Patterns of Edema in Tumors vs. Infarcts

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Patterns of Edema in Tumors vs. Infarcts:

Visualization of White Matter Pathways

Ahmad Monajati1 Lucille Heggeness2

The computed tomographic (CT) scans of 339 patients with recent nonhemorrhagic cerebral infarct and 155 patients with supratentorial tumors were reviewed to evaluate the appearance of cerebral edema. White matter pathway edema characterized the CT pattern in 106 (68% ) of the 155 tumor cases. In these 106 cases, there were 143 tumors , with edema in the arcuate white matter (73% ), the external capsule (33 % ), the interna l capsule (12% ), and the corpus callosum (14% ). In contrast , only four of the 339 cases of infarct had edema in the white matter pathways. In addition , 260 (77% ) of the infarct cases had edema in both gray and white matter and 98% had at least gray matter involvement, while only two of the tumor cases had any gray matter edema . White matter pathway involvement with respect to tumor site is useful in differentiating tumor and infarct edema.

Received July 23, 198 1 ; accepted aft er revision December 2. 198 1 .

' Deparlm enl o f Di ag nosti c Radiology. Rochesler General Hospital. 1425 Porll and Ave., Roc hester . NY 1462 1 Address reprinl requ esls to A. Monajali .

2Deparlm enl of Path ology. Roc hester General Hospital. Roc hester , NY 1462 1 .

AJNR 3:251-255, May/ June 1982 0 195- 6 108 / 82 / 0 3 0 3-0 25 1 $ 0 0. 00 ? Am eri can Roentgen Ray Society

The computed tomographi c (CT) appearance of cerebral edema due to intrac ranial tumors has been described as an area of low attenu ation , usu ally c onfin ed to the topography of the whit e matter [1 , 2]. In c ontrast , th e edema assoc iated with cerebral isc hemi a appea rs on CT as a typi cal low density involving both th e gray and the adjoining white matter [3-6].

The aim of this study was to analyze th e CT scans of brain tumors and ce rebral infarcts to evaluate the specifi c ity of th e differenti al pattern o f th e edema in distingu ishing neoplastic lesions from acut e ce rebral isc hemi a. Spec ial attenti on was given to the distribution of edema along recognizable white matter pathw ays.

Materials and Methods

A total of 33 9 c rani al CT scans from pati ent s w ith ce rebral infarc ti on and 155 CT sca ns from pati ent s with supratentori al tum ors co nstituted th e CT materi al for thi s stu dy . Foll owup CT scans demonstrating th e evolution of th e white matter edema assoc iated with a tumor or regressio n of th e edema aft er tum or th erapy or surgery we re in c luded . Th e CT sca ns that showed sign s of assoc iated hemorrh age we re exc luded because hemorrh age in brain ti ss ue per se cou ld provo ke whit e matt er edema (7) and thu s wo uld co mpli cate th e pi c ture of th e ed ema produ ced by infarcts or tumors. Only CT scans th at were obt ain ed w ithin th e first 2 week s after th e infarct we re inc luded to assure th at onl y th e edematous ph ase o f th e di sease wa s analyzed [8 j.

All th e CT sca ns except one we re taken w ith an EMI 500 5 sca nn er, usin g a 160 x 160 or 3 20 x 32 0 matri x. Th e scans we re usuall y taken both be fore and after intravenous infu sion o f co ntrast materi al. Th e CT abso rpti on va lues of edematous reg ions on 12 pa ti ent s with infarcts and 12 pati ents w ith tum ors we re meas ured usin g an area o f int erest rangin g from 52 to 308 pi xe ls. Th e att enu atio n number va ri ed fro m 11 .2 to 17.4 CT un it s ( - 500 to +500 sc ale) in th e tumor edema and from 10.2 to 16 .2 unit s in brain infarc ts.

All pati ent s w ith ce rebral infarc ti on had th e diag nos is suggested by th e typi ca l c linica l presentati on and th e natural hi story o f th e di sease. An giog raphy was perform ed in a sma ll number of cases. Aut opsy foll ow-up was onl y avail abl e in a few cases in whic h gross b rain swelling was evident.

Brain tumors co nsisted of gli al tum ors, menin giomas, metastati c tum ors, pit uitary tum ors w ith suprasell ar ex tension , and one pin ealoma. Gross and mi crosco pi c ph o tographs from

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autopsy and surgical biopsy material were selected to correlate the gross anatomic findings with the CT scans and to illustrate tumor ede m a.

Th e areas of edema were evalu ated in term s of involvement of the gray and white matter versus in vo lvement of isolated white

A

8

matter only. Special attention was given to th e presence of th e edema along th e ce rebral white matter pathways, whi c h were read ily recog niza bl e on CT. They in cluded th e ex ternal and internal ca psules, corpus ca ll osum, and arcuate wh ite matter [9).

Results and Discussion

Infarcts

We found, as have others [3-6], that edema due to an infarct usually affected both the cortex and the underlying white matter (fig . 1). The gray matter was involved in 98% of the cases. In 6 cases, only a focus of deep white matter edema was present. Only 2 cases were accompanied by an edematous internal capsule (fig. 2), possibly due to ischemic involvement [1 0] rather than extension of the infarct (table 1 ).

The process of edema in brain ischemia has been said to begin as a cytotoxic event characterized by intracellular accumulation of fluid and to be followed by vasogenic edema [8]. Others have shown vasogenic white matter edema surrounding a hemorrhagic infarct in postmortem histologic specimens and correlated these cases with CT [7, 11]. The edema is indistinguishable by CT from that seen with intracerebral hemorrhage. In nonhemorrhagic infarcts, se ld om has edema been defined in tissue that is not part of the infarct [11]. This confirms our CT observations that ischemic edema seldom, if ever, migrates to the neighboring white matter pathways.

c

D

Fig . 1.- I sc hem ic cerebral edema compared with edema of tumor. A and B . Postcontrast CT scan from 56-year-o td hypertensive man who had lett cerebral st roke 1 day before CT sca n. Edema of both gray and white matter. C and D. Postcontrast CT scan from different patient with left parietal contrast-enhanc ing tumor (m etastatic carc inoma from lung). Subcorti ca l white matter edema digitating toward cort ex.

Tumors

Forty-seven cases (30%) of the tumor cases showed no edema (table 2). In two cases the tumor edema diffusely involved both the white and overlying gray matter (fig . 3) . In 106 (68%) of the cases, white matter pathway edema with no g ray matter involvement was seen. The localization and extension of the edema along spec ifi c fiber tracts are summarized in table 3 . A few cases with involvement of the superior long itudinal fasciculus [9] (fig . 48) are not included in the tabl e.

In th e CT differentiation of tumor edema from that of a cerebral infarct, edematous involvement of the following

2

3A

38

Fig. 2. - lschem ic edema with involvement of internal ca psul e. Postcontrast CT scan on admi ssion of 78-yea rold hype rt ensive man with typical histo ry of right hemisph eric stroke 9 days before CT scan. Diffuse low density in distribution of middle cerebral artery with involvement of entire cou rse of internal capsule (arrows).

Fig . 3. -Atypica l pattern o f peritumor edema. A and B . Postcont rast CT scans. Enhanc ing lesions (metastatic carcinoma from breast). Ed ema diffu sely involves both wh ite and overlying gray m a t t e r.

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TABLE 1: CT Characteristics of Cerebral Edema in 339 Cases of Recent Nonhemorrhagic Infarct

Site of Edema

N o.

Cortical gray matter and underlying wh ite

matter

260

Both cortical surface and basal ganglia

52

Basal gang lia only

21

White matter (focal involvement) with no in-

vo lvement of cort ical surface

6

Total

339

White matter pathways:

Internal capsule

2

Corpus callosum (unilateral)

2

Other white matter pathways (isolated

involvement)

0

Cases (% )

(77) (15)

(6)

(2) (100)

Note. -In 147 cases (43 %), the edema pattern was homogeneous and well defined.

A

B

TABLE 2: Cerebral Edema in 155 Cases of Supratentorial Tumors

No. Cases

Type of Tumor

No Edema

White MaUer Edema

Cont ig u o u s and White M alter Edema

Glial neoplasm

10

Meningioma

13

Metastatic tumor

18

Pituitary tumor with supra-

sellar extension

5

Pinea loma

40

0

14

0

51 ?

2

1

0

0

0

Total no. of cases

47 (30 % ) 106 (68 % ) 2 (1 % )

? In multiple les ions, on ly those lesions that showed the typical edema were cou nted.

c

o

white matter pathways appeared most useful because of their CT recognizability:

External capsule. This narrow white matter tract with the claustrum and extreme capsule is located between the gray matter of the insular cortex on its lateral aspect and the gray matter of the lenticu lar basal ganglia on the medial aspect [9] (fig. 4C). The external capsule became readily visible by CT when involved by the extension of the white matter edema. This was common in temporo-parietal tumors with anterior extension of edema (figs. 4 and 5) and frontal tumors with posterior extension of the edema (figs. 6 and 7) (table 3).

Internal capsule. Involvement of the posterior limb of this tract by the extension of tumor edema usually accompanied the external capsular edema in the case of posterior localization of tumors (figs. 4 and 5). Edema along the anterior limb was seen in only one case (fig . 7).

Corpus callosum. Though involvement of the corpus callosum by the extension of tumor edema from adjacent tissues was not unusual (table 3), edema extension to the contralateral hemisphere without direct tumor invasion was not encountered. It has been suggested that cerebral edema fai ls to cross the corpus callosum [12]. This has also been reported in a CT investigation of experimental cerebral edema [13]. Our findings support the view that the corpus

Fig . 4. -Exte nsion of ede ma in posterior hemispheric tumor . A and B , Postcontrast CT scans. Enh anc ing lesion (g lioblastoma multiforme) in lett pari etooccipital reg ion (open arrows). A , Edema along extern al capsul e (short arrow) and posterior lim b of intern al capsu le (long arrow). B , Edema along course of superi or longitudinal fasciculus extending toward frontal lobe (closed arrows). Pati ent died from bronchopneumon ia 4 weeks after su rge ry and treatm ent. C and D, Autopsy brain sections in same plane as CT scans. Edematous white matter tracts on A and B anatomica ll y co rr elated with their

locations on brain sect ions 1, 3 , and 8. 1 = posterior limb and 2 = ant eri or

limb of internal capsul e; 3 = exte rn al capsule; 4 = head of ca udate nucleus; 5 = lenticu lar nuc leus; 6 = gray matter of in su lar cortex; 7 = tha lamus: 8 = superi or longitudinal fasciculus.

callosum seem ingly exh ibits relative resistance to th e extension of cerebral edema from one hemisphere to the other. When it is invaded by tumor, however, bilateral edema can occur. A continuous low-d ensity lesion between th e hem ispheres with or without contrast enhancement corre lated with tumor invasion across the midline in several cases (fig. 8).

Arcuate white matter. Subcortical white matter contains fibers that interconnect adjoining gyri and enter the deeper white matter during their course [9]. Spread of the edema along this zone of white matter and sparing of the overlying gray matter [14] lead to the formation of a digitate pattern of low density along the brain cortex on CT (fig . 1C). Thi s appearance was the most common finding in the case of tumor edema (tabl e 3). Infrequently, a part of the white matter directly adjacent to a tumor did not show the typical

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TABLE 3: Tumor Site and Edema Extension in White Matter Pathways: 143 Tumors in 106 Cases

Tumo r Si le (No. Lesio ns)

Frontal (46) Pari etal (53 ) Temporal (32) Occ ip ital (10) Th alami c (1) Suprasell ar (1)

Total (% ) 143 (100)

No. Tumors with Edema in White M atler Pat hways

Arcuate While Maller

17 51 24 10

1

104 (73)

Ext erna l Ca psu le

26 8

11 2 0 0

47 (33)

Int erna l Capsu le

1 6 9 1 0 0

17 (1 2)

Co rpus ca ll osu m

11 4 5 0 0 0

20 (14)

NOTE.- Tumors included multiple metastatic tumors.

5

6A

68

7

Fig . 5.-Ex tension of edema in te mpo rat tumo r. Postcontrast CT scan in patient wi tl, t mporal lobe tumor (m etastati c ca rc inoma from colon). Edema along ex tern al apsu le (bla ck arro w) and posteri or limb of intern al capsule (wh ire arro w) .

Fig . 6 .-Ex tension of frontal tumor edema . A and B, Postco ntrast CT

scans. Enh anc ing solitary metastatic ca rc in oma fr om lung with massive ede ma. Extension of edema along ex tern al capsu le (arrow).

Fig. 7.-Prog ression of frontal tum or edema. Postco ntra st CT sca n. Tumor with enhancing rim (astrocytoma). Edema ex tensio n towa rd exte rn al capsul e (shorr arrow) and anteri or limb of intern al capsu le (long arrow).

radiating pattern of white matter edema (fig . 68) , apparently as a result of th e severity of ede ma and assoc iated gray matter involvement. Neve rth eless, away from th e lesion distin ctive w hite matter ede ma was evide nt.

Th e brain edema provoked by intrac rani al tumors occurs princ ipally within th e white matter due to an alteration in vasc ular perm ea bility with resultant leakage of intravasc ul ar fluid into the extracellular spaces [15]. The pattern of the edema propagation within the cerebral white matter has been shown in vivo by CT in experimental animals [13 , 16]. In man th e investig ations have been limited to autopsyCT correlations [1, 7]. In this study, follow-up CT scans showed th at edema could progress o r regress along white matter tracts within one hemisphere. The topographic visualizatio n of th ese pathways on CT proved usefu l in differentiating tumor edema from ischemic edema.

Fi . 8 .- Tumor (witho ut edema) across corpu s callosum. A , Postcontrast CT ca n. Low density lesion with faint marginal en hancement extend ing acro s splenium . Patient died 2 days after CT sca n and was autopsied . B , Corr sponding brain section . Glioblastoma involving left parietal lobe and c rossing corpu s c allosum . No appreciab le edema.

ACKNOWLEDGMENT

We th ank Don na Med in g and Bern ie T . Smith for assistan ce in manuscript preparati on.

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