Clinical Diagnosis of Coincident Carpal and Cubital Tunnel Syndromes

Introduction

Coincident ulnar compression at the cubital tunnel can affect patients with carpal tunnel syndrome, but poses a diagnostic challenge - sensitivity of “gold standard” nerve conduction study results is limited to 60-70%.  To date, this coincidence has not yet been reported, and a better characterization of diagnostic methods may improve detection of coincident compression neuropathy.

Methods

A retrospective chart review of 515 patients was performed from patients treated for carpal tunnel and/or cubital tunnel release by two university-based hand surgeons. Cohorts included patients with isolated carpal tunnel syndrome (n=337) and patients with coincident carpal and cubital tunnel syndromes (n=178). Patients were characterized according to demographics, medical history, physical exam, and nerve conduction studies. Univariate and multivariate logistic regression identified predictors of coincident nerve compression. The “K-B Classification System” was constructed by integerizing regression coefficients of predictive factors in the multiple regression model. Sensitivities, specificities, positive, and negative predictive values were calculated for each class to assess risk of coincident compression neuropathy. 

Results
Loss of intrinsic hand strength, ulnar sensation loss, positive elbow flexion test, positive cubital tunnel Tinel's sign, and abnormal ulnar nerve NCS result were selected (Table 1). Profiles and associated specificities and positive predictive values were recorded for each classification (Table 2).  Positive predictive value of K-B classes ranged from 0.605 (K-B Class I) to 0.923 (K-B Class V).  Specificities ranged from 71.69% (K-B Class I) to 99.55% (K-B Class V).

Conclusions
Rather than being utilized as a gold standard diagnostic, given its low sensitivity at the cubital tunnel, NCS testing should be considered as a supplementary diagnostic factor for identifying coincident cubital tunnel syndrome in carpal tunnel syndrome patients.  A compelling physical exam profile can very strongly suggest the presence of coincident compression, even pre-NCS evaluation – for example, physical presentation alone can portray a K-B Class IV patient with 98.20% specificity and a PPV of 0.906. In this developmental cohort, the score was a robust method for characterizing patients with coincident nerve compression using factors routinely utilized to assess compression neuropathy at the cubital tunnel.