Surgical Ligation of Spinal CSF-Venous Fistulas after Transvenous Embolization in Patients with Spontaneous Intracranial Hypotension

MATERIALS AND METHODS

This study was approved by the Cedars-Sinai Medical Center institutional review board.

Using a registry that has been prospectively maintained since January 2001 at our quaternary referral center for SIH, we identified all patients with SIH who underwent surgical ligation of a CSF-venous fistula following transvenous embolization with Onyx (Covidien). The diagnosis of SIH was based on the criteria of the International Classification of Headache Disorders, third edition,¹³ with minor modifications. These criteria require objective evidence of SIH, consisting of brain MR imaging showing stigmata of SIH (eg, pachymeningeal gadolinium enhancement or brain sagging), spinal imaging showing a CSF leak (ie, the presence of extradural CSF or a CSF-venous fistula), or low CSF opening pressure (ie, <6.0 cm of CSF). The modification consists of also including patients who do not have headaches but whose symptoms are best explained by SIH.

All patients underwent brain MR imaging and MR myelography (heavily T2-weighted MR imaging). Brain MR imaging was scored for the following findings typical of SIH: subdural fluid collections, enhancement of pachymeninges, engorgement of venous structures, pituitary enlargement, and sagging of the brain.¹⁴ Specifics of the MR myelography technique are reported elsewhere.¹⁵ For DSM, the technique as described by Hoxworth et al¹⁶ was used with some minor modifications. Briefly, DSM is performed with the patient under general endotracheal anesthesia with deep paralysis and suspended respiration for maximal detail and temporal resolution. Patients are positioned in the lateral decubitus position in a biplane angiography suite, with tilt table capability. Pillows or foam padding are placed to optimize the cervicothoracic alignment. A fluoroscopically-guided lumbar puncture is performed with a 22-ga needle. An opening pressure is obtained at this time using standard manometry. Then, an accurate needle position is confirmed with an injection of 0.5 mL of iohexol (Omnipaque; GE Healthcare).

Patients are then further positioned on the basis of the area of interest by tilting the table to achieve contrast flow to the cervicothoracic spine. Great care is taken to maximize contrast opacification of the lateral dural sac by adjusting the degree of tilting to a patient-specific spinal curvature and anatomy. Finally, contrast is injected manually, 1 mL per second, with suspended respiration for 40–120 seconds while acquiring biplane subtraction images at 1–2 frames per second. All imaging studies (ie, brain MR imaging, MR myelography, and DSM) were analyzed by a board-certified neuroradiologist and a board-certified neurosurgeon. Any discrepancies were adjudicated by a second board-certified neuroradiologist.

For transvenous embolization, the technique as described by Brinjikji et al^10,12 was used. Briefly, the right common femoral vein was punctured to access the inferior vena cava. A 6F Benchmark guide catheter (Penumbra) was then advanced to the azygous vein with a coaxial technique using an inner 5F Select Berenstein catheter (Boston Scientific) and Terumo guidewire. A double-lumen (Eclipse 2L; MedLine Group) or single-lumen (Scepter XC; MicroVention) balloon microcatheter with a Synchro2 (Stryker) or Hybrid (Balt) microwire was used to access the paraspinal vein at the level of the fistula determined by DSM. The balloon microcatheter was positioned close to the neuroforaminal venous network, and Onyx-18 was injected slowly with the balloon inflated to prevent reflux into the azygous vein.

The surgical technique consisted of a hemilaminotomy and foraminotomy, exposing the lateral common thecal sac and exiting the nerve root sleeve. A titanium Yasargil aneurysm clip (B Braun) was then placed over the fistulous connection, or the fistula was coagulated with bipolar electrocautery if the fistula could be visualized, or a titanium aneurysm clip was placed over the nerve root sleeve without dividing the underlying nerve root. The operation did not require any modification from that used for CSF-venous fistulas not previously treated with endovascular embolization.

All patients (or their family/caregivers) completed a modified Migraine Disability Assessment score questionnaire to assess the severity of the symptoms before and after the last treatment.¹⁷ The modification consists of substituting “symptoms of SIH” for “headaches.” We refer to this modified questionnaire as the SIH Disability Assessment Score (SIHDAS) questionnaire. A score of 0–5 (grade I) is considered to equate to little or no disability, 6–10 (grade II) is mild disability, 11–20 (grade III) is moderate disability, and >20 (grade IV) is severe disability.