Background: Endovascular thrombolysis, with or without mechanical clot removal (ET), may be beneficial for a subgroup of patients with cerebral venous sinus thrombosis (CVT), who have a poor prognosis despite treatment with heparin. Published experience with ET is promising, but only based on case series and not on controlled trials.

Objective: The main objective of the TO-ACT trial is to determine if ET improves the functional outcome of patients with a severe form of CVT

Study design: The TO-ACT trial will be designed as a multi-centre, prospective, randomized, open-label, blinded endpoint (PROBE) trial.

Study population: Patients are eligible if they have a radiologically proven CVT, a high probability of poor outcome (defined by presence of one or more of the following risk factors: mental status disorder, coma, intracranial hemorrhagic lesion or thrombosis of the deep cerebral venous system) and the responsible physician is uncertain if ET or standard anti-coagulant treatment is better.

Intervention: Patients will be randomized to receive either ET or standard therapy (therapeutic doses of heparin). ET consists of local application of alteplase or urokinase within the thrombosed sinuses, and/or mechanical thrombectomy. Glasgow coma score, NIH stroke scale and relevant laboratory parameters will be assessed at baseline.

Endpoints: The primary endpoint is the modified Rankin scale (mRS) at 12 months. The most important secondary outcomes are the mRS, mortality and recanalization rate at 6 months. Major intra- and extracranial hemorrhagic complications within one week following the intervention are the principal safety outcome. Results will be analyzed according to the "intention-to-treat" principle. Assessment of study endpoints will be carried out according to standardized questionnaires by a blinded neurologist or research nurse who is not involved in the treatment of the patient.

Study size: To detect a 50% relative reduction in mRS≥2 (from 40 to 20%), 164 patients (82 in each treatment arm) have to be included (two-sided alpha, 80% power).

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Included patients may benefit directly from ET. Complications of ET, most notably intracranial hemorrhages, constitute the most important risk of the study.

Inclusion Criteria:

1. Cerebral venous thrombosis, confirmed by cerebral angiography (with intra-arterial contrast injection), magnetic resonance venography or computed tomographic venography.

2. Severe form of CVT with a high chance of incomplete recovery, as defined by the presence of one or more of the following risk factors

   1. Intracerebral hemorrhagic lesion due to CVT
   2. Mental status disorder
   3. Coma (Glasgow coma scale < 9)
   4. Thrombosis of the deep cerebral venous system

3. Uncertainty by the treating physician if ET or standard heparin therapy is the optimal therapy for the patient.

Exclusion Criteria:

• Age less than 18 years

• Duration from diagnosis to randomization of more than 10 days

• Recurrent CVT

• Any thrombolytic therapy within last 7 days

• Pregnancy (women in the puerperium may be included)

• Isolated cavernous sinus thrombosis

• Isolated intracranial hypertension (without focal neurological signs, with the exception of papilloedema and 6th cranial nerve palsy)

• Cerebellar venous thrombosis with 4th ventricle compression and hydrocephalus, which requires surgery

• Contraindication for anti-coagulant or thrombolytic treatment

  1. documented generalized bleeding disorder
  2. concurrent thrombocytopenia (<100 x 10E9/L)
  3. documented severe hepatic or renal dysfunction, that interferes with normal coagulation
  4. uncontrolled severe hypertension (diastolic > 120 mm Hg)
  5. known recent (< 3 months) gastrointestinal tract hemorrhage (not including he¬morrhage from rectal hemorrhoids)

• Any known associated condition (such as terminal cancer) with a poor short term (1 year) prognosis independent of CVT

• Clinical and radiological signs of impending transtentorial herniation due to large space-occupying lesions (e.g. large cerebral venous infarcts or hemorrhages)

• Recent (< 2 weeks) major surgical procedure (does not include lumbar puncture) or severe cranial trauma

• Known allergy against contrast fluid used during endovascular procedures or the thrombolytic drug used in that particular centre

• Previously legally incompetent prior to CVT

• No informed consent