✓ Injuries of the cervical spine are relatively rare in children but are a distinct clinical entity compared with those found in adults. The unique biomechanics of the pediatric cervical spine lead to a different distribution of injuries and distinct radiographic features. Children younger than 9 years of age usually have upper cervical injuries, whereas older children, whose biomechanics more closely resemble those of adults, are prone to lower cervical injuries. Pediatric cervical injuries are more frequently ligamentous in nature, and children are also more prone to spinal cord injury without radiographic abnormality than adults are. Physial injuries are specific only to children. Radiographically benign findings, such as pseudosubluxation and synchondrosis, can be mistaken for traumatic injuries. External immobilization with a halo brace can be difficult and is associated with a high complication rate because of the thin calvaria in children. Surgical options have improved with the development of instrumentation specifically for children, but special considerations exist, such as the small size and growth potential of the pediatric spine.
Todd McCall, Dan Fassett, and Douglas Brockmeyer
Pigmented villonodular synovitis associated with pathological fracture of the odontoid and atlantoaxial instability
Case report and review of the literature
Michael A. Finn, Todd D. McCall, and Meic H. Schmidt
✓Pigmented villonodular synovitis (PVNS) is a proliferative disorder of the synovium with a predisposition for the appendicular skeleton. Rarely PVNS can arise from the spine, where this disorder usually presents with localized or radicular pain secondary to involvement of the posterior elements. The authors report the case of an 82-year-old woman who presented with long-standing neck pain and acute upper-extremity numbness and weakness. Computed tomography imaging revealed a mixed sclerotic and lucent lesion affecting the dens and right lateral mass of C-2. There was also a pathological fracture at the base of the dens with 8 mm of anterior dens displacement. Magnetic resonance imaging demonstrated a diffusely infiltrative process that was nonenhancing. Because of instability, the patient underwent transarticular screw fixation, and a biopsy of the lesion was also performed at this time. Histopathological analysis was consistent with a diagnosis of PVNS. To the authors' knowledge, this is the first report of PVNS involving the C-2 vertebra or causing a pathological fracture.
Case report and review of the literature
Frank S. Bishop, James K. Liu, Todd D. McCall, and Douglas L. Brockmeyer
✓Glutaric aciduria type 1 (GA1) is a rare neurometabolic disorder with characteristic neuroimaging and clinicopathological features. The authors describe a case of GA1 in a 7-month-old girl presenting with macrocephaly and bilateral subdural hematomas (SDHs) who was initially evaluated for nonaccidental trauma (NAT). Bilateral subdural drains were placed because of significant mass effect from the chronic SDHs, with subsequent neurological and neuroimaging-documented improvement. Clinical and neuroimaging findings led to further laboratory investigation to confirm the diagnosis of GA1, after which a specialized low-protein diet was initiated. After a thorough investigation, NAT was ruled out. At the follow-up examination, the patient experienced improvement in her symptoms and resolution of the bilateral subdural collections. The presence of bilateral SDHs in an infant raises the suspicion of NAT and presents a difficult diagnostic challenge because of the legal and social implications. Glutaric aciduria type 1 should be considered in the differential diagnosis of bilateral SDHs, and an evaluation should be performed. The authors review the clinical manifestations, diagnosis, medical and surgical management, and specific considerations regarding GA1, including misdiagnosis of NAT.
Daniel R. Fassett, Todd McCall, and Douglas L. Brockmeyer
Odontoid synchondrosis fractures, although rare in the overall incidence of spinal trauma, are one of the more common fractures in young children. The goal of this study was to evaluate the demographic data, incidence of neurological deficits, treatment strategies, and outcomes in a combined series of odontoid synchondrosis fractures treated at the authors' institution and reported in other series.
In a retrospective chart review, the authors identified four odontoid synchondrosis fractures treated at their hospital since January 2000; these were combined with cases reported in six other series in the literature, yielding a total of 55 patients. Data regarding the patients' age, sex, delayed diagnosis, odontoid displacement, neurological deficits, treatment, and fusion status were collected.
The patients' ages ranged from 9 months to 7 years (mean 2.8 years), with neither sex predominating. Diagnosis was delayed in eight cases. The orientation of the odontoid fracture was reported for 36 patients, with 94% experiencing anterior displacement. Spinal cord injury (SCI) was noted in 15 patients, including 11 with complete injuries and eight with SCI at the cervicothoracic junction. Forty-two (93%) of 45 patients with fractures initially treated with external immobilization attained fusion. Eight patients were treated with surgery; four initially, with no attempt at conservative therapy, three after failed halo immobilization, and one after nonunion because of delayed diagnosis.
Odontoid synchondrosis fractures can be difficult to diagnose. In children younger than 7 years of age who present with neck pain or neurological deficits attributable to SCI, this fracture should be suspected. Given the high rate of fusion attained with conservative therapy, it is recommended for most synchondrosis fractures, although surgery may be warranted for individual cases.
Todd McCall, Jeroen Coppens, William Couldwell, and Andrew Dailey
A paracondylar process is a bony exostosis that arises from the skull base lateral to the occipital condyle and extends inferiorly toward the transverse process of the atlas. This congenital anomaly can vary in size from a small protuberance to an elongated process articulating with an epitransverse process arising from C-1. Typically, a paracondylar process is an incidental finding described in anatomical studies. The authors report on a patient with a symptomatic paracondylar process articulating with an epitransverse process that caused occipitocervical pain. Resection of the paracondylar and epitransverse processes completely relieved the patient's pain.
Todd D. McCall, James K. Liu, and John R. W. Kestle
Todd McCall, Steven S. Chin, Karen L. Salzman, and Daniel W. Fults
Tuberous sclerosis (TS) is a congenital neurocutaneous syndrome (or phacomatosis) characterized by widespread development of hamartomas in multiple organs. For affected individuals, neurological and psychiatric complications are the most disabling and lethal features. Although the clinical phenotype of TS is complex, only three lesions characterize the neuropathological features of the disease: cortical tubers, subependymal nodules, and subependymal giant cell astrocytomas. The latter is a benign brain tumor of mixed neuronal and glial origin. Tuberous sclerosis is caused by loss-of-function mutations in one of two genes, TSC1 or TSC2. The normal cellular proteins encoded by these genes, hamartin and tuberin, respectively, form a heterodimer that suppresses cell growth in the central nervous system by dampening the phosphatidylinositol 3–kinase signal transduction pathway. The authors review the clinical and neuropathological features of TS as well as recent research into the molecular biology of this disease. Through this work, investigators are beginning to resolve the paradoxical findings that malignant cancers seldom arise in patients with TS, even though the signaling molecules involved are key mediators of cancer cell growth.
Michael A. Finn, Daniel R. Fassett, Todd D. Mccall, Randy Clark, Andrew T. Dailey, and Darrel S. Brodke
Stabilization with rigid screw/rod fixation is the treatment of choice for craniocervical disorders requiring operative stabilization. The authors compare the relative immediate stiffness for occipital plate fixation in concordance with transarticular screw fixation (TASF), C-1 lateral mass and C-2 pars screw (C1L-C2P), and C-1 lateral mass and C-2 laminar screw (C1L-C2L) constructs, with and without a cross-link.
Ten intact human cadaveric spines (Oc–C4) were prepared and mounted in a 7-axis spine simulator. Each specimen was precycled and then tested in the intact state for flexion/extension, lateral bending, and axial rotation. Motion was tracked using the OptoTRAK 3D tracking system. The specimens were then destabilized and instrumented with an occipital plate and TASF. The spine was tested with and without the addition of a cross-link. The C1L-C2P and C1L-C2L constructs were similarly tested.
All constructs demonstrated a significant increase in stiffness after instrumentation. The C1L-C2P construct was equivalent to the TASF in all moments. The C1L-C2L was significantly weaker than the C1L-C2P construct in all moments and significantly weaker than the TASF in lateral bending. The addition of a cross-link made no difference in the stiffness of any construct.
All constructs provide significant immediate stability in the destabilized occipitocervical junction. Although the C1L-C2P construct performed best overall, the TASF was similar, and either one can be recommended. Decreased stiffness of the C1L-C2L construct might affect the success of clinical fusion. This construct should be reserved for cases in which anatomy precludes the use of the other two.