Abstract
In a previous study, intraforaminal anomalies were found to occur at a rate of 7.6%. This increases the risk of injury to
this vessel if the surgeon is unaware of such abnormalities preoperatively. The aim of our retrospective study was to identify
patient factors that may predict anomalous intraforaminal vertebral arteries. Patient records were obtained from a previous
study. In that study, the records of each consecutive patient who underwent cervical spine magnetic resonance imaging (MRI)
for axial neck pain, radiculopathy, or myelopathy between January 2007 and January 2008 were reviewed. The social and medical
histories of each patient were evaluated with respect to the presence or absence of an aberrant vertebral artery. We reviewed
the medical records of the 250 patients whose MRIs were reviewed in the previous study. Seven patients were excluded for incomplete
records. Chi-square and Fisher’s exact tests were performed to compare the normal vertebral artery anatomy patients to the
aberrant patients. The medical records of 19 patients with aberrant vertebral arteries and 224 patients with normal vertebral
arteries were reviewed. The aberrant group was significantly older than the normal group (
P=.00015). The only diagnostic condition that represented a statistically significant difference between the 2 groups was incidence
of cancer. A relationship may exist between patient age, cancer, and medialization of the vertebral artery. The mechanism
of this possible relationship is unclear. Although aberrant vertebral arteries are rare, a surgeon should have raised suspicion
of this possibility in patients with a history of cancer.
Drs Eskander, Aubin, Drew, Marvin, and Connolly, and Mr Major and Ms Huning are from the Department of Orthopedic Surgery,
University of Massachusetts Medical School, Worcester, Massachusetts.
Drs Eskander, Aubin, Drew, Marvin, and Connolly, and Mr Major and Ms Huning have no relevant financial relationships to disclose.
Correspondence should be addressed to: Joshua W. Major, BS, Department of Orthopedic Surgery, University of Massachusetts
Medical School, 55 Lake Ave N, Worcester, MA 01655 (jmajor08@gmail.com).
Injury to the vertebral artery is a rare but potentially devastating complication to cervical spine surgery.
1–5
In a prior study, we examined the magnetic resonance images (MRIs) of 250 patients with cervical spine symptomatology and
found the incidence of patients with an intraforaminal vertebral artery anomaly to be 7.6%.
1
Because of this high rate of anomalies, a case-by-case evaluation of the patient’s vertebral artery anatomy should be done
with each patient assessment. We suspect that the intraforaminal medialization is related to degenerative changes or bony
changes, whereas the other observed anomalies are congenital or traumatic. The purpose of this study was to evaluate patient
factors that may predict anomalous intraforaminal vertebral arteries.
Materials and Methods
In a previous study, we evaluated the cervical spine MRIs of 250 patients taken for the diagnosis of radiculopathy or myelopathy.
1
Magnetic resonance imaging studies of these patients were evaluated and measurements were taken from C2–C7 to determine vertebral
artery anomaly. The 4 measurements obtained were intervertebral artery distance, midline vertebral artery distance, uncovertebral
joint artery distance, and vertebral artery diameter measured on both the right and left sides. All of the MRIs were completed
from the base of the skull through T2.
1
Based on the MRI findings in the previous study, patients were categorized as having normal or anomalous vertebral arteries.
Vertebral artery anomaly was described as the vertebral artery being either medial to or <1.5 mm lateral to the uncovertebral
joint ().
6
As a continuation of that study, the medical records of the 250 patients were evaluated in detail for the patients’ medical
histories. All charts were standardized with regard to determining different variables to be analyzed. Seven patients had
incomplete medical records and were subsequently eliminated from the study. Chi-square and Fisher’s exact tests were performed
to determine any statistically significant differences between the medical histories of those patients with normal vertebral
arteries and the medical histories of those patients with aberrant vertebral arteries. Every medical diagnosis was included
in the study as an individual diagnosis and, when appropriate, as part of an organ system (eg, hepatitis C, cirrhosis, and
steatotic hepatitis were evaluated individually and as a group “liver”) ().
Results
The medical records of 243 patients were reviewed, with 19 patients having aberrant vertebral arteries and 224 patients having
normal vertebral arteries. As stated in the previous study, age represented a statistically significant difference between
the 2 groups.
1
Average patient age in the aberrant group was 55.5 years and in the normal group was 49.5 years (
P=.049). Fifty-eight percent of patients were women, with no statistically significant difference between those patients with
normal and aberrant vertebral arteries (
P=.53). The patient conditions evaluated included social habits and diagnoses of all organ systems (). There was no significant difference between the 2 groups in terms of smoking, alcohol consumption, or drug abuse.
The only diagnostic condition that represented a statistically significant difference between the 2 groups was overall incidence
of cancer. In the normal vertebral artery group, 19 of 224 patients (8.5%) had cancer, while in the aberrant vertebral artery
group, 7 of 19 patients (36.8%) had cancer. Chi-square analysis was applied to these rates, and Fisher’s exact test showed
the 2-tailed
P value to be .0015. This demonstrates a significant difference in the rate of cancer between the 2 groups. Pearson’s correlations
were performed for age, smoking, and cancer in the total of 243 patients and in the separate normal and aberrant groups. Age
did not significantly correlate with cancer (
r=0.89;
P=.169). Also, 6 of 19 patients in the normal group were considered smokers prior to and at the time of their diagnosis of
cancer (lung=1, esophageal=1, breast=2, brain=2). None of the 7 patients in the aberrant group had a recorded smoking history
before or at the time of cancer diagnosis.
Discussion
In this study, patient age, sex, and medical history were reviewed to identify factors that may raise the surgeon’s suspicion
for aberrant vertebral arteries. Despite the vast number of medical conditions evaluated, the only conditions that represented
a significant difference between the 2 groups were age and cancer.
The literature lacks similar studies evaluating patient factors that may predict midline migration of vertebral arteries,
and the literature is divided on various mechanisms for and causes of such variations of normal anatomy. Studies have suggested
that the process may be secondary to cervical trauma.
7,8
However, none of the patients in the studies had any recorded history of significant trauma. Other studies have suggested
that the process may be degenerative.
1,3
It has also been suggested that osteoarthritic changes such as loss of vertebral body height and alignment may lead to tortuosity
of the vertebral artery and erosion of the bone, leading to medialization. The aberrant group was older than the normal group,
making this possibility likely. Despite this fact, the diagnoses of osteoarthritis, rheumatoid arthritis, or osteoporosis
were not significantly related to medialization. However, the condition may exist without documentation in the medical record;
therefore, the retrospective nature of this study limits the reliability of these findings.
The bone pathology theory suggests that pathology of the bone itself may lead to medialization. Infection, tumor, or systemic
disease may lead to erosion of the posterolateral portion of the bone, leading to medialization of the vertebral artery.
3,9,10
The findings of this study make the theory seem plausible, as there was a higher rate of cancer in the aberrant group. This
finding was significant. Also, none of the patients with cancer in the aberrant group were smokers, while 6 of 19 patients
with cancer in the normal group were smokers. This difference in smoking history makes the higher rate of cancer in the aberrant
group even more compelling.
The mechanism of this relationship is unclear. It seems possible that the treatment of these patients may have induced changes
in the bony environment. The patients were all in various stages of diagnosis and treatment, including newly diagnosed, currently
undergoing treatment, and many years after treatment. Therefore, no obvious correlation existed between timing/staging or
treatment and vertebral artery abnormality. Another possible etiology is the catabolic state produced by cancer and its treatment.
Decreased appetite may lead to poor nutrition, which may change bone metabolism. Changes in stress hormones can also alter
the bony environment. The limited number of patients with cancer and the retrospective nature of this study make it difficult
to further evaluate possible mechanisms. Further studies to evaluate this significant finding are needed.
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Patient Conditions
| Social habits |
Smoking, alcohol, drug abuse |
| Cardiac |
Myocardial infarction, chronic heart failure, coronary artery disease, atrial fibrillation, supraventricular tachycardia |
| Hepatic |
Hepatitis C, cirrhosis, hepatic steatosis |
| Pulmonary |
Chronic obstructive pulmonary disease, asthma, sleep apnea |
| Gastrointestinal |
Gastroesophageal reflux disease, irritable bowel syndrome, celiac disease |
| Neurologic |
Multiple sclerosis, migraine, seizure, hydrocephalus, syringomyelia |
| Vascular |
Hypertension, hypotension, anemia, subclavian steal, Arnold-Chiari malformation, cerebral vascular accident, Reynaud’s disease |
| Musculoskeletal |
Osteoporosis, rheumatoid arthritis, osteoarthritis, fibromyalgia, achondroplasia |
| Psychiatric |
Depression, anxiety, bipolar |
| Cancer |
Squamous cell, basal cell, thyroid, renal cell, esophageal, primary brain tumor (oligoastrocytoma, medulloblastoma), leukemia
(acute lymphoblastic, acute promyelocytic, acute myeloid), non-Hodgkin lymphoma, prostate, lung, gastric, breast, ovarian
|
| Other (not included as part of a system) |
Hypercholesterolemia, diabetes, renal failure, human immunodeficiency virus, benign prostatic hypertrophy, glaucoma, Lyme
disease, polycystic ovarian syndrome, hypothyroidism, sarcoidosis, urticaria, glaucoma
|