PEDIATRIC PUZZLER

A 1-year-old refuses to walk any longer:
Backing into the diagnosis

Ann Settgast, MD, Peter Melchert, MD, Deepak Kamat, MD, PhD, and Walter W. Tunnessen, Jr., MD

Monday morning back in the office always comes too soon, especially after you have been out of town for a few days at the annual conference of the American Academy of Pediatrics. The schedule is stacked; it would be appreciated if all encounters were for sore throats and well-child checks. You pick up the chart on your first patient: a 12-month-old with a chief complaint of refusing to walk for the past three weeks. You have a premonition that nothing here will be easy.

The infant seems comfortable and in no distress lying in Mother's lap, so you proceed with the history. Approximately one month ago, he was seen in an urgent care center for a fever of 102° F. No source of the fever was found, and it was attributed to a viral illness. Acetaminophen and adequate fluid intake were suggested.

Seven days ago, the infant was seen by one of your partners. The fever had disappeared, only to return again. More disturbing to the parents, however, was their son's irritability and lack of interest in playing. Whereas he previously walked, now he only crawled. And, Mother added, he had not had a bowel movement in four days. She believed that he had some abdominal discomfort, perhaps because of the constipation. The temperature at the time was normal and the physical examination, unremarkable.

Your partner ordered an abdominal radiograph; no abnormalities in bowel pattern or other problems were seen on the film except for evidence of constipation. A diagnosis of a "viral syndrome" was made and a stool softener was prescribed for the constipation. Urinalysis and urine culture were obtained to rule out urinary tract infection: Urinalysis was negative and culture subsequently showed no growth.

Today, the parents are back. Their son's refusal to walk is now their primary concern. Here is what they report: The boy began walking at 10 ¹/₂ months of age; about three weeks ago, he seemed more wobbly, after which he walked only with support. Next, he regressed to crawling only, and even that became tentative and slow. Now he refuses to sit upright; even in the tub, he prefers to lay down when bathed. And he is definitely more fussy and wants to be held.

Any falls or other possible trauma? The parents remember only that six weeks ago he climbed on an overturned laundry basket and fell to the floor rather hard; he did not appear to have any problems after the fall, however. Last week's complaints of fever and constipation have disappeared. His appetite is somewhat diminished; Mother thinks he may have lost weight.

There has been neither contact with an ill person nor recent travel. Birth history is unremarkable; growth and developmental milestones have been on target. He is not on medications, has no known allergies, and has not been hospitalized. The family history is significant for a cousin in whom a neuroblastoma was diagnosed at 3 years of age, and who died recently. No wonder the parents are concerned.

The youngster's vital signs include a temperature of 98.4° F; heart rate, 124/min; respirations, 32/min; and blood pressure, 102/72 mm Hg. Weight is 9.9 kg—a decrease of 1.1 kg since his 9-month well-child check. He seems comfortable reclined in his mother's lap, where the examination is carried out.

In considering a lower extremity problem, you save that part of the examination for last. Head, neck, chest, cardiac, and abdominal examinations are unremarkable. As you turn him over to inspect the back, you note that he cries when you flex him into a sitting position. You find no areas of bruising or tenderness on the back.

You return him to a recumbent position. There is no swelling of the joints or deformity of the extremities. No areas of tenderness or warmth are found but, when you attempt to check hip motion, he resists and cries in pain. He refuses to bear any weight on his legs and he will not crawl. Clearly, he prefers to remain recumbent. Other than isolated small bruises on the elbows, the rest of the examination is unremarkable.

No time to take a back seat

Without question, something is amiss—but what? Your first thought is accidental—or intentional—trauma. There was the fall six weeks ago, preceding the onset of symptoms, but his parents reported that he was fine for at least two weeks afterward. What about toxic synovitis of the hips? There was a viral illness one month ago; could that have been the precipitant? Osteomyelitis, septic arthritis, juvenile rheumatoid arthritis, intra-abdominal abscess, and even epidural abscess need to be considered. And, of course, with documented weight loss, our old nemesis, malignancy—particularly leukemia and neuroblastoma—needs to be considered.

You order a few laboratory tests to home in on the diagnosis. White blood cell count is 13 x 10³/mL, with a differential count of 50% neutrophils, 40% lymphocytes, and 10% monocytes. Hemoglobin level is 12.1 g/dL, but the platelet count is high at 636 x 10³/mL. The peripheral smear is read as normal. But—hold on!—the erythrocyte sedimentation rate is elevated at 60 mm/hr. Urinalysis is normal, as is the serum lactate dehydrogenase level at 254 U/L.

Radiographs of both lower extremities are performed. No evidence of fracture or a periosteal reaction is seen. Given the elevated platelet count and sedimentation rate, infection, inflammation, and, still, neuroblastoma need to be strongly considered.

Why does the youngster not want to sit? He prefers recumbency, and flexing the spine increases his irritability, as does passive range of motion of the hips. Could this be a problem in the spine? Anterior-posterior and lateral views of the thoracolumbar spine are ordered.

Betwixt and between

The radiologist, examining the spinal films, points to a loss of disk space at L4-5, without apparent erosion of the adjacent vertebral bodies. But you want to make certain that this problem is limited to the disk space—diskitis—and isn't something else, particularly malignancy or osteomyelitis. You obtain blood cultures and order a magnetic resonance imaging scan of the spine. The scan shows increased signal intensity and loss of disk height at the L4-5 space (see figure).

The vertebral bodies appear intact, and there are no masses to be seen in the spinal canal or in the paraspinal area. Blood culture shows no growth. Diagnosis? Diskitis.

Clues, then discovery

Although diskitis is relatively benign and often self-limiting, it can pose a diagnostic dilemma. The exact incidence of the disease is unknown but believed to be quite low—perhaps one or two cases for every 30,000 visits to a pediatrician.¹ Most cases present in infancy and the toddler years, at a mean age of 2.8 years.²

Onset of the problem tends to be gradual, with symptoms present for days or weeks before the child is brought for medical attention. Younger children localize the discomfort poorly and tend be irritable and reluctant to walk or bear weight; older children tend to complain of back pain. Abdominal complaints are common, particularly anorexia, vomiting, pain, and, as this child had, constipation. Although affected children often have a low-grade fever, they do not look ill.²

Tenderness over the lower back or paraspinous muscle spasm may be found on examination. More often, extension and flexion of the hips cause pain. Key to remember is that apparent hip problems may be referred from the spine. The course of events in diskitis—gradual refusal to walk, then to bear weight, and then to crawl—should direct us to the problem. The child's position of comfort, reclining, is an important piece of information to be obtained from the physical exam.

Routine laboratory studies are not much help in localizing the problem. The WBC count may be normal or slightly elevated; the ESR may be elevated but is usually less than 60 mm/hr.^2,3 Blood culture is almost always negative; positive results appear to reflect contamination. If you suspect diskitis, obtain plain anteroposterior and lateral radiographs of the spine. In most children with diskitis, those films demonstrate loss of disk space height unless they were taken very early in the course. Some erosion of adjacent vertebral end plates is usually present.² Normal lumbar lordosis may be lost or even reversed. Additional imaging studies, particularly MRI, should be performed only if the presentation or the radiographic findings are uncharacteristic of diskitis.

The disorder that must be distinguished from diskitis is vertebral osteomyelits. Children who have this infection are generally older: Their mean age at presentation is 7.5 years, compared with 2.8 years for children with diskitis.² They also tend to have a more rapid onset of symptoms and a higher fever and to appear ill, and are more likely to have an elevated WBC count and a higher ESR. MRI would be important to pick up vertebral body involvement, and a purified protein derivative test is useful—in either disorder—to ensure that tuberculosis of the disk space or vertebral body is not a possibility. Paraspinous and intraspinal tumors are also included in the differential diagnosis of a back problem in a child.

Is diskitis a pyogenic infection? That debate continues. Blood cultures are almost always sterile and these children recover without antibiotic therapy. Retrospective reviews have reported that antibiotics do not appear to change the natural course^1,3; on the other hand, other investigators have demonstrated significantly faster recovery and a lower rate of relapse when children are treated with an antibiotic.⁴ Keep your pulse on the literature. . . .

As for how the history unfolds, diskitis follows quite a classic course, particularly in infants and young children. A child who progresses from difficulty walking to reluctance to bear weight, then refuses to crawl, and, last, shows a preference for a recumbent position should raise our antennae to this specific problem—or, at least, to a problem with the back generally. Work with the clues; then step back and piece together what you've found on the history and physical exam!

REFERENCES

1. Cushing AH: Diskitis in children. Clin Infect Dis 1993;17:1

2. Fernandez M, Carrol CL, Baker CJ: Discitis and vertebral osteomyelitis: An 18-year review. Pediatrics 2000; 105:1299

3. Crawford AH, Kucharzyk DW, Ruda R, et al: Diskitis in children. Clin Orthop May 1991;(266):70

4. Ring D, Johnston CE 2nd, Wenger DR: Pyogenic infectious spondylitis in children: The convergence of discitis and vertebral osteomyelitis. J Pediatr Orthop 1995; 15:652

DRS. SETTGAST and MELCHERT are medicine/ pediatrics residents and DR. KAMAT is director of the medicine/pediatrics residency program and a staff physician, all at the University of Minnesota.

DR. TUNNESSEN, who, until his death last year, served as section editor for Pediatric Puzzler for the more than 17 years that it has appeared here, was senior vice president of the American Board of Pediatrics, Chapel Hill, N.C., and a member of the Contemporary Pediatrics editorial board. Before his death, he was named the recipient of the 2002 Joseph W. St. Geme, Jr., Leadership Award.

Acknowledging a change of leadership

The editors of Contemporary Pediatrics are pleased to announce that, beginning with the March 2002 issue, George K. Siberry, MD, MPH, assumes editorial leadership of Pediatric Puzzler. Dr. Siberry completed his pediatric residency and chief residency at Johns Hopkins University School of Medicine. For three years, he served on the faculty in the department of pediatrics at Thomas Jefferson University, returning to Johns Hopkins in 2000 to begin a fellowship in pediatric infectious diseases.

Dr. Siberry is an academic pediatrician with a deep and intense interest in clinical evaluation and management. Capping a long list of awards and honors for clinical acumen and teaching, he received the Harriet Lane House Staff Fellow Appreciation Award in 2001. Dr. Siberry also has a longstanding interest in international health, and has participated in studies in India and Haiti. He served as co-editor of the 15th edition of The Harriet Lane Handbook and has published original research articles, reviews, and book chapters.

Walter W. Tunnessen, MD, inspired Pediatric Puzzler as its editor for 17 years until his death in November. When we set out to select a successor to Dr. Tunnessen, we were aware that it must be someone who finds the same joy in the challenge of clinical care as he did and the same enthusiasm for communicating discovery that he had. I am confident that, with Dr. Siberry as editor, the Puzzler will remain the favorite of so many readers of Contemporary Pediatrics.

Julia A. McMillan, MD

A 1-year-old who refuses to walk any longer : Backing into the diagnosis.

Contemporary Pediatrics

2002;2:32.