Radiation-Induced Lumbosacral Plexopathy Clinical Presentation

Updated: Sep 05, 2023
  • Author: Rajesh R Yadav, MD; Chief Editor: Dean H Hommer, MD  more...
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With prior radiation treatment and initial symptoms, a recurrent tumor may need to be distinguished from radiation plexopathy. The median symptom-free interval for radiation-induced lumbosacral plexopathy, from treatment to the initial neurologic symptom, is 5 years, with a range of 1-31 years. [9]

  • Patients with radiation-induced lumbosacral plexopathy most commonly present with painless weakness in 1 or both legs. Pain is present initially in only 10% of patients, although ultimately it is noted in as many as 50% of patients. The incidence of initial pain is lower than that of brachial plexopathy. This pain is described in varying terms, such as aching, burning, pulling, cramping, and lancinating; however, pain rarely is a major problem.

  • Weakness is asymmetrical. At the height of illness, the ratio of bilateral to unilateral illness is 5:1. Acute lower extremity paralysis has been noted in a patient with cervical cancer 10 weeks after completion of radiation treatment. [11]

  • Sensory loss occurs in 50-75% of patients and is more severe with greater motor impairment, which can add significantly to disability.

  • Bladder or bowel incontinence may occur. [12]

Studies by Skolka et al indicated that in patients with early onset radiation-induced neuropathies, a painful, monophasic course is common. The reports included individuals with brachial and lumbosacral plexopathies, radiculopathies, and mononeuropathies, with post-radiation neuropathic onset averaging about 2 months. The patients’ responsiveness to steroids and the presence of microvasculitis suggested that an inflammatory-immune mechanism is associated with early onset radiation-induced neuropathies. [13, 14]  



See the list below:

  • In radiation-induced lumbosacral plexopathy, motor deficits in the lower extremities commonly are bilateral (80%) and asymmetrical. Diffuse limb weakness with distal predominance in L5-S1 distribution is relatively common (55% of patients). Exclusive proximal paresis in the distribution of L2-L4 is less common (10% of patients), as is femoral neuropathy (5% of patients). Moderate weakness is present in 50% of patients, with equal distribution of mild and severe weakness.

  • Deep tendon reflexes (DTRs) almost always are abnormal at the knees and/or ankles and usually are present bilaterally.

  • Sensory impairments are present in most patients (75%) and more often are bilateral. No specific sensory modality is favored. The distal lower extremities are affected more commonly than are the proximal lower extremities. Impaired deep sensation occurs with severe, superficial sensory loss.

  • Skin changes may be present in areas of radiation portals.



Radiation dosage, treatment technique, and concomitant use of chemotherapy are associated with development of radiation-induced lumbosacral plexopathy.