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Arnold H. Menezes

Object

Hindbrain herniation syndrome, or Chiari malformation Type I (CM-I), occurs frequently with craniovertebral junction (CVJ) abnormalities when there is reduction in the posterior fossa volume. Syringomyelia is often present. Posterior fossa dorsal decompression (PFDD) is typically performed but has adverse results when ventral bone abnormality exists. This paper presents the results of a prospective study on CVJ abnormalities in patients with CM-I and syringomyelia.

Methods

Between 1984 and 2008 (the MR imaging era), 298 patients with CVJ abnormalities and CM-I underwent ventral cervicomedullary decompression. Eighty-four patients had associated syringomyelia (15 with secondary invagination and 69 with primary basilar invagination, os odontoideum, or malunion of fractures). Of these 84 patients with CVJ abnormalities, CM-I, and syringomyelia, 46 had previously undergone PFDD, and 28 had previously undergone PFDD combined with fusion procedures or shunt placements. Of the 84 patients, a cervicothoracic syrinx was observed in 57, thoracic syrinx in 14, and holocord syrinx in 13. Studies included CT, MR imaging, and cine flow studies. All 298 patients who underwent ventral CVJ decompression had irreducible or partially reducible pathology. All 84 with syringomyelia showed brainstem dysfunction, lower cranial nerve symptoms, or myelopathy.

Results

Brainstem signs improved in 66 of the 84 patients, myelopathy improved in 58, and syringomyelia regressed in 64.

Conclusions

Neurological improvement and syringomyelia resolution can occur using only ventral cervicomedullary junction decompression in patients with basilar invagination and basilar impression. This is likely due to the relief of neural encroachment and reestablishment of CSF pathways.

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Arnold H. Menezes

The surgical management of craniovertebral junction (CVJ) instability in pediatric patients presents unique challenges. As compared with the adult patient, the anatomical variations of the CVJ in the pediatric patient are significant, complicate the approach, and limit the use of internal fixation. Diminutive osseous and ligamentous structures and syndromic craniovertebral abnormalities complicate the issue. Advances in imaging analysis and instrumentation have improved the armamentarium for managing the pediatric patient who requires craniocervical stabilization. In this paper, the author's experience of performing more than 850 pediatric CVJ fusions is reviewed. This work includes the indications for atlantoaxial arthrodesis and occipitocervical fusion. Early atlantoaxial fusions were performed using interlaminar rib graft fusion, and more recently using either transarticular screw fixation in the older patient, or lateral mass screws at C-1 and rod fixation with either C-2 pars interarticular screw fixation or pedicle screw fixation. A C-2 translaminar screw fixation is also described. Occipitocervical fusions are performed with rib grafts in patients younger than 6 years of age. Subsequently, above that age, contoured loop fixation was performed, and in the past 8–10 years, screw and rod fixation was used. Abnormal spine growth was not observed in children who underwent craniocervical stabilization below the age of 5 years (clearly the bone grew with the patient). However, no deleterious effects were noted in the children treated with rigid instrumentation. The success rate for bone fusion alone was 98%. The author's success rate with rigid instrumentation is nearly 100%. A detailed review of the technique of fusion is presented, as well as the indications and means of avoidance of complications, their prevention, and management.

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Evaluation and treatment of congenital and developmental anomalies of the cervical spine

Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2004

Arnold H. Menezes

✓ Congenital and developmental osseous abnormalities of the cervical spine can result in neural compression ranging from the medulla oblongata to the cervicothoracic spinal cord junction. These may present in infancy as scoliosis and even limb weakness. A high index of suspicion is essential. Neurodiagnostic imaging relies on high-resolution computerized tomography (CT) scanning and three-dimensional CT reconstructions as well as magnetic resonance imaging and angiography. The anatomical/physiological CT factors considered when developing a surgical approach are: 1) the stability and reducibility of the lesions; 2) direction and manner of encroachment of the lesion on the neural structures; 3) neural and vascular abnormalities; and 4) growth potential of the affected area. Primary stabilization is required for reducible lesions, whereas irreducible lesions are decompressed in the manner in which encroachment has occurred. Instability, whether present before or after operative intervention, required spinal stabilization. Illustrative examples of this approach are presented.

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Arnold H. Menezes

Os odontoideum is an uncommon craniovertebral junction (CVJ) abnormality that exists as a separate ossicle apart from a hypoplastic dens. It usually moves with the clivus or the anterior arch of C-1 (dystopic) or rarely with the dens (orthotopic). Its genesis and natural history have been debated, and its proper treatment remains uncertain.

Two hundred and sixty patients, with symptomatic os odontoideum, were evaluated by the author over a 20-year period; the author performed surgery in 134 of these patients. In a prospective study the author evaluated the early childhood history of trauma, the dynamic studies of motion, and the effects of traction by using pleuridirectional tomography, computerized tomography (CT), CT myelography and magnetic resonance (MR) imaging. Operative findings were documented.

Early childhood trauma to the CVJ was recorded in 74 patients, in 30 of whom normal odontoid processes were documented at initial examination prior to the patient reaching age 4 years.

Acute neurological deterioration following trauma occurred in 63 of 134 patients. Symptoms were insidious in 71 of 134 patients. In six patients, who presented with acute neurological deterioration after trauma and in whom an abnormal spinal cord signal in the cervicomedullary junction was demonstrated on MR imaging, normal CVJ motion dynamics were shown. Motion dynamics varied and were unique to each patient. Irreducible ventral CVJ disease causing cervicomedullary compromise occurred in 28 patients in whom a transpharyngeal ventral decompressive procedure was necessitated. During the transoral operation, the transverse portion of the cruciate ligament was found to be located anterior to the axis body. All patients required dorsal CVJ arthrodesis, which, in 46, was limited to the C1-2 segment. Instability at the C1-2 joints was always multidirectional, as demonstrated on preoperative neuroimaging studies as well as at operation.

Sixteen patients presented after completed primary C1-2 dorsal fusion and with worsening deficits. They improved when the range of the fusion was extended to the occiput or if the ventrally located lesion was excised.

Os odontoideum is associated with early childhood trauma and is an acquired phenomenon. The presence of abnormal motion dynamics necessitates surgical intervention as do associated neurological deficits. Asymptomatic patients in whom os odontoideum is incidentally discovered and in whom no abnormal motion dynamics are demonstrated should be followed closely.

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Retroclival hematoma in the pediatric population

Report of two cases and review of the literature

Daniel Guillaume and Arnold H. Menezes

✓ Case reports of retroclival hematoma are infrequent, and little is known about the mechanism of formation of the lesion, its management strategy, and the outcome in affected patients. The authors report two cases of posttraumatic retroclival hematoma in children and discuss the available literature. Both patients were treated with cervical immobilization and had good outcomes.

Retroclival hematomas are rare. Most reported cases involve pediatric patients in whom the hematomas developed in association with trauma. Spinal trauma in children mainly occurs at the craniovertebral junction due to a high fulcrum of cervical motion and results in ligamentous injuries more often than fractures. The formation of epidural hematomas posterior to the clivus is likely to be due to either clivus fracture or ligament disruption. A high index of suspicion is essential in making the diagnosis. Magnetic resonance imaging is superior to computed tomography in demonstrating retroclival hematomas because of its superiority in delineating the extradural spaces and the integrity of the ligaments. The authors conclude that in most cases retroclival hematomas can be treated conservatively and good outcomes can be expected.

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Raheel Ahmed and Arnold H. Menezes

Clinical presentation of craniovertebral junction disorders may range from acute catastrophic neurological deficits to insidious signs and symptoms that may mask the underlying etiology. Prompt recognition and treatment is essential to avert long-term neurological morbidity. Proatlas segmentation disorders are a rare group of developmental disorders involving the craniocervical junction. Abnormal bony segmentation leads to malformed bony structures that can in turn lead to neurological deficits through bony compression of the cervicomedullary junction. This report details a proatlas segmentation defect presenting as palatal myoclonus, a rare movement disorder. The clinical presentation, surgical management, and neuroanatomical basis for the disorder is presented. This report highlights the myriad clinical presentations of craniovertebral disorders and emphasizes a rare but treatable etiology for palatal myoclonus.

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Arnold H. Menezes

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Arnold H. Menezes and Raheel Ahmed

Object

Atlantoaxial tumors account for a substantial proportion of primary bone tumors in children. Before resection, surgeons must consider the complex regional anatomy, the potential for neurological compromise, craniocervical instability, and the question of tumor resectability in a growing spine. Using current technology, the authors analyzed surgical cases in this light and present outcomes and treatment recommendations after long-term patient follow-up.

Methods:

The authors reviewed clinical records for 23 children whose primary atlantoaxial bone tumors were treated from 1996 through 2010.

Results

Pathological lesions among the 23 patients were 4 aneurysmal bone cysts, 2 osteochondromas, 5 chordomas, 4 osteoblastomas, 3 fibrous dysplasias, 4 eosinophilic granulomas, and 1 Ewing's sarcoma. Clinical presentation consisted of neck pain (n = 23), headaches and occipital pain (n = 16), myelopathy (n = 8), and torticollis (n = 4). Selective angiography and coil embolization were undertaken for all patients with aneurysmal bone cysts and osteoblastomas, 2 patients with chordomas, 1 patient with fibrous dysplasia, and 1 patient with Ewing's sarcoma. Primary embolization treatment of radiation-induced aneurysmal bone cyst of the atlas showed complete reossification. Results of CT-guided needle biopsy were diagnostic for 1 patient with eosinophilic granuloma and 1 with Ewing's sarcoma. Needle biopsies performed before referral were associated with extreme blood loss for 1 patient and misdiagnosis for 2 patients. Surgery involved lateral extrapharyngeal, transoral, posterior, and posterolateral approaches with vertebral artery rerouting. Complete resection was possible for 9 patients (2 with osteochondroma, 3 with fibrous dysplasia, 2 with chordoma, and 2 with osteoblastoma). Decompression and internal fusion were performed for 3 patients with aneurysmal bone cysts. Of the 23 patients, 7 underwent dorsal fusion and 4 underwent ventral fusion of the axis body. Chemotherapy was necessary for the patients with eosinophilic granuloma with multifocal disease and for the patient with Ewing's sarcoma. There was no morbidity, and there were no deaths. All patients with benign lesions were free of disease at the time of the follow-up visit (mean ± SD follow-up 8.8 ± 1.1 years; range 2–18 years). Chordomas received proton or LINAC irradiation, and as of 4–15 years of follow-up, no recurrence has been noted.

Conclusions

Because most atlantoaxial tumors in children are benign, an intralesional procedure could suffice. Vascular control and staged resection are critical. Ventral transoral fusion or lateral extrapharyngeal fusion has been successful. Resection with ventral fusion and reconstruction are essential for vertebral body collapse. Management of eosinophilic granulomas must be individualized and might require diagnosis through needle biopsy.

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Andrei Fernandes Joaquim

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Paul D. Sawin and Arnold H. Menezes

✓ Osteogenesis imperfecta (OI) is a heritable disorder of bone development caused by defective collagen synthesis. Basilar invagination is an uncommon but devastating complication of this disease. The authors present a comprehensive strategy for management of craniovertebral anomalies associated with OI and related osteochondrodysplasias.

Twenty-five patients with congenital osteochondrodysplasias (18 OI, four Hajdu—Cheney syndrome, and three spondyloepiphyseal dysplasia) and basilar invagination were evaluated between 1985 and 1995. The male/female ratio in this cohort was 1:1. The mean age at presentation was 11.9 years (range 13 months–20 years). Fourteen patients (56%) presented during adolescence (11–15 years of age). Symptoms and signs included headache (76%), lower cranial nerve dysfunction (68%), hyperreflexia (56%), quadriparesis (48%), ataxia (32%), nystagmus (28%), and scoliosis (20%). Four patients (16%) were asymptomatic. Seven (28%) had undergone previous posterior fossa decompression; one had also undergone ventral decompression. Imaging findings included basilar invagination (100%), ventral brainstem compression (84%), hydrocephalus (32%), hindbrain herniation (28%), and syringomyelia/syringobulbia (16%).

Patients with hydrocephalus underwent ventricular shunt placement. Reducible basilar invagination (40%) was treated with posterior fossa decompression and occipitocervical fusion. Those with irreducible ventral compression (60%) underwent transoral—transpalatopharyngeal decompression followed by occipitocervical fusion. All patients improved initially. However, basilar invagination progressed radiographically in 80% (symptomatic in 24%) despite successful fusion. Prolonged external orthotic immobilization with the modified Minerva brace afforded symptomatic improvement and arrested progression of the deformity. The mean follow-up period was 5.9 years (range 1.1–10.5 years).

Ventral brainstem compression in OI should be treated with ventral decompression, followed by occipitocervical fusion with contoured loop instrumentation to prevent further squamooccipital infolding. Despite fusion, however, basilar invagination tends to progress. Prolonged immobilization (particularly during adolescence) may stabilize symptoms and halt further invagination. This study represents the largest series to date addressing craniovertebral anomalies in OI and related congenital bone softening disorders.