CSF circulation around the traumatized segment of spinal cord, occurs as a sequela of bleeding-induced arachnoiditis, scarring, spinal canal stenosis, or kyphotic deformity.
Syringomyelia can be categorized as “communicating” (dilation of the central canal) and “noncommunicating” (eccentrically located within the substance of the spinal cord). Congenital conditions, such as Chiari malformations, are associated with either communicating or noncommunicating syrinxes. However, PTS is generally considered noncommunicating. 
The "slosh-and-suck" theory proposes that increased epidural venous flow occurring during activities (eg, coughing, sneezing) that produce effects like the Valsalva maneuver results in increased pressure around the spinal cord, which cannot be dissipated because of disruptions in CSF flow. This pressure may force CSF into the cyst, resulting in expansion and extension.
A model developed by Carpenter et al suggests that a cough or sneeze can produce a pressure wave that would, in turn, give rise to a shocklike elastic jump. [2, 3] According to the model, the elastic jump could create a transient high-pressure region in the spinal cord, resulting in fluid accumulation. However, in an analysis of the model, Elliott et al maintained that the effect of an elastic jump would probably be too weak for fluid accumulation to result and that "the polarity of the pressure differential set up by cough-type impulses opposes the tenets of the elastic-jump hypothesis."  The authors conclude that, based on their analysis, cough-based pressure impulses cannot cause syringomyelia.
A study by Krebs et al of 138 patients indicated that complete SCI and patient age over 30 years are risk factors for developing syrinx early (within 5 years of injury). The study also found that in almost 60% of patients with PTS, the cervical spine was involved. 
Approximately 3-4% of persons with traumatic SCI develop clinically symptomatic PTS. A larger percentage of persons have clinically silent syrinx cavities diagnosed by imaging techniques.
Morbidity is associated with weakness, loss of function, and chronic pain. Mortality can occur from involvement of brainstem respiratory centers or surgical complications.
No racial differences are known for development of PTS.
The incidence of PTS is higher in men due to the increased frequency of SCI in males; however, there is no association of manifestations of the condition with the patient's sex.
Development of PTS can occur at any age, and may begin at any time after traumatic SCI. Cases are reported as early as 1 month or as late as 45 years following injury.
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