Orbital venous congestion: rare manifestation of an intracranial arteriovenous malformation.

Intracranial arteriovenous malformations (AVM) are uncommon vascular lesions which typically present with hemorrhage or, in the case of unruptured lesions, with seizure, headache, or focal neurological deficit. The importance of the venous drainage pattern in AVM natural history and treatment outcomes is well documented. It is exceptionally rare for an AVM to drain into the orbital venous system. We present a 42-year-old man with a large, complex AVM of the midbrain, basal ganglia, and thalamus which partially drained into the superior ophthalmic vein. The patient was referred for treatment with radiosurgery. The resolution of orbital venous congestion symptoms accompanied AVM obliteration. An attempt to relieve orbital venous congestion by endovascular obliteration or surgical ligation without successful and complete cure of the AVM will most likely destabilize the nidus and predispose it to rupture. Serial ophthalmologic monitoring by an experienced neuro-ophthalmologist is crucial to monitoring the ophthalmologic effects of AVM progression and treatment.