Transient radiation myelopathy (TRM) is a benign form of myelopathy, characterised by Lhermitte’s sign; the subjective complaint of unpleasant electric-shock sensation radiating down the extremities upon neck flexion.
Incidence of TRM has been reported between 3.6 to 10.3 % in patients who have received radiation to the head and neck region.r
Studies suggest the median development time for Lhermitte's sign is 3.0 months after the completion of RT, and the appearance of such a sign lasts, on average, 17 weeks.
Risk factors for developing TRM include the extent of the spinal cord included in the treatment field and the dose given per fraction eg >2 Gy per fraction for once daily fractionation.r Concurrent chemotherapy can also increase risk of developing Lhermitte's sign.r
There is also a higher risk for patients who have received bilateral neck-boost irradiation.r
The development of TRM has not been shown to predict the development of radiation myelitis.r