C1 arch regeneration, tight cisterna magna, and cervical syringomyelia following foramen magnum surgery.

BACKGROUND: Although bone regrowth following craniocervical decompression has been rarely reported to cause late recurrence of Chiari symptoms, syringomyelia has not been observed in such cases. We report a unique case of cervical syringomyelia resulting from spontaneous regeneration of the posterior C1 arch after foramen magnum decompression. CASE DESCRIPTION: A 38-year-old male patient underwent resection of a symptomatic foramen magnum meningioma. Three years later, he developed neuropathic pain in his left upper extremity with worsening dysphagia and dysphonia. MRI revealed regeneration of the posterior arch of C1 with tight tonsillar impaction of the foramen magnum and extensive cervical syringomyelia. Surgical exploration was undertaken. Neo-ossification of the posterior arch of C1 and thick arachnoid adhesions were found to obstruct cerebrospinal fluid flow through the foramen of Magendie. Foramen magnum decompression, arachnoid dissection, and duraplasty were thus performed and cerebrospinal fluid flow was reestablished through the foramen of Magendie. Postoperatively, patient's symptoms improved dramatically and repeat MRI showed complete resolution of the syrinx cavity.
CONCLUSION: Spontaneous bone regrowth and arachnoid scarring may lead to the development of cervical syringomyelia several years after foramen magnum surgery. Neurosurgeons should be aware of this rare complication whose management is similar to that of Chiari malformations, namely craniocervical decompression and establishment of a patent foramen of Magendie.