Fran Lowry

December 08, 2009

December 8, 2009 (Chicago, Illinois) — Retropharyngeal lymph nodes seen in magnetic resonance imaging (MRI) sleep studies in children with obstructive sleep apnea are normal and can be safely ignored, researchers reported here at the Radiological Society of North America 95th Scientific Assembly and Annual Meeting.

"The retropharyngeal lymph nodes are the least well described portion of Waldeyer's ring. They are not commonly talked about, and I've seen several cases where people have misinterpreted them as either recurrence of a tonsil or something pathologic," Lane Donnelly, MD, chief of radiology at the Cincinnati Children's Medical Center in Ohio, told Medscape Radiology.

Dr. Donnelly and Norma S. Costa, MD, also from the Cincinnati Children's Medical Center, decided to look at the frequency and appearance of retropharyngeal lymph nodes in children with and without obstructive sleep apnea.

Their hypothesis was that medial retropharyngeal lymph nodes appear more commonly than has been described, and that they also occur more often in children who have obstructive sleep apnea.

The investigators reviewed the axial and sagittal T2-weighted MRIs of 150 children with obstructive sleep apnea and 150 control subjects who were imaged for other indications. The mean age of the children with sleep apnea was 9.4 years; the mean age of the control subjects was 9.1 years.

The retropharyngeal lymph nodes were noted as high signal structures. They were designated as lateral if they were positioned just medial to the carotid sheath, and medial if they were located near the midline. The presence, size, and location of the retropharyngeal lymph nodes were evaluated.

The findings, which were presented by Dr. Costa, were similar in both groups of children.

Lateral retropharyngeal lymph nodes occurred in 137 of the children with obstructive sleep apnea (91%), and in 146 of the control subjects (97%). More than 98% were located at the level of the skull base (C2).

Medial retropharyngeal lymph nodes were less common; they were found in 23 of the children with obstructive sleep apnea (21%) and in 26 of the control subjects (17%). They were also more inferior in location; 79% were found at the C2 to C3 level.

"It turns out that these lymph nodes are actually common, and not any more common in obstructive sleep apnea than in the control kids," Dr. Donnelly told Medscape Radiology. "They should be considered completely normal. They haven't been talked about and most people don't know about them, but they are of no significance. When radiologists see one on an examination, they should recognize it for what it is — a normal anatomic structure, not a pathologic process."

Ines Boechat, MD, chair of the board of directors of the Society for Pediatric Radiology and professor of radiology and pediatrics at the David Geffen School of Medicine at the University of California, Los Angeles, told Medscape Radiology that the main concern upon finding lymph nodes is that one does not know whether they are benign or malignant.

Determining that these nodes should not be considered abnormal is a useful finding, she said.

"It is helpful for whoever is looking at the MRIs of the neck in children to realize that these retropharyngeal lymph nodes are normal, and that they are seen bilaterally and more frequently, particularly the medial group of lymph nodes, than previously thought," she said. "Therefore, they should not be alarmed."

Dr. Boechat added that it is important to remember that children are growing and constantly changing, and that many pediatric imaging studies are done by adult, not pediatric, radiologists.

"It's good to know the established parameters of normal in children. This is one of these observations."

Dr. Costa, Dr. Donnelly, and Dr. Boechat have reported no relevant financial relationships.

Radiological Society of North America (RSNA) 95th Scientific Assembly and Annual Meeting: Abstract VP31-03. Presented December 1, 2009.


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