John Zovickian

Long-term outcome of total and near-total resection of spinal cord lipomas and radical reconstruction of the neural placode: part I-surgical technique.

OBJECTIVEPartial resection of complex spinal cord lipomas is associated with a high rate of symptomatic recurrence caused by retethering, presumably promoted by a tight content-container relationship between the spinal cord and the dural sac, and incomplete detachment of the terminal neural placode from residual lipoma. Since 1991, we have performed more than 250 total/near-total resections of complex lipomas with radical reconstruction of the neural placodes. Sixteen years of follow-up have proven the long-term benefits of this technique. Part I of this series introduces our technique of total resection and reports the immediate surgical results. Part II will analyze the long-term outcomes of both total and partial resection and identify the factors affecting outcome. METHODSFrom 1991 to 2006, 238 patients (age range, 2 months–72 years) with dorsal, transitional, and chaotic lipomas underwent total or near-total lipoma resection and radical placode reconstruction. Eighty-four percent of the patients were children younger than 18 years and 16% were adults. The technique consisted of wide bony exposure, complete unhinging of the lateral adhesions of the lipoma-placode assembly from the inner dura, untethering of the terminal conus, radical resection of the fat off the neural plate along a white fibrous plane at the cord-lipoma interface, meticulous pia-to-pia neurulation of the supple neural placode with microsutures, and expansile duraplasty with a bovine pericardial graft. Elaborate electrophysiological monitoring was used. RESULTSThree postoperative observations concern us. The first is that of the 238 patients, 138 (58%) had no residual fat on postoperative magnetic resonance imaging; 81 patients (36%) had less than 20 mm3 of residual fat, the majority of which were small bits enclosed by neurulation; and 19 patients (8%), mainly of the chaotic lipoma group, had more than 20 mm3 of fat. There are no significant differences in the amount of residual fat among lipoma types, but redo lipomas are more likely than virgin (previously unoperated on) lipomas to have residual fat by a factor of 2 (P = 0.0214). The second concern is that the state of the reconstructed placode is objectively measured by the cord-sac ratio, obtained by dividing the sagittal diameter of the reconstructed neural tube by the sagittal diameter of the thecal sac. A total of 162 patients (68%) had cord-sac ratios less than 30% (low), 61 (25.6%) had ratios between 30% and 50% (medium), and only 15 (6.3%) had high ratios of more than 50%. Seventy-four percent of patients with virgin lipomas had low cord-sac ratios compared with 56.3% in the redo lipoma patients. The overall distribution of cord-sac ratio is significantly different between redo and virgin lipomas (P = 0.00376) but not among lipoma types. Finally, the incidence of combined neurological and urological complications was 4.2%. The combined cerebrospinal fluid leak and wound infection/dehiscence incidence was 2.5%. Both sets of surgical morbidity compared favorably with the published rates reported for partial resection. CONCLUSIONTotal/near-total resection of spinal cord lipomas and complete reconstruction of the neural placode can be achieved with low surgical morbidity and a high yield of agreeable postoperative cord-sac relationship. Some large rambling transitional lipomas and most chaotic lipomas are the most difficult lesions to resect and tend to have less favorable results on postresection magnetic resonance imaging.

ATLANTO-OCCIPITAL DISLOCATIONPART 1—NORMAL OCCIPITAL CONDYLE-C1 INTERVAL IN 89 CHILDREN

OBJECTIVEAlthough atlanto-occipital dislocation has long been recognized as an extremely unstable and often lethal injury, no single radiodiagnostic criterion published to date has achieved failure-proof status. This is because most existing diagnostic tests exploit bony landmarks remote from the injured condyle–C1 (OC1) joint so that patient positioning could inadvertently line up these landmarks and conceal actual disruption of the joint. Many of the landmarks used are wide apart and/or noncoplanar; their measurements are subject to errors related to x-ray angle, target–film distance, and superimposed bony outlines. We propose using the actual occipital condyle–C1 interval (CCI) obtained from high-resolution reconstructed computed tomographic scans as the indicator for OC1 joint disruption. We hypothesize that the normal CCI is very small and has great left-right symmetry and that atlanto-occipital dislocation is always manifested by an abnormal widening of the CCI and/or by left-right joint asymmetry irrespective of the shifting of other remote bony landmarks. Part I of this study establishes standard normal values for CCI in children. METHODSagittal and coronal reformatted images were obtained from thin axial computed tomographic scans performed on 89 children, 18 for nontraumatic complaints and 71 as part of a minor head trauma protocol but later exonerated for cervical injury. The interval between condyle and C1 was measured at four equidistant points on the joint surface on the sagittal and coronal images of all 178 joints (left and right) in the group. Sagittal and coronal CCIs are the means of four sagittal and four coronal measurements, respectively. The combined or true CCI for an individual joint was taken as the mean of both the sagittal and coronal (total of eight) measurements. RESULTSThe mean combined CCI of all 178 joints was 1.28 mm ± 0.26 (standard deviation [SD]). None of the 178 CCIs exceeded 1.95 mm, and none of the individual joint interval measurements exceeded 2.5 mm. Left-right symmetry was tested by computing the mean left-right difference in CCI from all 89 subjects equal to 0.047 mm ± 0.002 (SD); or only 3% of the mean combined CCI. When the mean of all right CCIs (1.333 mm ± 0.31 SD) is contrasted with the mean of all left CCIs (1.327 mm ± 0.30 SD), the difference is 0.006 mm, or 1.09% of the mean total CCI (P = 0.792). Left-right symmetry is also apparent in conformational anatomy in both sagittal and coronal images. Linear regression analysis between CCI and age shows no statistical difference in CCI between age groups from 0.5 to 18 years. Linear regression performed separately on the right and left CCIs suggests that left-right symmetry is also stable through this age range. CONCLUSIONThe normal OC1 joint in children 0 to 18 years is tightly held together by ligaments with a mean CCI of 1.28 mm in the 89 subjects tested. There is great left–right joint symmetry in both CCI and conformational anatomy. CCI and left-right symmetry do not appear to change significantly with age. It is reasonable to set a maximum CCI as a discriminator between normal and disrupted OC1 joints to indicate atlanto-occipital dislocation.

Long-term outcome of total and near-total resection of spinal cord lipomas and radical reconstruction of the neural placode, part II: outcome analysis and preoperative profiling.

OBJECTIVETo show the long-term benefits of total and near-total resection of complex spinal cord lipomas and reconstruction of the neural placode. METHODSWe analyzed 238 patients with dorsal, transitional, and chaotic lipomas who had total resection as described in part I for overall progression-free survival probability (PFS, Kaplan-Meier analysis) over 16 years. We also analyzed subgroup proportional recurrence hazard (Cox analysis) of 6 outcome predictors of sex, lipoma type, age, preoperative symptoms, previous surgery, and postoperative cord-sac ratio. These results were compared with an age-matched, lesion-matched series of 116 patients followed for 11 years after partial lipoma resection and with the Parisian series of nonsurgical treatment. RESULTSThe immediate effects of surgery were similar between total and partial resection: both achieved greater than 95% symptom stabilization or improvement rate. The neuro-urologic complication rates for the groups were also similar, 4.2% and 5.2% for total and partial resection, respectively. The combined cerebrospinal fluid leakage and wound complication rate of total resection was much lower at 2.5% than the 6.9% for partial resection, but both were better than published rates. The overall PFS for total resection was 82.8% at 16 years, comparing much more favorably with 34.6% for partial resection at 10.5 years (P < .0001). Culling only the asymptomatic patients with virgin (previously unoperated) lipomas to match the patient profile of the Parisian series, the PFS for prophylactic total resection for this subgroup increased to 98.4% at 16 years, versus 67% at 9 years for no surgery and 43.3% at 10.5 years for our own partial resection series, with a remarkable statistical difference between total and partial resection (P = .00001). Subgroup analyses showed that sex and lipoma type did not affect outcome. For the other predictor variables, while univariate analyses showed that young age, absence of symptom, and virgin lipomas correlated with better statistical PFS than older age, symptoms, and redo lipomas, these effects vanished with multivariate analyses. Cord-sac ratio stood alone as the only influential outcome predictor in multivariate analysis, with a 96.6% PFS for a low ratio of <30% and an 80.6% progression-free probability for a high ratio of >50%, and a 3-fold increase in recurrence hazard for high ratios (P = .0009). This suggested that all the individual effects of the other predictor variables could be reduced to whether a low cord-sac ratio could be achieved with total lipoma resection and placode reconstruction. Cord-sac ratio was the obvious factor that differentiated the outcomes between total and partial resection, the latter associated with a >90% chance of having a high cord-sac ratio. CONCLUSIONTotal and near-total resection of lipomas and complete reconstruction of the neural placode produced a much better long-term progression-free probability than partial resection and nonsurgical treatment. The perioperative complications for total resection were low and compared favorably with published results. A low postoperative cord-sac ratio and well-executed placode neurulation were strongly correlated with good outcome. The ideal preoperative patient profile with early disease stabilization and the best recurrence-free probability is an asymptomatic child less than 2 years without previous lipoma surgery. There are strong indications that partial resection in many cases produces worse scarring on the neural placode and worse prognosis than no surgery.

Clear Cell Meningioma: Case Report and Review of the Literature

Clear cell meningioma (CCM) is a rare variant of meningioma. Only 17 cases have been previously reported in children. Although it has bland cytologic features, it has a higher rate of recurrence than does conventional meningioma. This variant has been reported in sites such as spinal/intradural (lumbar and thoracic), cerebellopontine angle, and supratentorial. The differential diagnosis of CCM includes microcystic meningioma, hemangioblastoma, and clear cell ependymoma. The characteristic histology and immunohistochemistry leads to the diagnosis. We present a case of a 7-year-old boy with a CCM of the cauda equina and a review of pediatric CCM.

Limited Dorsal Myeloschisis: A Distinctive Clinicopathological Entity

BACKGROUND: Limited dorsal myeloschisis (LDM) is a distinctive form of spinal dysraphism characterized by 2 constant features: a focal “closed” midline defect and a fibroneural stalk that links the skin lesion to the underlying cord. The embryogenesis is hypothesized to be incomplete disjunction between cutaneous and neural ectoderms, thus preventing complete midline skin closure and allowing persistence of a physical link (fibroneural stalk) between the disjunction site and the dorsal neural tube. OBJECTIVE: To illustrate these features in 51 LDM patients. METHODS: All patients were studied with magnetic resonance imaging or computed tomography myelography, operated on, and followed for a mean of 7.4 years. RESULTS: There were 10 cervical, 13 thoracic, 6 thoracolumbar and 22 lumbar lesions. Two main types of skin lesion were saccular (21 patients), consisting of a skin-base cerebrospinal fluid sac topped with a squamous epithelial dome, and nonsaccular (30 patients), with a flat or sunken squamous epithelial crater or pit. The internal structure of a saccular LDM could be a basal neural nodule, a stalk that inserts on the dome, or a segmental myelocystocele. In nonsaccular LDMs, the fibroneural stalk has variable thickness and complexity. In all LDMs, the fibroneural stalk was tethering the cord. Twenty-nine patients had neurological deficits. There was a positive correlation between neurological grade and age, suggesting progression with chronicity. Treatment consisted of detaching the stalk from the cord. Most patients improved or remained stable. CONCLUSION: LDM is a distinctive clinicopathological entity and a tethering lesion with characteristic external and internal features. We propose a new classification incorporating both saccular and flat lesions.

Intranasal schwannoma with extension into the intracranial compartment: case report

The authors present a case of intranasal schwannoma with extension into the intracranial compartment. Computed tomographic findings are presented, and a combined intranasal and subfrontal operative approach is described. The pathology, origin, and clinical characteristics of intranasal schwannomas are reviewed.

Retained medullary cord in humans: late arrest of secondary neurulation.

BACKGROUND:Formation of the caudal spinal cord in vertebrates is by secondary neurulation, which begins with mesenchyme-epithelium transformation within a pluripotential blastema called the tail bud or caudal cell mass, from thence initiating an event sequence proceeding from the condensation of mesenchyme into a solid medullary cord, intrachordal lumen formation, to eventual partial degeneration of the cavitatory medullary cord until, in human and tailless mammals, only the conus and filum remain. OBJECTIVE:We describe a secondary neurulation malformation probably representing an undegenerated medullary cord that causes tethered cord symptoms. METHOD:We present 7 patients with a robust elongated neural structure continuous from the conus and extending to the dural cul-de-sac, complete with issuing nerve roots, which, except in 2 infants, produced neurological deficits by tethering. RESULTS:Intraoperative motor root and direct cord stimulation indicated that a large portion of this stout neural structure was “redundant” nonfunctional spinal cord below the true conus. Histopathology of the redundant cord resected at surgery showed a glioneuronal core with ependyma-lined lumen, nerve roots, and dorsal root ganglia, corroborating the picture of a blighted spinal cord. CONCLUSION:We propose that these redundant spinal cords are portions of the medullary cord normally destined to regress but are here retained because of late arrest of secondary neurulation before the degenerative phase. Because programmed cell death almost certainly plays a central role during degeneration, defective apoptosis may be the underlying mechanism.

Terminal Myelocystocele: Surgical Observations and Theory of Embryogenesis

BACKGROUND The structural complexity of terminal myelocystocele (TMC) precludes a recognizable link to spinal cord development and therefore a plausible embryogenetic theory. OBJECTIVE To demystify TMC using clinical, imaging, surgical, electrophysiological, and histopathological data and to propose a theory of embryogenesis. METHODS Our series consisted of 4 newborns and 6 older children. All had preoperative magnetic resonance imagings and surgical repair of the myelocystocele with electrophysiological monitoring. RESULTS TMC can be deconstructed into essential and nonessential features. Essential features are present in all TMCs and constitute the core malformation, comprising an elongated spinal cord extending extraspinally into a cerebrospinal fluid--filled cyst that is broadly adherent to the subcutaneous fat. The functional conus resides in the proximal cyst or within the intraspinal cord, and the caudal myelocystocele wall is nonfunctional fibroneural tissue. Nonessential features include variable measures of hydromyelia, caudal meningocele, and fat, present in only some patients. The core structure of TMC strikingly resembles a transitory stage of late secondary neurulation in chicks in which the cerebrospinal fluid-filled bleblike distal neural tube bulges dorsally to fuse with the surface ectoderm, before focal apoptosis detaches it from the surface and undertakes its final dissolution. We theorize that TMC results from a time-specific paralysis of apoptosis just before the dehiscence of the cystic distal cord from the future skin, thereby preserving the embryonic state. CONCLUSION Besides tethering, the myelocystocele may show early rapid expansion causing precipitous deterioration. We recommend early repair with resection of the nonfunctional caudal cyst wall, reconstruction of the proximal neural placode, and duraplasty.

Isolated unilateral rupture of the alar ligament

Only 6 cases of isolated unilateral rupture of the alar ligament have been previously reported. The authors report a new case and review the literature, morbid anatomy, and pathogenesis of this rare injury. The patient in their case, a 9-year-old girl, fell head first from a height of 5 feet off the ground. She presented with neck pain, a leftward head tilt, and severe limitation of right rotation, extension, and right lateral flexion of the neck. Plain radiographs and CT revealed no fracture but a shift of the dens toward the right lateral mass of C-1. Magnetic resonance imaging of the cervical spine showed signal hyperintensity within the left dens-atlas space on both T1- and T2-weighted sequences and interruption of the expected dark signal representing the left alar ligament, suggestive of its rupture. After 12 weeks of immobilization in a Guilford brace, MRI showed lessened dens deviation, and the patient attained full and painless neck motion. Including the patient in this case, the 7 patients with this injury were between 5 and 21 years old, sustained the injury in traffic accidents or falls, presented with marked neck pain, and were treated with external immobilization. All patients had good clinical outcome. The mechanism of injury is hyperflexion with rotation. Isolated unilateral alar ligament rupture is a diagnosis made by excluding associated fracture, dislocation, or disruption of other major ligamentous structures in the craniovertebral junction. CT and MRI are essential in establishing the diagnosis. External immobilization is adequate treatment.

Unjoined primary and secondary neural tubes: junctional neural tube defect, a new form of spinal dysraphism caused by disturbance of junctional neurulation

IntroductionPrimary and secondary neurulation are the two known processes that form the central neuraxis of vertebrates. Human phenotypes of neural tube defects (NTDs) mostly fall into two corresponding categories consistent with the two types of developmental sequence: primary NTD features an open skin defect, an exposed, unclosed neural plate (hence an open neural tube defect, or ONTD), and an unformed or poorly formed secondary neural tube, and secondary NTD with no skin abnormality (hence a closed NTD) and a malformed conus caudal to a well-developed primary neural tube.Methods and resultsWe encountered three cases of a previously unrecorded form of spinal dysraphism in which the primary and secondary neural tubes are individually formed but are physically separated far apart and functionally disconnected from each other. One patient was operated on, in whom both the lumbosacral spinal cord from primary neurulation and the conus from secondary neurulation are each anatomically complete and endowed with functioning segmental motor roots tested by intraoperative triggered electromyography and direct spinal cord stimulation. The remarkable feature is that the two neural tubes are unjoined except by a functionally inert, probably non-neural band.ConclusionThe developmental error of this peculiar malformation probably occurs during the critical transition between the end of primary and the beginning of secondary neurulation, in a stage aptly called junctional neurulation. We describe the current knowledge concerning junctional neurulation and speculate on the embryogenesis of this new class of spinal dysraphism, which we call junctional neural tube defect.