Spontaneous intracranial hypotension (SIH) is caused by cerebrospinal fluid (CSF) leakage and subsequent hypovolemia in the spinal subarachnoid membrane or, rarely, the intracranial space [1]. The major clinical manifestation is a postural headache caused by low cerebrospinal fluid pressure, especially in the upright position. However, patients with SIH can also experience nonpostural headaches, dizziness, nuchal discomfort, nausea, vomiting, diplopia, and blurred vision [2]. During imaging, brain sagging, narrowing of the cisterns around the brainstem (such as the suprasellar or prepontine cistern), and subdural fluid collection can be observed with SIH [3].

Depending on the severity and duration of symptoms, conservative therapy, including bed rest, oral hydration, oral caffeine intake, analgesics, and epidural blood patch (EBP) application, can be administered; however, rarely, dura repair may be performed. Recently, the use of targeted fibrin glue injection for the treatment of refractory SIH has been reported [4]. Subdural fluid collection and subdural hemorrhage (SDH) are complications of SIH, which include subdural hygroma and hematoma caused by the persistence of negative pressure. Most patients with SIH experience a self-limiting course with conservative treatment. However, SDH rarely results from the tearing of bridging veins or bleeding from engorged veins in the subdural space. If the hemorrhage volume is too high, then the patient’s mental status can deteriorate rapidly, and emergent surgery is required [5]. We report a case of SIH with SDH in a patient who underwent surgical hematoma evacuation before EBP.

1. Case 1

A 60-year-old man presented to our emergency department with an orthostatic headache in the frontal area (numeric pain rating scale score, 5), nausea, and vomiting for 3 days. The patient had no relevant medical history and had not experienced any traumatic events. The neurological examination revealed no abnormal findings. His vital signs were stable during the examination in the emergency department. SIH was suspected; therefore, the patient was admitted to the neurosurgery department. Brain computed tomography (CT) without contrast showed subacute SDH, narrowing of the suprasellar cistern, and sagging of the brainstem (Fig. 1). Because the patient reported typical SIH symptoms, the attending physician decided to initiate conservative treatment including hydration, bed rest, intravenous Cerebrolysin 20 ml/day, intravenous 20% mannitol 60 g/day, oral ketorolac 10 mg three times per day, and oral acetaminophen 650 mg three times per day; however, his headache persisted. Magnetic resonance imaging (MRI) myelography revealed a small dural diverticulum in the left neural foramen at the C7/T1 level. Two days after treatment administration, the patient was referred to our pain clinic for EBP. During the consultation with a physician specializing in pain medicine, it was noted that his symptoms were not typical of SIH at that time. The patient reported a persistent headache regardless of position and general malaise. Mild disorientation was also observed. A further evaluation of the headache was recommended to rule out surgical indications. After 6 hours, he gradually manifested drowsiness and was transferred to the intensive care unit for observation. Although the follow-up brain CT examination results showed no interval changes when compared to the results of the previous examination, his right pupil was dilated to 6 mm with no light reflex; therefore, he underwent emergent burrhole trephination to evacuate the SDH. After successful surgery, the dilated pupil normalized. Additionally, his pupil reflex and mental state stabilized, but his headache persisted. Two days after surgery, the patient was referred to our pain clinic again for EBP application to manage his persistent headache attributable to SIH. An EBP at L3/4 with 20 ml autologous blood from his cephalic vein was applied. The next day, he presented with an aggravated headache (numeric pain rating scale score, 7-8), disorientation regarding time and place, and motor aphasia. Follow-up brain CT and MRI examinations showed a decreased SDH; however, acute infarctions in both basal ganglia, left parieto-temporo-occipital lobes, right parieto-temporal lobe, and both temporal lobes were observed (Fig. 2). With conservative management including hydration, analgesics, and sedatives, his disorientation resolved and headache improved (numeric pain rating scale score, 2-3) after 10 days. Two weeks after the lumbar EBP, his headache worsened progressively (numeric pain rating scale score, 5-6), and a follow-up brain CT examination showed increased subdural hygroma (Fig. 3). The attending physician requested a second EBP; therefore, a C-arm-guided EBP was applied at C7/T1 with 10 ml autologous blood from his cephalic vein. His headache significantly improved (numeric pain rating scale score, 1-2). During the next 3 days, his symptoms, including headache, completely resolved, and he was discharged with instructions to return for a follow-up outpatient appointment.

Figure 1. Computed tomography (CT) image without contrast of the brain showing subdural hemorrhage (SDH) (asterisk), sagging of the brainstem (white arrow), and narrowing of the suprasellar cistern (black arrow).

Figure 2. Magnetic resonance diffusion view showing acute infarctions in both basal ganglia, left parieto-temporo-occipital lobes, right parieto-temporal lobe, and both temporal lobes (white arrow).

Figure 3. Follow-up brain CT showed increased subdural hygroma with enlarged hemorrhage.

2. Case 2

A previously healthy 43-year-old man visited our outpatient department of neurology with symptoms including posterior neck pain, right-hand numbness, and orthostatic frontal headache that had occurred after swimming 4 months previously. No specific findings other than ossification of the posterior longitudinal ligament were observed on brain CT and spine MRI images obtained at other hospitals. The patient was prescribed a non-steroidal anti-inflammatory drug. A month previously, the headache became worse (numeric pain rating scale score, 4-5), and 3 days previously, mild amnestic disorder and symptoms, such as not being able to find his house, occurred. Neurological examination revealed no abnormal findings, and his vital signs were stable. To rule out a cervicogenic headache, the outpatient electromyography and nerve conduction study was planned. The patient was presented to our emergency department due to worsened acute memory impairment and intermittent drowsy mentality for the past five days. Upon arrival, his mental state was alert and his motor and sensory orientations were intact. Brain CT revealed subdural effusion or hemorrhage in both cerebral hemispheres and sagging of the brainstem (Fig. 4). SIH with SDH was suspected, and the patient was referred to the neurosurgery department. The attending physician initiated conservative treatment including hydration, bed rest, oral acetaminophen 650 mg three times per day, oral zaltoprofen 80 mg three times per day, and oral levetiracetam 500 mg two times per day. The next day, brain MRI images showed SDH with dural thickening in both cerebral hemispheres, sagging of the brainstem, obliteration of basal cisterns, and bilateral uncal herniation; furthermore, the patient gradually manifested drowsiness. Therefore, he underwent emergent burrhole trephination to evacuate the SDH under general anesthesia. He was transferred to the intensive care unit for postoperative care and mechanical ventilation. After 2 hours, extubation was performed, and the patient was able to obey the physician’s verbal orders without motor weakness. The following day, his mental status stabilized, but he still reported postural headache (numeric pain rating scale 3-4) and mild dizziness. Five days after surgery, MRI myelography showed CSF leakage at the C-T junction, especially at the left C5/6 level (Fig. 4); therefore, the patient was referred to our pain clinic for EBP. A C-arm-guided EBP at C7/T1 with 10 ml autologous blood from his cephalic vein was applied. Three days after EBP, his headache disappeared. He was discharged with instructions to follow-up with the outpatient department.

Figure 4. MRI myelography showed CSF leakage at the C-T junction, especially at the left C5/6 level (red arrows). Brain CT showed subdural hemorrhage in both cerebral hemispheres and sagging of brainstem.

Subdural fluid collection is a rare complication of SIH that includes subdural hygroma and hematoma caused by the persistence of negative pressure. Usually, SIH has a benign clinical course. However, after subdural fluid collects, SIH can manifest as multiple neurologic deficits (e.g., hearing disturbances, dizziness, and transient diplopia) [6]. If the hemorrhage volume is so large that it changes the patient’s mental status, then emergency evacuation of the hematoma could be necessary [5]. However, SIH can present with various symptoms. The patient’s condition can rapidly deteriorate if the overlapping clinical features of SDH are neglected and not managed immediately.

Our patient had a typical postural headache with nausea and vomiting, and the CT examination showed narrowing of the suprasellar cistern and sagging of the brainstem indicative of SIH, even though the SDH volume was small. Magnetic resonance myelography also showed a small dural diverticulum in the left neural foramen at the C7/T1 level, which is classified as another type of SIH. The most recognized type comprises a linear tear in the dura located ventral or posterolateral to the spinal cord. Another type comprises leakage at meningeal diverticula sites (Tarlov cysts) or diffuse dilatations of the dural sac (dural ectasia). A further type comprises a spinal CSF-venous fistula that abnormally communicates with the subarachnoid space, adjacent veins, and meningeal diverticula [7]. Although the patient was experiencing other unrepresented symptoms that may have caused the deterioration of his condition, he reported typical symptoms of SIH. Hence, the attending physician referred him to our pain clinic for EBP without hesitation. Chen et al. [8] reported that the main warning signs of SDH are a transformed headache pattern or new persistent headache, acute alteration of consciousness, and unexpected severe headache far worse than previous headaches or thunderclap headache.

Several mechanisms of SDH with SIH have been suggested. First, intracranial hypotension can cause the brain to sink and rupture the bridging veins by pulling away from the dura [9]. Second, intracranial venous engorgement and new dural vessels secondary to intracranial hypotension can cause fragility of the bridging veins [10]. Third, the subdural fluid collection can contribute to SDH by enlarging the subdural space and increasing the stress on the bridging veins by causing stretching [11]. Focal neurological signs manifest as brainstem compression, and these signs are often associated with the disturbance of consciousness [8].

Acute cerebral infarction occurred in both the posterior and middle cerebral artery territories in our patient 3 days after hematoma evacuation; therefore, this was also a rare case of acute arterial cerebral infarction with SIH [12,13]. According to the literature, the pathophysiological hypothesis is that mechanical stretching causes stress on the cerebral arteries and induces arterial occlusion as a result of sagging of the brainstem and effacement of the subarachnoid cisterns that mimic brain edema [12]. Another suggested cause is the opening of the subarachnoid space to the air, which can make the CSF less buoyant, accelerate sagging of the brain, and cause brain sagging associated with Duret hemorrhage, thus reflecting the rapid deterioration of the brain structures and transtentorial herniation [13]. These mechanisms can cause a paradoxical increase in intracranial pressure, reduction in cerebral perfusion pressure, and reduction in cerebral blood flow.

Depending on the severity and duration of symptoms, a short course of conservative management can be initiated. After conservative treatment, most patients with SIH can achieve satisfactory improvement. If conservative measures fail, then an EBP, which immediately increases the CSF pressure accompanying an epidural hematoma, can be applied. Recently, epidural fibrin glue patches targeted at the leakage site have been used for patients with persistent and recurrent SIH, regardless of EBP application. Our patient was diagnosed with SIH and SDH and progressively lost consciousness; therefore, we recommended further evaluation and considered surgical options such as burr hole drainage. After he recovered consciousness, a lumbar EBP was applied to treat the remaining headache. However, the headache did not improve completely. Therefore, a cervical EBP was applied, resulting in the complete disappearance of his headache. Patients diagnosed with SIH are mainly referred to the pain clinic for EBP application. Attending physicians believe that EBP application by a clinician specializing in pain medicine is a relatively safe and easy procedure for patients. Although a rare complication, SDH secondary to SIH varies from a thin subdural hygroma to a large SDH. Patients with SIH require monitoring of their neurologic signs so that emergency conditions are not missed. A large-volume SDH and altered state of consciousness are indications for urgent evacuation. Even when a small hematoma is initially observed using CT, early surgical interventions are required when neurologic symptoms develop.

In conclusion, a physician specializing in pain medicine should be alerted to the presence of SDH with unusual SIH symptoms that could require evacuation before an EBP is considered. It is particularly important to consider the characteristics of newly developed headaches and sudden deterioration of consciousness when patients present with SIH.

The Institutional Review Board of the Hallym University Sacred Heart Hospital (IORG0004993, IRB00005964), Project No. HALLYM 2023-01-014.

None.

No potential conflict of interest relevant to this article was reported.