There is paucity of data describing patients with anatomical anomalies that preclude them from undergoing a typical trans-femoral approach. Variations in venous anatomy are common and should be noted when treating venous sinus pathology. Transverse sinus asymmetry, hypoplasia, aplasia and arachnoid granulations have been previously described with left side anomalies being more common than right. Goyal et. al reported 33.1% rate of asymmetry in their patients with unilateral hypoplasia in 26.8% and aplasia in 4.8%. 1.6% demonstrated bilateral hypoplasia. McCormick et. al. reported 79% of their cadaveric cases showed sinus luminal aberration with septations and blind pouches.
Alternate approaches for variant venous anatomy include upper limb venous access, contralateral access and direct transcranial access. Ramos et. al. have described a successful approach utilising the upper limb brachial or basilic vein as an alternative for patients who may have higher groin complications. A contralateral approach has also been demonstrated as a safe substitute for those patients where antegrade stenting is not feasible. However these approaches do not address the cases where patients have anatomically aberrant intracranial venous systems that do not allow for peripheral access. In this case, a contralateral approach via femoral approach was also attempted without success due to a hypoplastic contralateral sinus.
Transcranial access for endovascular procedures have been described, particularly in the case of embolization for dural arteriovenous malformations. However to our knowledge, there has been no documented description of a transcranial sinus access technique to stent an adult patient.
Technical considerations include the precision in placement of the craniotomy, which can be attempted under fluoroscopic guidance or neuro-navigation techniques.[1, 2] This was accomplished via neuro-navigation in our case and allowed for accurate cannulation of the superior sagittal sinus. There is no consensus in the literature regarding size of craniotomy to allow for successful cannulation as larger craniotomies to a single burr hole have been described.[2, 7] It is also pertinent to counsel the patient regarding the increased risk of performing a craniotomy whilst on dual antiplatelet therapy and the theoretical likelihood of increased bleeding.
There are infrastructural limitations, as a hybrid operating theatre with high quality fluoroscopy will be required to safely execute this procedure. Houdart et. al. reported a subdural bleed as a complication of the only case in their series where the endovascular procedure was not performed in an angiography suite. The case can also be performed with a multidisciplinary team consisting of a neurosurgeon and neurointerventionalist where a dual-trained proceduralist is not available.