EMG in piriformis syndrome diagnosis: Reliability of peroneal H-reflex according to results obtained after surgery, Botox injection and medical treatment.

Diagnosing piriformis syndrome (PS) throughout the past decades was not that easy, however peroneal H-reflex was proved as reliable test for PS with the change in wave amplitude and delay in conduction as parameters for diagnosis. We interpreted these parameters according to treatment's results carried out for patients presenting clinical PS, aiming to define a threshold value for peroneal H-reflex delay to accurately diagnose. A retrospective mono-centric review of 27 patients, 9 females and 18 males, aged 22-65 years, benefited from peroneal H-reflex test and treated for clinical PS. These patients were classified into 3 groups according to treatment modality they received: 11 patients underwent surgical treatment, 7 patients underwent Botox injections (4 of them benefited from surgery later on) and 9 patients received pharmacological treatment. From 11 operated patients with 4 < delay < 9 ms, 10 had complete improvement and 1 remained in pain. For 7 patients having injection of Botox 100-300 IU, with 5 < delay < 7 ms had a transient recovery, 4 of them have benefited later from surgery, the 3 others reproved pain. Between 9 patients who have declined invasive treatment, 7 patients with 4 < delay < 10 ms didn't demonstrate any improvement after medical treatment and are suspected of PS, 2 others with delay < 4 ms recovered from a non-confirmed PS. A threshold value to diagnose PS was reached through peroneal H-reflex delay ranges, classified as: high with a delay > 5 ms, moderate: 4 < delay < 5 ms and poor: <4 ms.