Unilateral hyperlucent thorax on plain chest radiographs after neck dissection: importance of atrophy of the trapezius muscle.
OBJECTIVE
A hyperlucent thorax on plain chest radiography indicates a decrease in the radiographic density of the thorax, which can be caused by intra- or extrapulmonary diseases. The purpose of this study was to assess the prevalence and mechanisms that may be responsible for unilateral hyperlucency of the thorax after neck dissection and to determine if atrophy of the trapezius due to the transection of the accessory nerve is a cause of hyperlucent thorax.


METHODS
Differences in the radiographic density between the right and left lung were evaluated and correlated with transection of the accessory nerve in 21 patients who had had a radical or a modified neck dissection for a malignant tumor of the head and neck. Twenty-eight neck dissections were performed on these 21 patients (seven had a simultaneous bilateral neck dissection). In 14 of the 21 patients, the accessory nerve had been severed during the neck surgery. In six patients, mechanisms responsible for a hyperlucent thorax were investigated with follow-up thoracic CT scans.


RESULTS
In the radiographs, eight patients had a hyperlucent thorax on the side of the neck dissection. In all of these cases, the accessory nerve on the side of this neck dissection had been severed during a radical or a modified neck dissection. Prior to surgery, no such hyperlucency was noted. CT scans showed atrophy of the denervated trapezius muscle.


CONCLUSIONS
Our findings show that atrophy of the denervated trapezius muscle after neck dissection is a cause of unilateral hyperlucent thorax on plain chest radiographs. Therefore, this finding should be anticipated as a postoperative change in patients who have had this surgery.
Department of Radiology, Jichi Medical School, Tochigi-ken, Japan.
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H
Sugimoto
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T
Ohsawa
D000055:Accessory Nerve / Q000601:surgery; D000328:Adult; D001284:Atrophy; D005500:Follow-Up Studies; D006258:Head and Neck Neoplasms / Q000601:surgery*; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology; D037981:Neck Dissection; D011184:Postoperative Period; D013902:Radiography, Thoracic; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed