DOI: 10.1148/rg.272065101
RadioGraphics 2007;27:371-390
© RSNA, 2007
Percutaneous Biopsy of Head and Neck Lesions with CT Guidance: Various Approaches and Relevant Anatomic and Technical Considerations1
Sanjay Gupta, MD,
Joy A. Henningsen, MD,
Michael J. Wallace, MD,
David C. Madoff, MD,
Frank A. Morello, Jr, MD,
Kamran Ahrar, MD,
Ravi Murthy, MD and
Marshall E. Hicks, MD
1 From the Department of Diagnostic Radiology, Unit 325, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030. Recipient of a Magna Cum Laude award for an education exhibit at the 2005 RSNA Annual Meeting. Received May 16, 2006; revision requested July 25 and received August 22; accepted August 23. R.M. is a research consultant for Sirtex Medical (Lake Forest, Ill); M.E.H. is a stockholder in Pfizer (New York, NY), General Electric (Fairfield, Conn), and St Jude Medical (St Paul, Minn); all other authors have no financial relationships to disclose.
Address correspondence to S.G. (e-mail: sgupta{at}di.mdacc.tmc.edu).
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Abstract
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Deep-seated head and neck lesions, which traditionally were evaluated by surgical means, are now accessible with less invasive computed tomography–guided percutaneous needle biopsy techniques. Major vessels, the trachea, and osseous structures like the maxilla, mandible, and vertebrae often preclude direct access to these lesions. It is important to understand the anatomy relevant to safe access route planning and the techniques, advantages, and limitations associated with various approaches used for percutaneous biopsy of head and neck lesions. For biopsy of suprahyoid head and neck lesions, including those of the skull base and upper cervical vertebrae, various approaches such as the subzygomatic, retromandibular, paramaxillary, submastoid, transoral, and posterior approaches can be used. Lesions in the infrahyoid portion of the neck and lower cervical vertebrae can be accessed with the anterolateral approach (between the airways and the carotid sheath), posterolateral approach (posterior to the carotid sheath), and direct posterior approach. The location and extent of the lesions and their relationship to adjacent structures influence the choice of the trajectory to use. Careful planning of the procedure and considerable familiarity with head and neck anatomy are necessary for a biopsy that is both precise and safe.
© RSNA, 2007
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Introduction
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Percutaneous needle biopsy with imaging guidance is a well-established technique for diagnosis of head and neck lesions (1–8). Computed tomography (CT)–guided biopsies of deep-seated head and neck lesions are challenging because major vessels, nerves, the airway, or osseous structures often intervene in the projected needle path. Therefore, a thorough knowledge of the complex cross-sectional anatomy of this region is essential for planning a safe route of access for a needle biopsy.
In this article, we review the various approaches used for CT-guided biopsies of head and neck lesions, focusing on the relevant anatomy, technical aspects, and advantages and limitations of each approach. Specific topics discussed are image guidance; patient preparation and lesion localization; biopsy technique and needle selection; complications; approaches for skull base, head, and suprahyoid neck lesions; and approaches for infrahyoid neck lesions.
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Anatomy
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For this review, we have divided the head and neck area into suprahyoid and infrahyoid regions because each region requires different percutaneous biopsy approaches (9,10). The axial cross-sectional anatomy extending from the skull base to the cervicothoracic junction is shown in schematic illustrations (Fig 1), which focus on the important osseous, muscular, vascular, and neural structures and the spaces at various levels. Each figure panel shows the anatomic structures on the left and the spaces on the right.
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Figure 1a. (a) Axial cross-sectional anatomy at the level of the skull base. Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. (b, c) Axial cross-sectional anatomy at the level of the upper maxillary antrum (b) and lower maxillary antrum (c). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (d, e) Axial cross-sectional anatomy at the level of the alveolar ridge (d) and mandible (e). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (f–h) Axial cross-sectional anatomy at the level of the C4 vertebra (f ), C6 vertebra (g), and C7 vertebra (h). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side.
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Figure 1b. (a) Axial cross-sectional anatomy at the level of the skull base. Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. (b, c) Axial cross-sectional anatomy at the level of the upper maxillary antrum (b) and lower maxillary antrum (c). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (d, e) Axial cross-sectional anatomy at the level of the alveolar ridge (d) and mandible (e). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (f–h) Axial cross-sectional anatomy at the level of the C4 vertebra (f ), C6 vertebra (g), and C7 vertebra (h). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side.
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Figure 1c. (a) Axial cross-sectional anatomy at the level of the skull base. Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. (b, c) Axial cross-sectional anatomy at the level of the upper maxillary antrum (b) and lower maxillary antrum (c). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (d, e) Axial cross-sectional anatomy at the level of the alveolar ridge (d) and mandible (e). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (f–h) Axial cross-sectional anatomy at the level of the C4 vertebra (f ), C6 vertebra (g), and C7 vertebra (h). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side.
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Figure 1d. (a) Axial cross-sectional anatomy at the level of the skull base. Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. (b, c) Axial cross-sectional anatomy at the level of the upper maxillary antrum (b) and lower maxillary antrum (c). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (d, e) Axial cross-sectional anatomy at the level of the alveolar ridge (d) and mandible (e). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (f–h) Axial cross-sectional anatomy at the level of the C4 vertebra (f ), C6 vertebra (g), and C7 vertebra (h). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side.
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Figure 1e. (a) Axial cross-sectional anatomy at the level of the skull base. Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. (b, c) Axial cross-sectional anatomy at the level of the upper maxillary antrum (b) and lower maxillary antrum (c). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (d, e) Axial cross-sectional anatomy at the level of the alveolar ridge (d) and mandible (e). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (f–h) Axial cross-sectional anatomy at the level of the C4 vertebra (f ), C6 vertebra (g), and C7 vertebra (h). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side.
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Figure 1f. (a) Axial cross-sectional anatomy at the level of the skull base. Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. (b, c) Axial cross-sectional anatomy at the level of the upper maxillary antrum (b) and lower maxillary antrum (c). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (d, e) Axial cross-sectional anatomy at the level of the alveolar ridge (d) and mandible (e). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (f–h) Axial cross-sectional anatomy at the level of the C4 vertebra (f ), C6 vertebra (g), and C7 vertebra (h). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side.
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Figure 1g. (a) Axial cross-sectional anatomy at the level of the skull base. Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. (b, c) Axial cross-sectional anatomy at the level of the upper maxillary antrum (b) and lower maxillary antrum (c). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (d, e) Axial cross-sectional anatomy at the level of the alveolar ridge (d) and mandible (e). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (f–h) Axial cross-sectional anatomy at the level of the C4 vertebra (f ), C6 vertebra (g), and C7 vertebra (h). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side.
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Figure 1h. (a) Axial cross-sectional anatomy at the level of the skull base. Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. (b, c) Axial cross-sectional anatomy at the level of the upper maxillary antrum (b) and lower maxillary antrum (c). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (d, e) Axial cross-sectional anatomy at the level of the alveolar ridge (d) and mandible (e). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side. CN = cranial nerve. (f–h) Axial cross-sectional anatomy at the level of the C4 vertebra (f ), C6 vertebra (g), and C7 vertebra (h). Anatomic structures are shown on the left side of the diagram; spaces are shown on the right side.
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The parapharyngeal space (Fig 1a–1e) is shaped like an upside-down pyramid, the inferior apex of which points toward the greater cornu of the hyoid and the superior base of which is demarcated by the skull base. It is bounded anteriorly by the masticator space, laterally by the deep parotid space, medially by the pharyngeal mucosal space, posteriorly by the carotid space, and posteromedially by the lateral extension of the retropharyngeal space. Apart from fat, the parapharyngeal space contains the internal maxillary, middle meningeal, and ascending pharyngeal arteries; the pterygoid venous plexus; and branches of the mandibular nerve. The pharyngeal mucosal space (Fig 1a–1e) is located on the airway side of the buccopharyngeal fascia in the nasopharynx and oropharynx and contains mucosa, lymphoid tissue, minor salivary glands, and pharyngeal constrictor muscles.
The masticator space (Fig 1a–1e) extends from the most inferior aspect of the mandible up to the skull base. It can be divided into two components: the infratemporal fossa below the zygomatic arch and the temporal fossa above it. Spaces that border the masticator space include the buccal space anteriorly, the parotid space posteriorly, and the parapharyngeal space posteromedially. In addition to the muscles of mastication (ie, medial and lateral pterygoid, masseter, and temporalis muscles), which attach to the ramus and body of the mandible (also a part of this space), other important structures within the masticator space include the inferior alveolar branch of the mandibular nerve and inferior alveolar vessels.
The carotid space (Fig 1) surrounds the carotid vessels and extends from the skull base to the aortic arch. It contains the common or internal carotid artery (depending on the level); internal jugular vein; sympathetic plexus; cranial nerves IX, X, XI, and XII in the nasopharyngeal portion; cranial nerve X in the oropharyngeal and infrahyoid neck; and lymph nodes. Fat in the parapharyngeal space forms the anterior boundary of the carotid space in the suprahyoid neck.
The parotid space (Fig 1b–1e) is located directly lateral to the parapharyngeal space and posterolateral to the masticator space, extending from the level of the external auditory canal down to the angle of the mandible. The medial portion of the space reaches the anterolateral aspect of the carotid space, from which it is separated by the posterior belly of the digastric muscle. The contents of the parotid space include the parotid gland, facial nerve, external carotid artery, retromandibular vein, and lymph nodes.
The retropharyngeal space (Fig 1) is a midline space located between the pharyngeal constrictor muscle anteriorly and prevertebral muscles posteriorly, and it contains fat and lymph nodes only. It is bordered by the pharyngeal mucosal space anteriorly, carotid space laterally, and prevertebral portion of the perivertebral space posteriorly.
The perivertebral space (Fig 1) lies beneath the deep layer of deep cervical fascia and extends from the skull base to the fourth thoracic vertebral level. This space can be divided into prevertebral and paravertebral portions. The prevertebral portion contains the prevertebral muscles; vertebral artery and vein; scalene muscles; brachial plexus; phrenic nerve; and vertebral body, transverse process, and pedicle. The paravertebral portion contains the paravertebral muscles and posterior elements of the cervical vertebrae. The retropharyngeal space is anterior to and the carotid space is anterolateral to the prevertebral portion of this space, and the posterior cervical space is located lateral to the prevertebral and paraspinal portions.
In the infrahyoid neck, apart from the inferior extensions of the carotid, retropharyngeal, and perivertebral spaces, three other spaces, namely the visceral and the posterior and anterior cervical spaces, can be identified (Fig 1f–1h). The visceral space is bounded by the middle layer of the deep cervical fascia, extends from the hyoid bone to the mediastinum, and contains the thyroid and parathyroid glands, larynx, hypopharynx, esophagus, trachea, recurrent laryngeal nerve, and lymph nodes. The posterior cervical space is located posterior to the carotid space and lateral to the prevertebral and paravertebral portions of the perivertebral space and contains mostly fat. The spinal accessory nerve and the preaxillary portion of the brachial plexus pass through this space. No important structure is present in the anterior cervical space, which is located lateral to the visceral space and anterior to the carotid space.
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Image Guidance
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Image guidance is generally required for biopsy of nonpalpable deep-seated head and neck lesions. Sonographic guidance, with its inherent advantages of real-time imaging capability, decreased procedural time, ability to visualize vessels without use of intravenous contrast material, portability, lack of ionizing radiation, and decreased cost, is routinely used for biopsies of thyroid lesions, parotid gland lesions, and superficial cervical lymph nodes (11–13). However, the lack of an adequate acoustic window because of overlying bony structures such as the maxilla, mandible, mastoid and styloid process, and the air-containing aerodigestive system preclude the use of sonographic guidance for many deep-seated head and neck lesions.
CT, with its high spatial and contrast resolution, is the imaging modality of choice for biopsies of deep-seated head and neck lesions (1,3,5, 8,14–16). Air-containing spaces and bony structures do not result in significant image degradation, especially with the use of thin-section collimation. CT allows excellent delineation of intervening vital structures, permitting safe biopsy path planning. With CT, the operator can target the appropriate part of the mass and avoid areas of necrosis. We focus on the use of CT guidance for head and neck biopsies in this review.
Magnetic resonance (MR) imaging guidance has also been used for biopsies of head and neck lesions (4,6,17). The potential advantages of MR imaging as a guidance modality include its high contrast resolution, its multiplanar imaging capacity allowing the use of double oblique approaches, and its ability to demonstrate vessels without a contrast agent. However, the limited availability of open-configuration MR imaging systems, high cost, longer acquisition times, and need for MR imaging–compatible needles have prevented more widespread use of MR imaging guidance for head and neck biopsies.
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Patient Preparation and Lesion Localization
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Prebiopsy CT or MR images are reviewed to determine the patient position and approach. Patients are positioned in the supine, prone, or lateral decubitus position depending on the lesion location and the planned biopsy approach. Tilting the head away from the side of the target lesion is useful, especially for retromandibular and sub-mastoid approaches. Preliminary 3- or 5-mm-thick axial CT images are obtained through the lesion to determine the optimal entry site of the needle. In most patients, administration of intravenous contrast medium is not required during the biopsy procedure, but sometimes it is needed to help define the major vessels in the projected needle path. We perform all biopsies after administration of 1% lidocaine for local anesthesia supplemented with midazolam and fentanyl citrate for light conscious sedation. General anesthesia is usually required for biopsy with the transoral approach. The procedures are usually performed on an outpatient basis: patients are observed for 1 hour after the procedure to ensure their hemodynamic stability and to monitor their respiratory status.
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Biopsy Technique and Needle Selection
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Percutaneous biopsies of head and neck lesions are usually performed with the coaxial needle technique, which involves the initial placement of an 18- or 19-gauge thin-wall guide needle close to the target lesion followed by advancement of the biopsy needle through this needle to obtain tissue samples. We use a 20–22-gauge fine needle for obtaining aspirates for cytologic analysis and, if necessary, 20-gauge cutting needles for obtaining tissue cores for histologic evaluation. The small-caliber cutting needles now available consistently provide high-quality specimens adequate for histologic diagnosis in most cases, without increasing the complication rate. The coaxial technique has the advantage of allowing multiple samples of tissue to be obtained without the need for additional passes through overlying tissues, thus decreasing the procedure time, number of images required, risk of complications, and patient discomfort. Use of a Hawkins-Akins needle with a blunt trocar may reduce the risk of injury to major vessels and nerves in the needle path (18,19).
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Complications
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Major complications with CT-guided head and neck biopsy procedures are rare; most studies report no serious complications (1–8). Minor complications include pain, vasovagal reaction, minor infection, and minor bleeding. The potential of major vascular injury with the small-caliber biopsy needles is extremely low. Familiarity with the cross-sectional anatomy of the head and neck region and the location of major vessels and careful attention to planning the needle path minimize the chances of clinically significant hemorrhage. Walker et al (20) reported the case of a patient with internal maxillary artery pseudoaneurysm formation presenting with an oral hemorrhage 3 months after a CT-guided biopsy in the masticator space. According to those authors, prior radical neck surgery and radiation therapy increase the risk for vascular complications. Injury to cranial nerves and branches in this region with subsequent sensory or motor loss remains a theoretical concern; however, many large series have failed to demonstrate any such risk (1–8).
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Approaches for Skull Base, Head, and Suprahyoid Neck Lesions (including Upper Cervical Vertebrae)
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The approaches for biopsy of suprahyoid head and neck lesions, skull base lesions, and upper cervical vertebral lesions include the subzygomatic, retromandibular, paramaxillary, submastoid, transoral, and posterior approaches.
Subzygomatic Approach
Target Lesions.—
The subzygomatic (infratemporal, transcondylar, sigmoid notch) approach is ideally suited for biopsy of lesions in different parts of the masticator space. This approach can also be used for sampling lesions in the parapharyngeal, pharyngeal mucosal, and retropharyngeal spaces and the prevertebral portion of the perivertebral space. Caudal-to-cranial needle angulation with this approach allows access to lesions in the suprazygomatic portion (temporal fossa) of the masticator space and also to the skull base, including the pterygopalatine fossa region.
Anatomic and Technical Considerations.—
The needle is inserted below the zygomatic arch and advanced through the intercondylar (mandibular) notch between the coronoid process anteriorly, the mandibular condyle posteriorly, and the superior border of the mandibular ramus inferiorly (Figs 2, 3). As pointed out by Abrahams (2), the superficial location of the sigmoid notch allows easy angulation of the needle in various directions (anterior, posterior, cranial, or caudal), permitting access to multiple target sites. The needle traverses the masticator and parapharyngeal spaces during biopsy of lesions located in the pharyngeal mucosal, retropharyngeal, and prevertebral spaces and skull base lesions.
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Figure 3. CT scan shows a biopsy needle (solid arrow) that was inserted inferior to the zygomatic arch (Z) and advanced between the coronoid process (arrowhead) and mandibular condyle (open arrow) into a mass (M) in the left masticator space. The patient had undergone previous maxillectomy for maxillary sinus carcinoma.
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Cranial needle angulation allows the subzygomatic approach to be used for accessing lesions in the skull base and the suprazygomatic portion of the masticator space. Using a triangulation method, the physician estimates the needle angle from contiguous axial CT scans obtained from the level of the planned skin entry site to the level of the target lesion. The needle is inserted below the level of the zygomatic arch and advanced cranially and medially in small increments, and axial CT scans are obtained to check the needle tip position and angulation (Fig 4). Alternatively, a change in the degree of neck side flexion can bring the target lesion and the skin entry site into the same axial plane, allowing visualization of the entire needle length in a single axial CT image.
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Figure 4a. Subzygomatic approach. (a) CT scan shows a soft-tissue mass (arrowheads) in the right pterygopalatine fossa. A direct lateral approach is precluded by the zygomatic arch (Z). (b) CT scan shows a biopsy needle (arrow) inserted at a level caudad to the zygomatic arch. The needle was advanced in a cranial direction by using the triangulation method. (c) CT scan obtained at a more cranial level shows the needle tip (arrow) within the soft-tissue mass (M) in the pterygopalatine fossa.
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Figure 4b. Subzygomatic approach. (a) CT scan shows a soft-tissue mass (arrowheads) in the right pterygopalatine fossa. A direct lateral approach is precluded by the zygomatic arch (Z). (b) CT scan shows a biopsy needle (arrow) inserted at a level caudad to the zygomatic arch. The needle was advanced in a cranial direction by using the triangulation method. (c) CT scan obtained at a more cranial level shows the needle tip (arrow) within the soft-tissue mass (M) in the pterygopalatine fossa.
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Figure 4c. Subzygomatic approach. (a) CT scan shows a soft-tissue mass (arrowheads) in the right pterygopalatine fossa. A direct lateral approach is precluded by the zygomatic arch (Z). (b) CT scan shows a biopsy needle (arrow) inserted at a level caudad to the zygomatic arch. The needle was advanced in a cranial direction by using the triangulation method. (c) CT scan obtained at a more cranial level shows the needle tip (arrow) within the soft-tissue mass (M) in the pterygopalatine fossa.
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It has been suggested that having the patient keep his or her mouth open, preferably with a bite block, can help open up the space between the mandible and the zygomatic arch, facilitating needle insertion; however, in our experience as in that of others (2), this is rarely necessary.
With this approach, there is a theoretical risk of injury to the mandibular branch of the trigeminal nerve, the internal maxillary artery and its branches, including the middle meningeal artery, and the pterygoid venous plexus (Fig 2). The maxillary artery arises posterior to the neck of the mandible and is embedded in the parotid gland. The mandibular part runs horizontally forward along the medial surface of the ramus and passes between the neck of the mandible and the sphenomandibular ligament. The pterygoid part ascends obliquely forward and medially, either superficially (60%) or deep (40%) to the lateral pterygoid muscle, to enter the pterygopalatine fossa through the pterygomaxillary fissure. The middle meningeal artery arises from the mandibular part of the internal maxillary artery and ascends in the posterior part of the sigmoid notch deep to the lateral pterygoid muscle to enter the foramen spinosum. The mandibular nerve exits the cranial cavity through the foramen ovale and descends in the posterior part of the intercondylar notch; it runs downward medially to the lateral pterygoid muscle and a little anteriorly to the neck of the mandible to enter the inner surface of the mandibular ramus. The pterygoid venous plexus is located partly between the temporalis and lateral pterygoid muscles and partly between the two pterygoid muscles. However, as mentioned earlier, the risk of major injury to the vessels or nerves is extremely low. A needle inserted posteriorly close to the mandibular condyle and directed anteriorly may occasionally pass through a small anterior portion of the parotid gland, but this does not usually cause any problems (Fig 5).
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Figure 5a. Subzygomatic approach. (a) CT scan shows a mass (M) in the right pharyngeal mucosal space that extends into the carotid space and encases the carotid artery (arrowhead). (b) CT scan shows a biopsy needle (solid arrow) inserted through a small anterior portion of the parotid gland (arrowhead). The needle passes anterior to the mandibular condyle (c) and through the lateral pterygoid muscle (m) and parapharyngeal space (open arrow) into the anterior portion of the mass (M), away from the expected position of the internal carotid artery.
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Figure 5b. Subzygomatic approach. (a) CT scan shows a mass (M) in the right pharyngeal mucosal space that extends into the carotid space and encases the carotid artery (arrowhead). (b) CT scan shows a biopsy needle (solid arrow) inserted through a small anterior portion of the parotid gland (arrowhead). The needle passes anterior to the mandibular condyle (c) and through the lateral pterygoid muscle (m) and parapharyngeal space (open arrow) into the anterior portion of the mass (M), away from the expected position of the internal carotid artery.
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Retromandibular Approach
Target Lesions.—
Lesions in the deep parotid space, parapharyngeal space, pharyngeal mucosal space, and lower part of the retropharyngeal space are amenable to biopsy with a retromandibular (transparotid) approach. This approach can also be used for safely sampling lesions in the carotid sheath, if the vessels are displaced medially by the mass.
Anatomic and Technical Considerations.—
With the patient in the supine position and his or her head turned to the contralateral side, the needle is inserted posterior to the mandible and anterior to the mastoid process and advanced through the parotid gland (which is located behind the mandible, extending from the external auditory canal to the level of the mandibular angle) toward the target lesion (Fig 6). Care should be taken to identify and avoid the external carotid artery and retromandibular vein, which are located within the parotid gland immediately posterior to the mandibular ramus (Fig 1). The external carotid artery is the medial of the two vessels. Approximately midway between the tip of the mastoid process and the angle of the mandible, the external carotid artery turns laterally from the carotid sheath and passes anterior to the posterior belly of the digastric muscle to reach the posteromedial surface of the parotid gland. Within the substance of the parotid gland, it ascends behind the condyle and divides into its terminal branches, the superficial temporal and maxillary arteries. The seventh cranial nerve passes just lateral to the retromandibular vein (Fig 1). The styloid process serves as a useful bony landmark; keeping the needle anterior to the styloid process avoids injury to the internal carotid artery, which is located in a plane posterior to the styloid process (Fig 7). Occasionally, however, medial displacement of the carotid vessels by mass lesions may allow the needle to be advanced posterior to the styloid process (Fig 8).
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Figure 7a. Retromandibular approach. (a) CT scan shows a right parapharyngeal mass (M). Note the presence of the external carotid artery and retromandibular vein (arrow) in the anterior portion of the parotid gland (P). The carotid sheath vessels are located posterior to the styloid process (arrowhead). (b) CT scan shows a biopsy needle (solid arrow) inserted through the parotid gland (P) posterior to the vessels (open arrow). The needle passes anterior to the styloid process (arrowhead) and into the mass (M).
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Figure 7b. Retromandibular approach. (a) CT scan shows a right parapharyngeal mass (M). Note the presence of the external carotid artery and retromandibular vein (arrow) in the anterior portion of the parotid gland (P). The carotid sheath vessels are located posterior to the styloid process (arrowhead). (b) CT scan shows a biopsy needle (solid arrow) inserted through the parotid gland (P) posterior to the vessels (open arrow). The needle passes anterior to the styloid process (arrowhead) and into the mass (M).
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Figure 8a. Retromandibular approach. (a) CT scan shows a mass (M) in the carotid space with medial displacement of the carotid artery (arrowhead). Note the presence of vessels (arrow) in the parotid gland (P) immediately posterior to the mandibular ramus. (b) CT scan shows a biopsy needle (solid arrow) passing immediately posterior to the vessels (open arrow) in the parotid gland (P) and into the mass (M).
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Figure 8b. Retromandibular approach. (a) CT scan shows a mass (M) in the carotid space with medial displacement of the carotid artery (arrowhead). Note the presence of vessels (arrow) in the parotid gland (P) immediately posterior to the mandibular ramus. (b) CT scan shows a biopsy needle (solid arrow) passing immediately posterior to the vessels (open arrow) in the parotid gland (P) and into the mass (M).
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The presence of surrounding structures, such as the styloid process, internal carotid artery, mastoid process, and mandible, does not allow much room for needle angulation. Hence, it is difficult to access the skull base, prevertebral space, cervical spine, and portions of the retropharyngeal space with this approach (Fig 9). The potential risk of injury to the facial nerve, which courses through the parotid gland, limits the size of the biopsy needle that can be used with this approach. The use of thin needles precludes the option of obtaining a core specimen. The needle passes through the parapharyngeal space for biopsy of deeper lesions, and there is a potential risk of injury to the mandibular nerve branches and branches of the internal maxillary artery such as the middle meningeal and ascending pharyngeal arteries. Yousem et al (21) pointed out that a transparotid biopsy may occasionally yield salivary gland tissue, which may be confused with a salivary gland neoplasm of the parapharyngeal space. However, we have not encountered this problem in any of our patients.
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Figure 9a. Retromandibular approach. (a) CT scan shows a prevertebral mass (M). Needle placement posterior to the styloid process is not possible because of the presence of the internal carotid artery (arrow) and jugular vein (V) directly lateral to the mass. (b) As seen on the CT scan, the presence of vessels (open arrow) in the parotid gland (P) and of the styloid process (arrowhead) limits the angulation of the needle (solid arrow), restricting access to the mass (M).
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Figure 9b. Retromandibular approach. (a) CT scan shows a prevertebral mass (M). Needle placement posterior to the styloid process is not possible because of the presence of the internal carotid artery (arrow) and jugular vein (V) directly lateral to the mass. (b) As seen on the CT scan, the presence of vessels (open arrow) in the parotid gland (P) and of the styloid process (arrowhead) limits the angulation of the needle (solid arrow), restricting access to the mass (M).
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Paramaxillary Approach
Target Lesions.—
The paramaxillary (retromaxillary, buccal space) approach offers safe access to lesions in the infrazygomatic portion of the masticator space, the posterior portions of the parapharyngeal and pharyngeal mucosal spaces, the carotid sheath space, and the deep portion of the parotid space (22,23). It is particularly useful for lesions in the lateral part of the retropharyngeal space (eg, lateral retropharyngeal node of Rouviere) and the prevertebral portion of the perivertebral space because these lesions are difficult to access with other approaches. This approach can also be used for sampling lesions involving the anterior arch of the first cervical vertebra (C1) and the odontoid and body of the second (C2). In addition, it can be used to access the foramen ovale and other skull base lesions by using cranial needle angulation (24).
Anatomic and Technical Considerations.—
For the transfacial paramaxillary approach, the patient is placed in the supine position with his or her head turned to the contralateral side, and the needle is inserted through the buccal space inferior to the zygomatic process of the maxilla and advanced posteriorly between the maxilla and mandible (Fig 10). It is important to avoid the facial artery, which is easy to identify as it courses in the buccal space (Figs 10, 11). The needle passes through the buccinator muscle or anterior portion of the masseter muscle or between them for biopsy of lesions in the masticator space. The needle is advanced through the lateral and medial pterygoid muscles and the parapharyngeal space to sample more posterior lesions. The needle is advanced through the lateral and medial pterygoid muscles and the parapharyngeal space for biopsy of lesions in the retropharyngeal and carotid spaces and C1 and C2 lesions (Figs 11–14). This approach can also be used to access foramen ovale and other skull base lesions by using cranial needle angulation. Causing mild hyperextension of the neck by placing padding under the patient’s shoulders brings the skull base lesions and the skin entry site into the same axial plane, making needle placement and visualization easy.
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Figure 11a. Paramaxillary approach. (a) MR image shows an enlarged lateral retropharyngeal node (M) medial to the carotid artery (arrowhead). (b) CT scan shows an 18-gauge Hawkins needle (solid arrow) passing lateral to the facial artery (open arrow) and through the medial pterygoid muscle (m). A 22-gauge biopsy needle (arrowhead) was advanced coaxially through the guide needle into the mass (M).
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Figure 11b. Paramaxillary approach. (a) MR image shows an enlarged lateral retropharyngeal node (M) medial to the carotid artery (arrowhead). (b) CT scan shows an 18-gauge Hawkins needle (solid arrow) passing lateral to the facial artery (open arrow) and through the medial pterygoid muscle (m). A 22-gauge biopsy needle (arrowhead) was advanced coaxially through the guide needle into the mass (M).
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Figure 12a. Paramaxillary approach. (a) CT scan shows an enhancing mass (M) in the left carotid space medial to the carotid artery (arrowhead). (b) CT scan shows a needle (arrow) passing through the masticator and parapharyngeal spaces into the mass (M).
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Figure 12b. Paramaxillary approach. (a) CT scan shows an enhancing mass (M) in the left carotid space medial to the carotid artery (arrowhead). (b) CT scan shows a needle (arrow) passing through the masticator and parapharyngeal spaces into the mass (M).
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Figure 13. Paramaxillary approach. CT scan shows a biopsy needle (arrow) advanced through the masticator and parapharyngeal spaces and through the prevertebral muscles into a lesion (arrowheads) posterior to the anterior arch of the atlas.
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The needle trajectory and angulation with the paramaxillary approach are limited by the shape and size of the adjacent bones, such as the posterolateral wall of the maxillary antrum, the alveolar ridge, the lateral pterygoid plate, and the anterior margin of the mandibular ramus, limiting access to the anterior and medial portions of the parapharyngeal and pharyngeal mucosal spaces and the medial portions of retropharyngeal and prevertebral space lesions. In patients with a large maxillary antrum, the space between the maxilla and the mandible may be very narrow, limiting needle placement.
The pterygoid plates prevent inadvertent injury to the maxillary nerve and its main branches, which descend into the pterygopalatine fossa after exiting the foramen rotundum. Care should be taken to identify and avoid the carotid artery, especially during biopsy of lesions in the carotid sheath space, the retropharyngeal and prevertebral spaces, and C1 and C2. Other structures that could be injured with this approach include the branches of the mandibular and maxillary nerves in the masticator space, the pterygoid venous plexus, the internal maxillary artery and its branches in the masticator and parapharyngeal spaces, and the external carotid artery, which courses laterally deep to the lateral pterygoid muscle on its way to the parotid gland. Use of a Hawkins-Akins needle (Meditech, Westwood, Mass) with a blunt tip stylet as the outer guiding needle decreases the risk of injury to the vessels and nerves in these spaces.
Submastoid Approach
Target Lesions.—
The submastoid (retroparotid) approach is suitable for carotid sheath lesions when the carotid vessels are displaced medially by the lesion, for lesions in the anterolateral portion of the perivertebral space that displace the carotid sheath anteriorly, and occasionally for lesions in the parapharyngeal space.
Anatomic and Technical Considerations.—
The patient is placed in a prone position or in a supine position with his or her head turned to the contralateral side. The needle is inserted at a variable distance inferior to the mastoid tip and advanced through the sternocleidomastoid muscle (Fig 15). Because the needle is then passed posterior to the parotid gland, there is no risk of damage to the parotid gland, intraparotid vessels, or facial nerve with this approach. The needle is advanced anteriorly and medially and occasionally cranially toward the lesion (Fig 15).
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Figure 15. Submastoid approach. CT scan obtained with the patient’s head turned to the contralateral side shows a biopsy needle (arrow) passing through the sternocleidomastoid muscle (m) into a left carotid space mass (M). Note the carotid artery (arrowhead), which is displaced anteriorly by the mass. The needle was inserted at a level 1 cm below the tip of the mastoid process (not shown).
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One must carefully avoid the vertebral artery, especially during biopsy of anterior or lateral perivertebral lesions at the C1–C2 level (Fig 1d, 1e). After coming out of the C2 foramen, the vertebral artery turns outward to reach the lateral aspect of the lateral mass of C2 and runs cranially along the lateral mass of C2 before it enters the C1 foramen. The artery then exits the C1 foramen and turns posteriorly to course along the upper surface of the C1 lamina. The use of contrast medium can improve visualization of the vertebral artery and be a useful adjunct for needle path planning. Because of the presence of the carotid and vertebral arteries in the needle path, use of the submastoid approach for biopsy of deeper lesions located in the pharyngeal mucosal, parapharyngeal, or retropharyngeal spaces is not possible unless those vessels are displaced by the lesion.
Transoral Approach
Target Lesions.—
The transoral approach is a well-established open surgical procedure for access to the atlantoaxial region (25). It can also be used for percutaneous biopsy of lesions in the posterior pharyngeal mucosal space, the retropharyngeal space, the prevertebral part of the perivertebral space, and also for lesions involving the anterior portions of the C1 and C2 vertebrae, including the odontoid (26). A posterior or lateral approach to this region is associated with risk of injury to the vertebral artery.
Anatomic and Technical Considerations.—
The use of this approach requires general anesthesia. With the patient in the supine position, a mouth opener is applied after the patient is anesthetized. A trajectory between the tongue and uvula is chosen, and the uvula is pushed away with a retractor or nasal tube. The intended site of needle puncture in the posterior pharyngeal wall is sprayed and infiltrated with local anesthetic. The needle is advanced through the patient’s open mouth, inserted through the posterior pharyngeal mucosa, and advanced posteriorly through the retropharyngeal space and prevertebral muscles toward the target lesion (Fig 16). This is a relatively safe approach because no important structure lies between the posterior pharyngeal wall and the bone. Maintaining a sterile field is often a problem with the transoral approach, and because of the inherently contaminated nature of these biopsies, use of antibiotics is recommended. During biopsy of lesions in the anterior arch of the atlas or the odontoid process, care should be taken to avoid any slip because of the proximity of the spinal cord.
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Figure 16. Transoral approach. CT scan shows a needle (arrow) inserted through the open mouth and advanced through the retropharyngeal and prevertebral tissues into a soft-tissue mass (arrowheads) involving the tip of the odontoid and the anterior arch of the atlas.
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Posterior Approach
Target Lesions.—
The posterior approach is used for percutaneous biopsies of lesions involving the spinous process, lamina, and articular pillar of the upper cervical vertebrae (Figs 17, 18). It is also used for occipital condylar lesions and masses located in the posterior and lateral portions of the perivertebral space. This approach can also be used occasionally for sampling lateral masses involving C1 and C2, provided care is taken to identify and avoid the vertebral artery (Fig 19).
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Figure 17. Posterior approach. CT scan obtained with the patient in the prone position shows a needle (arrow) advanced through the posterior paravertebral muscles for biopsy of a lytic lesion (arrowheads) involving the spinous process and lamina of the C2 vertebra.
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Figure 18. Posterior approach. CT scan obtained with the patient in the prone position shows a needle (white arrow) passing through the posterior paravertebral muscles into a lytic process (black arrows) involving the lamina, articular pillar, and pedicle of the C3 vertebra.
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Abstract
Introduction
