A Study of Sensory Nerve Conduction in Pre- and Post-immunoglobulin Treatment of Guillain-Barré Syndrome.

BACKGROUND: Guillain-Barré syndrome (GBS) is a condition characterized by acute and progressive weakness that impacts the limbs, facial muscles, and bulbar muscles due to acute polyneuro-radiculopathy. Typically, an infection that results in immune-mediated nerve dysfunction is what starts the disease. Patients often encounter paresthesia or discomfort before progressing to muscle weakness, initially in the lower extremities (which may include some proximal components) and subsequently in the upper extremities. The features of polyneuropathy identified during electrophysiology tests, bolstered by evidence of acquired demyelination in the nerve conduction study (NCS), support the clinical diagnosis of GBS. In peripheral neuropathies, NCS often reveals abnormalities in nerve conduction parameters. A specific pattern observed in the sensory nerve conduction study (SNCS), referred to as "sural sparing," signifies that the sural nerve, located near the calf muscles, remains relatively unaffected compared to other sensory nerves. Very few studies have been conducted to investigate improvements in sensory nerve conduction (SNC) parameters before and after intravenous immunoglobulin (IVIG), offering limited clinical correlation for the recovery and prognosis of the disease. The study aimed to observe the NCS parameters of the sensory nerves in both the upper and lower limbs, before and after the infusion of IVIG.

METHODOLOGY: This study was an observational investigation conducted in the neurophysiology laboratory of the Physiology Department at a rural medical college in central India. Fifty clinically diagnosed cases of GBS aged between 18 and 60 years were referred from the Department of Medicine to the Physiology Department for conducting the NCS. Basic sociodemographic information, along with clinical history, was collected. Subsequently, the RMS EMG EP Mark-II machine was employed to examine the sensory nerve action potentials (SNAPs), such as amplitude (in mV) and conduction velocity (in ms), of the sensory nerves in both the upper and lower limbs before and after IVIG infusion. The IVIG infusion occurs within one week of clinically diagnosing GBS. Following an initial NCS, a second NCS follow-up study was conducted one week after the IVIG infusion to analyze the changing trend in sensory nerves.

RESULTS: Upon analysis, no significant correlation was observed between the pre- and post-IVIG SNAPs of the median and ulnar nerves. However, the sural nerve conduction velocity's p-value of 0.033 demonstrated statistical significance, suggesting that the sural nerve is comparatively spared, confirming sural sparing. However, the SNAP of the sensory nerves in GBS patients showed a significant improvement overall, and only NCS quantified the percentage of improvement.

CONCLUSION: According to the study, the NCS of sensory nerves showed a positive change in the parameters examined before and after the infusion of IVIG. This underscores the timely intervention of GBS with IVIG, and conducting the sensory conduction study diligently will enhance knowledge about the recovery period. Additionally, it supports the treating physician in making informed interventions based on the results post-IVIG infusion. This enhancement in the sensory nerves can only be quantified through NCS.