MR neurography of sciatic nerve injection injury

We report on magnetic resonance neurography (MRN) as a supplementary diagnostic tool in sciatic nerve injection injury. The object of the study was to test if T2-weighted (w) contrast within the sciatic nerve serves as an objective criterion for sciatic injection injury. Three patients presented with acute sensory and/or motor complaints in the distribution of the sciatic nerve after dorsogluteal injection and underwent MRN covering gluteal, thigh and knee levels. Native and contrast-enhanced T1-w images were employed to identify the tibial and peroneal division of the sciatic nerve while T2-w images with fat suppression allowed visualization of the site and extent of the nerve lesion. MRN in the two patients with clinically severe sensory and motor impairment correctly depicted sciatic injury: continuity of the T2-w lesion within the nerve at the lesion site and distal to it corresponded well to severe injury confirmed by NCS/EMG as axonotmetic or neurotmetic. Topography of the T2-w lesion on cross-section corresponded to predominant peroneal involvement; moreover, associated denervation patterns of distal target muscles were revealed. One of these patients completely recovered with concomitant complete regression of MRN abnormalities on follow-up. The third patient experienced transient sensory and mild motor impairment with complete recovery after 2 weeks. In this patient, T2-w signal within the nerve and distal target muscles remained normal indicating only mild, non-axonal nerve affliction. Our case series shows that MRN can be very useful in precisely determining the site of sciatic injection injury and may provide diagnostic criteria for the assessment of lesion severity and recovery.