# Case report of stiff - person syndrome and literature review

## TL;DR

This case report describes a patient with stiff person syndrome misdiagnosed for years and highlights how electromyography can help diagnose and monitor treatment.

## Contribution

The study demonstrates the use of needle EMG as an objective tool for SPS diagnosis and treatment evaluation.

## Key findings

- Needle EMG showed increased spontaneous motor unit activity in SPS patients at rest.
- Diazepam reduced muscle electrical signals, suggesting a therapeutic effect.
- Anti-GAD65 antibodies confirmed the SPS diagnosis after EMG findings.

## Abstract

Currently, there is no objective evaluation method to measure muscle tension and therapeutic effects in patients with stiff person syndrome (SPS). We aimed to investigate objective evaluation criteria for diagnosis and treatment. We used needle electromyography (EMG) to record muscle electrical signals before and after the diazepam drug trial to diagnose a patient with SPS.

We present a patient who was misdiagnosed as having an "anxiety state" for more than a decade because of recurrent tension, worry, and intermittent fear, resulting in generalized muscle stiffness and even falls. Conventional needle EMG was performed on the limbs and axial muscles. The changes in muscle electrical signals before and after diazepam drug trials were recorded.

EMG revealed a significant increase in spontaneous motor unit potentials in the patient's limbs and axial muscles at rest. After intravenous injection of diazepam, the spontaneous motor unit gradually reduced and ultimately disappeared. Based on these results, anti-antibody testing for SPS was performed one week later. The results revealed a high titer of anti-glutamic acid decarboxylase 65 antibodies (GAD65-Abs) in serum, while anti-amphiphysin antibodies were negative. The diagnosis was confirmed as SPS.

Needle EMG is a convenient tool that can provide diagnostic direction for SPS before genetic testing, enabling clinicians to select specific genes for testing and thereby shortening the time required for clinical examination and diagnosis for patients. Additionally, it can be used to verify the efficacy of experimental medications during testing.