The thoracic paraspinal shadow: A review of the appearances in pathological conditions

ClinicalRadiology(1984) 35, 215-221 © 1984 RoyalCollegeof Radiologists

000%9260/84/254215502.00

The Thoracic Paraspinal Shadow: A Review of the Appearances in Pathological Conditions H. H. LIEN, A. KOLBENSTVEDT and G. LUND

Departments of Diagnostic Radiology, The Norwegian Radium Hospital and Rikshospitalet, University Hospital, Oslo, Norway

Alterations of the thoracic paraspinal shadow may give valuable information about pathological conditions of the spine, the paraspinai soft tissues, pleura and lungs. The causes of a distorted paraspinal shadow are reviewed and the main conditions illustrated by 15 selected cases.

The paraspinal shadow is visible on conventional antero-posterior (AP) films of the thoracic spine, most frequently on the left side (Lachman, 1942; Brailsford, 1943; Garland, 1943; Millard, 1963; Witten et al., 1965; Gupta and Mohan, 1979; Lien and Kolbenstvedt, 1982). Its lateral border (the paraspinal line) represents the interface of paraspinal soft tissues and air-filled lung (Lachman, 1942). The appearances of the paraspinal shadow have been reported in normal conditions (Doyle et al., 1961; Gupta and Mohan, 1979; Lien and Kolbenstvedt, 1982). Alterations may be caused by pathological processes in adjacent regions, i.e. spine, paraspinal soft tissue, pleura and lung (Table 1). The purpose of the present report is to.review systematically the causes of paraspinal shadow abnormalities and to illustrate such conditions by selected cases.

Table 1 - Distortion of the thoracic paraspinai shadow

Spine Tumour Primary Secondary Infection Fracture Scheuermann'sdisease Osteophytes

Paraspinalsoft tissue Lymphaticsystem Primary tumour Secondarytumour Vascular system Aorta Unfolding Dilatation Rupture Azygosvein system- dilatation Nervous system Neurinoma Neurenteric cyst Gastrointestinalsystem Oesophagus - rupture Interstitium Fat deposition Oedema Emphysema Haematopoiesis

Pleura SPINAL DISEASE

The vertebral transverse diameter may be increased in disorders of the spine, such as tumour, infection, fractures and osteophytes. Adjacent soft-tissue extension may widen the paraspinal shadow and thereby add to the changes (Brailsford, 1943; Dalton and Schwartz, 1956; Norman, 1962; Millard, 1963). The border of the lesion towards the lung is sharp and often bulging.

Fluid Thickening- calcification Tumour Primary Secondary

Lung Consolidation Atelectasis Tumour Primary Secondary

Tumours

Infections

Spinal tumours may be primary or secondary (metastases), the latter group being the commoner. Paraspinal expansion is most often segmental (Norman, 1962) (Fig. 1), but more extensive widening may occur when multiple vertebrae are involved. Likely primary turnouts include plasmocytoma, lymphoma, osteoblastoma and sarcoma arising in Paget's disease. The vertebra plana caused by eosinophilic granuloma may be associated with paraspinal swelling (Norman, 1962).

Inflammatory disease responsible for unilateral or bilateral bulging of the paraspinal shadow includes tuberculosis and non-specific osteomyelitis. A narrowed disc-space (Fig. 2) has been considered typical for inflammatory as opposed to neoplastic disease (Brailsford, 1943; Norman, 1962). However, Schmorl and Junghanns (1971) have reported disc involvement in a malignant tumour involving a vertebral body; in a study of 150 patients comprising 50 cases each of tumour, tuberculosis and osteomyelitis, Paus (1973) found disc reduction in 40, 48 and 48 patients, respectively. He concluded that no radiological sign was pathognomonic

Correspondence to: Dr Hans Henrick Lien, Department of DiagnosticRadiology,The NorwegianRadiumHospital,Montebello, Oslo 3, Norway.

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paraspinal bulging, reduction in disc height and vertebral body abnormalities all occurred. He stressed that the clinical course and laboratory tests had to be taken into account. A known primary tumour may indicate the likely diagnosis in many cases, while biopsy may be necessary in others. Fractures A fractured vertebral body is often associated with a paravertebral haematoma. The paraspinal shadow will be fusiform in most cases (Fig. 3), but patients with ankylosing spondylitis may show a segmental bulge due to adhesions of paraspinal ligaments (Norman, 1962). Widening due to haematoma will usually disappear within a month due to resorption (Norman, 1962).

Fig. 1 - Metastasis from prostatic carcinoma. Bilateral segmental bulge of paraspinal shadow corresponding to metastasis of T l l

(arrows). for one or the other disease and no sign was always present. However, tumour was somewhat more probable if only a single vertebra was involved, if the pedicle was affected and if the disc height was retained. Inflammatory disease was likely if change of axis,

Fig. 3 - Fracture of a mid-thoracic vertebra (not visible on present AP film). H a e m a t o m a causing bilateral, fusiform paraspinal swelling.

Scheuermann's Disease Soft part swelling may cause a slight widening of the paraspinal shadow in infants and adolescents with juvenile kyphosis (Brailsford, 1943). The mid-thoracic region is most frequently involved. The thickening of the paravertebral tissues may extend above and below the bony changes (Fig. 4). Osteophytes (a)

(b)

Fig. 2 - Osteomyelitis of mid-thoracic spine. (a) A P film demonstrating bilateral paraspinal widening (arrows). (b) Lateral film: disc reduction, anterior erosion (arrow) and sclerosis of adjacent vertebrae.

Hypertrophic spurs may cause uniform lateral deflection of the pleura without local bulging (Dalton and Schwartz, 1965; Lien and Kolbenstvedt, 1982). Spurring is most common on the right side, due to aortic pulsations preventing osteophyte formation on the left side (Goldberg and Carter, 1978).

THE THORACICPARASPINALSHADOW

(a) (b) Fig, 4 - Scheuermann's disease in a 17-year-old female. (a) Slight bilateral swelling of paraspinal shadow (arrows), extending to the lower thoracic region on the left side, Thickening of left paraspinal line. (b) Irregularities of endplates in anterior third of two midthoracic vertebral bodies which are slightly wedged (arrows). Schmorl's nodes present anteriorly. Moderate increase of kyphosis.

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Fig. 5 - Malignant lymphoma. Enlarged, contrast-filled, paravertebral lymph nodes in lower thoracic region and at thoracolumbar junction. Lateral displacement of paraspinal lines (arrows) and diaphragmatic crura (arrowheads).

PARASPINAL SOFT-TISSUE DISEASE Lymphatic System Enlarged paravertebral lymph nodes may widen the paraspinal shadow (Dalton and Schwartz, 1956; Witten et al., 1965; G u p t a and Mohan, 1979; Efremidis et al., 1981). Involvement m a y be primary (Fig. 5) or secondary due to metastasis (Fig. 6). The masses in Hodgkin's disease are often fusiform, extending over many segments. In a series of 403 patients with Hodgkin's disease, Witten et al. (1965) reported paraspinal masses in 22. The left lower paradorsal region was most frequently involved. Paraspinal masses are often in continuity with retroperitoneal masses through the aortic hiatus. They may, therefore, also displace the diaphragmatic crura (Fig. 5).

Vascular System The descending aorta greatly affects the position of the paraspinal line. The normal aortic unfolding with increasing age makes the line run a m o r e lateral course (Gupta and Mohan, 1979). A wide paraspinal shadow may also be seen in cases of aortic aneurysm or dilatation, due to displacement of the pleural reflection laterally. A mirror image of the line will occur in right-sided descending aorta. Traumatic rupture of the aorta causes mediastinal haemorrhage which m a y extend into the paraspinal area, widening the paraspinal shadow on one or both sides (Sanborn et al., 1970). Peters and G a m s u (1980) 18

Fig. 6 - Metastasis from testicular tumour. Widening of left lower paraspinal shadow.

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(b)

(a)

Fig. 7 - Distortion of paraspinal shadow in 15-year-old male. Accidental finding during work-up for congenital heart disease. Abnormality showecl no change during 4 years and was considered to be a neurinoma. (a) AP tomogram. Paraspinal bulge on left side. (b) CT scan demonstrating paravertebral location of process. Shallow erosion of adjacent vertebra (arrow) (L +55, W 605).

reported displacement of the right paraspinal interface in eight out of 14 patients with this condition, whereas the left paraspinal shadow was abnormal in only five. The azygos vein is located on the anterior aspect of the spine and, therefore, usually does not affect the paraspinal line. The hemiazygos vein lies posterior to the descending aorta, but its position is usually too medial to influence the paraspinal line. However, a dilated or tortuous vein may extend laterally and posteriorly, bulging into the left lung (Castellino et al., 1968). Dilatation of these veins may occur in superior or inferior caval vein obstruction and in azygos continuation of the inferior vena cava, as well as in portal hypertension (Doyle et al., 1961). Widening of the left paraspinal shadow in the latter condition may also be due to fluid retention with mediastinal oedema (Doyle et al., 1961).

masses. The occurrence of vertebral anomalies may be helpful in the diagnosis.

Gastrointestinal System Rupture of the oesophagus may lead to distortion of the left paraspinal shadow (Heitzman, 1977).

Nervous System Neurogenic tumours have been held to be the most frequent localised masses distorting the paraspinal shadow (Madewell et al., 1973). They may arise from intraspinal structures, nerve roots, intercostal nerves and sympathetic trunks. The latter tumours lie in a more anterior position than the others and tend to be fusiform. Bony changes are frequent in neurogenic tumours, but may be small (Fig. 7) or even absent. Neurenteric cysts and meningocoele also should be considered when dealing with posterior mediastinal

(~)

(b)

Fig. 8 - Abnormal accumulation of fat in left lower paraspinal region. (a) AP film: fusiform swelling on the left (arrows). (b) CT scan. Paraspinal widening caused by fat (L -68, W 1000).

THE THORACIC PARASPINAL SHADOW

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al, paraspinal masses. T h e lower thoracic region is m o s t frequently involved ( H e i t z m a n , 1977).

PLEURAL DISEASE

Fluid and Thickening A pleural effusion posterior to the p u l m o n a r y ligament m a y simulate widening of the paraspinal

(a)

(b)

Fig. 9 - Free pleural fluid in patient with malignant testicular tumou~ (a) Supine position. Apparent widening of left paraspinal shadow with maximum at T8. (b) Left lateral position. Shift of free fluid. Normal paraspinal shadow.

Interstitium A b n o r m a l accumulation of fat, as seen during high-dose steroid therapy, Cushing's disease or advanced obesity, may widen the paraspinal shadow (Heitzman, 1977). T h e widening m a y be u n i f o r m (Fig. 8) or m o r e masslike (Streiter et al., 1982). M o s t often, o t h e r findings of thoracic lipomatosis suggest the diagnosis of paraspinal fatty infiltration. C o m p u t e d t o m o g r a p h y (CT) will usually confirm the diagnosis. Displacement of the p a r a v e r t e b r a l pleura m a y occur in mediastinal e m p h y s e m a (Schulman et al., 1982). E x t r a m e d u l l a r y h a e m a t o p o i e s i s m a y present as bilater-

(a)

(b) Fig. 10

Fig. 11

Fig. 10 - Pleural thickening and pulmonary fibrosis from old tuberculosis. Slight traction effect on widened paraspinal shadow (arrows) and diaphragm. Obscured paraspinal line between arrows. Fig. 11 - Linear pleural calcification corresponding to paraspinal line.

Fig. 12 - Mesothelioma. (a) AP film. Thickening of pleura in the paraspinal region (arrows). Paraspinal line not distinguishable from descending aorta. (b) CT scan. Involvement of paraspinal pleura adjacent to aorta explains why aortic contour cannot be distinguished from paraspinal line (L +48, W 500).

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shadow by displacing adjacent lung laterally in the supine patient. A shift of free fluid in erect or lateral positions discloses the normal paraspinal shadow (Fig. 9). Trackler and Brinker (1966) considered lateral displacement of the lung on supine antero-posterior films to be an early diagnostic indication of free pleural fluid. It collected in this region due to gravitation and was more often observed on the left than on the right side. The apparent widening is usually most marked at the level of the diaphragm owing to the inferior pulmonary ligament binding the lung closer to the mediastinum at the hilar level (Rabinowitz and Wolf, 1966). However, the greatest collection may occur at higher levels, causing a slight convex bulge towards the lung (Fig. 9). Pleural thickening and calcification are most often secondary to tuberculosis and may be located to the paraspinal reflection of the pleura (Figs 10, 1l). Tumours

Mesotheliomas are primary tumours arising from the cells lining the surface of the pleura. Most of the hemithorax may be affected and the paraspinal region is frequently involved (Fig. 12). Metastases are frequent, especially in patients suffering from breast carcinoma. The paravertebral pleura may be studded with small deposits, or infiltrated by lobulated masses (Fig. 13). Most patients with pleural tumour also have pleural fluid.

(a)

P U L M O N A R Y DISEASE Consolidation

A pulmonary density may obliterate the paraspinal line when located adjacent to it. Fibrosis may be

(b) Fig. 15 - Carcinoma of apical segment of left lower lobe. (a) A P tomogram. Distortion of paraspinal shadow. (b) CT scan. Paraspinal location of tumour. Vertebra and rib destruction (L - 7 5 , W 500).

associated with a pleural thickening, resulting in an obscured paraspinal line and a widened paraspinal shadow (Fig. 10). In some cases fibrosis may have an additional traction effect on the paraspinal soft tissues (Fig. 10). Fig. 13

Fig. 14

Fig. 13 - Metastases from breast carcinoma. Lobulated pleural masses in the left paraspinal region (arrows). Fig. 14 - Collapse of left lower lobe (arrows), obliterating paraspinal line. Occlusion of lower lobe bronchus (arrowhead) from squamous-cell carcinoma.

Atelectasis

Collapse of a lower lobe usually causes a triangular density with the base on the postero-medial aspect of the

THE THORACIC PARASPINAL SHADOW

diaphragm and the apex inferior to the hilum, thereby obliterating the paraspinal line (Fig. 14). When the attachment of the inferior pulmonary ligament to the diaphragm is incomplete, the entire lower lobe may collapse against the mediastinum. A paraspinal mass results, the true nature of which may be demonstrated by the presence of an air bronchogram. Tumour Primary and secondary neoplasms located medially and posteriorly may distort the paraspinal shadow. A solitary lesion with bone destruction may simulate a neurogenic tumour (Fig. 15). CONCLUSION The thoracic paraspinal shadow may be altered by pathological conditions of the spine, paraspinal soft tissues, pleura and lung. Knowledge of these main groups is important for a rational work-up of a distorted paraspinal shadow. REFERENCES

Brailsford, J. F. (1943). The radiographic postero-medial border of the lung, or the linear thoracic paraspinal shadow. Radiology, 41, 34-37. Castellino, R. A., Blank. N. & Adams, D. F. (1968). Dilated azygos and hemiazygos veins presenting as paravertebral intrathoracic masses. New England Journal of Medicine, 278, 1087-1091. Dalton, C. J. & Schwartz, S. S. (1956). Evaluation of the paraspinal line in roentgen examination of the thorax. Radiology, 66, 195-200. Doyle, F. H., Read, A. E. & Evans, K. T. (1961). The mediastinum in portal hypertension. Clinical Radiology, 12, 114-129. Efremidis, S. C., Dan, S. J., Cohen, B. A., Mitty, H. A. & Rabinowitz, J. G. (1981). Displaced paraspinal line: role of CT and lymphography. AmericanJournalofRoentgenology, 136,505-509. Garland, L. H. (1943). The postero-mesial pleural line. Radiology, 41, 29-33.

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Goldberg, R. P. & Carter, B. L. (1978). Absence of thoracic osteophytosis in the area adjacent to the aorta. Computed tomography demonstration. Journal of Computer Assisted Tomography, 2, 173-175. Gupta, S. K. & Mohan, V. (1979). The thoracic paraspinal line: further significance. Clinical Radiology, 30, 329-335. Heitzman, E. R. (1977). The mediastinum. Radiologic Correlations With Anatomy and Pathology, pp. 205-206. C. V. Mosby, St Louis. Lachman, E. (1942). A comparison of the posterior boundaries of lungs and pleura as demonstrated on the cadaver and on the roentgenogram of the living. Anatomical Record, 83, 521-542. Lien, H. H. & Kolbenstvedt, A. (1982). The thoracic paraspinal shadow: normal appearances. Clinical Radiology, 33, 31-35. Madewell, J. E., Sobonya, R. E. & Reed, J. C. (1973). Neurenteric cyst. RPC from the AFIP. Radiology, 109, 707-712. Millard, D. G. (1963). Displacement of the linear thoracic paraspinal shadow of Brailsford. An early sign in osteomyelitis of the thoracic spine. American Journal of Roentgenology, 90, 1231-1235. Norman, A. (1962). Segmental bulge of the linear thoracic paraspinal shadow (paravertebral line). An early sign of disease of the thoracic spine. Journal of Bone and Joint Surgery, 44A, 352-358. Paus, B. (1973). Tumour, tuberculosis and osteomyelitis of the spine. Differential diagnostic aspects. Acta Orthopaedica Scandinavica, 44, 372-382. Peters, D. R. & Gamsu, G. (1980). Displacement of the right paraspinous interface: a radiographic sign of acute traumatic rupture of the thoracic aorta. Radiology, 134, 599-603. Rabinowitz, J. G. & Wolf, B. S. (1966). Roentgen significance of the pulmonary ligament. Radiology, 87, 1013-1020. Sanborn, J. C., Heitzman, E. R. & Markarian, B. (1970). Traumatic rupture of the aorta. Roentgen-pathological correlations. Radiology, 95, 293-298. Schmorl, G. & Junghanns, H. (1971). TheHuman Spine in Health and Disease, p. 340. Grune & Stratton, New York, London. Schulman, A., Fataar, S., van der Spuy, J. W., Morton, P. C. G. & Crosier, J. H. (1982). Air in unusual places: some causes and ramifications of pneumomediastinum. Clinical Radiology, 33, 301-306. Streiter, M. L., Schneider, H. J. & Proto, A. V. (1982). Steroid-induced thoracic lipomatosis: paraspinal involvement. American Journal of Roentgenology, 139, 679-681. Trackler, R. T. & Brinker, R. A. (1966). Widening of the left paravertebral pleural line on supine chest roentgenograms in free pleural effusions. American Journal of" Roentgenology, 96, 1027-1034. Witten, R. M., Fayos, J. V. & Lampe, I. (1965). The dorsal paraspinal mass in Hodgkin's disease. American Journal of Roentgenology, 94, 947-951.