Atlanto-occipital dislocation with traumatic pseudomeningocele formation and post-traumatic syringomyelia.

STUDY
DESIGN: A case report of traumatic atlanto-occipital dislocation complicated by the development of anterior and posterolateral pseudomeningoceles and the late development of syringohydromyelia is presented.
OBJECTIVE: To describe a unique post-traumatic and postsurgical course following atlanto-occipital dislocation. SUMMARY OF BACKGROUND DATA: Syringomyelia is a significant potential long-term complication in patients recovering from traumatic atlanto-occipital dislocation. Cord enlargement and increased T2 signal can be a marker of abnormal cerebrospinal fluid flow dynamics. This "presyrinx state" can be seen before clinical evidence of neurologic compromise. Pseudomeningocele formation after atlanto-occipital dislocation is rare, with only 3 reported cases. To our knowledge, all reported cases describe retropharyngeal pseudomeningoceles, and posterolateral pseudomeningocele as seen in this case has not previously been described.
METHODS: A single case is reported with an emphasis on the imaging findings related to the patient's subsequent neurologic deterioration.
RESULTS: Following a pedestrian-motor vehicle collision, the patient received initial evaluation and treatment at a local foreign medical facility, where his cervical spine was cleared. Several days following stabilizing treatment and surgery, the patient was transferred to a foreign-based United States military medical facility and ultimately to our institution, where magnetic resonance imaging demonstrated occipitocervical dissociation. The patient was taken to the operating room for surgical stabilization. Four months after his index operation, the patient underwent halo removal. Follow-up magnetic resonance imaging revealed thickening of the cervical spinal cord in conjunction with diffuse high cord T2 signal and a small low cervical segment of syringomyelia. The patient was observed with follow-up magnetic resonance imaging obtained after 1 month. At this time, the low cervical syrinx had enlarged slightly, a small thoracic syrinx was observed, and cine imaging of cerebrospinal fluid flow demonstrated obstruction at the level of the foramen magnum. The patient was taken to the operating room fordecompression of the foramen magnum and posterior fossa and duraplasty. One month later, the patient's clinical condition began to deteriorate, and repeat imaging showed continued enlargement of the patient's syrinx and hydrocephalus. He was admitted for an urgent shunt procedure but unfortunately sustained cardiorespiratory arrest while on the ward awaiting surgery.
CONCLUSIONS: Atlanto-occipital dislocation is rarely survivable, and delayed diagnosis can negatively affect long-term clinical outcome. This case illustrates how, despite early signs of improvement, post-traumatic syringomyelia may occur months or even years after spinal trauma and should always be considered in patients who experience late neurologic deterioration after atlanto-occipital dislocation.