Trends in prior antithrombotic medication and risk of in-hospital mortality after spontaneous intracerebral hemorrhage: the J-ICH registry.

Spontaneous intracerebral hemorrhage (SICH) remains a devastating form of stroke. Prior use of antiplatelets or warfarin before SICH is associated with poor outcomes, but the effects of direct oral anticoagulants (DOACs) remain unclear. This study aimed to clarify trends in prior antithrombotic use and to assess the associations between prior use of antithrombotics and in-hospital mortality using a multicenter prospective registry in Japan. In total, 1085 patients were analyzed. Prior antithrombotic medication included antiplatelets in 14.2%, oral anticoagulants in 8.1%, and both in 1.8%. Prior warfarin use was significantly associated with in-hospital mortality (odds ratio [OR] 5.50, 95% confidence interval [CI] 1.30-23.26, P < 0.05) compared to no prior antithrombotic use. No such association was evident between prior DOAC use and no prior antithrombotic use (OR 1.34, 95% CI 0.44-4.05, P = 0.606). Concomitant use of antiplatelets and warfarin further increased the in-hospital mortality rate (37.5%) compared to warfarin alone (17.2%), but no such association was found for antiplatelets plus DOACs (8.3%) compared to DOACs alone (11.9%). Prior use of warfarin remains an independent risk factor for in-hospital mortality after SICH in the era of DOACs. Further strategies are warranted to reduce SICH among patients receiving oral anticoagulants and to prevent serious outcomes.

Spinal endodermal cyst undergoing malignant transformation and marked elevation of serum carbohydrate 19-9 level.

Endodermal cyst (EC) is a benign tumor that can arise along the craniospinal axis. Infrequently, ECs undergo malignant transformation. A 43-year-old man presented with numbness in the right arm, leg and occipitalgia. MRI revealed a multicystic, intradural extramedullary tumor at C2 with enhancement along the ventral surface of the spinal cord. Blood test showed an abnormal increase in serum carbohydrate antigen 19-9 (CA 19-9) level. Systemic positron emission tomography-computed tomography was normal. He underwent total tumor resection and was diagnosed with EC. He developed double vision, hearing loss, and swallowing difficulty on postoperative day 70. Cerebral MRI revealed marked extensions of leptomeningeal dissemination. The serum CA 19-9 level increased continuously and finally reached 1515.0 U/ml. He died of respiratory failure on day 108. An autopsy did not reveal abnormalities in the abdominal and chest organs. On microscopic examination, the post-mortem specimen revealed adenocarcinoma. Immunohistochemically, both the surgical and autopsy specimens were positive for CA 19-9. Spinal ECs may lead to malignant transformation with leptomeningeal dissemination that causes abnormal elevation of serum CA 19-9 levels.

The Superior Ophthalmic Vein: Anatomical Perspective for Transvenous Access to the Cavernous Sinus.

The anatomical characteristics of the superior ophthalmic vein (SOV), which is crucial when performing craniofacial surgeries and transvenous access to the cavernous sinus, have not been documented. The present study aimed to explore them using magnetic resonance angiography (MRA). A volumetric, phase-contrast MRA was performed in 74 outpatients not bearing vascular or tumorous pathologies in the face, orbit, and cavernous sinus. The entire course of the SOV was delineated in 46 patients (62%), for 76% on the right side and 83% on the left. These SOVs consistently showed a characteristic morphology with a laterally coursing proximal segment and a medially coursing distal segment. The latter segment was connected to the angular, supraorbital, supratrochlear, facial, and external nasal veins that were inconsistently delineated. The angular vein was tortuous in 51% of the patients on the right and 53% on the left. The morphology of the proximal part of the SOV was also variable and involved a tortuous segment in 11% of the patients on the right and in 7% on the left. Furthermore, in 4 patients (8.7%), a fenestration was found in the right SOVs. Inconsistent tributaries of the SOV, tortuous angular vein, and possible tortuous segment and fenestration of the SOV can make orbital transvenous access to the cavernous sinus difficult.

Diploic veins of the cranial base: an anatomical study using magnetic resonance imaging.

PURPOSE: The anatomy and distribution of the diploic veins (DVs) of the cranial base have not been fully documented. The aim of this study was to characterize these veins using contrast magnetic resonance imaging (MRI). METHODS: In total, 95 patients underwent thin-sliced, contrast MRI. Coronal and sagittal images were used for the analysis. The cranial base was divided into the anterior, middle, and posterior bases. Then, each base was further subdivided into three equal parts in the anteroposterior and lateromedial directions. The anteroposterior parts were evaluated on coronal images, while the lateromedial parts were evaluated on sagittal images. RESULTS: The DVs were identified over the entire cranial base. However, they were more frequent in the posterior-third of the lateral-third region of the anterior, middle-third of the lateral and middle-third regions of the middle, and middle-third region of the posterior cranial base, and sparse in the posterior and medial-third regions of the middle cranial base. The DVs showed marked morphological variability. For instance, the DVs of the pterional area were generally well defined, as pivotal channels connecting the lateral parts of the anterior and middle cranial base, but were highly varied in appearance. CONCLUSIONS: The DVs of the cranial base are distinct structures characterized by morphological variability and topographical predilection. Contrast MRI is useful for delineating these veins.

Possible cerebrospinal fluid pathways in the middle fossa floor and pterional diploe: a magnetic resonance imaging study.

PURPOSE: There has not been a study documenting the distribution of cerebrospinal fluid (CSF) pathways in the anterolateral base of the middle fossa (ALB) and diploe of the pterional region (Pt). The present study aimed to delineate these pathways using magnetic resonance imaging. METHODS: Thin-sliced, axial, and coronal T2-weighted sequences were performed for a total of 358 outpatients, including 20 pediatric patients. RESULTS: Adult population: CSF-filled channels were identified on axial images in the ALB in 57% and in the diploe of the Pt in 65% of 338 patients. These pathways showed variable morphology and number bilaterally. CSF-filled channels were identified on coronal images in the ALB in 14% and in the diploe of the Pt in 100% of 59 patients. These were delineated as linear structures of variable number and thickness. Eleven percent of the pathways identified in the ALB was connected with extracranial channels. Pediatric population: CSF-filled channels were identified on axial images in the ALB in 75% and in the diploe of the Pt in 80% of 20 patients. CONCLUSIONS: The ALB and diploe of the Pt may function as CSF pathways in children and adults. The pathways in the ALB can be a CSF-drainage route connecting to the extracranial sites.

The intracanalicular segment of the hypoglossal nerve: An anatomical study using magnetic resonance imaging.

Few studies have documented the morphology of the intracanalicular segment of the hypoglossal nerve (CSHN). Therefore, the aim of this study was to characterize the CSHN using magnetic resonance imaging (MRI). In total, 95 patients underwent thin-sliced, contrast MRI. The axial and coronal images were used for analysis. The CSHNs were bilaterally identified in 97% and 94% of the 95 patients on the axial and serial coronal images, respectively. On axial images, length of the hypoglossal canal was measured as 8.2 ±â€¯1.66 mm on the right and 8.4 ±â€¯1.71 mm on the left. The CSHN was delineated as a slightly tortuous, linear structure with variable length. The CSHN course in the hypoglossal canal could be classified into the ventral, central, and ventrodorsal types, with the ventral type most predominant and found in 65% on the right side and 43% on the left. The angle formed by the CSHN and perpendicular line was highly variable. On serial coronal images, the CSHN course in the hypoglossal canal was also variable and could be found in the any part of the canal. The CSHN is a distinct structure characterized by morphological variability, which can influence the type of hypoglossal neuropathy arising from the CSHN.

Does the prone sleeping position affect the intracranial dural venous flow?

PURPOSE: There are few studies documenting the effect of posture on intracranial dural venous flow. The aim of the present study was to explore alterations caused by the prone position using magnetic resonance (MR) venography. METHODS: A total of eight patients (five men and three women) underwent non-contrast MR venography in both supine and prone positions. RESULTS: In the prone position, an increase in intracranial dural venous flow was found in all patients in the non-dominant transverse and sigmoid sinuses. An increase in venous flow to the straight sinus was observed in 75% of the patients. Flow to the superior ophthalmic vein decreased in three patients. No postural flow alterations were observed in any of the patients in the superior sagittal, dominant transverse, and sigmoid sinuses. CONCLUSION: Based on results of the study, in the prone sleeping position, part of the intracranial venous flow may be preferentially drained through the straight and non-dominant transverse sinuses.

Vertebral artery segment at the suboccipital dural penetration site: an anatomical study using magnetic resonance imaging.

PURPOSE: The morphology of the vertebral artery (VA) segment at the suboccipital dural penetration site has little been explored with magnetic resonance imaging (MRI). Therefore, the aim of this study was to examine the structure using MRI. METHODS: In total, 94 patients underwent thin-sliced, contrast MRI in the axial, coronal, and sagittal planes involving the atlas, axis, occipital bone, and V3 and V4 segments of the VA. RESULTS: The VA segment at the suboccipital dural penetration site was well-delineated in 93% on the axial images and in 95% on the coronal images. The axial images showed that 82% of the VA penetration sites were located in the middle third of the dural sac. Meanwhile, the coronal images revealed that the heights of both VA penetration sites were located at the same level in 87%. The axial VA penetration angle, which is formed by the VA and tangential line of the dural sac, was 66 ± 11.9° on the right side and 61 ± 14.1° on the left side. The coronal VA penetration angle, which is formed by the tangential line of the VA and dural sac, was 111 ± 24.6° on the right side and 112 ± 19.9° on the left side. CONCLUSIONS: The morphology of the VA segment is considerably variable at the suboccipital dural penetration site, while most penetration sites are located in the middle third of the dural sac on axial MRI. These should be assumed during surgeries around the suboccipital VA penetration site.

An undescribed venous pathway intervening between the olfactory fossa and nasal vestibule.

PURPOSE: A curvilinear pathway intervening between the olfactory fossa and nasal vestibule has not been well documented. Therefore, the aim of this study was to examine its structure using magnetic resonance imaging (MRI). METHODS: In total, 84 patients underwent thin-sliced, contrast MRI. Among these patients, 31 underwent additional thin-sliced, sagittal T2-weighted imaging. RESULTS: A curvilinear pathway intervening between the olfactory fossa and nasal vestibule was delineated on sagittal and coronal imaging in 98% and 82% of patients, respectively. All of these pathways demonstrated communication with the lower limit of the superior sagittal sinus (SSS) or fine venous channels connecting to the SSS in the vicinity of the crista galli. The pathway was identified in the parasagittal regions on both sides with varying lengths, diameters, and curvatures. In 94% of the patients who underwent sagittal T2-weighted imaging, the pathways appeared as linear high-intensity signals. Most pathways were delineated as a single channel coursing extracranially adjacent to the olfactory fossa. In 38% of the patients, post-contrast sagittal images showed variable filling defects between the olfactory bulb and floor of the olfactory fossa, furthermore traversing the venous pathway. Additionally, in 73% of the patients, post-contrast images identified diploic venous channels, variably in the nasal bone and communicating with the venous pathway. CONCLUSIONS: A curvilinear pathway intervening between the olfactory fossa and nasal vestibule is a consistent venous structure and may function as an extracranial route of cerebrospinal fluid drainage.

The diaphragma sellae, diaphragm opening, and subdiaphragmatic cistern: an anatomical study using magnetic resonance imaging.

PURPOSE: Few studies have explored the detailed morphology of the diaphragma sellae (DS), diaphragm opening (DO) or stoma, and subdiaphragmatic cistern (SDC) using neuroimages. The aim of the present study was to characterize these structures using magnetic resonance imaging. METHODS: Thin-sliced, sagittal and coronal T2-weighted imaging was performed for a total of 84 outpatients. RESULTS: The DS, DO, SDC, and relevant structures were consistently delineated in all patients. In 66% of patients, all three structures appeared to be highly variable, and were classifiable as six distinct morphological types. In 4% of patients, the DS presented as a complete sheet lacking a discernible DO. In addition, 30% of the patients presented with undiscernible SDCs. In the coronal sections of 11% of patients, the pituitary glands extended laterally, reaching or extending beyond the center line on the sectional image of the cavernous internal carotid artery. CONCLUSIONS: Thin-sliced, sagittal, and coronal T2-weighted sequences are useful for delineating the DS, DO, and SDC. Morphological variation of these structures among individuals may considerably influence the direction of pituitary tumor expansion.

Visualization of the supraorbital notch/foramen using magnetic resonance imaging.

The supraorbital notch/foramen involving the segment of the supraorbital nerve (SON) and the supraorbital artery (SOA) has little been explored with magnetic resonance imaging (MRI). Therefore, we explored these structures using MRI. A total of 90 patients underwent thin-sliced contrast MRI. In addition, eight sides of the orbits were dissected in four cadaveric heads. Cadaver dissections showed that the SOA coursed consistently beneath and in close proximity to the SON and reached the supraorbital notch/foramen. On axial MRI images, the supraorbital notch/foramen was identified in 98% on the right side and in 99% on the left. The distance from the midline to the midpoint of the supraorbital notch/foramen and depth from the skin surface to the supraorbital foramen/exit were measured. The median distance was 22.6 ±â€¯3.08 mm on the right side and 22.8 ±â€¯3.07 mm on the left, whereas the depth was 7.7 ±â€¯1.39 mm on the right and 7.7 ±â€¯1.43 mm on the left. Eighty percent of the sagittal images showed well-developed diploic veins in the supraorbital rim. Of these, 8.3% had anastomotic channels with the subcutaneous veins through the anterior wall of the supraorbital rim, 11.8% through the inferior wall, and 9% through the SOF. The SON and SOA segments passing through the supraorbital exit can be reliably located using contrast MRI. The supraorbital rim may function as the intracranial to extracranial anastomotic channel.

Interdural high signal on CISS sequence: an alternative CSF pathway?

PURPOSE: The falx cerebri, falx cerebelli, and tentorial notch exhibit a peculiar morphology with a two-layered, dural leaf that protrudes into the cranial cavity with a free edge. However, there are few studies exploring this morphology using neuroimaging techniques. The present study aimed to explore these dural structures using magnetic resonance imaging. METHODS: A total of 65 outpatients were included in this study. Following initial examinations with conventional sequences, the constructive interference in steady-state (CISS) sequences were performed in thin-sliced, coronal sections. RESULTS: In 78% of the subjects, the interdural spaces presenting with high signal were identified in the falx cerebri. These spaces were located adjacent to the uppermost part of the falx, formed by two dural leaves and the superior sagittal sinus, and tapered downward where the leaves united to form the falx cerebri. At the tentorial notch, these spaces were found in 52% of the 65, most predominantly in the medial edge followed by the tentorium cerebelli-tentorial notch junctional region. Forty-one percent of patients had a dural opening into the cerebral cistern. The interdural spaces with high signal were not identified in the tentorium cerebelli in any of the subjects. CONCLUSIONS: The falx cerebri and tentorial notch form the interdural spaces that may provide alternative cerebrospinal fluid pathways. The coronal CISS sequence is suitable for delineating such interdural spaces.

Venous channels of the falx cerebri in adult Japanese population: delineation using magnetic resonance imaging.

PURPOSE: Few studies have characterized the venous channels of the falx cerebri under physiological conditions. The present study aimed to explore the falx cerebri using magnetic resonance imaging (MRI). METHODS: A total of 91 patients (41 men and 50 women) with an intact falx cerebri and relevant dural sinuses underwent contrast MRI. RESULTS: In 15% of the participants, the falx cerebri contained venous channels with a patchy appearance. Seven of these channels were located in the anterior third of the falx, two were in the anterior two-thirds, and 5 were in the middle third. In 19 (21%) participants, the falcine sinus was unequivocally delineated. In 14 of them, connected the posterior third of the superior sagittal sinus and uppermost part of the straight sinus. These sinuses showed variable morphologies, presenting with linear, triangular, multi-channel, and branching appearances. The linear type was the most predominant and found in 50% of these cases. In contrast, in the remaining five participants, the falcine sinuses were coursing posteriorly, connecting the posterior third of the falx cerebri with the superior sagittal sinus. CONCLUSION: The falx cerebri may have a role as a pathway in the intracranial venous circulation. The falcine sinus has several variants with diverse morphologies.

Orbital Arteriovenous Fistula Coexistent with an Arteriovenous Hemangioma: A Rare Occurrence and Review of Literature.

BACKGROUND: Orbital arteriovenous fistula (AVF) is a rare entity with only 17 cases reported so far. An arteriovenous hemangioma is a distinct entity of an angioma that most frequently affects the skin. However, to our knowledge, there has not been a case arising in the orbit. CASE DESCRIPTION: A previously healthy, 73-year-old man had progressive proptosis for 1 month. At presentation, the patient showed considerable proptosis, hyperemia in the lower eyelid, chemosis, and total ophthalmoplegia on the right side. Computed tomography and magnetic resonance imaging revealed a round retro-orbital mass, 23 mm in maximal dimension, and lying in the inferomedial aspect of the orbit with an irregular-shaped lesion in the orbital apex. Cerebral angiography detected an orbital AVF fed by the ipsilateral maxillary and ophthalmic arteries and draining into the inferior ophthalmic vein. Stain of the retro-orbital mass was not identified. A transvenous coil embolization via the facial and superior ophthalmic veins achieved complete isolation of the AVF with satisfactory outcome. Two months later, the orbital mass, well circumscribed and lacking perilesional hemosiderin deposition, was microsurgically resected via a lateral orbitotomy. Histological diagnosis was consistent with an arteriovenous hemangioma. CONCLUSIONS: An AVF and arteriovenous hemangioma may simultaneously develop in the same orbit. In patients with symptomatic orbital AVF and coexisting other orbital pathology, strategies should be carefully planned before setting about the treatment.

The trigeminal root: an anatomical study using magnetic resonance imaging.

PURPOSE: The trigeminal root is a remarkable structure that can be an original site of trigeminal neuralgia. However, few studies have explored the detailed anatomy of it with neuroimages. The aim of the present study was to characterize the trigeminal root using magnetic resonance (MR) imaging. METHODS: Thin-sliced, axial T2-weighted imaging and coronal constructive interference in steady-state (CISS) sequence were performed for a total of 167 patients. RESULTS: On axial T2-weighted imaging, three divisions of the main trigeminal sensory root were unequivocally delineated in 36% of the 95 patients. Sixty-three percent of the Meckel's cave was bilaterally adjacent to the petrous portion of the internal carotid artery. On CISS sequence, course of the main trigeminal sensory root was well delineated in all of the 72 patients. The accessory sensory and motor rootlets were identified in 38% and 56% of 144 sides, respectively. Levels of the main trigeminal roots at the original site and entrance into the Meckel's as well morphology of the original segment of the main trigeminal sensory root were variable. Furthermore, in 24% of sides, three divisions of the main trigeminal sensory root were clearly delineated, arranged in variable manners. In 20% sides, segments of the superior cerebellar artery had a contact with the main trigeminal sensory root and motor rootlets. CONCLUSIONS: Coronal CISS sequence is useful for delineating the trigeminal root. Anatomy of the trigeminal root presents considerable inter- and intra-individual variability that can influence the symptoms of trigeminal neurovascular compression.

Visualization of the vidian canal and nerve using magnetic resonance imaging.

BACKGROUND AND PURPOSE: Few studies have investigated the vidian nerve (VN) and vidian canal (VC) with the use of magnetic resonance imaging (MRI). The present study aimed to characterize the VC and VN using MRI. MATERIALS AND METHODS: A total of 91 patients underwent thin-sliced, contrast MRI. The course of the VC and VN and the relationships with relevant structures were analyzed. RESULTS: The VC was identified in 95% of axial images on the right side and in 93% on the left. The course of the VC was delineated in 99% of serial coronal images on both sides. The VN location in the VC was highly variable. The course of the VC and transmitting VN was delineated in 95% of sagittal images on the right side and in 91% on the left. The mean length of the VC was 19.8 mm on the right side and 19.3 mm on the left. Topographical relationships between the anterior genu of the petrous internal carotid artery and the posterior end of the vidian canal could be classified into three types. Of these, the type terminating at the level of the petrous carotid was the most predominant, comprising 76% of 182 sides. The course of the VC and transmitting VN could be classified into four types. The straight type was the most predominant and was found in 41%. CONCLUSIONS: The VC and transmitting VN are structures with variable morphologies. Contrast MRI is useful for delineating the VC and VN.

Atypical epidural hemangiopericytoma presenting with visual disturbance.

BACKGROUND: Hemangiopericytomas are a rare entity commonly presenting as subdural tumors. CASE DESCRIPTION: A 57-year-old man presented with a progressive visual disturbance over a period of 3 weeks. Cranial computed tomography scans revealed an isodense mass at the tip of the left middle fossa, extending into the orbital apex, and accompanying bony erosions in the sphenoid ridge. On magnetic resonance imaging, the lesion appeared isointense both on T1- and T2-weighted sequences, and intensely enhanced on contrast examinations. A frontotemporal craniotomy revealed a dura-based, capsulized tumor located entirely in the epidural space. A gross total resection was achieved for the tumor and histologically verified as hemangiopericytoma. CONCLUSION: Hemangiopericytoma should be assumed in a differential diagnosis when encountering epidural tumors, and total resection should be attempted when possible.

Visualization of the periventricular Virchow-Robin spaces with ependymal openings.

PURPOSE: The morphological relationships between the periventricular Virchow-Robin spaces (VRSs) and cerebral ventricles have been poorly documented. The present study aimed to explore the issue using magnetic resonance imaging. METHODS: A total of 211 patients were included in this study. T2-weighted and constructive interference in steady state (CISS) sequences were performed in thin-sliced, coronal sections. RESULTS: On T2-weighted sequence, the periventricular VRSs with ependymal openings were identified in 34% of 139 subjects. All the openings were located in the lateral wall of the anterior horn. In CISS sequences, such VRSs were found in 39% of 72 subjects. The mean age was significantly higher in the population with such VRSs compared to those without VRSs (p = 0.0047). Of the 58 periventricular VRSs with ependymal openings identified on T2-weighted images, 16% were located in the upper, 36% in the middle, and 48% in the lower part of the lateral wall. Of the 38 such VRSs identified on CISS images, 32% were located in the upper, 24% in the middle, and 42% in the lower part of the lateral wall, and 3% in the upper part of the medial wall. CONCLUSIONS: The ependymal openings of the periventricular VRSs may be centered in the lateral wall of the anterior horn. The coronal CISS sequence can sensitively delineate the VRSs with ependymal openings.

Dorsal extensions of the fastigium cerebelli: an anatomical study using magnetic resonance imaging.

BACKGROUND AND PURPOSE: The fastigium cerebelli is an important topographical landmark for neurosurgeons and radiologists. However, few studies have characterized the morphology of the fastigium cerebelli. We aimed to investigate the fastigium cerebelli using postmortem specimens and magnetic resonance imaging (MRI) in vivo. MATERIALS AND METHODS: Three cadaveric brains were midsagittally sectioned for observing the fastigium cerebelli. Additionally, 66 outpatients underwent MRI, including sagittal T1-weighted imaging, axial T2-weighted imaging, and coronal constructive interference in steady-state (CISS) sequence. RESULTS: In the cadaveric specimens, the fastigium cerebelli was observed as a beak-like dorsal protrusion of the fourth ventricle. Its inner surface was observed as a small fovea. On serial CISS images, the fastigium cerebelli consistently possessed a pair of triangular-shaped, dorsal extensions lying parasagittally along the nodule. These extensions were classified as symmetrical, right-side dominant, or left-side dominant. The symmetrical type was the most predominant and comprised 60.6% of the extensions, while the right-side dominant and left-side dominant types comprised 13.6 and 25.8%, respectively. In 91% of the 66 patients, the number of slices covering the entirety of the dorsal extensions were the same on both sides. The fastigial angle (θ) formed by lines tangent to the superior and inferior medullary velums varied widely. CONCLUSIONS: The fastigium cerebelli has a pair of dorsal extensions lying parasagittally along the nodule. Coronal CISS sequence is useful in delineating the fastigium cerebelli in vivo.

Spinal Dural Arteriovenous Fistula Assumed to be Symptomatic after Placement of Lumbar Cerebrospinal Fluid Drain.

A 69-year-old man presented with severe headache. Cranial computed tomography revealed diffuse subarachnoid hemorrhage. An anterior communicating artery aneurysm was identified and successfully obliterated by open microsurgery on the same day. Following placement of a continuous lumbar cerebrospinal fluid drain on hospitalization day 7, the patient developed a severe paraplegia and sensory loss below T6. Cerebral magnetic resonance imaging did not identify a responsible lesion. Spinal magnetic resonance imaging, however, showed extensive intramedullary hyperintensity on T2-weighted sequences. Spinal angiography identified a dural arteriovenous fistula fed by the segmental artery branching with the 12th intercostal artery. It was successfully embolized and the patient's sensorimotor disturbances remarkably improved. A spinal dural arteriovenous fistula may better be considered as one of the underlying etiologies when patients exhibit new neurological deficits after placement of a continuous lumbar cerebrospinal fluid drain.