Persistent low-back pain in children that is not associated
with trauma and is not relieved by two to three weeks of rest, modification
of activity, or nonsteroidal anti-inflammatory medication is uncommon.
If a child has persistent, unremitting low-back pain, a serious
underlying pathological cause should be suspected and appropriately
investigated and a thorough evaluation, including the recording
of a medical history, clinical examination, and radiography, should
be performed.
The purpose of the current report is to describe our findings
in two patients, who were eight and thirteen years of age when they
presented with pain in the low lumbar area secondary to a lesion
in the sacrum. These two unusual cases highlight the importance
of a careful clinical examination and imaging of the sacrum in the
evaluation of low-back pain in children.
Case 1. An eight-year-old girl presented with low-back pain that
had had an acute onset. She was seen in an emergency room, where
radiographs of the lumbar spine were interpreted as normal. The
pain continued for a week, and she was then seen at our institution.
She described low-back pain that radiated to the groin and the anterior
aspects of the thighs. She reported no tingling or numbness in the
lower extremities and no bowel or bladder symptoms. Walking, sneezing,
defecation, and laughing worsened the pain.
Physical examination revealed no gross motor or reflex changes,
but there was decreased pin-prick sensation on the sole of the left
foot. The radiographs that had been made at the other institution
were not available for our review. Additional radiographs of the
entire spine were made with lead-shielding of the gonadal area and
were reported as normal. Magnetic resonance imaging revealed a cystic
lesion extending from the caudal end of the second sacral segment
to approximately the fourth sacral segment. The lesion was hypointense
on T1-weighted images and hyperintense on T2-weighted images, consistent
with a cyst. The lesion was explored operatively and was removed
without any complications; it was subsequently identified as an
arachnoid cyst.
At the two-year follow-up examination, the patient was asymptomatic.
Case 2. A thirteen-year-old girl presented with a ten-month history
of recurrent low-back pain following a blow to the lower back while
jumping on a trampoline. Radiographs of the thoracolumbar spine,
made at a different institution after the accident, were reported
as normal. These radiographs were not available for our review initially.
The pain initially resolved after a short course of physical therapy
but then recurred with increased physical activity. The patient
did not have any bowel or bladder dysfunction or tingling in the
lower extremities. The only remarkable finding on physical examination
was mild tenderness in the midline of the lower back. Sensation,
strength, and reflexes in the lower extremities were normal. Radiographs
of the entire spine were repeated with shielding of the pelvis (Fig. 1-A) and were
interpreted as normal. The radiographs that had been made initially
without lead-shielding were subsequently reviewed by us; they showed
an expansile lesion in the spinal canal. Magnetic resonance imaging
demonstrated a 5.6 1.7 12-mm cystic lesion widening the spinal
canal of the sacrum, with scalloping of the ventral and dorsal aspects
of the bone (Figs. 1-B and 1-C). At surgery, an intradural arachnoid
cyst was removed without complications.
At the two-year follow-up examination, the patient reported no
pain or discomfort in the lower back.
According to a number of studies, the prevalence of back pain in
children is between 11.5% and 36%, with less than
2% of children being seen for medical attention1,2. Back pain can be secondary to
trauma, infection, spondylolisthesis, disc degeneration, herniation
of the intervertebral disc, or tumor1-11.
Turner et al.2 reported on sixty-one
children who presented with low-back pain. Approximately 50% had
a serious spinal disease. All sixty-one patients had radiographs
of the spine, which provided the diagnosis for twenty-three. The
fact that a high percentage of the patients had a serious spinal
abnormality supports the need for optimal radiographic visualization
of the symptomatic area.
Because children are not always specific in localizing the area of
concern, a thorough history and clinical examination are imperative1,9,12. The patient can sometimes describe
the type and location of the symptoms, which can help the physician
to determine the cause of the pain. One of our patients (Case 1)
had decreased pin-prick sensation, which alerted us to the possibility
of a cause that was more serious than mechanical low-back pain. If
appropriate evaluation warrants radiographs of the pelvic or sacral
area, these tests should be performed without lead-shielding by
competent technicians using state-of-the-art equipment, to reduce
the chances of repeat radiation exposure. Additional diagnostic
studies, such as magnetic resonance imaging, may be needed to establish
the diagnosis5,12-14.
In the two cases presented in this report, radiographs of the thoracolumbar
spine had been made before the children were seen at our institution
because of low-back pain. However, because of parental concerns
about radiation exposure to the gonads, the pelvis was shielded
and the sacrum was not visualized. The radiographs were considered
normal, as no abnormalities were seen. When the pain persisted,
magnetic resonance imaging of the entire spine was performed, demonstrating
the lesion in the sacrum.
Spinal meningeal cysts can be classified into three major categories:
type I—extradural cysts without spinal nerve-root fibers,
type II—extradural cysts with spinal nerve-root fibers, and
type III—intradural cysts15.
These cysts occur more commonly in the thoracic region, but in both
of our patients the lesion was located in the sacrum. Intradural
arachnoid cysts are believed to be the result of an alteration of
the arachnoid trabeculae16. The
mechanism that allows the cyst to communicate with the subarachnoid
space is unclear, but it appears that this communication is needed
in order for the cyst to enlarge and become symptomatic16. Rabb et al. reported on eleven
patients who were diagnosed with a spinal arachnoid cyst; three
of the cysts were located in the lumbosacral region16. The clinical findings included
radicular pain, progressive weakness, increasing scoliosis, worsening
spasticity, and recurrent urinary tract infection. Eight of the
eleven patients had excision and/or fenestration of the
cyst wall. Two patients had a shunt tube placed in the cyst, which
allowed the fluid to drain into the pleural cavity. In all eleven
patients, the symptoms had decreased or had stopped progressing16. Our two patients had excision of
the cyst, and, at the two-year follow-up examination, had remained
asymptomatic.
We believe that the evaluation of low-back pain in a child should
include a detailed history and a careful physical examination prior
to any diagnostic studies. Lead-shielding to protect the gonads
from ionizing radiation should not be used for the initial radiographs
of the spine because it may obscure a lesion located in the sacrum
or the pelvis.