Skull base metastases (SBM) are rare among all tumors affecting the base of the skull. Because of their rarity, they have received limited attention in the published medical literature. Several clinical syndromes associated with SBM have been described. Knowledge of these syndromes and maintenance of a high index of suspicion are important for an early diagnosis. The majority of patients are best managed by radiotherapy. Other therapeutic options include stereotactic radiosurgery, chemotherapy, and surgery. Surgical resection is reserved for a minority of well-selected patients. The decision to intervene surgically is based on patients’ clinical status, the degree of control of systemic disease, the accessibility of the lesion, and the potential morbidity of the procedure. Well-designed trials and evidence-based practice guidelines are not available. The management of these patients largely depends of the experience of the treating medical team.
Brain metastasis is a common medical problem. According to the 2008 American Cancer Society Registry, it is estimated that approximately 1.4 million Americans are diagnosed with cancer every year, nearly 40% of them develop one or more brain metastasis. The treatment options for these patients include surgery, whole brain radiation, stereotactic radiosurgery (SRS), and chemotherapy. Considerable efforts have been made to determine the optimal management strategy. As a result, a large number of well-designed studies have been conducted, and evidence-based clinical practice guidelines are currently available. Skull base metastases (SBM), however, have received limited attention, undoubtedly related to the relative rarity of these lesions. The current medical literature on SBM consists of case reports and small case series. Comparative studies for different treatment options are not available, and evidence-based practice guidelines are nonexistent. Currently, management of these patients is based on the limited available data in the literature and on the clinical experience of the treating medical team.
Epidemiology
Autopsy series reveal a high incidence of SBM. Belal found a 3% incidence of temporal bone metastases in the general population; whereas, Jung and colleagues and Gloria-Cruz and colleagues reported a 24% and 22.2% incidence, respectively, of temporal bone metastases in subjects with a known history of cancer. Most of these metastases are clinically silent, however, and clinical series reveal a much lower incidence of SBM. Hall and colleagues, for instance, noted only a 0.13% incidence of cranial neuropathy caused by osseous metastases in subjects with breast cancer. SBM are rare among tumors of the skull base reported in surgical series. In an article reporting the experience of George Washington University Medical Center in the surgical treatment of skull base tumors, Morita and colleagues found that metastatic lesions constituted less than 5% of their subjects.
In 1981, Greenberg and colleagues reported the experience of Sloan-Kettering Cancer Center in the management of SBM. Their series spanned 7 years and consisted of 43 subjects. The most common tumors found were breast cancer (17 subjects), lung cancer (6 subjects), and prostate cancer (5 subjects). In a review of the literature published in 2005 analyzing 279 cases that were identified in the English and French literature, prostate cancer was actually the most common (38%) followed by breast cancer (20%). All other pathologies constituted less than 10% each, with most of them accounting for less than 5% of the subjects.
Clinical presentation
SBM are typically diagnosed in patients already known to have metastatic cancer. In approximately 28% of cases, these lesions can be the first sign of cancer. In most cases, it is thought that these lesions spread by hematogenous dissemination. Retrograde venous seeding along the extensively interconnected midline venous system has also been postulated as a possible mechanism, mainly in the case of prostatic cancer. Malignant tumors can also reach the skull base through direct extension of a head and neck cancer. These cases, however, do not represent true metastasis.
SBM may be asymptomatic; for example, it may be discovered incidentally on routine imaging for cancer staging or during brain imaging for head trauma. SBM should be strongly suspected, however, when patients with a known history of cancer present with cranial neuropathy or craniofacial pain. Several clinical syndromes determined by the anatomic location of the lesion have been described. In their review of the literature, Laigle-Donadey and colleagues found that the parasellar and sellar syndromes were the most common (29%) followed by the gasserian ganglion (6%) and jugular foramen syndromes (3.5%). No distinct syndrome could be described in 33% of the cases.
Orbital Syndrome
The orbital syndrome is characterized by orbital or supraorbital pain, frontal headache, proptosis, diplopia, and blurred vision. On examination, there is typically periorbital swelling, tenderness, palpable mass, and decreased visual acuity ( Fig. 1 ).
Sellar/Parasellar Syndrome
The parasellar syndrome is characterized by frontal and supraorbital headache, diplopia, facial pain, and hypoesthesia. The physical examination reveals ocular palsy, decreased facial sensation, and occasionally mild proptosis. There may be signs and symptoms of hypopituitarism, diabetes insipidus, and visual loss.
Gasserian Ganglion Syndrome
Metastases to the middle cranial base may cause pain, numbness, and paresthesia along the trigeminal nerve distribution. The symptoms can mimic those of idiopathic trigeminal neuralgia. On examination there is usually sensory loss in the distribution of one or more of the trigeminal divisions with some dysfunction of the motor root. Extension into Dorello’s canal can lead to a concomitant sixth nerve palsy.
Temporal Bone Syndrome
The temporal bone syndrome is characterized by hearing loss and otalgia. Vertigo and tinnitus are much less common. The hearing loss can be conductive, related to dysfunction of the eustachian tube with secondary otitis media, or sensorineural caused by involvement of the cochlear nerve. The physical examination typically shows periauricular swelling and facial nerve palsy.
Jugular Foramen Syndrome
This syndrome is characterized by occipital or postauricular pain, hoarseness, and dysphagia. On physical examination, there is usually weakness of the palate, paralysis of the vocal cords, and weakness of the sternocleidomastoid and trapezius muscles. Occasionally, glossopharyngeal neuralgia can be part of the clinical picture.
Occipital Condyle Syndrome
The occipital condyle syndrome is characterized by occipital pain and neck stiffness. Dysarthria and dysphagia are common features of this syndrome. The physical examination typically reveals the presence of tongue weakness, atrophy, and fasciculation.
Clinical presentation
SBM are typically diagnosed in patients already known to have metastatic cancer. In approximately 28% of cases, these lesions can be the first sign of cancer. In most cases, it is thought that these lesions spread by hematogenous dissemination. Retrograde venous seeding along the extensively interconnected midline venous system has also been postulated as a possible mechanism, mainly in the case of prostatic cancer. Malignant tumors can also reach the skull base through direct extension of a head and neck cancer. These cases, however, do not represent true metastasis.
SBM may be asymptomatic; for example, it may be discovered incidentally on routine imaging for cancer staging or during brain imaging for head trauma. SBM should be strongly suspected, however, when patients with a known history of cancer present with cranial neuropathy or craniofacial pain. Several clinical syndromes determined by the anatomic location of the lesion have been described. In their review of the literature, Laigle-Donadey and colleagues found that the parasellar and sellar syndromes were the most common (29%) followed by the gasserian ganglion (6%) and jugular foramen syndromes (3.5%). No distinct syndrome could be described in 33% of the cases.
Orbital Syndrome
The orbital syndrome is characterized by orbital or supraorbital pain, frontal headache, proptosis, diplopia, and blurred vision. On examination, there is typically periorbital swelling, tenderness, palpable mass, and decreased visual acuity ( Fig. 1 ).
Sellar/Parasellar Syndrome
The parasellar syndrome is characterized by frontal and supraorbital headache, diplopia, facial pain, and hypoesthesia. The physical examination reveals ocular palsy, decreased facial sensation, and occasionally mild proptosis. There may be signs and symptoms of hypopituitarism, diabetes insipidus, and visual loss.
Gasserian Ganglion Syndrome
Metastases to the middle cranial base may cause pain, numbness, and paresthesia along the trigeminal nerve distribution. The symptoms can mimic those of idiopathic trigeminal neuralgia. On examination there is usually sensory loss in the distribution of one or more of the trigeminal divisions with some dysfunction of the motor root. Extension into Dorello’s canal can lead to a concomitant sixth nerve palsy.
Temporal Bone Syndrome
The temporal bone syndrome is characterized by hearing loss and otalgia. Vertigo and tinnitus are much less common. The hearing loss can be conductive, related to dysfunction of the eustachian tube with secondary otitis media, or sensorineural caused by involvement of the cochlear nerve. The physical examination typically shows periauricular swelling and facial nerve palsy.
Jugular Foramen Syndrome
This syndrome is characterized by occipital or postauricular pain, hoarseness, and dysphagia. On physical examination, there is usually weakness of the palate, paralysis of the vocal cords, and weakness of the sternocleidomastoid and trapezius muscles. Occasionally, glossopharyngeal neuralgia can be part of the clinical picture.
Occipital Condyle Syndrome
The occipital condyle syndrome is characterized by occipital pain and neck stiffness. Dysarthria and dysphagia are common features of this syndrome. The physical examination typically reveals the presence of tongue weakness, atrophy, and fasciculation.
Related posts:
Review of Imaging Techniques in the Diagnosis and Management of Brain Metastases
Radiotherapy for Brain Metastases
Radiosurgical Management of Brain Metastases
Surgical Management of Brain Metastases
Investigational Therapies for Brain Metastases
Evidence-Based Guidelines for the Management of Brain Metastases
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