Distraction osteogenesis in two cases of unilambdoid synostosis

Abstract Unilateral lambdoid synostosis (ULS) is a rare suture anomaly and its diagnosis and treatment remain controversial. We investigated how to improve their function and morphology through the review of two cases of ULS with improved function and morphology by the same unreported operative procedure. Moreover, we discussed the diagnosis and treatment of ULS. Case 1 involved a 15-month-old female, brought for consultation because of suspected right ULS. She was diagnosed with right lambdoid and squamous synostoses and approximately 15 mm descent of the cerebellar tonsil. Thus, we performed foramen magnum decompression, first cervical vertebra laminectomy, and skull lengthening. Case 2 involved an 18-month-old female. She also consulted for suspected right ULS. Computed tomography revealed right ULS and squamous synostosis and magnetic resonance imaging showed approximately 9 mm descent of the cerebellar tonsil. We performed foramen magnum decompression and skull lengthening. Both procedures included decompression of the foramen magnum. We enforced osteotomy of the affected side of the lambdoid suture by crossing the superior sagittal sinus and added horizontal osteotomy from the superior right squamous suture to the coronal suture. Three extension devices were placed, two and one in the lambdoid and squamous sutures, respectively. After skull extension and descent of the cerebellar tonsil, exertion of the left frontal bone was improved. In cases of ULS, the squamous suture fusion and the drooping of the cerebellar tonsils can be complicated. Extending the lambdoid suture upward and downward and decompressing the posterior cranial fossa may improve the morphological and functional prognoses.