Interventional procedure overview of Transvenous embolisation for spontaneous intracranial hypotension caused by a cerebrospinal fluid-venous fistula

The condition, current treatments, unmet need and procedure

A cerebrospinal fluid-venous fistula (CSFVF) is an abnormal connection that develops between the space surrounding the spinal cord and nearby veins. The fistula allows CSF to leak into the veins. The loss of CSF can cause pressure in the brain to drop (spontaneous intracranial hypotension).

SIH can present with a variety of symptoms, including orthostatic headache, which typically worsens upon standing up and gets better when lying down, neck stiffness, nausea, vomiting, vertigo, tinnitus, visual disturbances, dizziness and imbalance. 

Initial management may include bed rest, hydration, and oral or intravenous caffeine. If symptoms persist then non-targeted epidural blood patching may be offered. If this fails, advanced imaging such as digital subtraction myelography or dynamic CT myelography is done to locate the CSF–venous fistula. Once the fistula is located, targeted treatments are considered. These may include CT-guided fibrin glue injections, which are usually done as a day-case procedure under local anaesthesia and may be offered immediately after the scan, or surgical ligation.

Existing treatment options may not always be feasible or suitable. When a fistula is located near an eloquent or functional nerve root, surgery is not always the best option. This is because it can damage nerves and cause muscle weakness in the arms and legs. Existing treatments can also fail, risking recurrence or the development of new CSF–venous fistulas. Transvenous embolisation offers an alternative treatment option. It could be particularly useful when nerve root ligation cannot be done, when people are unfit for or decline surgery, or when there is treatment failure or recurrence after a CT-guided fibrin glue injection. Although the procedure is more invasive than CT-guided fibrin glue injection, it is less invasive than surgery and may reduce hospital length of stay and overall patient risk.

Transvenous embolisation is a minimally invasive endovascular procedure used to stop abnormal venous outflow responsible for SIH. However, to confirm the presence of CSFVF, accurate localisation is first required which is achieved through advanced imaging technique such as DSM, an invasive procedure. The procedure begins with venous access, obtained via the common femoral or internal jugular vein. A guiding catheter is navigated into the superior vena cava and then into the azygous vein or other relevant venous drainage pathway. These alternative pathways can include the hemiazygos vein, ascending lumbar veins or vertebral veins depending on the location of the fistula. A hydrophilic or still wire is often needed for access. Once the catheter has reached the appropriate venous system, a microcatheter is advanced over a fine wire to selectively catheterise the foraminal or paraspinal vein that contains the fistula. Venography is done to confirm the location of the fistula and see the venous drainage pattern. Venography is an imaging technique that uses contrast dye to visualise the veins under X-ray. The fistula is then embolised using a liquid embolic agent. A high-viscosity formulation is injected to create a proximal plug and then a low-viscosity formulation is injected which flows across the fistula or fistulous network.

The procedure does not offer a way to check that the fistula has successfully sealed. So, the success of the procedure is judged by symptom resolution. A post-procedure CT scan may be done to view the distribution of the embolic agent and assess the extent to which the fistula has sealed.