Key-words:
Craniotomy - embolization - middle meningeal artery - organized chronic subdural hematoma
Introduction
An organized chronic subdural hematoma (OSDH) is a subtype of refractory chronic subdural
hematomas (CSDHs), and the most preferred treatment for an OSDH remains unknown. An
OSDH has been said to require a large craniotomy for radical treatment. However, a
craniotomy is associated with a risk of postoperative hemorrhagic complications or
recurrence.[[1]] Acute subdural hematomas and other common hemorrhagic complications have been reported
in 6%–12% of craniotomies for an OSDH.[[1]],[[2]],[[3]] In addition, a CSDH, including an OSDH, develops in the elderly with several comorbidities.
Some patients cannot undergo a craniotomy under general anesthesia because of underlying
diseases.
Recently, the effectiveness of a middle meningeal artery (MMA) embolization for fluid
CSDH has been reported. However, to the best of our knowledge, only few cases have
been reported regarding MMA embolization for an OSDH.[[3]],[[4]] In this report, we present two cases of OSDHs treated with MMA embolization followed
by a small craniotomy.
Case Reports
Case 1
A 71-year-old man with a history of diabetes mellitus underwent a burr hole irrigation
for CSDH. One month later, he visited our hospital complaining of easily falling.
Neurologically, he was alert but had dysarthria and slight left hemiparesis. A head
computed tomographic (CT) scan revealed a right CSDH with midline shift [[Figure 1]]a. A single burr hole irrigation was attempted on the day he was admitted, but the
hematoma was solid and could not be evacuated via a single burr hole [[Figure 1]]b.
Figure 1: Perioperative images of Patient 1. A 71-year-old man (Patient 1) with an organized
chronic subdural hematoma (a) underwent a burr hole irrigation, which failed (b).
The middle meningeal artery, having an abnormal vascular network, (c) was embolized
using Embosphere® and detachable coils (d). After embolization, a minicraniotomy was
performed for hematoma evacuation (e). Although a new asymptomatic left subdural hematoma
appeared on the %-year follow-up, no recurrence was seen on his operated right side
(f)
He was subsequently diagnosed as having an OSDH and underwent an MMA embolization
using trisacryl gelatin microspheres (Embosphere®; Nihonkayaku, Tokyo, Japan, 300–500
μ) and three Target Helical Ultra (Stryker, Kalamazoo, MI, USA) [[Figure 1]]c and [[Figure 1]]d. The following day, he underwent a small craniotomy for hematoma removal under
local anesthesia. The oozing from the hematoma outer membrane (HOM) and between the
HOM and dura mater was minimal during craniotomy, and the organized hematoma was easily
evacuated because the intraoperative bleeding could be easily controlled. Postoperatively,
his symptoms, dysarthria and slight hemiparesis, disappeared. Postoperative CT demonstrated
the disappearance of the hematoma and absence of hemorrhagic complications [[Figure 1]]e. During 1½-year follow-up period, no recurrence of the right hematoma was found
although asymptomatic left CSDH was newly revealed [[Figure 1]]f.
Case 2
A 77-year-old male man admitted to a local hospital and underwent a burr hole irrigation
for a left CSDH [[Figure 2]]a. The hematoma was organized, and his neurological symptoms of motor aphasia (the
difficulty of word recall) and right mild hemiparesis did not improve. He was referred
to our hospital for further treatment 2 weeks after the first burr hole surgery. On
arrival, a CT scan disclosed a thick hematoma in his left convexity [[Figure 2]]b.
Figure 2: Perioperative images of Patient 2. A 77-year-old man (Patient 2) underwent a burr
hole irrigation on the left chronic subdural hematoma (a). He was referred to our
hospital for further treatment of an organized chronic subdural hematoma 2 weeks after
the surgery (b). The abnormal vascular network of middle meningeal artery (c) was
embolized using Embosphere® and coils (d). He underwent a craniotomy under local anesthesia
(e), and his symptoms were relieved. Although the organized chronic subdural hematoma
did not disappear 6 months later at follow-up (f), he is currently asymptomatic
After MMA embolization using Embosphere® (300–500 μ) and three Target Helical Ultra
(Stryker) [[Figure 2]]c and [[Figure 2]]d, a craniotomy for evacuation of the OSDH was performed under local anesthesia.
During the surgery, there was almost no ooze from the HOM or from the hematoma itself
[[Figure 3]]. After the craniotomy, his neurological symptoms improved. A postoperative CT scan
showed no acute hemorrhagic complications although the OSDH remained [[Figure 2]]e. At 1-year follow-up, there was no evidence of any neurological deficits although
a CT scan revealed that the hematoma remained [[Figure 2]]f.
Figure 3: Intraoperative photographs of patient 2. During the surgery of Patient 2, a thick
outer membrane (a) and liquid-solid hematoma (b), typical of organized chronic subdural
hematoma, below the craniotomy site was evacuated (c). The ooze from the dura mater,
hematoma, and outer membrane was minimal and was easily stopped by simple manipulation
Discussion
These two cases highlighted some important issues. First, an MMA embolization for
an OSDH may be useful to prevent recurrences. An MMA embolization for a refractory
CSDH has been reported to prevent recurrence; the efficacy for an MMA embolization
is more than 90%.[[5]],[[6]] In addition, a recent systematic review reported that the recurrence rate after
an MMA embolization for a CSDH is 3%–6%, not restricted to refractory cases.[[7]] A CSDH is considered to develop due to repeated hemorrhage from the outer membrane
of a hematoma.[[8]] An MMA embolization is presumed to prevent the recurrence of a CSDH by blocking
the blood supply via the dura mater to the outer membrane of the hematoma.[[9]]
If the theory for preventing the recurrence of an MMA embolism is correct, it is reasonable
to assume that an MMA embolization will be effective for the treatment of an OSDH
because an OSDH supplies blood from the MMA via fragile sinusoidal vessels at the
junction of the inner and outer membranes.[[2]],[[10]] A previous study has reported three patients treated with MMA embolization, which
established its effectiveness in preventing postoperative recurrence of an OSDH.[[3]] Similarly, the two cases in the present study showed no recurrence.
Some precautions can be taken for effective and safe MMA embolization. First, the
embolization target should be the distal part of the MMA, where the pre-embolization
angiography shows an abnormal vascular network. Therefore, we considered that particle
embolic materials were suitable for this procedure and that a coil was not suitable
as an embolic material because it could not embolize the distal part of MMA. Liquid
embolic material can occlude the target, but it carries a risk of trapping the catheter.
Second, we must be attentive toward dangerous anastomosis collaterals to avoid complications,
where the embolic materials accidentally enter dangerous anastomosis collaterals,
in particular, the recurrent meningeal artery. We should confirm the absence of a
recurrent meningeal artery, guide the microcatheter to the horizontal segment of the
MMA, verify that the microcatheter does not wedge the vessel, and embolize the MMA
without pressure. Third, the MMA should be occluded at the microcatheter-guided site
with a coil to prevent recanalization.
The second important issue is that an MMA embolization may enable hematoma evacuation
using a small craniotomy by reducing the amount of intra- and post-operative bleeding.
As shown in [[Figure 3]], hemorrhage was lesser in the craniotomy after the embolization than without precraniotomy
embolization. As bleeding could be easily controlled, the operation time decreased
and the craniotomy was small and performed under local anesthesia. We resected only
a part of the HOM and hematoma beneath the craniotomy site. Although the HOM and hematoma
remained, postoperative acute phasic hemorrhage did not occur.
These findings may be contrary to the established consensus that an OSDH requires
a large craniotomy under general anesthesia as excision of the HOM is required. This
consensus is derived from a report which concluded that partial hematoma removal and
remnant HOM, containing fragile capillaries from the dura mater, cause postoperative
hemorrhage and hematoma growth.[[2]],[[11]],[[12]],[[13]] From our experience of these two cases, we hypothesize that partial resection of
a hematoma is sufficient to eliminate symptoms and would be sufficient for the treatment
of an OSDH under the condition that the blood supply via the dura mater is blocked.
Therefore, the procedure would be favorable for patients with a poor general condition.
Whether the residual hematoma could be a cause for relapse is unknown. In fact, one
reported case showed recurrence of an OSDH after an MMA embolization using polyvinyl
alcohol particles and fibered coils. The recurrence was speculated to be due to the
development of new collateral pathways in the HOM as a residual organized hematoma
delay healing.[[4]] However, we often observed no increase in the size of the hematomas in patients
with OSDH treated conservatively, despite the presence of an OSDH. This fact supports
our approach of avoiding the total removal of hematoma in a craniotomy procedure.
Although we cannot provide a detailed rationale as to why the MMA embolization was
effective, we speculate that the MMA embolization suppressed inflammatory changes
and local anticoagulation, contributing to the OSDH relapse.
Conclusions
Partial removal of an OSDH after an MMA embolization may be a therapeutic option.
Declaration of patient consent
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