Athirty-five-year-old man was evaluated as an outpatient for the subjective
complaint of progressive bilateral lower extremity weakness and difficulty
with walking. The patient reported that the weakness had started one year
prior to presentation and had been progressive in nature with substantial
worsening during the previous two months. The patient stated that he was able
to walk only one-half block with the assistance of a cane. He also reported
difficulty rising from a seated position, with numbness of both lower
extremities, and the recent development of urinary frequency. He stated that
he had not had any fevers, chills, night sweats, dysuria, or urinary
incontinence. The medical history was positive for a diagnosis of fibrous
dysplasia due to multiple rib lesions noted on a chest radiograph made twenty
years earlier. The patient was not taking any medication and had been
participating in physical therapy without any notable improvement in lower
extremity strength.
On physical examination, the patient was 1.6 m tall and weighed 150 kg. He
walked with a wide-based, shuffling gait with extreme difficulty, requiring
the assistance of a cane. Pertinent findings on motor examination included
bilateral muscle strength of grade 4 of 5 for the iliopsoas and quadriceps,
grade 3 of 5 for the tibialis anterior and gastrocnemius, and grade 2 of 5 for
the extensor hallucis longus. The patient was hyperreflexic in both lower
extremities and had positive Babinski signs and sustained ankle clonus.
Plain anteroposterior and lateral radiographs of the cervical spine showed
dense sclerotic hypertrophic changes involving the right first rib as well as
the right posterior elements of the seventh cervical vertebra. Anteroposterior
and lateral radiographs of the upper thoracic spine were difficult to
interpret because of the body habitus of the patient. A plain radiograph of
the chest demonstrated sclerotic osseous proliferation of multiple ribs on the
right side. A computed tomographic scan of the cervical, thoracic, and lumbar
spine demonstrated multiple areas of sclerotic hypertrophy of the ribs and
anterior and posterior spinal elements on the right side. The most notable
involvement was at the level of the first thoracic through the fourth thoracic
vertebra, where osseous hypertrophy of the posterior elements resulted in
canal stenosis that ranged from 50% to 90% (Figs.
1-A and 1-B).
Because of the worsening neurologic condition, the patient agreed to
proceed with a cervicothoracic decompressive laminectomy and instrumented
arthrodesis. The posterior decompression was carried out pedicle to pedicle
from the seventh cervical vertebra to the fifth thoracic vertebra with the use
of a high-speed side-cutting burr (Fig.
2). Toward the completion of the decompression, sudden complete
loss of motor signals to the lower extremities was noted on motor evoked
potentials. The decompression was completed, and the instrumented arthrodesis
portion of the procedure was aborted because of the intraoperative changes
noted on the spinal cord monitoring and the desire to obtain nondistorted
postoperative magnetic resonance images to assess spinal cord parenchymal
changes. The blood pressure was continuously maintained at a mean arterial
pressure of >90 mm Hg, and methylprednisolone was administered at the
standardized dose for spinal cord injury (30 mg per kg loading dose followed
by 5.4 mg per kg for twenty-three hours).
Magnetic resonance imaging scans performed after the patient had stabilized
postoperatively demonstrated edema within the spinal cord from the seventh
cervical through the fourth thoracic vertebra with adequate decompression of
the neural elements. Postoperatively, the patient was noted to have no motor
function in the lower extremities with preservation of light touch and
pinprick (T3 ASIA [American Spinal Injury Association] B with sacral
sparing)4. The final
report on the microbiological culture of the specimen indicated no growth, and
melorheostosis was diagnosed on the basis of the pathological evaluation of
the specimen (Fig. 3). At the
time of the follow-up examination six months after surgery, the patient was
noted to have 4+ of 5 strength in the iliopsoas, quadriceps, and tibialis
anterior muscles bilaterally and 4 of 5 strength in the extensor hallucis
longus and gastrocnemius muscles bilaterally. In addition, he had a positive
Babinski sign bilaterally and sustained ankle clonus in the left lower
extremity. No evidence of sagittal plane deformity either clinically or on the
lateral radiograph was noted. Since the patient underwent a multilevel
laminectomy that crossed the cervicothoracic junction without an arthrodesis,
he is at an increased risk for the development of sagittal plane instability.
Therefore, he will need evaluation with anteroposterior, lateral, and
flexion-extension radiographs at regular intervals to monitor for this
complication.