Clinical History
A 53-year-old male patient with squamous cell carcinoma of the tonsils, which had been controlled with radiotherapy, now presented with myelopathic symptoms.
Imaging Findings
A 53-year-old man had been diagnosed with a high grade squamous cell carcinoma of the left tonsil in March 2001. He had undergone induction chemotherapy with cisplatinum and 5-fluorouracil followed
by radical radiotherapy with 44 Gy in 22 fractions and phase 2 22 Gy in 11 fractions. He had had an excellent response to the treatment and in October 2001, there had been no evidence of tonsillar or
nodal involvement. In August 2002, he developed progressive sensory symptoms in his hands and an unsteadiness of his legs. MRI scan showed extensive swelling of the cervical cord and the presence of
a ring-enhancing lesion at the level of the body of the C2 vertebral body.
Discussion
Radiation myelopathy is a condition which may be seen in acute or early delayed or late delayed phases. The acute phase, which is extremely rare, is seen during radiotherapy. In the acute phase,
patients may have paresthesia or weakness progressing to paralysis. MRI is often negative in this acute stage, and the symptoms usually resolve after radiotherapy. Early-delayed transient myelopathy
is usually seen two to six months following irradiation of the cord. It is probably due to a transient demyelination occurring especially in the dorsal columns of the spinal cord. Patients typically
present with shooting pain along the back of the neck that radiates down to the feet during flexion of the neck (Lhermitte's sign). It is clasically seen after mantle radiotherapy. The symptoms tend
to resolve spontaneously over several months and do not progress. The late delayed-chronic progressive radiation myelopathy occurs due to the administration of a high dose of radiation and is seen
months or even years after irradiation. It is thought to be caused by damage to the white matter due to vascular damage and occlusion. The most widely accepted dose limit for spinal cord irradiation
is 45 Gy in 22–25 fractions. The risk of myelopathy increases significantly with higher radiation doses, shorter intervals, association with vascular disease such as diabetes or hypertension or
concomitant chemotherapy. When the cord receives 57–61 Gy there is a 5% incidence of radiation myelopathy which increases to 50% when the cord receives 68–73 Gy. Chronic progressive
radiation-induced myelopathy usually develops in 6–12 months after therapy and presents with a gradual onset of paresis, numbness, and sphincter dysfunction. The initial signs are subtle and
may include decreased temperature sensation and proprioception. These signs may stabilize or slowly progress to muscle weakness, foot drop, Brown–Sequard syndrome, incontinence and sometimes to
complete paresis below the level of irradiation. The diagnosis is made clinically with the help of the MR imaging technique. The spinal cord shows an abnormally increased T2 signal which may span
several segments above and below the level of irradiation. On T1-weighted images, the abnormal area may appear to be isointense to hypointense. There may be cord expansion and focal eccentric
enhancement may be seen in the cord at the site of maximum irradiation. The site of contrast-enhancement correlates with the clinical manifestations. Focal necrosis of the cord may occur. In later
stages, cord atrophy is seen. Secondary changes from Wallerian degeneration are seen in the chronic stages above and below the level of the initial cord abnormality. These changes may be difficult to
distinguish from intramedullary metastatic lesions and leptomeningeal metastases. Treatment is given with hyperbaric oxygen and sometimes with steroids.
Differential Diagnosis List
Delayed radiation myelopathy.
Final Diagnosis
Delayed radiation myelopathy.
