Overall, trauma represents the most fre- quent cause of death and permanent disability, with an annual incidence of 0.2-0.3% and with peak incidence in the 15-24 year age band (1).
In the United States alone, approximately 2 million head injuries occur annually, of which some 10% are fatal. Approximately 5-10% of survivors experience neurological deficits of varying degrees (1, 4, 5). The most common causes of trauma are road accidents, firearm in- juries, falls and assaults.
The brain lesions resulting from cranial trauma are usually classified as being either primary or secondary, according to how di- rectly they correlate to the traumatic event (4, 20, 22, 29). Primary lesions include fractures of the skull, extraaxial haemorrhages (e.g., epidural haematoma, subdural haematoma and subarachnoid haemorrhage) and intraaxial le- sions (e.g., diffuse axonal injury [DAI], corti- cal contusion, deep grey matter injury and in- traventricular haemorrhage). Secondary lesions are constituted by pathological processes that occur due to the brain’s response to the pri- mary trauma and are generally more clinically devastating than primary ones. Secondary brain lesions include internal cerebral herniation, dif- fuse cerebral oedema, infarction and secondary haemorrhage (4, 20, 22, 29). Yet other lesions are the result of sequelae of severe cranial trau-
ma; these changes are represented by pneu- mocephalus, CSF fistulae, leptomeningeal cysts, lesions of the cranial nerves, diabetes in- sipidus secondary to pituitary axis injury, cor- tical atrophy and encephalomalacia (9).
In recent decades, considerable progress has been made in the diagnosis and management of cranial trauma patients. The application of Computed Tomography (CT) has resulted in a revolution in head injury diagnosis, making it possible to detect cases suitable for surgical treatment in a rapid, non-invasive manner (6, 7, 11, 12, 14). Its near-universal availability in hos- pitals, the speed with which examinations can be conducted, the general absence of con- traindications to emergency patient scanning, and its sensitivity in diagnosing haemorrhagic collections make CT the imaging technique of choice for the initial assessment of patients with acute head injuries (4, 22, 32, 33). Further ad- vantages offered by this technique are found in its high spatial resolution allowing the possibil- ity of documenting even the thinnest fractures and those located in critical positions such as the base of the skull or the temporal bone, and in identifying small splinters of metal or tiny fragments of bone displaced into the cranial cavity (24, 31). The drawbacks of CT include its limited sensitivity in studying small traumat- ic lesions in the inferior posterior fossa or else-
2.1
CLINICAL AND DIAGNOSTIC SUMMARY
G. M. Giannatempo, T. Scarabino, M. Armillotta
where adjacent to the base of the skull, these limitations being principally due to bone arte- facts generated by the technique. CT also has a relatively low sensitivity in the identification of small non-haemorrhagic lesions of the cerebral cortex, white matter and brainstem (4, 10, 20, 21, 23). However, these limitations do not pre- vent CT from identifying the nature, size and site of the most clinically significant acute phase traumatic brain lesions and from decid- ing whether or not surgical intervention is re- quired (4, 22, 32, 33).
Magnetic Resonance Imaging (MRI) plays a limited role in the acute phase of cranial trau- ma, given its higher cost, relatively limited availability, longer examination times, lower sensitivity in recognising fractures, patient con- traindications (internal electronic pacemakers, etc.) and the practical difficulty of effectively monitoring patients with severe clinical condi- tions requiring external support devices (4, 8).
MR is also limited by problems encountered in recognising acute phase haemorrhages (e.g., oxy- and deoxyhaemoglobin within hyperacute haemorrhages) and small bone fragments dislo- cated into the skull. The use of MR in emer- gency situations also entails certain intrinsic risks, for example those linked to the difficulty in ascertaining the presence of electronic pace- makers in unconscious trauma patients.
Technological progress has to some extent reduced the drawbacks associated with long examination times and the difficulties in using instruments to monitor the patient’s vital pa- rameters during the MR examination. The use of fast scanning sequences (e.g., fast spin-echo, gradient-echo, echo-planar) has considerably reduced the amount of time required to per- form MR studies, to the point where it is now possible to perform a basic MR scan in less than ten minutes. This scan protocol may in- clude a T1-weighted spin-echo sequence, a T2- weighted fast spin-echo sequence and a T2*- weighted gradient-echo sequence, the latter be- ing particularly sensitive to haemorrhagic ex- travasations. It must also be pointed out that considerable progress has been made in the de- velopment of new non-ferromagnetic alloys employed in the manufacture of electronic
medical instruments used for vital parameter monitoring and life support, so that they are now compatible with MRI (4, 8).
MRI has greatest diagnostic sensitivity in many of the very cases in which CT encounters some of its greatest limitations. Given its greater sensitivity in the diagnosis of diffuse axonal injury (DAI), small cortical contusions and primary and secondary traumatic brain- stem lesions, MRI is also used as a complement to other imaging methods in the acute phase of trauma, especially in patients with clinical signs and symptoms but with minor or absent CT findings (4, 20, 21). MR examinations are also suitable in subacute and chronic phase cranial trauma for the purpose of evaluating secondary lesions and other sequelae.
In the area of cranial trauma diagnosis, digi- tal angiography currently plays only a marginal role and is principally utilized for cases in which traumatic vascular lesions are suspected (e.g., vascular dissections, lacerations, occlu- sions, pseudo-aneurysms and arteriovenous fis- tulae).
NEURORADIOLOGICAL PROTOCOLS
Although any diagnostic approach must be tailored to suit the requirements of each pa- tient, some general guidelines can be identified to aid in the establishment of which technique is most suitable. Defining an efficient and effi- cacious diagnostic protocol requires compro- mising between the choice of a technique guar- anteeing high diagnostic sensitivity and the lim- itations imposed on the number and complexi- ty of the diagnostic examinations that can be performed.
Although CT is the examination technique
of choice in cranial trauma, not all authors
agree on the necessity of performing CT in
asymptomatic patients with previous minor
cranial traumatic incidents, the need for com-
plementing CT examinations with MR scans in
patients with intermediate or serious head in-
juries and the real contribution of traditional
skull x-rays in patients with head injuries of any
degree.
The choice of a specific imaging technique to be employed must be preceded by a defini- tive clinical evaluation of the patient. The most commonly used method for evaluating head in- jury patients is the Glasgow Coma Scale (GCS), based on a progressive score attributed to the patient’s ability to open his/her eyes, perform movements and verbally respond to external stimuli (13, 22, 28) (Tab. 2.1). The degree of severity of the trauma is classified in three cate- gories according to the GCS score: mild trauma for a GCS score of 13-15; moderate trauma for a GCS score of 12-8 and severe trauma for GCS scores lower than 8.
Patients with mild head trauma (GCS 13-15) usually complain of headaches and transient mental confusion or disorientation (30) and, by definition, they do not exhibit persistent prob- lems with consciousness (30). Some authors hold that it is sufficient to keep patients with such mild degrees of cranial trauma under ob- servation, and furthermore that they do not re- quire imaging studies (18). On the contrary, others believe that mild head injuries warrant at a minimum a CT examination, because despite the paucity of symptoms, traumatic brain le- sions may be observed (19, 27). In a recent sur- vey conducted on 1,170 mild cranial trauma pa- tients (GCS = 15), CT demonstrated the pres- ence of brain lesions in 3.3% of cases, of which 18 in number were intracranial bleeds; in 1.8%
the CT examination altered the treatment pro- gramme, and in four cases surgery was per- formed (19). The same authors also stressed the prognostic value of a negative CT examination:
in the same patient sample, none of the patients with negative CT scans experienced clinical de- terioration. The authors therefore believe that it is not necessary to keep asymptomatic mild head trauma patients under observation in the setting of negative CT findings (19). Patients with mild trauma can reveal skull fractures, as well as extraaxial and intraparenchymal haematomas, lesions that are usually clearly documented on CT images. Although MR is slightly more sensitive than CT in demonstrat- ing extraaxial haematomas, those that are not detected by CT are small and generally do not require surgery (4). The diagnostic sensitivity of
MR is clearly superior to that of CT in cases of small, non-haemorrhagic lesions (e.g., DAI, bland cortical contusions), but the recognition of this type of lesion in minor head trauma pa- tients does not alter the therapeutic manage- ment nor the clinical outcome (18, 30).
Patients with moderate (GCS = 8-12) and severe (GCS< 8) head trauma share a number of clinical and therapeutic characteristics, and for the sake of simplicity they will be consid- ered as a single group (4). It should be point- ed out that before commencing any diagnos- tic examination, the stabilization of the pa- tient’s respiratory and circulatory systems must be ascertained, ensuring the freedom of the airways (with intubation, if necessary), cer- vical spine stabilization (in case of underlying fracture/subluxation), respiratory function (face mask with high flow O
2; controlled ven- tilation if the patient is intubated) as well as their haemodynamic condition (e.g., identifi- cation and treatment of serious internal and external haemorrhaging; volemic restoration with isotonic solutions or plasma expanders).
Tab. 2.1 - Glasgow Coma Scale (GSGS) Best Eye Response
• Eyes open spontaneously
• Eye opening to verbal command
• Eye opening to pain
• No opening of eyes Best Motor Response
• Obeys commands
• Localising pain
• Withdrawal from pain
• Flexion to pain
• Extension to pain
• No motor response Best verbal Response
• Oriented
• Confused
• In appropriate words
• Incomprehensible sounds
• No verbal response
Mild cranial trauma GCS = 13 - 15
Moderate cranial trauma GCS = 9 - 12 Severe cranial Trauma GCS = 1 - 8
Once the patient’s clinical stability has been ascertained, the neurological examination may commence with the evaluation of the GCS, pupillary analysis and the evaluation of later- alizing signs, as well as with a general clinical examination for the identification of any oth- er non-cranial traumatic lesions. Patients with moderate and severe head injuries usually suf- fer from disorders of consciousness, often as- sociated with focal neurological deficits. In such cases, the fundamental question to be answered is whether the patient has an in- tracranial haematoma that requires surgery; at present CT is the only technique that is able to exclude this type of lesion rapidly and with sufficient reliability.
Once the need for emergency surgery has been eliminated, certain authors recommend performing an MR examination during the first two weeks of the traumatic event in pa- tients with moderate to severe head injuries.
MR has a far greater sensitivity than CT in diagnosing DAI, small cortical contusions (especially when non-haemorrhagic) and brainstem lesions, conditions that usually demonstrate minor or completely negative CT findings that may contrast considerably with the impaired clinical picture. In such cases, MR permits a more accurate evalua- tion than does CT with regard to the extent of the involvement of the encephalon and the brainstem, thus offering important informa- tion on possible clinical evolution and out- come (3, 5).
It should be remembered that although clinical indicators such as the GCS are useful instruments in establishing the patient’s clini- cal condition, they do not provide significant information on the actual lesion(s) underlying the signs and symptoms, the prognosis or the patient’s clinical evolution. Low GCS scores can be obtained from a number of different brain injuries that ultimately are responsible for vastly different clinical evolutions. Prior to the advent of MRI, diagnostic studies had lit- tle impact on prognosis; for example, many au- thors have highlighted the poor prognostic val- ue of CT findings (2, 3, 12). CT’s poor sensi- tivity in documenting non-haemorrhagic le-
sions of the brain is believed to be partly re- sponsible for the poor correlation between CT findings and clinical evolution, which appear to be much better correlated with MRI find- ings (3).
In particular, the number of DAI lesions would appear to be inversely correlated with the GCS score in the long term; whereas 80%
of patients without DAI recover well, only 27% of those with more than 10 lesions have a good prognosis (3). Conversely, the number of cortical contusions and the presence of iso- lated subdural or epidural haematomas do not appear to be statistically correlated with clini- cal evolution, unless associated with significant mass effect (e.g., transtentorial cerebral herni- ation and brainstem compression) (3). Signs of brainstem compression and intrinsic brainstem lesions typically suggest a very severe progno- sis, especially when observed in combination.
It should be pointed out that most au-
thors agree that it is not necessary to per-
form skull x-rays for the purpose of diag-
nosing fractures (15, 17, 20, 25, 26). The
presence or absence of fractures is often not
indicative of the gravity of the underlying in-
jury of the brain. Skull fractures can in fact
be isolated and are not necessarily associat-
ed with intracranial haematomas; converse-
ly, the absence of fractures does not exclude
the possibility of serious brain damage: in
25-30% of patients with moderate and se-
vere trauma and brain lesions, the skull is
not fractured (16). Fractures shown on x-
rays do not therefore necessarily indicate
brain damage, nor is the absence of such
fractures reassuring with regard to the pa-
tient’s normality (15, 17). In short, the diag-
nosis of fractures is not as important as is
the identification of depressed fractures, in-
tracranial dislocation of bone fragments,
fractures in critical positions such as the
temporal bone and base of the skull (which
can be associated with fluid fistulae and vas-
cular lacerations or fistulae) and associated
intracranial lesions (especially intra- and ex-
traaxial haematomas). In all such cases, CT
offers diagnostic potential that is far superi-
or to conventional x-ray examinations.
REFERENCES
1. Frankowski RF, Annegers JF, Whitman S. Epidemiological and descriptive studies. Part I: The descriptive epidemio- logy of head trauma in the United States. In: Becker DP, Polishock J, eds. Central Nervous System Trauma Status Report. Bethesda, MD National Institute of Health, 33-51, 1985.
2. French BN, Dublin AB: The value of computerized tomo- graphy in the management of 1000 consecutive head inju- ries. Surg Neurol 7:171-183, 1977.
3. Gentry LR, Godersky JC, Thompson BH: Prognosis after severe head injury: MRI correlation with Glasgow outco- me scale. (Submitted).
4. Gentry LR: Head trauma. In: Atlas SW:Magnetic resonan- ce of the brain and spine.(2nded.), Lippincott-Raven, Phi- ladelphia, pp. 611-647, 1996.
5. Gentry LR: Imaging of closed head injury. Radiology 191:1-17, 1994.
6. Grumme T, Kluge W, Kretzschmar K et al: Head Trauma.
In: Cerebral and spinal computed tomography. Blackwell Science, Berlin pp. 49-69, 1998.
7. Johnson MH, Lee SH: Computed tomography of acute ce- rebral trauma. Radiol Clin N Am 30:325-352, 1992.
8. Kanal E, Shellock FG: Patient monitoring during clinical MR imaging. Radiology; 185:623-629, 1992.
9. Keskil S, Baykaner K, Ceviker N et al: Clinical significan- ce of acute traumatic intracranial pneumocephalus. Neu- rosurg Rev. 21(1):10-3, 1998.
10. Klufas RA, Hsu L, Patel MR: Unusual manifestations of head trauma. AJR 166:675-681, 1996.
11. Kuntz R, Skalej M, Stefanou A: Image quality of spiral CT versus conventional CT in routine brain imaging. Eur J Ra- diol. 26(3):235-40, 1998.
12. Lanksch W, Grumme T, Kazner E: Computed tomography in head injuries Springer, Berlin, 1979.
13. Lee TT, Aldana PR, Kirton OC et al: Follow-up computeri- zed tomography (CT) scans in moderate and severe head injuries: correlation with Glasgow Coma Scores (GCS), and complication rate. Acta Neurochir Wien. 139(11):1042-7;
discussion 1047-8, 1997.
14. Leidner B, Adiels M, Aspelin P et al: Standardized CT exa- mination of the multitraumatized patient. Eur Radiol.
8(9):1630-8, 1998.
15. Lloyd DA, Carty H, Patterson M et al: Predictive value of skull radiography for intracranial injury in children with blunt head injury. Lancet. 22; 349(9055):821-4, 1997
16. Macpherson BCM, Macpherson P, Jennett B: CT inciden- ce of intracranial contusion and hematoma in relation to the presence, site and type of skull fracture. Clin Radiology 42:321-326, 1990.
17. Mogbo KI, Slovis TL, Canady AI et al: Appropriate ima- ging in children with skull fractures and suspicion of abu- se. Radiology. 208(2):521-4, 1998.
18. Mohanty SK, Thompson W, Rakower S: Are CT scan for head injury patients always necessary? J Trauma 31:801- 805, 1991.
19. Nagy KK, Joseph KT, Krosner SM et al: The utility of head computed tomography after minimal head injury. J Trau- ma. 46(2):268-70, 1999.
20. Osborn A: Craniocerebral trauma. In Osborn A: Diagno- stic neuroradiology. St Louis, pp 199-247, 1994.
21. Parizel PM, Ozsarlak P, Van-Goethem JW et al: Imaging findings in diffuse axonal injury after closed head trauma.
Eur Radiol. 8(6):960-5, 1998.
22. Pellicanò G, Bartolozzi A: La TC nei traumi cranioencefa- lici. Edizioni del Centauro, Udine,1996.
23. Petitti N, Williams DW 3rd: CT and MR imaging of nonacci- dental pediatric head trauma. Acad Radiol. 5(3):215-23, 1998.
24. Rhea JT, Rao PM, Novelline RA: Helical CT and three-di- mensional CT of facial and orbital injury. Radiol Clin North Am 37:489-513, 1999.
25. Shane SA, Fuchs SM: Skull fractures in infants and pre- dictors of associated intracranial injury. Pediatr Emerg Ca- re. 13(3):198-203, 1997.
26. Snoek J, Jennet B, Adams JH: Computerized tomography after recent severe head injury in patients without acute in- tracranial hematoma. J Neurol Neurosurg Psychiat 42:215- 225, 1979.
27. Stein SC, Ross SE: The value of computed tomographic scans in patients with low-risk head injuries. Neurosurgery 26:638-640, 1990.
28. Teasdale G, JennettB: Assessment of coma and impaired consciousness: a practical scale. Lancet 2:81-84, 1974.
29. Weisberg L., Nice C.: Cerebral computed tomography.
W.B. Saunders, Philadelphia, pp 321-343, 1989.
30. Williams DH, Levin HS, Eisenberg HM: Mild head injury classification. Neurosurgery, 27:422-428, 1990.
31. Wilson AJ: Gunshot injuries: what does a radiologist need to know? Radiographics 19:1358-1368, 1999.
32. Wysoki MG, Nassar CJ, Koenigsberg RA et al: Head trau- ma: CT scan interpretation by radiology residents versus staff radiologists. Radiology. 208(1): 125-8, 1998.
33. Zee CS, Go JL: CT of head trauma. Neuroimaging Clin N Am. 8(3): 525-39, 1998.
