Recurrent posterior circulation infarction caused by anomalous occipital bony process in a young patient

Cerebral infarction in young people is rare. Infarction at a young age may have distinct causes such as hypercoagulability, connective tissue disease, cerebral or cervical arterial dissection, or cardiac problems [1]-[3]. Particularly, recurrent cerebral infarction indicates a higher possibility of the presence of unusual underlying causes. Structural anomaly of the cervical spine or craniocervical junction has been reported as one such unusual cause of infarction [4],[5]. We report the case of a young patient with recurrent posterior circulation infarction that may have been associated with an anomalous occipital bony process compressing the vertebral artery.

A 23-year-old man had a history of recurrent cerebral infarction localized to the vascular territory of posterior circulation. He had no conventional vascular risk factors for stroke. Laboratory findings including lipid profile, D-dimer level, and autoimmune antibody tests were unremarkable. In addition, cardioembolism was excluded after a detailed cardiological evaluation including electrocardiography, echocardiography, 24-hr Holter monitoring, and cardiac CT.

In his first stroke, he experienced dizziness of sudden onset (first stroke, July 2008). Brain MRI showed acute infarction in the vascular territory of the right superior cerebellar artery (Figure 1A). He started taking aspirin (100 mg), clopidogrel (75 mg), and atorvastatin (10 mg). Interestingly, a small hook-shaped anomalous occipital bony process from the left occipital base compressing the left vertebral artery was observed (Figure 2). Although we could not exclude the possibility of arterial thromboembolism originating from the compressed left vertebral artery, we preferred medical treatment instead of invasive intervention.

Two months later, he experienced dizziness again (second stroke, September 2008). Brain MRI showed acute infarction in the left cerebellum and paramedian pons with thromboembolus at the distal basilar artery (Figure 1B). Then, cilostazol (200 mg) and warfarin were added to his regimen. One month later, warfarin was withdrawn for the concern of bleeding in long-term anticoagulation. However, triple antiplatelet therapy including aspirin, clopidogrel, and cilostazol was continued.

Nine months later, he experienced left arm weakness (third stroke, June 2009). Brain MRI revealed acute infarction in the right medial thalamus and paravermian cerebellum along with thromboembolus at the distal basilar artery (Figure 1C). Warfarin was added again to triple antiplatelet therapy. He recovered without neurological deficit. Ten months later, warfarin was withdrawn again for the concern of bleeding in long-term anticoagulation. Three years later, he experienced dysarthria and ataxia (fourth stroke, May 2012). Acute infarction was found in the vascular territory of the left posterior inferior cerebellar artery. CT angiography revealed thromboembolus at the distal basilar artery again (Figure 1D).

To examine the causal relation between recurrent arterial thromboembolism and compression of the left vertebral artery, dynamic time-of-flight MR angiography was performed in 3 positions: neutral, right-, or left-sided head rotation. Stenosis of the left vertebral artery was observed in the neutral position and was slightly aggravated when the head was turned to the right side (Figure 3). There was no remarkable finding in the repeated complete stroke work-ups except for stenosis of the left vertebral artery. Therefore, we were convinced about the causal relationship between recurrent arterial thromboembolism and stenosis of the left vertebral artery compressed by the anomalous occipital bony process. Because the third and fourth strokes recurred when anticoagulation therapy was discontinued, we added warfarin again in addition to the triple antiplatelet therapy. However, unfortunately, the fifth stroke presenting right-sided weakness and facial palsy occurred under adequate anticoagulation and triple antiplatelet therapy (fifth stroke, September 2012). Acute left paramedian pontine infarction and irregular thromboembolus at the distal basilar artery were observed (Figure 1E). Emergency intra-arterial suction thrombectomy was performed and the basilar artery was completely recanalized. Conventional cerebral angiography revealed compression of the left vertebral artery even in the neutral position and was slightly aggravated when the head was rotated to the right side. However, there was no definite flow disturbance according to head rotation. Because of the recurrent infarctions under optimal medical treatment including anticoagulation and triple antiplatelet therapy, we decided to perform endovascular occlusion of the left vertebral artery by coiling. He tolerated the internal trapping procedure following balloon occlusion test without any neurological complication (Figure 4). Triple antiplatelet therapy was continued for 5 months and tapered one by one. Currently, there has been no recurrence of stroke for 2 years after permanent occlusion of the left vertebral artery.

Arterial thromboembolism originating from the left vertebral artery compressed by the anomalous occipital bony process is a rare but not to be overlooked cause of posterior circulation infarction. When intractable to medical treatment, endovascular occlusion of the vertebral artery without flow disturbance of the posterior circulation may be a useful option when surgical removal is not feasible.

We obtained written informed consent from the patient for publication of this case report and any accompanying images.