Electrodiagnostic characteristics of upper lumbar stenosis: Discrepancy between neurological and structural levels

Abstract

Background: Radiculopathies caused by spinal stenosis in the upper lumbar spinal canal (L1/2, L2/3, L3/4) have not been comprehensively investigated. Methods: This retrospective study reviewed 14 patients from a tertiary hospital outpatient clinic. The inclusion criteria were upper lumbar stenosis seen on MRI and radiculopathies with active denervation confirmed on electromyography. Patients with any other conditions that could explain the clinical or electrophysiological manifestations were excluded.Results: Neurogenic findings were predominantly observed in L5 or S1 myotomes on electromyography. Abnormal spontaneous activity was observed in distal muscles in all patients and in proximal muscles in eight patients. Axonal involvement was bilateral in 10 patients and unilaterally in 4 patients. MRI showed redundant nerve roots in 13 patients with chronic reinnervation on electromyography.Conclusions: Upper lumbar spinal stenosis usually causes L5 or S1 radiculopathies with diverse patterns. This discrepancy may cause diagnostic confusion. K E Y W O R D S electromyography, lumbosacral, magnetic resonance image, nerve root compressions, radiculopathy, upper lumbar spinal stenosis

Redundant nerve roots on magnetic resonance imaging can predict ongoing denervation in patients with lumbar spinal stenosis

“…Another intraoperative study found that conduction velocity in RNRs was reduced to approximately half that in normal roots 14 . In the study of Kim et al, 15 all 14 patients with upper‐level LSS had active denervation potentials on EMG, and spine MRI revealed RNRs in all except one patient whose symptom onset duration was as short as 1 month.…”