2025 Workshop Handout Bundle-W46AS EDX and Clinical Approach to Lumbosacral Plexopathies

W46AS EDX and Clinical Approach to Lumbosacral Plexopathies - Vazquez Do Campo

Pdf Summary

This review discusses the complex diagnosis and electrodiagnostic (EDX) evaluation of lumbosacral plexopathies—conditions affecting the lumbosacral plexus, a network of nerves (L1-S4 roots) supplying the lower limbs. The plexus is anatomically divided into upper lumbar (L1-L4) and lower lumbosacral (L5-S4) segments, each with distinct sensory and motor innervations. Disorders range from trauma and compression to metabolic and inflammatory causes, with diabetes being a common risk factor.<br /><br />Clinically, lumbosacral plexopathies present with patchy leg weakness, hyporeflexia, sensory disturbances, and pain that can mimic radiculopathies. Injury to upper plexus causes proximal weakness; lower plexus injury affects distal muscles and can cause foot drop. Pain is often neuropathic, with signs of small fiber involvement (allodynia, hyperalgesia) suggesting inflammatory/metabolic etiologies.<br /><br />Electrodiagnostic confirmation requires abnormalities in multiple muscles innervated by different nerves/roots, with abnormal sensory responses and typically normal paraspinal muscles (except in radiculoplexus neuropathy - LRPN). Routine nerve conduction studies (NCS) evaluate primarily L5-S2 segments; non-routine studies (lateral femoral cutaneous, saphenous, femoral nerves) assess upper lumbar plexus. Needle EMG should target both proximal (hip girdle) and distal muscles for comprehensive assessment, as patchy denervation confirms plexopathy.<br /><br />Differentiating plexopathy from radiculopathy or mononeuropathies involves recognizing abnormal sensory nerve action potentials (SNAPs), patchy involvement across multiple myotomes, normal paraspinals (in pure plexopathy), and absence of imaging findings for root compression. LRPN, associated with diabetes and inflammation, often shows bilateral asymmetric involvement and paraspinal abnormalities.<br /><br />Key points: Lumbosacral plexopathies are under-recognized and should be considered in patients with leg symptoms not localized to single nerves/roots. Electrodiagnostic studies must be tailored and interpreted cautiously, considering patient factors. Needle EMG of proximal muscles enhances diagnostic yield. Clinical and imaging correlation remains essential in equivocal cases.

Keywords

Lumbosacral plexopathies

Electrodiagnostic evaluation

Nerve conduction studies

ncs

Needle EMG

Radiculoplexus neuropathy

Diabetic plexopathy

Neuropathic pain

Sensory nerve action potentials

Lower limb weakness

Plexus anatomy