Diffuse Axonal Injury after severe head trauma

Summary Diffuse Axonal Injury (DAI) is a well known entity that affects many patients with severe head trauma. Classically DAI has been considered the pathological substrate of those cases rendered unconscious at the moment of impact and in which the CT scan does not show mass lesions. Diffuse axonal damage is almost always related to mechanisms of injury in which the rotational acceleration produces shear and tensile strains of high magnitude. In this paper we present a group of 24 patients with a severe head injury in whom the postmortem examination demonstrated unequivocal signs of DAI.Widespread axonal retraction balls, located preferentially in the centrum semiovale and internal capsule were the most constant histological finding. We divided the entire series into two subgroups. One group (15 cases), included all the patients in whom the CT scan did not demonstrate mass lesions. In the second group (9 patients) we considered patients with a diffuse axonal injury in whom the CT scan additionally demonstrated a mass lesion (6 acute subdural haematomas, 2 intracerebral and 1 extradural haematoma). The mean age of the entire group was 26 years.Twenty two patients were injured in a road traffic accident, the remaining two fell from a considerable height. All were rendered immediately unconscious on impact. Diffuse brain damage is a common finding in patients with a severe head injury and immediate coma in whom the CT scan does not show mass lesions. Diffuse axonal injury can also appear in connection with a wide spectrum of focal lesions (acute subdural haematoma, basal ganglia haematoma etc.). Associated shear injuries of the brain in this latter group, could justify the poor outcome that certain groups of patients had in spite of the rapid surgical treatment and aggressive control of intracranial pressure.     

A clinical and pathological study of diffuse axonal injury

There is increasing evidence from human and experimental studies that the most important factor governing the outcome in head injury is the severity of diffuse axonal injuries. The authors have experienced 18 cases of severe diffuse axonal injury which showed post-traumatic coma for more than 24 hours and CT findings resembling those of shearing injuries of the cerebral white matter such as have been presented by Zimmerman et al. (1978). The consciousness levels on admission were 6 or less on the Glasgow Coma Scale and all cases were shown clinically to have primary brain stem injury. The main type of head trauma resulted from road traffic accidents (83%). Skull fractures were found in only 5 cases (28%). These findings suggested that acceleration/deceleration injury produce in the patients severe diffuse axonal injury. Initial ICP was below 20 mmHg in 11 cases out of 13 (85%). Parenchymal small hemorrhagic lesions of initial CT were basal ganglia (7 cases), corpus callosum (4 cases), pons (4 cases), midbrain (3 cases) and thalamus (2 cases). Extraparenchymal hemorrhagic lesions included intraventricular hemorrhage (6 cases) and subarachnoid hemorrhage (6 cases). Two autopsied cases of severe diffuse axonal injury (acute case and chronic case) showed remarkable congestion and edema in the deep part of the frontal white matter. Microscopic examination revealed marked axonal degeneration including axonal retraction ball in the corpus callosum, in the internal capsule and in the white matter of the brain stem. Glasgow Outcome Scale of the 18 patients at 3 months after the trauma made us concerned that no patients indicated good recovery or even only moderate disability.(ABSTRACT TRUNCATED AT 250 WORDS)     

MRI findings of closed head injury in children; with special reference to the effect of central shearing force]

It is considered that shearing effect as introduced by Holbourn may produce central concussion, diffuse brain swelling and diffuse axonal injury according to its grade of force. MRI was performed in 38 children who had been admitted to our hospital during the previous 1 year for the treatment of closed head injury of varying severity. In 8 out of 38 cases, abnormal high signal intensity was observed in the medial and para-medial brain parenchyma on MRI. All of these 8 cases suffered from head trauma caused by motor vehicle accidents. They included 2 cases of cerebral concussion, 1 of diffuse brain swelling, and 5 cases of diffuse axonal injury. In 2 cases of cerebral concussion, MRI (T2 weighted) revealed only localized high intensity in the corpus callosum, while CT showed normal and subarachnoid hemorrhage only at the interposium. These two children had been unconscious for periods of 20 to 30 minutes. In one case of diffuse brain swelling, MRI (T2W) showed a slightly obscure border between gray and white matter due to generally increased intensity. In 5 cases of diffuse axonal injury, most of these cases manifested lesions at the corpus callosum, deep white matter, periventricular gray matter, pons, midbrain and the cerebellum as demonstrated by high signal intensity on MRI (T2W) while CT in the acute stage showed small hemorrhage at the corpus callosum, corticomedullary junction and mid-brain and in the ventricles. Among these, two cases also demonstrated subdural hematoma and cortical contusional hemorrhage. At 3-4 weeks after injury, the area of high intensity previously demonstrated in the deep white matter and the corpus callosum on MRI (T2W) was reduced.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intention tremor after head injury. Clinical features and computed tomographic findings

Eight cases of intention tremor as a late complication of head injury were investigated. The patients ranged in age from 3 to 24 years. All received severe head injuries and lapsed into coma immediately afterward (Glasgow Coma Scale scores less than or equal to 8). Six patients exhibited decerebration or decortication. Hemiparesis was present in six cases and oculomotor nerve palsy in four. In the chronic stage, all patients displayed some degree of impairment of higher cortical function and five had dysarthria and/or ataxia. Initial computed tomography (CT) scans within 3 hours after the injury were obtained in five cases, of which four showed a hemorrhagic lesion in the midbrain or its surroundings. Other CT findings were diffuse cerebral swelling (four cases), intraventricular hemorrhage (three), and multiple hemorrhagic lesions (two). In the chronic stage, generalized cortical atrophy or ventricular enlargement was noted in five cases. These clinical features and CT findings indicate diffuse brain damage as well as midbrain damage and may reflect shearing injury.     

Diffuse traumatic cerebral injuries in children

A consecutive series of 41 patients aged less than 16 and admitted to the Department of Neurosurgery of the University of Milan in the period 1977-1978 following serious cranioencephalic trauma with Glasgow Coma Score (GCS) less than or equal to 7, duration of coma longer than 24 h and CT picture of diffuse lesion has been examined. These patients account for 5% of the paediatric cranial traumas observed in the same period and 66% of those in a state of coma. The CT picture made it possible to split patients into 3 groups: a) those without visible cerebral lesions and with subarachnoid and cisternal spaces present; b) those with small hyperdense lesions due to intraparenchymal or median/paramedian subcortical shearing lesions; c) those with marked constriction or absence of the 3rd ventricle and of the perimesencephalic cisterns. The first two pictures (a, b) were considered to be the expression of diffuse axonal damage, the last (c) of diffuse cerebral swelling. Intracranial pressure was monitored in about 50% of patients. The overall outcome of the series was favourable in more than 68% of cases with total mortality of 26.8%. Analysis of individual tomographic categories, however, showed that whereas the group of patients with diffuse axonal lesion presented nil mortality, those with diffuse cerebral swelling had 52% mortality owing to the onset of refractory intracranial hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)     

弥漫性脑肿胀临床分析(附46例报告)

目的　分析弥漫性脑肿胀 (DBS)的机理并探讨其诊断和治疗。方法　按Zimmerman的CT诊断标准对急诊 46例弥漫性脑肿胀 (DBS)患者临床资料进行研究 ,并对其诊断和鉴别诊断、治疗和预后进行分析。结果　DBS多发生于交通肇事 ,后即刻意识障碍 ,呈持续性昏迷 ,CT表现双侧大脑弥漫性肿胀 ,中线附近散在点状高密度灶。结论　DBS损伤机制与病理诊断的弥漫性轴索损伤 (DAI)是一致的 ,其致死、致残率高。     

Intraventricular hemorrhage in severe head injury

A series of 30 patients suffering posttraumatic intraventricular hemorrhage (IVH) after closed head injury is reviewed. Clotted blood and a mixture of blood and cerebrospinal fluid could be distinguished by computerized tomography (CT). Posttraumatic IVH was associated with diffuse brain lesions in most cases; intracerebral lesions with contusion, and subdural hematomas coexisted with posttraumatic IVH in eight and four instances, respectively. In two more cases, no CT abnormality other than IVH was noted. All patients in this series were in deep coma at the time of CT examination, and only seven survived. The early clinical findings, the site of ventricular hematoma, and the final outcome are analyzed.     

Post-traumatic intention tremor - clinical features and CT findings

Eight patients with post-traumatic intention tremor were reported. Intention tremor developed in the young as a late complication of severe head injury (Glasgow Coma Scale was below 8 in all cases) and impaired their functional outcome. This state was treatable with medication or by stereotactic thalamotomy. Neurologically, all the patients lapsed into coma immediately after the injury and many patients manifested clinical signs of a midbrain lesion in the chronic stage. The characteristic CT (computed tomography) findings in the acute stage were a high density area in the midbrain, accompanied by diffuse cerebral swelling or intraventricular hemorrhage, and in the chronic stage, brain atrophy or ventricular enlargement were the most prominent CT findings. These characteristics, indicating diffuse brain damage in addition to midbrain injury, may suggest the presence of shearing injury. The midbrain damage is consistent with the classical hypothesis that the damage to the Dentate-Rubro-thalamic system accounts for the occurrence of intention tremor. Furthermore, the presence of diffuse brain damage suggests that a more widespread brain injury may participate in its development.     

Immediate coma following inertial brain injury dependent on axonal damage in the brainstem

OBJECT: Immediate and prolonged coma following brain trauma has been shown to result from diffuse axonal injury (DAI). However, the relationship between the distribution of axonal damage and posttraumatic coma has not been examined. In the present study, the authors examine that relationship. METHODS: To explore potential anatomical origins of posttraumatic coma, the authors used a model of inertial brain injury in the pig. Anesthetized miniature swine were subjected to a nonimpact-induced head rotational acceleration along either the coronal or axial plane (six pigs in each group). Immediate prolonged coma was consistently produced by head axial plane rotation, but not by head coronal plane rotation. Immunohistochemical examination of the injured brains revealed that DAI was produced by head rotation along both planes in all animals. However, extensive axonal damage in the brainstem was found in the pigs injured via head axial plane rotation. In these animals, the severity of coma was found to correlate with both the extent of axonal damage in the brainstem (p < 0.01) and the applied kinetic loading conditions (p < 0.001). No relationship was found between coma and the extent of axonal damage in other brain regions. CONCLUSIONS: These results suggest that injury to axons in the brainstem plays a major role in induction of immediate posttraumatic coma and that DAI can occur without coma.     

Diffuse axonal injury and early intracranial sequelae in severe head injury.

The importance of diffuse axonal injury (DAI) and early intracranial sequelae was studied in 107 patients with diffuse and focal brain injuries. Comprehensive neuropathological study was also undertaken in 24 fatal patients. The mortality rate was clearly the highest in traumatic subarachnoid hemorrhage, followed by acute subdural hematoma, cerebral contusion with delayed hematoma formation, traumatic intracerebral hematoma, diffuse cerebral swelling, DAI with classical features, and finally nearly normal on computed tomographic scans. The mean flow velocities in the middle cerebral artery recorded by transcranial Doppler ultrasound were variable in diffuse brain injury, but commonly decreased on the hematoma side depending on increased intracranial pressure and decreased cerebral perfusion pressure in focal brain injury. Deep-seated hemorrhagic lesions did not expand in diffuse brain injury, but sizable hematoma developed within 24 hours in focal brain injury. The platelet count was significantly lower in patients with poor outcomes in focal brain injury. Histological evidence of classical DAI was found in eight (50%) of 16 cases with focal brain injury. DAI of varying severity is the common subjacent lesion in patients with severe head injury, but the final outcome varies greatly with different lesion types.     

螺旋CT对弥漫性轴索损伤的诊断价值

目的分析脑弥漫性轴索损伤(diffuse axonal injury,DAI)的CT表现,评价螺旋CT对DAI的诊断价值。方法回顾性分析43例DAI患者的CT表现。结果 DAI在CT影像上可见弥漫性脑肿胀,皮层下及脑深部小出血灶,中线结构无明显移位。43例患者检出58个病灶,非出血性病灶37个,呈斑片状大小不一低或稍底密度影,边界不清晰;出血性病灶21个,呈斑片状大小不一高密度影。结论螺旋CT检查是DAI的影像学诊断依据之一,结合临床能协助判断伤情,并为动态观察预后提供帮助。     

Normal computerized tomography scans in severe head injury. Prognostic and clinical management implications

The authors analyze the clinical course of 46 severely head-injured patients who had completely normal computerized tomography (CT) scans through the immediate posttraumatic period (1 to 7 days after trauma). These patients represent 10.2% of a consecutive series of 448 cases of severe head injuries and two-thirds of the cases showing a normal CT scan on admission (the other one-third of the cases developed new pathology). The usual course in these 46 patients after the initial coma was toward progressive neurological improvement, and 35 patients (76%) achieved a functional level of survival. Nine patients (19.5%) remained comatose for several weeks and developed severe disability. There were two fatalities due to medical complications. The final outcome was more closely related to the duration of coma (the longer the duration the worse the result) than to the initial Glasgow Coma Scale (GCS) score. In fact, 26% of the patients in the lower GCS score ranges (3 to 4 points) made a good recovery and 46% developed moderate disability only. These findings indicate that the grim prognostic significance of deep posttraumatic coma is tempered in the presence of a normal scan. However, the absence of CT abnormalities in severely head-injured patients cannot be equated with a good prognosis because in one-fifth of the cases serious permanent disability develops. Sustained elevation of the intracranial pressure (ICP) was not seen in these patients, indicating that ICP monitoring may be omitted in cases with a normal scan. However, since one-third of the patients with a normal admission scan developed new pathology within the first few days of injury, a strategy for control scanning is recommended. Control CT scans performed more than 6 months after injury showed a significantly higher incidence of brain atrophy in patients developing permanent disability than in those who made a good recovery.     

Diffuse brain swelling in severely head-injured children. A report from the NIH Traumatic Coma Data Bank.

In this study, data were prospectively collected from 753 patients (111 children and 642 adults) with severe head injury and examined for evidence of diffuse brain swelling and its association with outcome. Diffuse brain swelling occurred approximately twice as often in children (aged 16 years or younger) as in adults. A high mortality rate (53%) was found in these children, which was three times that of the children without diffuse brain swelling (16%). Adults with diffuse brain swelling had a mortality rate (46%) similar to that of children, but only slightly higher than that for adults without diffuse brain swelling (39%). When the diagnosis of diffuse brain swelling was expanded to include patients with diffuse brain swelling plus small parenchymal hemorrhages (less than 15 cu cm), these mortality rates were virtually unchanged.     

Sequential computerized tomography changes and related final outcome in severe head injury patients

Summary The authors analysed the serial computerized tomography (CT) findings in a large series of severely head injured patients in order to assess the variability in gross intracranial pathology through the acute posttraumatic period and determine the most common patterns of CT change. A second aim was to compare the prognostic significance of the different CT diagnostic categories used in the study (Traumatic Coma Data Bank CT pathological classification) when gleaned either from the initial (postadmission) or the control CT scans, and determine the extent to which having a second CT scan provides more prognostic information than only one scan.92 patients (13.3% of the total population) died soon after injury. Of the 587 who survived long enough to have at least one control CT scan 23.6% developed new diffuse brain swelling, and 20.9% new focal mass lesions most of which had to be evacuated. The relative risk for requiring a delayed operation as related to the diagnostic category established by using the initial CT scans was by decreasing order: diffuse injury IV (30.7%), diffuse injury III (30.5%), non evacuated mass (20%), evacuated mass (20.2%), diffuse injury II (12.1%), and diffuse injury I (8.6%).Overall, 51.2% of the patients developed significant CT changes (for worse or better) occurring either spontaneously or following surgery, and their final outcomes were more closely related to the control than to the initial CT diagnoses. In fact, the final outcome was more accurately predicted by using the control CT scans (81.2% of the cases) than by using the initial CT scans (71.5% of the cases only). Since the majority of relevant CT changes developed within 48 hours after injury a pathological categorization made by using an early control CT scan seems to be most useful for prognostic purposes.Prognosis associated with the CT pathological categories used in the study was similar independently of the moment of the acute posttraumatic period at which diagnoses were made.     

Rapid spontaneous disappearance of an acute extradural hematoma: case report

The authors report the case of a patient presenting with an acute extradural hematoma and diffuse axonal injury. Control CT scan performed 4 hours later showed the complete resolution of the extradural collection together with increased evidence of shearing injuries. The mechanism of the hematoma resolution may probably be related to the concomitant acute brain swelling.     

Magnetic resonance imaging in cases of severe head injury

Magnetic resonance imaging (MRI) is an invaluable tool in the evaluation of intracranial and spinal disorders. However, because of various technical limitations, the use of MRI in head-injured patients has yet to be fully explored. With its precise anatomical sensitivity, MRI may be useful in severely head-injured patients in whom computed tomographic (CT) scans fail to demonstrate an anatomical substrate for the degree of coma. In this regard, a prospective study in severely head-injured patients was undertaken. Twenty-four patients with Glasgow coma scores of 7 or less who had minimal or no CT abnormalities and normal intracranial pressures underwent MRI as soon as their medical conditions allowed. In all 24, MRI demonstrated lesions that were not evident on repeated CT scans--suspected white matter shear injuries or contusions in 10, brain stem injuries in 5, diffuse white matter injury in 5, and subdural hematoma in 4. None of the 19 patients with the most widespread MRI abnormalities or the presence of brain stem injuries made any significant neurological recovery. Various prognostic indicators of the outcome of acute posttraumatic coma are continuously being developed. In this group of patients, the MRI scan is the most sensitive measure. Significant MRI abnormalities with normal CT scans and intracranial pressures were universally associated with vegetative outcome in this series. As we gain experience imaging neurotrauma, MRI may form the basis for a better in vivo understanding of the substrate for and natural history of traumatically induced coma.     

Magnetic resonance imaging in diffuse brain injury]

Forty cases diagnosed as diffuse brain injury (DBI) were studied by magnetic resonance imaging (MRI) performed within 3 days after injury. These cases were divided into two groups, which were the concussion group and diffuse axonal injury (DAI) group established by Gennarelli. There were no findings on computerized tomography (CT) in the concussion group except for two cases which had a brain edema or subarachnoid hemorrhage. But on MRI, high intensity areas on T2 weighted imaging were demonstrated in the cerebral white matter in this group. Many lesions in this group were thought to be edemas of the cerebral white matter, because of the fact that, on serial MRI, they were isointense. In mild types of DAI, the lesions on MRI were located only in the cerebral white matter, whereas, in the severe types of DAI, lesions were located in the basal ganglia, the corpus callosum, the dorsal part of the brain stem as well as in the cerebral white matter. As for CT findings, parenchymal lesions were not visualized especially in mild DAI. Our results suggested that the lesions in cerebral concussion were edemas in cerebral white matter. In mild DAI they were non-hemorrhagic contusion; and in severe DAI they were hemorrhagic contusions in the cerebral white matter, the basal ganglia, the corpus callosum or the dorsal part of the brain stem.     

Primary brain stem lesions caused by closed head injuries

Traumatic lesions of the brain stem are of two types: primary, which are considered to be caused at the moment of impact, and secondary, associated with supratentorial mass lesion. Of the 239 patients with a serious head injury who showed a severe disturbance of consciousness upon admisision and who had CT scan carried out immediately, 21 cases were considered to have a primary brain stem lesion with initial CT scan. A primary brain stem lesion was found in 21 of 239 (8.8%) of patients with serious head injury. Their injuries were caused primarily by traffic accidents. Sixteen of the 21 cases showed not only brain stem lesions but also other brain injuries such as cerebral contusion of the white and gray matter, callosal injury, intraventricular hemorrhage, and subarachnoid hemorrhage, which are considered to be caused by a diffuse shearing injury. Five cases who showed a single injury to the brain stem with no other brain lesions were considered to have a pure brain stem lesion. Primary brain stem lesions were observed on the dorsal side of the midbrain, where they can be differentiated from secondary brain stem lesions. These lesions are considered to result from the shearing mechanism in and around the brain stem very close to the tentorial edge, or to an injury of the lower brain stem by hyperextension of the cervical vertebrae. The prognosis of patients with a primary brain stem lesion was usually unfavorable, except in those with a single brain stem lesion.     

Progressive brain injury

The aim of this study was to evaluate the clinical manifestations and prognostic factors of progressive brain injury following trauma. We reviewed the records of 779 patients with head injury who had an admission Glasgow Coma Scale of 9 or more; 70 (7.0%) developed progressive brain injury as evidenced on serial CT scans. Of these 70 patients, 19 (27.1%) had a subdural hematoma, 19 (27.1%) an epidural hematoma, 16 (22.9%) a cerebral contusion, 13 (18.6%) an intracerebral hematoma, and 3 (4.3%) a diffuse brain swelling. Three months after injury, 36 (51.4%) patients died, 2 (2.9%) were left in a vegetative state and 23 (32.9%) had a favorable outcome. The appearance of progressive brain injury was associated with patient age, admission Glasgow Coma Scale, injury mechanisms, skull fracture and hemorrhagic lesions on the initial CT scan. Patients with the extracerebral lesions deteriorated 4 hours after injury, whereas those with intracerebral lesions deteriorated 8 hours after injury. The outcome based on Glasgow Outcome Scale was significantly associated with age, type of intracranial lesion, Glasgow Coma Scale following deterioration, the mechanism of injury and surgical treatment. It is concluded that early repeated CT scan is indicated in patients with risk factors of developing progressive brain injury.     

Brain swelling and brain oedema in acute head injury

Summary Chronological changes in diffuse brain swelling and brain oedema were studied in repeated CT studies following a closed head injury. These findings were compared with changes in intracranial pressure (ICP). The grades of diffuse brain swelling were classified into mild, moderate and marked according to the CT findings. Planimetry of low density areas of brain oedema was carried out on repeated CT images. Diffuse brain swelling was recognized in 71 of patients shortly after the head injury and subsided within days 3–5. Brain oedema first appeared 24 hours post injury and did not reach its maximum size and distribution before days 5–8. Thus, these two events can be clearly separated. The intracranial pressure reflected the course of the brain swelling and was not very high during the presence of maximum oedema.