Key-words:
Chronic subdural hematoma - computed tomography scan control - Evans' index - ventricular
seize
Introduction
Chronic subdural hematoma (CSDH), which generally occurs in older patients, is one
of the most frequent clinical entities encountered in neurosurgery departments.[[1]],[[2]],[[3]] Treatment of subdural chronic hematoma ranges from simple drainage throughout once
or twice burr hole, with or without irrigation, to craniotomy.[[1]],[[2]] The burr-hole drainage could be the best modality as the initial treatment for
CSDH. Recently, lower recurrence rates using a burr-hole and closed drainage system
without irrigation have been reported. The intention of irrigation is to remove the
hematoma completely or at least to dilute its content.[[1]],[[3]] However, despite clinical improvement after surgery, the early computed tomography
(CT) scan control often showed persistence of liquid collection in the subdural space
which may discuss the possibility of recurrence or failed surgery. In the aim to study
the variation of intracranial liquid compartment following surgery, we have compared
the thickness of residual hematoma and the ventricular size between patients who have
an early CT scan control within the 3rd day of surgery and patients who had CT scan
control after that.[[4]],[[5]]
Methods
In this prospective study (2013–2016), data of sixty-three patients who were operated
for CSDH were analyzed. The diagnoses of CSDH were confirmed by CT scans. Surgery
involved the drilling of two burr holes on the side of the subdural hematoma and irrigation
of the subdural space with normal saline. Subdural drains were all closed systems
with no suction for 72 h. Among all patients, the postoperative CT scan controls were
performed during the week following evacuation of hematoma. The controlled patients
were sequentially allocated to either two groups; Group 1 with CT scan control under
the 3rd day of surgery and Group 2 with delayed CT scan control (from 4th to 7th day).
Radiological evaluation for cranial CT scan and a high-speed scanner was used. The
CT slices were parallel to the orbitomeatal plane, with axial slices from the foramen
magnum to the vertex. Linear measure of ventricular size was assessed, by Evans' index
as the linear ratio of the total width of the frontal horns of the cerebral lateral
ventricles (A) to the maximum inner diameter of the skull at the level of the measurement
(E). [[Figure 1]].[[4]] We reviewed and analyzed the data, including clinical presentations, precipitating
factors, CT scan findings, and outcomes. The preoperative and postoperative Evans'
indexes were compared between the two groups using Mann–Whitney test. All statistical
results were established significant if P < 0.05. The analysis was performed with
the IBM SPSS Statistics for Windows, Version 19.0. (IBM Corp: Armonk, NY).
Figure 1: Axial computed tomography scan, demonstrating measurement technique for Evans' index
as the linear ratio of the total width of the frontal horns of the cerebral lateral
ventricles (A) to the maximum inner diameter of the skull at the level of the measurement
(E).
Results
There were 33 patients in the Group 1 and 30 patients in the Group 2. The mean age
in all patients was 62 years [[Table 1]], 61.7 in Group 1 and 62.4 in Group 2 (P = 0.54). There were 53 males and 10 females,
and the sex ratio was 30/3 in Group 1 and 23/7 in Group 2 (P = 0.12). History of head
injury was noted in 23/63, 12/33 in Group 1 and 11/30 in Group 2 (P = 0.98). Five
patients (2 in Group 1 and 3 in Group 2) have hypertension. Diabetes was observed
in 4 patients in Group 2 and no patients in Group 1. Seven patients undertake anticoagulant
or antiplatelet treatment (3 patients in Group 1 and 4 patients in Group 2). Nine
patients (17%) were admitted with less of the level of consciousness, 6 patients in
Group 1 and 3 patients in Group 2 (P = 0.09). Neurological deficit was observed in
49 patients (77%); 26 in Group 1 and 23 in Group 2 (P = 0.84). Headache was reported
in 45 cases (70%), 24 patients in Group 1 and 21 patients in Group 2 (P = 81). Vomiting
was noted in 18 cases (28%), 11 patients in Group 1 and 7 in Group 2 (P = 0.33). The
subdural chronic hematoma was unilateral in 39 cases (62%), 20 cases in Group 1 and
19 in Group 2 (P = 0.82).
Table 1: Summary of epidemiological and clinical data in our study and comparison of these
features between two groups
The average of preoperative hematoma thickness was 20.4 mm [[Table 2]], 20.5 mm in Group 1 versus 19.9 mm in Group 2, and there was no statistical difference
(P = 0.67). The mean midline shift was 8.5 mm in each group. The preoperative Evans'
index was 26.7 in Group 1 and 27 in Group 2 (P = 0.7). Postoperatively, the mean thickness
of the residual hematoma was 7.7 mm in Group 1 and 8.4 mm in Group 2 (P = 0.57). The
mean midline shift was 3.3 mm in Group 1 and 1.9 mm in Group 2 (P = 0.08). The postoperative
Evans' index was 28.5 in Group 1 and 32.1 in Group 2 (P = 0.002). The comparison of
preoperative characters between two groups demonstrated no significant difference.
Table 2: Summary of pre- and postoperative computed tomography scan finding with statistical
comparison between two groups
Discussion
The insidious installation of symptoms in patients with CSDH is related to the intracranial
components of accommodation induced by progressive accumulation of this hematoma in
the subarachnoid space.[[6]],[[7]],[[8]] However, the presence of new mass in the inextended cranium led to the reduction
of one or more intracranial components (brain parenchyma, cerebrospinal fluid [CSF],
or vascular compartments). The reduction of intracranial CSF depends on diminution
of ventricular size and/or subarachnoid spaces.[[1]],[[2]],[[6]],[[9]] We have compared the epidemiological, clinical, and preoperative radiological data
between two groups and we observed no statistically significant difference. Postoperatively,
the thickness of hematoma in all patients was reduced from 20.4 to 8.1 mm, but there
was no significant difference between Group 1 and Group 2. This finding demonstrates
that some residual collection might take more time to be completely resolved. The
midline shift was significantly reduced in both groups compared to preoperative status,
but when it was compared between Group 1 and Group 2, the difference was not significant
with a P value at 0.08. In this study, the Evans' index was used to evaluate the reduction
of ventricular size preoperatively, in the immediate postoperative days and within
the 1 week of surgery. The Evans' ratio was one of the first attempts to use an index
of comparison of ventricular size in patients with large ventricles. It is measured
as the ratio of the span of the frontal horn on a pneumogram or a ventriculogram to
the maximum width of the skull on an AP film.[[5]] With the development of CT scan, the ratio of the frontal horn span to the maximum
width of the skull at the level of the frontal horn was developed as the frontal horn
index.[[4]] In our study, the postoperative Evans' index was 28.5 in Group 1 and 32.1 in Group
2, with a significant difference as P = 0.002. We conclude that despite the presence
of residual hematoma in early and delayed CT scan control, the expansion of ventricle
is progressive and differs between both groups. The evaluation of variation of ventricle
size compared to preoperative data might be a good indicator of success of surgery.
In this study, we agree that some potential methodological limitations should be noted,
such as the strategy of assessing ventricular size. Some authors have argued that
Evans' index represent no good measure of ventricular size as the correlation with
ventricular volume was low.[[4]] There are various strategies of linear measurements of ventricular size. It was
advocated that computation of the frontal and occipital horn ratio correlated well
with ventricular volume.[[4]],[[10]],[[11]],[[12]],[[13]] Others have argued that CT-based volumetric measurements in a more sensitive way
describe changes in ventricular volume.[[4]],[[10]]
Conclusion
According to our finding, postoperative residual hematoma might take more time to
be resorpted while the ventricle size shows a remarkable expansion.[[12]] Furthermore, the adoption of Evans' index, for assessing the variation of ventricular
seize after surgery, by neurosurgeons appears to be a good and simple method for evaluation
and following the success of surgical removal of subdural hematoma, despite the observation
of some residual collection in early CT scan control.
