Clin. Radiol. (1978) 29,571---577 THE ROLE OF COMPUTERISED TOMOGRAPHY IN THE DIAGNOSIS AND MANAGEMENT OF INTRACRANIAL ABSCESS H. PRICE and A. DANZIGER
From the Department of Diagnostie Radiology, Johannesburg GeneraI Hospital, Johannesburg A retrospective study has been undertaken of patients with intracerebral abscess and subdural empyema. Computerised tomography (CT) offers a rapid, non-invasive mode of diagnosis with accurate localisation and assessment of multiplicity of lesions. We propose that early diagnosis and correctly timed surgical intervention has lessened the mortality rate. CT allows for easy follow-up of patients and has allowed us in one case, to treat an inaccessible abscess conservatively.
Computerised tomography (CT) is now recognised as a standard method of investigating intracranial disease and this is particulary true of the investigation of intracranial abscess. CT offers an accurate, non-invasive, rapid and easily repeated means of following the course of lesions and in our institution, has replaced other neuroradiological means o f investigating intracranial abscess. MATERIALS AND METHODS In the past year we have had 38 patients with cerebral abscess or subdural empyema out of a total of 3300 scans. Tables 1 and 2 represent the details o f the patients scanned and we have analysed them as far as sex, race, age, site o f lesion, clinical features, predisposing factors and follow-up. All the scans reviewed were on a 160 x 160 matrix. Iodinated contrast medium was used as a routine in all cases clinically suspected of having an abscess. Motion artefact was reduced by using patient movement correction (PMC), chin straps, intravenous sedation (mainly diazepam) and general anaesthesia if required. RESULTS Thirty-eight patients had intracranial abscesses and of these, 33 had intracerebral abscesses. The latter involved all the supratentorial areas. The remaining five patients had subdural empyemas. Trauma was the most important predisposing factor, accounting for 18 patients. Primary intracranial infection accounted for seven, sinus or ear infection for six and pneumonia for two patients. In four patients, no clinically obvious primary focus for infection could be found.
Twenty-nine of the patients were South African Bantu (Negro) and only nine were white. We suggest that the high incidence among the black population is due to the frequency of head trauma. Of the 29 black patients, 15 had trauma as a predisposing factor, whereas of the nine white patients, only three had a history of trauma. All except one of our patients were treated surgically by aspiration under direct vision. The only other neuroradiological procedure performed on these patients was plain skull radiography. Only three patients demonstrated gas in the abscess prior to surgery. The CT scan was positive in all cases and in only two patients, did we fail to demonstrate an abscess capsule. The mortality rate in our series was 26%.
DISCUSSION The CT appearances o f intracerebral abscess are areas of low density which indicate density measurements of cerebral oedema, associated with mass effect. We consider iodinated contrast medium injection mandatory and this demonstrates a rim which can be regular or irregular and vary in shape and thickness. Abscesses could be unilocular (Fig. la, b) or multilocular (Fig. 2a, b). In our series, all cases had abnormal CT scan appearances and to our knowledge, there were no false negative results. This agrees with the findings of other authors (New etal., t976; Lott etal., 1977). Two of our cases did not exhibit rim enhancement after intravenous iodinated contrast. The first patient was clinically diagnosed as a temporal abscess, but at the time of needling, no pus was aspirated. The CT features were of a small, high density lesion with surrounding oedema which was single and showed no significant enhancement after contrast medium.
Table 1 - Abscesses
Name
Age/sex
Race
Clinical feature
Predisposing factors
Site
Outcome
IZ
6/M
B
40/M
B
Trauma, scalp abscess subdural Post-trauma
BS
23/M
B
Left occipital abscess Right parietal abscess Left frontal
Well
ES
TS
20/M
B
Stupor, left dilated pupil Confused, pyrexlal fitting Headache, confused neck stiffness Pyrexial
Left frontal
Well
DK
30/M
B
Left pupil dilated, right facial
Left frontal
Died
AD
50/M
B
Left parietal
Well
SM
40/M
B
Left parietal
Well
JM
31/M
B
Right spastic hemiplegia Right hemiplegma aphasia Right hemiplegia
Left occipital
Died
UM JC
36/M 24/M
B W
Trauma, depressed fracture Trauma Fractured base
Left frontal Right temporal
Died Died
DM ST
7/M 40/M
B B
Trauma, subdural Depressed fracture
Left occipital Left parietal
Well Well
HG
60/M
W
Trauma
Right frontal
Died
CC GL RE
32/M 4/M 18/M
W W B
Post-trauma Shunted Postencephalus
Right occipital Right parietal Left frontal
Well Well Well
EM Mt,
5/t" 16/M
B B
Postencephalitis Postencephalitls
Well Well
MDK
6/M
W
Right frontal Left frontal (daughter cyst) Right thalamic
DV
35/M
B
Well
ZOM
44/M
W
Right frontoparietal Left temperoparietal
JR EK WZ
23/F 12/b
15/M
W B B
Encephalitis Frontal sinusitis Frontal sinusitis
Right frontal Left frontal Left frontal
Well Died Died
SL
5/M
B
Otmtis media
Right parietal
Well
GL PK
32/M 4/F
W B
Otitis Otitis
Well Well
LP
40/M
B
Left temporal (air) Left temperoparietal Right thalammc
AN
35/M
B
ED TM
50/M 70/M
B B
RS PM
35/M 47/M
W B
Comatosed Confused, pyrexial decreasing level of consciousness Confused, pyrexial Dense right hemiplegia stupor Confused, left hemlplegia, dysphasia Confused, left hemiplegia ttydrocephalus Right sided headache, right facial, hemiplegia Pyrexial, drowsy vomiting Right sided fits frontal headache Headache, vomiting neck stiffness Left hemiplegia, confused Coma, pyrexial, dilated left pupil right sided fits Confused, left hemiplegaa Right hemiplegia Right hemiplegia, decreased level of consciousness Left facial, left hemiplegia Confused, dysarthria Headache, contused Left hemiplegia, decreased sensation Confused, pyrexial neck stiffness Right facial hemiplegia Headache, chest pain tremor, left hemlplegia Confused, pyrexial Aphasia, abnormal rightsided movements
Trauma Post-trauma depressed fracture Trauma, fracture, intracerebral clot drained Post-trauma septic skull wound Post-trauma
Encephalitis Postencephalitis Encephalitis
Pneumonia Pneumonia
Well Well
Well
Died
Well
Unknown Unknown
Right frontal, right parietal Left frontal Right frontal
Well Well Well
Unknown Unknown
Right occipital Left parietal
Dxed Well
M, male; F, female; W, white; B, South African Bantu. Trauma accounted for 14 patients. Primary intracranial infection for seven, sinus or ear infection for five; two patients had pneumonia In four patients no clinlcaUy obvious primary focus was noted. One was postoperative. Nine patients were white (European) and the rest South African Bantu. Four were female.
573
COMPUTERISED TOMOGRAPHY Table 2 - Subdurat
-Name
empyemas
Age~sex
Race
Clinical features
Predisposing factors
Site
Outcome
AO
25/M
W
13/M
B
Fronto-ethmoiditis sinusitis Postoperative subdural
Left frontal subdural Frontal empyema
Well
PK SN WM
58/M 58/M
B B
Trauma Trauma
26/M
B
Subdural empyema Left frontal empyema Right temporal
Well Well
SM
Pyrexial stupor confused Headache, vomiting right sided fits, left dilated pupil Confused, drowsy Right hemiplegia, right fits Headache, ataxic obtunded
Trauma, base fracture, otitis media
M, male; F, female;W, white; B, South African Bantu (Negro). Trauma accounted for all but one of this group, who had sinusitis. All were male. Only one was white.
Fig. 1 - Cerebral abscess. In the precontrast scan (a), extensive area of low density displacing the ventricles in the left temporoparietal region. With contrast (b), there is typical rim enhancement of the capsule.
Fig. 2 - Multilocular abscess. (a) shows an extensive area of low density in the right parieto-occipital region with mass effect. After contrast (b), a multilocular abscess is demonstrated.
Well
Well
574
Fig. 3
CLINICAL RADIOLOGY
Multiple abscesses. Primary focus was in the lung.
Fig. 4 Developing abscess. (a) shows a small low density in the left temporal region. Seven days later, (b) an abscess cavity is demonstrated with air. This allowed for the correct timing of surgical intervention. The primary focus was in the ear.
We feel that the failure of demonstrating the typical capsule was due to the fact that at post-mortem, a solid-aspergilloma was found. The second patient was found to have a ruptured abscess. We feel that at the time of scanning the latter patient, the cavity had decompressed itself and, therefore, we did not demonstrate its capsule. It should be remembered that both antibiotics and corticosteroids can markedly decrease the contrast enhancement of the abscess capsule. Angiography and isotope scanning are positive in only 90% of patients with brain abscess (Beller et al., 1973). They do not indicate the exact nature, stage nor precise anatomical site o f the abscess. In contrast, CT is 100% positive, gives accurate localisation and determines the presence o f daughter cysts and abscesses at other sites (Fig. 3a, b). It allows for serial examinations at short intervals, to gauge the correct time for surgical intervention, i.e. in following the evolution of an abscess from a cerebritis to cavitation with capsule formation (Fig. 4a, b). The abscess capsule rim constitutes three layers: inner granulation layer, middle collagen layer and outer reactive glial layer. The capsule takes some time to develop, as the fibroblasts forming the collagen layer take time to be activated (Moore and Thomas, 1974). The timing o f the surgical intervention is important, as surgery prior to the developm e n t of a capsule is generally not advised. Surgery requires: (a) early and accurate identification o f the abscess capsule; (b) accurate anatomical localisation o f the abscess; (c) identification of multiple loculations and multiplicity o f lesions. These factors promote decreased surgical trauma and increased accuracy of treatment and are corn-
Fig. 5 - This shows the presence of a draining catheter and postoperative air in the abscess cavity. The surrounding cerebral oedema and mass effect are again present.
COMPUTERISED
TOMOGRAPHY
575
Fig. 6 - Resolving abscess. Six-year-old child with otitis media. A well-defined capsule in the left parietal region demonstrated with contrast in (a). There is surrounding cerebral oedema. (b) Follow-up scan two weeks postoperatively. Capsule no longer present, with some resolution in the amount of cerebral oedema. The mass effect is less prominent.
Fig. 7 - This seven-year-old boy with encephalitis demonstrates the abscess rim after contrast (a). The lack of surrounding oedema is due to the high doses of antibiotics. Follow-up (b) showed some resolution in the size. A further scan (c) five weeks later, shows complete resolution. pletely satisfied b y CT and not b y angiography and isotope scanning. All except one o f our patients were treated surgically b y aspiration under direct vision and our overall m o r t a l i t y rate was 26%. The mortality rate from cerebral abscess varies from 36 to 53% (Morgan et al., 1973; Carey et al., 1972). Therapeutic success has, in the past, b e e n hampered b y incorrect diagnosis, late diagnosis and poor localisation. CT offers a solution to all these problems. It is useful for frequent follow-up of patients with
576
CLINICAL RADIOLOGY treated cerebral abscess (Fig. 5). We have been able to follow the progress o f patients postsurgery, demonstrating a decrease in abscess size, a reduction in the amount of surrounding oedema and a decrease in the mass effect (Fig. 6a, b). We were able to follow the progress o f one patient (MDK) who had a surgically inaccessible abscess and who was treated conservatively with high doses of antibiotics. He made a good recovery and is now well (Fig. 7a,
b, c). SUBDURAL EMPYEMA A peripheral area o f low density with EMI number between 10 and 14 with an associated mass effect (Fig. 8) is seen. After the administration of iodinated contrast media, all demonstrated medial rim enhanceFig. 8 - Subdural empyema. Peripheral low density on the right with enhancement after contrast. The right lateral ment. The thickness o f the rim demonstrated varied somewhat, but we feel that the chronic type o f ventricle is attenuated. subdural empyema will demonstrate a thicker capsule. In our series, cerebral oedema was not the prominent feature it was with the intracerebral abscess. All, except one case, were associated with a history of trauma with the development of a subdural or intracerebral haematoma (Fig. 9). The other patient had a frontal sinusitis and subsequently developed a frontal empyema. All underwent surgical drainage and were discharged well. CT is of value in the postoperative follow-up of these patients (Fig. 9c). We had no mortality in this group.
Fig. 9 - Post-traumatic subdural empyema. Two low density areas in the left frontoparietal regions (a) which after intravenous contrast (b) demonstrates a loculated subdural empyema. Follow-up post-aspiration scan (c) shows resolution. Note the bony defect.
COMPUTERISED TOMOGRAPHY
577
cysts as well as the timing of surgical intervention. It is important to obtain good quality scans; general anaesthesia may be required. CT is very useful in following the progress of abscesses and in one of our cases, it allowed us to follow the complete resolution, a thalamic abscess managed conservatively.
REFERENCES Beller, A. J., Sahar, A. & Praiss, I. (1973). Brain abscess" review of 89 cases over a period of 30 years. Journal o/ Neurology, Neurosurgery and Psychiatry, 36,757 768. Carey, M. E., Chou, S. N. & French, L. A. (1972). Experience with brain abscesses. Journal of Neurosurgery, 36(1), 1-9. Lott, T., el Gammal, T., da Silva, R., ttank, D. & Reynolds, J. lqg. 10 Post-traumatic abscess. An intracerebral abscess (1977). Evaluation of brain and epidural abscesses by CT. with a depressed bony fragment lying within it. Radiology, 122, 376. Moore, G. A. & Thomas, L. M. (1974). Infections including abscesses of the brain, spinal cord, intraspinal and intracranial lesions. Surgical Annual, 6, 413-437. CONCLUSION Morgan, H., Wood, M. W. & Murphey, [. (1973). Experience We present a large series of intracerebral abscess with 88 consecutive cases of brain abscess. Journal o f Neurosurgery, 38,698-704. and subdural empyema, in which the mortality is 26%. This is an improvement on previously published New, P. F. J., Davis, K. R. & Ballantine, H. T. (1976). CT in cerebral abscess. Radiology, 121,641-646. results. We believe the mortality rate has decreased Zlmmerman, R. A., Patel, S. & Bilaniuk, L. T. (1976). Demonbecause CT scanning allows for early diagnosis, stratlon of purulent bacterial intracranial infections by CT. American Journal o f Radiology, 127, 155-165. accurate localisation and recognition o f any daughter
43
From the Department of Diagnostie Radiology, Johannesburg GeneraI Hospital, Johannesburg A retrospective study has been undertaken of patients with intracerebral abscess and subdural empyema. Computerised tomography (CT) offers a rapid, non-invasive mode of diagnosis with accurate localisation and assessment of multiplicity of lesions. We propose that early diagnosis and correctly timed surgical intervention has lessened the mortality rate. CT allows for easy follow-up of patients and has allowed us in one case, to treat an inaccessible abscess conservatively.
Computerised tomography (CT) is now recognised as a standard method of investigating intracranial disease and this is particulary true of the investigation of intracranial abscess. CT offers an accurate, non-invasive, rapid and easily repeated means of following the course of lesions and in our institution, has replaced other neuroradiological means o f investigating intracranial abscess. MATERIALS AND METHODS In the past year we have had 38 patients with cerebral abscess or subdural empyema out of a total of 3300 scans. Tables 1 and 2 represent the details o f the patients scanned and we have analysed them as far as sex, race, age, site o f lesion, clinical features, predisposing factors and follow-up. All the scans reviewed were on a 160 x 160 matrix. Iodinated contrast medium was used as a routine in all cases clinically suspected of having an abscess. Motion artefact was reduced by using patient movement correction (PMC), chin straps, intravenous sedation (mainly diazepam) and general anaesthesia if required. RESULTS Thirty-eight patients had intracranial abscesses and of these, 33 had intracerebral abscesses. The latter involved all the supratentorial areas. The remaining five patients had subdural empyemas. Trauma was the most important predisposing factor, accounting for 18 patients. Primary intracranial infection accounted for seven, sinus or ear infection for six and pneumonia for two patients. In four patients, no clinically obvious primary focus for infection could be found.
Twenty-nine of the patients were South African Bantu (Negro) and only nine were white. We suggest that the high incidence among the black population is due to the frequency of head trauma. Of the 29 black patients, 15 had trauma as a predisposing factor, whereas of the nine white patients, only three had a history of trauma. All except one of our patients were treated surgically by aspiration under direct vision. The only other neuroradiological procedure performed on these patients was plain skull radiography. Only three patients demonstrated gas in the abscess prior to surgery. The CT scan was positive in all cases and in only two patients, did we fail to demonstrate an abscess capsule. The mortality rate in our series was 26%.
DISCUSSION The CT appearances o f intracerebral abscess are areas of low density which indicate density measurements of cerebral oedema, associated with mass effect. We consider iodinated contrast medium injection mandatory and this demonstrates a rim which can be regular or irregular and vary in shape and thickness. Abscesses could be unilocular (Fig. la, b) or multilocular (Fig. 2a, b). In our series, all cases had abnormal CT scan appearances and to our knowledge, there were no false negative results. This agrees with the findings of other authors (New etal., t976; Lott etal., 1977). Two of our cases did not exhibit rim enhancement after intravenous iodinated contrast. The first patient was clinically diagnosed as a temporal abscess, but at the time of needling, no pus was aspirated. The CT features were of a small, high density lesion with surrounding oedema which was single and showed no significant enhancement after contrast medium.
Table 1 - Abscesses
Name
Age/sex
Race
Clinical feature
Predisposing factors
Site
Outcome
IZ
6/M
B
40/M
B
Trauma, scalp abscess subdural Post-trauma
BS
23/M
B
Left occipital abscess Right parietal abscess Left frontal
Well
ES
TS
20/M
B
Stupor, left dilated pupil Confused, pyrexlal fitting Headache, confused neck stiffness Pyrexial
Left frontal
Well
DK
30/M
B
Left pupil dilated, right facial
Left frontal
Died
AD
50/M
B
Left parietal
Well
SM
40/M
B
Left parietal
Well
JM
31/M
B
Right spastic hemiplegia Right hemiplegma aphasia Right hemiplegia
Left occipital
Died
UM JC
36/M 24/M
B W
Trauma, depressed fracture Trauma Fractured base
Left frontal Right temporal
Died Died
DM ST
7/M 40/M
B B
Trauma, subdural Depressed fracture
Left occipital Left parietal
Well Well
HG
60/M
W
Trauma
Right frontal
Died
CC GL RE
32/M 4/M 18/M
W W B
Post-trauma Shunted Postencephalus
Right occipital Right parietal Left frontal
Well Well Well
EM Mt,
5/t" 16/M
B B
Postencephalitis Postencephalitls
Well Well
MDK
6/M
W
Right frontal Left frontal (daughter cyst) Right thalamic
DV
35/M
B
Well
ZOM
44/M
W
Right frontoparietal Left temperoparietal
JR EK WZ
23/F 12/b
15/M
W B B
Encephalitis Frontal sinusitis Frontal sinusitis
Right frontal Left frontal Left frontal
Well Died Died
SL
5/M
B
Otmtis media
Right parietal
Well
GL PK
32/M 4/F
W B
Otitis Otitis
Well Well
LP
40/M
B
Left temporal (air) Left temperoparietal Right thalammc
AN
35/M
B
ED TM
50/M 70/M
B B
RS PM
35/M 47/M
W B
Comatosed Confused, pyrexial decreasing level of consciousness Confused, pyrexial Dense right hemiplegia stupor Confused, left hemlplegia, dysphasia Confused, left hemiplegia ttydrocephalus Right sided headache, right facial, hemiplegia Pyrexial, drowsy vomiting Right sided fits frontal headache Headache, vomiting neck stiffness Left hemiplegia, confused Coma, pyrexial, dilated left pupil right sided fits Confused, left hemiplegaa Right hemiplegia Right hemiplegia, decreased level of consciousness Left facial, left hemiplegia Confused, dysarthria Headache, contused Left hemiplegia, decreased sensation Confused, pyrexial neck stiffness Right facial hemiplegia Headache, chest pain tremor, left hemlplegia Confused, pyrexial Aphasia, abnormal rightsided movements
Trauma Post-trauma depressed fracture Trauma, fracture, intracerebral clot drained Post-trauma septic skull wound Post-trauma
Encephalitis Postencephalitis Encephalitis
Pneumonia Pneumonia
Well Well
Well
Died
Well
Unknown Unknown
Right frontal, right parietal Left frontal Right frontal
Well Well Well
Unknown Unknown
Right occipital Left parietal
Dxed Well
M, male; F, female; W, white; B, South African Bantu. Trauma accounted for 14 patients. Primary intracranial infection for seven, sinus or ear infection for five; two patients had pneumonia In four patients no clinlcaUy obvious primary focus was noted. One was postoperative. Nine patients were white (European) and the rest South African Bantu. Four were female.
573
COMPUTERISED TOMOGRAPHY Table 2 - Subdurat
-Name
empyemas
Age~sex
Race
Clinical features
Predisposing factors
Site
Outcome
AO
25/M
W
13/M
B
Fronto-ethmoiditis sinusitis Postoperative subdural
Left frontal subdural Frontal empyema
Well
PK SN WM
58/M 58/M
B B
Trauma Trauma
26/M
B
Subdural empyema Left frontal empyema Right temporal
Well Well
SM
Pyrexial stupor confused Headache, vomiting right sided fits, left dilated pupil Confused, drowsy Right hemiplegia, right fits Headache, ataxic obtunded
Trauma, base fracture, otitis media
M, male; F, female;W, white; B, South African Bantu (Negro). Trauma accounted for all but one of this group, who had sinusitis. All were male. Only one was white.
Fig. 1 - Cerebral abscess. In the precontrast scan (a), extensive area of low density displacing the ventricles in the left temporoparietal region. With contrast (b), there is typical rim enhancement of the capsule.
Fig. 2 - Multilocular abscess. (a) shows an extensive area of low density in the right parieto-occipital region with mass effect. After contrast (b), a multilocular abscess is demonstrated.
Well
Well
574
Fig. 3
CLINICAL RADIOLOGY
Multiple abscesses. Primary focus was in the lung.
Fig. 4 Developing abscess. (a) shows a small low density in the left temporal region. Seven days later, (b) an abscess cavity is demonstrated with air. This allowed for the correct timing of surgical intervention. The primary focus was in the ear.
We feel that the failure of demonstrating the typical capsule was due to the fact that at post-mortem, a solid-aspergilloma was found. The second patient was found to have a ruptured abscess. We feel that at the time of scanning the latter patient, the cavity had decompressed itself and, therefore, we did not demonstrate its capsule. It should be remembered that both antibiotics and corticosteroids can markedly decrease the contrast enhancement of the abscess capsule. Angiography and isotope scanning are positive in only 90% of patients with brain abscess (Beller et al., 1973). They do not indicate the exact nature, stage nor precise anatomical site o f the abscess. In contrast, CT is 100% positive, gives accurate localisation and determines the presence o f daughter cysts and abscesses at other sites (Fig. 3a, b). It allows for serial examinations at short intervals, to gauge the correct time for surgical intervention, i.e. in following the evolution of an abscess from a cerebritis to cavitation with capsule formation (Fig. 4a, b). The abscess capsule rim constitutes three layers: inner granulation layer, middle collagen layer and outer reactive glial layer. The capsule takes some time to develop, as the fibroblasts forming the collagen layer take time to be activated (Moore and Thomas, 1974). The timing o f the surgical intervention is important, as surgery prior to the developm e n t of a capsule is generally not advised. Surgery requires: (a) early and accurate identification o f the abscess capsule; (b) accurate anatomical localisation o f the abscess; (c) identification of multiple loculations and multiplicity o f lesions. These factors promote decreased surgical trauma and increased accuracy of treatment and are corn-
Fig. 5 - This shows the presence of a draining catheter and postoperative air in the abscess cavity. The surrounding cerebral oedema and mass effect are again present.
COMPUTERISED
TOMOGRAPHY
575
Fig. 6 - Resolving abscess. Six-year-old child with otitis media. A well-defined capsule in the left parietal region demonstrated with contrast in (a). There is surrounding cerebral oedema. (b) Follow-up scan two weeks postoperatively. Capsule no longer present, with some resolution in the amount of cerebral oedema. The mass effect is less prominent.
Fig. 7 - This seven-year-old boy with encephalitis demonstrates the abscess rim after contrast (a). The lack of surrounding oedema is due to the high doses of antibiotics. Follow-up (b) showed some resolution in the size. A further scan (c) five weeks later, shows complete resolution. pletely satisfied b y CT and not b y angiography and isotope scanning. All except one o f our patients were treated surgically b y aspiration under direct vision and our overall m o r t a l i t y rate was 26%. The mortality rate from cerebral abscess varies from 36 to 53% (Morgan et al., 1973; Carey et al., 1972). Therapeutic success has, in the past, b e e n hampered b y incorrect diagnosis, late diagnosis and poor localisation. CT offers a solution to all these problems. It is useful for frequent follow-up of patients with
576
CLINICAL RADIOLOGY treated cerebral abscess (Fig. 5). We have been able to follow the progress o f patients postsurgery, demonstrating a decrease in abscess size, a reduction in the amount of surrounding oedema and a decrease in the mass effect (Fig. 6a, b). We were able to follow the progress o f one patient (MDK) who had a surgically inaccessible abscess and who was treated conservatively with high doses of antibiotics. He made a good recovery and is now well (Fig. 7a,
b, c). SUBDURAL EMPYEMA A peripheral area o f low density with EMI number between 10 and 14 with an associated mass effect (Fig. 8) is seen. After the administration of iodinated contrast media, all demonstrated medial rim enhanceFig. 8 - Subdural empyema. Peripheral low density on the right with enhancement after contrast. The right lateral ment. The thickness o f the rim demonstrated varied somewhat, but we feel that the chronic type o f ventricle is attenuated. subdural empyema will demonstrate a thicker capsule. In our series, cerebral oedema was not the prominent feature it was with the intracerebral abscess. All, except one case, were associated with a history of trauma with the development of a subdural or intracerebral haematoma (Fig. 9). The other patient had a frontal sinusitis and subsequently developed a frontal empyema. All underwent surgical drainage and were discharged well. CT is of value in the postoperative follow-up of these patients (Fig. 9c). We had no mortality in this group.
Fig. 9 - Post-traumatic subdural empyema. Two low density areas in the left frontoparietal regions (a) which after intravenous contrast (b) demonstrates a loculated subdural empyema. Follow-up post-aspiration scan (c) shows resolution. Note the bony defect.
COMPUTERISED TOMOGRAPHY
577
cysts as well as the timing of surgical intervention. It is important to obtain good quality scans; general anaesthesia may be required. CT is very useful in following the progress of abscesses and in one of our cases, it allowed us to follow the complete resolution, a thalamic abscess managed conservatively.
REFERENCES Beller, A. J., Sahar, A. & Praiss, I. (1973). Brain abscess" review of 89 cases over a period of 30 years. Journal o/ Neurology, Neurosurgery and Psychiatry, 36,757 768. Carey, M. E., Chou, S. N. & French, L. A. (1972). Experience with brain abscesses. Journal of Neurosurgery, 36(1), 1-9. Lott, T., el Gammal, T., da Silva, R., ttank, D. & Reynolds, J. lqg. 10 Post-traumatic abscess. An intracerebral abscess (1977). Evaluation of brain and epidural abscesses by CT. with a depressed bony fragment lying within it. Radiology, 122, 376. Moore, G. A. & Thomas, L. M. (1974). Infections including abscesses of the brain, spinal cord, intraspinal and intracranial lesions. Surgical Annual, 6, 413-437. CONCLUSION Morgan, H., Wood, M. W. & Murphey, [. (1973). Experience We present a large series of intracerebral abscess with 88 consecutive cases of brain abscess. Journal o f Neurosurgery, 38,698-704. and subdural empyema, in which the mortality is 26%. This is an improvement on previously published New, P. F. J., Davis, K. R. & Ballantine, H. T. (1976). CT in cerebral abscess. Radiology, 121,641-646. results. We believe the mortality rate has decreased Zlmmerman, R. A., Patel, S. & Bilaniuk, L. T. (1976). Demonbecause CT scanning allows for early diagnosis, stratlon of purulent bacterial intracranial infections by CT. American Journal o f Radiology, 127, 155-165. accurate localisation and recognition o f any daughter
43
