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Traumatic Posterior Fossa Hematoma, A Rare Entity: Study of 21 Cases

Background Traumatic posterior fossa hematoma is a rare entity. Traumatic posterior fossa hematomas are associated with considerable morbidity and mortality and their surgical management remained controversial. Methods From August 2011 to August 2017, approximately 5,100 patients with head injury were managed. Authors reviewed clinical and radiological findings, management criteria, and outcome of posterior fossa hematoma in 21 patients. Results Out of 21 cases, 13 survived with our management. The Glasgow Coma Scale (GCS) on admission was higher in favorable group than in poor outcome group. Factors associated with Glasgow Outcome Scale in two groups were status of fourth ventricle, basal cisterns, subarachnoid hemorrhage (SAH), hematoma volume, and their location (hemispheric or midline). Similarly, associated supratentorial lesions, age, gender, lesions in other parts of body, and timing from injury to reporting to hospital were taken into consideration. Conclusion The factors correlated with patient outcome were age, sex, mode of injury, GCS at admission, associated intracranial hematomas, associated SAH, hematoma volume, hematoma location, basal cisterns, status of fourth ventricle, and associated multiple injuries on other body parts. It is hereby concluded that timely surgical intervention should be employed whenever indicated without delay. Posterior fossa hematomas were rarely observed in the pediatric age group. Abstract


Introduction
Traumatic posterior fossa hematoma is very less as compared with spontaneous hematomas associated with hypertension. They are associated with significant mortality and morbidity. They constitute a small subset of total head injury patients. 1 As we know, posterior fossa have small volume, and any increase in volume due to any cause may cause increase intracranial pressure, herniation, and deterioration. Traumatic posterior fossa hematomas account for < 1% in all head injury patients. 2, 3 Liu 4 reported the incidence of traumatic posterior fossa hematoma to be 3.7% of total intracranial hematomas. These hematomas may be totally asymptomatic, with a sudden increase in size can lead to rapid deterioration of neurological status. 5 Traumatic cerebellar hematoma may be isolated or may be associated with subdural hemorrhage (SDH), extradural hemorrhage (EDH), and subarachnoid hemorrhage (SAH) in posterior fossa. They may present acutely or in delayed manner. The hematoma location, volume, initial Glasgow Coma Scale (GCS) score, status of fourth ventricle, and basal cisterns are important in final outcome. Management of these hematomas nowadays have changed from all surgery to conservative management. 1 Authors evaluated outcome of patients on GCS score at admission, location, volume, status of cisterns, fourth ventricle, SAH, and supratentorial lesions. The surgical indications were posterior fossa hematoma with mass effect, midline shift, size greater than 3 cm, effaced basal cisterns, fourth ventricle compression, and associated supratentorial lesions with significant mass effect with midline shift.

Traumatic Posterior Fossa Hematoma Bhardwaj et al.
Similarly, patients were managed conservatively with respect to hematoma location, size less than 3 cm, normal basal cisterns, and fourth ventricle. In some of these hematomas, early surgical intervention is deemed necessary. [5][6][7][8][9] The early results of surgery are good, so surgical intervention if required should not be delayed. The course and prognosis of midline hematoma is worse, so evacuation should be done early.

Methods
From August 2011 to August 2017, approximately 5,100 patients with head injury were admitted in our institute. This study was focused on 21 patients (0.41%) with traumatic posterior fossa hematomas. The clinical findings, mode of injury, initial GCS, various radiological parameters, and final outcome were evaluated in 21 patients using Glasgow Outcome Scale (GOS). GOS was graded into good recovery (GR), moderate disability, severe disability (SD), vegetative state (VS), and death (D).
Initial computed tomography (CT) head was obtained at admission of patient and repeat CT head was done at 6 hours if the patient deteriorated more than 2 points of initial GCS score at admission. On CT scan, hematoma location, size, status of basal cisterns (normal or compressed), status of fourth ventricle (normal or compressed), associated SAH, and supratentorial lesions were evaluated. Hematoma volume was assessed by using formula A*B*C/2, where A is maximum transverse diameter of hemorrhage on CT, B is anterioposterior diameter, and C is number of CT slices showing hematoma. 10 Hematomas were classified as type 1 vermian hematoma (►Fig. 1) and type 2 hemispheric hematoma involving superficial two-thirds of the hemisphere (►Figs. 2 and 3). Injury is classified as coup, countercoup, and acceleration-deceleration type. Time to reach hospital is important as it affects overall morbidity and mortality of patient.

Clinical and Radiological Findings
Out of 21 patients, 18 were male and the rest females. Most of the patients were in the age range of 30 to 60 years. The mode of injury was road traffic accident (15 patients) and fall (6 patients). Duration between sustaining injury and reporting to hospital was 4 hours in 11 patients and 5 to 8 hours in 10 patients. GCS score on admission ranged from 3 to 15 as shown in ►Table 1. The location of hematoma was type 1 (8 patients) and type 2 (13 patients). Nine patients had isolated posterior fossa hematoma and 12 patients presented with associated intracranial lesions.

Type 1 and Type 2 Hematoma Outcome
Comparison between type 1 and 2 hematomas is shown in ►Table 2. Age range in type 1 was 22 to 56 years, while in type 2 hematomas it was 12 to 79 years. In type 2 hematomas, age varied over a wider range as compared with type 1. Volume of hematoma was higher in type 2 hematomas as

Treatment and Outcome
In our study, 10 patients were treated conservatively and 11 patients underwent surgery. All patients with surgical indications were operated immediately without any delay. Out of 11 patients, 10 patients underwent suboccipital craniectomy and hematoma evacuation, and 1 patient underwent both supratentorial and suboccipital craniectomy. CT head (►Fig. 3) suggestive of type 2 hematomas were managed conservatively and those suggestive of type 2 hematoma (►Fig. 1) managed by suboccipital craniectomy with hematoma evacuation. Outcome of 21 patients was GR in 6, MR (moderate recovery) in 3, SD in 3, VS in 1, and D in 8 patients. The incidence of poor outcome was 61.9% (13/21).

Prognostic Factors
Frequency, age (range), sex, mode of injury, GCS, hematoma location, basal cisterns, fourth ventricle, SAH, supratentorial contusions, SDH, EDH, IVH, DAI, lesion in posterior fossa, and their relationship with outcome are shown in ►Table 3. Agewise distribution shows that there were no females in the favorable group and all females were in the poor outcome group suggesting that females had higher mortality in posterior fossa hematoma. In our study, GCS at admission was higher in the favorable group as compared with the other group. Brainstem cisterns were compressed in 2 patients in the favorable group as compared with 7 in the poor outcome group. Fourth ventricle was compressed in 1 patient in the favorable group. There was significant presence of SAH in the poor outcome group as compared with the favorable group.

Discussion
These hematomas approximately constitute one-fourth of all posterior fossa traumatic lesions, 3,11 but their frequency is almost between SDH and EDH. 9,12 Sato et al 13 established 0.7% incidence of cerebellar contusions. Nagata et al reported their frequency to be between 0.6 and 0.82%. The incidence observed in our series was 0.41%, which correlates well with other figures. Various mechanisms are responsible for these Traumatic Posterior Fossa Hematoma Bhardwaj et al.  hematomas but remain unclear. These could be coup and countercoup injuries. Coup injuries are thought to be the most frequent mechanism. 1,7,14 Countercoup injuries are considered to be rare. 15 Another mechanism for traumatic intracerebellar hematoma involves acceleration and deacceleration injuries. 16 In our series, 7/21 patients had coup (33.3), 4/21 (19.0) had countercoup injuries, and the rest (47.6) had accelerationdeacceleration injuries. So, this leads us to the conclusion that acceleration and deacceleration is a common cause as reported previously by Takeuchi et al. 17 Delayed or evolving hematoma has been reported previously. 18,19 In our series, no cases of delayed or evolving hematoma was reported as repeat scan was done within 6 hours of admission as mentioned previously. However, repeat CT examination is necessary, as delayed hematomas can develop.
The incidence of poor outcome in previously published series were around 20 to 100% (average 60%), 2 and in our series, it was 61.9%. The prognosis was better in good GCS patient and in patients who were promptly operated with surgical indication. 20 Summary of published series of posterior fossa hematomas are depicted in ►Table 4.
D'Avella et al have described protocol for traumatic intracerebellar hematomas as follows: 1. Conservative approach is a treatment option for noncomatose patients with intracerebellar clots 3 cm, except when associated with other EDH or SDH of posterior fossa. 2. Surgery should be done for any patient with any clot > 3 cm.
In our study, surgery was done in 11 patients, out of which 7 patients survived and 4 expired. In our series, type 1 hematomas were more frequent in the poor outcome group due to easy compression of brainstem or involvement of deep cerebellar nuclei which lead to bad prognosis. 17 Various factors influencing surgical decision were patients with poor GCS, advanced age, poor general condition, clinical signs of early brainstem damage, bilateral cerebral clots, and associated multiple supratentorial intracranial hemorrhages with evidence of coagulopathy. These factors reflect the peculiar heterogenecity of clinical radiological picture of this subset of posterior fossa hematomas. 21 HCP is usually not associated with traumatic intracerebellar clots. 11,18 Karasawa et al 3 mentioned of acute HCP in 20% of intracerebellar hematomas, while in our series it was 9.52%. The timing of reaching hospital is important and affects overall morbidity and mortality of patients. Most of the patients in the favorable outcome group reported to hospital within 4 to 5 hours, whereas those in the poor outcome group had reported more than 4 to 8 hours. There was single case of posterior fossa hematoma with associated SDH in our series (►Fig. 1C). This suggests that associated lesions in posterior fossa hematoma such as SDH and EDH are less.
Posterior fossa hematoma is rare in children and incidence of cerebellar hematoma is much rarer. 22 Most frequent mode of injury is fall followed by road traffic accident. 23 Trauma is a leading cause of childhood head injury, with Center for Disease Control, stating about half a million emergency department visits in the United States is for traumatic brain injury for children aged 0 to 14 years, with 0 to 4 years being the most vulnerable group. 24 Although most cases are seen in young adults, Zuccarello et al 25  Suboccipital craniectomy with hematoma evacuation is the most preferred surgical approach in posterior fossa. 26,27 Clinical with radiological features, types of hematomas, prognostic factors, and final outcome are discussed and mentioned in ►Tables 1-3. In summary, patients who reported within 4 hours of trauma, with initial GCS score of between 9 and 15, absent SAH, normal basal cisterns, and normal fourth ventricle had better survival rate. However, older age group and females fared worse in our study as shown in ►Tables 1-3. In severely ill subjects, surgery should be individualized for each patient with reasonable salvageability.

Conclusion
Traumatic cerebellar hematoma is a life-threatening condition that requires timely management. Nowadays, with wider availability of CT and intensive neuromonitoring, smaller hematomas can be managed conservatively and larger ones with surgical evacuation in clinically deteriorating patients.
The factors correlated with patient outcome were age, sex, mode of injury, GCS at admission, associated intracranial hematomas, associated SAH, hematoma volume, hematoma location, basal cisterns, status of fourth ventricle, and associated multiple injuries on other body parts. It is hereby concluded that timely surgical intervention should be employed whenever indicated without delay. This study had some limitations, like sample size was relatively small to determine the actual prognostic factors. As these lesions are associated with higher morbidity and mortality, it should be evaluated further to explore pathophysiology for better clinical outcome of patients.

Funding
None.