Head & Neck Tumors: Minimally Invasive Microsurgery of the Skull Base
Surgical resection of head and neck tumors extending to or through the skull base requires special expertise combining the talents of skull base surgeons and head and neck surgeons; the multidisciplinary team may also include neuroradiologists and radiation and medical oncologists.
Newer approaches including endoscopic techniques to access these tumors have made a dramatic impact on the overall outcomes by reducing mortality and morbidity, reducing hospital stay and improving overall prognosis. Many head and neck cancers that were previously thought to be inoperable have been successfully removed through small and precise exposures by these techniques.
One of the challenges is to resect the tumor without any disfiguring scars. This can be done by hiding all the scars either in the hairline, the conjunctiva (inside the eyelid) or inside the mouth. The advent of minimally invasive endoscopic techniques has facilitated the resection of these tumors completely through such "hidden" or natural openings such as the nostril, the hair of the eyebrow or the inside of the eyelid.
At the Skull Base Institute we have combined traditional techniques such as the infratemporal fossa approach with minimally invasive endoscopic approaches in order to resect completely massive tumors of the skull base with minimum discomfort and complications and maximum safety and preservation of vital neurologic and cranial nerve functions.
Many of these patients require neuroradiologic embolisation of their tumors 48 hours prior to surgery and in many occasions they also require a carotid balloon test occlusion. These neuroradiologic tests allow us to perform the surgery safely, minimizing the amount of bleeding from the tumor and also allowing us to know in advance whether any blood vessels including either carotid or any of their branches can be safely occluded without the patient suffering any adverse effects. To date we have collaborated with our colleagues in interventional neuroradiology on hundreds of such patients who have had their tumors successfully embolised preoperatively followed by a surgical resection 48 hours later.
Some of these patients have also required adjuvant radiation therapy and chemotherapy either systemically or intraarterially. For those patients we have combined our efforts with colleagues in the fields of radiation oncology and medical oncology in order to provide our patients with the most up to date multidisciplinary therapies available.
Overview
Head and neck tumors is the term given to a variety of tumors that develop in the oral cavity, nasal passages, paranasal sinuses, orbits, larynx, pharynx and salivary glands. Many authorities also include skin tumors of the face and neck and tumors of the cervical lymph nodes under the broad classification of head and neck tumors.
Head and neck tumors may be benign or malignant. The most common malignant tumor of the head and neck is squamous cell cancer. Specific sites, such as the salivary glands or the paranasal sinuses, may have other types of cancer. Each year, approximately 60,000 Americans are diagnosed with new head and neck cancers (not including skin cancers that occur in this region).
Since many of these tumors do not differentiate between where the skull base starts and where the brain ends, they infiltrate the skull base and ultimately invade the brain. When the preoperative history, physical examination, and appropriate imaging techniques reveal probable or definite intracranial involvement, or when the location of the tumor requires an intracranial exposure for en bloc removal, a combined multidisciplinary effort is required.
Head and neck tumors that involve the skull base include:
Orbital tumors
Paranasal sinus tumors
Rhabdomyosarcomas
Esthesioneuroblastomas
Infratemporal fossa tumors
Causes
The cause of head and neck tumors is unknown; however, researchers are continuously working to identify the specific genetic factors that influence the progression and outcome of these tumors. Most head and neck "cancers" arise after prolonged exposures to known risk factors and these cancers are often considered preventable. Risk factors for head and neck cancers include tobacco and excessive alcohol use, a history of pre-cancerous lesions, and exposure to cancer-causing agents in the environment.
Symptoms
Benign tumors of the head and neck often cause no symptoms other than the presence of a hard or firm lump, Other symptoms are site specific and are due to direct pressure by the slow growing tumor on adjacent structures. Cranial extension of head and neck cancers often involves areas of the respiratory tract, the digestive tract, as well as the visual tracts, thus often interfering with the vital functions of eating, seeing and breathing. However, in many occasions, early symptoms or warning signs are subtle and non-specific and many of these symptoms can be caused by other, non-cancerous conditions.
Some of the most common presenting symptoms of head and neck cancers are:
A lump or swelling in the neck
A sore in the mouth that does not heal or that bleeds easily
A red or grayish patch in the mouth
Frequent bleeding per nose, ongoing nasal congestion or chronic sinus infections
Persistent sore throat
Persistent hoarseness or a change of voice
Persistent pain in the neck, throat, or ears
Blood tinged sputum
Difficulty chewing, swallowing, or moving the jaws or tongue
Numbness in the tongue or other areas
Loosening of teeth or dentures that no longer fit
Diagnosis
Physical examination focusing on the head and neck area and a thorough medical history noting all the symptoms and risk factors associated with the development of different types of head and neck tumors are the first steps in the diagnosis.
Radiographic imaging tests include plain X-rays, computed tomography (CT) scans and magnetic resonance imaging (MRI). Positron emission tomography (PET) scans may also be useful in some cases. Other possible tests in malignant cases to scan for metastasis or primaries in other areas of the body include ultrasound, chest x-rays and radionuclide bone scans.
Subsequently, a biopsy (cutting a small piece of the tumor and sending it for histopathological examination) is typically taken from the suspected tumor. The biopsy is often the most important piece of information and the only definite way to differentiate benign from malignant neoplasms. If the suspicious lesion is in the mouth or nose, the biopsy can often be done in the office on an outpatient basis. However, if it is located in deeper regions, the biopsy will probably be done in the operating room under a general anesthetic, this is usually done endoscopically.
The different types of biopsies are:
Superficial lesions:
Punch biopsy or shave biopsy - ideal for readily accessible lesions of the skin or mucosa
Deeper lesions:
Needle biopsy - Fine needle aspiration (FNA) for cytologic evaluation of a neck mass is a simple office procedure requiring a few minutes to complete. It can be carried out with ease in children and reduces the necessity to perform excisional biopsy in many cases,
Needle core Biopsy - This is also a fairly simple, well tolerated procedure which can be done on an outpatient basis with mild sedation and local anesthesia. A large size needle is inserted into the tumor site and a small piece of tissue is extracted for histopathological examination. For tumors that are located in deeper parts of the body, the procedure is normally done under indirect visualization of the tumor with CT or ultrasound guidance.
Incisional biopsy - violates the tumor capsule and potentially seeds tumor. Useful when all diagnostic modalities have failed to establish a diagnosis and excisional biopsy of the mass is not feasible.
Excisional biopsy - removal of a suspected tumor mass in its entirety.
If cancerous cells are detected in the biopsied sample a "metastatic workup" is required to find whether the cancer has spread.
Treatment
Surgery is usually the mainstay of treatment for most head and neck tumors. Benign tumors are generally treated with surgery alone. Treatment options for malignant tumors include surgery, radiotherapy, chemotherapy, or a combination of the three. In some cases, surgery is combined with craniofacial reconstructive surgery to obtain a better cosmetic outcome. Distant and loco-regional metastases when found, should be treated accordingly with surgery, radiotherapy or chemotherapy.
Radiation therapy may involve external beam treatment, Gamma Knife or brachytherapy. Radiation therapy is often given in conjunction with surgical treatment, but in some inoperable cases, it is combined with chemotherapy. These multi-modal approaches can often preserve the patient's ability to speak and swallow even in patients with advanced disease.
Rehabilitation therapy is often an integral part of the treatment plan for patients with head and neck cancer and continuous evaluation of each patient's individual needs together with physical and functional rehabilitation provides a means to improve mobility and function following treatment.
Prognosis
Benign neck masses are treated by surgical removal of the primary tumor in its entirety and typically have a good prognosis. For malignant head and neck cancers, early detection and treatment is of utmost importance. Occasionally salvage surgery or salvage radiation therapy are appropriate. Although cure of the cancer is the primary goal in treatment, preserving a patient's appearance and ability to function, and thus his/her quality of life, are also important goals and are considered an integral part of the treatment plan.
Rehabilitation, follow-up care, and post-treatment support are important for maximum functional outcomes following treatment. When found early, recurrent tumors have a better chance of being successfully treated. Follow-up frequency and duration depends on many factors and may last for five years or more
Infratemporal Fossa Tumors
Microsurgical and Endoscopic Access to the Lateral Skull Base
At the Skull Base Institute we have combined traditional techniques such as the infratemporal fossa approach with minimally invasive endoscopic approaches. Through a small hidden preauricular incision , we gain access to the lateral skull base and the infratemporal fossa to resect completely tumors of the infratemporal fossa with minimum discomfort and complications and maximum safety and preservation of vital neurologic and cranial nerve functions.
Many of these patients require neuroradiologic embolisation of their tumors 48 hours prior to surgery and in many occasions they also require a carotid balloon test occlusion. To date we have collaborated with our colleagues in interventional neuroradiology on hundred of such patients who have had their tumors successfully embolized preoperative followed by a surgical resection 48 hours later.
Overview
The Infratemporal Fossa (ITF) is a potential space that lies below the temporal bone and the greater wing of the sphenoid bone; medially it is bound by the lateral pterygoid plate; laterally by the mandibular ramus, zygoma and parotid gland. It extends anteriorly to the posterior wall of the maxillary sinus, and opens inferiorly into the parapharyngeal space.
The ITF communicates with the middle cranial fossa via multiple neurovascular foramina, these include the carotid canal, jugular foramen, foramen spinosum, foramen ovale, and foramen lacerum. It communicates with the orbit via the pterygomaxillary fissure and the inferior orbital fissure.
The ITF comprises the contents of both the parapharyngeal space which include the internal carotid artery (ICA), the internal jugular vein (IJV), cranial nerves IV to XII, the internal maxillary artery (IMA), and the pterygoid muscles and venous plexus.
Any of the structures within or surrounding the ITF may give origin to a tumor and rarely the ITF may also be involved by metastatic tumors.
A host of neoplasms can either arise from or extend into the ITF. Neoplasms found in this region can include paragangliomas (glomus vagale and glomus jugulare), deep lobe parotid tumors such as pleomorphic adenomas, schwannomas, adenoid cystic carcinomas, mucoepidermoid carcinomas, melanomas, hemangiomas, squamous cell carcinomas, rhabdomyosarcomas, myxomas, cholesterol granulomas, angiofibromas, trigeminal neuromas, meningiomas, teratomas, malignant lymphomas, pheochromocytomas, and ameloblastomas.
Causes
There are no known Causes or risk factors associated with the occurrence of ITF tumors. The symptoms occur when these tumors expand causing a mass effect and compressing or infiltrating the adjacent critical neurovascular structures within the ITF. These tumors also often cause bony destruction and thus invade the skull base or they may extend intracranially by following the preexisting anatomical pathways such as the neurovascular foramina.
Symptoms
Tumors of the ITF region typically present as occult neoplasms with usually vague or non-specific symptoms. The majority are asymptomatic in their early phase and symptoms generally occur late and are due to local involvement of the nerves and vessels. Mass effect, cranial nerve compression resulting in symptoms such as facial pain and/or facial numbness, eustachian tube dysfunction and trismus, are common symptoms. A variety of other symptoms may occur depending on the structures affected. Due to the usually subtle nature and insidious onset of symptoms, ITF tumors commonly grow large within the infratemporal fossa before being discovered. The average delay in diagnosis from first symptom is usually between 6-12 months.
Diagnosis
On neurological examination, cranial nerve deficits may be noted especially with larger tumors. Further evaluation requires the identification of the nature, origin, and extent of the tumor. The list of differential diagnosis is wide and includes a host of rare lesions such as myxoma, melanoma, rhabdomyosarcoma, pheochromocytoma, and metastatic lesions.
Computed tomography (CT) scans and magnetic resonance imaging (MRI) are the primary modalities used in the evaluation of location, size and extent of ITF tumors. CT scans are best for evaluating bony destruction and erosion, which is a hallmark of ITF tumors. MRI is usually superior to CT in accurate delineation of the tumor boundaries and in demonstrating any intracranial extension and for evaluating the relationship of the tumor to the adjacent critical neurovascular structures such as the carotid artery and cranial nerves.
Angiography remains valuable in preoperative evaluation of ITF tumors, and the possibility of preoperative embolization. Angiography can confirm the diagnosis and can provide information about the vascular supply of the tumor and the status of the carotid arteries.
Treatment
Surgical removal is the mainstay in the treatment of ITF tumors. However, the management of ITF tumors is complex and the presence of critical neurovascular structures within the ITF limits the exposure of any particular surgical approach. Thus, surgical approaches are designed not only to remove the tumor but also to identify and preserve the complex neurovascular entities of this region. According to the specific type of tumor, some patients may also require adjuvant radiotherapy and/or chemotherapy.
Many surgical approaches have been proposed for the resection of ITF tumors. No single approach is optimal for all tumors. The infratemporal fossa approaches (IFTA) (Types A, B and C), utilize a wide postauricular skin incision to approach ITF tumors. However, the infratemporal approach may provide inadequate exposure of massive tumors of the ITF region and in this case it is used in conjunction with other approaches, such as the transcranial-subtemporal, transmaxillary,transcochlear or anterior transpetrosal approaches.
Prognosis
Although usually histologically benign, ITF tumors are locally destructive, spreading along paths of least resistance and infiltrating critical neurovascular entities. Hence, prognosis is highly influenced by the completeness of surgical resection, the histopathological type of the tumor, and the ability to preserve the critical neurovascular entities within this region.
