Syringomyelia associated with arachnoid septum at the craniovertebral junction, contradicting the currently prevailing theory of syringomyelia formation

Syrinx to Subarachnoid Shunting for Syringomyelia

OBJECTIVE

Surgery for syringomyelia generally aims to treat the underlying cause, if it is known. Optimal management is unclear for idiopathic syringomyelia, or when treatment of the putative cause has failed or is high risk. Syrinx to subarachnoid shunting is an option for these cases; a series is reported to assess the outcomes of this approach.

METHODS

We retrospectively analyzed the clinical and radiologic features of a consecutive series of patients with syringomyelia treated with syrinx to subarachnoid shunting.

RESULTS

Forty-one patients (19 male, 4-79 years old) were treated from 2000 to 2016, including 15 patients with idiopathic syringomyelia, 13 with spinal trauma, 5 with Chiari malformation, 4 with arachnoiditis, 3 with tethered cord, and 1 with arachnoid bands. The patients were treated with a syrinx to subarachnoid shunt, and a subset also underwent expansile duraplasty. At follow-up (3-108 months, mean 36 months) syrinx size was reduced in 37 patients, and there was improvement or stabilization of symptoms in all but 1 patient. Three patients had temporary lower limb sensory symptoms after surgery. Other complications were 2 transient cerebrospinal fluid leaks, a pseudomeningocoele, and 1 postoperative myocardial infarction. Two cases of shunt dislodgement required reoperation, and a third case required early reoperation for an enlarging syrinx. There were no cases of shunt blockage or infection.

CONCLUSIONS

Syrinx to subarachnoid shunting is a safe and effective treatment for idiopathic syringomyelia and for patients who are not suitable for, or have not responded to, other treatment.

Treatment of Syringomyelia in Patients with Arachnoiditis at the Craniocervical Junction

OBJECTIVE

Craniocervical junction arachnoiditis (CCJA) is an uncommon cause of syringomyelia. The pathophysiology of syrinx formation is uncertain, and the appropriate management unclear. A series of cases is reported to demonstrate variations in etiology, uniformity of functional cerebrospinal fluid obstruction at the foramen magnum, and results of surgical intervention.

METHODS

We retrospectively analyzed the clinical and radiologic features of a consecutive series of patients treated for syringomyelia related to CCJA.

RESULTS

Eight patients (5 male, 28-66 years old) were treated from 2000 to 2016. Magnetic resonance imaging demonstrated cervicothoracic syringomyelia in all cases, with the rostral extension of the syrinx suggesting communication with the fourth ventricle in all but one case. There was reduction of foramen magnum cerebrospinal fluid space in all cases, cerebellar ectopia in 5 cases, and fourth ventricular entrapment in 3 cases. Treatment consisted of posterior fossa decompression with either a GoreTex or pericranial patch graft. Six patients had a fourth-ventricle spinal subarachnoid shunt. Two patients had titanium mesh cranioplasty. The immediate postoperative period was associated with reduction in syrinx cavity size and improvement in neurologic symptoms in all cases. At follow-up 10-60 months postoperatively, 3 patients exhibited recurrence of the syrinx and underwent successful reoperation at the craniocervical junction. One patient with persistence of the inferior component of the syrinx was treated with a syrinx-spinal subarachnoid shunt.

CONCLUSIONS

Most syrinx cavities associated with CCJA communicate with the fourth ventricle. Posterior fossa decompression and fourth ventricle to spinal subarachnoid space shunting appears a reasonable treatment for this form of syringomyelia.

Increased flow signal in compressed segments of the spinal cord in patients with cervical spondylotic myelopathy

STUDY DESIGN

Prospective controlled trial.

OBJECTIVE

To describe a newly found increased flow signal in phase-contrast magnetic resonance imaging observed in compressed segments of the spinal cord in patients with cervical spondylotic myelopathy (CSM).

SUMMARY OF BACKGROUND DATA

Derangement of cerebrospinal fluid movement in the spine is a well-known cause of syringomyelia. However, its possible role in CSM has not been studied well, despite the fact that similar derangement takes place in CSM.

METHODS

In a consecutive series of 57 patients with CSM, cardiac-gated phase-contrast magnetic resonance imaging was analyzed. The amplitude of the flow signal obtained in the compressed segment of the spinal cord was compared with that obtained in the lesion-free C2 segment. It was also compared with controls obtained from 10 healthy volunteers. We also studied whether the amplitude was correlated with the severity of cervical canal stenosis, neurological symptoms, indication of surgery, and the presence of intramedullary high-intensity signal on T2-weighted images. In 33 patients who underwent decompression surgical procedures, we compared the amplitude of the flow signal between the preoperative and the postoperative study.

RESULTS

Increased flow signal on phase-contrast study was seen in compressed segments of the spinal cord in 36 (63%) patients. The mean amplitude of the signal in the compressed segment was 0.64 ± 0.06 cm/s, whereas that in the C2 segment was 0.27 ± 0.01 and that in the controls was 0.28 ± 0.01. The flow signal linearly increased as the severity of canal stenosis increased. It significantly correlated with the symptom of upper-extremity dysesthesia, and the indication of surgery in these patients. The mean amplitude of the signal tended to be higher in those with intramedullary high-intensity signal than in those without. After decompression surgery, the increased flow signal was markedly diminished, and returned to a level comparable with the controls.

CONCLUSION

Phase-contrast imaging demonstrated increased flow signal in compressed segments of the spinal cord in a majority of patients with CSM. This suggests a possible role played by derangement of cerebrospinal fluid movement in CSM. It also suggests potential usefulness of phase-contrast study in the management of patients with CSM.

LEVEL OF EVIDENCE

2.

Dorsal spinal arachnoid web diagnosed with the quantitative measurement of cerebrospinal fluid flow on magnetic resonance imaging

An arachnoid web is an abnormal formation of the arachnoid membrane in the spinal subarachnoid space that blocks CSF flow and causes syringomyelia. Although the precise mechanism of syrinx formation is unknown, dissection of the arachnoid web shrinks the syrinx and improves symptoms. Precisely determining the location of the arachnoid web is difficult preoperatively, however, because the fine structure generally cannot be visualized in usual MRI sequences. In this report the authors describe 2 cases of arachnoid web in which the web was preoperatively identified using quantitative CSF flow analysis of MRI. By analyzing cardiac-gated phase-contrast cine-mode MRI in multiple axial planes, the authors precisely localized the obstruction of CSF flow on the dorsal side of the spinal cord in both patients. This technique also revealed a 1-way valve-like function of the arachnoid webs. Imaging led to the early diagnosis of myelopathy related to the derangement of CSF flow and allowed the authors to successfully excise the webs through limited surgical exposure.