Anteriorly placed meningiomas at the level of the foramen magnum are rare, are difficult to diagnose, and present technical problems for a conventional posterior fossa removal.
Previously, the transoral approach garnered interest only from a historical point of view, but with technical progress it has acquired a “second life”. Novel surgical techniques allow for a more radical resection of named tumors, as well as lower morbidity and invasiveness of the surgical procedures, which, in the long term, leads to lower complication rates 1).
Miller and Crockard in 1987 described the successful transoral transclival excision of two such tumors. Cerebrospinal fluid fistula can be avoided by dural repair using a fibrin glue and long term CSF diversion. This modification enables the transoral route to be considered for anteriorly placed intradural lesions 2).
Uchibori et al., in 1990 published a 50-year old woman with a giant parapharyngeal meningioma extending from the intracranial.
The parapharyngeal tumor was biopsied using the transoral approach and a histological section diagnosis suggested meningioma. Thereafter, further examination by magnetic resonance images (MRI) and contrast enhanced CT scans revealed a diffuse meningioma en plaque in the posterior fossa. Invasion extended from the clival dura to the right sigmoid sinus. The extracranial extension of a meningioma is very rare but a few cases have been reported. In almost all of the reported cases, a large intracranial meningioma was simultaneously or previously verified by CT scans.
This case was special in that the intracranial mass was not voluminous but showed en plaque extension, and also because the pathway of the extracranial extension through the jugular foramen was clearly visualized by CT and MRI. Obliteration and invasion of the right sigmoid sinus and the internal jugular vein by tumor were also demonstrated 3).
Kondoh et al., presented three cases of foramen magnum meningioma. The first involved a ventral type tumor extending to the second cervical body. Following bilateral mandibulotomy, surgery was performed via the anterior transoral approach and the tumor was totally removed. Nine days postoperatively, she developed meningitis, which was successfully treated with antibiotics. The second patient’s tumor was dorsal type and was deeply embedded in the lateral part of the vermis. The tumor was totally removed via the midline suboccipital approach and she recovered uneventfully, with only slight upper-extremity paresthesia. In the third case, the tumor was ventral type and situated mainly in the clivus. Craniotomywas performed by the bilateral suboccipital approach and extended nearly to the jugular tubercle. The tumor, which severely displaced the lower cranial and upper cervical nerves, was totally removed. The postoperative course was lengthy and complicated. Artificial ventilation was required for 2 months, and difficulty in swallowing persisted during long-term follow-up. As illustrated by the second case, dorsal and lateral type foramen magnum meningiomas can usually be removed via the lateral suboccipital approach. In the case of ventral type tumors, the anterior transoral approach entails the risk of infection, as occurred in the first case. They conclude that the lateral suboccipital approach is preferable; craniotomy extending to the jugular tubercle lowers the risk of brainstem damage 4).
Bonkowski et al., published a case of meningioma situated at the anterior rim of the foramen magnum with successful removal via a transoral approach is reported. A new technique of preventing cerebrospinal fluid leakage is described utilizing fascia lata and a bone baffle without any attempt to close the dura, either by primary suture or tissue sealants 5).
In 2001 Imamura et al., reported a 66-year-old female complaining of occipitalgia and numbness of the extremities who had a foramen magnum meningioma. She wastreated via the transoral transclival route with a protective bone baffle, obtained from the iliac bone, securely fixed in the bone window to protect the repaired dura from injury by CSF pulse energy. The patient dont showed CSF leakage or meningitis, and the period of continuous lumbar CSF drainage was only 7 days 6).
An et al., presented two clinical cases in which transoral approach was used to treat ventral meningiomas of the craniovertebral junction. Endoscopic assistance and an original method of anterior atlantooccipital stabilization were used.
Subtotal removal in the first case and complete removal of the tumor in the second case were achieved. In the first case, an unsuccessful attempt of anterior stabilization was made. In the second case, there were no indications for instrumentation (anterior or posterior) as local bone autograft fusion between the condyles and lateral masses of C1 was effectively carried out.
Previously, the transoral approach garnered interest only from a historical point of view, but with technical progress it has acquired a “second life”. Novel surgical techniques allow for a more radical resection of named tumors, as well as lower morbidity and invasiveness of the surgical procedures, which, in the long term, leads to lower complication rates 7).