Sunday, October 10, 2004 - 2:36 PM

Squamosal Suture Synostosis: A Rare or Missed Entity Resulting in Atypical Skull Asymmetry

Davinder J. Singh, MD and Scott P. Bartlett, MD.

Introduction: The most common presentation of skull asymmetry is anterior and posterior plagiocephaly, the majority of which result from deformational forces, and the remainder from premature closure of cranial vault sutures. Infrequently, asterion region synostosis has been recognized as manifesting as posterior plagiocephaly and unilateral frontosphenoidal synostosis as anterior plagiocephaly. The majority of patients with skull asymmetry can be diagnosed clinically; however, occasionally, radiographic studies aid in distinguishing between synostotic and non-synostotic pathogenesis. CT scans were obtained for those patients with an atypical skull asymmetry. From these patients, a subgroup was diagnosed with synostosis of the squamosal (parieto-temporal) suture, which has not been described in the literature. The purpose of this paper is to present this subgroup of patients with radiographically diagnosed squamosal synostosis.

Methods: Charts and axial/3D head CT were reviewed for those patients who presented with skull asymmetry and radiographically diagnosed with squamosal synostosis. The following data was obtained: birth history, age and head shape at presentation, torticollis, and treatment. In order to determine if this was a missed radiographic entity, the CT scans of 25 patients diagnosed with posterior positional plagiocephaly, 10 with lambdoid synostosis, and 25 with syndromic craniosynostosis were evaluated for any evidence of squamosal synostosis.

Results: Four patients with radiographically diagnosed squamosal synostosis had heterogeneous skull asymmetries upon presentations. The documentation of the clinical exam, treatment, and CT findings is as follows:

Patient 1: A 5-month-old girl presented with severe left frontal,temporal, and orbital flattening and mid-face hypoplasia. She had left-sided torticollis. Helmut therapy was used for 4 months with no improvement and the patient underwent two fronto-orbital advancements and a posterior vault reshaping. The CT showed a left squamosal synostosis.

Patient 2: A 5-week-old boy presented with severe left front-orbital retrusion and right occipital flattening. He was repositioned for 2 months with no improvement and received helmet therapy until 13 mos with moderate improvement. CT illustrated bilateral squamosal.

Patient 3: A 4-month-old boy presented with moderate right lateral frontal and parietal retrusion as well as left mid and lower face hypoplasia. He had left-sided torticollis. He is being treated with repositioning. CT showed a right squamosal and partial metopic synostosis

Patient 4: An 8-month-old girl presented with moderate to severe bioccipital flattening and biparietal flaring. She was repositioned age 3-8 months and then treated with a helmet from age 8-12 mos with no improvement. CT scan demonstrated bilateral squamosal synostosis.

Review of CTís of 25 patients with unilateral posterior positional plagiocephaly, ten patients with lambdoid synostosis and 25 patients with syndromic craniosynostosis did not demonstrate any evidence of squamosal synostosis.

Conclusions: Squamosal synostosis has not previously been described in the human cranium. It is unclear whether premature fusion of this suture results in skull asymmetry or whether continued deformational forces result in the secondary fusion of the squamosal suture. It appears that squamosal synostosis is a rare entity, which is seen in combination with a skull asymmetry that is not predictable in its pattern. Its functional significance and optimal treatment require further investigation.