Routine radiography in early cholesteatomatous middle ear disease* By ROGER PARKER (London) Summary
THE surgery of chronic suppurative otitis media (C.S.O.M.) has altered radically in the last decade but its routine radiology has not. A new set of standard views is suggested, two of which are discussed in detail. Introduction
The diagnosis of cholesteatoma is made on history, inspection, and radiology. There is no doubt that inspection has been, by far, the principal means of diagnosis and that radiology has been the least important. Indeed, its value has tended to be limited to the few doubtful cases. Even then, the dangers of leaving a cholesteatoma unexplored are such that it is usually right to operate on suspicion, so that the place of radiology has been questioned altogether by many surgeons. At present, the type of surgery available is very varied, elaborate, lengthy and often staged. It is of help to the surgeon and to the patient to know as much as possible what is involved, so as to turn an 'exploration' into a planned procedure. It is in view of this requirement amongst others that the place of radiology for C.S.O.M. should be reassessed. Standard radiography of the middle-ear cleft is still, for the most part, confined to views of the petrous bone that demonstrate the gross anatomy and pathology present. However, the rise and success of middle-ear surgery has highlighted the need for more detailed radiological information of this region. It has been this need which has made tomography, and even polytomography where it is available, the first line in assessing, radiologically, evidence of middle-ear disease. However, it should be noted that the average dose of irradiation delivered to the unprotected cornea during 'routine petrous tomography' is 10 r (Chin et al., 1970), 23 r (Dobrin et al., 1973), and that lens opacities have been reported in animals following a single dose of 15 r (Upton et al., 1953). When one also takes into account that the maximum permissible dose for radiation workers is 5 r per year, the need to protect the patient from unnecessary irradiation compels the clinician to use straight radiography wherever possible. For example, a fronto-occipital (Towne's) view *From a paper given at the Fiftieth Anniversary Meeting of the Visiting Association of Throat and Ear Surgeons of Great Britain, October 1973.
R. Parker gives an absorbed dose of only 260 mr (Rogers, 1969). Thus, it is important that all the simple standard views of the middle ear be known, as well as the potentially hazardous, more expensive tomographic methods. Mastoid X-ray-projections
For X-ray views of the middle-ear cleft and its neighbouring anatomical structures, Sutton (1969) in his large and well-known textbook on radiology, briefly notes most of the standard radiographs of the middle-ear cleft. He studies in detail three views for C.S.O.M. which pay attention to the attic, ossicles and lateral semicircular canal (L.S.C.C.) or 'key area', namely those structures eroded in the cholesteatomatous form of C.S.O.M. Petrous radiography is given in detail in Scott Brown (1971), but the author gives no preference which routine views should be used in attico-antral disease. A lucid but incomplete chapter on this 'key area' is found in Shambaugh (1967). However, in a complete book devoted to radio-otology by Portmann and Guillen (1967), for which the latter author is known for his per-orbital view of this region in question, the radiography of cholesteatomatous erosion is discussed, explained in anatomical and radiological detail; and routine standard X-ray films are suggested for this form of middle-ear cleft disease. Finally, to augment the information obtained from these published sources, the radiographic departments of all the London teaching hospitals were canvassed for their 'routine mastoid views' in C.S.O.M. (Table I). It TABLE I. ROUTINE 'MASTOID X-RAYS' AT LONDON TEACHING HOSPITALS, I973
Charing Cross The London The Middlesex
Lateral
Lateral Oblique
Stockholm A, B
Stockholm C
Towne SMV
?
Stenvers or C
••
Schuller
The Royal National T.N.E.
2O°
St. Bartholomew's
3°°
St. George's
Stockholm A
St. Thomas'
Schuller
Frontal
Tip
Stenvers
Stockholm C
Law
Stenvers
The Westminster
Law
Stenvers 152
,, ••
Petrous through orbits
University College Hospital
Axial
••
Other
Macrographs
Routine radiography in early middle-ear disease can be shown in texts on petrous radiography, that all these views, taken for C.S.O.M., are, unfortunately, a heritage of the pre-antibiotic era of acute middle-ear disease, poorly adapted to the present demand for views in chronic ear disease. For those who use straight tomography for the routine radiography of middle-ear disease, it should be pointed out that, for a region the length of the middle-ear cleft, for example from anterior tympanum to antrum and posterior mastoid cells, many X-ray cuts are necessary. This fact of expense, plus the possible hazard of excess irradiation, should encourage the use of a few informative standard views. Polytomography suffers from the same argument of possible unnecessary irradiation. Also this form of radiography requires very expensive equipment, which can only be found in exceedingly few radiology departments in this country. The purchase of such equipment should be justified by its use. Where its information in congenital malformations of the ear may be inestimable, its use in cholesteatomatous erosion is rarely justified. For successful reconstructive middle-ear surgery in C.S.O.M., simple radiography should be available. This must give early, and safe, accurate information about the disease process. Two standard couch views of the mastoid will, therefore, be described to assist this. Radiology of early cholesteatomatous erosion
Erosion of the middle ear from cholesteatoma in C.S.O.M. usually starts in the posterior attic, to extend into the aditus over the bony prominence of the L.S.C.C, and into the mastoid antrum beyond. The ossicles, in this region, may also be eroded; in particular, the long process of the incus and stapes superstructure. The disease process may also extend to other parts of the middle-ear cleft and even beyond the petrous bone itself. However, it is the early radiography of erosion that is required, namely in the outer attic wall (O.A.W.), antrum, ossicles and, later, the L.S.C.C, if more conservative, rather than obliterative, surgery is to be possible. If a radiograph is taken along the axis of the middle-ear cleft (Fig. ia), the various structures projecting from its walls are thrown into profile, while the ossicles rilling the tympanum are seen in the centre without superimposition of other structures. This axial projection is that described by Guillen (1955). If an oblique radiograph along this same axis is taken (Fig. ia), different parts of the same structures are seen projecting once again into the cleft. This radiographic projection, named Chausse III, was originally described for visualising petrous fractures (1939; 1943) and, in recent years, it has been used in the routine radiography of C.S.O.M. (Chausse, 1950; Portmann and Guillen, 1967), especially on the continent. Detailed study of Fig. ib explains these differences in relation to the O.A.W., ossicles and L.S.C.C, which are pinpointed by these two views. 153
R. Parker One projection complements the other by demonstrating, radiologically, the anatomical extent of the disease. In simple terms, Guillen's projection will show the earliest sign of erosion, loss of the posterior O.A.W. spur and GUILLEN
CHAUSSE
FIG.
ia.
A diagrammatic horizontal section through the right middle ear and neighbouring structures. The red and blue arrows indicate the X-ray paths for Guillen and Chausse III views respectively. The same colours are also seen on the lateral semi-circular canal (L.S.C.C.) medially, and outer attic wall (O.A.W.) laterally, where each coloured part refers to the appropriate X-ray path. FIG. ib. Coronal diagrams through the right middle ear, each relating to the X-ray path indicated. Each illustration represents the X-ray anatomy to be considered, O.A.W. laterally, ossicles centrally and L.S.C.C. medially. In the first of these two illustrations, the Chausse' III view throws into profile the anterior O.A.W. and posterior L.S.C.C; the second, that of Guillen, shows the opposite, posterior O.A.W. and anterior L.S.C.C.
incus erosion, and, later on, more extensive erosion, anterior O.A.W. and posterior L.S.C.C, will be shown in the Chausse III projection. The lower diagrams (Fig. ib) illustrate these basic structures to be considered on the X-ray films in these two projections. The ossicular shadow, also represented, 154
Routine radiography in early middle-ear disease is likewise altered if any degree of malleus or, in particular, incus destruction, has occurred. Erosion of the incus reduces the overall triangular density of the ossicular outline to that of a vertical rectangle. These 'key area' structures seen in both Guillen and Chausse III diagrams (Fig. ib), can now be interpreted in the full X-ray illustrations of these views (Figs. 2 and 3).
FIG. 2. Guillen X-ray diagram. Key to the structures seen in this view: 1. L.S.C.C.; 2. ossicles; 3. attic; 4. antrum; 5. E.A.M.; 6. head of mandible; 7. mastoid tip air cells; 8. orbital rim; 9. tegmen tympani.
The only other standard views that define this key area, O.A.W., aditus and antrum, are the Mayer projection (1926) and its modification by Owen (1951). However, these views are technically difficult to take and read, due to their inherent distortion. Also, should these radiographs be out of alignment, it is difficult to instruct the radiographer where the necessary corrections should be made. Finally, in these views, erosion of the L.S.C.C. is not seen, although clinically, this is a very important milestone in the pathology and treatment of this disease and a contra-indication for reconstructive surgery (Hammond, 1970). 155
R. Parker Radiographic technique
Equipment A skull table with cones and diaphragms should be used, in order to obtain the greatest definition in the resulting X-rays. The patient can be examined in either the erect or supine position.
FIG. 3. Chausse III X-ray diagram. Key as for Figure 2.
Technique To obtain the Guillen radiograph (Fig. 4), the patient is placed in the antero-posterior (A.P.) position with the radiological base line (R.B.L.) at 900 to the film. The head is rotated 10° towards the side being examined. The central ray passes from the outer canthus of the eye to the external auditory meatus (E.A.M.), with the centring point at the medial canthus of the eye, on the side being examined. This view passes along the axis of the middle-ear cleft (Fig. ia). For Chausse III, the patient remains in the same position, A.P., with the R.B.L. at 90° to the film (Fig. 5). The head is rotated io° away, however, from the side being examined. The X-ray tube is angled io° caudally, so that the central ray passes from the lateral edge of the eyebrow on the side being examined. This view passes obliquely along the axis of the middleear cleft (Fig. ia). Routine X-rays for C.S.O.M. Lateral oblique
The patient is placed with the skull in the true lateral position. The tube is angled 250 caudally and the central ray passes through the E.A.M. of the 156
Routine radiography in early middle-ear disease side being examined. This view is taken to provide anatomical information of the operative field for the surgeon. He should know the gross anatomy and limits of the petro-mastoid block, namely, the posterior and middle cranial fossae.
GUILLEN
FIG. 4. Guillen X-ray position.
CHAUSSE
FIG. 5. Chausse III X-ray position.
Towne's view (half-axial) A coned view of the petrous temporal bones must be taken in order to provide a bilateral picture, whereby the two ears may be compared. The routine Towne's projection is employed with the central ray passing through the mastoid process at the level of the E.A.M. Considerable antral enlargement from erosion can be seen in this radiograph. This view will also show gross petrous pathology, which might not be read in the Guillen or Chausse views, where in extensive disease they may lack any normal anatomical landmarks for reference. 157
R. Parker Guillen and Chausse views These views, already described, will define the extent of cholesteatomatous erosion, denning what disease is early, and possibly amenable to conservative and reconstructive surgery; or, what more extensive erosion has occurred, warning the surgeon that a more radical operation should be planned. These four radiographs are sufficient for routine screening in C.S.O.M. to show middle-ear cleft erosion. However, it is important to realize the part that further radiographic investigation can play, should these views be unrewarding in more complicated cases. Acknowledgements
I am indebted to Professor Michel Portmann, not only for his permission to reproduce the illustrations in Figure i, but also for the stimulus and encouragement he gave in promoting this paper. Likewise, I am grateful to Mr. E. E. Douek for his help in committing this work into a comprehensive article. The illustrations have been painstakingly produced by the Department of Photography and Medical Illustration, Guy's Hospital, without whose help this paper would be incomplete. Also, I record the helpful and practical advice of Patricia Hampson, Superintendent Radiographer, Guy's Hospital. REFERENCES CHAUSSE, C. (1939) British Journal of Radiology, 12, 536. (1943) Journal de Radiologie et d'Electrologie, 25, 209. (1950) Premiers Elements de Radio-Otologie. Jouve, Paris. CHIN, F. K., ANDERSON, W. B., and GILBERTSON, J. D. (1970) Radiology, 94, 623. DOBRIN, R., BECKER, M. H., and GENIESER, N. B. (1973) Radiology, 109, 201.
GUILLEN, G. (1955) Revue de Laryngologie, Otologie, Rhinologie, 76, 395. HAMMOND, V. T. (1970) Journal of Laryngology and Otology, 84, 33. MAYER, E. G. (1926) Radiology, 7, 306. OWEN, G. R. (1951) Transactions of the American Otological Society, 39, 189. PORTMANN, M., and GUILLEN, G. (1967) Radiodiagnostic en Otologie. Masson, Paris. ROGERS, R. T. (1969) British Journal of Radiology, 42, 511. SCOTT-BROWN (1971) Diseases of the Ear, Nose and Throat, 3rd ed. Eds. J. Ballantyne and J. Groves. Butterworths, London. SHAMBAUGH, G. E. (1967) Surgery of the Ear, 2nd ed. Saunders, Philadelphia. SUTTON, D. (1969) A Textbook of Radiology. Livingstone, Edinburgh and London. UPTON, A. C. CHRISTENBERRY, K. W., and FURTH, J. (1953) Archives of Ophthal-
mology, 49, 164. Hearing Research Group, Throat and Ear Department, Guy's Hospital, London S.E.i.
158
THE surgery of chronic suppurative otitis media (C.S.O.M.) has altered radically in the last decade but its routine radiology has not. A new set of standard views is suggested, two of which are discussed in detail. Introduction
The diagnosis of cholesteatoma is made on history, inspection, and radiology. There is no doubt that inspection has been, by far, the principal means of diagnosis and that radiology has been the least important. Indeed, its value has tended to be limited to the few doubtful cases. Even then, the dangers of leaving a cholesteatoma unexplored are such that it is usually right to operate on suspicion, so that the place of radiology has been questioned altogether by many surgeons. At present, the type of surgery available is very varied, elaborate, lengthy and often staged. It is of help to the surgeon and to the patient to know as much as possible what is involved, so as to turn an 'exploration' into a planned procedure. It is in view of this requirement amongst others that the place of radiology for C.S.O.M. should be reassessed. Standard radiography of the middle-ear cleft is still, for the most part, confined to views of the petrous bone that demonstrate the gross anatomy and pathology present. However, the rise and success of middle-ear surgery has highlighted the need for more detailed radiological information of this region. It has been this need which has made tomography, and even polytomography where it is available, the first line in assessing, radiologically, evidence of middle-ear disease. However, it should be noted that the average dose of irradiation delivered to the unprotected cornea during 'routine petrous tomography' is 10 r (Chin et al., 1970), 23 r (Dobrin et al., 1973), and that lens opacities have been reported in animals following a single dose of 15 r (Upton et al., 1953). When one also takes into account that the maximum permissible dose for radiation workers is 5 r per year, the need to protect the patient from unnecessary irradiation compels the clinician to use straight radiography wherever possible. For example, a fronto-occipital (Towne's) view *From a paper given at the Fiftieth Anniversary Meeting of the Visiting Association of Throat and Ear Surgeons of Great Britain, October 1973.
R. Parker gives an absorbed dose of only 260 mr (Rogers, 1969). Thus, it is important that all the simple standard views of the middle ear be known, as well as the potentially hazardous, more expensive tomographic methods. Mastoid X-ray-projections
For X-ray views of the middle-ear cleft and its neighbouring anatomical structures, Sutton (1969) in his large and well-known textbook on radiology, briefly notes most of the standard radiographs of the middle-ear cleft. He studies in detail three views for C.S.O.M. which pay attention to the attic, ossicles and lateral semicircular canal (L.S.C.C.) or 'key area', namely those structures eroded in the cholesteatomatous form of C.S.O.M. Petrous radiography is given in detail in Scott Brown (1971), but the author gives no preference which routine views should be used in attico-antral disease. A lucid but incomplete chapter on this 'key area' is found in Shambaugh (1967). However, in a complete book devoted to radio-otology by Portmann and Guillen (1967), for which the latter author is known for his per-orbital view of this region in question, the radiography of cholesteatomatous erosion is discussed, explained in anatomical and radiological detail; and routine standard X-ray films are suggested for this form of middle-ear cleft disease. Finally, to augment the information obtained from these published sources, the radiographic departments of all the London teaching hospitals were canvassed for their 'routine mastoid views' in C.S.O.M. (Table I). It TABLE I. ROUTINE 'MASTOID X-RAYS' AT LONDON TEACHING HOSPITALS, I973
Charing Cross The London The Middlesex
Lateral
Lateral Oblique
Stockholm A, B
Stockholm C
Towne SMV
?
Stenvers or C
••
Schuller
The Royal National T.N.E.
2O°
St. Bartholomew's
3°°
St. George's
Stockholm A
St. Thomas'
Schuller
Frontal
Tip
Stenvers
Stockholm C
Law
Stenvers
The Westminster
Law
Stenvers 152
,, ••
Petrous through orbits
University College Hospital
Axial
••
Other
Macrographs
Routine radiography in early middle-ear disease can be shown in texts on petrous radiography, that all these views, taken for C.S.O.M., are, unfortunately, a heritage of the pre-antibiotic era of acute middle-ear disease, poorly adapted to the present demand for views in chronic ear disease. For those who use straight tomography for the routine radiography of middle-ear disease, it should be pointed out that, for a region the length of the middle-ear cleft, for example from anterior tympanum to antrum and posterior mastoid cells, many X-ray cuts are necessary. This fact of expense, plus the possible hazard of excess irradiation, should encourage the use of a few informative standard views. Polytomography suffers from the same argument of possible unnecessary irradiation. Also this form of radiography requires very expensive equipment, which can only be found in exceedingly few radiology departments in this country. The purchase of such equipment should be justified by its use. Where its information in congenital malformations of the ear may be inestimable, its use in cholesteatomatous erosion is rarely justified. For successful reconstructive middle-ear surgery in C.S.O.M., simple radiography should be available. This must give early, and safe, accurate information about the disease process. Two standard couch views of the mastoid will, therefore, be described to assist this. Radiology of early cholesteatomatous erosion
Erosion of the middle ear from cholesteatoma in C.S.O.M. usually starts in the posterior attic, to extend into the aditus over the bony prominence of the L.S.C.C, and into the mastoid antrum beyond. The ossicles, in this region, may also be eroded; in particular, the long process of the incus and stapes superstructure. The disease process may also extend to other parts of the middle-ear cleft and even beyond the petrous bone itself. However, it is the early radiography of erosion that is required, namely in the outer attic wall (O.A.W.), antrum, ossicles and, later, the L.S.C.C, if more conservative, rather than obliterative, surgery is to be possible. If a radiograph is taken along the axis of the middle-ear cleft (Fig. ia), the various structures projecting from its walls are thrown into profile, while the ossicles rilling the tympanum are seen in the centre without superimposition of other structures. This axial projection is that described by Guillen (1955). If an oblique radiograph along this same axis is taken (Fig. ia), different parts of the same structures are seen projecting once again into the cleft. This radiographic projection, named Chausse III, was originally described for visualising petrous fractures (1939; 1943) and, in recent years, it has been used in the routine radiography of C.S.O.M. (Chausse, 1950; Portmann and Guillen, 1967), especially on the continent. Detailed study of Fig. ib explains these differences in relation to the O.A.W., ossicles and L.S.C.C, which are pinpointed by these two views. 153
R. Parker One projection complements the other by demonstrating, radiologically, the anatomical extent of the disease. In simple terms, Guillen's projection will show the earliest sign of erosion, loss of the posterior O.A.W. spur and GUILLEN
CHAUSSE
FIG.
ia.
A diagrammatic horizontal section through the right middle ear and neighbouring structures. The red and blue arrows indicate the X-ray paths for Guillen and Chausse III views respectively. The same colours are also seen on the lateral semi-circular canal (L.S.C.C.) medially, and outer attic wall (O.A.W.) laterally, where each coloured part refers to the appropriate X-ray path. FIG. ib. Coronal diagrams through the right middle ear, each relating to the X-ray path indicated. Each illustration represents the X-ray anatomy to be considered, O.A.W. laterally, ossicles centrally and L.S.C.C. medially. In the first of these two illustrations, the Chausse' III view throws into profile the anterior O.A.W. and posterior L.S.C.C; the second, that of Guillen, shows the opposite, posterior O.A.W. and anterior L.S.C.C.
incus erosion, and, later on, more extensive erosion, anterior O.A.W. and posterior L.S.C.C, will be shown in the Chausse III projection. The lower diagrams (Fig. ib) illustrate these basic structures to be considered on the X-ray films in these two projections. The ossicular shadow, also represented, 154
Routine radiography in early middle-ear disease is likewise altered if any degree of malleus or, in particular, incus destruction, has occurred. Erosion of the incus reduces the overall triangular density of the ossicular outline to that of a vertical rectangle. These 'key area' structures seen in both Guillen and Chausse III diagrams (Fig. ib), can now be interpreted in the full X-ray illustrations of these views (Figs. 2 and 3).
FIG. 2. Guillen X-ray diagram. Key to the structures seen in this view: 1. L.S.C.C.; 2. ossicles; 3. attic; 4. antrum; 5. E.A.M.; 6. head of mandible; 7. mastoid tip air cells; 8. orbital rim; 9. tegmen tympani.
The only other standard views that define this key area, O.A.W., aditus and antrum, are the Mayer projection (1926) and its modification by Owen (1951). However, these views are technically difficult to take and read, due to their inherent distortion. Also, should these radiographs be out of alignment, it is difficult to instruct the radiographer where the necessary corrections should be made. Finally, in these views, erosion of the L.S.C.C. is not seen, although clinically, this is a very important milestone in the pathology and treatment of this disease and a contra-indication for reconstructive surgery (Hammond, 1970). 155
R. Parker Radiographic technique
Equipment A skull table with cones and diaphragms should be used, in order to obtain the greatest definition in the resulting X-rays. The patient can be examined in either the erect or supine position.
FIG. 3. Chausse III X-ray diagram. Key as for Figure 2.
Technique To obtain the Guillen radiograph (Fig. 4), the patient is placed in the antero-posterior (A.P.) position with the radiological base line (R.B.L.) at 900 to the film. The head is rotated 10° towards the side being examined. The central ray passes from the outer canthus of the eye to the external auditory meatus (E.A.M.), with the centring point at the medial canthus of the eye, on the side being examined. This view passes along the axis of the middle-ear cleft (Fig. ia). For Chausse III, the patient remains in the same position, A.P., with the R.B.L. at 90° to the film (Fig. 5). The head is rotated io° away, however, from the side being examined. The X-ray tube is angled io° caudally, so that the central ray passes from the lateral edge of the eyebrow on the side being examined. This view passes obliquely along the axis of the middleear cleft (Fig. ia). Routine X-rays for C.S.O.M. Lateral oblique
The patient is placed with the skull in the true lateral position. The tube is angled 250 caudally and the central ray passes through the E.A.M. of the 156
Routine radiography in early middle-ear disease side being examined. This view is taken to provide anatomical information of the operative field for the surgeon. He should know the gross anatomy and limits of the petro-mastoid block, namely, the posterior and middle cranial fossae.
GUILLEN
FIG. 4. Guillen X-ray position.
CHAUSSE
FIG. 5. Chausse III X-ray position.
Towne's view (half-axial) A coned view of the petrous temporal bones must be taken in order to provide a bilateral picture, whereby the two ears may be compared. The routine Towne's projection is employed with the central ray passing through the mastoid process at the level of the E.A.M. Considerable antral enlargement from erosion can be seen in this radiograph. This view will also show gross petrous pathology, which might not be read in the Guillen or Chausse views, where in extensive disease they may lack any normal anatomical landmarks for reference. 157
R. Parker Guillen and Chausse views These views, already described, will define the extent of cholesteatomatous erosion, denning what disease is early, and possibly amenable to conservative and reconstructive surgery; or, what more extensive erosion has occurred, warning the surgeon that a more radical operation should be planned. These four radiographs are sufficient for routine screening in C.S.O.M. to show middle-ear cleft erosion. However, it is important to realize the part that further radiographic investigation can play, should these views be unrewarding in more complicated cases. Acknowledgements
I am indebted to Professor Michel Portmann, not only for his permission to reproduce the illustrations in Figure i, but also for the stimulus and encouragement he gave in promoting this paper. Likewise, I am grateful to Mr. E. E. Douek for his help in committing this work into a comprehensive article. The illustrations have been painstakingly produced by the Department of Photography and Medical Illustration, Guy's Hospital, without whose help this paper would be incomplete. Also, I record the helpful and practical advice of Patricia Hampson, Superintendent Radiographer, Guy's Hospital. REFERENCES CHAUSSE, C. (1939) British Journal of Radiology, 12, 536. (1943) Journal de Radiologie et d'Electrologie, 25, 209. (1950) Premiers Elements de Radio-Otologie. Jouve, Paris. CHIN, F. K., ANDERSON, W. B., and GILBERTSON, J. D. (1970) Radiology, 94, 623. DOBRIN, R., BECKER, M. H., and GENIESER, N. B. (1973) Radiology, 109, 201.
GUILLEN, G. (1955) Revue de Laryngologie, Otologie, Rhinologie, 76, 395. HAMMOND, V. T. (1970) Journal of Laryngology and Otology, 84, 33. MAYER, E. G. (1926) Radiology, 7, 306. OWEN, G. R. (1951) Transactions of the American Otological Society, 39, 189. PORTMANN, M., and GUILLEN, G. (1967) Radiodiagnostic en Otologie. Masson, Paris. ROGERS, R. T. (1969) British Journal of Radiology, 42, 511. SCOTT-BROWN (1971) Diseases of the Ear, Nose and Throat, 3rd ed. Eds. J. Ballantyne and J. Groves. Butterworths, London. SHAMBAUGH, G. E. (1967) Surgery of the Ear, 2nd ed. Saunders, Philadelphia. SUTTON, D. (1969) A Textbook of Radiology. Livingstone, Edinburgh and London. UPTON, A. C. CHRISTENBERRY, K. W., and FURTH, J. (1953) Archives of Ophthal-
mology, 49, 164. Hearing Research Group, Throat and Ear Department, Guy's Hospital, London S.E.i.
158
