Background Ulnar neuropathy at the elbow is the second most common compression neuropathy preceded by carpal tunnel syndrome. Although this diagnosis has been traditionally confirmed by electrodiagnosis (EDX), ultrasonography (US) is a re-emerging alternative method which can also evaluate the cubital zone anatomy. This study determines the maximum amount of US sensitivity and specificity by assessing different sonographic parameters and evaluates consistency and diagnostic value of the best US method in compare with EDX.
Methods We included 66 participants (32 elbows of patient and 34 normal elbows) and performed physical exam, US and EDX for both groups. Patients were classified into four severity grades using EDX criteria. The parameters of US were cross sectional area (CSA) of ulnar nerve at three levels: medial epicondyle (CSA med), 2cm distal (CSA dist) and 2cm proximal (CSA prox) to medial epicondyle. Then we would be able to evaluate consistency between two tests using area under receiver operating curve (AU-ROC) method and also to determine the optimum CSA cut-off point to better diagnosis of ulnar neuropathy by US.
Results Our findings showed that CSA med and CSA dist had significantly larger size in patients compared to normal participants (P-value =0.01 and 0.05, respectively). This increase in nerve size was more prominent among those who had axonal lesion rather than patients with demyelinated lesion (p-value <0.01). Moreover those who had longer duration of symptoms had significantly higher CSA med. and CSA dist. (p-value=0.015 and 0.001 respectively). The other promising findings were two important points; First a strong correlation between CSA med. and severity grade (p-value=0.034) and the second correlation was between CSA med and CSA dist. with a cross-elbow nerve conduction velocity (NCV) (p-value=0.01 and 0.02, respectively). Finally we assessed US diagnostic value as it showed AU-ROC =0.871, that means a very good coverage for an alternative diagnostic method. Also our results showed specificity of 80% and sensitivity of 84% for US in the CSA med cut-off point =9mm2 for diagnosis of ulnar nerve entrapment at elbow.
Conclusions Based on these results we can conclude that US is a highly sensitive and specific method to diagnose ulnar neuropathy at elbow and can be used as an alternative and complementary method in diagnosis of ulnar neuropathy at elbow in particular when EDX is not available. However it could not be still a definitive and substitute mutually exclusive method to EDX in diagnosis of ulnar neuropathy
Disclosure of Interest None declared