Radiation-Induced Lumbosacral Plexopathy Workup

Updated: Sep 05, 2023
  • Author: Rajesh R Yadav, MD; Chief Editor: Dean H Hommer, MD  more...
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Imaging Studies

Routine spine and pelvis radiographs and myelograms are unremarkable in lumbosacral plexopathy.

The diagnosis of radiation plexopathy can be supported by diagnostic studies, such as computed tomography (CT) scanning and magnetic resonance imaging (MRI) of the pelvis. MRI is more sensitive than is CT scanning in detecting tumor recurrence. [3, 4] Enhancement of nerve roots and T2-weighted hyperintensity usually suggests tumor. Unfortunately, differentiation from tumor recurrence remains difficult. Generally, radiation plexopathy does not produce nerve enhancement. Positron emission tomography (PET) scanning with 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) may be helpful in diagnosing recurrent tumor.

Although PET/CT scanning can aid in differentiating tumor recurrence from radiation plexitis in oncology patients, it offers only limited resolution of the brachial or lumbosacral plexus. [19]


Other Tests

Electromyography (EMG) reveals myokymic discharges in most patients (57%) with radiation-induced lumbosacral plexopathy. Such changes occur over years; however, the absence of myokymia does not exclude radiation injury. EMG in clinically weak muscles also may reveal fibrillation potentials (ie, chronic, neurogenic motor unit changes with decreased recruitment). Paraspinal involvement occurs in 50% of cases. Compound muscle action potential (CMAP) of motor nerves may be low. [20, 21]