By Michael Rubin, MD

Professor of Clinical Neurology, Weill Cornell Medical College

Dr. Rubin reports no financial relationships relevant to this field of study.

SYNOPSIS: In a large retrospective review of treatment outcome for ulnar neuropathy at the elbow, no difference was found in outcomes between any of the various conservative or surgical therapies, but prognosis was determined by the severity of the lesion at time of diagnosis.

SOURCE: Beekman R, Zijlstra W, Visser LH. A novel points system to predict the prognosis of ulnar neuropathy at the elbow. Muscle Nerve doi: 10.1002/mus.25406.

With an incidence of 24.7/100,000, ulnar neuropathy at the elbow (UNE) is the second most common compression neuropathy, following carpal tunnel syndrome. Choosing between conservative measures and surgery is the major management decision in UNE, and is confounded by its many diverse causes, and an uncertainty as to which, if any, improve spontaneously. Accurate prognostication of UNE would be helpful to address this question.

Baseline information, including clinical, electrodiagnostic, and ultrasound data, was collected on two cohorts of UNE patients, diagnosed between 1998-2002 and 2006-2008, at Atrium Medical Centre, Heerlen, and St. Elisabeth Hospital, Tilburg, The Netherlands, and compared to outcome on follow-up, at least four or six months following surgery or conservative management, respectively.

Diagnosis of UNE was based on the presence of at least one symptom or sign of UNE, comprising tingling or numbness in the ulnar territory, or weakness or atrophy of ulnar innervated muscles, including first dorsal interosseous (FDI) and abductor digiti minimi (ADM), in association with supportive electrodiagnostic or ultrasonographic evidence. Electrodiagnostic evidence comprised motor conduction block across the elbow of at least 16%; motor nerve conduction velocity slowing across the elbow to < 46 m/s or > 15 m/s slower than in forearm segment; low motor- or sensory ulnar-evoked response amplitudes; and needle EMG showing abnormal spontaneous activity, enlarged or long duration motor unit potentials, or increased (> 15%) polyphasicity. Ultrasound evidence of UNE required enlargement of the ulnar nerve diameter at the level of the medial epicondyle, or 2 cm above or below, to > 2.4 mm, > 2.5 mm, or > 2.6 mm, respectively. Exclusionary criteria encompassed prior UNE surgery or severe traumatic origin of UNE, evidence of polyneuropathy, or genetically proven liability to pressure palsies. Conservative treatment included minimizing elbow flexion, avoidance of repetitive elbow flexion, and avoidance of crossing arms when seated, while surgery encompassed simple decompression or transposition, as determined by the surgeon. Statistical analysis comprised Student t-test, Mann-Whitney U test, chi-square test, and multiple logistic regression analysis, with P < 0.05 considered to be significant.

Among 220 patients with UNE at baseline, 84 and 136 in each cohort, 178 were available for re-evaluation (69 and 109, respectively), with 42 patients lost to follow-up, including three deaths, 18 refusing to participate, and 21 not responding. Among 178 responders, 94 men and 84 women, mean age was 52.8 years, and 161 had unilateral UNE. Complete recovery was reported in 23% (n = 40) and improvement in 37% (n = 66), with 40% (n = 72) noting either no change (28%, n = 49) or worsening (12%, n = 23). Overall, patients with left-sided UNE had a better outcome (P < 0.001), but there was no prognostic correlation found with respect to age, gender, symptom duration, presence of weakness, or type of treatment. Electrodiagnostically, conduction block to the ADM, but not the FDI, was associated with a good outcome, whereas low motor or sensory amplitudes presaged a poor outcome. Smaller ultrasound nerve diameter (mean 3 mm) predicted a good outcome, compared to a poor outcome where mean diameter was a mean of 3.3 mm. Right-sided UNE, more severe ADM weakness, and more pronounced ulnar thickening are poor prognostic indicators in UNE, whereas conduction block across the elbow of > 15% is a good prognostic sign, allowing outcome of UNE to be predicted by scoring these four parameters.

COMMENTARY

Can careful clinical examination of UNE distinguish demyelinating injury (Class I, neuropraxia) from axonal (Class II, axonotmesis) pathophysiology? In a prospective study of consecutively recruited subjects, four blinded examiners performed neurological examinations, electrodiagnostic studies, and ultrasound evaluations on patients with suspected UNE, and compared examination findings with pathophysiologic results. Although pronounced weakness and atrophy predicted axonal UNE, whereas normal muscle bulk and moderate weakness predicted neuropractic injury, in the majority of examinations the prediction was not reliable. Electrodiagnostic studies remain the single most reliable test to determine pathophysiology of UNE, more so than examination or ultrasound evaluation.