Traumatic Basilar Artery Dissection - Causes, Clinical Features, and Management.

Introduction:

The basilar artery is the main artery that carries oxygen-rich blood to the posterior part of the brain, supplying the brain stem, cerebellum, and occipital region. The right and left vertebral arteries fuse to form a basilar artery at the base of the skull, forming the vertebrobasilar system. The basilar artery dissection can occur due to blunt trauma, inadvertent neck manipulation, fibromuscular dysplasia, and other connective tissue disorders, which may end up causing ischemic stroke.

What Is Traumatic Basilar Artery Dissection?

Traumatic basilar artery dissection is a rare medical emergency that refers to a tear in the basilar artery as a result of blunt trauma, which manifests as subarachnoid hemorrhage, brainstem compression, and brain ischemia. Cases with subarachnoid hemorrhage are associated with higher mortality rates.

What Are the Causes Of Basilar Artery Dissection?

• Car accidents.

• Smoking.

• Blunt trauma.

• Cystic medial necrosis (a disease of large blood vessels like the aorta associated with the weakening of the walls of the blood vessels).

• Ehlers-Danlos syndrome (a hereditary disorder affecting blood vessels, joints, and skin, causing hyperelasticity and hypermobility).

• Fibromuscular dysplasia (progressive twisting of the blood vessels).

• High blood pressure.

• Marfan syndrome (a hereditary disorder affecting the connective tissue).

• Osteogenesis imperfecta (a genetic disorder associated with fragile bones).

• Polycystic kidney disease.

• Vasculitis (inflammation of the blood vessels).

What Are the Risk Factors For Basilar Artery Dissection?

The risk factors include:

• Looking upward for longer periods or neck being in a hyper-flexed position.

• Sudden blunt movements of the neck.

• Trauma.

• Deep massaging of neck tissue.

• Blowing one’s nose.

• Certain yoga postures demand hyperflexion of the neck.

• Painting a ceiling which causes hyperflexion of the neck for a longer period.

• Cardiopulmonary resuscitation.

• Sneezing.

• Vomiting.

• Wrestling.

• Heavy weight lifting.

• Neck injury.

What Are the Consequences Of Basilar Artery Dissection?

• Dissection (tearing) of a basilar artery leads to clot formation as the blood flow in a damaged artery is hampered because of the blood being trapped between the intima (inner layer) and the media (middle layer) of the artery wall.

• The clot formed in the arterial wall will cause bulging of the arterial wall, causing further obstruction in the blood flow.

Severe cases of disrupted blood flow to the posterior part of the brain can lead to:

1. Ischemic Stroke: Ischemic stroke occurs when the clot formed in the artery blocks the blood flow to the brain. The clots can also get dislodged from the original site, which may travel in the bloodstream and can attach itself somewhere in different arteries, leading to complications.

2. Hemorrhagic Stroke: Hemorrhagic stroke occurs when all three layers of the basilar artery are affected by dissection, leading to the pooling of the blood in the surrounding region without reaching the brain tissues.

3. Subarachnoid Hemorrhage: This occurs if the dissection happens inside the brain, leading to the spillage of blood in the subarachnoid space.

What Are the Clinical Features Of Traumatic Basilar Artery Dissection?

• Severe headache.

• Tinnitus.

• Vertigo.

• Hypertension.

• Angina.

• Posterior neck and/ or occipital pain.

• Neck dullness.

• Ataxia (coordination imbalance).

• Dizziness.

• Hearing loss.

• Double vision.

• Dysarthria (slurred speech).

What Are the Complications of Traumatic Basilar Artery Dissection?

• Stroke.

• Subarachnoid hemorrhage (bleeding in the space enclosing the brain).

• Rebleeding.

• Hemiparesis (muscle weakness or paralysis of one side of the body).

• Brainstem ischemia ( refers to the loss of blood supply to the base of the brain).

How Is Traumatic Basilar Artery Dissection Diagnosed?

• The traumatic basilar artery is diagnosed based on the clinical findings and radiological imaging studies, which include CT (computed tomography) scan with CT (computed tomography angiography), MRI (magnetic resonance imaging) with MRA (magnetic resonance angiography), and conventional angiography.

• Subarachnoid hemorrhage can be confirmed by performing a CT scan or lumbar tapping.

• Radiologic diagnosis of basilar artery dissection is confirmed by carrying out conventional angiography and CT angiography or MR imaging with MR angiography. The diagnosis is based on the presence of at least two of the following radiographic features:

1. Intramural hematoma (leaking of blood in the innermost layer of the aorta).

2. Intimal flap (a defect in the aorta, a large blood vessel accompanied by a flap-like projection in the wall).

3. Double-lumen sign (air being trapped in the peritoneal cavity).

4. String or pearl-and-string appearance.

5. Basilar artery trunk (focal symmetric or asymmetric) dilation with proximal or distal stenosis.

6. Configurational change of the involved segment.

7. Contrast media stasis in the affected segment of the basilar artery.

• The radiological findings co-relating with the clinical features can give a clue to the diagnosis.

How Is Traumatic Basilar Artery Dissection Treated?

• Ruptured basilar artery dissections can be best managed by reconstructive endovascular treatment with stents with or without coiling and can prevent potential complications.

• Conservative therapy includes administering anticoagulants and controlling blood pressure, which can prevent further progression and recurrent embolism.

• Stent placement is ideal in patients suffering from complications like brain stem ischemia due to hemodynamic insufficiency detected by diffusion MR imaging or in the cases of brain stem compression.

• Endovascular treatment is usually performed under general anesthesia or deep sedation.

• In cases of ruptured basilar artery dissection, generally, antiplatelet premedication is contraindicated. However, after the procedure, the patient can be given a loading dose of Aspirin and Clopidogrel (dual antiplatelet medication).

• Unruptured basilar artery dissection cases can be treated with dual antiplatelet premedication before the procedure.

• Activated coagulation time (ACT) measures the time taken to form the blood clot, which should be maintained at 2 to 2.5 times the baseline value for 24 to 48 hours after the procedure.

• For ruptured basilar artery dissections, ACT is normalized throughout the follow-up period, whereas ACT is maintained the same for about one to three months in case of unruptured basilar artery dissections.

• Stent placement or stent-assisted coiling is done using a balloon-expandable stent or a self-expanding stent in ruptured basilar artery dissections.

• Stent placement using a balloon-expandable vision stent is done in cases of unruptured basilar artery dissection with progressive brain stem ischemia.

Conclusion:

When compared to an unruptured basilar artery dissection, ruptured basilar artery dissection can be a potentially life-threatening emergency in cases of rebleeding. The emergence of stent placements with or without coiling in basilar artery dissection procedures has better outcomes when compared with conservative techniques and can also be indicated in ruptured basilar artery dissection cases to prevent rebleeding. Unruptured basilar artery dissections should always be treated primarily by a conservative approach. Stent placement can be indicated in patients with signs of progressive brain stem ischemia. The unruptured dissection cases do have a better prognosis if managed effectively.