Devoted to diagnostic and interventional spine imaging and therapeutics

Library

Vertebral Artery Loop Causing Radiculopathy: Important Implications 2008

General Spine

Jonelle Petscavage, MD,
Huey-Jen Lee, MD, ASSR Member
Waseem Bhatti, MD, Non ASSR Member

Excerpta Extraordinaire

Purpose

Vertebral artery loop formation has been described on conventional, CT, or MR angiography. Initial diagnosis by non-contrast MRI of the cervical spine secondary to radiculopathy has not been reported to our knowledge.

Methods & Materials

A 52 year old female with a history of generalized neck pain, presented with 1 year of increasing right sided radiculopathy in the C4-5 and C5-6 nerve root distributions. MRI of the cervical spine from a local hospital reported a left cervical rib contacting the left C8 nerve root and a herniated disc and osteophyte complex at C4-5 on the right resulting in moderate neural foraminal stenosis. The patient was scheduled for an anterior discectomy, plating, and fusion procedure.

Non contrast MRI of the cervical spine was performed at our institution for pre-operative planning. The repeat MRI demonstrated that elongation of the right vertebral artery from a loop entering the right neural foramen at C4-5 with indentation of the thecal sac and deformity of the lateral recess. The right C4-C5 neural foramen was mildly enlarged. There was compression of the right C5 nerve root. CT angiogram of the neck showed looping of the right vertebral artery and bilateral internal carotid arteries. Neurosurgery was consulted and the surgical procedure was cancelled.

Results

Vertebral artery loop formation in the neural foramen or spinal canal is rare, with an incidence of approximately 2.7% in cadaveric specimens. The majority of cases are asymptomatic. Symptomatic patients usually present with radicular pain and palsy in the C3 to C6 range, more commonly on the left side. The underlying mechanism of loop formation is unclear. We postulate that it is most likely due to elongation of the artery.

Radiculopathy is common secondary to disc herniation or osteophyte complex causing foraminal stenosis. Vertebral artery loop may mimic a lateral disc herniation on plain CT of the cervical spine and Flow void vertebral artery on MRI may mimic a calcified disc or osteophyte. However, a tubular hypointense structure and neural foraminal enlargement due to pulsatile arterial pressure are important clues to indicate an arterial loop. Contrast study would also be helpful for confirmation.

Conclusion

Although rare, vertebral artery loop formation can cause cervical radiculopathy. Our case demonstrates that the diagnosis of an arterial loop can be made by the distinguishing imaging feature of an enlarged neural foramina containing a vascular structure.

Images

[gallery]