Computed Tomography in Head Trauma 1

Computed Tomography

Arthur B. Dublin, M.D., Barry N. French, M.D., F.R.C.S.(C), and John M. Rennick, M.D. Retrospective analysis of 200 cases of documented head trauma demonstrated an accuracy approaching 100% In the diagnosis of Intra- and extracerebral collections of blood. Caution must be exercised In the evaluation of trauma 1 to 5 weeks old, since subdural hematomas have the same density as normal brain tissue, and angiography may be necessary. The clinical diagnosis of bralnstem contusion Is associated with a remarkably high level (54 %) of surgically correctable lesions. The use of computed tomography In the evaluation of other traumatic Intracranial lesions Is discussed. INDEX TERMS: Brain, hemorrhage. Computed tomography, cranial, 1[0] .1211 • Head, wounds and injuries (Skull, Intracranial effects of trauma, 1[0] .430) • Meninges, hemorrhage

Radiology 122:365-369, February 1977

Table I:

tomography (CT)represents a great advance in the diagnosis of a wide variety of intracranial lesions, particularly those secondary to head trauma. While angiography is often time-consuming and cannot differentiate between intracerebral mass lesions such as hematomas and contusions, CT gives a specific diagnosis in a minimum amount of time; for this reason, it has almost completely replaced angiography for acute head trauma at this institution. We wish to present the largest series of traumatic pathology in the literature to date (4, 5, 7, 10), with a discussion of the CT findings of each entity. OMPUTED

C

CT Scan Abnormalities in 112 Patients*

Contusion/edema/mass effect Subdural hematoma Intracerebral hematoma Ventricular enlargement Skull fracture Epidural hematoma Intraventricular hemorrhage Eye trauma Pneum ocepha Ius Infection

45 41 (55 lesions) 20

18 8 5 4 2 2

1

*30/112 (27%) had multiple lesions.

represents approximately Ys of the fractures seen by conventional radiography. Four were depressed and/or compound. A linear fracture by itself may not be of great clinical importance. In fact, subdural lesions may occur as frequently with fractures as without (11); in Galbraith and Smith's series, 19% of acute intracranial hematomas occurred without fracture (3). The real value of CT in fracture cases is the detection of surgically correctable intracranial lesions such as hematoma or the evaluation of depressed skull fractures (Fig. 1, A), or intracranial bone fragments secondary to missile wounds (Fig. 1, B and C). With the advent of the 320 X 320 matrix and shortened scan times, skull fractures (especially basal ones) may be detected and evaluated more readily.

MATERIAL

1,600 consecutive CT examinations (160 X 160 matrix) performed on 1,250 patients were reviewed. Of these, 200 patients with documented head trauma form the body of this report; this is approximately Y3 of the 620 patients with head trauma seen in the emergency room at this institution. Scans were abnormal in 112 cases (56 % ) {TABLE I}. Each diagnosis was confirmed by surgery or clinical follow-up. No correlation between radionuclide studies and CT was possible, since the former are rarely performed at this institution in cases of head trauma. Motion artifacts were minimized by the routine use of patient motion control on all levels and intravenous Valium sedation. Although New has stated that general anesthesia may occasionally be required to reduce motion artifacts to a tolerable level (7), we have not generally encountered this problem.

ExtracerebraI Hematomas (a) Subdural Hematoma: Fifty-five lesions were detected; of these, 41 (66 % ) were unilateral and 14 (34 % ) were bilateral (i.e., 28 lesions). Thirty-seven lesions exhibited increased density, 5 were isodense, and 13 demonstrated decreased density in relation to normal brain tissue. This is comparable with data published by Paxton and Ambrose (10). Subdural hematomas were found in 0.5% of patients with head injuries in the neurosurgical literature (11). In our series, they represented 8.7% of the 620 cases of head injury seen in the emergency room. Some individuals with postconcussion headaches demonstrate small subdural

RESULTS

Because of the complexity of lesions found in head trauma, each entity will be discussed separately. Where possible, appropriate cross references and correlations between each entity will be made. Fractures

Eight fractures were detected by CT in our series. This

1 From the Departments of Diagnostic Radiology, Sections of Neuroradiology (A.B.D., J.M.R.) and Neurosurgery (B.N.F.), Sacramento Medical Center, Sacramento, Calif., and University of California School of Medicine, Davis, Calif. Accepted for publication in August 1976. Presented in part at the Annual Meeting of the American Association of Neurological Surgeons, San Francisco, Calif., April 4-8, 1976. sjh

365

366

ARTHUR

B.

DUBLIN AND OTHERS

February 1977

Fig. 1. A. There is a depressed frontal skull fracture (arrowhead) with a small area of underlying cerebral cortical hemorrhage. B. A tract of bone and hemorrhage (arrowhead) in the temporal lobe, secondary to a gunshot, is well seen. C. Same case as B, showing computer artifact spray from metallic fragments residing just underneath the posterior occipital portion of the cranial vault. 90

~ 80 ;;::;

.~

70

0-

;; 60 I-

Z 50 ::::>

I • •

•

• •

· ·

•

•

a 40 ...J

~ 30 en ~ 20 §? 10

•

lor less

7

14

•

• •

21

• • 28

• 35

42

TIME FROM TRAUMA (days)

Fig. 2. Relationship between subdural hematoma density and time after trauma. Areas having a density of 30-50 H may be isodense to normal brain tissue. Notice the fairly wide scattering of points with time, thus making statements as to the age of a subdural hematoma often unreliable.

hematomas on CT. Four of our patients were stable clinically, and CT follow-up showed resolution of their lesions without surgical intervention. These patients would not have had angiography prior to CT. Thirty cases of subdural hematoma are shown graphically in Figure 2. Fifteen of the original 55 lesions were eliminated from the study due to a lack of reliable history with regard to elapsed time between injury and CT scan. Two cases were omitted because of defective computer tape. Several others were omitted because the hematoma appeared after surgery, raising the question of whether these lesions were residual from previous trauma or due to the surgery itself. As the graph shows, there is an overall correlation of the average density of the subdural hematoma with age. However, considerable variation does exist; and aside from hematomas of very high or low density, it is often difficult to make any accurate statement as to the age of a particular lesion. New hemorrhage into an old subdural lesion is well known in the neurosurgical literature (11). Thus a chronic subdural hematoma may increase in density, giving the false appearance of an acute process. In addition, the literature is somewhat confusing with regard to subdural hematomas: identical lesions have been called

subacute in one article and chronic in another (1, 10). Neurosurgeons refer to an acute subdural hematoma as a lesion less than 24 hours old, subacute if 2 to 10 days old, and chronic if older than 10 days (11). We simply describe a subdural hematoma as an extracerebral collection of fluid whose density is greater than, equal to, or less than that of normal brain tissue. It is interesting to note that the average density in these 30 cases increased from 74 to 78 Hounsfield units (H) (or from 37 to 39 EMI units) in the first 3 days post-trauma. Norman believes the density of a subdural hematoma is most directly related to its hemoglobin content (9). With clot retraction, absorption of fluid, and increased hemoglobin concentration, it is possible that the absolute density of such lesions may indeed increase over the first few days. Rebleeding into an acute subdural hematoma would not be expected to increase the density of the lesion, since, on the average, it is already at the maximum level. It is possible that a tremendous increase in the overall volume of a lesion might have some effect on raising the density; however, this did not seem to be the case in our series. A typical high-density subdural hematoma is illustrated in Figure 3, A. Such lesions are typically crescentic and extend over a fairly large area of the brain, in contrast to an epidural hematoma, which tends to be localized and lenticular in appearance. Figure 3, C represents a typical subdural lesion of decreased density. Figure 4, A shows a subdural lesion whose density is decreased anteriorly and increased posteriorly; the layering between the two regions changes with a shift in the position of the bony calvaria as demonstrated in Figure 4, B, probably related to gravitation and sedimentation of corpuscular elements to the most dependent portion of the tumor. Figure 3 B demonstrates a typical isodense subdural lesion. As shown in Figure 2, the density of the hematoma may become isodense to normal brain tissue during the period from approximately 1 to 5 weeks post-trauma; thus such a lesion may be misleading, presenting only as a mass effect. One of our cases (2) was initially misdiag-

Vol. 122

367

COMPUTED TOMOGRAPHY IN HEAD TRAUMA

Computed Tomography

Fig. 3. Subdural hematomas. A. Typical high-density subdural lesion (arrowhead) with associated shift of the ventricles. B. A small layered subdural hematoma (arrowhead) produces very little mass effect on the lateral ventricles, due to an isodense contralateral subdural hematoma which was confirmed by angiography. C. Two large subdural lesions with decreased density and associated with moderate hydrocephalus (arrowheads).

Fig. 4. Layered subdural hematoma. A. There is a large subdural hematoma (arrow) and a smaller contralateral one with shift of the ventricles. The large tumor is layered, most likely due to settling of corpuscular elements to the most dependent portion. B. Same patient as A. The head has been tilted 45 0 • Notice the shift in the layered hematoma (arrow). The apparent increase in the size of the contralateral lesion is due to a computer artifact.

nosed: the patient presented with a clinical history suggesting a neoplasm, but a non-enhancing mass effect was demonstrated on the CT scan and a large isodense subdural hematoma was confirmed by angiography. Newton (8) has suggested that contrast enhancement between an isodense subdural hematoma and the normal brain tissue, produced by a chronic membrane, is helpful in the differential diagnosis, but we have not seen this phenomenon in our series of 5 isodense subdural hematomas (plus 4 additional cases observed since the original compilation of data) employing 300 ml of Conray-30 with immediate and delayed scans. Approximately 45 % of subdural hematomas are associated with other abnormalities (predominantly cerebral contusion and hematoma) on the CT scan, which explains why evacuation of an extracerebral collection of blood does not always produce the expected dramatic clinical improvement. CT is helpful not only in determining the location and extent of a subdural hematoma but also in

Fig. 5. There is a small, thin subdural hematoma (white arrow) as well as one in the temporal lobe (black arrow). There has been a moderate shift of the lateral ventricles.

detecting and differentiating intracerebral masses such as edema or another hematoma; a case in point is the small temporal-lobe hematoma associated with a subdural hematoma on the same side shown in Figure 5. The volume of a subdural lesion seen on the CT scan is often less than that revealed at surgery, since most such lesions are found over the convexities of the brain (7); as one moves higher the bony calvaria adds to the overall absorption coefficient of the subdural lesion, thus artifactually decreasing its observed volume. (b) Epidural Hematomas: Five epidural hematomas (4 supratentorial and 1 infratentorial) were demonstrated. Such lesions are usually lenticular and exhibit high density in relationship to normal brain structures. They are also usually well localized to a particular portion of the cranial vault. Typical supra- and infratentorial hematomas are ilI

368

ARTHUR

B.

DUBLIN AND OTHERS

Fig. 6. Epidural hematoma. A. Classical lenticular temporal epidural hematoma (arrow) with associated shift of ventricular structures. B. A large epidural hematoma in the posterior fossa (arrow) is well shown. A small postoperative residual frontal hematoma is also present, associated with hydrocephalus of the lower third ventricle and temporal ventricular horns secondary to the epidural mass effect on the fourth ventricle and aqueduct.

Fig. 8. Cerebral contusion. Notice the slight shift of the anterior horns of the lateral ventricles as the result of a temporal contusion (arrow).

lustrated in Figure 6. The patient in Figure 6, 8 fell, injuring his occiput, and was considered to have a temporal lobe contusion. When he deteriorated, CT showed the expected frontal temporal lesion as well as an unexpected cerebellar epidural hematoma. Removal of the latter lesion resulted in dramatic clinical improvement. Epidural hematomas are particularly amenable to examination by CT, since the interval between trauma and surgery is of utmost importance and angiography may be too time-consuming.

Intracerebral Hematoma and Contusion Twenty intracerebral hematomas were detected, of which 16 (80 % ) were unilateral and 4 (20 % ) were bilateral or multiple. Sixty per cent were associated with other lesions, usually extracerebral collections of blood. Angi-

February 1977

Fig. 7. Intracerebral hematoma. A. A large insular and basal ganglia hemorrhage is well shown (arrow). Notice the mass effect on the calcified pineal gland and ventricles. B. Same case as A, two weeks later. The area of hemorrhage (arrow) appears to have decreased considerably in size; however, the mass effect on the ventricles and calcified pineal gland is essentially unchanged. The increase in ventricular size is due to communicating hydrocephalus.

Fig. 9. Intraventricular hemorrhage. A. Post-traumatic cerebellar hemorrhage (white arrow) with displacement of the blood-filled fourth ventricle (black arrow). B. Same case as A, showing noncommunicating hydrocephalus of the lateral and third ventricles with intraventricular third (white arrow) and lateral ventricular hemorrhage near the foramen of Monro (black arrow).

ography may demonstrate a mass effect, but CT can determine whether this mass effect is simply a contusion or a well-defined hematoma that can be surgically removed. Figure 7 demonstrates regression of a typical intracerebral hematoma with time. Note that a considerable mass effect is still present on the second scan (taken 2 weeks later) even though the left temporal intracerebral blood has apparently been reabsorbed. Surgical exploration at this time revealed a Iiquified hematoma corresponding in size to that suggested on the original scan. It is apparent that a hematoma may be stable in size, but due to degradation of its various elements its CT density may decrease with time, giving an artifactual impression of resolution. The change in mass effect, not the change in density, is the most important criterion in the evaluation of an intracerebral hematoma (6). Forty-five cases of contusion and/or edema were

Vol. 122

369

COMPUTED TOMOGRAPHY IN HEAD TRAUMA

demonstrated (TABLE I). Edema presents acutely as an area of mass effect with slight marked to decreased density in relationship to normal brain tissue. Contusion presents as a "salt and pepper" appearance representing areas of small punctate hemorrhage intermixed with normal or edematous brain tissue. Forty cases of contusion and/or edema were evaluated with regard to time after trauma, with scans obtained within 24 hours after injury in 17 of the 25 cases presenting as contusion and later in 12 of the 15 cases presenting as edema. Twenty-two cases of contusion and/or edema (55 %) were associated with other lesions. Thus whether one describes a lesion as contusion or edema is most likely related to how soon after injury it is observed. A typical contusion is shown in Figure 8.

Intra ventricular Hemorrhage At one time intraventricular hemorrhage uniformly indicated a grave prognosis. With the advent of CT, intraventricular hemorrhage (Fig. 9) is now appreciated more frequently, leading to earlier ventricular drainage at this institution. It also appears that some individuals with previously unsuspected intraventricular hemorrhage may tolerate bleeding of this type without drainage and without uniform mortality, particularly infants and children. In those that do survive, hydrocephalus of some degree, either transient or more permanent, occurs in approximately Ys of cases.

Ventricular Enlargement Eighteen cases of ventricular enlargement were detected. In 5 it was the only CT finding, while 13 had associated lesions. Two categories of ventricular enlargement are apparent from our study. The first is seen in generalized brain edema. Initially one observes tiny, slit-like ventricles. With time and resolution of the swelling, the ventricular size, while enlarging in a relative manner, actually returns to an absolute normal configuration (5). The second category of patients represents true hydrocephalus, either noncommunicating (Fig. 9) or communicating; the latter is probably due to blockage of normal CSF absorptive pathways by subarachnoid blood. Follow-up is incomplete but suggests that the communicating hydrocephalus is transient and a shunt is not required.

Brainstem Contusion Twenty-four patients presented with a typical clinical pattern of "brainstem contusion," including various degrees of decerebrate activity. In the past, there has been a tendency to assume that no surgical lesion is present in such cases; however, 13 of our patients (54 % ) had surgicallesions (6 contusion/edema, 5 subdural hematomas, and 2 intracerebral hematomas). Death was averted in 4 of them, of whom 1 showed good improvement, 1 demonstrated moderate improvement, and 2 remained vegetative. The 9 remaining patients exhibited various degrees

Computed Tomography

of recovery, but it is difficult to assess whether the surgery had any real effect on the eventual outcome. Only 4 patients with brainstem contusion had a negative CT scan. Thus the neurosurgical connotations of the term "brainstem contusion" may have to be revised.

SUMMARY In the vast majority of cases, angiography is no longer necessary in cases of acute head trauma, the only exception being in the evaluation of isodense subdural hematomas. Differentiation between edema and a surgically correctable lesion such as a well-defined hematoma is greatly improved with CT. This technique also permits earlier detection of intraventricular hemorrhage; with intraventricular drainage, the survival rate may be improved. Correlation of the density and temporal course of a subdural lesion can be misleading. Thus we have eliminated the terms acute, subacute, and chronic and prefer instead to refer to extracerebral collections of fluid of (a) increased density, (b) isodenstty, or (c) decreased density in relation to normal brain tissue. Subdural hematomas may actually increase in density during the first 1 to 3 days post-trauma. Improvement of intracerebral hematomas should be based on changes in mass effect, not CT density. "Brainstem contusion" may be associated with a surprisingly high number of surgically correctable lesions. Department of Diagnostic Radiology University of California-Davis School of Medicine 4301 X sr., Rm. 214 Sacramento, Calif. 95817

REFERENCES 1. Ambrose J: Computed transverse axial scanning (tomography): Part 2. Clinical application. Br J Radiol 46:1023-1047, Dec 1973 2. Dublin AB. Rennick JM, Sivalingam S: Failure of computerized axialtomography to demonstrate a chronic subdural hematoma. Surg Neurol 6:23-24, Jul 1976 3. Galbraith S, Smith J: Acute traumatic intracranial haematoma without skull fracture. Lancet 1:501-505, 6 Mar 1976 4. Levander B, Stattin S, Svendsen P: Computer tomography of traumatic intra- and extracerebral lesions. [In] Lindgren E, ed: Computer tomography of brain lesions. Acta Radiol (Suppl 346):

107-118, 1975 5. Merino-deViliasante J, Taveras JM: Computerized tomography (CT) in acute head trauma. Am J Roentgenol 126:765-778, Apr

1976

6. Messina AV, Chernik NL: Computed tomography: the "resolving" intracerebral hemorrhage. Radiology 118:609-613, Mar 1975 7.

NewPFJ, ScottWR: Computed Tomography oftheBraln.and Orbit (EMI Scanning). Baltimore, Williams & Wilkins, 1975, Chapt 18, pp 33-34; Chapt 26, pp 287-306 and 426-439 8. Newton TH: Personal communication, 1976 9. Norman D: Current status of computerized tomographic brain scanning. [In] Margulis AR, Gooding CA, ed: Diagnostic Radiology. San Francisco, Univof California, 1976, pp 813-833 10. Paxton R,Ambrose J: The EMI scanner. A briefreviewof the first 650 patients. Br J Radiol 47:530-565, Sep 1974 11. Youmans JR, ed: Neurological Surgery. Philadelphia, Saunders, 1973, pp 960-968 and 1025