Review
Neuroradiology/Head and Neck Imaging
December 4, 2018

The Lateral C1–C2 Puncture: Indications, Technique, and Potential Complications

Abstract

OBJECTIVE. Lateral C1–C2 puncture can be used for CSF collection, contrast agent injection for myelography, and access for cordotomy. The objective of this article is to describe the indications, technique, and potential complications of this procedure.
CONCLUSION. Radiologists performing lumbar puncture or myelography should be comfortable gaining access to the subarachnoid space via the lateral C1–C2 approach when indicated. Familiarity with the technique and its potential complications is essential for a safe and efficient procedure.
A 2009 survey showed that over 85% of neuroradiology departments in the United States performed at least one lateral C1–C2 puncture for myelography in the year preceding the survey and that 93% would perform the procedure for thoracolumbar pathologic abnormality if MRI was not available or contraindicated and lumbar puncture was contraindicated [1]. Almost 80% of departments favor a lumbar approach to cervical myelography; however, 92% reported that they would perform a lateral C1–C2 puncture if lumbar access was unsuccessful. Over 60% also reported performing lateral C1–C2 puncture for obtaining CSF within the year preceding the survey [1].
Although it is infrequently performed, the lateral C1–C2 puncture plays a valuable role in the diagnostic evaluation for a subset of patients [2]. The procedure comes with risks but can be performed safely with proper technique. In this article, we will review the technique for lateral C1–C2 puncture with an emphasis on safety and potential complications. We will also review normal and variant arterial anatomy as it pertains to safe performance of the procedure.

Historical Perspective

Cisternal puncture for acquiring CSF was described by Obregia in 1908 and by Ayer in 1919 [35]. The procedure was performed from a posterior suboccipital approach with the patient in the lateral decubitus position or sitting upright with the head flexed. The needle was advanced freehand in the midline just inferior to the occipital protuberance until CSF was obtained [4]. Though the procedure was safe in experienced hands, complications and the increased use of both gas and positive contrast myelography prompted the need for a new approach to the subarachnoid space [610].
In the early 1960s, Mullan et al. [11] and Rosomoff et al. [12] independently described lateral C1–C2 puncture for percutaneous cordotomy with advancement of a needle under fluoroscopic guidance through the anterior subarachnoid space and into the anterolateral spinal cord. This procedure is still performed for patients with intractable pain [13]. The first description of lateral C1–C2 puncture for positive contrast myelography in 1968 by neurosurgeons Kelly and Alexander [14] described a technique identical to those of Mullan et al. and Rosomoff et al. for entering the anterior subarachnoid space. Use of the lateral C1–C2 puncture for gas myelography was described by neuroradiologists in 1972 [10, 15]. This report, the first description of lateral C1–C2 puncture by radiologists, described targeting the lateral part of the spinal canal, where the subarachnoid space widens slightly, rather than the smaller anterior portion. Targeting of the posterior part of the spinal canal was described in the late 1970s as a way to avoid inadvertent arterial puncture or puncture of the spinal cord [16, 17].
Initial advantages of lateral C1–C2 puncture for cervical myelography were described, including better quality images [18, 19] and decreased short-term adverse effects thought to be due to decreased intracranial spillage of contrast agent [20, 21]. However, reports of complications [22, 23], the routine use of postmyelography CT [24], and the increased availability of MRI have decreased the number of lateral C1–C2 punctures currently performed. Some authors, however, believe that its risks are overestimated and that lateral C1–C2 puncture is indicated and preferred in a select group of patients [23, 25, 26].

Why C1–C2?

In most patients, the dorsal subarachnoid space widens at C1–C2 providing a target for access (Fig. 1). The cervical spinal cord expands inferior to C2, decreasing the ratio of cervical spinal canal to cervical spinal cord area and making this region suboptimal for obtaining access [27]. The thoracic spinal canal is narrow, and a lateral approach is precluded by the presence of the ribs. Although a dorsal approach in the thoracic spine can be performed safely [28], it is generally avoided because the needle trajectory is directed toward the spinal cord itself.
Fig. 1 —42-year-old woman with neck pain. Sagittal T2-weighted MR image of cervical spine shows normal widening of spinal canal and dorsal subarachnoid space at C1–C2 (arrow).

Indications

Lateral C1–C2 puncture is often performed for either CSF collection or myelography (Table 1). Reasons for CSF collection include suspected meningitis, demyelination, or leptomeningeal tumor dissemination. In cases of suspected leptomeningeal disease, collecting CSF from nearer to the area of clinically or radiographically suspected disease can provide a higher yield of tumor cells [29]. Recently, data from one center showed that lateral C1–C2 puncture findings were positive in five of 37 patients with suspected intracranial or cervical leptomeningeal disease and negative lumbar puncture findings [30]. However, it is unclear how many lumbar punctures were attempted before lateral C1–C2 puncture in this cohort. The sensitivity of lumbar puncture for leptomeningeal disease is about 45–55% after one puncture and 80–90% after two punctures [31, 32]. Many researchers advocate for three lumbar punctures with negative findings before performing a lateral C1–C2 puncture for this indication.
TABLE 1: Indications for Lateral C1–C2 Puncture
IndicationComments
CSF collectionCannot obtain safe lumbar access; CSF must be sampled above a spinal block or there is a possibility that a block is complete; lumbar puncture findings are negative for suspected intracranial or cervical leptomeningeal disease
MyelographyCannot obtain safe lumbar access; must delineate superior level of spinal block or there is a possibility that a block is complete
Reasons for unsuccessful or unsafe lumbar punctureSevere lumbar stenosis; severe degenerative or postsurgical changes; infection in lumbar region; congenital anomaly such as low conus or tethered cord; history of arachnoiditis with adhesions; inability to assume prone or lateral decubitus position
Myelography is often performed in patients who are unable to undergo an MRI or after MRI evaluation is inconclusive or suboptimal. Although lateral C1–C2 puncture was previously preferred for cervical myelography, most radiologists now prefer a lumbar approach [21, 33]. Lateral C1–C2 puncture is considered when lumbar access is unsafe or unavailable or was previously unsuccessful or if the superior level of a spinal block must be delineated [2] (Fig. 2). Lateral C1–C2 puncture is also performed in cases of suspected complete subarachnoid block to avoid spinal coning [34, 35].
Fig. 2A —16-year-old girl with achondroplasia and known severe lumbar stenosis who developed progressive leg weakness after lumbar spinal anesthesia. Patient could not undergo MRI because of extensive external fixation hardware from recent tibial osteotomy. Myelography was performed via lateral C1–C2 puncture. Though C1–C2 puncture is usually not recommended for patients with achondroplasia because of upper cervical spinal canal stenosis and low-lying tonsils, decision was made to do C1–C2 puncture rather than lumbar puncture because of concern for hematoma at site of recent lumbar spinal anesthesia.
A, Contrast agent was injected into posterior subarachnoid space at C1–C2. Notice contrast agent layers ventrally (arrow); patient was positioned prone for procedure.
Fig. 2B —16-year-old girl with achondroplasia and known severe lumbar stenosis who developed progressive leg weakness after lumbar spinal anesthesia. Patient could not undergo MRI because of extensive external fixation hardware from recent tibial osteotomy. Myelography was performed via lateral C1–C2 puncture. Though C1–C2 puncture is usually not recommended for patients with achondroplasia because of upper cervical spinal canal stenosis and low-lying tonsils, decision was made to do C1–C2 puncture rather than lumbar puncture because of concern for hematoma at site of recent lumbar spinal anesthesia.
B, Axial (B) and sagittal (C) spot fluoroscopic images show complete myelographic block at L1 (arrows). Patient underwent posterior decompression shortly after myelogram was performed, with resolution of symptoms.
Fig. 2C —16-year-old girl with achondroplasia and known severe lumbar stenosis who developed progressive leg weakness after lumbar spinal anesthesia. Patient could not undergo MRI because of extensive external fixation hardware from recent tibial osteotomy. Myelography was performed via lateral C1–C2 puncture. Though C1–C2 puncture is usually not recommended for patients with achondroplasia because of upper cervical spinal canal stenosis and low-lying tonsils, decision was made to do C1–C2 puncture rather than lumbar puncture because of concern for hematoma at site of recent lumbar spinal anesthesia.
C, Axial (B) and sagittal (C) spot fluoroscopic images show complete myelographic block at L1 (arrows). Patient underwent posterior decompression shortly after myelogram was performed, with resolution of symptoms.

Contraindications

Absolute contraindications to lateral C1–C2 puncture include Chiari malformation, known mass at C1–C2 with mass effect on the thecal sac, cervical stenosis at C1–C2 (Fig. 3), evidence of herniation, uncorrectable coagulopathy leading to an increased risk of bleeding, known vertebral or posterior inferior cerebellar artery variant with vessel crossing the posterior spinal canal at C1–C2, and obstructive hydrocephalus. In obstructive hydrocephalus or herniation, lateral C1–C2 puncture can cause shifting of intracranial components resulting from the pressure differential above and below the block or above and below the tentorium cerebelli [36]. Relative contraindications to the procedure include an uncooperative patient, who may require sedation or general anesthesia, and low-lying cerebellar tonsils. Lowlying cerebellar tonsils increase the risk of tonsillar puncture and may cause altered CSF flow around the foramen magnum [37]. Cases of uncooperative patients and low-lying cerebellar tonsils should be managed on a case-by-case basis.
Fig. 3 —82-year-old man with neck stiffness. Sagittal T2-weighted MR image of upper cervical spine shows severe stenosis at C1–C2 secondary to large retrodental pannus (white arrows) and ligamentum flavum infolding (black arrow). Notice that there is no safe window for puncture in posterior one-third of spinal canal at C1–C2.

Preprocedure Evaluation

Once the procedure is deemed indicated, the radiologist begins reviewing the prior imaging and medical record. Head imaging should be performed before the procedure in all cases. If there is a prior MRI or CT angiogram, the vertebral and posterior inferior cerebellar arteries should be identified to ensure that there is no variant anatomy or vessel crossing the expected puncture location. Cervical spine imaging should be reviewed in patients with prior surgery to ensure a safe window for access. Uncommon factors that can increase bleeding risk include collateral vessels secondary to prior jugular venous thrombosis and prominent vessels in dural arteriovenous fistula. In such cases, CT angiography or MR angiography of the neck should be performed before deciding whether the procedure is safe to perform.
A review of the medical record focuses on current medications and history of contrast agent allergy. Patients with a history of contrast agent allergy are premedicated with steroids before myelography. Anticoagulation and antiplatelet medications are withheld according to established guidelines [38, 39] (Table 2). Coagulation tests should be available within 1 week of the procedure. Patients with coagulopathy are at increased risk for spinal hematoma, which may require emergent surgery [4042]. Many departmental guidelines require a platelet count of at least 50 × 109/L and an international normalized ratio of 1.4 or less, and the procedure should not be considered for patients with abnormal coagulation test results [39].
TABLE 2: Recommended Guidelines for Performing Spinal Procedures in Anticoagulated Patients
WarfarinDiscontinue chronic warfarin therapy 4–5 days before spinal procedure and evaluate INR. INR should be within the normal range at time of procedure to ensure adequate levels of all vitamin K-dependent factors.
Antiplatelet medicationNo contraindications with aspirin or NSAIDs. Thienopyridine derivatives (clopidogrel and ticlopidine) should be discontinued 7 days and 14 days, respectively, prior to procedure. GP IIb/IIIa inhibitors should be discontinued to allow recovery of platelet function prior to procedure (8 hours for tirofiban and eptifibatide, 24–48 hours for abciximab).
Thrombolytics/fibrinolyticsThere are no available data to suggest a safe interval between procedure and initiation or discontinuation of these medications. Follow fibrinogen level and observe for signs of neural compression.
LMWHDelay procedure at least 12 hours from the last dose of thromboprophylaxis LMWH dose. For “treatment” dosing of LMWH, at least 24 hours should elapse prior to procedure. LMWH should not be administered within 24 hours after the procedure.
Unfractionated SQ heparinThere are no contraindications to neuraxial procedure if total daily dose is less than 10,000 units. For higher dosing regimens, manage according to intravenous heparin guidelines.
Unfractionated IV heparinDelay spinal puncture 2–4 hours after last dose, document normal aPTT. Heparin may be restarted 1 hour following procedure.

Note—Reprinted with permission from [39]. INR = international normalized ratio, NSAID = nonsteroidal antiinflammatory drug, GP IIb/IIIa = platelet glycoprotein receptor IIb/IIIa inhibitors, LMWH = low-molecular-weight heparin, aPTT = activated partial thromboplastin time, SQ = subcutaneous.

Technique

Patient Positioning and Localization

The procedure can be performed with the patient positioned prone, supine, or lateral decubitus. Ideally, the patient's neck is placed in a neutral position or slight hyperextension because extension increases the width of the dorsal subarachnoid space at C1–C2 [43, 44]. For CSF collection, either the supine or prone position can be used. Neither position provides a specific advantage from a technical standpoint; the supine position tends to be more comfortable for most patients. For cases of myelography, the prone extended position is preferred to prevent intracranial spill-age of contrast agent and allow better control of the contrast agent column [23, 4446]. However, the prone extended position may be uncomfortable for patients and hyperex-tension can lead to patient injury [22, 44]. The supine position can be used for myelography with the neck maintained in a neutral position to prevent the intracranial spillage that occurs with the supine extended position [46]. In all cases, the lateral decubitus position is the least advantageous and should be used only if the prone and supine positions are not possible. Optimum positioning should be determined by patient comfort, because it is essential that patients do not move during the procedure. This is especially important in patients with meningeal irritation due to meningitis or leptomeningeal disease because they often present with a stiff neck and cannot maintain certain positions [47]. Patients with cervical spondylosis also may be unable to maintain neck extension as a result of cervical canal stenosis [48, 49].
After the patient is positioned, the head can be secured with a folded towel placed over the patient's forehead and tape, if supine, or by towels or a specialized chin and neck holder, if prone, to prevent head turning. The puncture site is marked either with a radiopaque object under fluoroscopic guidance (Fig. 4) or with a grid placed over the patient's neck for CT. Under CT guidance, the vertebral artery should be followed as it exits the C2 transverse foramen before planning the needle trajectory (Fig. 5). The puncture site in most patients is about 1 cm inferior and 1 cm posterior to the mastoid process. Using fluoroscopy, the puncture site is about 2–5 mm anterior to the spinolaminar line, posterior to the recently described C1 posterior arch flare point [50] and about 5 mm inferior to the posterior arch of C1 (Fig. 6). Before marking the puncture site, care should be taken to ensure that the image is a true lateral projection (Fig. 6).
Fig. 4A —32-year-old man with lymphoma and visual disturbances undergoing lateral C1–C2 puncture for suspected leptomeningeal disease. Multiple lumbar puncture findings had previously been negative.
A, Lateral fluoroscopic image shows Kelly clamp placed over posterior spinal canal at C1–C2 at intended puncture site (arrow). Note that tip of Kelly clamp is anterior to spinolaminar line (dashed line) at anterior border of posterior one-third of spinal canal, which is most anterior location that is acceptable for safe puncture.
Fig. 4B —32-year-old man with lymphoma and visual disturbances undergoing lateral C1–C2 puncture for suspected leptomeningeal disease. Multiple lumbar puncture findings had previously been negative.
B, Photographs show how patient's neck was marked (B) and how patient was prepared and draped (C).
Fig. 4C —32-year-old man with lymphoma and visual disturbances undergoing lateral C1–C2 puncture for suspected leptomeningeal disease. Multiple lumbar puncture findings had previously been negative.
C, Photographs show how patient's neck was marked (B) and how patient was prepared and draped (C).
Fig. 5A —54-year-old woman with breast cancer undergoing CT-guided C1–C2 puncture for CSF collection for suspected leptomeningeal disease because of pachymeningeal disease seen at prior brain MRI. Previous lumbar puncture was unsuccessful because of extensive thoracosacral fusion.
A, Axial CT of head in soft-tissue window shows left vertebral artery within transverse foramen of C2 (arrow).
Fig. 5B —54-year-old woman with breast cancer undergoing CT-guided C1–C2 puncture for CSF collection for suspected leptomeningeal disease because of pachymeningeal disease seen at prior brain MRI. Previous lumbar puncture was unsuccessful because of extensive thoracosacral fusion.
B, Sequential CT image obtained 2.5 mm superior to that in A shows left vertebral artery exiting transverse foramen of C2 (white arrow). Superior portion of posterior arch of C2 is blocking access to spinal canal at this level (black arrow).
Fig. 5C —54-year-old woman with breast cancer undergoing CT-guided C1–C2 puncture for CSF collection for suspected leptomeningeal disease because of pachymeningeal disease seen at prior brain MRI. Previous lumbar puncture was unsuccessful because of extensive thoracosacral fusion.
C, CT image obtained 2.5 mm superior to image in B shows that left vertebral artery has fully exited transverse foramen of C2 and now travels alongside base of C2 vertebral body (arrow), well anterior to targeted needle trajectory (dashed line).
Fig. 6A —Target site localization in cadaver, fluoroscopic anatomy, and appropriate needle positioning.
A, Photograph of cadaver dissection performed in our anatomy laboratory at Weill Cornell Medical Center shows V3 segment of vertebral artery (red arrows) and ideal needle target (box) between posterior arch of C1 (black arrowhead) and posterior arch of C2 (white arrowhead). Needle target is just anterior to spinolaminar line (dashed line) and inferior and posterior to mastoid process (white arrow).
Fig. 6B —Target site localization in cadaver, fluoroscopic anatomy, and appropriate needle positioning.
B, 39-year-old man with neck pain. Lateral cervical spine radiograph shows ideal puncture site target location (box) just anterior to spinolaminar line (dashed white line). Notice alignment of inferior endplate of C2 and superior and inferior endplates of C3 (dashed black lines) as well as superimposed bilateral mastoid processes (arrow) and posterior C2 and C3 vertebral bodies (arrowheads) signifying true lateral radiograph.
Fig. 6C —Target site localization in cadaver, fluoroscopic anatomy, and appropriate needle positioning.
C, 66-year-old man with cryptococcal meningitis and history of arachnoiditis. Fluoroscopic image shows findings characteristic of true lateral image, including superimposed mastoid processes (black arrow) and sharp endplates (dashed black lines) and posterior vertebral bodies (white arrowheads) at C2 and C3. Needle is angled anteriorly (white arrows) though needle tip remains posterior to C1 posterior arch flare point (black arrowhead) within posterior one-third of spinal canal. Notice that needle is just anterior to spinolaminar line (dashed white line).
Fig. 6D —Target site localization in cadaver, fluoroscopic anatomy, and appropriate needle positioning.
D, 74-year-old woman with bilateral lower extremity weakness and previously unsuccessful lumbar puncture due to extensive postsurgical changes. Lateral fluoroscopic image shows that needle is seen down barrel and is not directed anteriorly or posteriorly. Needle tip (white arrow) is just anterior to spinolaminar line (dashed line) and posterior to C1 posterior arch flare point (black arrow).

Needle Selection and Advancement

After marking and preparing the patient using standard sterile technique, the skin is anesthetized using a 25-gauge needle. Deeper anesthetic can be obtained through a 23-gauge 1.5-inch needle or through the spinal needle; however, care should be taken to aspirate before anesthetic injection to ensure that the needle is not intravascular or intrathecal. Also, if the spinal needle is used, care should be taken to make sure that the stylet is reinserted securely before thecal sac puncture. Fluoroscopic or CT images with the anesthetic needle in position are obtained to determine adjustments that may need to be made to the puncture site. Many operators prefer a 20- or 22-gauge 6- or 9-cm spinal needle [46]. The benefits of a larger gauge needle include better CSF return, easier needle steering, and less bending during dural puncture. Some operators, however, prefer a smaller gauge needle because of the theoretic risk of decreased damage to the spinal cord if it is directly punctured or decreased bleeding risk if a vessel is entered. The drawbacks of a smaller needle are that it is more prone to bending, especially when entering the tough dura, and may make ensuring complete dural puncture difficult because of less rapid flow of CSF return. Larger needle gauge increases the frequency of postdural puncture headache after lumbar puncture [51, 52]; however, postdural puncture headache after cervical puncture is uncommon and increased needle gauge has not been shown to correlate with increased frequency of headache after cervical punctures [53].
Once a needle is selected, it is advanced under intermittent fluoroscopic guidance with the bevel facing dorsally [26, 46]. Bevel orientation is important because the dural sac should be punctured with the needle parallel to the elastic fibers, allowing fiber retraction, which minimizes the size of the resulting defect [54, 55]. Dorsal orientation of the bevel optimizes needle entry into the dural sac and prevents the needle from slipping off and tracking posteriorly. After the needle is advanced a distance in the correct trajectory, an anteroposterior image is obtained to check needle position. When the needle is within a few millimeters of the medial border of the ipsilateral lateral mass of C1, the stylet is removed to check for CSF return (Fig. 7A). Dural tenting is expected, and CSF return may not happen until the needle is past the midline [46, 56] (Fig. 7B). It is common to encounter venous blood as the needle enters the epidural venous plexus. If this happens, advancing the needle another 1–2 mm usually yields CSF. Under CT, the needle is advanced, with intermittent scanning, to enter the posterior one-third of the spinal canal (Fig. 7C).
Fig. 7A —Needle placement at time of CSF return.
A, 32-year-old man with lymphoma (same patient as in Fig. 4). Anteroposterior fluoroscopic image shows needle tip (white arrow) within few millimeters of medial border of lateral mass of C1 (black arrow). CSF was obtained before needle reached midline.
Fig. 7B —Needle placement at time of CSF return.
B, 66-year-old man with suspected meningitis. Anteroposterior fluoroscopic image shows needle tip (white arrow) past midline and almost at medial border of opposite lateral mass (black arrow) before CSF return. Dural tenting is to be expected, and at times needle must be advanced past midline before CSF return.
Fig. 7C —Needle placement at time of CSF return.
C, 54-year-old woman with breast cancer (same patient as in Fig. 5). Axial CT shows needle tip (white arrow) in position proximal to midline at time of CSF return. Notice that needle is well posterior to vertebral artery (black arrow) and needle tip is in posterior one-third of spinal canal.

CSF Collection and Contrast Agent Injection

Once the dura is punctured and CSF return verified, the bevel of the needle is rotated either 90° so the bevel faces toward the patient's feet or 180° so it faces ventrally to optimize CSF flow. If CSF is in the needle hub though not freely flowing, the stylet should be reinserted and the needle should be advanced a few millimeters to ensure complete dural puncture. The needle should then be gently retracted to ensure that the needle is not contacting the opposite side of the spinal canal or the spinal cord. In general, manual aspiration is not recommended because it can cause nerve root or small vessel damage and does not resolve the underlying problem of improper needle placement. If the purpose of the procedure is CSF collection, the appropriate amount of CSF is collected, the stylet is returned to the needle hub, and the needle is removed. The puncture site is cleaned and a bandage is applied. If the procedure is being performed for myelography, contrast agent is injected under fluoroscopic guidance to ensure layering in the dependent subarachnoid space (Figs. 2 and 8). The contrast agent should move away from the needle tip and extend cranially and caudally [57]. As contrast agent is injected, the head of the fluoroscopic table should be elevated to decrease the intracranial bolus of contrast agent. When using CT, a small test dose of contrast agent is injected and the patient is scanned to ensure that the contrast agent forms layers within the dependent subarachnoid space. If at any point the patient complains of severe pain during contrast agent injection or exhibits the Lhermitte sign, or if there is arterial blood within the needle hub, the procedure is terminated and emergent CT is performed. Similarly, CT is also performed if there is concern for intramedullary injection (Fig. 8). After injection of the recommended contrast agent volume, the stylet is reinserted and the needle is removed. The puncture site is then cleaned and a bandage is applied. The recommended doses for myelography via C1–C2 puncture are 7–12.5 mL for iohexol 180 mg I/mL, 6–12.5 mL for iohexol 240 mg I/mL, and 4–10 mL for iohexol 300 mg I/mL although higher doses rarely cause adverse reactions. At our institutions, we use iohexol 240 mg I/mL for cervical myelography performed via lateral C1–C2 puncture and iohexol 300 mg I/mL for total spine myelography. The use of single-dose myelographic contrast vials is recommended, and it must be stressed that only nonionic contrast agent should be used for myelography because older ionic contrast agents have significant neurotoxicity [58].
Fig. 8A —Contrast agent injection during myelography via C1–C2 puncture.
A, 74-year-old woman with bilateral lower extremity weakness (same patient as in Fig. 6D). Lateral fluoroscopic image (A) shows successful injection of contrast agent into subarachnoid space after lateral C1–C2 puncture (black arrow). Needle has been removed. Patient was positioned supine for procedure with neck slightly hyperextended. In supine position, it is difficult to avoid some intracranial spillage of contrast agent (white arrow). Corresponding image from CT myelogram (B) verifies contrast agent in subarachnoid space (white arrow) without subdural or epidural contamination. Image also shows intracranial contrast bathing cerebellum (black arrow).
Fig. 8B —Contrast agent injection during myelography via C1–C2 puncture.
B, 74-year-old woman with bilateral lower extremity weakness (same patient as in Fig. 6D). Lateral fluoroscopic image (A) shows successful injection of contrast agent into subarachnoid space after lateral C1–C2 puncture (black arrow). Needle has been removed. Patient was positioned supine for procedure with neck slightly hyperextended. In supine position, it is difficult to avoid some intracranial spillage of contrast agent (white arrow). Corresponding image from CT myelogram (B) verifies contrast agent in subarachnoid space (white arrow) without subdural or epidural contamination. Image also shows intracranial contrast bathing cerebellum (black arrow).
Fig. 8C —Contrast agent injection during myelography via C1–C2 puncture.
C, Axial (C) and sagittal (D) CT images show intramedullary contrast agent injection during attempted C1–C2 puncture (black arrows). Notice that there is contrast agent within subarachnoid space (white arrows) because lumbar puncture through recent surgical site was performed after unsuccessful C1–C2 puncture.
Fig. 8D —Contrast agent injection during myelography via C1–C2 puncture.
D, Axial (C) and sagittal (D) CT images show intramedullary contrast agent injection during attempted C1–C2 puncture (black arrows). Notice that there is contrast agent within subarachnoid space (white arrows) because lumbar puncture through recent surgical site was performed after unsuccessful C1–C2 puncture.

Postprocedure Care

The patient is observed for 2–4 hours in the recovery area. Bed rest is not required after the procedure; however, the patient is advised to avoid strenuous activity for 48–72 hours [59]. Semierect positioning is stressed while the patient is in bed to drop contrast agent into the lower thecal sac and decrease the volume of intracranial spillage [60]. The patient should be in the company of a responsible adult for 12 hours after the procedure, and staff should be available to answer questions as they arise.

Complications

Serious complications after C1–C2 puncture are rare [19, 22]. A large survey by Robertson and Smith [22] revealed major complications in less than 0.05% of cervical myelograms performed via lateral C1–C2 puncture, with the most common major complications associated with cervical spine hyperextension during positioning. Minor complications after C1–C2 puncture include headache, nausea, and vomiting. The frequency of headache after C1–C2 puncture is lower than that after lumbar puncture, and, in most cases, the headaches are mild and less than 24 hours in duration [19, 20]. Eight of 94 patients in a 1985 study developed headache after C1–C2 myelography with iohexol, though only one headache was severe and lasted more than 24 hours [19]. Other studies with small sample sizes have shown a high frequency of headache, though it is consistently shown that the headaches are mild and self-limited in most cases [21, 45, 53]. Nausea and vomiting appear less commonly with iohexol than with metrizamide because of the better safety profile of iohexol [19, 21, 45, 61, 62]. The frequency of nausea is less than 5% in most series [19, 53]. Seizure and adverse neurobehavioral reactions, which were a real concern with metrizamide, have rarely been described after administration of iohexol [63, 64]. Because of its high frequency of associated complications, metrizamide should no longer be used [65]. The frequency of post-dural puncture headache after C1–C2 puncture is very low, probably as a result of less hydrostatic pressure of CSF above the puncture site in comparison with a lumbar puncture [53]. One large series mentions a CSF leak after C1–C2 puncture, though this did not require further intervention [66].

Bleeding

There are case reports of bleeding complications after lateral C1–C2 puncture, though bleeding occurs infrequently [23, 41, 42, 67, 68]. In the large survey by Robertson and Smith [22], three cases of arterial injury, including one subsequent death and one epidural hematoma, were reported in an estimated total of over 55,419 cervical myelograms performed by lateral C1–C2 puncture. Other large series describe no bleeding or vascular complications [66, 69]. The risk of bleeding after lumbar puncture is also very low, with most reported cases occurring in patients receiving anticoagulation therapy or those with coagulopathy [7072]. Iatrogenic hematoma in patients not previously receiving anticoagulation therapy or with coagulopathy has, however, been described [40]. Unfortunately, a 1983 case report described death after a lateral C1–C2 puncture due to puncture of a variant vertebral artery [68], and bleeding is a major concern for those performing the procedure.

Normal and Variant Arterial Anatomy

Variant vertebral artery anatomy is common and can occur anywhere along the vessel's course [7377]. Normally, the extra-spinal V3 segment exits the C2 transverse foramen, ascends through the C1 transverse foramen, and travels posteromedially around the atlantooccipital junction within a groove on the superior surface of the posterior arch of C1. It then turns anterosuperiorly before piercing the dura at the foramen magnum [78]. The V3 segment often forms a posterior bend, which can overlie the spinal canal between C2 and C1 (Fig. 9). A 1990 study by Katoh [23] looked at 164 vertebral artery angiograms and showed that the posterior bend is anterior to the spinal canal or overlies the anterior one-third of the spinal canal in 96% of patients, overlies the middle one-third of the spinal canal in 2% of patients, and over-lies the posterior one-third of the spinal canal in 2% of patients.
Fig. 9A —Anatomy of V3 segment of vertebral artery.
A, Lateral photograph from cadaver dissection performed in our anatomy laboratory at Weill Cornell Medical Center shows V3 segment of left vertebral artery. Notice posterior bend of V3 segment (arrowhead). Posterior bend of V3 is anterior to spinal canal (arrows) or overlies anterior one-third of spinal canal in 96% of patients.
Fig. 9B —Anatomy of V3 segment of vertebral artery.
B, 8-year-old boy with multiple congenital abnormalities. Reformatted 3D image from CT angiography of neck shows variant left vertebral artery with fenestration above and below C1. Vertebral artery is normal as it passes distal to transverse foramen of C2 (red arrow). It then divides into branch entering spinal canal between C2 and C1 (white arrows) and branch that travels normally through transverse foramen of C1 (arrowhead). These branches join together before combining with opposite vertebral artery to form basilar artery (not shown).
Vertebral artery embryology involves complex interplay among the seven cervical intersegmental arteries and developing lateral and posterior spinal arteries [77, 79]. Persistence of the first intersegmental artery, which normally regresses, causes the distal vertebral artery to enter the spinal canal between C2 and C1 rather than entering the transverse foramen of C1. This has also been called a C2 segmental type vertebral artery and has been implicated in cases of C2 sub-occipital neuralgia and myelopathy [8083]. A recent study assessing upper cervical vertebral artery anomalies in healthy subjects with MR angiography found this anomaly to be present in 3.2% of Japanese patients [74], which is more common than previously thought [84]. First intersegmental artery in combination with preservation of a distal vertebral artery that enters the C1 transverse foramen is called fenestration of the vertebral artery above and below C1, or a duplicated vertebral artery. This has been well-described, often as an incidental angiographic finding in patients with other intracranial pathologic abnormalities [85, 86] (Fig. 9).
Posterior inferior cerebellar artery (PICA) is most commonly an intracranial branch off the distal V4 segment, originating about 15 mm proximal to the vertebrobasilar junction and traveling posteriorly along the inferior cerebellum [77, 87]. PICA has a variable origin and location of its most caudal loop [74, 75, 84, 87]. A 2009 angiographic study showed the caudal loop extending below the inferior border of the posterior C1 arch in two of 346 patients (0.6%) but did not describe PICA originating below C1 [87] (Fig. 10). Studies using MR angiography and CT angiography both showed the frequency of PICA origin from between C1 and C2 to be around 1% in Japanese patients [74, 75].
Fig. 10A —80-year-old woman with bilateral strokes who had variant posterior inferior cerebellar artery (PICA) anatomy.
A, Coronal (A) and sagittal (B) maximum-intensity-projection images from CT angiogram of neck show caudal loop of PICA descending below C1 and into spinal canal at C1–C2 (arrows). Lateral C1–C2 puncture should be avoided in patients with this incidental anatomic variant.
Fig. 10B —80-year-old woman with bilateral strokes who had variant posterior inferior cerebellar artery (PICA) anatomy.
B, Coronal (A) and sagittal (B) maximum-intensity-projection images from CT angiogram of neck show caudal loop of PICA descending below C1 and into spinal canal at C1–C2 (arrows). Lateral C1–C2 puncture should be avoided in patients with this incidental anatomic variant.
Recent studies have shown the combined frequency of first intersegmental artery, fenestration of the vertebral artery above and below C1, and origin of PICA below C1 to be about 5% in Japanese patients with normal cervical spine anatomy [74, 75]. The frequency is higher in patients with atlantoaxial subluxation and congenital cervical spine anomalies [84, 88]. Awareness of these anomalies is imperative before lateral C1–C2 puncture because laceration of an anomalous vessel is a rare but potentially fatal complication [22, 68]. Although the reported frequency of these vascular anomalies is high, the frequency of vessels encroaching the posterior one-third of the spinal canal is significantly lower, emphasizing the need for proper technique [84, 89]. In patients who are unable to undergo MRI, the decision to pursue limited preprocedure CT angiography to delineate the vascular anatomy is at the discretion of the radiologist performing the procedure. We do not routinely perform preprocedure vascular imaging, though we believe that further research into the true frequency of these vascular variants in non-Japanese patients is needed.

Spinal Cord Puncture and Intramedullary Injection

In the large survey by Robertson and Smith [22], five cases of spinal cord puncture and 16 cases of intramedullary contrast agent injection were reported. The five spinal cord punctures resulted in one death and one patient with a persistent neurologic deficit, whereas three patients recovered completely. It is likely that many cases of spinal cord puncture go unreported because, although it is painful, it is unclear whether puncture itself routinely causes symptoms after the procedure [15]. Of the 16 cases of intramedullary contrast agent injection, eight patients recovered completely and eight patients had a persistent neurologic deficit. Intramedullary contrast agent injection can cause severe complications, which increase in severity with a greater volume of injected contrast agent [90]. In 1988, Nakstad and Kjartansson [91] described an injection of 8 mL of iohexol with about 1–2 mL thought to be intramedullary and no complaints of symptoms or long-lasting effects. Experimental data have shown that the spinal cord is able to accommodate less than 1.0 mL of contrast agent without producing a broad contrast agent stripe [57]. Thus, small injections of intramedullary contrast agent may be of little clinical significance, and early recognition of possible intramedullary injection is essential to avoid potentially devastating complications [57, 92]. Contrast agent neurotoxicity, which was a major concern with metrizamide and led to severe deficits with small injections, does not appear to be as significant with iohexol [19, 22, 23, 33, 9194]. In most cases, the patient will complain of pain at the time of intramedullary injection and neurologic complications will be immediately apparent [90]. CT should be performed if there is uncertainty as to the location of injected contrast agent, and symptomatic intramedullary injections should be treated with steroids after discussion with the ordering physician [90].

Conclusion

Lateral C1–C2 puncture can provide valuable diagnostic information in a subset of patients. Familiarity with the indications, technique, and potential complications can ensure that this procedure can be offered by radiology departments and performed safely when indicated. Further research is necessary to identify the frequency of relevant vascular variants in non-Japanese patient cohorts and to better define the role of lateral C1–C2 puncture in cases of suspected leptomeningeal disease.

Acknowledgment

We thank Doug Noble for contributing to the outline of the manuscript and for sharing his personal experience in performing these procedures.

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Information & Authors

Information

Published In

American Journal of Roentgenology
Pages: 431 - 442
PubMed: 30512994

History

Submitted: January 16, 2018
Accepted: July 15, 2018
Version of record online: December 4, 2018

Keywords

  1. C1–2 puncture
  2. C1–C2 puncture
  3. cervical puncture
  4. CSF aspiration
  5. CT
  6. fluoroscopy
  7. myelography
  8. spine intervention

Authors

Affiliations

Steven P. Daniels
Department of Radiology, New York Presbyterian Hospital-Weill Cornell Medical Center, 525 E 68th St, Box 141, New York, NY 10065.
Andrew D. Schweitzer
Department of Radiology, New York Presbyterian Hospital-Weill Cornell Medical Center, 525 E 68th St, Box 141, New York, NY 10065.
Ritwik Baidya
Department of Anatomy in Radiology, Weill Cornell Medical College, New York, NY.
George Krol
Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, NY.
Robert Schneider
Department of Radiology and Imaging, Hospital for Special Surgery, New York, NY.
Eric Lis
Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, NY.
J. Levi Chazen
Department of Radiology, New York Presbyterian Hospital-Weill Cornell Medical Center, 525 E 68th St, Box 141, New York, NY 10065.

Notes

Address correspondence to S. P. Daniels ([email protected]).

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