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Chordomas are the tumors commonly involving base of skull which are predominantly solid in consistency. A cystic chordoma of the cavernous sinus is an extremely rare entity and has never been reported. We report a 26-year-old male presenting with gradually progressive right-sided sixth nerve palsy and headache. Computed tomography and magnetic resonance imaging of the brain showed a cystic lesion in the right cavernous sinus. The patient was successfully treated using a transnasal endoscopic transsphenoidal approach. Histopathological examination of the lesion revealed chordoma. Our case is the first report of such a condition. Chordoma should be considered in the differential diagnosis of cystic lesions in the parasellar location. We briefly review the radiology, the pathology and management dilemmas of such lesions.

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OBJECTIVE: The authors evaluate the significance of atlantoaxial instability in the management of idiopathic syringomyelia. BACKGROUND: We recently observed that atlantoaxial dislocation can be present even when the atlantodental interval was within normal range. Atlantoaxial instability can be identified on the basis of facetal mal-alignment or even by direct observation of status of joint during surgery. Our observations are discussed in nine patients where we identified and treated atlantoaxial instability in cases that would otherwise be considered as having "idiopathic" syrinx. MATERIALS AND METHODS: The authors report experience with nine cases that were diagnosed to have "idiopathic" syrinx. The main bulk of the syrinx was located in the cervico-dorsal spinal region in all cases. One patient had been treated earlier by syringo-subarachnoid shunt surgery and one patient had undergone foramen magnum decompression. RESULTS: On radiological evaluation, eight patients had posterior atlantoaxial facetal (Type B) dislocation. In one patient there was no facetal mal-alignment and was labeled to have axial or central (Type C) facetal instability. All patients were treated by atlantoaxial fixation. All patients improved symptomatically in the immediate postoperative period and the improvement was progressive and sustained on follow-up. In one case, the size of syrinx reduced in the immediate postoperative imaging. In the period of follow-up (range 6-42 months - average 19 months), reduction in the size of syrinx was demonstrated on imaging in three cases. CONCLUSIONS: The positive clinical outcome suggests that atlantoaxial instability may be the defining phenomenon in development of previously considered "idiopathic" syringomyelia.

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BACKGROUND: We discuss the rationale of surgical treatment of group B basilar invagination by atlantoaxial facet joint stabilization and segmental arthrodesis. METHODS: From January 2010 to April 2016, 63 patients with group B basilar invagination were surgically treated. All patients had varying degree of myelopathy-related functional disability. Fifty-two patients had both Chiari malformation and syringomyelia. All patients were treated by atlantoaxial plate and screw fixation with the techniques described by us in 1994 and 2004. Foramen magnum decompression or syrinx manipulation was not carried out in any patient. Occipital bone and subaxial spinal elements were not included in the fixation construct. RESULTS: Three patients died in the immediate postoperative phase. In the remaining patients, there was clinical improvement and no patient's neurologic function worsened after surgery. In 12 of 38 patients in whom postoperative magnetic resonance imaging was possible, at a follow-up of at least 3 months, there was reduction in the size of the syrinx. CONCLUSIONS: The pathogenesis of basilar invagination in group B is related to atlantoaxial instability. The clinical outcome suggests that the surgical treatment in these cases should be directed toward atlantoaxial stabilization and aimed at segmental arthrodesis. Inclusion of the occipital bone in the fixation construct is not necessary. Foramen magnum decompression and procedures involving manipulation of Chiari malformation and syringomyelia are not necessary.

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BACKGROUND: We evaluated the radiologic features of 75 patients with group B basilar invagination who exhibited no evidence of atlantoaxial instability based on the conventional parameter of an abnormal increase in the atlantodental interval. We specifically studied the variability and possible significance of the presence of cerebrospinal fluid (CSF) within and outside the confines of neural tissues. MATERIALS AND METHODS: During the period January 2008-May 2015, we encountered 75 cases with group B basilar invagination. These patients were divided into 4 groups depending on cervical spinal imaging that showed the presence of syringomyelia (group B1), increased CSF volume in the extramedullary space or external syrinx (group B2), the presence of both syringomyelia and external syrinx (group B3), and no abnormality of CSF cavitation in the spinal canal (group B4). RESULTS: Our cohort comprised 39 group B1 cases, 10 group B2 cases, 20 group B3 cases, and 6 group B4 cases. The neck size and posterior fossa height were simultaneously reduced, by 15.89% and 15%, respectively, but the length of the neural structures remained within the normal range. Excessive amounts of CSF were present within or outside the confines of neural structures, including the spinal cord, brainstem, and cerebellum. CONCLUSIONS: In cases of basilar invagination, various musculoskeletal and neural alterations seem to have a common functional role in protecting the craniocervical cord and delaying or stalling neurologic dysfunction.

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Complex craniovertebral junctional anomalies can be daunting to treat surgically, and preoperative information regarding the osseous abnormalities, course of the vertebral arteries, size of the pedicles, and location of the transverse foramina is invaluable to surgeons operating on these challenging cases. The authors present their experience with the emerging technology of 3D model acquisition for surgery in 11 cases of complex craniovertebral junction region anomalies. For each case, a 3D printed model was made from thin CT scans using a 64-slice CT scanner. The inclination of the joints, the presence of false articulations, the size of the pedicles, and the course of the vertebral arteries were studied preoperatively on the 3D models. The sizes of the plates and screws to be used and the angle of insertion of the screws were calculated based on the data from the models. The model was scaled to actual size and was kept beside the operating surgeon in its anatomical position during surgery. The potential uses of the models and their advantages over conventional radiological investigations are discussed. The authors conclude that 3D models can be an invaluable aid during surgery for complex craniovertebral junction anomalies. The information available from a real life-size model supersedes the information available from 3D CT reconstructions and can also be superior to virtual simulation. The models are both cost effective and easy to build and the authors suggest that they may form the basis of investigations in the near future for craniovertebral junction surgery.

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A 22-year-old female, a known case of neurofibromatosis 1 (NF1), presented with a congenital swelling in the left occipital region. She had developed recent onset dysphagia and localized occipital headache. Neuroradiology revealed a left occipital meningoencephalocele and a left parapharyngeal meningocele. This was associated with ventriculomegaly. She was advised on cranioplasty along with duraplasty which she denied. She agreed to a lumbar-peritoneal shunt. She described a dramatic improvement in her symptoms following the lumbar-peritoneal shunt. Occipital dysplasias, though uncommon, have been reported in the literature. We review this case and its management and discuss relevant literature on occipital dysplasias in NF1.

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A 52-year-old female presented with frequent episodes of falls without loss of consciousness. These episodes lasted for brief period followed by full neurological recovery. Magnetic resonance imaging (MRI) of the brain showed foramen magnum meningioma encasing left vertebral artery. The patient had dramatic improvement after excision of the tumor.