Arteriovenous malformation: a rare cause of trigeminal neuralgia identified by magnetic resonance imaging with constructive interference in steady state sequences

Abstract

A 64-year-old female presented with a 4-year history of right-sided facial pain. She described an ‘electric shock-type’ pain starting on the right side of her chin that radiated along the lower lip, upper lip and into the lower cheek, in the mandibular division of the trigeminal nerve. The pain was triggered by speaking, eating, drinking, brushing her teeth or touching her chin. These attacks occurred daily and lasted for 3 months before resolving spontaneously, consistent with classical trigeminal neuralgia (TN). Systemic and neurological examinations were normal. In particular, trigeminal sensation was intact bilaterally and trigeminal reflexes were normal. A diagnosis of right-sided, mandibular division TN was made. She had four similar episodes of pain over the following 4 years, each lasting ∼3 months, with each episode becoming more severe. She did not want any analgesic medication for the first two episodes. However, during the most recent episode, carbamazepine (300 mg twice a day) and, subsequently, adjunctive amitriptyline (10 mg at night) were prescribed, although these failed to control the symptoms. Therefore the patient underwent investigation to assess for a structural cause amenable to neurosurgical intervention. The patient underwent a cranial MRI with constructive interference in steady state (CISS) sequences, which demonstrated several small blood vessels surrounding the right trigeminal nerve and a very large mass, thought likely to be a venous aneurysm, lying just behind the root entry zone into the trigeminal nerve (Figure 1). A contrast-enhanced computed tomography angiogram (CTA) confirmed the previous MRI findings and was highly suggestive of an underlying arteriovenous malformation (AVM) (Figure 2). For the pre-surgical work-up a digital subtraction angiogram was organized. This demonstrated a definite AVM during contrast injection in the right vertebral artery with rapid filling of the straight sinus during the early arterial phase (Figure …