- Image Guidance
- CSF Rhinorrhoea & Meningocoele
- Bony Tumour of Skullbase
- Malignant Nasopharyngeal Tumour
- Petrous Apex Lesions
- Anterior Clinoid Mucocoele
- Optic Nerve Decompression
- Schwannoma Around Optic Nerve
- Schwannoma of Infratemporal Fossa
Overview of Endoscopic Skullbase Surgery
The endonasal endoscopic approach has revolutionized the way the tumours involving the central skull base are managed. Large craniotomy (opening of the cranium), brain retraction and cutting through the face are not needed to remove these tumours. The skull base constitutes an anatomical boundary between the fields of neurosurgery and otolaryngology. Collaborative efforts between the otolaryngologists and neurosurgeons have given rise to many transcranial and transfacial skull base approaches to reach pathology in almost any location.
However these open approaches are associated with complications related to prolonged brain retraction, neurovascular manipulation and facial scars. Endoscopes have revolutionized sinus surgery. Better illumination and magnification has helped in improving sinus surgery results. It is only a natural progression of science to go beyond the sinuses to treat the conditions at the skull base by working with the neurosurgeons. It is accurate to call these approaches as maximally invasive with minimal access, because the ultimate goal is to perform a resection as aggressively as with an open approach. Visualization provided by the rigid straight and angled endoscopes can illuminate areas of the skull base that were previously unreachable with standard microscope-based transsphenoidal or transoral approaches. The panoramic view allows visualization, even around corners.
A variety of lesions occur in this region of the skull base. Some of them are purely intracranial. Some of them extend into the nose by eroding the bone or through a pre-existing defect in skull base.
To reach a lesion ventral to the brain, traditionally, after doing a craniotomy (opening of the skull) at the suitable site, brain is retracted. Extent of retraction depends on how deep the lesion is. Excessive and prolonged brain retraction causes oedema and contusion of brain. This neurovascular injury can lead to loss of consciousness and seizure. In endoscopic skull base surgery, the skull base bone, the only structure that is present between the sinus and the tumour is removed. It is nothing but a craniotomy through the nose. Then the tumour is removed without touching the adjacent brain. After removal of the tumour, the defect in the skull base is reconstructed using vascularized pedicled mucosal flap.
Sphenoid sinus is the epicenter of the endoscopic skull base surgery. The anterior cranium can be accessed through removal of the cribriform plate - this is called the transcribriform approach. The middle fossa can be approached through either the transplanum or transsellar routes. The posterior fossa through the transclival method. Lateral recess of sphenoid and infratemporal fossa can be accessed through transpterygoid approach. The same approach is used for nasopharyngectomy also.
The skull base region is packed with very important neurovascular structures. There are normal landmarks to identify these structures. But the normal anatomy of the skull base region is distorted by the tumour. In this scenario, it is very difficult for the surgeon to know the location of these neurovascular structures during the surgery.
Since these structures are at risk of injury, the surgeon becomes less aggressive and may leave behind some of the tumour. Similar to a car or mobile Global Positioning System (GPS), the computer assisted surgical navigation system uses cameras or electromagnetic fields to give the surgeon a three dimensional perception as to where he is operating with respect to the tumour as well as to the adjacent neurovascular structures.These devices allow the surgeon more accuracy and safety in removing disease. This not only improves tumour clearance but also helps to reduce the morbidity.
Craniopharyngiomas are histologically benign (non-cancerous), slow-growing tumours that grow out of embryologic remnants that were misplaced during the formation of the pituitary gland. They occur exclusively in the region of the pituitary gland.
Craniopharyngiomas account for approximately 2 – 3% of all intracranial neoplasms and are most common in childhood and adolescence and they represent 5 – 13% of all brain tumours occurring in children. There is no sexual predisposition. Despite its histologic appearance, craniopharyngiomas may rarely behave like malignant tumours and can metastasize.
Craniopharyngiomas may be intrasellar or suprasellar and may cause various degrees of hypopituitarism by compression of the anterior part of the pituitary gland, pituitary stalk or the hypothalamus. Craniopharyngiomas are uniformly benign and they do not produce hormones. They can be solid, cystic or mixed, they may show various degrees of calcification. Due to their slow-growing characteristics, these tumours can take years to manifest themselves before a diagnosis is made.
The symptoms associated with a craniopharyngioma are related to its location and size. They include symptoms related to an increase in the intracranial pressure (ICP) due to blockage of cerebrospinal fluid (CSF) pathways causing headache, nausea, vomiting and difficulty with balance; and symptoms related to direct pressure they exert on the surrounding neurovascular structures such as decreased vision, particularly peripheral vision due to direct pressure on the optic nerves. They may also cause hormonal manifestations due to pressure on the hypothalamus and pituitary gland causing obesity, excessive thirst and urination (diabetes insipidus), stunted growth and delayed developmental milestones.
Diagnosis :1. A thorough medical history and neurological examination.
2. Magnetic resonance imaging (MRI) and computed tomography (CT) scanning both performed with and without intravenous contrast.
3. An ophthalmological and endocrinological baseline evaluation.
The treatment of choice for craniopharyngiomas is surgical removal. However, radiation therapy (conventional or gamma knife (GK)) may be combined especially in cases of residual tumour following surgery. If possible, radiation is withheld in younger children to prevent their delayed side effects.
In general, the prognosis is good, but it depends on several factors, including the ability of the tumour to be completely removed, and the neurological deficits and hormonal imbalances caused by the tumor at time of treatment.
Esthesioneuroblastoma (ENB), also called olfactory neuroblastoma, is a rare cancer that occurs in the upper part of the nasal cavity. The disease is believed to arise from the cribriform region of the olfactory nerves that carry the sensation of smell from the nose to the brain.
ENB can develop in all age groups. It accounts for 3-5% of all nasal neoplasms. Although it mainly affects Caucasians, but has been reported in all races. The tumour occurs most commonly in teenagers and in the sixth decade of life.
Most patients with ENB present with symptoms of nasal obstruction causing inability to breath through the involved nostril, nose bleed or both. Rarely, may metastasize to other areas of the body.
Further growth of the tumour can be directed laterally within the orbit resulting in symptoms such as proptosis, extraocular movement paralysis, and blindness or superiorly toward the base of the skull producing intracranial symptoms and complications.
Early referral for an intranasal biopsy is key to early diagnosis. A patient with a unilateral nasal obstruction and/or a recurrent epistaxis lasting longer than 1-2 months should be suspected and should undergo a thorough nasal evaluation.
Coronal thin-cut computed tomography (CT) scan is usually the initial radiological study of choice. CT images are essential for correct staging of ENB and should be evaluated carefully for erosion of the cribriform plate, and bone of the skull base.
Magnetic resonance imaging (MRI) is often necessary to better delineate sinonasal, intraorbital or intracranial extension.
The role of an accurate histopathological diagnosis before initiating treatment for ENB is of critical importance. Treatment depends on the tumour stage; the classic treatment strategies for ENB are surgery or radiotherapy or a combination of both. More recently, chemotherapy has been introduced in the therapeutic armamentarium. The optimal treatment sequence varies in each individual case.
Traditionally combined cranio-facial resection is required especially with larger advanced tumours. In this procedure, a skull base surgeon operates through the skull via a craniotomy, while a head and neck surgeon makes the transfacial approach via an incision along the side of the nose (lateral rhinotomy).
Endoscopic endonasal approach has obviated the need for large disfiguring transcranial and transfacial approaches without sacrificing outcomes and with reduced complications.
Olfactory Neuroblastoma – Preoperative MRI Scan
Olfactory Neuroblastoma – Preoperative MRI Scan
Olfactory Neuroblastoma – Postoperative CT Scan
Olfactory Neuroblastoma – Postoperative CT Scan
CSF Rhinorrhoea & Meningocoele
Cerebrospinal fluid (CSF) is a clear, colourless liquid that fills and surrounds the brain and the spinal cord and is contained by the covering of brain (dura). When there is a hole in the dura and skullbase bone, CSF can then leak into the nose and sinuses. Sometimes, the dura herniates through the defect and is known as meningocele. If the defect is large, brain may also herniate through the defect and is known as encephalocoele.
CSF rhinorrhea is rare but can lead to meningitis, which may result in significant morbidity and mortality for the patient.
CSF leaks can happen following head injury, surgery (neurosurgery or sinus surgery) or may occur spontaneously. Traumatic causes include both blunt and penetrating facial injuries. Most spontaneous CSF rhinorrhea are now thought actually to be secondary to elevations in intracranial pressure (ICP). Congenital skull base defects and certain tumors can also lead to CSF rhinorrhea.
The typical history of a cerebropsinal fluid (CSF) leak is that of clear, watery discharge, usually unilateral(Fig.1). However if fluid drains into the back of the throat there may be a salty taste. Drainage also tends to increase when bending over or straining.Diagnosis is made more easily in patients with recent trauma or surgery than in others. Patients with recurrent meningitis should be evaluated for a skull base defect regardless of the presence or absence of CSF rhinorrhea. Patients with herniation of dura and/or brain can have nasal obstruction. Chemical analysis of the nasal fluid for glucose and protein but is unreliable. Beta2-transferrin is located only within the CSF, perilymph, and aqueous humor. This is currently single best laboratory test for identifying the presence of CSF in sinonasal fluid.
High-resolution CT scanning is the imaging modality of choice for identifying a skull base defect associated with CSF rhinorrhea. Injection of intrathecal contrast improves localization of the site of the CSF leak in most patients with active leak. Patients with intermittent CSF rhinorrhea may have false-negative CT cisternograms. Another disadvantage of this technique is that it may miss cribriform or ethmoid sinus defects.MRI typically is not recommended as a first-line imaging modality in the evaluation of CSF rhinorrhea unless an encephalocele is demonstrated on examination or is suspected. Unlike CT imaging, MRI does not delineate well bony defects within the anterior or middle cranial fossa.
As traumatic leaks stop spontaneously in the majority of cases, conservative measures (bed rest, stool softeners, and lumbar drainage) are taken for a period of 7 days.However, if CSF rhinorrhea persists beyond this point, or if a large skull base defect is observed at the time of injury, surgical repair is warranted. Surgical repair is recommended in all patients with spontaneous or iatrogenic CSF rhinorrhea in order to prevent ascending meningitis.If an iatrogenic leak is detected intraoperatively, it should be repaired at the time of the original surgery. As only one third of spontaneous leaks stop spontaneously and intermittent leakage over several years is characteristic, surgery is the only option.
Traditionally, a large skull opening was required to see the site of the leak after lifting up the frontal lobe of the brain.Disadvantages of the intracranial approach include increased morbidity, loss of smell, and trauma related to brain retraction, including seizures, edema, and hemorrhage. Failure rate for this approach is 40%.
Now, with minimally invasive endoscopic techniques, the site of the fluid leak can be approached through the nose and fixed, without opening up the skull or touching the brain.Endoscopic repair has now become the preferred method of controlling CSF rhinorrhea, with the high success rate of 90-95%. It avoids the morbidity associated with the open craniotomy approach.It has several advantages, including enhanced illumination and magnified as well as angled visualization. Another advantage is the ability to more accurately position the grafts(Fig.2). If the CSF pressure is high, to prevent recurrence, lumbo-peritoneal shunt is done.
Chordomas are tumours originating from embryonic remnants of the primitive notochord which is a flexible rod-like structure present in the human embryo from which the spinal column develops. The notochord usually disappears almost entirely shortly after birth, the cells that give origin to chordoma are left over notochordal cells. It may affect the axial skeleton anywhere from the coccyx to the base of the skull, in either the midline or paramedian position.
There are three histological subtypes of chordoma: conventional (sometimes called classic), chondroid, and dedifferentiated. Chondroid chordomas tend to be less aggressive than conventional chordomas, while dedifferentiated chordomas are more aggressive, faster growing and more likely to metastasize.
Chordomas of the skull base are particularly debilitating due to the involvement of local structures. The most common signs of chordoma are pain and neurological changes. Most often cause headache, double vision, or gait disturbance.
Imaging studies. True diagnosis of chordoma can only be made pathologically.
Olfactory neuroblastoma – Preoperative MRI scan
Olfactory neuroblastoma – Preoperative MRI scan
Currently, surgery is the first-line treatment for chordomas. Complete resection during the first surgery provides the best chances for local control and long-term survival. Using the endoscopic, endonasal technique small, midline tumours can removed without performing a large cranial opening. In addition, larger tumours can be debulked in preparation for radiation therapy with minimal morbidity and rapid recovery time. Surgical goals involve as complete a removal of the grossly identified tumour as possible. The role of adjuvant radiotherapy thereafter is still subject to debate.
Chordomas should be treated aggressively especially in younger since failure to do so will result in a locally aggressive behavior that can result in numerous cranial nerve deficits including blindness.
Prognosis and Survival :
Chordomas are malignant and potentially life threatening tumours. Advances in surgery, radiation and imaging techniques in the past two decades have increased survival rates and improved chances of a cure.
The overall survival rates are 68% at 5 years and 40% at 10 years. Complete surgical resection offers the best chance for long-term survival. In many cases, radiation therapy can also increase local control rates and prolong survival.
Even after surgery and/or radiation, chordomas tend to return locally - in the same location or in the areas around the original tumour. Many patients undergo multiple surgeries over several years to treat local recurrences. Distant metastasis (spreading to other body parts) occurs in 20-40% of patients with chordomas of the spine and less than 10% of patients with skull-base tumours. The most common sites of distant metastasis are the lungs, liver, bones, and skin.
Bony Tumour of Skullbase
Bony lesions of the skull base are a rare group of heterogeneous disorders. Clinical manifestation of these disorders often results from compression of the cranial nerves in the foramina at the skull base (optic nerve is most commonly affected), displacement of the eye and obstructing the nasal passage and sinuses.
Osteomas are relatively rare, slow-growing tumours. Most commonly they are found within the frontal and ethmoid sinuses. These tumours are slow growing and usually cause no symptoms. Small, asymptomatic lesions do not need surgery. Extension to the orbit and/or skull base is unusual. When osteomas expand, they give rise to symptoms by blocking the sinuses, like headache, and ocular symptoms, such as diplopia, exophthalmos and proptosis. On imaging, they tend to show a range of variable bone density, from very dense and sclerotic for ivory-type osteoma to less dense and less ossified for fibrous osteoma.
Surgery is the treatment of choice for symptomatic osteomas. However, the approach depends on the extension and the occurrence of complications. Traditional surgical approaches to the involved sinuses cut through the facial skin (external frontoethmoidectomy, lateral rhinotomy or osteoplastic flap technique). Endoscopic transnasal resection is ideal for tumours confined to the ethmoid and nasal cavity. The main advantages of the method are the minimal soft tissue dissection, the absence of facial bony disruption, and the avoidance of a facial incision. The magnification and the different angled view, which are possible with the use of endoscopes, may facilitate the removal of osteoma, with minimal morbidity. However, when osteomas are large and expanded in to the orbit and anterior cranial base, a combination of external and endoscopic technique are required, due to the limited access and visibility of endoscopy.
Osteoma - ethmoid; preoperative CT scan
Osteoma - ethmoid; postoperative CT scan
Fibrous dysplasia is an idiopathic, non-hereditary, progressive skeletal disorder in which the bone in localized areas being replaced by fibrous tissue resulting in expanded, softened, and fragile bone. It is established early in life and the activity continues until skeletal growth ceases. The most common bones affected by this disease are the skull and facial bones. Disease can present as monostotic fibrous dysplasia (affects only one bone), polyostotic fibrous dysplasia (involves multiple bones), or as McCune-Albright syndrome (polyostotic fibrous dysplasia with skin pigmentation and precocious puberty).
Fibrous dysplasia widens the medullary cavity, leaving the cortex intact. As a result, encroachment on the neurovascular foramina and paranasal sinus openings is often seen. CT is best for imaging and shows the inhomogeneous mixture of bone and fibrous tissue referred to as a “ground glass’’ appearance. A thin intact cortical rim is seen over the margins of the involved bones.
It is first detected in young children where it manifests as a swelling of the jaw. Involvement of the frontal and/or facial bones can eventually lead to deformation of facial features and skull shape, along with pain. When one or more bones progressively increase in size, they encroach on the cavities of the orbit, mouth the nose and sinuses. Abnormal protrusion of the eyeball (exophthalmos) may develop and eventually causes complete loss of sight due to compression of the optic nerve. There may also be interference of the nasal passage and with eating.
Asymptomatic lesions can be observed. Surgery is usually delayed until adolescence, however if the progression of the disease compromises neurological function, a decompressive procedure should be considered early in childhood to preserve normal function. Curative treatment for fibrous dysplasia involves complete removal of the affected bone. To preserve sight, surgery for optic nerve decompression is needed in cases where the fibrous dysplasia has deformed the optic canal. Some lesions are amenable to resection for a cure by a single procedure. More often, most lesions can be managed through staged procedures.
The endoscopic approach allows surgeons using the nose and nasal cavities to reach fibrous dysplasias that were once considered inoperable or hard to reach. It has the advantage of no facial scar or disfigurement to the patient, and a shorter recovery time.
Ossifying fibroma is a neoplastic process affecting the bones of the skull. There is still confusion as to the distinctiveness of this disease, and these lesions have often been mislabeled as fibrous dysplasia, cementifying fibroma and fibrous osteoma. The distinct histological finding is the presence of osteoblasts and lamellar bone (fibrous dysplasia has woven bone with dysplastic bony spicules without osteoblasts). Head and neck lesions are most often in the mandible and maxilla, with rare occurrences reported in the paranasal and sphenoid bones and occasionally in the orbit. They tend to occur in the third and fourth decades, with the younger patients noted to have a more aggressive (faster growing) lesion.
Osteopetrosis is a diffuse disease in which skeletal sclerosis is formed by thickening of both the cortical and the spongy bone and was known as marble bone disease. Most often patients present with deficits of cranial nerve (CN) II, VII and VIII. Blindness from optic nerve compression is almost exclusively associated with the juvenile autosomal recessive form of this disease.
CT scan shows ossifying fibroma
Juvenile Nasopharyngeal Angiofibroma (JNA)
JNA is a benign but locally aggressive vascular tumor that grows in the back of the nasal cavity. It most commonly affects adolescent males.Onset is most commonly in the second decade; the range is 7-19 years. JNA is rare in patients older than 25 years.
The tumor starts adjacent to the sphenopalatine foramen. They initially fill the nasal cavity and nasopharynx. The tumour can extend superiorly towards the sphenoid sinus. The cavernous sinus may become invaded if the tumor advances further.Laterally, the tumour extends through thepterygopalatine fossa, bowing the posterior wall of the maxillary sinus, into the infratemporal fossa. Extending through the orbital fissures can cause proptosis and optic nerve atrophy.
Patients Usually Present with1. Frequent unprovoked profuse nasal bleed
2. Nasal obstruction and nasal discharge
3. Facial swelling
4. Conductive hearing loss from eustachian-tube obstruction
5. Double vision, which occurs secondary to erosion into superior orbital fissure and due to third and sixth nerve palsy,
6. Protrusion of eye when the tumour extends into the orbit
CT as well as MRI is done to know the extent of this highly vascular tumour. Biopsy should be avoided as to avoid extensive bleeding since the tumor is composed of blood vessels without a muscular coat. To reduce the blood loss during surgery, angiography is done to block the artery that supplies blood to the tumourand is known as embolization(Fig. 1 & 2).
Selective angiogram of sphenopalatine artery shows the vascularity of the tumour
Selective angiogram of sphenopalatine artery shows complete occlusion of tumour blood vessels.
Treatment for Nasopharyngeal angiofibroma (JNA) is primarily surgical. In the past, tumour was exposed through the mouth or by making incisions in the face (transpalatal, lateral rhinotomy,transmaxillary, maxillary swing and mid-face degloving approaches). Currently, advanced endoscopic sinus surgery techniques have been used successfully to remove these tumours. Considerable surgical experience is required to successfully perform the endoscopic operation.Radiotherapy is reserved for intracranial disease or recurrent cases.
Cancer of Nasopharynx
The nasopharynx is the air passageway at the upper part of the pharynx (throat) behind the nose and lies just above the soft palate(Fig.1). The nostrils lead through the nasal cavity into the nasopharynx.An opening on each side of the nasopharynx (called the Eustachian tube opening) leads into the middle ear on each side. Inferiorly, it communicates with the oropharynx (part of pharynx behind the oral cavity).
Several types of tumours can develop in the nasopharynx. Some of these tumours are benign (non-cancerous), but others are malignant (cancerous). Several types of benign tumours, including angiofibromas, hemangiomas and tumours in the lining of the nasopharynx that include the minor salivary glands.
The nasopharynx contains several types of tissue, and each contains several types of cells. Different cancers can develop in each kind of cell. The differences are important because they determine the seriousness of the cancer and the type of treatment needed. Squamous cell carcinoma (nasopharyngeal carcinoma - NPC) is the most common malignant tumour of the nasopharynx. Other nasopharyngeal cancers include adenoid cystic and mucoepidermoid carcinomas, malignant mixed tumours, adenocarcinomas, lymphomas, fibrosarcomas, osteosarcomas, chondrosarcomas, and melanomas.
NPC is one of the most common cancers among people of Chinese, especially Southern Chinese, and Southeast Asian ancestry, including Chinese immigrants to North America. Over several generations, the prevalence among Chinese-Americans gradually decreases to that among non-Chinese Americans, suggesting an environmental component to etiology. Dietary exposure to nitrites and salted fish also is thought to increase risk. Epstein-Barr virus is a significant risk factor, and there is hereditary predisposition.
1. Nasal obstruction
2. Hearing loss due to a middle ear effusion (eustachian tube obstruction)
3. Purulent bloody nasal discharge
4. Frank epistaxis
5. Cervical lymphadenopathy
6. Pain in the side of the head (due to involvement of fifth cranial nerve)
7. Blurred or double vision (3rd, 4th, and 6th cranial nerve palsies)
These symptoms may be caused by other conditions also. Therefore, there is always a big delay between the onset of symptoms and final diagnosis. As a result, most patients usually present at late stages.
Anyone with such symptoms requires careful evaluation and examination with a nasopharyngeal mirror or endoscope, and lesions are biopsied. Open cervical node biopsy should not be done as the initial procedure, although a needle biopsy is acceptable and often recommended. Gadolinium-enhanced MRI (with fat suppression) of the head with attention to the nasopharynx and skull base is done; the skull base is involved in about 25% of patients. CT also is required to accurately assess skull base bony changes, which are less visible on MRI. A PET scan also commonly is done to assess the extent of disease as well as the cervical lymphatics.
Primary treatment of NPC is concomitant chemoradiotherapy, in which chemotherapy is given in combination with radiation therapy. Patients achieve quite satisfactory cure rate. About one third of the patients fail locally in the nasopharynx. Up until recently there were no good treatment options available other than re-irradiation.
Re-irradiation improves survival in less than 30% of patients but associated with high incidence of complications like temporal lobe necrosis, trismus, deafness, endocrine dysfunction and osteoradionecrosis causing severe pain, foul odour and massive bleeding. Even though the incidence of complications has come down with intensity modulated radiotherapy (IMRT), the cure rate remains the same.
Surgery improves survival in more than 50% in these lesions with minimal morbidity. Todays evidence favours surgery in these recurrent or residual tumours.
Removing the tumour (Nasopharyngectomy).
For long, nasopharynx was considered unresectable because of its central location and was surrounded by uninvolved bony structures. Access to the nasopharynx has been pioneered by many surgeons in the last three decades using various open techniques e.g.,. Trans temporal approach by UgoFischin 1983. William Wei in 1989 translocated the upper jaw bone (facial translocation or maxillary swing) to expose this region well for an en-bloc resection. Paul Donald described the Transfacial Subcranial approach for nasopharyngectomy. This has doubled the 5-year survival in patients with recurrent disease.
With newer endoscopic surgical techniques, surgeons can completely remove some nasopharyngeal tumours, but this is appropriate only for a small tumours. Factors determining the surgical approach are the extent of tumourand the structures involved. For planning the surgery, we should know whether the tumour is limited to nasopharynx or spread to infratemporal fossa or involving theinternal carotid artery or intracranial extension.
Nasopharyngectomy is indicated as a salvage procedure in persistent or recurrent nasopharyngeal carcinoma. But it is done as a primary treatment in radioresistent tumours like adenocarcinomas, minor salivary gland tumours and sarcomas. These complex procedures are done only in specialized centers.
Removing lymph nodes :
Cancers of the nasopharynx often spread to the lymph nodes in the neck. These cancers often respond well to treatment with radiation therapy (and sometimes chemotherapy). But if some cancer remains after these treatments, an operation called a neck dissection may be needed to remove these lymph nodes.
Questions Patients should ask before deciding about the treatment:
1. What type of nasopharyngeal cancer do I have?
2. What is the stage of the cancer? What does this mean?
3. What are the treatment options?
4. What treatment option do you recommend?
5. Should I get an additional consultation or second opinion?
6. What can be done to relieve the possible side effects?
7. If surgery is needed, will it be necessary to have reconstruction done to replace lost tissue ?
8. If surgery is needed, will there be a need for a neck dissection (removing lymph nodes)? If so, what type of dissection will be done? What does this mean?
9. What are the possible side effects of this treatment, both in the short term and the long term?
10. When can I expect to recover from the treatment effects?
11. What follow-up tests will be needed, and how often will I need them?
12. Will there be any lasting or late side effects that will need special care?
Petrous Apex Lesions
Petrous bone is part of the temporal bone. It is pyramidal in shape and is wedged between the greater wing of sphenoid and basiocciput(Fig). The inner ear (cochlea & labyrinth) is within the petrous bone. The tip of the pyramidal bone (medial to cochlea and internal auditory canal) is filled with marrow and is pneumatized in 33%. Pneumatization (presence of air spaces within the bone) of the petrous apex results from extension of air cells from mastoid around the labyrinth to the petrous apex. This provides direct pathways for disease to spread from the mastoid bone or middle ear to the petrous apex. Pneumatization is asymmetric in 5%–10% of individuals.
Selective angiogram of sphenopalatine artery shows the vascularity of the tumour
The apex of the petrous bone lies in a complex anatomic region that contains a number of critical neural and vascular structures. Therefore, lesions arising in or spreading to the petrous apex cause varied and occasionally severe clinical sequelae, which typically are the result of mass effect or direct invasion of the cranial nerves, brainstem, or internal carotid artery (ICA).
A variety of pathology occurs at petrous apex. Before the advent of antibiotics, infections of the petrous apexwas common and progressed to meningitis, brain abscess and death. Since the introduction of antibiotics, the prevalence of such serious complications has been drastically reduced.Eventhough rare, the most common pathology encountered at present is cholesterol granuloma and it forms 60% of all lesions in this area. Other lesions seen in this area are congenital cholesteatoma, mucocoele, encephalocoele and tumours like meningioma, schwannoma. Chondrosarcoma and chordoma.
The diagnosis usually isn’t based on a biopsy, because it’s so hard to get to. It’s in the middle of the head. So we do rely a lot on imaging.
Management of petrous apex pathology poses a unique challenge even to the most experienced skull base surgeons. The central location in the skull base with adjacent critical neurovascular structures makes access to this region more than a trivial matter.
The introduction of modern skull base surgery techniques also has provided skull base surgeons with numerous avenues to the petrous apex while significantly decreasing morbidity.
Solid tumors/cholesteatoma removed when first identified, rather than after symptoms develop. Establish outflow drainiage pathway that is maintained so that cholesterol granuloma expansion does not result in recurrence of patient’s symptoms. Small cystic lesions can be observed with periodic MRI to assess the growth. Delaying surgery in presence of symptoms offers no real advantage.
We need to consider the following before choosing the surgical approach.1. Patient’s hearing level
2. Drainage of a cyst or excision of a tumour
3. Pneumatization of the temporal bone and sphenoid
If the sphenoid sinus is well pneumatized and is abutting the petrous apex, the petrous apex can be approached through the nose using endoscope. It gives wide drainage pathway and is done without retracting the brain. This is the treatment of choice.
If it is extension of infection from mastoid, petrous apex can be drained through the air cell tract underneath or infront of cochlea.
If the petrous apex lesion is not projecting into the sphenoid sinus, the middle cranial fossa approach / infratemporal approach / transcochlear approach may be used in resecting tumours or tumour-like conditions.
Basilar invagination is an uncommon condition that occurs when the upper portion of the second vertebra (C2) moves upward. This may cause compression of the spinal cord and brainstem, creating a variety of neurological problems, including sudden death. This condition may be present at birth; may occur as the result of an accident; or may occur in patients with bone diseases such as rheumatoid arthritis.
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Patients may have headache, dizziness, confusion, swallowing problems, numbness/tingling in the extremities and paralysis. Symptoms can become worse with flexion of the head, which causes further drapes the brainstem and/or spinal cord by the odontoid process.
Basilar invagination can be diagnosed by imaging studies such as head X-rays, CT and MRI scans.
Non-surgical treatment for basilar invagination that is not compressing the spinal cord may include physical therapy, non-steroidal anti-inflammatory medication, or a cervical collar.
Traditionally, odontoidectomy has been done through the mouth after splitting the soft palate. Traversing the oral cavity increases the risk of infection. To prevent this oral feeding is withheld for a week after surgery. Splitting the soft palate can cause nasal regurgitation and can affect phonation.
Most patients will subsequently need posterior cranio-cervical fusion to prevent recurrence and to stabilize the joints.
If surgery is needed, the odontoid and clivus can be approached through the nose using an endoscope to decompress the brainstem and spinal cord.
Anterior Clinoid Mucocoele
Fig.1 40 yrs old lady presented with deterioration of vision in right eye. Coronal MRI shows mucocoele of anterior clinoid process (green arrow) laterl to optic nerves(yellow arrows).
Fig.2 Axial MRI shows the mucocoele of anterior clinoid process (green arrow) lateral to optic nerve (yellow arrow).
Fig.3 Diagram shows pneumatization of anterior clinoid process through lateral opticocarotid recess (black arrow).
Ant Clinoid Mucocoele 1min 30sec
Optic Nerve Decompression
Optic Nerve Decompression
Schwannoma Around Optic Nerve
Schwannoma Around Optic Nerve
Schwannoma of Infratemporal Fossa
Fig.1 Coronal MRI shows tumour in infratemporal fossa, reaching skull base superiorly. Inferiorly, above the level of palate.
Fig.2 Sagittal MRI shows the mass in ITF reaching skull base. Thickened mandibular nerve is seen.