What is the rate of Somatosensory Evoked Potentials (SSEP) abnormalities in Multiple Sclerosis (MS)?

From the Guidelines

Somatosensory evoked potentials (SSEPs) show abnormalities in approximately 60-85% of patients with multiple sclerosis (MS), making them a valuable diagnostic tool. These abnormalities typically manifest as delayed latencies and reduced amplitudes in the evoked responses, reflecting demyelination and axonal damage in the somatosensory pathways. The rate of SSEP abnormalities varies depending on the clinical presentation and disease duration, with higher rates observed in patients with more advanced disease or those with sensory symptoms 1. SSEPs are particularly useful in detecting clinically silent lesions in the dorsal column-medial lemniscus pathway, which can help confirm MS diagnosis when combined with other diagnostic criteria.

Some key points to consider when interpreting SSEP results in MS patients include:

• The test is most sensitive when performed on both upper and lower limbs, as this increases the chance of detecting subclinical lesions.
• While MRI remains the gold standard for MS diagnosis, SSEPs provide complementary functional information about the integrity of sensory pathways that cannot be directly assessed by structural imaging alone 1.
• This neurophysiological assessment helps in both initial diagnosis and monitoring disease progression in MS patients.
• Advanced MRI techniques, such as magnetization transfer MRI and proton magnetic resonance spectroscopy, can add information on the biochemical nature of MS-related abnormalities and tissue disruption, but their use for monitoring treatment effects is hampered by a lack of standardization between centers 1.

Overall, SSEPs are a valuable tool in the diagnosis and management of MS, providing important information about the functional integrity of sensory pathways that can complement MRI and other diagnostic tests.

From the Research

SSEP Abnormalities in MS

• The rate of SSEP abnormalities in MS patients is significant, with one study finding that wave P22 was statistically significantly extended in MS diagnosed patients compared to healthy examinees 2.
• Another study found that recording the middle-latency components of the median nerve somatosensory evoked potentials (SEPs) increased the diagnostic sensitivity in patients with MS from 50% to 75% 3.
• A study of 161 patients with relapsing-remitting MS or clinically isolated syndrome found that tibial nerve SSEP (tSSEP) were less frequently abnormal than spinal cord MRI (22% vs. 68%, p < 0.001), but higher EDSS scores were significantly associated with abnormal tSSEP 4.
• In a study of 143 patients with symptoms suggestive of MS but normal initial assessments, evoked potential studies were abnormal in a small percentage of patients, including somatosensory evoked potentials (SSEP) in 4.9% of patients 5.
• A whole brain DTI study found that SSEP latencies were representative of widespread microstructural change, and especially demyelination in patients suffering from MS, with significant correlations of FA and RD to SSEPs 6.

Key Findings

• SSEP abnormalities are common in MS patients, with extended latencies and altered amplitudes compared to healthy controls.
• SSEP can be a useful tool in the diagnosis and monitoring of MS, particularly in combination with other diagnostic tests such as MRI.
• The relationship between SSEP abnormalities and disease severity is complex, with some studies finding correlations between SSEP latencies and EDSS scores, while others do not.

Study Results

• Study 2 found that 50 MS patients had statistically significant extended wave P22 compared to 50 healthy controls.
• Study 3 found that 20 consecutive MS patients at early onset had increased diagnostic sensitivity with median nerve SEPs.
• Study 4 found that 161 patients with relapsing-remitting MS or clinically isolated syndrome had less frequent abnormal tSSEP compared to spinal cord MRI.
• Study 5 found that 143 patients with symptoms suggestive of MS but normal initial assessments had abnormal SSEP in 4.9% of patients.
• Study 6 found that 46 patients with MS or clinically isolated syndrome had significant correlations of FA and RD to SSEPs.