Comparison of ulnar and median nerve injury and muscle denervation secondary of these with electrodiagnostic study and magnetic resonance imaging

Comparison of electrodiagnostic tests and magnetic resonance imaging in muscle denervation secondary to ulnar and median nerve injuries. Muscle denervation is a condition which is caused by deterioration of the relationship between motor neuron and muscle fibers. Muscle denervation occurs as the results of central and peripheric nervous system problems. Electrodiagnostic tests and physical examination are used to diagnose of muscle denervation and also to identify severity and to follow temporal course. But electrodiagnostic studies, especially needle EMG, are invasive, painful and hard to tolerate for some patients. Sometimes discrepancies occur between interpretation of the electrodiagnostic study results due to examination period and physicians experience. Over the last years there has been increasing evidence that magnetic resonance ımaging (MRI) can significantly aid in the diagnose of peripheric nerve injuries and muscle denervation. Median and ulnar nerves are mostly affected peripheral nerves in focal neuropathies, especially in chronic compression neuropathies. The most common innervation anomalies are also seen between median and ulnar nerves and these anomalies may complicate the diagnosis of focal neuropathies. The differential diagnosis may also difficult in special situations if electrodiagnostic tests can not be performed such as using anticoagulants. In these situations, MRI may be used as an important diagnostic tool in evaluation and localisation of ulnar and median nevre injuries. The aim of this study was questioning of the diagnostic utility of MRG in determining denervated muscles in cases of focal median and ulnar nerve lesions and comparing the results of MRI with electrodiagnostic tests.. Forthy patients diagnosed as median/ulnar nerve injury, carpal tunnel syndrome (CTS), ulnar entrapment neuropathy and ulnar /median mononeuropathies according to motor and sensory nerve conduction studies were included in the study. In these cases the muscles with denervation and/or motor unit loss according to needle electromyography were also evaluated with MRI. Coronal and axial plains fat-suppressed (FSPD) and short tau invertion recovery (STIR) sequences with 3mm slice thickness were performed and evaluated for the existence of muscle edema. All patients' demographic and clinical features were compared with MRI findings. While denervation findings in needle EMG accepted as a reference paramater, diagnostic sensitivity of MRI was calculated as 40,9% and specificity was calculated as 94,3% . In conclusion, the results of this study show that the sensitivity of MRI parameters for the diagnosis of muscle denervation is low. For this reason, electrodiagnostic tests can be accepted as a gold standard or first choice diagnostic test in diagnosing muscle denervation. But, magnetic resonance imaging can be used in diagnosis of muscle denervation in cases of electrodiagnostic tests are contraindicated. However clinical studies about this issue are very limited and further resarch is needed.