Man was left blind after spinal surgery

CB is a 40-year-old man who underwent spinal surgery due to a car accident. At first, the surgery was without complications. Several hours later, CB woke up completely blind in both eyes.

CB is a 40-year-old construction worker who was brought to the emergency department after a car accident at work. On admission, he was hemodynamically stable, and due to the circumstances of the accident, a lumbar spine fracture was suspected. This suspicion was confirmed when an X-ray showed a fracture of the second lumbar vertebra. A neurological exam showed that he had diminished motor power in both of his lower limbs, in addition to a complete loss of bladder and bowel sensation. His past medical history was unremarkable since he had no previous neurological problems or problems with vision. He had no comorbidities that could lead to complications during surgery, such as diabetes, hypertension, coronary artery disease, and so on. Due to a fracture shown on the X-ray, he was a candidate for spinal surgery, and an MRI was performed to better visualize possible spinal cord injury.

An MRI showed a significant compression of the spinal cord between the first and second lumbar vertebrae, thus explaining his symptoms.

Soon after the evaluation, the surgery was performed.

In this case, posterior decompression and fusion using pedicle screws in the prone position were done, under general anesthesia. Spine decompression is a procedure performed to relieve pressure on the spinal nerves anywhere along the spine from the neck (cervical) to the lower back (lumbar).

Spinal canal stenosis, disc herniations, fractures, infections, and tumors can narrow the spinal canal and compress the nerves.

Posterior spinal decompression surgery is performed from the back of the spine.

The surgery is performed under general anesthesia, and your surgeon makes an incision on the skin at the back over the involved region of the spine. The muscles overlying the vertebrae are split and moved to the side, exposing the lamina of the vertebra. The lamina is the bone that makes up the backside of the spinal canal and forms a protective roof over the back of the spinal cord. Then the entire bony lamina and ligament are removed (laminectomy). In some cases, only a small opening of the lamina is made by removing bone of the lamina above and below the spinal nerves to relieve compression (laminotomy). Next, to remove the bone spurs and the thickened ligament, the protective sac of the spinal cord and the nerve root are retracted. Then, the facet joints are trimmed to create more space for the nerve roots.

This surgery makes the spine unstable, and therefore, another procedure, spinal fusion, is performed to stabilize the spine. Spinal fusion uses bone grafts, rods, plates, or screws to join together two separate vertebrae in the spine.

During the surgery, the patient was constantly monitored, and both his blood pressure and oxygen saturation were within normal limits.

There were no surgical or anesthetic complications.

After the surgery, CB was still asleep from the anesthesia and seemed to be recovering well. At least, until he woke up. After twelve hours, CB woke up without the ability to see anything.

He was evaluated by various medical specialists such as ophthalmologists, neurologists, and neurosurgeons.

A neurological examination showed that he had preserved papillary and corneal reflexes, meaning his cranial nerves were intact, and his ocular movements were without any disturbance. The ophthalmologist performed tests for intraocular pressure, and they were also without any pathological findings. Since the problem was not his eyes or the nerves surrounding them, maybe it was time to look into the brain. The next diagnostic step was magnetic resonance angiography, which revealed infarcts in the patient's occipital lobe bilaterally.

This means that, somehow, during surgery, there was significant ischemic damage to the patient’s part of the brain that controls vision, leaving him blind forever.

But how could this happen?

Let me explain.

Several types of blindness can occur as a complication of various surgical procedures. More common types of blindness are due to an ischemic process of the optic disc and thrombosis of the retinal artery. Ischemic optic neuropathy is the sudden loss of vision due to an interruption in blood flow to the optic nerve, most commonly caused by inflammation of the arteries that supply blood to the optic nerve. The inflammation commonly occurs in a condition called giant-cell arteritis or temporal arteritis. Retinal artery occlusion refers to the blockage of the retinal artery carrying oxygen to the nerve cells in the retina at the back of the eye. The lack of oxygen delivery to the retina results in severe and permanent loss of vision.

In this case, our patient suffered from a condition known as cortical blindness, meaning the lack of oxygen led to damage to his occipital brain cortex rather than the eye or the optic nerve.

While optic nerve ischemia and retinal artery thrombosis both show changes on the fundoscopic exam, cortical blindness can be confirmed by looking for ischemic changes on intracranial imaging.

The causes of this type of ischemic damage remain unknown, but several interesting theories might explain its pathogenesis.

It is recorded that hypotension, hypoxia, blood loss, and anemia can be significant risk factors for intraoperative ischemic damage. The only caveat was that CB had none of those, and the surgery went completely fine.

In theory, it is impossible to locate the source of a possible thrombus that occluded the vessels of the occipital lobe of the brain. To understand this strange phenomenon, we must take another approach.

Starting with the brain anatomy.

The occipital lobe is one of the four major lobes of the cerebral cortex, and the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex. The occipital lobes sit at the back of the head and are responsible for visual perception, including color, form, and motion.

Damage to the occipital lobe can lead to difficulty with locating objects in the environment, difficulty with identifying colors, production of hallucinations, and, in this case, complete blindness.

Four arteries supply the brain, namely one internal carotid artery and one vertebral artery on each side. Classically the internal carotid arteries on both sides are referred to as the anterior circulation, while the vertebral-basilar arterial system composes the posterior circulation.

At the cranial base, the anterior and posterior circulation connect to form an anastomotic ring called the “Circle of Willis.” The sides of the circle of Willis are made of the anterior cerebral arteries, the posterior cerebral arteries, the anterior communicating branch, which bridges both anterior cerebral arteries, and the posterior communicating arteries, which link the internal carotid artery and posterior cerebral artery on each hemibrain.

The distal part of the posterior cerebral artery extends from the quadrigeminal plate to the calcarine fissure, where it supplies the occipital lobe but also a part of the parietal and temporal lobe. This intricate interconnection allows one of the major arteries to be blocked since the other will easily take over without ischemic repercussions for the brain.

Since there are no risk factors that could explain the production of thrombus and occlusion of the patient's posterior cerebral artery, we must consider another fact: the patient’s position during surgery. 

Procedures in spinal surgery, such as decompression, are often done in a prone position, meaning with the patient lying on his belly, leaving easier access to the spine from the back. Since both the internal carotid and vertebral arteries, which make up the circle of Willis, pass through the patient’s neck, it is entirely possible that inadequate positioning of the neck during surgery can lead to a decrease in blood flow and consequent hypoxia of the brain.

However, the blockage of both the internal carotid artery and vertebral artery inevitably leads to brain death. So, we must consider another fact about the human body- the anatomical variations.

An anatomical variation is a presentation of body structure with morphological features different from those that are typically described in the majority of individuals. Anatomical variations are seen in muscles, bones, joints, and organs, but also in blood vessels, and even in the major ones.

If we look at the circle of Willis once again, we can see that the posterior communicating artery connects the internal carotid artery and posterior cerebral artery, effectively closing up the circle.

If there is a blockage of the vertebral artery, for example, the internal carotid artery simply takes over and continues to supply the branches responsible for the cerebellum and occipital lobes. If there is an anatomical variation in which the posterior communicating artery is not adequately developed, the blockage of the vertebral arteries leads to ischemia of the cerebellum and occipital lobes.

This blockage of vertebral arteries, as some authors suggest, is possible in a prone position during spinal surgery.

The real mystery is how the patient’s cerebellum wasn’t affected by ischemic change, leaving only his occipital lobes irreversibly damaged, and his brain unable to comprehend any kind of vision.

Thanks for watching (reading).