Myelopathic Symptoms in Surfers May Be Spinal Cord Ischemia

Pauline Anderson

November 28, 2012

A new study describes symptoms of acute myelopathy in surfers.

Back in the late 1990s, Cherylee Chang, MD, medical director, Neuroscience Institute/Neurocritical Care, director, Stroke Center, The Queen's Medical Center, and associate clinical professor of medicine and surgery, University of Hawaii, Honolulu, was curious about a surfer presenting with acute myelopathic symptoms that include urinary retention and progressive paraparesis.

She started researching the literature and collecting data on cases with similar symptoms that imaging showed were not due to a fracture, disc herniation, or inflammation. She's now becoming convinced that these patients have an anatomic abnormality that puts them at increased risk for ischemia of the inferior spinal cord.

Her small case series of patients in Hawaii who presented with this surfers' myelopathy (SM) was published in the November 27 issue of Neurology.

Surfers may want to consider avoiding lying for long periods of time on their board with their back hyperextended, as this may raise the risk for spinal cord ischemia, Dr. Chang advises.

Increasing Weakness

The new study included 19 novice surfers aged 15 to 46 years (14 males), who presented to the hospital between 2002 and 2011. Of these, 5 had complete paraplegia and sensory loss (American Spinal Cord Injury Association Impairment Scale [AIS] A) and 8 had near complete paraplegia (AIS B). None had acute trauma or pre-existing neurologic injury or symptoms.

All but 1 had been lying prone on their surfboard for long periods of time with the lumbar spine hyperextended before noticing lower back discomfort or pain, while some described getting a "pop" or "crack" in their back; most patients said they developed an "achy" lower back pain, said Dr. Chang.

This was followed by increasing weakness and paralysis. "As they emerged from the water and gradually took on more gravity, they noticed that their legs were weakening; by the time they reached their towel on the beach, they couldn't walk," said Dr. Chang.

Imaging tests appeared to rule out cardiogenic or aortic embolic phenomenon, and there was no evidence of ongoing vessel occlusion or hemorrhage to suggest avulsion. As well, arteriosclerotic disease is unlikely to be the cause in such a young population, said the authors.

The imaging findings suggested that the most likely cause was a vascular phenomenon that involves dynamic compression vasospasm or thrombotic infarction of the great anterior radicular artery of Adamkiewicz, which is the main artery feeding the spinal cord, said Dr. Chang.

Pinching Vessel

Although it's speculation at this point, she said, "it seems that somehow patients were pinching or torquing" or otherwise putting stress on that blood vessel, making the cord ischemic. "This is all hypothesis. No patient has died, so we don't have the full pathology, but we suspect it's ischemia to the spinal cord."

She and her coauthors postulate that the compression of the artery occurs during prolonged hyperextension of the lumbar spine.

Experienced surfers tend to sit on their board waiting for a wave and get on their stomach only when they're ready to paddle out to catch it, said Dr. Chang. More inexperienced boarders tend to lie on their stomach with the back extended for longer periods of time.

It's not clear why only a very small number of surfers develop this condition, but Dr. Chang speculates it has something to do with anatomy. The great anterior radicular artery of Adamkiewicz in some people may be a different size and at a level when the back is hyperextend, making it more prone to ischemia, she notes.

Lumbar drainage to decrease intrathecal pressure was performed in 1 patient but had no effect. There was also no significant correlation between mean arterial pressure (MAP) and improvement in the AIS. Although pushing blood pressure up is theorized to enhance neurologic recovery, most patients in this case series already had a pressure of greater than 85 mm Hg, and the 2 patients in the study who had the lowest MAP (70 mm Hg) had the best improvement of 2 or 3 clinical grades over baseline. Higher blood pressure may worsen edema, thereby causing secondary injury, and may not be beneficial, the authors noted.

It's likely that the ischemic injury had already occurred and neither augmentation of blood pressure nor lumbar drainage would be of any benefit after injury, said Dr. Chang.

Although the initial patients tended to receive treatment with methylprednisolone, changes in the literature concerning the risks of this treatment for trauma resulted in "more sporadic" use of this drug, said Dr. Chang. In this small cohort, those patients who did receive this drug didn't see any improvement in symptoms.

"Given that current evidence for acute SCI [spinal cord injury] management suggests harmful side effects are more consistent than any suggestion of clinical benefit, it is not clear that methylprednisolone should be given for SM," the authors write.

Although some patients in this series improved over time, some still can't move their legs or feel anything below the level of their injury.

Dr. Chang concludes that patients presenting with symptoms suggestive of SM should get a detailed history and neurologic examination and an urgent MRI to evaluate for acute spinal cord compression. Computed tomography of the spine is also in order if there is concern about traumatic fracture.

Dr. Chang and the authors have disclosed no relevant financial relationships.

Neurology. Published online November 26, 2012. Abstract