Atlantoaxial Fixation for Treatment of Chiari Formation and Syringomyelia with No Craniovertebral Bone Anomaly: Report of an Experience with 57 Cases.

AIM: In this paper we evaluate the role of atlantoaxial instability in the pathogenesis of Chiari formation type I and the role of atlantoaxial stabilization for treatment of this condition in cases with no obvious bone malformation in the region of the craniovertebral junction. MATERIALS, METHODS AND RESULTS: During the period from January 2010 to July 2016, we identified 57 cases of Chiari formation where there was no bone malformation or evidence of craniovertebral junction instability that could be diagnosed on the basis of an abnormal increase in the atlantodental interval on dynamic imaging. Forty-eight of these patients had syringomyelia. The average duration of follow-up was 42 months. There were 30 males and 27 females in the series. The ages of the patients ranged from 4 to 57 years. The Japanese Orthopaedic Association (JOA), visual analogue scale (VAS) and Goel clinical grading systems were used to assess the patients' clinical status. Atlantoaxial instability was diagnosed on the basis of vertical mobility of the odontoid process on dynamic radiographs, facetal malalignment on imaging or direct bone handling during the surgical procedure. Surgical treatment was achieved using atlantoaxial fixation. Foramen magnum decompression or syrinx manipulation was not done. All patients had immediate postoperative and sustained clinical symptomatic recovery. A reduction in the size of the syrinx was observed in ten patients and regression of tonsillar herniation was observed in 12 of 23 cases in which postoperative magnetic resonance imaging (MRI) was possible. CONCLUSION: Atlantoaxial instability is the prime factor in the genesis of Chiari formation even when there is no bone abnormality in the craniovertebral junction.

Olfactory groove meningiomas: An analysis based on surgical experience with 129 cases.

OBJECTIVE: The surgical strategy and outcome for 129 patients operated for an olfactory groove meningioma is retrospectively analyzed. MATERIAL AND METHODS: One hundred and twenty nine patients with an olfactory groove meningioma operated between the years 1987 and 2016 were analyzed on the basis of clinical and radiological factors that appeared to affect the conduct of surgery and its outcome. Each factor was given points, and the points were added to obtain a score. On the basis of the score, the tumors were divided into three grades. The grades determined the difficulties that could be anticipated during surgery. In the initial part of the series, a bifrontal craniotomy was done to resect the tumor in all patients. In the later half of the series, majority of the patients were operated by the use of a unifrontal craniotomy. The aim of surgery was to resect the tumor completely. RESULTS: Total tumor resection was achieved in 86 patients, and subtotal tumor resection with less than 10% tumor left behind was achieved in 43 patients. Seven patients died in the immediate postoperative period. All patients where a subtotal tumor resection was done and where the patient died after surgery had a higher grade tumor. The average follow-up period was 82 months. There was non-symptomatic recurrence in 11 patients. CONCLUSIONS: The location and size of the tumor, extent and duration of visual symptoms, extent of tumor adjoining cerebral edema, encasement of anterior cerebral artery complex and extension in the extracranial compartment were more important factors that affected the outcome of surgery.

Extraspinal-Interdural Surgical Approach for C2 Neurinomas-Report of an Experience with 50 Cases.

OBJECTIVE: We report our experience with surgery in 50 patients with C2 neurinomas. The anatomic subtleties of these discrete forms of tumors and their surgical implications are analyzed. METHODS: During the period 2006-2016, we operated on 50 patients with 55 C2 neurinomas. Type A tumors were located within the spinal canal, type B tumors were located in the lateral gutter, and type C tumors had a paraspinal extension. By working within the dural confines of the tumor and appropriately angulating the microscope, the entire tumor bulk extending into 1 or all 3 compartments was resected. Follow-up duration ranged from 3 months to 10 years (mean 68 months). RESULTS: This series included 36 male and 14 female patients. Age range of patients was 14-70 years (mean age 36 years). Progressive symptoms of myelopathy were present in 41 patients. There were 16 type A + B tumors, 27 type B tumors, 10 type B + C tumors, and 2 type A + B + C tumors. All patients experienced symptom improvement after surgery and were able to resume their normal lifestyle. CONCLUSIONS: C2 neurinomas arise in the region of the C2 ganglion, and despite the fact that some achieve a large size, they remain confined within the dura. Radical tumor resection can be achieved by working within the layers of the dural cover. Bone removal and opening of spinal dura for tumor exposure and resection can be avoided.

Atlantoaxial instability associated with pan cervical vertebral fusion: Report on management of 4 cases.

We report a series of four patients aged 4, 5, 14, and 27 years (1 male and 3 female patients) with severe shortening of the neck and torticollis since early childhood who presented with complaint of pain in the nape of neck as the primary symptom. All four patients had relatively well preserved neurological functions. One patient had vertical mobile and reducible atlantoaxial dislocation, and 3 patients had anteroposterior mobile and reducible dislocation. There was assimilation of atlas in 1 patient. The arch of atlas was bifid in 3 patients. Two patients underwent atlantoaxial fixation. Both the patients were relieved of neck pain after their surgery. The potential surgical difficulties due to the presence of severe shortening of neck height and marginal presenting symptoms favored conservative observation in the other 2 patients. Follow-up ranged from 6 to 84 months. All patients are functionally and socially active.

Multilevel Spinal Segmental Fixation for Kyphotic Cervical Spinal Deformity in Pediatric Age Group-Report of Management in 2 Cases.

OBJECTIVE: We discuss the role of instability of multiple spinal segments including the atlantoaxial joint in the pathogenesis of cervical kyphotic deformity. MATERIAL AND METHODS: Two male patients (5 and 17 years old) had severe cervical kyphosis and presented with symptoms related to myelopathy. The patients underwent multisegmental spinal distraction and fixation that included atlantoaxial joint. No bone decompression was done. RESULTS: At a follow-up of >30 months, both patients had significant neurologic recovery. Investigations at follow-up showed successful arthrodesis of treated spinal segments. Although incomplete, there was recovery in kyphosis. CONCLUSIONS: Multisegmental spinal distraction and fixation can lead to reduction in kyphosis and relief from symptoms related to myelopathy. Role of spinal instability in general and atlantoaxial joint instability in particular in pathogenesis of cervical kyphosis need to be assessed on the basis of studies with a larger number of patients.

Role of Atlantoaxial and Subaxial Spinal Instability in Pathogenesis of Spinal "Degeneration"-Related Cervical Kyphosis.

BACKGROUNDS: The role of subaxial and atlantoaxial instability in the pathogenesis of "degeneration"-related cervical kyphosis is evaluated. MATERIAL AND METHODS: During the period 2013-2016, the authors treated 21 patients having cervical kyphosis that was related to degenerative spinal disease. The patients presented with symptoms related to cervical myelopathy. Kyphosis was diagnosed on the basis of described radiologic parameters. The patients were divided into 3 groups. Group A (10 patients) had manifest radiologic evidence of atlantoaxial dislocation, type 1 facetal instability, abnormal increase in atlantodental interval, and evidence of cord compression by the odontoid process. Group B (5 patients) had axial or central atlantoaxial facetal instability (type 2 or 3 atlantoaxial facetal instability) and subaxial spinal instability. Group C (6 patients) had subaxial spinal instability. The patients were treated by only stabilization. Group A patients underwent atlantoaxial fixation, group B patients underwent atlantoaxial and subaxial fixation, and group C patients underwent only subaxial spinal fixation. The operation was aimed at arthrodesis of the spinal segments. No bone or soft tissue decompression was done. RESULTS: During the minimum follow-up period of 6 months, all patients improved in their neurologic symptoms and demonstrated evidence of spinal arthrodesis. There were no major surgical complications. CONCLUSIONS: Spinal instability plays a major role in the generation of cervical spinal kyphosis. Atlantoaxial instability may form the primary and nodal site of development of the process of spinal degeneration in general and kyphosis in particular.

Indocyanine green as an adjunct for resection of insular gliomas.

OBJECTIVE: Many controversies exist regarding the extent of resection for insular gliomas and the timing of resection. Several techniques and adjuncts are used to maximize safety during resection of these tumors. We describe the use of indocyanine green (ICG) to identify the branches of the middle cerebral artery and discuss its utility to increase safety for resection for insular gliomas. MATERIALS AND METHODS: Five patients with insular gliomas were surgically treated by the authors from June 2013 to June 2014. The patients presented with complaints of either a headache or recurring episodes of convulsions. All the patients were operated with the aid of neuronavigation and tractography. The long perforating branches of the middle cerebral artery course through the insula and pass onward to supply the corona radiata. It is essential to preserve these vessels to prevent postoperative neurological deficits. ICG (Aurogreen) was used to identify and preserve the long perforating arteries of the middle cerebral artery. RESULTS: ICG dye correctly identified the long perforating branches of the middle cerebral artery and easily distinguished these vessels from the short perforating branches. All the branches of the middle cerebral artery that coursed through the tumor and had an onward course were preserved in all the patients. Only one patient developed a transient right sided hemiparesis that had improved at follow-up. CONCLUSIONS: Surgery for insular gliomas is challenging due to its location adjacent to eloquent areas, important white fiber tracts and the course of the middle cerebral artery within it. ICG is useful to identify and preserve the long perforating branches of the middle cerebral artery that course through the tumor and traverse onward to supply the corona radiata.

Immediate Postoperative Disappearance of Retro-Odontoid "Pseudotumor".

OBJECTIVE: The authors present reports of 2 cases in which there was manifest atlantoaxial instability and presence of retro-odontoid pseudotumor. The retro-odontoid tumor disappeared in the immediate postoperative phase after surgery, which involved facetal distraction and atlantoaxial fixation. The cases are discussed. Although regression of the retro-odontoid pseudotumor has been reported after atlantoaxial fixation, its disappearance in the immediate postoperative phase has not been recorded. METHODS: Two patients (42 years and 16 years old) presented with progressive quadriparesis. Investigations revealed presence of retro-odontoid "pseudotumor" and evidence of cord compression. There was radiologic evidence of atlantoaxial instability in both cases. Both patients were treated by atlantoaxial lateral facet distraction and fixation. No attempt was made to directly manipulate or handle the retro-odontoid tissue. RESULTS: The patients had remarkable clinical improvement after surgery. Immediate postoperative imaging showed disappearance of pseudotumor. CONCLUSIONS: The retro-odontoid pseudotumor appears to be related to buckling of the posterior longitudinal ligament. Distraction of the facets probably assists in stretching of the posterior longitudinal ligament. Our experience reconfirms that retro-odontoid pseudotumor could be a manifestation of atlantoaxial instability and need not be directly handled by surgery.

Brain Herniation in Neurofibromatosis with Dysplasia of Occipital Bone and Posterior Skull Base.

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.