Chiari Malformation Associated With Craniosynostosis

Jennifer Strahle, M.D.; Karin M. Muraszko, M.D.; Steven R. Buchman, M.D.; Joseph Kapurch, B.S.; Hugh J. L. Garton, M.D., M.H.Sc.; Cormac O. Maher, M.D.


Neurosurg Focus. 2011;31(3):e2 

In This Article


A total of 383 individual patients underwent surgical craniosynostosis repair over the specified time interval. Of these patients, 183 children were evaluated for isolated sagittal synostosis; 80 for isolated coronal synostosis; 71 for isolated metopic synostosis; 9 for isolated lambdoid synostosis; and 40 for multisuture craniosynostosis. Forty-six patients (12%) were diagnosed with a craniofacial syndrome. Specifically, 16 had Crouzon syndrome, 9 had Pfeiffer syndrome, 9 had Saethre-Chotzen syndrome, 2 had craniofacial dyssynostosis, and 1 had Norman-Roberts syndrome.

Chiari malformation was diagnosed in 29 (8%) of the patients treated for craniosynostosis (Table 2, Fig. 1). Children with single-suture lambdoid synostosis (p < 0.001) or multisuture craniosynostosis (p < 0.001) were much more likely to have associated CM than all other patients with craniosynostosis (Fig. 2). Of the 9 individuals with isolated lambdoid synostosis, 5 (56%) were diagnosed with CM (Figs. 3 and 4) in contrast to no patients (0%) of those 71 with isolated metopic synostosis, 5 (3%) of the 183 with isolated sagittal synostosis, and 5 (6%) of the 80 with isolated coronal synostosis. Of the 40 patients with multisuture synostosis, 5 had pansynostosis defined as premature closure of all sutures (metopic, coronal, sagittal, and lambdoid), and 4 (80%) of these patients were diagnosed with CM. In patients with multisuture synostosis, 14 (35%) of 40 had CM compared with 15 (4%) of the 343 with single-suture involvement (p < 0.001). Including 5 patients with single-suture lambdoid craniosynostosis as well as 12 patients with lambdoid suture involvement in multisuture craniosynostosis, lambdoid synostosis was found in 17 patients (59%) with CM. Multisuture craniosynostosis without lambdoid suture involvement was not significantly more likely to be associated with CM (Table 2) than single-suture disease (p = 0.3). Of the patients with CM, 15 (52%) had associated hydrocephalus. Of the 29 patients with craniosynostosis and CM, 10 (34%) also had syringomyelia and 8 (28%) had associated abnormalities of cerebral venous drainage.

Figure 1.

Schematic treatment diagram for 29 patients with CM and craniosynostosis who underwent surgical repair of craniosynostosis.

Figure 2.

Imaging studies obtained in a 3-year-old boy presenting with scaphocephaly. A: Reconstructed CT scan demonstrating fusion of the sagittal suture, coronal suture, and lambdoid sutures bilaterally, as well as lückenschädel of the skull. Inset: Two-dimensional depiction of the "viewing angle" that is depicted in the larger 3D image. B: Sagittal MR image showing cerebellar tonsillar descent with crowding at foramen magnum. The patient underwent cranial vault expansion and remodeling including frontoorbital advancement. No CM decompression was performed. C: Three years postoperatively, tonsillar descent has improved and there is less crowding at foramen magnum. D: The spinal syrinx has resolved.

Figure 3.

Imaging studies obtained in a 9-month-old boy presenting for evaluation of an abnormal head shape. A: Reconstructed CT scan demonstrating synostosis of the left lambdoid suture. Inset: Two-dimensional depiction of the "viewing angle" that is depicted in the larger 3D image. B: Sagittal MR image showing cerebellar tonsillar descent to 5 mm below the foramen magnum. A posterior CVR with suboccipital craniectomy for CM decompression was performed. The dura was not opened. C: Two-year postoperative MR image revealing improvement in the degree of tonsillar descent and crowding at foramen magnum.

Figure 4.

Imaging studies obtained in a 6-month-old girl presenting for evaluation of severe plagiocephaly. A: Reconstructed CT scan confirming synostosis of the right lambdoid suture. Inset: Two-dimensional depiction of the "viewing angle" that is depicted in the larger 3D image. B: Sagittal MR image demonstrating cerebellar tonsillar descent in a pegged configuration consistent with a diagnosis of CM. The patient underwent posterior cranial vault reshaping including barrel-stave osteotomies and removal of suboccipital bone at the posterior rim of the foramen magnum. The dura was not opened and posterior arch of the first cervical vertebra was not removed. C: Two-year postoperative MR image demonstrating no evidence of a CM.

Each of the 29 patients underwent surgical correction for their craniosynostosis. The mean age at time of craniosynostosis repair was 1.8 years (range 2 months to 9 years). Of the patients who underwent surgical craniosynostosis repair, 17 were diagnosed with CM before undergoing surgical correction for craniosynostosis and 12 were diagnosed with CM following craniosynostosis repair.

Chiari Malformation Diagnosed Prior to Craniosynostosis Repair

Of the 17 patients diagnosed with CM prior to craniosynostosis repair, 10 underwent CM decompression. Five of these children were treated with simultaneous craniosynostosis repair and CM decompression. In each case, calvarial exposure of the posterior fossa was accomplished by reflecting the scalp posteriorly from a single bicoronal incision and performing a suboccipital craniectomy. In each case, the posterior arch of C-1 was never removed and the dura was never opened. In 3 patients, an initial craniosynostosis repair was followed by CM decompression, and in 2 CM decompression was performed prior to craniosynostosis repair. When CM decompression was carried out, either before or after craniosynostosis repair, the CM decompression was performed via a standard midline posterior scalp incision from the inion to the upper cervical spine, and a bony decompression was conducted. The dura mater was never opened. Seven patients diagnosed with CM prior to craniosynostosis repair did not undergo CM decompression at any time during the study period (Table 3). Of these, 6 had a decrease in tonsillar ectopia and 5 had improved CSF flow studies following craniosynostosis repair alone. The 2 patients in this group with syringes prior to craniosynostosis repair both had decreased syrinx width following craniosynostosis repair.

Chiari Malformation Diagnosed After Craniosynostosis Repair

Following craniosynostosis repair, 12 patients were diagnosed with CM. The mean age at time of CM diagnosis was 5.6 years (range 0–16 years) with a mean interval from the initial surgery of 3.7 years (range 197–2780 days). All of these patients underwent both cine MR imaging and spine MR imaging. At the time that CM was diagnosed, cine MR imaging revealed abnormal CSF flow in 10 (83%) of the 12 patients and spine MR imaging demonstrated a syrinx in 7 patients (58%). Five patients (42%) required more than 1 CVR procedure and 7 (58%) had increased ICP found after placement of an invasive ICP monitoring device. Six of these patients (50%) had tonsillar descent over 10 mm and CSF flow studies with restricted anterior and posterior flow at the foramen magnum. These patients ultimately underwent posterior fossa decompression at a mean interval of 3.4 years following the initial craniosynostosis repair.

Of the 12 patients diagnosed with CM following craniosynostosis repair, 5 had at least 1 prior MR imaging study that demonstrated normal tonsillar height, thus indicating de novo CM development. The mean interval between the initial repair and CM diagnosis in these patients was 3.5 years. Four of the patients with documented de novo CM development had a history of hydrocephalus and VP shunt placement in the interim between craniosynostosis repair and CM diagnosis.


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