Intraspinal synovial cyst at the craniocervical junction.

A cystic lesion adjacent to the dens with compression of the lower portion of the medulla oblongata was found on MRI in a 75-year-old male patient with a 2-month history of occipital pain and gait disturbance. Clinically, the patient showed mild tetraparesis, signs of spinal ataxia and symmetrical hyperreflexia. Following subtotal removal of the cyst via left-sided suboccipital craniotomy and left-sided hemilaminectomy of C1 the lesion was classified as synovial cyst on histopathological examination. Postoperatively, the quadriparesis almost completely subsided and the patient is currently doing well, 33 months after surgery. Synovial or ganglion cysts adjacent to the atlantoaxial articulation with ventral compression of the cervicomedullar cord represent rare surgical or radiological entities. Atlantoaxial synovial cysts have no typical radiographic appearance or specific neurological symptoms so that they are frequently misdiagnosed as intraspinal- or skull base tumour, rheumatoid lesion or ectatic vertebral artery. Since no ensuing complications or recurrences have been encountered in cases of incompletely removed cysts the less invasive operative approaches should be used to avoid destabilisation and subsequent additional surgical procedures.