Anterior Spinal Artery Infarction at the Cervicomedullary Junction

Abstract

An 81-year-old right handed man presented with bilateral leg weakness. The patient had been previously independent and was medicated with warfarin for atrial flutter. He had longstanding type 2 diabetes, controlled by oral hypoglycemic medication. At presentation, he reported sudden onset left sided weakness with accompanying neck pain at 22h00 the previous evening. Pertinent findings on neurological examination included a left pronator drift and profound left leg weakness with unsustained antigravity strength. Deep tendon reflexes were brisk throughout but absent at the ankles and there was a left extensor plantar response. Cranial nerve and sensory examinations were normal.The following day there was a profound deterioration in the patient's neurological status, with weakness progressing to involve both legs. Cranial nerve examination was normal apart from significant hypophonia of speech. Palatal movements were normal. Tone was reduced in the left arm, left leg and right leg but was normal in the right arm. There was pyramidal weakness of the left arm with 2/5 power and of the legs with 1/5 power on the left and 3/5 on the right. Reflexes were absent at the left ankle, 1+ at the right ankle and 2+ and brisk in the remainder. Strength was normal in the right arm. Extensor plantar reflexes were present bilaterally. Sensory examination revealed a subtle diminution in pinprick sensation at the level of the C2 dermatome and below with normal light touch, vibration and proprioception throughout.Initial magnetic resonance imaging (MRI) of the brain, including diffusion weighted imaging (DWI), and the cervical spine was reported normal, although the vascular abnormalities of the right vertebral artery had been commented upon and are referred to below on subsequent imaging. Laboratory investigations revealed normal blood work and cerebrospinal fluid. Repeat MR imaging of the cervicomedullary junction, 11 days later, revealed a hyperintense lesion on T2 of the medullary pyramids also involving the upper anterior portion of the cervical spinal cord (see Figure 1A,B) with corresponding reduced apparent diffusion coefficient ( Figure 1C,D). Also seen in Figure 1 is a hyperintense signal in the right vertebral artery (Figure 1, arrow) suggesting either slow blood flow or vascular occlusion. Three-Dimensional time of flight MR angiography (MRA) revealed minimal flow within the proximal vertebral artery on the right, followed by a long segment of absent flow distally (Figure 2). There were multifocal areas of stenosis within the fourth segment of the right vertebral artery with a tight area of stenosis in the distal right fourth segment (Figure 2, arrow 1). The left vertebral and basilar artery and the remainder of the posterior circulation are normal. The right posterior inferior cerebellar artery (PICA) was patent ( Figure 2, arrow 2).The unifying diagnosis was infarction of cervicomedullary junction secondary to occlusion of the anterior spinal artery at the origin of the right vertebral artery.Anterior spinal artery syn...