Does conventional posterior vault remodeling alter endocranial morphology in patients with true lambdoid synostosis?

True lambdoid synostosis (TLS) produces a consistent morphology that includes occipital flattening, an ipsilateral occipitomastoid prominence, and a mild contralateral hemifacial deficiency that minimally improves with surgery. Prior studies have demonstrated that dysmorphic middle and posterior cranial fossae contribute to the craniofacial scoliosis characteristic of TLS. We hypothesize that these endocranial features remain after surgery, causing the persistent hemifacial deficiency seen in these patients.

Three-dimensional anthropometric measurements were made on preoperative and postoperative CT scans of patients with TLS (n = 5). Quantitative analysis was performed on the middle cranial fossa area (MCF), anterior cranial fossa area (ACF), posterior fossa deflection angle (PFA), petrous ridge angle (PRA), temperomandibular joint (TMJ) angle, and external auditory meatus angle. The results were analyzed using a 2-tailed t test.

Preoperative CT scans were obtained at a mean age of 1.05 years. Patients underwent posterior vault remodeling at a mean age of 1.33 years. Postoperative CT scans were obtained a mean age of 3.14 years. Following surgery, patients with TLS demonstrated an unchanged PFA (P = 0.76) with deviation toward the affected suture. The ACF remained symmetrical (P = 0.212), and the contralateral MCF remained enlarged relative to the ipsilateral side (P = 0.003). The contralateral middle fossa became more retrodisplaced (P = 0.021). The ipsilateral PRA remained unchanged (P = 0.95). Ear position also remained asymmetrical (P = 0.037). The position of the TMJ was not statistically different between sides before (P = 0.24) or after surgery (P = 0.07).

Traditional cranioplasty effectively restores calvarial shape, but does not significantly alter the dysmorphic features seen in the endocranium of patients with TLS.