Kimmerli's anomaly
Kimmerli's anomaly, also known as ponticulus posticus, is an anatomical variant involving the ossification of the posterior atlanto-occipital membrane over the groove of the vertebral artery, leading to the formation of an arcuate foramen or ridge (). This anomaly can result in extravasal compression of the vertebral artery, which can sometimes cause cerebrovascular symptoms.
A complete Kimmerli anomaly on the right and an incomplete one on the left.
A complete Kimmerli anomaly on the right.
Incomplete Kimmerli anomaly on the left.
Etiology
The exact cause of Kimmerli's anomaly is not fully understood, but it is believed to result from congenital ossification processes during development. It is a common anatomical variation, with a prevalence in the population ranging from 9% to 37%.
Pathophysiology
The ossified bony ridge can compress the V3 segment of the vertebral artery, especially during head movements such as turning or tilting. This compression may impair blood flow in the vertebrobasilar system, leading to symptoms of vertebrobasilar insufficiency. Over time, chronic compression may cause secondary changes in the artery, such as sclerosis, which contribute to further blood flow disturbances.
Clinical Manifestations
Many individuals with Kimmerli's anomaly remain asymptomatic. However, when symptoms occur, they often include:
- Headache, dizziness, tinnitus, and blurred vision (vertebrobasilar symptoms).
- Pain in the cervical and occipital regions, often aggravated by head movements.
- Symptoms of vertebral artery ischemia such as nausea, vomiting, visual disturbances, loss of balance, and, in severe cases, cerebrovascular accidents (strokes).
- Some patients might experience syncope, sleep disturbances, or reduced work capacity.
Treatment Methods
Management depends on symptom severity:
- Conservative treatment: includes physical therapy, lifestyle modifications, medication to improve blood flow (such as anticoagulants or vasodilators), and wearing a cervical collar to immobilize the neck.
- Surgical intervention: indicated in cases with significant artery compression causing recurrent ischemic symptoms or stroke. Surgically, decompression of the vertebral artery through minimally invasive procedures can be performed to restore adequate blood flow.
In summary, Kimmerli's anomaly is a congenital ossification variant that may cause vertebrobasilar insufficiency through arterial compression, presenting with symptoms such as headaches, dizziness, and ischemic events. Treatment ranges from conservative management to surgical decompression depending on clinical severity.