Predisposing factors for incomplete spontaneous recovery after Parsonage-Turner Syndrome

Parsonage-Turner Syndrome (PTS) is a rare idiopathic brachial neuritis that classically presents with sudden onset upper extremity pain followed by upper limb weakness, sensory disruption, and muscle atrophy. We hypothesized that the type of antecedent event before symptom onset would determine the degree of spontaneous recovery after PTS.

We retrospectively reviewed all patients who presented with PTS to a single tertiary referral center from January 2002 to December 2021. Each medical record was reviewed to exclude patients with any other identifiable neurologic etiology. The primary outcome was improved muscle strength measured by a modified British Medical Research Council (mBMRC) grading system. The spontaneous recovery cohort included patients with appreciable or full recovery (mBMRC 4 and 5). In contrast, patients with little to no recovery (mBMRC 0 to 3) were included in the incomplete recovery group. Antecedent events, demographic variables, affected upper extremity region, time between symptom onset and final visit, and presence of nerve surgery were analyzed. Two-tailed T-test and Fisher exact tests were used to compare continuous and categorical variables. Multivariable logistic regression was modeled to identify variables associated with spontaneous recovery.

100 patients with 144 extremities met the inclusion criteria. The average time from symptom onset to the final clinic visit was 3.5 years. 65 extremities (57.0%) spontaneously recovered without surgical intervention, whereas 49 extremities (43.0%) incompletely recovered. The spontaneous recovery cohort was younger (mean [SD] age, 47.4 [18.1] vs. 56.5 [18.7]; p = 0.02) and had fewer bilateral cases (count[%], 4 [6.5%] vs. 10 [26.3%]; p = 0.008). Multivariable logistic regression revealed that each year of increased age was associated with a 3% decreased chance of spontaneous recovery (OR[95%CI] 0.97[0.95, 0.99], p = 0.046). Bilateral involvement was associated with 93% decreased chance of recovery (OR[95%CI] 0.07[0.01, 0.39], p = 0.002), each additional muscle affected was associated with 10% decreased chance of recovery (OR[95%CI] 0.90[0.83, 0.97], p = 0.01), and traumatic antecedent events were associated with increased chance of recovery (OR[95%CI] 27.3[2.59, 287.5], p = 0.006).

Younger patients with unilateral symptoms and fewer muscle involvement have a greater chance of spontaneous recovery after PTS. PTS precipitated by trauma may have better spontaneous recovery than those precipitated by other causes.