Overshunting-Associated Myelopathy (OSAM) in a Patient with Bilateral Jugular Vein Occlusion

Overshunting-associated myelopathy (OSAM) is a very rare complication of ventricular shunt therapy, and only 11 previous cases have been reported in the literature. We report the successful surgical management of a case of OSAM in a patient with bilateral jugular vein occlusion and congenital hydrocephalus.

A 45-year-old patient with shunt-dependent, congenital hydrocephalus presented to our department with an 8-year history of progressive tetraparesis and gait disturbance. The patient was wheelchair-dependent. A new magnetic resonance imaging scan of the head revealed slit ventricle syndrome and dural enhancement due to shunt overdrainage. Magnetic resonance imaging and a computed tomography-phlebography of the cervical spine revealed engorgement of the epidural venous plexus with secondary compression of the spinal cord and myelomalacia. Surgery was performed, during which we implanted a shunt valve. The patient recovered from surgery without any new deficits. The tetraparesis improved during the inpatient hospital stay. Computed tomography-phlebography was performed 5 days after surgery and showed that the epidural venous plexus anterior to the cervical spinal cord had returned to nearly normal size. On follow-up examination 3 months after surgery, the patient's strength had improved, and he was able to walk short distances with assistance and with ankle foot orthosis on the right side.

OSAM has to be considered according to the Monro-Kellie doctrine and is affected by an engorgement of the epidural cervical venous plexus, which can produce cervical myelopathy. Because it can be treated simply by increasing the shunt resistance, surgeons should be aware of the rarely detected overdrainage complication.