European Journal of Radiology, 12 (1991) 113-119
113
Elsevier
EURRAD
00135
CT scanning in meningitis Stephan Wardle and Helen Carty Department of Radiology, Royal Liverpool Children’s Hospital, Alder Hey, Liverpool, U.K.
(Received 21 July 1990; accepted
Key words: Meningitis,
complications;
Meningitis,
after revision 22 October
CT; Computed
tomography,
1990)
brain; Brain, radiography
Abstract Twelve paediatric cases of acute meningitis were reviewed retrospectively. Findings on CT scan were compared with the clinical course and resulting neurological sequelae. Complications detected by CT scanning include subdural effusion, empyema, hydrocephalus, cerebral atrophy, oedema and infarction. The CT scan results adequately correlated with neurological signs in most cases. Infarction was a reliable indicator of neurological sequelae. Cerebral atrophy alone, however, did not correlate well with the clinical sequelae.
Introduction
Materials and Methods
The introduction of computed tomography (CT) is a major advance in the diagnosis of inflammatory diseases of the brain. It has been shown to be both sensitive and accurate in detecting, characterising and delineating the purulent bacterial infectious process [I]. It is a reliable, repeatable and non-invasive technique [2,3] which enables earlier diagnosis of potentially fatal but treatable complications of acute meningitis such as subdural effusion and empyema [4]. It will reveal some structural abnormalities when neurological complications have occurred [5]. It is also helpful in assessing the degree of hydrocephalus when that complication occurs [6]. The case records and CT scans of 12 patients suffering from acute meningitis admitted to this hospital over a 2-year period are reviewed to determine how CT scanning contributed to the management and outcome of meningitis in these children.
The case notes of twelve children ranging in age from 3 days to 8 years 8 months who, during their admission for acute meningitis, had a CT scan were reviewed, along with their scans. The CT findings were identified and compared with data about the clinical course of each patient obtained from the case sheets. The outcome and resulting neurological sequelae were found from subsequent outpatient follow-up. All patients were initially treated with triple antibiotic therapy which was subsequently changed to a single specific antibiotic once the organism had been cultured and its sensitivities determined. The patient with tuberculous meningitis was treated with standard anti-tuberculous therapy, on diagnosis.
Address for reprints: Dr. Helen Carty, Department of Radiology, Royal Liverpool Children’s Hospital, Alder Hey, Liverpool, L12 2AP, U.K. 0720-048X/91/$03.50
0 1991 Elsevier Science Publishers
Results Details of the patients’ ages and infecting organisms are shown on Table 1. The causative organism was cultured from the cerebrospinal fluid or blood. Six patients had Neisseria meningitides infection, average age being 3 years 10 months. Three patients (aged 3 days-6 weeks) had group B b-haemolytic streptococcal infection and two (age 7 months) were
B.V. (Biomedical
Division)
114 TABLE
TABLE
1
Case No. 1
Sex
Age at presentation
Infecting organism
No. of scans performed
M
11 weeks
Neisseria
1
meningitides
2
F
3
F
3
CT findings at initial scan
Infecting organism
8 years 8 months 5 months
Neisseria
2
meningitides Neissen’a
2
Cerebral atrophy Cerebral oedema Subdural empyema Subdural effusion Infarction Hydrocephalus Gyral brightness White-matter changes
meningitides
4
M
Neisseria
8 years
1
meningitides
5
F
6
M
4 years 4 months 18 months
Neisseria
3
meningirides Neisseria
2
meningitides
I
M
18 months
Mycobacterium
3
tuberculosis
8
F
Group B
3 days
1
Streptococcus
9
M
6 weeks
Group B
3
Streptococcus
10
M
6 weeks
Group B
4
Streptococcus
11
M
7 months
Haemophilus
1
injluenzae
12
M
7 months
Haemophilus
2
injluenzae
infected by Haemophilus injluenza. One patient suffered from tuberculous meningitis. The presenting complaints tended to reflect the age of the patient rather than the infecting organism, the commonest presenting symptoms are shown in Table 2. The CT scans were performed when indicated by the clinical, course. Eight of the 12 patients had more than one scan. Findings on the initial and late CT scans are shown in Tables 3 and 4. TABLE
The indications for each scan are shown in Table 5. The results of the scans for each patient and the neurological condition at follow-up are shown in Table 6. Three patients (Cases 7, 9 and 10) required ventriculoperitoneal (VP) shunts for their resultant hydrocephalus. Case 7, which was tuberculous meningitis, had a VP shunt successfully inserted on the 1 lth day of his admission, but also required cervical thoracic laminectomy for spinal arachnoiditis due to the infection. Case 9 also had a shunt successfully inserted 2 months after the onset of the meningitis. Case 10,
TABLE 4 Findings on follow-up Cerebral and cerebellar Subdural empyema Subdural effusion Infarction Gyral brightness Hydrocephalus
atrophy
5 1 1 3 1 3
2
Clinical symptoms
TABLE
on presentation
5
Indications Symptom
No. of patients
Neck stiffness Diarrhoea and vomiting Pyrexia Decreased consciousness Rash Headache Bulging fontanelle Anorexia Apnoeic spells Fitting
4
Most patients presented
I 6 6 3 2 4 3
for scanning
Fitting Focal neurological signs Increased head circumference Decreased consciousness Continued pyrexia Papilloedema Bulging fontanelle Recurrence of symptoms Follow-up
1 3
with more than one symptom.
The total number of indications differs from the total number of patients because several patients had more than one scan and more than one indication for each scan.
115 TABLE
6
Scan results - neurological
outcome
Case No.
Outcome
Time of scan
z
(days)
z&
z
z
z: _;j
‘Z
E
2 k
z
G
5
2
16
+
_
-
1 3
+ _
_ -
_ -
Incoordination left arm
11 120
_
-
_ -
Slight hearing loss left ear
5
_
-
-
4 9 135
-
+ +
_ _
5 14
-
_
-
9 24 62
_
_
-
8
11
_
+
9
9 29 13.5
+ _ -
Speech and intellect adversely affected right peripheral visual field loss and emotional disturbances
-
_ -
_
+ +
_
_ +
_
-
_
_ -
-
+ + _
_
_
+
-
_
+
-
-
+
_
+ _ -
-
_
-
_ _ -
_
-
+ +
Hydrocephalus No follow-up notes available
+ _ _
+ +
-
+ _ _
-
+ + -
+ _
_ +
-
-
+ -
Severe mental and physical handicap and hydrocephalus
-
_
-
-
_
-
-
_
-
-
+
+ -
-
-
-
_
_ -
+ -
_
+
-
-
+ -
2 39 120 132
11
9
12
3 11
+ +
No neurological sequelae
+ +
-
10
-
No neurological sequelae
+ +
however, required a second shunt on the left after the first had been inserted on the right. Three patients required subdural paracentesis
Hemiparesis, right hemianopia, VI nerve palsy Hemiparesis (improving) Hydrocephalus Spasticity all limbs
No neurological sequelae No follow-up notes available
because of subdural empyema or effusion which was diagnosed by CT scan. Only one patient had a subdural collection which did not require drainage.
116
Discussion During an uncomplicated course of meningitis there is normally no cranial CT scan performed. The patients reviewed represent those cases of meningitis with the most serious neurological complications which, therefore, required CT scanning in an attempt to identify a remediable cause for complications such as fitting, focal neurological signs and significant alteration in mental function. In cases which are successfully treated or in the early stages of meningitis there are no abnormalities found on CT scan [ 11. When neurological complications have occurred CT will, in most instances, reveal some structural abnormalities [ 51. The study confirms this - of the cases reviewed only two cases were reported as normal. The indications for scanning in these patients were, in one, failure to improve after 4-5 days of antibiotic therapy and in the other a single episode of fitting 8 days after the commencement of the illness. The lack of any obvious lesion to explain these complications excluded any more serious pathology requiring treatment. In one other case, CT scan failed to adequately explain unilateral neurological signs, the only abnor-
Fig. 1. Case 5 (day 9). Extensive low density within virtually the whole of the left cerebral hemisphere, with a shift from left to right. The appearance is of extensive cerebral oedema.
mality present on CT being generalised cerebral oedema. A second scan still in the acute phase of the infection showed continuing cerebral oedema with no focal lesion. At discharge from hospital this child had continued neurological deficit with into-ordination of the left arm. This was the only scan showing cerebral oedema in which no associated structural abnormality, e.g., infarction, subdural empyema, abscess etc. was demonstrated. In the other cases where infarction occurred, a tight appearance of the brain, characteristic of cerebral oedema, was present on the initial scan. Repeat scans several days later revealed the focal defect. Other studies have also shown that ischaemic lesions are occasionally difficult to identify by CT scan during their acute stages so that repeat scans are necessary. [7]. Focal infarcts will not be visible on ultrasound until much later than CT. Small ones will be missed, and even large lesions lying laterally under the parietal bone may also be missed. Previous reports have documented the occurrence of cerebral infarcts secondary to vasculitis of arteries in bacterial meningitis [8] and due to leptomeningeal capillary congestion [9]. There have been several reports documenting detection of such infarcts by CT scan [5,10]. Four children, Cases 5, 6, 8, 10, had infarcts which were compatible with the neurological findings (Figs. 1 and 2.) The presence of an infarct and neurological signs carries a bad prognosis. Case 6 also showed gyral brightness on non-contrast enhanced CT, which is an appearance indicative of hypoxic brain damage. Case 8 also had serious neurological sequelae. Her CT scan showed cerebral atrophy and fairly severe white-matter disease. She continued to suffer repeated seizures and subsequently developed severe spasticity of all limbs. Cerebral atrophy was a feature generally seen on scans performed after the acute phase of infection. It was present in five patients. Of these cases, follow-up information was available on four; one child was normal, two had major neurological sequelae with intellectual impairment. The fourth had just a slight unilateral hearing loss. Atrophy was reported to occur more commonly in the frontal lobe by Cockrill et al. [ 111. However, this was not evident in another study [ 71 and was not evident in these cases. Atrophy has been reported to be very likely to be associated with subsequent intellectual deficit [ 71. This does not seem evident in this review. Development in Case 3 was reported as progressing normally several months after the episode of meningitis,
117
Fig. 2. Case 5 (day 135). Large infarct involving the left cerebral hemisphere at the site of the previous oedema.
despite a follow-up CT can still showing generalised cerebral atrophy. No cases of viral meningitis were scanned. This is probably because viral meningitis is almost always a less severe and self-limiting infection which does not in general cause neurological disturbances. No abnormalities were found in four patients with viral meningitis on CT scan in one study [ 121. Tuberculous meningitis is now a rare occurrence in developed countries, but one case was included in this study. This patient developed obstructive hydrocephalus, which is a frequent occurrence in this type of meningitis [ 61. Two of the three patients with group B streptococcal meningitis presented with fitting, in keeping with previous reports [ 131. Fitting was only seen at a later stage in meningitis due to other organisms. The initial scans in these patients showed cerebral atrophy, white-matter disease, subdural empyema and cerebral oedema. Residual neurological sequelae resulted in each case. CT scanning allows earlier diagnosis of complications which may be amenable to successful surgical intervention [4,7]. It also reduces the need for exploratory procedures and lowers the operative risks and complications [ 141. In this series of patients, diagnosis of subdural col-
lection was made in four patients with CT scan. Three of these were successfully drained surgically, the fourth did not require drainage. The incidence of subdural collection in meningitis in infants has been reported in studies to be between 10 and 50% [ 13,15,16]. Big subdural collections may be diagnosed by ultrasound when there is access through the patent fontanelle, but small collections and, in particular, pockets of encysted collections are more reliably diagnosed by CT. When there is easy access to MR, this may be preferable due to the lack of ionising radiation, but this is still not generally available in most children’s acute units. White-matter disease, consequent on the meningitis, is more easily detected by MR. Subdural empyema has an incidence of approximately 2% in meningitis [ 131, and mortality rates of 50% were previously reported [ 171. However, since the introduction of CT scan, mortality has been substantially reduced, probably due to earlier diagnosis and more effective treatment of complications [4]. Dodge and Schwartz [ 131 report that the role of subdural effusions is uncertain in the development of permanent neurological sequelae but state that their role has probably been overstressed. With subdural empyema, Jacobsen and Farmer [4] report that only one of six patients had permanent sequelae. Differentiation of subdural empyema and effusion
Fig. 3. Case 12. Contrast enhanced CT.There is meningealenhancement surrounding the subdural collection indicating an empyema.
118
Fig. 4. Case 9. First scan showing areas of low density on the grey matter posteriorly. There are tiny frontal subdural collections.
Fig. 5 (a and b) Case 9 (day 135). The ventricles
using CT is difficult, both showing a crescent shaped hypodense area adjacent to the cortex which can produce a mass effect with a shift of the lateral and third ventricles [ 10,141. Rim-like enhancement with i.v. (intravenous) contrast indicates an empyema [ 10,14,18] (Fig. 3). Lack of enhancement does not differentiate an early subdural empyema from a subdural effusion [ 10,14,18]. This problem is illustrated in Case 12 in whom the initial scan showed subdural collections with no enhancement, but a subsequent scan showed the typical meningeal enhancement. A high Hounslield number indicates a raised protein content of the CSF but does not necessarily indicate active infection. Communicating hydrocephalus can result secondary to pia-arachnoidal adhesions and obstructive hydrocephalus can result secondary to aqueduct stenosis [ 191. Minimal ventricular widening can occur in the initial stages of the illness and is a frequent and usually reversible CT finding [7], but requires follow-up. Hydrocephalus requiring shunting occurred in three patients (Figs. 4 and 5). Symptoms in these patients included fitting, papilloedema and increase in head circumference. On follow-up, two of the three had neurological sequelae, though in Case 7 these were not severe and improved gradually with time. It was detected as both an early and a late complication.
have substantially increased in size, indicating obstructive as the 4th ventricle is narrow.
post-meningitis
hydrocephalus,
which is
119
The ventricular size is easily monitored by ultrasound when the fontanelle is patent, CT or MR being required in these patients to assess subdural collections or to elucidate a confusing ultrasonic appearance. It has been suggested that periependymal oedema may be a sign of evolving hydrocephalus and amenable to neurosurgical intervention. Serial scans can be performed if this is suspected [ 71. Conclusions CT has an important role in the management of bacterial meningitis. Lesions which explain neurological complications are identified. Earlier diagnosis of complications, for which surgical intervention is appropriate, is facilitated. The indications for scanning include fitting and signs of neurological disturbance in the acute phase of infection. After the acute phase, CT is indicated to assess focal neurological signs which have developed or failed to resolve, even though infection has been adequately treated by antibiotics. Cerebral atrophy alone on CT scanning does not correlate with the extent of neurological sequelae. When associated with focal infarction, it correlates well with the clinical sequelae. Infarcts may exist without general cerebral atrophy and this results in focal neurological damage. Subdural effusion or empyema does not have a bad prognosis as long as it is diagnosed early and treated promptly. Early detection of hydrocephalus and shunting, if appropriate, may minimise neurological damage. Cerebral oedema is usually present in association with more serious neurological damage in the acute phase of infection, and repeat scans are necessary after the acute phase to assess further structural abnormalities. Acknowledgement I would like to thank Mrs Dorothy patience in typing this manuscript.
Turner for her
References 1 Zimmerman RA, Pate1 S, Bilaniuk LT. Demonstration of purulent bacterial intracranial infections by computed tomography. AJR 1976; 127: 155-165. Ambrose J. Computerised transverse axial scanning (tomography). II: clinical applications. Br J Radio1 1973; 42: 1023-1047. Paxton R, Ambrose J. The EM1 scanner: brief review of the first 650 patients. Br J Radio1 1974; 47: 530-565. Jacobsen PL, Farmer TW. Subdural empyema complicating meningitis in infants: improved prognosis. Neurology (NY) 198 1; 31: 190-193. Stovring J, Snyder RD. Computed tomography in childhood bacterial meningitis. J Paediatr 1976; 5: 820-823. Price HI, Danziger A. Computed tomography in cranial tuberculosis. AJR 1978. 130: 769-771. Bodino J, Lylyk P, Del Valle M, Wasserman J, Leiguarda R, Monges J, Lopez EL. Computed tomography in purulent meningitis. Am Dis Child 1982; 136: 495-501. Kinkel WR, Jacobs L. Computerized axial transverse tomography in cerebra-vascular disease. Neurology 1976; 26: 294. Butler IJ, Johnson RT. Central nervous system infections. Paediatr Clin N Am 1974; 21: 649-668. Weisberg LA. Cerebral computerized tomography in intracranial inflammatory disorders, Arch Neurol 1980; 37: 137-142. Cockrill HH, Dreisbach J, Lowe B, Yamouchi T. Computed tomography in leptomeningeal infections. AJR 1978; 130: 511-515. 12 Schneider E, Becker H, Klos G. Demonstration of inflammatory diseases of the brain and meninges by computerised tomography. In Lanksch W, Kazner E, eds. Cranial computerized tomography, Berlin: Springer Verlag, 1976. 13 Dodge PR, Schwartz MN. Bacterial meningitis: a review of selected aspects. N Engl J Med 1965; 272: 954, 1003. 14 Joubert MJ, Stephanov S. Computerized tomography and surgical treatment of intracranial suppuration. J Neurosurg 1977; 47: 73-78. 15 McKay RJ, Ingraham FD, Matson DD. Subdural fluid complicating bacterial meningitis. JAMA 1953; 152: 387-391. 16 Smith MHD, Dormont RE, Prather GW. Subdural fluid complicating bacterial meningitis. Paediatrics 1951; 7: 34-43. 17 Galbraith JG, Barr VW. Epidural abscess and subdural empyema. Adv Neurol 1974; 6: 257-267. 18 Bilaniuk LT, Zimmerman RA, Brown L et al. Computer tomography in meningitis. Neuroradiology 1978; 16: 13-14. 19 Salmon JH. Ventriculitis complicating meningitis. Am J Dis Child 1972: 124: 35-40.
113
Elsevier
EURRAD
00135
CT scanning in meningitis Stephan Wardle and Helen Carty Department of Radiology, Royal Liverpool Children’s Hospital, Alder Hey, Liverpool, U.K.
(Received 21 July 1990; accepted
Key words: Meningitis,
complications;
Meningitis,
after revision 22 October
CT; Computed
tomography,
1990)
brain; Brain, radiography
Abstract Twelve paediatric cases of acute meningitis were reviewed retrospectively. Findings on CT scan were compared with the clinical course and resulting neurological sequelae. Complications detected by CT scanning include subdural effusion, empyema, hydrocephalus, cerebral atrophy, oedema and infarction. The CT scan results adequately correlated with neurological signs in most cases. Infarction was a reliable indicator of neurological sequelae. Cerebral atrophy alone, however, did not correlate well with the clinical sequelae.
Introduction
Materials and Methods
The introduction of computed tomography (CT) is a major advance in the diagnosis of inflammatory diseases of the brain. It has been shown to be both sensitive and accurate in detecting, characterising and delineating the purulent bacterial infectious process [I]. It is a reliable, repeatable and non-invasive technique [2,3] which enables earlier diagnosis of potentially fatal but treatable complications of acute meningitis such as subdural effusion and empyema [4]. It will reveal some structural abnormalities when neurological complications have occurred [5]. It is also helpful in assessing the degree of hydrocephalus when that complication occurs [6]. The case records and CT scans of 12 patients suffering from acute meningitis admitted to this hospital over a 2-year period are reviewed to determine how CT scanning contributed to the management and outcome of meningitis in these children.
The case notes of twelve children ranging in age from 3 days to 8 years 8 months who, during their admission for acute meningitis, had a CT scan were reviewed, along with their scans. The CT findings were identified and compared with data about the clinical course of each patient obtained from the case sheets. The outcome and resulting neurological sequelae were found from subsequent outpatient follow-up. All patients were initially treated with triple antibiotic therapy which was subsequently changed to a single specific antibiotic once the organism had been cultured and its sensitivities determined. The patient with tuberculous meningitis was treated with standard anti-tuberculous therapy, on diagnosis.
Address for reprints: Dr. Helen Carty, Department of Radiology, Royal Liverpool Children’s Hospital, Alder Hey, Liverpool, L12 2AP, U.K. 0720-048X/91/$03.50
0 1991 Elsevier Science Publishers
Results Details of the patients’ ages and infecting organisms are shown on Table 1. The causative organism was cultured from the cerebrospinal fluid or blood. Six patients had Neisseria meningitides infection, average age being 3 years 10 months. Three patients (aged 3 days-6 weeks) had group B b-haemolytic streptococcal infection and two (age 7 months) were
B.V. (Biomedical
Division)
114 TABLE
TABLE
1
Case No. 1
Sex
Age at presentation
Infecting organism
No. of scans performed
M
11 weeks
Neisseria
1
meningitides
2
F
3
F
3
CT findings at initial scan
Infecting organism
8 years 8 months 5 months
Neisseria
2
meningitides Neissen’a
2
Cerebral atrophy Cerebral oedema Subdural empyema Subdural effusion Infarction Hydrocephalus Gyral brightness White-matter changes
meningitides
4
M
Neisseria
8 years
1
meningitides
5
F
6
M
4 years 4 months 18 months
Neisseria
3
meningirides Neisseria
2
meningitides
I
M
18 months
Mycobacterium
3
tuberculosis
8
F
Group B
3 days
1
Streptococcus
9
M
6 weeks
Group B
3
Streptococcus
10
M
6 weeks
Group B
4
Streptococcus
11
M
7 months
Haemophilus
1
injluenzae
12
M
7 months
Haemophilus
2
injluenzae
infected by Haemophilus injluenza. One patient suffered from tuberculous meningitis. The presenting complaints tended to reflect the age of the patient rather than the infecting organism, the commonest presenting symptoms are shown in Table 2. The CT scans were performed when indicated by the clinical, course. Eight of the 12 patients had more than one scan. Findings on the initial and late CT scans are shown in Tables 3 and 4. TABLE
The indications for each scan are shown in Table 5. The results of the scans for each patient and the neurological condition at follow-up are shown in Table 6. Three patients (Cases 7, 9 and 10) required ventriculoperitoneal (VP) shunts for their resultant hydrocephalus. Case 7, which was tuberculous meningitis, had a VP shunt successfully inserted on the 1 lth day of his admission, but also required cervical thoracic laminectomy for spinal arachnoiditis due to the infection. Case 9 also had a shunt successfully inserted 2 months after the onset of the meningitis. Case 10,
TABLE 4 Findings on follow-up Cerebral and cerebellar Subdural empyema Subdural effusion Infarction Gyral brightness Hydrocephalus
atrophy
5 1 1 3 1 3
2
Clinical symptoms
TABLE
on presentation
5
Indications Symptom
No. of patients
Neck stiffness Diarrhoea and vomiting Pyrexia Decreased consciousness Rash Headache Bulging fontanelle Anorexia Apnoeic spells Fitting
4
Most patients presented
I 6 6 3 2 4 3
for scanning
Fitting Focal neurological signs Increased head circumference Decreased consciousness Continued pyrexia Papilloedema Bulging fontanelle Recurrence of symptoms Follow-up
1 3
with more than one symptom.
The total number of indications differs from the total number of patients because several patients had more than one scan and more than one indication for each scan.
115 TABLE
6
Scan results - neurological
outcome
Case No.
Outcome
Time of scan
z
(days)
z&
z
z
z: _;j
‘Z
E
2 k
z
G
5
2
16
+
_
-
1 3
+ _
_ -
_ -
Incoordination left arm
11 120
_
-
_ -
Slight hearing loss left ear
5
_
-
-
4 9 135
-
+ +
_ _
5 14
-
_
-
9 24 62
_
_
-
8
11
_
+
9
9 29 13.5
+ _ -
Speech and intellect adversely affected right peripheral visual field loss and emotional disturbances
-
_ -
_
+ +
_
_ +
_
-
_
_ -
-
+ + _
_
_
+
-
_
+
-
-
+
_
+ _ -
-
_
-
_ _ -
_
-
+ +
Hydrocephalus No follow-up notes available
+ _ _
+ +
-
+ _ _
-
+ + -
+ _
_ +
-
-
+ -
Severe mental and physical handicap and hydrocephalus
-
_
-
-
_
-
-
_
-
-
+
+ -
-
-
-
_
_ -
+ -
_
+
-
-
+ -
2 39 120 132
11
9
12
3 11
+ +
No neurological sequelae
+ +
-
10
-
No neurological sequelae
+ +
however, required a second shunt on the left after the first had been inserted on the right. Three patients required subdural paracentesis
Hemiparesis, right hemianopia, VI nerve palsy Hemiparesis (improving) Hydrocephalus Spasticity all limbs
No neurological sequelae No follow-up notes available
because of subdural empyema or effusion which was diagnosed by CT scan. Only one patient had a subdural collection which did not require drainage.
116
Discussion During an uncomplicated course of meningitis there is normally no cranial CT scan performed. The patients reviewed represent those cases of meningitis with the most serious neurological complications which, therefore, required CT scanning in an attempt to identify a remediable cause for complications such as fitting, focal neurological signs and significant alteration in mental function. In cases which are successfully treated or in the early stages of meningitis there are no abnormalities found on CT scan [ 11. When neurological complications have occurred CT will, in most instances, reveal some structural abnormalities [ 51. The study confirms this - of the cases reviewed only two cases were reported as normal. The indications for scanning in these patients were, in one, failure to improve after 4-5 days of antibiotic therapy and in the other a single episode of fitting 8 days after the commencement of the illness. The lack of any obvious lesion to explain these complications excluded any more serious pathology requiring treatment. In one other case, CT scan failed to adequately explain unilateral neurological signs, the only abnor-
Fig. 1. Case 5 (day 9). Extensive low density within virtually the whole of the left cerebral hemisphere, with a shift from left to right. The appearance is of extensive cerebral oedema.
mality present on CT being generalised cerebral oedema. A second scan still in the acute phase of the infection showed continuing cerebral oedema with no focal lesion. At discharge from hospital this child had continued neurological deficit with into-ordination of the left arm. This was the only scan showing cerebral oedema in which no associated structural abnormality, e.g., infarction, subdural empyema, abscess etc. was demonstrated. In the other cases where infarction occurred, a tight appearance of the brain, characteristic of cerebral oedema, was present on the initial scan. Repeat scans several days later revealed the focal defect. Other studies have also shown that ischaemic lesions are occasionally difficult to identify by CT scan during their acute stages so that repeat scans are necessary. [7]. Focal infarcts will not be visible on ultrasound until much later than CT. Small ones will be missed, and even large lesions lying laterally under the parietal bone may also be missed. Previous reports have documented the occurrence of cerebral infarcts secondary to vasculitis of arteries in bacterial meningitis [8] and due to leptomeningeal capillary congestion [9]. There have been several reports documenting detection of such infarcts by CT scan [5,10]. Four children, Cases 5, 6, 8, 10, had infarcts which were compatible with the neurological findings (Figs. 1 and 2.) The presence of an infarct and neurological signs carries a bad prognosis. Case 6 also showed gyral brightness on non-contrast enhanced CT, which is an appearance indicative of hypoxic brain damage. Case 8 also had serious neurological sequelae. Her CT scan showed cerebral atrophy and fairly severe white-matter disease. She continued to suffer repeated seizures and subsequently developed severe spasticity of all limbs. Cerebral atrophy was a feature generally seen on scans performed after the acute phase of infection. It was present in five patients. Of these cases, follow-up information was available on four; one child was normal, two had major neurological sequelae with intellectual impairment. The fourth had just a slight unilateral hearing loss. Atrophy was reported to occur more commonly in the frontal lobe by Cockrill et al. [ 111. However, this was not evident in another study [ 71 and was not evident in these cases. Atrophy has been reported to be very likely to be associated with subsequent intellectual deficit [ 71. This does not seem evident in this review. Development in Case 3 was reported as progressing normally several months after the episode of meningitis,
117
Fig. 2. Case 5 (day 135). Large infarct involving the left cerebral hemisphere at the site of the previous oedema.
despite a follow-up CT can still showing generalised cerebral atrophy. No cases of viral meningitis were scanned. This is probably because viral meningitis is almost always a less severe and self-limiting infection which does not in general cause neurological disturbances. No abnormalities were found in four patients with viral meningitis on CT scan in one study [ 121. Tuberculous meningitis is now a rare occurrence in developed countries, but one case was included in this study. This patient developed obstructive hydrocephalus, which is a frequent occurrence in this type of meningitis [ 61. Two of the three patients with group B streptococcal meningitis presented with fitting, in keeping with previous reports [ 131. Fitting was only seen at a later stage in meningitis due to other organisms. The initial scans in these patients showed cerebral atrophy, white-matter disease, subdural empyema and cerebral oedema. Residual neurological sequelae resulted in each case. CT scanning allows earlier diagnosis of complications which may be amenable to successful surgical intervention [4,7]. It also reduces the need for exploratory procedures and lowers the operative risks and complications [ 141. In this series of patients, diagnosis of subdural col-
lection was made in four patients with CT scan. Three of these were successfully drained surgically, the fourth did not require drainage. The incidence of subdural collection in meningitis in infants has been reported in studies to be between 10 and 50% [ 13,15,16]. Big subdural collections may be diagnosed by ultrasound when there is access through the patent fontanelle, but small collections and, in particular, pockets of encysted collections are more reliably diagnosed by CT. When there is easy access to MR, this may be preferable due to the lack of ionising radiation, but this is still not generally available in most children’s acute units. White-matter disease, consequent on the meningitis, is more easily detected by MR. Subdural empyema has an incidence of approximately 2% in meningitis [ 131, and mortality rates of 50% were previously reported [ 171. However, since the introduction of CT scan, mortality has been substantially reduced, probably due to earlier diagnosis and more effective treatment of complications [4]. Dodge and Schwartz [ 131 report that the role of subdural effusions is uncertain in the development of permanent neurological sequelae but state that their role has probably been overstressed. With subdural empyema, Jacobsen and Farmer [4] report that only one of six patients had permanent sequelae. Differentiation of subdural empyema and effusion
Fig. 3. Case 12. Contrast enhanced CT.There is meningealenhancement surrounding the subdural collection indicating an empyema.
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Fig. 4. Case 9. First scan showing areas of low density on the grey matter posteriorly. There are tiny frontal subdural collections.
Fig. 5 (a and b) Case 9 (day 135). The ventricles
using CT is difficult, both showing a crescent shaped hypodense area adjacent to the cortex which can produce a mass effect with a shift of the lateral and third ventricles [ 10,141. Rim-like enhancement with i.v. (intravenous) contrast indicates an empyema [ 10,14,18] (Fig. 3). Lack of enhancement does not differentiate an early subdural empyema from a subdural effusion [ 10,14,18]. This problem is illustrated in Case 12 in whom the initial scan showed subdural collections with no enhancement, but a subsequent scan showed the typical meningeal enhancement. A high Hounslield number indicates a raised protein content of the CSF but does not necessarily indicate active infection. Communicating hydrocephalus can result secondary to pia-arachnoidal adhesions and obstructive hydrocephalus can result secondary to aqueduct stenosis [ 191. Minimal ventricular widening can occur in the initial stages of the illness and is a frequent and usually reversible CT finding [7], but requires follow-up. Hydrocephalus requiring shunting occurred in three patients (Figs. 4 and 5). Symptoms in these patients included fitting, papilloedema and increase in head circumference. On follow-up, two of the three had neurological sequelae, though in Case 7 these were not severe and improved gradually with time. It was detected as both an early and a late complication.
have substantially increased in size, indicating obstructive as the 4th ventricle is narrow.
post-meningitis
hydrocephalus,
which is
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The ventricular size is easily monitored by ultrasound when the fontanelle is patent, CT or MR being required in these patients to assess subdural collections or to elucidate a confusing ultrasonic appearance. It has been suggested that periependymal oedema may be a sign of evolving hydrocephalus and amenable to neurosurgical intervention. Serial scans can be performed if this is suspected [ 71. Conclusions CT has an important role in the management of bacterial meningitis. Lesions which explain neurological complications are identified. Earlier diagnosis of complications, for which surgical intervention is appropriate, is facilitated. The indications for scanning include fitting and signs of neurological disturbance in the acute phase of infection. After the acute phase, CT is indicated to assess focal neurological signs which have developed or failed to resolve, even though infection has been adequately treated by antibiotics. Cerebral atrophy alone on CT scanning does not correlate with the extent of neurological sequelae. When associated with focal infarction, it correlates well with the clinical sequelae. Infarcts may exist without general cerebral atrophy and this results in focal neurological damage. Subdural effusion or empyema does not have a bad prognosis as long as it is diagnosed early and treated promptly. Early detection of hydrocephalus and shunting, if appropriate, may minimise neurological damage. Cerebral oedema is usually present in association with more serious neurological damage in the acute phase of infection, and repeat scans are necessary after the acute phase to assess further structural abnormalities. Acknowledgement I would like to thank Mrs Dorothy patience in typing this manuscript.
Turner for her
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