Role of sciatic nerve stiffness in surgical decision making and follow up in patients with deep gluteal syndrome

The study shows the relevance of sciatic nerve stiffness assessed by strain elastography using ARFI (Acoustic Radiation Force Impulse) for surgical decision making and the follow up of patients with deep gluteal syndrome (DGS). The research focuses on nerve stiffness associated with knee movements in order to determine the degree of nerve entrapment. Neurological examination, MRI of pelvis and electromyography (EMG) were performed as well. The sciatic nerve was scanned by ARFI (strain) elastography during knee movements in patients with DGS (143). In 54 patients surgical treatment was indicated, while 24 of them underwent surgery. The results were based on tissue response to ARFI by color elastogram and stiffness ratio. Diameters of the sciatic nerve in patients with DGS during knee flexion were statistically significantly lower than during extension movement (p<0.01). In patients with DGS (in ones without indication and the ones scheduled for surgery) sciatic nerve stiffness ratio was significantly increased (p<0.01) during knee flexion. Patients scheduled for surgery confirmed increased sciatic nerve stiffness during knee movements, compared with those without indications for surgery (p<0.05). Sciatic nerve recovery after surgery by diameter and stiffness ratio was marked (r=0.881). The correlation between MRI and EMG findings and ARFI nerve stiffness values in patients scheduled for surgery was high (r=0.963). The overall specificity of method was 93.5%, sensitivity was 88.9% with accuracy of 90.6%. ARFI elastography (by strain) is a diagnostic procedure based on nerve stiffness assessment and a useful tool in decision making for surgery and the follow up.