Tibial Nerve SEP Shows Promise in detection of Lumbar Spinal Stenosis

Lumbar spinal stenosis (LSS) can cause debilitating back pain and nerve-related symptoms, it has been notoriously challenging to diagnose accurately. However, a recent study published in Clinical Neurophysiology Practice found a promising technique that utilizes somatosensory evoked potentials (SEPs) in the tibial nerve, offering new hope for LSS patients.

The retrospectively study focused on patients with MRI-confirmed LSS located at the cauda equina or conus/epiconus region and recorded the P15 and N21 potentials and identified specific abnormalities as diagnostic markers. Localizing abnormalities, including a normal P15 latency with either a prolonged P15-N21 interval or an absent N21, were found in 67% of patients, making this approach significantly more sensitive than traditional diagnostic methods.

Importantly, the newly discovered technique surpassed other diagnostic markers' sensitivities. While delayed P38 latency offered a sensitivity of just 28%, and N21 abnormalities provided 39%, the P15 and N21 potentials combined displayed a higher sensitivity that could potentially revolutionize LSS diagnosis.

Moreover, this method demonstrated its ability to identify LSS even in patients who did not present typical sensory symptoms or signs. The study discovered that localizing abnormalities were present in six out of eleven patients without these hallmark indicators, making it a valuable tool for early diagnosis.

The study also examined tibial nerve F-wave findings, a common diagnostic approach, and found that it was abnormal in 36% of patients. However, the localizing abnormalities in SEPs were detected in a higher percentage of the same patient population, further underlining the potential advantages of this new diagnostic method.

Additionally, the study found that the P15 amplitude was depressed in 22% of patients, which could indicate the involvement of the dorsal root ganglion in LSS, even though its latency remained normal for these individuals.

This innovative diagnostic technique, which uses tibial nerve SEPs with the recording of P15 and N21 potentials, promises a much-needed improvement in LSS diagnosis. It can precisely pinpoint the location of the lesion at the cauda equina or conus/epiconus level, enhancing the ability to target treatments effectively.

Reference:

Matsukura, K., Hokkoku, K., Mukai, T., Oishi, C., Kanbayashi, T., Takahashi, T., & Sonoo, M. (2023). Tibial nerve SEPs in diagnosing lumbar spinal stenosis: The utility of segmental evaluation using P15 and N21. In Clinical Neurophysiology Practice (Vol. 8, pp. 49–57). Elsevier BV. https://doi.org/10.1016/j.cnp.2023.03.001