Keywords cerebrospinal fluid leak - epidural blood patch - intracranial pressure monitoring
- spontaneous intracranial hypotension - subdural hematoma
Introduction
Spontaneous intracranial hypotension (SIH) is a clinical syndrome characterized by
orthostatic headache and cranial nerve deficits due to brain sagging caused by a reduction
in cerebrospinal fluid (CSF) volume and pressure.[1 ]
[2 ]
[3 ] In addition to headaches, SIH also causes symptoms such as stiff necks, nausea,
vomiting, tinnitus, and dizziness. Furthermore, serious complications of SIH include
brain sagging, cerebral venous sinus thrombosis, and coma due to SDH.[4 ] Brain sagging generates negative pressure around the convexity, placing tension
particularly on the bridging veins attached to the skull. The precise mechanism remains
unclear, but concomitant subdural hematoma (SDH) is thought to result from brain sagging.[5 ]
[6 ] The management of SIH with SDH presents a unique therapeutic challenge, as the underlying
pathophysiological mechanisms require a balanced approach addressing both the CSF
leak and the hematoma.
When SIH is complicated by SDH, management becomes challenging because the two conditions
have opposite pathophysiology. SIH causes symptoms from low intracranial pressure
(ICP) and is treated by raising CSF volume (epidural blood patch [EBP]), whereas symptoms
of SDH are caused by high ICP and are treated by reducing intracranial volume (hematoma
drainage).[7 ] Several case reports have documented severe neurological deterioration or even fatal
outcomes following isolated hematoma drainage in patients with unrecognized SIH.[8 ]
[9 ] Conversely, EBP without addressing a significant hematoma may lead to rebound intracranial
hypertension, characterized by severe headache, nausea, and visual disturbances.[10 ]
[11 ] Kranz et al described nine patients who developed confirmed rebound intracranial
hypertension following EBP, with opening pressures averaging 30 cm H2 O (range 22–55 cm H2 O).[10 ] This phenomenon emphasizes the delicate balance of ICP in these patients and the
potential risks of a single therapeutic approach. Furthermore, the difficulty of distinguishing
between neurological deterioration due to intracranial hypertension or persistent
hypotension based merely on clinical findings is a significant diagnostic dilemma
that can lead to inappropriate management decisions.
To address these difficulties, we designed a technique that involved performing both
burr hole hematoma evacuation and epidural blood patching in the same session. In
addition, we continuously monitored ICP during the procedure. This technique enables
immediate epidural blood patching if ICP is low during burr hole hematoma evacuation.
Conversely, by continuously monitoring ICP in real time during epidural blood patching,
immediate intervention (hematoma drainage) can be performed when dangerous signs of
ICP elevation appear. Here, we report two cases of SIH-induced SDH successfully treated
with simultaneous burr hole drainage and EBP, highlighting the clinical considerations
and potential benefits of this strategy.
Surgical Technique
Preparation Before the Technique
Under local anesthesia, the patient is positioned in the lateral decubitus position
with the affected side up (to facilitate burr hole drainage on the thicker hematoma
side) ([Fig. 1A ]). The head and the chosen epidural puncture site are prepared and draped separately
in a sterile fashion.
Fig. 1 (A ) The patient is placed in the lateral decubitus position and the side of the larger
hematoma facing upward, the puncture site and burr hole area are sterilized and exposed.
(B ) After creating a single burr hole, the hematoma cavity is accessed using an elaster
needle, with only the sheath left in place. The sheath is then secured to the bone
edge using bone wax. Before any hematoma outflow occurs, the pressure monitoring line
is connected. (C ) Intracranial pressure is assessed by measuring the mean arterial pressure displayed
on the monitor (yellow arrow). (D ) A small amount of contrast agent is injected through the epidural needle to confirm
proper placement in the epidural space, followed by autologous blood injection.
Burr Hole and ICP Monitor Placement
One burr hole is placed just above the thickest part of the hematoma (often in the
temporoparietal region). The dura is exposed but initially left intact. A small-gauge
needle is then inserted at a shallow angle through the dura into the SDH cavity, taking
care to avoid cortical injury ([Fig. 1B ]). Through this needle, an elastomeric catheter or needle sheath is introduced into
the subdural space and connected to an arterial pressure monitoring kit (DX-312, Nihon
Kohden, Tokyo, Japan) ([Fig. 1C ]). Baseline ICP is recorded before blood patch injection. If ICP is high at this
point, immediate drainage of the hematoma is to be considered.
Epidural Blood Patch Injection
Lumbar or cervical epidural punctures are performed at the level appropriate for the
suspected CSF leak. If the site of the leak is unknown, the lumbar level can be used
as a nontargeted patch. If a specific site of the leak has been identified (as in
case 2 below), the epidural needle can be placed close to that level. After confirming
the placement of the epidural needle, a small amount of contrast medium may be injected
to visualize the spread into the epidural space under fluoroscopy ([Fig. 1D ]). Next, autologous blood is slowly injected into the epidural space. During the
injection, the epidural ICP is continuously monitored and recorded.
Dynamic ICP Monitoring and Hematoma Drainage
During the EBP procedure, if the ICP remains within the predetermined safe range,
the entire preset volume of blood is injected. Conversely, if the ICP exceeds the
normal range (with our protocol employing a threshold of 20 mm Hg) or if an awake
patient experiences severe headache during the injection, blood injection is immediately
halted and hematoma evacuation is initiated without delay. In practice, once the ICP
surpasses 20 mm Hg or clear symptoms manifest, the injection is terminated and the
subdural space is immediately opened. A dural incision is made at the drill-hole site,
and partial evacuation of the SDH is performed until a trend toward ICP normalization
is observed. Subsequently, a closed subdural drainage catheter is inserted into the
hematoma cavity to facilitate continuous postoperative drainage. By tailoring the
timing of drainage to the trajectory of ICP elevation, pressure is released at the
juncture when sufficient CSF has been restored to enable appropriate cerebral expansion.
Case Presentation
Case.1
A 51-year-old male with no significant medical history presented with a progressively
worsening orthostatic headache lasting several days, without any identifiable precipitating
factors. He initially underwent computed tomography (CT) at a previous hospital, which
revealed a massive SDH, prompting an urgent transfer to our institution. On arrival,
his Glasgow Coma Scale score was E4V5M6, with no focal deficits. His voice was weak,
but he remained oriented. At that time, SIH was suspected. Brain CT revealed bilateral
SDH, predominantly on the right side ([Fig. 2A ]). Contrast-enhanced magnetic resonance imaging (MRI) demonstrated diffuse dural
thickening ([Fig. 2B ]). Fat-suppressed T2-weighted thoracic spine MRI showed a floating dural sac sign
from the lower cervical to mid-thoracic spine ([Fig. 2C ]), strongly suggesting coexisting SIH. However, on the following day, his condition
deteriorated to E3V4M6, with left oculomotor nerve palsy and poor responsiveness to
verbal stimuli—he was able to open his eyes to voice and weakly state his name and
the presence of a headache. Although dural puncture was essential for further localization
of the CSF leak, the presence of radiological uncal herniation and unilateral pupillary
dilation necessitated emergency simultaneous EBP and burr hole drainage.
Fig. 2 (A ) Noncontrast head computed tomography (CT) obtained at the initial presentation demonstrates
bilateral chronic subdural hematomas, more pronounced on the right side, accompanied
by evidence of brainstem compression and deformation. (B ) Contrast-enhanced magnetic resonance imaging (MRI) in the coronal plane reveals
diffuse dural enhancement including the tentorium cerebelli, indicative of spontaneous
intracranial hypotension (SIH). (C ) Fat-suppressed T2-weighted MRI shows the presence of the “floating dural sac sign,”
strongly indicative of concomitant intracranial hypotension syndrome.
Using the technique described above, we placed a right-sided burr hole with subdural
pressure monitoring and performed a lumbar EBP at L3–L4 (nontargeted, since the exact
leak site was not yet known). Before EBP, ICP was 14 mm Hg, which appeared relatively
low for young patients with a massive intracranial hematoma. After the start of the
epidural blood injection, ICP gradually increased to 36 mm Hg, prompting immediate
drainage. A closed subdural drain was left in place. He had complete resolution of
the headache and oculomotor palsy after the procedure. The follow-up CT confirmed
a significant reduction of the hematoma. He was discharged home without neurological
deficits. At 1-year follow-up, he remained symptom-free, and no recurrence of either
the SDH or the CSF leak was observed.
Case 2
A 31-year-old woman with no significant medical history presented to a referring hospital
with a progressively worsening orthostatic headache of several days' duration, with
no identifiable precipitating factors. Brain imaging revealed a significant amount
of right-sided SDH, which was suspected to be the primary cause of her headache ([Fig. 3A ]). Contrast-enhanced MRI did not show prominent diffuse dural thickening, but slit-like
ventricles and kissing thalami were observed, suggestive of low ICP. A previously
performed cisternography at the referring hospital demonstrated contrast leakage into
the epidural space at the C6–T2 level, confirming a spontaneous CSF leak ([Fig. 3B ]). Although EBP was considered for the first, the relatively large hematoma necessitated
a combined approach. Therefore, simultaneous burr hole drainage and EBP were performed.
Fig. 3 (A ) Coronal contrast-enhanced magnetic resonance imaging (MRI) shows a hematoma in the
right convexity, accompanied by collapse of the third ventricle and apposition of
the thalami. (B ) Computed tomography (CT) myelography reveals extradural leakage of contrast medium
along the ventral aspect of the dura mater, extending from the C6 to T2 levels.
The patient was taken to the operating room where a burr hole craniotomy was made
over the right convexity to drain the hematoma, and simultaneously a targeted high
cervical EBP was performed. The epidural needle was placed at the C6–C7 interspinous
level (just caudal to the known leak site) for blood injection. A subdural pressure
monitor was placed through the burr hole at the start of the procedure. As anticipated,
her baseline subdural pressure was in the low-normal range (around 11 mm Hg) despite
the large hematoma. After the injection of a small volume of blood into the epidural
space, the ICP began to climb. When the monitor showed pressures exceeding 20 mm Hg
and the patient reported a severe headache, the SDH was immediately decompressed.
The burr hole opening was widened and approximately 50 mL of old liquefied hematoma
was drained until the ICP dropped to a safe level. A subdural drain was then left
in place. The patient's headaches resolved promptly after the procedure. She had an
uncomplicated recovery and was discharged without any neurological deficits. At 12
months' follow-up, she remained well with no recurrence of the SDH and no further
SIH symptoms.
Discussion
These two cases demonstrate that combined burr hole drainage and EBP with simultaneous
monitoring of subdural ICP is a feasible and effective strategy for the management
of SDH associated with SIH. Both patients had SIH with large symptomatic SDHs and
were at high risk for clinical deterioration. Using our combined approach, we were
able to safely treat the CSF leak and hematoma in a single session without any intra-
or postoperative complications. After treatment, both patients improved promptly,
and there was no recurrence of SDH or SIH during the follow-up period. This experience
highlights the importance of treating both the low- and high-pressure aspects of this
condition in a controlled manner and shows that real-time ICP monitoring significantly
increases safety.
One of the main findings observed was the dynamic changes in ICP during EBP. In all
cases, despite the presence of very large hematomas, the initial subdural pressure
was relatively low (11–14 mm Hg). This is lower than the values expected in young
patients with relatively large SDH without SIH. For ICP in patients with pure SDH,
Sundstrøm et al (60 cases) reported a mean ICP of 15.6 mm Hg and Tanaka et al (15
cases) reported a mean ICP of 19.4 ± 3.7 mm Hg.[12 ]
[13 ] For this reason, it is likely that the two cases presented here were due to the
patient's potential CSF leak creating a low pressure environment, and the SDH expanded
without the accompanying increase in ICP that is generally seen in isolated SDHs.
Essentially, there was a “sagging” of the brain, and the fluid in the hematoma partially
compensated for the volume of lost CSF. This is consistent with clinical observations
that some SIH-related SDHs can grow despite the patient's ICP and mild symptoms.[4 ]
However, when the CSF volume was restored using EBP, the situation changed dramatically.
When EBP was started, ICP increased rapidly to over 30 mm Hg in both cases. The main
role of EBP in SIH is thought to be that it acts as a dura mater sealant and promotes
fibroblast activity and collagen formation in the epidural space.[14 ]
[15 ] However, in the short term, autologous blood injection into the spinal epidural
space is thought to increase hydrostatic pressure, and as a result, we may have seen
a rapid increase in ICP in SIH with SDH cases. If this acute rise in ICP is not recognized
and left unmanaged, it can lead to a serious risk of herniation and nerve damage.
In our protocol, continuous monitoring of ICP allowed us to immediately detect this
sudden rise and perform decompressive procedures on the hematoma at the precise moment.
As a result, ICP stabilized under controlled conditions. This real-time management
supports the concept that a combination of monitoring and procedures can effectively
adjust the balance of ICP immediately.
The safe volume of blood that can be injected safely into the epidural space in patients
with SIH who also have SDH has not yet been determined. In patients with pure hypotension
(SIH only), large volumes of blood patches (up to 20 mL or more, depending on the
puncture site) are often administered to ensure that the dural defect is sealed.[16 ]
[17 ]
[18 ] Transient ICP elevations are generally well tolerated due to intact intracranial
compliance. However, in the presence of a significant intracranial hematoma, intracranial
compliance is decreased, as evidenced by the observation of dramatic ICP elevations
with even small volumes of blood injected. Because SDHs occupy space, an increase
in hydrostatic pressure at the puncture site of EBP will result in a direct increase
in ICP. This suggests that a more cautious approach is needed in SIH cases involving
SDHs. Further research is needed to determine the optimal EBP injection volume and
injection speed in order to minimize sudden rises in ICP and maximize treatment success
rates, but it is likely that a smaller amount of EBP may be adequate in cases involving
SIH with SDH.
As well as the amount and speed of blood injection, careful attention must be paid
to the condition of the spinal canal before injection. EBP requires particular caution
in patients with specific comorbidities. For instance, patients with epidural adhesions
due to previous lumbar surgery or those with significant lumbar spinal stenosis may
experience worsening neurological symptoms, such as radiculopathy or neurogenic claudication.[19 ] Therefore, preprocedural imaging, such as MRI or CT myelography, should be performed
to identify at levels free from stenosis or adhesions, thereby minimizing procedural
risks. Another concerning comorbidity is that in patients receiving antiplatelet or
anticoagulant therapy, clinical guidelines regarding the timing of drug discontinuation
prior to EBP should be followed.[20 ]
[21 ] In urgent cases necessitating immediate intervention, EBP might be performed under
appropriate reversal agents or hemostatic support. Nevertheless, clinicians must remain
vigilant and be prepared for emergent hematoma evacuation following the procedure,
given the elevated risk of bleeding.
While there are several important points that warrant careful attention, the usefulness
of our simultaneous treatment strategy is consistent with recent reports. Terakado
et al reported two similar cases of bilateral SDH and SIH, in which they first performed
subdural drainage and ICP monitoring, followed by EBP.[7 ] Similarly, Engrand et al documented the gradual transmission of lumbar intrathecal
pressure to ICP during sequential EBP procedures.[22 ] These reports correspond to staged versions of our simultaneous approach, but emphasize
the usefulness of real-time ICP visualization for safely controlling ICP and dealing
with CP elevation during EBP. However, Takahashi et al suggest that patients who undergo
SDH surgery first may require additional treatment and may sometimes experience complications.[9 ] Therefore, our combined therapy is beneficial for patients with SIH who have SDH,
as it allows ICP to be safely controlled by ICP monitoring while reducing the risk
of sequential therapy and conservative approaches.
Even with the implementation of EBP procedures, residual symptoms of SIH and recurrence
of SDH remain possible. According to several studies, single session frequently fails
to provide sufficient therapeutic effect for SIH patients.[23 ]
[24 ] In such cases, repeated EBPs have been reported to be effective and represent a
treatment option.[23 ] Furthermore, in cases with spinal fluid leak accurately identified by screening,
targeted EBP, or surgical repair of the dural defect under general anesthesia, can
be a more effective strategy to treat and prevent leakage.[25 ]
[26 ] Regardless of which treatment option is adopted at the time of recurrence, the changes
in ICP during SIH treatment should be carefully considered.
Conclusion
We report two cases of SIH-associated SDH successfully treated with simultaneous burr
hole drainage and EBP, with real-time ICP monitoring. Real-time ICP monitoring allows
precise control of intracranial dynamics, preventing dangerous pressure fluctuations.
Further research is needed to refine this approach, yet our results support the use
of combined therapy for SIH-associated SDH patients.
