Common Clinical Manifestations of Craniovertebral Junction Tumors

Tumors of the craniovertebral junction, whether extracranial with secondary involvement of the intracranial and intraspinal structures or primarily intracranial with secondary extension into the spinal canal, have characteristics that reflect compression of neighboring structures or traction. They also may have distal effects such as hydrocephalus, syringohydromyelia, and vascular compromise.^9,13,14 Chordoma often involves the cranial base and upper cervical spine extensively and may be associated with only minimal complaints of headache and neck pain for several years. Unfortunately, this hiatus is followed by a rapid progression of brainstem and cervical spinal cord dysfunction that brings the lesion to light. In the report of Meyer and coworkers, the time from the onset of symptoms to the diagnosis of extramedullary tumor at the foramen magnum was 2.5 years.²

The clinical presentation of craniovertebral junction tumors can be divided into intracranial lesions, “straddle lesions,” and those affecting the high cervical spinal cord.⁷ The effects of vascular compromise and alterations of cerebrospinal fluid (CSF) circulation add to the constellation of symptoms and signs.

Patients with intracranial lesions present with involvement of the lower cranial nerves, brainstem dysfunction, and occasionally cerebellar symptoms. Patients with straddle lesions have a paucity of cranial nerve dysfunction and a predominance of high cervical myelopathy. High cervical lesions do not produce cranial nerve and cerebellar signs, except for involvement of the spinal accessory nerve and sometimes the descending tracts of the trigeminal nerve and the lower decussations of the motor and sensory tracks.¹⁵

The most common presentation is pain referred to the second cervical dermatome.¹ The head is held flexed, and the condition may resemble torticollis. The pain is described as an aching sensation that is aggravated by neck and head motion and referred to the suboccipital region. Unfortunately, the symptom of pain alone may predate other clinical findings for many years. Paresthesias or dysesthesias of the face, hands, and limbs are frequently reported. An abnormal cold sensation of the lower extremities was described by Elsberg and Strauss⁷ and by Beatty¹³ as being pathognomonic of lesions of the high cervical cord. Most frequently, pain and temperature sensation is affected, followed by loss of joint sensation. This finding is seen in the upper extremities and may then proceed clockwise around the limbs. A suspended sensory loss with patches of preservation of sensation in the upper extremities may confuse the presentation. “Dissociated” sensory loss has been described in about one fourth of extracranial lesions of the cervicomedullary junction, even though this finding has been considered to reflect an intramedullary process.²

Spastic weakness of the extremities is a prominent feature in patients with tumors in this region. The weakness may begin in the ipsilateral limb and progress to the lower limb of the same side, followed by weakness of the contralateral lower limb; finally, weakness becomes apparent in the contralateral upper limb. This distinct progression of motor symptoms is an important characteristic of lesions of the cervicomedullary junction.¹⁵ Localized wasting of the intrinsic muscles of the hand may develop ipsilateral to the lesion. Taylor and Byrnes postulate venous stagnation of the anterior horn cells and the lower cervical cord as a result of decreased venous drainage, which typically occurs rostral to the lower portion of the cervical spinal cord.¹⁶ Other proposed mechanisms include anterior spinal artery compression, hydromyelia secondary to CSF obstruction, venous obstruction with spinal cord edema, and spinal cord rotation with contralateral traction.

A tumor at the foramen magnum may produce a mixture of upper motor neuron findings in the upper and lower extremities. This pattern reflects the pyramidal decussation that begins just below the obex and ends near the uppermost cervical spinal cord. The more medial fibers of the pyramidal tract carry impulses to the upper extremities and cross superior to the lateral fibers that serve the lower extremities. Similarly, the sensory decussation of the medial lemniscus may produce a varied pattern of sensory abnormalities.¹⁷ Thus, a tumor situated at the ventral aspect of the cervicomedullary junction can cause sensory aberrations in the lower extremities first. The syndrome of cruciate paralysis has been associated with trauma as well as tumors with basilar invagination.¹⁸

Transient symptoms may be due to both vascular changes and instability at the craniovertebral junction.^1,19 Such symptoms can manifest as paralysis, paresthesias, drop attacks, and vertebrobasilar syndromes such as migraine and visual loss in the homonymous visual fields. Cranial nerve palsies may be the result of nuclear involvement in the brainstem, traction, compression of the subarachnoid segments, or interosseous disease.^1,15 The most common cranial nerves affected are the vagus, glossopharyngeal, and hypoglossal. Their involvement leads to dysphagia, slurred speech, and repeated episodes of aspiration into the tracheobronchial tree, resulting in pneumonia and weight loss. Tumors of the upper cervical canal can present with involvement of the spinal root of the accessory nerve, manifesting as torticollis and weakness of the trapezius and sternocleidomastoid muscles. About 15% to 20% of patients develop tinnitus, vertigo, and hearing loss related to involvement of the vestibulocochlear nerve.¹⁵

The differential diagnoses considered most often by Meyer and coworkers in their initial evaluation of 102 documented cases of benign extramedullary tumors of the foramen magnum included cervical spondylosis (25%), multiple sclerosis (18%), syringomyelia (17%), intramedullary tumor (15%), Chiari’s malformation (5.5%), and carpal tunnel syndrome (5.5%).² Other erroneous diagnoses in patients with lesions at the craniovertebral junction are intramedullary tumors of the brainstem and upper cervical cord, amyotrophic lateral sclerosis, and subacute combined degeneration. Cervical spondylosis may be difficult to differentiate when it coexists. The presentation of restless legs syndrome in patients with craniovertebral compressive pathology has been well documented by Glasauer and Egnatchick.²⁰

Neurodiagnostic Imaging

The complex anatomy and pathology of tumors in this region demand precise definition and depiction of the tumor’s extent and its relationship to the vital structures of the brainstem and spinal cord, lower cranial nerves, and vascular structures. Thus, complementary multimodality imaging includes plain radiography, magnetic resonance imaging (MRI), magnetic resonance angiography, computed tomography (CT), and three-dimensional CT angiography. The sensitivity of MRI is greatly enhanced by the addition of intravenous gadolinium and by performing separate magnetic resonance venography and angiography.⁵

Cerebral angiography is useful in understanding the dynamics of collateral circulation and tumor vascularity. Temporary balloon occlusion is a means of assessing a patient’s tolerance of vascular occlusion of the carotid or vertebral circulation before surgery.¹⁵ Such information is especially useful when lesions are encased by tumor. These two tests provide information about the resectability of difficult lesions.

Electrophysiologic Tests

Intraoperatively, we monitor somatosensory brainstem evoked potentials and perform facial electromyography when lesions extend to the cerebellopontine angle and when using the preauricular infratemporal fossa approach.^15,21,22 The intraoperative evaluation of cranial nerve IX and cranial nerve X function is accomplished by placing electrodes in the soft palate and against the true vocal cords, incorporating these latter electrodes in the endotracheal tube for the anesthetic. Hypoglossal nerve electromyography supplements the evaluation with an electrode placed directly into the tongue. Brainstem monitoring still yields a significant number of false-negative and false-positive results, but improved techniques make these adjuncts useful in the intraoperative assessment of the function of the cervicomedullary junction.

Surgical Approaches and Decision Making

The goal of treating benign osseous pathology differs from that of treating malignant disease, in which complete excision is the objective. Benign lesions create a space among the neurovascular structures, thereby allowing surgical debulking and resection “from within.” Malignant disease, however, requires a much more radical resection with clean margins. In most instances, benign lesions such as chordomas are radioresistant; hence, gross total resection should be the aim. Craniovertebral stability, both before and after operative intervention, must be considered in the development of approaches.^14,19,23 Thus, the factors that influence the specific treatment of tumors arising in this region are (1) mechanism of compression and direction of encroachment, (2) whether the lesion is benign or malignant, (3) whether the lesion has an associated vascular or intramedullary component (e.g., syringomyelia), (4) craniospinal stability, and (5) patient age. Lesions of the craniovertebral junction do affect the pediatric population, although to a lesser extent than they affect adults.^3,5,24 In children, the potential for growth, concerns about stability, and the patient’s size are critical. From this perspective, midface growth centers are the nasal septum and the pterygoid plates. Hence, in a child, a transpalatal approach to the clivus and the sella would be considered before a sublabial transsphenoidal or a maxillary drop-down procedure, with the goal of avoiding damage to the growth centers.²⁵

Advances in neurodiagnostic imaging and microsurgical instrumentation have allowed the development of extensive surgical approaches based on an understanding of the complex anatomy, the craniovertebral dynamics, and the site of encroachment. Consequently, the entire circumference of the foramen magnum is within the neurosurgeon’s reach (Fig. 308-1). However, several surgical limitations and considerations must be appreciated when designing an approach to the craniovertebral junction (Table 308-2). The most frequently used anterior route is the transoral-transpalatopharyngeal approach.^1,25–27 Laterally, this approach is limited by the pterygoid plates, the hypoglossal canal, the eustachian tubes, and the width between the vertebral arteries. The limitation imposed by the pterygoid plates can be overcome by using a transmaxillary route with down-fracture of the maxilla and an extended maxillotomy if needed.^1,28 A combined exposure with mandibulotomy and midline glossotomy lowers the midline exposure to C5.^5,29,30 The disadvantages of the ventral approaches are overshadowed by their easy access, ability to cross the midline, and vertical extensions.^31,32 The ventral and dorsal midline approaches permit the anterior and posterior 90 degrees of the craniovertebral junction to be scanned, respectively.

FIGURE 308-1 A, Artist’s illustration of extent of exposure available via various approaches to the craniocervical region in a lateral perspective. B, Illustration of the extent of exposure via various approaches to the clivus, foramen magnum, and upper cervical spine as viewed from above the skull base.

As a general rule, midline extra-axial tumors are best approached in an extra-axial fashion without retracting the brain or violating the dura. A lateral avenue should be used for tumors that are situated laterally.^33–35 The transsphenoidal-transsphenoethmoidal approach provides a shallow operative depth and is well tolerated as a route to the upper two thirds of the clivus.^36–38 This exposure provides better access to the contralateral side; hence, at times, a bilateral approach may be necessary. The transfacial routes provide wide access to the anterior and midline skull base and include the ventral aspect of the clivus.^39,40 This approach is ideal for treating extradural lesions such as chordomas, angiofibromas, and fibrous dysplasias. Dural coverage must be provided by vascularized muscle flaps obtained from the temporalis muscle.

The transbasal approach provides access to the anterior skull base. Unless combined with removal of the supraorbital bar, this approach is limited by the distance between the two optic nerves and the need to work beneath the sella turcica.²³ Nonetheless, we have used this approach in several patients and have achieved good reconstruction of the floor.

A lateral extrapharyngeal route is effective and safe for reaching the upper cervical spine.⁴¹ At the clivus, however, access becomes difficult because of the pyramidal narrowing of the exposure at the depths of the wound. In an effort to correct this problem, we reroute the facial nerve with upward displacement of the angle of the mandible,²⁵ thereby exposing the lower clivus. We believe that this approach should be limited to metastases, chordomas, and plasmacytomas that affect the axis and atlas vertebrae. Its use for treatment of basilar invagination and intradural pathology is limited.

The true lateral-transcondylar approach to the ventral aspect of the lower brainstem and clivus, as well as the upper cervical cord, demands resection of a portion of the lateral atlantal mass and the occipital condyle. Exposure of the lower clivus and the ventral brainstem is enhanced when combined with a retrosigmoid craniectomy.³⁴ It is useful in the treatment of both extradural and intradural lesions such as chordomas, meningiomas, and neurofibromas.^4,14,33 When combined with infratemporal procedures, it allows both anterior and posterior extensions that overcome the limitations of the sigmoid sinus and the hypoglossal nerve.^1,34,42 The risk for CSF leak and the possibility of destabilization are high. Troublesome bleeding is routinely encountered from the paravertebral venous plexuses.

The posterolateral route has been recognized for many years. It enables scanning of the foramen magnum to the 90 degrees available with the posterior midline approach as well as the 90 degrees available with the lateral transcondylar approach.^1,43 The latter uses a standard midline posterior exposure with a lateral cerebellar approach and includes partial resection of the mastoid process and the posterior third to half of the occipital condyle to provide exposure of the jugular bulb and the medial aspect of the lateral atlantal mass. This provides access to the vertebral artery, which can be rerouted and displaced from the foramen transversarium, thus allowing for control from the C2 level upward. The ability to create a fusion makes this an ideal approach for posterior, lateral, and ventrolateral lesions. Thus, the entire circumference of the foramen magnum is accessible.

The expanded endonasal endoscopic approach is a valid, minimally invasive alternative for treatment of centrally located clivus chordomas or any such lesions or could be an adjunct for the central part of a lesion with lateral extension.^36,44–46 A standard nasal access is used with the binostril approach, with the endoscope typically positioned in the right superior nasal cavity by one surgeon who is responsible for maintaining the visual field. This arrangement allows a second surgeon to use both hands and an instrument in each nostril for the resection of the tumor. Dissection of both middle turbinates can expose a large working field, although this is not essential. The mucoperiosteal flaps from the middle turbinate can be used to close off a CSF leak.³⁸ The medial wall of the clival carotids represents the lateral limits of the clival exposure. The floor of the sphenoid is further drilled to get access to the mid and lower clivus. Resection of medial pterygoid process can be performed for exposure of lateral extension of the lower part of the tumor. A total ethmoidectomy can augment exposure into the upper clivus. Closure is performed with multilayered reconstruction technique. In the series by Dehdashti and associates,⁴⁶ 12 patients underwent such operation over a 3-year span. There were four CSF leaks. One patient developed hydrocephalus and one new deficit with clot and one pneumocephalus. Cranial deficits improved over time. A gross resection was accomplished in 7 of the 12 patients. In the series by Frank and associates,⁴⁵ nine chordomas were approached in this fashion, with a total removal in three. An internal carotid injury occurred in one patient, with two persistent CSF leaks.

Extradural Tumors of the Craniovertebral Junction

Neoplasms that affect the craniovertebral junction are extradural or intradural in location. Glomus jugulare tumors and congenital and acquired abnormalities of the craniovertebral junction are discussed elsewhere.

Imaging Characteristics

Cranial-based chordomas are clearly defined by the use of high-resolution CT, on which they appear as solitary or multiple areas of decreased attenuation within the clivus. T2-weighed MRI reveals a bright signal from the marrow in the skull base, signifying replacement of bone by tumor.^9,25 At times, calcification is noted in the abnormal areas in the retropharyngeal space, representing sequestered bone fragments in tumor. Chordomas enhance with intravenous contrast and are well visualized by MRI. Chordomas are isointense on T1-weighted MRI (Fig. 308-2).

FIGURE 308-2 A, Composite of parasagittal and midsagittal gadolinium-enhanced magnetic resonance imaging (MRI) of the head and upper spinal canal in a 42-year-old women with craniocervical chordoma. She presented with dysphagia, nasal regurgitation, unsteady gait, headaches, and tongue atrophy. Note the hindbrain herniation as a result of the tumor mass. B, Composite of T1-weighted gadolinium-enhanced MRI in the axial plane through the fourth ventricle (left) and foramen magnum (right). There is retropharyngeal as well as extradural and intradural tumor that engulfs the left vertebral artery. C, Reformatted computed tomography (CT) of the craniovertebral junction in the frontal projection through the plane of the odontoid process. The occipital condyles are eroded bilaterally. D, Composite of postoperative T1-weighted MRI in the parasagittal and midsagittal plane at the craniocervical junction. The hindbrain herniation has receded significantly. There is no evidence of tumor visible 11 years after transpalatopharyngeal resection of the clivus and craniovertebral junction chordoma.