Painful radial nerve neuropathy with focal hourglass-like nerve constriction as a variant of distal neuralgic amyotrophy

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Abstract
Neuralgic amyotrophy (NA, Parsonage-Turner syndrome) is an autoimmune multifocal painful neuropathy that has a classic pattern of brachial plexus involvement in most patients. Cases in which motor and sensory deficits occur below the elbow joint are classified as a separate form – distal NA. In contrast to the classic pattern of NA, patients with distal NA recover less well and require surgical treatment.Objective: to describe the clinical and instrumental characteristics of patients with focal hourglass-like nerve constriction (FHNC) of the radial nerve.Material and methods. The clinical, electrophysiological and neuroimaging data of 24 patients with painful radial nerve neuropathy (5 women and 19 men, mean age 41.9±15.5 years) were analyzed. The average time from onset of pain to diagnosis was 10.8 months (median 5 months; minimum 4 days, maximum 5 years and 8 months). Glucocorticoids (GC) were taken by 8 patients (33%). Nine patients underwent surgery. The control group consisted of 60 individuals matched for age and gender.Results. All patients complained of neuropathic pain in the affected upper extremity with an average intensity of 9.4 (median 9.5) on the visual analogue scale (VAS). The duration of the pain syndrome was on average 13.4 days (median 12.5 days). According to electromyographic data, all patients showed changes in the muscles of the affected side in the form of chronic denervation. MRI of the nerve trunks in 12 patients, revealed no changes on the affected side in 5 patients (41.6 %). Edema of the nerve trunks was found in 5 patients (41.6%). Muscle atrophy was found in one patient (8.3%) and one patient (8.3%) had FHNC. Comparison of the ultrasound data of the cross-sectional area (CSA) of the affected and unaffected sides showed a significant enlargement of the radial nerve on the affected side (p=0.027); no statistically significant differences were found when comparing the affected and unaffected sides with the control group. FHNC in the radial nerve was found in 19 patients, with both sides affected in two cases. Four patients recovered completely, 3 of them (75 %) received GC and 2 (50 %) underwent surgery. Incomplete recovery was observed in 12 patients (50%). Eight patients (33%) did not recover, of whom only one received GC, while 4 (50%) underwent surgery. Of the patients who underwent surgery, 5 patients (55.6%) recovered completely or partially, 44% did not recover. The mean follow-up time was 10.2±2.9 months.Conclusions. Radial nerve painful neuropathy is a variant of NA whose morphological manifestation is the phenomenon of FHNC detected by ultrasound in the peripheral nerves. The use of ultrasound facilitates the diagnosis of the disease, leading to an earlier diagnosis and consequently to a more favorable prognosis. Surgical treatment should be favored in cases of FHNC.

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