Misoprostol for Spinal Stenosis

Overview

This single-group cross-sectional cohort study will enroll approximately 25 patients at the North Texas VA Health Care System (VANTHCS) who have previously received off-label prescriptions of misoprostol for lumbar spinal stenosis for any duration and who are willing to provide verbal and informed consent. Patients will answer a questionnaire regarding pain and functional improvement especially in reference to misoprostol treatment. Patients will also be selected to have their walking tolerance (claudication distance) measured in an outpatient clinic setting to determine the severity of their lumbar spinal stenosis symptoms after having received misoprostol.

Lumbar spinal stenosis (LSS) is clinically described as a neurogenic claudication that is associated with increased mechanical compression on the spinal nerve roots as well as potential compromise of the vascular supply of the spinal nerve roots. This compression typically leads to symptoms of lumbar pseudoclaudication, which include pain, paresthesias, and discomfort in the lower extremities, commonly exacerbated by walking. Broadly speaking, this compression can be the result of a degenerative narrowing of the spinal or nerve root canals. While spinal stenosis is typically considered idiopathic, causes can also include malignancy, injury, and chronic inflammation. It is often debilitating to patients and can lead to a wide variety of negative health outcomes (pre-operative lower levels of function, psychological distress, high self-reported disability scores and operative risks of surgical correction) related to attempted surgical correction of lumbar spinal stenosis. Spinal stenosis continues to be a leading indication for spine surgery in adults older than 65 years old. Furthermore, estimated total Medicare costs for surgeries treating lumbar spinal stenosis amounted to over $1.65 billion for 37,598 individual operations. Physiologically, the venous blood flow in the lumbar spinal region is disproportionately affected by pressure gradients generated secondary to normal movement and pathologic constriction. Studies have found that patients diagnosed with lumbar spinal stenosis with intermittent claudication, while walking on a treadmill, experienced larger amounts of vascular congestion which resolved with sitting. This was measured with a myeloscope in the intrathecal space. The current vascular pathologic mechanism of the symptomatic effects of lumbar spinal stenosis is thought to be a consequence of constriction leading to increasing vascular congestion and inflammation. Authors first described the effect of constriction on vascular flow through a post mortem study of a patient with chronic lumbar spinal stenosis at L4-L5. Most significantly, they found that venous supply proximal to constriction in fact showed reduced and collapsed veins with gross congestion proximal to the lesion. Further investigation found that venous congestion led to increased inflammatory markers in nerves with atrophy, Wallerian degeneration, and perineural fibrosis in more severe patients. Most importantly, these pathologic changes were associated with vascular changes in the absence of direct nerve root compression at these sites. This venous congestion is a potential target for therapy. There has been previous work done with medications that are PGE1 analogs such as limaprost and lipo-PGE1. PGE1 analogs hypothetically treat the above lumbar spinal stenosis pathology by improving blood flow to nerve roots through vasodilatory and antiplatelet aggregation effects. However, misoprostol (PGE1 analog) has not been thoroughly evaluated as a possible treatment for symptoms of lumbar spinal stenosis.