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The nasopharyngeal soft tissue sign: A reappraisal
Clin.RadioL (1979) 30, 481-483
The Nasopharyngeal Soft Tissue Sign: A Reappraisal £, L. COOK and C. K. L. COOK
piagnostie X-ray Department, Wessex Neurological Centre, Southampton General Hospital An increase in the thickness of the soft tissues of the posterior nasopharyngeal wall has been described in patients with a fracture of the skull base (Andrew, 1978). Measurements of this soft tissue layer made in the same way, in Southampton, have shown a striking difference in the mean and in the normal range both-in adolescents and adults. The normal measurements overlap those found in patients with a fracture of the skull base and the sign is not therefore a reliable indication of the presence of such a fracture. MATERIAL AND METHODS The distance from the base of the skull to the posterior nasopharyngeal airway was measured according to the method of Andrew (1978) in 224 adolescent and adult patients attending the accident and emergency department at Southampton General Hospital. None of these patients had any clinical or radiological evidence of a fracture of the skull base (du Boulay, 1965; Walker et al., 1969; Taveras and Wood, 1976), and all were discharged from hospital following the X-ray examination. The first group of 100 patients attended consecutively during August 1978. The discrepancy between the measurements in these patients and those in Andrew's series (1978)was so striking that measurements were made in a second group of 124 similar patients attending consecutively during December 1978. During the same periods measurements were also made on 220 children aged 10 years and under; 138 during August and 82 in December. Fifteen normal patients, 10 children, two adolescents and three adults had a total of 19 previous lateral radiographs of the skull available for comparison. Measurements were made on these to estimate the individual variations over a period of time. During the same periods measurements were made on two children, one adolescent and three adult patients admitted with clinical and radiological evidence of a fracture of the skull base. Finally, as magnification factors might have been responsible for the observed differences in findings in Johannesburg and Southampton, a series of lateral Films using various techniques and apparatus were made of a dry skull to the base of which a 1.0 cm india rubber was attached to represent the soft tissues.
Fig. 1. The mean thickness and range of measurements of the nasopharyngeal soft tissues are shown in Fig. 2. Fig. 1 also includes the measurements in the six patients with fractures of the skull base. The differences between the measurements made in August and those in December are expressed !n Table 1. Andrews (1978) advises that the soft tissue sign should be interpreted with reserve in adolescents, but nevertheless found the mean measurement at this age to be less than 11 ram. In only one adolescent in whom the soft tissues measured 16ram did he find a measurement greater than his upper limit of normal of 15 mm. Eighty-three of the 115 patients aged 1 1 - 2 0 years in the present series, gave measurements of 16ram or more. Both in patients aged 11 15 years and those aged 16-20 years the mean measurements at 17.4 and 16.0mm respectively were greater than
thickness
Number of Patients
RESULTS AND DISCUSSION Age in years
The age distribution, together with the numbers in whom the measurement exceeded 15 mm is shown in 38
Fig. 1 - Age distribution of patients and numbers with a soft tissue thickness greater than 15 mm.
482
CLINICAL RADIOLOGY o Patients with fractures of the base e'f skull
30
o o
t
Soft Tissue 20 Thickness in rnms:means and range of measurements. 10
.
.
.
.
.
.....: ."-"t"" t ..... 15mms
.
o
Age in years
Fig. 2 - Means and range of measurements of soft tissue thickness. the thickness of 15 mm regarded as the upper limit of normal by Andrews (1978). Seventy-two per cent of adolescents gave measurements greater than this with no significant seasonal difference. Twenty-two patients in the combined adolescent group (11-20 years) gave measurements of 21mm or more, the greatest being 30mm in a boy aged 17 years. At these more extreme levels some seasonal difference was noted witll: 8% of adolescents giving such measurements in August against 33% in December. Furthermore, in many of the patients giving such measurements the line of the nasopharynx was an unbroken curve with no identifiable local prominence of the adenoidal pad. In adults there is a tendency for the soft tissue thickness to decrease with age. The smallest mean measurement at any age is 10.8 rnm in patients aged over 60 years. Even at this age individual measurements of 24 and 17ram respectively were recorded in men aged 65 and 84 years. Twenty-six per cent of all normal adults gave measurements greater than 15 nun and the mean measurements up to the age of 40 were very close to this figure. There was no significant seasonal variation.
The majority of children, apart from those under the age of one year, gave measurements greater than 15ram. Such figures were obtained in 105/128 (83%) in August and 65/74 (89%) in December. The corresponding percentages giving measurements greater than 20 mm were 22% in August and 38% in December. A factor to be noted is the difficulty in making the measurements in the youngest patients, using the points described, because of the different craniofacial proportions at this age. Most of the children giving the more extreme measurements showed an obvious local pad of adenoidal tissue but this was by no means always the case. Nineteen earlier examinations were compared with that of the survey. Four patients gave identical measurements over periods up to two years. Most of the others showed small variations of the order of few millimetres. Two patients however, a boy aged six and a man of 21 showed variations of 4 and 5 turn at two-year intervals and a four-year-old boy varied by 3 mm at two examinations only a week apart. The measurements in the six patients with fractures of the skull base are also included in Fig. 2. In two children and an adolescent the measurements were well within the normal range; in two of them below the mean for their particular age group. The nasopharyngeal soft tissue space measured 17mm in one adult which is also comfortably within the normal range. The two remaining adults gave measurements of 25 mm. This is greater than any other adult measured although two men aged 33 and 65 gave measurements of 24 ram. It is of interest to note that in one of these patients the measurement had fallen to 20 mm a week later tending to support the suggestion of Andrews (1978) that the sign might be invalidated by a lapse of time. With all variations in radiographic technique and equipment the 1.0 cm rubber attached to the dry skull was found to measure between 1.2 and 1.3 cm on the radiographs. The possible significance of magnification factors, in accounting for the differences between the individual measured by Andrews (1978) in Johannesburg and those in the present series, was therefore eliminated. It seems likely that the striking discrepancy between experience in Johannesburg and Southampton may represent differences in the frequency and
Table 1 - Nasopharyngealsoft tissue thickness greater than 15 m m
Children (<10 years) Adolescents (11-20 years) Adults (> 20 years)
August
December
Total
106/138 (74%) 49/64 (77%) 8/36 (22%)
66/82 (80%) 34/57 (67%) 20/73 (27%)
168/220 (76%) 83/115 (72%) 28/109 (26%)
THE
NASOPHARYNGEAL
SOFT
severity of upper respiratory tract infection, particularlY in children and adolescents. Andrews (personal communication) confirms that the Highveld where johannesburg is situated is recognised in South Africa as being one of the best areas in that country for those suffering from allergic asthma. There appear to be no obvious differences in the selection o f patients in the two groups although accurate comparison is not possible. The South African patients ~¢ere all of Caucasian origin. cONCLUSIONS Measurements of the thickness of the posterior nasopharyngeal soft tissues in the present group o f patients have indicated that previously quoted figures are not universally applicable. Both the normal range and the mean are considerably greater than
TISSUE
SIGN
A REAPPRAISAL
483
previously suggested. The value of such measurements in the diagnosis of a fracture of the skull base is therefore limited especially in children and adolescents. In adults the measurement is of some value but the upper limit of normal was found to be 2 4 m m .
REFERENCES
Andrews, W. K. (1978). The soft tissue sign: a new parameter in the diagnosis of the fractures of the base of the skull. Clinical Radiology, 29,443 -446. du Boulay, G. H. (1965). Principles of X-ray Diagnosis of the Skull, p. 321. Butterworths, London. Taveras, J. M. and Wood, E. H. (1976). Diagnostic Neuroradiology, Vol. 2, p. 1047. Williams and Wilkins, BaltiMore. Walker, A. E., Caverness, W. F. and Critchley, M. (1969). The Late Effects of Head Injury, p. 560. Charles Thomas, Springfield.
The Nasopharyngeal Soft Tissue Sign: A Reappraisal £, L. COOK and C. K. L. COOK
piagnostie X-ray Department, Wessex Neurological Centre, Southampton General Hospital An increase in the thickness of the soft tissues of the posterior nasopharyngeal wall has been described in patients with a fracture of the skull base (Andrew, 1978). Measurements of this soft tissue layer made in the same way, in Southampton, have shown a striking difference in the mean and in the normal range both-in adolescents and adults. The normal measurements overlap those found in patients with a fracture of the skull base and the sign is not therefore a reliable indication of the presence of such a fracture. MATERIAL AND METHODS The distance from the base of the skull to the posterior nasopharyngeal airway was measured according to the method of Andrew (1978) in 224 adolescent and adult patients attending the accident and emergency department at Southampton General Hospital. None of these patients had any clinical or radiological evidence of a fracture of the skull base (du Boulay, 1965; Walker et al., 1969; Taveras and Wood, 1976), and all were discharged from hospital following the X-ray examination. The first group of 100 patients attended consecutively during August 1978. The discrepancy between the measurements in these patients and those in Andrew's series (1978)was so striking that measurements were made in a second group of 124 similar patients attending consecutively during December 1978. During the same periods measurements were also made on 220 children aged 10 years and under; 138 during August and 82 in December. Fifteen normal patients, 10 children, two adolescents and three adults had a total of 19 previous lateral radiographs of the skull available for comparison. Measurements were made on these to estimate the individual variations over a period of time. During the same periods measurements were made on two children, one adolescent and three adult patients admitted with clinical and radiological evidence of a fracture of the skull base. Finally, as magnification factors might have been responsible for the observed differences in findings in Johannesburg and Southampton, a series of lateral Films using various techniques and apparatus were made of a dry skull to the base of which a 1.0 cm india rubber was attached to represent the soft tissues.
Fig. 1. The mean thickness and range of measurements of the nasopharyngeal soft tissues are shown in Fig. 2. Fig. 1 also includes the measurements in the six patients with fractures of the skull base. The differences between the measurements made in August and those in December are expressed !n Table 1. Andrews (1978) advises that the soft tissue sign should be interpreted with reserve in adolescents, but nevertheless found the mean measurement at this age to be less than 11 ram. In only one adolescent in whom the soft tissues measured 16ram did he find a measurement greater than his upper limit of normal of 15 mm. Eighty-three of the 115 patients aged 1 1 - 2 0 years in the present series, gave measurements of 16ram or more. Both in patients aged 11 15 years and those aged 16-20 years the mean measurements at 17.4 and 16.0mm respectively were greater than
thickness
Number of Patients
RESULTS AND DISCUSSION Age in years
The age distribution, together with the numbers in whom the measurement exceeded 15 mm is shown in 38
Fig. 1 - Age distribution of patients and numbers with a soft tissue thickness greater than 15 mm.
482
CLINICAL RADIOLOGY o Patients with fractures of the base e'f skull
30
o o
t
Soft Tissue 20 Thickness in rnms:means and range of measurements. 10
.
.
.
.
.
.....: ."-"t"" t ..... 15mms
.
o
Age in years
Fig. 2 - Means and range of measurements of soft tissue thickness. the thickness of 15 mm regarded as the upper limit of normal by Andrews (1978). Seventy-two per cent of adolescents gave measurements greater than this with no significant seasonal difference. Twenty-two patients in the combined adolescent group (11-20 years) gave measurements of 21mm or more, the greatest being 30mm in a boy aged 17 years. At these more extreme levels some seasonal difference was noted witll: 8% of adolescents giving such measurements in August against 33% in December. Furthermore, in many of the patients giving such measurements the line of the nasopharynx was an unbroken curve with no identifiable local prominence of the adenoidal pad. In adults there is a tendency for the soft tissue thickness to decrease with age. The smallest mean measurement at any age is 10.8 rnm in patients aged over 60 years. Even at this age individual measurements of 24 and 17ram respectively were recorded in men aged 65 and 84 years. Twenty-six per cent of all normal adults gave measurements greater than 15 nun and the mean measurements up to the age of 40 were very close to this figure. There was no significant seasonal variation.
The majority of children, apart from those under the age of one year, gave measurements greater than 15ram. Such figures were obtained in 105/128 (83%) in August and 65/74 (89%) in December. The corresponding percentages giving measurements greater than 20 mm were 22% in August and 38% in December. A factor to be noted is the difficulty in making the measurements in the youngest patients, using the points described, because of the different craniofacial proportions at this age. Most of the children giving the more extreme measurements showed an obvious local pad of adenoidal tissue but this was by no means always the case. Nineteen earlier examinations were compared with that of the survey. Four patients gave identical measurements over periods up to two years. Most of the others showed small variations of the order of few millimetres. Two patients however, a boy aged six and a man of 21 showed variations of 4 and 5 turn at two-year intervals and a four-year-old boy varied by 3 mm at two examinations only a week apart. The measurements in the six patients with fractures of the skull base are also included in Fig. 2. In two children and an adolescent the measurements were well within the normal range; in two of them below the mean for their particular age group. The nasopharyngeal soft tissue space measured 17mm in one adult which is also comfortably within the normal range. The two remaining adults gave measurements of 25 mm. This is greater than any other adult measured although two men aged 33 and 65 gave measurements of 24 ram. It is of interest to note that in one of these patients the measurement had fallen to 20 mm a week later tending to support the suggestion of Andrews (1978) that the sign might be invalidated by a lapse of time. With all variations in radiographic technique and equipment the 1.0 cm rubber attached to the dry skull was found to measure between 1.2 and 1.3 cm on the radiographs. The possible significance of magnification factors, in accounting for the differences between the individual measured by Andrews (1978) in Johannesburg and those in the present series, was therefore eliminated. It seems likely that the striking discrepancy between experience in Johannesburg and Southampton may represent differences in the frequency and
Table 1 - Nasopharyngealsoft tissue thickness greater than 15 m m
Children (<10 years) Adolescents (11-20 years) Adults (> 20 years)
August
December
Total
106/138 (74%) 49/64 (77%) 8/36 (22%)
66/82 (80%) 34/57 (67%) 20/73 (27%)
168/220 (76%) 83/115 (72%) 28/109 (26%)
THE
NASOPHARYNGEAL
SOFT
severity of upper respiratory tract infection, particularlY in children and adolescents. Andrews (personal communication) confirms that the Highveld where johannesburg is situated is recognised in South Africa as being one of the best areas in that country for those suffering from allergic asthma. There appear to be no obvious differences in the selection o f patients in the two groups although accurate comparison is not possible. The South African patients ~¢ere all of Caucasian origin. cONCLUSIONS Measurements of the thickness of the posterior nasopharyngeal soft tissues in the present group o f patients have indicated that previously quoted figures are not universally applicable. Both the normal range and the mean are considerably greater than
TISSUE
SIGN
A REAPPRAISAL
483
previously suggested. The value of such measurements in the diagnosis of a fracture of the skull base is therefore limited especially in children and adolescents. In adults the measurement is of some value but the upper limit of normal was found to be 2 4 m m .
REFERENCES
Andrews, W. K. (1978). The soft tissue sign: a new parameter in the diagnosis of the fractures of the base of the skull. Clinical Radiology, 29,443 -446. du Boulay, G. H. (1965). Principles of X-ray Diagnosis of the Skull, p. 321. Butterworths, London. Taveras, J. M. and Wood, E. H. (1976). Diagnostic Neuroradiology, Vol. 2, p. 1047. Williams and Wilkins, BaltiMore. Walker, A. E., Caverness, W. F. and Critchley, M. (1969). The Late Effects of Head Injury, p. 560. Charles Thomas, Springfield.