Neurnrodiolngy
Neuroradiology 13, 45-49 (1977)
@ by Springer-Verlag 1977
Computerized Tomographyand Encephalography* G. Ruggiero, L. Sabattini, and G. Nuzzo Department of Neuroradiology, Ospedale Bellaria, Bologna, Italy
Summary. This preliminary paper compares encephalography and computed tomography as regards the duration of the examinations, the technical difficulties and their diagnostic values. Some examples are reported to demonstrate the complementary importance of the two techniques.
Key words: Computed tomography - Pneumoencephalography.
Since January 1975, 2477 computed tomographies (CT) and 718 encephalographies have been performed in our department. The aim of the present work is to compare these two methods on the basis of technique and pathology.
Technique The time required, the difficulty and the accuracy will be discussed. Is CT a shorter procedure than encephalography? Not in our department where a CT examination without contrast enhancement lasts approximately 30 min. Our apparatus is an EMI scanner (160 x 160 matrix). This duration could be shortened, but not significantly, by using more modem and faster machines. On the other hand special projections, which have to be decided during the examination and vary from case to case, are often necessary for both CT and encephalography. * Presented at the 5th Congress of the European Society of Neuroradiology, Geilo, Norway, September 1975. The section of the paper concerning the examination of the temporal horns will be published separately.
These projections, which involve positioning of the patient, photography and print-out, prolong the examination. Finally when contrast enhancement is necessary, which happens very often, the examination can last twice as long even though one can inject the contrast medium while another patient is being examined. The duration of CT examination is even longer if one wants to follow up the contrast fixation with late CT controls [ 1]. All these factors explain why it is not unusual that in some cases CT can last more than one hour. Anaesthesia may also increase the duration of the CT. General anaesthesia or neuroleptoanalgesia are often necessary for both encephalography and CT, perhaps more often for CT than encephalography, since for the latter the patient must theoretically remain motionless only for the time during which the X-ray pictures are taken. With the exception of unusual cases, encephalography lasts about 20-30 min if performed by an expert in a well-equiped department. Is CT an easier procedure than encephalography? Yes, but CT is not an easy examination. As well as for encephalography, there are problems of centering for CT. One of the main difficulties is the exact assessment of the midline, especially for the anterior portion of the brain. For the posterior portion of the brain the problem is simplified by the visualization of the pineal body which on CT is more frequently and clearly visible than on the X-ray films. The lateral ventricles often appear asymmetrical and deformed on CT even in normal cases while this does not happen wi,th encephalography (Fig. 1). The reason is that even the smallest inclination of the head along its vertical and/ or longitudinal planes can produce oblique tomographic sections of the brain causing an apparent deformation. The same thing happens when cutting a brain with a knife. Talairach [10] has demonstrated that,
46
G. Ruggiero et al.: Computerized Tomography and Encephalography
Fig. 1. a-b CT shows apparent
asymmetry of the lateral ventricles due to a slight obliquity of the skull, which disappears e after modifying the position of the head b
c
Fig. 1.d-f encephalography proves that the ventricles are symmetrical Table 1. Visualizationof ventricular system and subarachnoid space in 100 cases of negative CT Ventricular system
Subarachnoid space
Frontal horns Occipital horns Ventricular bodies r.
81 42 86 17
Basal cisterns (Pentagone) Quadrigeminal c. Circumpeduncolar c.
Temporal horns ~ Third ventricle Aqueduct (uncertain) Fourth ventricle
Fig. 2. a cerebral infarct and b glioblastoma, the oedematous necrotic tissue of both having a similar aspect. The correct diagnosis is made on the appearance of the ventricular system which, in the case of tumor, is displaced contralaterally
1. 18 75 11 57
66 97 55 43
Cerebellopontine c . ( r" 1. Cisterna magna r. Sylvian f i s s u r e ~ l "
29 22 33 26
Convexity space
65
G. Ruggiero et al.: Computerized Tomography and Encephaiography
47
Fig. 3. a, b. Meningioma of the tuberculum sellae a CT with enhancement shows a tumor in suprasellar region probably displacing the third ventricle backward b encephalography demonstrates that the lesion is extracerebral
Fig, 4. a--e CT shows the thalamic tumor but it is difficult to define its relationship to the brain stem. Encephalography shows that the brain stem is not infiltrated
whenever there is need of precise anatomical information, the only reliable method is stereotaxy. Improvement in centering may be obtained with machines without a rubber head-cap, but, in our opinion, this will not significantly reduce the likelihood of getting such oblique sections of the brain. Indeed, slight obliquities are often present on encephalography, as well as on all kinds of radiological examinations, but on encephalography they do not alter the precise anatomical representation as much as on CT. The essential difference between the two examinations is that CT is only a tomographic procedure and can not benefit from the general view of the brain
offered by encephalography with non-tomographic pictures. Let us imagine an encephalogram made only of tomograms; we are positive that its interpretation would be much more difficult and very probably less precise than an examination which includes all the standard films. The brain parenchyma is not visible on encephalography as it is on CT, so the diagnosis is based on the aspect of the ventricular system and subarachnoid space, which is important also for CT. Fig. 2 shows an example of two cases of different - not to say opposite - lesions in which the parenchyma has a similar aspect and the differential diagnosis is based
48
G. Ruggiero et al.: Computerized Tomography and Encephalography
Fig. 5. a--d Unverified left temporoparietal hygroma. CT shows large cyst in the temporoparietal basal region, not revealed by encephalography, but clearly demonstrated on late radiographic controls e, d
mainly on the aspect of the ventricular system. The visualization of the structures containing CSF is very important also in CT. These structures are not equally visible on CT and encephaiography. Table 1 shows the percentage of correct visualization of different structures obtained in 100 cases of negative CT performed with the standard technique. It is obvious that with encephalography all these structures can be visualized very accurately in practically all cases. For the reasons explained above, structures which have an oblique direction within the skull or are very thin, such as the temporal horns, fourth ventricle and the aqueduct, are the most difficult to study by CT. As regards the posterior fossa, it is probable that further experience with more refined equipment, will improve the situation. This is not the case for the temporal region since the temporal horns and the cisterns of the sylvian fissure are visible with the standard technique only when they are dilated. For this reason we have proposed a special technique to study these structures which is described in another paper [9] and is based on Talairach's stereotaxic method.
Pathology Tumors, hydrocephalus, malformations and atrophies will be considered. CT is preferable to encephalography to localize tumors of the hemispheres for two reasons. 1. It can differentiate edema from the tumor itself. 2. The diagnostic possibilities of encephalography are often decreased because of poor filling or non-filling of the ventricular system, which can be eliminated only partially by the urea technique [6]. Non-filling or poor filling of the ventricular system is not so important for posterior fossa tumors where correct localization can usually be made from the appearance of the cisterns only. Multiple metastases can usually be diagnosed by encephalography when there is good filling of the ventricles [3]. However there is no doubt that CT has greatly simplified the problem [4, 5]. It is often, but not always, possible to diagnose the nature of a tumour by CT [2]. But we must say that, with the exception of epidermoid cysts [7], the nature
G. Ruggiero et al.: ComputerizedTomography and Encephalography of the tumour is difficult to assess with encephalography which relies on indirect signs. Encephalography is, in our opinion, still preferable for tumors of the base of the skull since it indicates much m o r e clearly the extracerebral location of the tumor from the appearance of the cisterns (Fig. 3). Encephalography can also in some cases be useful to localize intracerebral growths more precisely (Fig. 4). Cortical atrophy can be demonstrated easily by both m e t h o d s . CT may sometimes demonstrate better, or at least more easily, some porencephalic cavities, but these lesions are usually also well shown by an encephalography performect with a highly refined technique (Fig. 5). Dilatation of the ventricles can be easily shown by both methods but encephalography is by far more precise for clarifying the cause of the lesion. This is particularly true for aqueductal stenosis where encephalography usually gives, not only a good demonstration of the obstruction, but explains the pathogenesis of the lesion, whether neoplastic or inflammatory [5, 8]. The diagnosis of malformations (agenesis of the corpus callosum, cyst of the cavum Vergae and of the septum peUucidum, anencephalus, Arnold-Chiari malformation, etc.) is more precise with encephalography. However, since most of these lesions occur in children, it is better to start the investigation with CT in o r d e r to avoid a lumbar puncture. In doubtful cases we perform encephalography immediately after CT, thus avoiding a second anaesthesia. In children, especially newborn, anaesthesia is a much more traumatic procedure than encephalography itself. T o conclude, CT must not be considered as a substitute for encephalography, as some people are in-
49 clined to think, much too naively. W e feel, on the contrary, that, in many fields, the two techniques are complementary.
Re~erences 1. Hatam, A., Bergvall, V., Lewander, R., Larsson, S., Lind, M.: Contrast medium enhancement with time in computer tomography (differential diagnosis of intracranial lesions). Acta Radiol. (Suppl.) 346, 63 (1975) 2. Paxton, C. R., Ambrose, J.: The EMI-Scanner.A bref reviewof the first 650 patients. Brit. J. Radiol. 47, 530 (1974) 3. Ruggiero, G.: L'encrphalographie fractionnre. Paris: Masson 1957 4. Ruggiero, G., Sabattini, L.: T. A. C. neUemetastasi. Communication at the 9th "Corso Internazionale di Aggiornamento sul dolore e sulle metastasi". Conversano, May 1976 5. Ruggiero, G., Sabattini,L.: FilosofiadellaT. A. C. Communication at the "Congresso Primaverile della S.N.O.", Salerno, June 1976 6. Ruggiero, G., Dettori, P., Leighton, R., Pacifico, L.: Encephalographywith urea. Acta Radiol. 3, 161 (1965) 7. Ruggiero,G., Dilenge,D., David, M.: Tableau radiologiquedes kystes 6pidermoides intracrfiniens. Neurochirurgie 3, 276 (1957) 8. Ruggiero, G., Sabattini, L.: Computerized tomography and encephalography. Communication at the 6th Congress of the European Societyof Neuroradiology,Dijon, September 1976 9. Ruggiero, G., Sabattini, L., Nuzzo, G.: CT and encephalography. Comunication at the 5th Congress of the European Societyof Neuroradiology.Geilo, September 1975 10. Talairach, J., Szikla, G.: Atlas of stereotaxic anatomy of the telencephalon. Paris: Masson 1967 Received: September 29, 1976
Prof. Dr. G. Ruggiero Department of Neuroradiology Ospedale Bellaria Bologna, Italy
Neuroradiology 13, 45-49 (1977)
@ by Springer-Verlag 1977
Computerized Tomographyand Encephalography* G. Ruggiero, L. Sabattini, and G. Nuzzo Department of Neuroradiology, Ospedale Bellaria, Bologna, Italy
Summary. This preliminary paper compares encephalography and computed tomography as regards the duration of the examinations, the technical difficulties and their diagnostic values. Some examples are reported to demonstrate the complementary importance of the two techniques.
Key words: Computed tomography - Pneumoencephalography.
Since January 1975, 2477 computed tomographies (CT) and 718 encephalographies have been performed in our department. The aim of the present work is to compare these two methods on the basis of technique and pathology.
Technique The time required, the difficulty and the accuracy will be discussed. Is CT a shorter procedure than encephalography? Not in our department where a CT examination without contrast enhancement lasts approximately 30 min. Our apparatus is an EMI scanner (160 x 160 matrix). This duration could be shortened, but not significantly, by using more modem and faster machines. On the other hand special projections, which have to be decided during the examination and vary from case to case, are often necessary for both CT and encephalography. * Presented at the 5th Congress of the European Society of Neuroradiology, Geilo, Norway, September 1975. The section of the paper concerning the examination of the temporal horns will be published separately.
These projections, which involve positioning of the patient, photography and print-out, prolong the examination. Finally when contrast enhancement is necessary, which happens very often, the examination can last twice as long even though one can inject the contrast medium while another patient is being examined. The duration of CT examination is even longer if one wants to follow up the contrast fixation with late CT controls [ 1]. All these factors explain why it is not unusual that in some cases CT can last more than one hour. Anaesthesia may also increase the duration of the CT. General anaesthesia or neuroleptoanalgesia are often necessary for both encephalography and CT, perhaps more often for CT than encephalography, since for the latter the patient must theoretically remain motionless only for the time during which the X-ray pictures are taken. With the exception of unusual cases, encephalography lasts about 20-30 min if performed by an expert in a well-equiped department. Is CT an easier procedure than encephalography? Yes, but CT is not an easy examination. As well as for encephalography, there are problems of centering for CT. One of the main difficulties is the exact assessment of the midline, especially for the anterior portion of the brain. For the posterior portion of the brain the problem is simplified by the visualization of the pineal body which on CT is more frequently and clearly visible than on the X-ray films. The lateral ventricles often appear asymmetrical and deformed on CT even in normal cases while this does not happen wi,th encephalography (Fig. 1). The reason is that even the smallest inclination of the head along its vertical and/ or longitudinal planes can produce oblique tomographic sections of the brain causing an apparent deformation. The same thing happens when cutting a brain with a knife. Talairach [10] has demonstrated that,
46
G. Ruggiero et al.: Computerized Tomography and Encephalography
Fig. 1. a-b CT shows apparent
asymmetry of the lateral ventricles due to a slight obliquity of the skull, which disappears e after modifying the position of the head b
c
Fig. 1.d-f encephalography proves that the ventricles are symmetrical Table 1. Visualizationof ventricular system and subarachnoid space in 100 cases of negative CT Ventricular system
Subarachnoid space
Frontal horns Occipital horns Ventricular bodies r.
81 42 86 17
Basal cisterns (Pentagone) Quadrigeminal c. Circumpeduncolar c.
Temporal horns ~ Third ventricle Aqueduct (uncertain) Fourth ventricle
Fig. 2. a cerebral infarct and b glioblastoma, the oedematous necrotic tissue of both having a similar aspect. The correct diagnosis is made on the appearance of the ventricular system which, in the case of tumor, is displaced contralaterally
1. 18 75 11 57
66 97 55 43
Cerebellopontine c . ( r" 1. Cisterna magna r. Sylvian f i s s u r e ~ l "
29 22 33 26
Convexity space
65
G. Ruggiero et al.: Computerized Tomography and Encephaiography
47
Fig. 3. a, b. Meningioma of the tuberculum sellae a CT with enhancement shows a tumor in suprasellar region probably displacing the third ventricle backward b encephalography demonstrates that the lesion is extracerebral
Fig, 4. a--e CT shows the thalamic tumor but it is difficult to define its relationship to the brain stem. Encephalography shows that the brain stem is not infiltrated
whenever there is need of precise anatomical information, the only reliable method is stereotaxy. Improvement in centering may be obtained with machines without a rubber head-cap, but, in our opinion, this will not significantly reduce the likelihood of getting such oblique sections of the brain. Indeed, slight obliquities are often present on encephalography, as well as on all kinds of radiological examinations, but on encephalography they do not alter the precise anatomical representation as much as on CT. The essential difference between the two examinations is that CT is only a tomographic procedure and can not benefit from the general view of the brain
offered by encephalography with non-tomographic pictures. Let us imagine an encephalogram made only of tomograms; we are positive that its interpretation would be much more difficult and very probably less precise than an examination which includes all the standard films. The brain parenchyma is not visible on encephalography as it is on CT, so the diagnosis is based on the aspect of the ventricular system and subarachnoid space, which is important also for CT. Fig. 2 shows an example of two cases of different - not to say opposite - lesions in which the parenchyma has a similar aspect and the differential diagnosis is based
48
G. Ruggiero et al.: Computerized Tomography and Encephalography
Fig. 5. a--d Unverified left temporoparietal hygroma. CT shows large cyst in the temporoparietal basal region, not revealed by encephalography, but clearly demonstrated on late radiographic controls e, d
mainly on the aspect of the ventricular system. The visualization of the structures containing CSF is very important also in CT. These structures are not equally visible on CT and encephaiography. Table 1 shows the percentage of correct visualization of different structures obtained in 100 cases of negative CT performed with the standard technique. It is obvious that with encephalography all these structures can be visualized very accurately in practically all cases. For the reasons explained above, structures which have an oblique direction within the skull or are very thin, such as the temporal horns, fourth ventricle and the aqueduct, are the most difficult to study by CT. As regards the posterior fossa, it is probable that further experience with more refined equipment, will improve the situation. This is not the case for the temporal region since the temporal horns and the cisterns of the sylvian fissure are visible with the standard technique only when they are dilated. For this reason we have proposed a special technique to study these structures which is described in another paper [9] and is based on Talairach's stereotaxic method.
Pathology Tumors, hydrocephalus, malformations and atrophies will be considered. CT is preferable to encephalography to localize tumors of the hemispheres for two reasons. 1. It can differentiate edema from the tumor itself. 2. The diagnostic possibilities of encephalography are often decreased because of poor filling or non-filling of the ventricular system, which can be eliminated only partially by the urea technique [6]. Non-filling or poor filling of the ventricular system is not so important for posterior fossa tumors where correct localization can usually be made from the appearance of the cisterns only. Multiple metastases can usually be diagnosed by encephalography when there is good filling of the ventricles [3]. However there is no doubt that CT has greatly simplified the problem [4, 5]. It is often, but not always, possible to diagnose the nature of a tumour by CT [2]. But we must say that, with the exception of epidermoid cysts [7], the nature
G. Ruggiero et al.: ComputerizedTomography and Encephalography of the tumour is difficult to assess with encephalography which relies on indirect signs. Encephalography is, in our opinion, still preferable for tumors of the base of the skull since it indicates much m o r e clearly the extracerebral location of the tumor from the appearance of the cisterns (Fig. 3). Encephalography can also in some cases be useful to localize intracerebral growths more precisely (Fig. 4). Cortical atrophy can be demonstrated easily by both m e t h o d s . CT may sometimes demonstrate better, or at least more easily, some porencephalic cavities, but these lesions are usually also well shown by an encephalography performect with a highly refined technique (Fig. 5). Dilatation of the ventricles can be easily shown by both methods but encephalography is by far more precise for clarifying the cause of the lesion. This is particularly true for aqueductal stenosis where encephalography usually gives, not only a good demonstration of the obstruction, but explains the pathogenesis of the lesion, whether neoplastic or inflammatory [5, 8]. The diagnosis of malformations (agenesis of the corpus callosum, cyst of the cavum Vergae and of the septum peUucidum, anencephalus, Arnold-Chiari malformation, etc.) is more precise with encephalography. However, since most of these lesions occur in children, it is better to start the investigation with CT in o r d e r to avoid a lumbar puncture. In doubtful cases we perform encephalography immediately after CT, thus avoiding a second anaesthesia. In children, especially newborn, anaesthesia is a much more traumatic procedure than encephalography itself. T o conclude, CT must not be considered as a substitute for encephalography, as some people are in-
49 clined to think, much too naively. W e feel, on the contrary, that, in many fields, the two techniques are complementary.
Re~erences 1. Hatam, A., Bergvall, V., Lewander, R., Larsson, S., Lind, M.: Contrast medium enhancement with time in computer tomography (differential diagnosis of intracranial lesions). Acta Radiol. (Suppl.) 346, 63 (1975) 2. Paxton, C. R., Ambrose, J.: The EMI-Scanner.A bref reviewof the first 650 patients. Brit. J. Radiol. 47, 530 (1974) 3. Ruggiero, G.: L'encrphalographie fractionnre. Paris: Masson 1957 4. Ruggiero, G., Sabattini, L.: T. A. C. neUemetastasi. Communication at the 9th "Corso Internazionale di Aggiornamento sul dolore e sulle metastasi". Conversano, May 1976 5. Ruggiero, G., Sabattini,L.: FilosofiadellaT. A. C. Communication at the "Congresso Primaverile della S.N.O.", Salerno, June 1976 6. Ruggiero, G., Dettori, P., Leighton, R., Pacifico, L.: Encephalographywith urea. Acta Radiol. 3, 161 (1965) 7. Ruggiero,G., Dilenge,D., David, M.: Tableau radiologiquedes kystes 6pidermoides intracrfiniens. Neurochirurgie 3, 276 (1957) 8. Ruggiero, G., Sabattini, L.: Computerized tomography and encephalography. Communication at the 6th Congress of the European Societyof Neuroradiology,Dijon, September 1976 9. Ruggiero, G., Sabattini, L., Nuzzo, G.: CT and encephalography. Comunication at the 5th Congress of the European Societyof Neuroradiology.Geilo, September 1975 10. Talairach, J., Szikla, G.: Atlas of stereotaxic anatomy of the telencephalon. Paris: Masson 1967 Received: September 29, 1976
Prof. Dr. G. Ruggiero Department of Neuroradiology Ospedale Bellaria Bologna, Italy
