Endoscopic-assisted Surgery in the Treatment of Isolated Frontosphenoidal Craniosynostosis

Summary:

Isolated frontosphenoidal craniosynostosis is extremely rare, due to which diagnosis can be challenging. All the isolated cases reported have been treated by open surgical technique. We present a unique case report of an infant with an isolated frontosphenoidal synostosis corrected by a novel endoscopic surgical technique. The patient was a 5-month-old boy with worsening abnormal head shape indicating progressive right frontal bossing, left orbital displacement, and right occipital plagiocephaly. Computed tomography scan confirmed the diagnosis of left isolated frontosphenoidal craniosynostosis. Endoscopic-assisted surgical release was done starting with a 2.5-cm incision in the left temple area followed by a 2-cm strip osteotomy to excise the fused frontosphenoidal suture. Custom-made orthotic helmet therapy was started 2-weeks postsurgery, with excellent progress noted in the head shape confirmed by laser scans. The benefits of the endoscopic technique include smaller incision, decreased blood loss and need for blood transfusion, and decreased stay in hospital. This is the first case report showing the application of a novel endoscopic-assisted surgical treatment in an isolated frontosphenoidal craniosynostosis with no complications noted.

Isolated frontosphenoidal craniosynostosis is extremely rare, with only 49 cases reported in the literature.¹ Due to its rarity, diagnosis can be challenging with frequent errors occurring within the diagnosis during the initial examination of these patients.^2,3

An isolated frontosphenoidal craniosynostosis is embryologically, phenotypically, and morphologically distinct from other types of craniosynostoses. The sphenoid bone has two embryological origins: the lateral frontosphenoidal region developed from intramembranous ossification, and the medial frontosphenoidal region formed through endochondral ossification. These embryological parts become two different units morphogenetically.⁴

All the isolated frontosphenoidal craniosynostosis patients reported have been treated by open fronto-orbital technique. There are no published reports on the use of endoscopic technique for the correction. We present a unique case report of an infant with an isolated frontosphenoidal craniosynostosisc corrected by a novel endoscopic surgical technique.

CASE REPORT

The patient was a 5-month-old boy who presented to the clinic with the chief complaint of abnormal head shape. It was progressively worsening with frontal bossing on the right side. There was no associated weakness, issues with feeding and weight gain, or any other past medical history. He was the third child in the family, and there was no family history of craniosynostosis.

On physical examination, the head circumference measured 39 cm (0.2% percentile). There was right frontal bossing, and the nasal root was almost neutral. On the left, the forehead was flat and the orbit was inferiorly displaced. The right ear was placed slightly anteriorly. There was also mild plagiocephaly noted in the right occipital region, and the left temporal region was severely depressed (Fig. 1). There was no obvious Harlequin sign.

Fig. 1.

Five-month-old boy with right frontal bossing, left orbital inferior displacement, and temporal flattening and neutral nasal root.

The differential diagnosis made was either right coronal craniosynostosis or frontosphenoidal craniosynostosis. Computer tomography scan was done, which confirmed the diagnosis of isolated left frontosphenoidal craniosynostosis (Fig. 2), which fit in line with the clinical findings as well. The diagnosis and the two treatment options were explained to the parents; an open surgical treatment involving fronto orbital advancement, or alternatively an endoscopic release of the fused suture and postoperative helmet therapy was offered.

Fig. 2.

Computed tomography scan confirming left frontosphenoidal craniosynostosis.

The open technique is a longer procedure performed at around 12–15 months of age and associated with higher morbidity. In contrast, the endoscopic technique is performed at a much earlier age and has become more popular, given that it is minimally invasive.^5–8 It was explained that the endoscopic procedure carried a small risk of open surgery if the craniosynostosis was not completely corrected.

Surgery Technique

The infant was placed in supine position with a headrest to support the head. After infiltration of local anesthetic containing adrenaline, an incision of 2.5 cm was made in the left temple area, down to the periosteum. The periosteum was then incised and fully elevated to expose the involved sutures and the lateral orbit. At this stage, the coronal suture was seen to be patent, and the left frontosphenoidal craniosynostosis was noted along with fusion of the sphenoidal wing.

A strip of 2 cm was marked on the frontosphenoidal suture and excised all the way down to the lateral orbit. Complete release of the lateral orbit, sphenoid wing, and pterion was obtained. The osteotomy was extended into the orbital roof to ensure complete excision of the fused suture. There were no dural tears noted. The periosteum and soft tissues were resuspended from the superior temporal tissues and muscle. Closure was done in two layers. Dermabond (Ethicon, N.J.) was used as a tissue adhesive. There were no complications during the procedure, duration of surgery was 65 minutes, and the estimated blood loss was 80 ml.

Helmet therapy was started at 2 weeks postsurgery, with a custom-made orthosis. The helmet had an adequate fit with space on the left temple, forehead, and left parietal segment. The patient made excellent progress at 9 months of follow-up with complete orbital and temporal correction noted (Fig. 3). The length of clinical follow-up was 9 months, with serial laser scans taken every 3 months. There was good progress in the head shape while comparing the first and latest laser scans, with significant improvement noted in the Cranial Vault Asymmetry Index from 3.74 to 0.55, and the anterior cranial symmetry ratio improving from 0.92 to 0.99 (Fig. 4).

Fig. 3.

Photograph at postoperative 9 months follow-up, demonstrating complete correction of frontal, orbital, and temporal asymmetry.

Fig. 4.

Comparison of preoperative laser scan (left) with postoperative laser scan (right) after 9 months.

DISCUSSION

The coronal ring consists of three different sutures: frontosphenoidal, frontoparietal, and spheno-ethmoidal.² In some studies, it is also said to include frontoethmoidal and sphenotemporal sutures as well.¹ In craniosynostosis, the frontosphenoidal suture usually fuses with the frontoparietal, but an isolated suture is extremely rare in occurrence.¹

The frontosphenoidal suture starts from the end of the frontoparietal suture, anteriorly and inferiorly in the temporal fossa and continues medially along the anterior cranial fossa. The second part of the frontosphenoidal suture lies in the middle cranial fossa between the greater sphenoid wing and the frontal bone. The normal age of fusion of this suture is 7 years.¹

Isolated frontosphenoidal synostosis is often misdiagnosed as anterior deformational plagiocephaly. This is noted to fail to resolve by when further radiological investigation is done that points to the correct diagnosis.² Unique features in the forehead, temporal, and orbit region are seen in this type of craniosynostosis.⁴ Features such as frontal bone flattening in the ipsilateral region and the characteristic lack of Harlequin deformity in radiology are also seen. This deformity is formed due to forehead retrusion and inferolateral orbit positioning, causing medial elongation of the orbit. Delay in diagnosis could be due to various reasons, firstly because of how rare it is. Other reasons include anatomical location and visualization of suture on the X-ray.² The frontosphenoidal suture is also very similar to unicoronal synostosis in its presentation of anterior plagiocephaly, making it hard to distinguish between the two and form the correct diagnosis. Volumetric analysis using Mimics software has showed that frontosphenoidal synostosis orbits significantly differed from unicoronal orbits by being wider, shorter, and shallower.⁹

There are several benefits associated with the endoscopic technique, including smaller incision and a minimally invasive procedure, decreased blood loss and need for blood transfusion, and decreased time to recovery. This is the first case report depicting the use of an endoscopic approach toward treatment of frontosphenoidal craniosynostosis. The efforts and close cooperation with the cranial orthotist have to be acknowledged during the time of helmet use in the postoperative recovery period. We recommend that orthotists be considered important members of the multidisciplinary team, as shown from experience in previous studies.^5–7 Additionally, as our length of follow-up is relatively short (9 months), we acknowledge that a longer-term follow-up period would be beneficial to fully note and appreciate the final surgical outcome.

ACKNOWLEDGMENTS

No IRB approval was needed for this case report. There was no need of clinical trial registration for this case report.

PATIENT CONSENT

Parents or guardians provided written consent for the use of the patients’ images.