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Abstract
We report about a case of a woman in her 50s with a chondrosarcoma of the petrous apex. She has a strabism due to a right-sided amblyopia since childhood and noticed a slowly progressive squint angle in the last months. Her general practitioner (GP) referred her to an ophthalmologist who diagnosed a left abducens paresis and initiated an MRI demonstrating a mass in the left petrous apex. A transnasal endoscopic transsphenoidal biopsy revealed a grade I chondrosarcoma. The patient underwent an endoscopic transsphenoidal anterior petrosectomy approach with complete removal of the tumour. After surgery the squint angle gradually improved to previous levels, so that the patient was able to resume her work. This report demonstrates that even slight changes of a squint angle without diplopia, in this case because of pre-existing amblyopia, could be a hallmark of an intracranial process.
- otolaryngology / ENT
- head and neck surgery
- neurosurgery
- ear, nose and throat/otolaryngology
- neuroopthalmology
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- otolaryngology / ENT
- head and neck surgery
- neurosurgery
- ear, nose and throat/otolaryngology
- neuroopthalmology
Background
Skull base chondrosarcoma are rare, malignant, slow growing tumours, mostly located at the spheno-occipital or spheno-petrosal synchondroses.1 It is thought that chondrosarcoma arises from cells of enchondral cartilage remnants, other theories consider them originating from primitive mesenchymal cells during skull base embryogenesis, and several authors also consider metaplastic fibroblasts as a source.2 According to the WHO classification, the chondrosarcomas are stratified into in grade I (well differentiated), II (intermediate) and III (poorly differentiated) subtypes.3 Skull base chondrosarcomas predominantly develop de novo, an association with the Maffucci and the Ollier-syndrome are known.4 Symptoms depend on the tumour location; headache and diplopia are often reported, occasionally tumours are incidental findings in neuroimaging, and metastatic disease is rare.5 The therapy of skull base chondrosarcoma is surgery with postoperative radiotherapy or protontherapy reserved for high grade or incompletely resected tumours.6
Case presentation
A patient in her 50s was referred from the ophtalmologist to the interdisciplinary skull base clinic for the diagnostic workup and management of a mass located in the left petrous apex. The patient has a pre-existing esotropic strabism and amblyopia of the right eye. Over the last couple of months, she noticed a progressive change of her squint angle. This triggered the further investigations via GP and ophthalmologist who diagnosed a left abducens paresis, subsequent MRI demonstrating the above-mentioned mass (figure 1). The clinical examination demonstrated the left abducens paresis with no other cranial nerve involvement. Diplopia was only present with extreme abduction to the left; in daily life, she did not notice any double vision. The Ear, Nose and Throat Examination was unremarkable. She had a history of strabism correction surgery at the age of 18, otherwise she was healthy with no regular medications.
T2-weighted axial MRI of the brain showing the tumour (blue arrow) and the anteriorly displaced internal carotid artery (red arrowhead).
The further workup with a CT scan of the skull base demonstrated an erosion of the left petrous apex and the left clivus with extension to the left petrous horizontal segment of the internal carotid artery (ICA). A balloon occlusion test of the ICA showed that the ICA if needed could be sacrificed without neurological sequelae. Transnasal endoscopic biopsy was performed, intraoperatively the tumour had a brownish colour, was friable and poorly vascularised (figure 2). The histology revealed a conventional chondrosarcoma WHO grade I (figure 3).
View during transnasal endoscopic biopsy. Tumour (blue arrow), intersinus septum (yellow arrow), bulging internal carotid artery anteriorly displaced in the left sphenoid sinus (red arrowhead).
Histopathology showing low-grade chondrosarcoma (H&E, ×10).
Investigations
Clinical assessment of skull base tumours is difficult due to their localisation deep in the skull. For this reason, reliable imaging techniques are of utmost importance. Usually, CT scans are obtained to assess the bony involvement and to assist planning of the surgical approach. The MRI modality is useful to look at specific tumour characteristics, extension and any signs of infiltration into neighbouring structures or compartments. The distinction between chordoma and chondrosarcoma can be challenging radiologically and histologically, this distinction is however crucial for the management considering the differing treatment strategies of these pathologies. Radiologically chondrosarcoma as well as chordoma demonstrate a T1 hypointensity with T2 hyperintensitiy and variable contrast enhancement, chordoma typically originate from the midline.7 A recent Japanese study showed that apparent diffusion coefficient value ≥1750×10−6 mm2/s were predictive for chondrosarcoma.8 In our patient, the mass exhibited a high signal intensity on T2 and a hypointensitiy on T1 with little contrast enhancement and restricted diffusion. Due to its paramedian location and lateral extension, our radiologists considered the chondrosarcoma as the working diagnosis.
Histologically, chondrosarcomas are divided into mesenchymal, conventional, dedifferentiated and clear cell subtypes. In the skull base, the WHO grade I–II conventional type chondrosarcomas are predominant. In contrast to the chondroma, the chondrosarcoma displays frank bone invasion.5 Chondrosarcomas are positive for S100 staining and most show the IDH1-mutation, importantly they are negative for notochord lineage transcription factor brachyury and for cytokeratin, which clearly differentiates them from chordoma on immunohistochemistry.9 In our case, the morphology showed a chondroid tumour with increased cellularity with positive staining for S100 and negativity for brachyury and cytokeratin thus confirming the diagnosis of grade I chondrosarcoma.
Treatment
After the histological diagnosis was made, an endoscopic transnasal tumour resection under general anaesthesia was performed by multidisciplinary team of otolaryngologists and neurosurgeons. The surgery entailed a creation of a nasoseptal flap for later coverage of the resection site, this was followed by removal of the posterior bony nasal septum and the sphenoidal rostrum with sphenoid sinus floor resection, lateral exposure was achieved by identifying the left vidian nerve and its canal. Subsequent removal of the posterior sphenoid wall revealed the tumour which had moved the cavernous ICA anteriorly. The tumour was removed in a piece meal fashion from medially to laterally up to the horizontal segment of the petrous ICA and posteriorly to the level of the left condyle of the atlas. There was no dural involvement by the tumour, thus complete macroscopic resection could be achieved. The resection site was then obliterated with abdominal fat and covered with the nasoseptal flap.
Outcome and follow-up
There were no postoperative sequelae. The postoperative squint angle gradually reduced to 14 prism dioptries with the left eye abduction improving from 0 to 6 mm. This allowed the patient to return to her normal work. The case was discussed at the sarcoma board which recommended regular 6-monthly MRI as follow-up without any need for adjuvant treatment. One year after surgery, the imaging showed no evidence of recurrence.
Discussion
Chondrosarcomas of the skull base are rare malignant tumours difficult to differentiate from chordomas on imaging and histopathology. So immunohistochemistry plays an important role in differentiating low-grade chondrosarcoma from chordoma and other chondromyxoid rich lesions of the central nervous system such as cystic schwannoma with myxoid degeneration and chondromyxoid fibroma.10
In addition, resection is a challenge, as the lesion is located in a complex anatomical region of the body. To the best of our knowledge, this is the first case of a skull base chondrosarcoma with an abducens palsy in a patient with a severely impaired contralateral vision. Due to the combination of these two clinical conditions, our patient did not experience any double vision.
Because of its long and tortuous course, localisation and affinity to Dorello’s canal, the abducens nerve is at risk in endonasal endoscopic skull base surgery, also in patients with no prior abducens nerve deficits. Clinical presentation of skull base chondrosarcoma can vary depending on the exact localisation and size of the lesion. Lawrence et al11 describe a case of a young man with abducens palsy with double vision as primary symptom, they opted for a combined contralateral endoscopic maxillary and endoscopic endonasal transclival approach for gross total resection of a WHO grade I petroclival chondrosarcoma with cavernous sinus involvement and subsequent postoperative radiation therapy. Banaz et al12 report a case of a middle-aged woman with abducens palsy and headache who had an intermediate grade petroclival chondrosarcoma resected completely through an expanded endoscopic endonasal transclival approach without postoperative radiotherapy. Pamias-Portalatin et al13 outline a case of a 35-year-old woman with diplopia, headache, hemifacial pain with a WHO grade III petroclival chondrosacroma involving superior clinoid ICA, hypoglossal canal, Meckels cave and cavernous sinus. They achieved a near-total resection with an endoscopic contralateral maxillary approach, with postoperative radiotherapy. Chondrosarcoma rarely may also present with acute intracranial pressure elevation. Laghari et al14 report of a 28-year-old man with intraventricular haemorrhage due to a petroclival mesenchymal chondrosarcoma.
Because of its rarity, there are no generally accepted treatment guidelines. Carlson et al6 analysed the data of a retrospective multicentre study including 55 patients with petroclival chondrosarcoma. Overall, 96% underwent surgery, in 27% of those gross total resection was achieved. The majority (64%) of patients were treated with surgery and radiotherapy, in 32% surgery alone was performed. The overall recurrence-free survival after 5 years was 70% for all chondrosarcomas, showing a significant worsening if the tumour size was bigger than 4 cm or if the ICA was encased more than 270° by the tumour. Hasegawa et al15 investigated upfront postoperative radiotherapy versus watchful waiting through serial MRI in 32 patients who underwent surgical resection of a WHO grade I–II chondrosarcoma in the skull base. They found a better short-term to intermediate-term recurrence control with postoperative radiotherapy. They also pointed out the feasibility of close observation in selected cases, due to good local manageability of recurrence without significant morbidity in the watchful waiting group. Simon et al16 found no survival benefit comparing skull base chondrosarcoma WHO grade I–II treated with surgery and postoperative radiotherapy vs surgery alone.
In summary, we report a case of a woman with a petroclival skull base chondrosarcoma WHO grade I presenting with an abducens palsy without noticing double vision due to preexisting amblyopia in the contralateral eye. She underwent an endoscopic endonasal transclival total resection with an uneventful postoperative course. Twelve months after surgery, there was no evidence of recurrence on imaging and she was able to return to work.
Learning points
Even large skull base tumours may induce only discrete symptoms, especially in case of pre-existing cranial nerve damage, or other conditions such as blindness or strabism.
Differentiation between chordoma and chondrosarcoma based on imaging alone is very difficult.
Endoscopic endonasal removal of midline skull base tumours is an elegant method with little morbidity in experienced hands, preferably performed through a multidisciplinary team in a tertiary referral centre.
Ethics statements
Patient consent for publication
Footnotes
Contributors LM was involved in the patient clinical follow-up, concepted and designed the case report, perform literature review and drafted the manuscripte. GR performed the descripted surgery, provided critical review and revision of the manuscript. All authors have read and approved the final version of the manuscript and agree to be accountable for all aspects of the work.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.