Parallel angulated frontal bone slat cuts for treatment of metopic synostosis and other frontal skull deformities: the "cathedral dome procedure"

PURPOSE

This study aims to describe a new procedure for the treatment of metopic synostosis and other frontal skull deformities.

METHOD

The procedure comprises a supraorbital bandeau widened with an interpositional graft and rounded laterally to eliminate the acute angle, and parallel angulated slat cuts in the frontal bones. Greenstick fracturing of the medial bases of these slats along a parasagittal hinge line causes fanning of the slats and expansion of the frontal flap both anteriorly and laterally making the forehead contour wider and more rounded. We performed this procedure on six infants (four with severe trigonocephaly from metopic synostosis, one with brachycephaly from bicoronal synostosis, and one with multiple suture synostosis and parietal flattening) for whom only the angulated slat cuts (without bandeau) were used. Each patient had preoperative three-dimensional computed tomography (3D-CT) and postoperative 3D-CT at 1 week, 3 months, and 12 months, to follow the result.

RESULT

The cosmetic improvements are dramatic in eliminating the midfrontal keel, hypotelorism, frontal-lateral retrusion, and temporal hollowing seen in severe metopic synostosis. In coronal synostosis, the procedure corrects the brachycephaly and gives a balanced, well-rounded frontal contour. The end results of the fronto-orbital correction resemble the ribbed dome of a cathedral; hence, the moniker the "cathedral dome procedure". No patient needed a second procedure to fill in cranial defects or recorrect deficient areas.

CONCLUSION

The parallel angulated frontal slat cuts technique (the "cathedral dome procedure") is a straightforward and easily mastered method that reliably produces excellent result for the correction of trigonocephaly and other frontal skull deformities.

Limited dorsal myeloschisis: a not-so-rare form of primary neurulation defect

PURPOSE

Limited dorsal myeloschisis (LDM) is a distinctive form of spinal dysraphism characterized by two constant features: a focal "closed" midline skin 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

We utilize the experience gained from the management of 63 patients with LDM to illustrate these features.

METHODS

All patients were studied with MRI or CT myelogram, operated on, and followed for a mean of 9.4 years.

RESULTS

There were 11 cervical, 16 thoracic, 8 thoracolumbar, and 28 lumbar lesions. Two main types of skin lesion were: saccular (26 patients; consisting of a skin base cerebrospinal fluid sac topped with squamous epithelial dome or a thin membranous sac) and nonsaccular (37 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 myelocystocoele. In nonsaccular LDMs, the fibroneural stalk has variable thickness and complexity. All fibroneural stalks contain glioneuronal tissues accompanied by variable quantities of nerves and mesodermal derivatives. 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. LDMs were associated with three other dysraphic malformations in more than coincidental frequencies: six LDMs were contiguous with dorsal lipomas, four LDMs shared the same tract or traveled in parallel with a dermal sinus tract, and seven LDMs were related to a split cord malformation. The embryogenetic implications of these associations are discussed.

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.

Surgical treatment of complex spinal cord lipomas

PURPOSE

This paper shows the long-term benefits of total/near-total resection of complex spinal cord lipomas and meticulous reconstruction of the neural placode, and specifically, its advantage over partial resection, and over non-surgical treatment for the subset of children with asymptomatic virgin lipomas.

METHODS

The technique of total resection and placode reconstruction, together with technical nuances, are described in detail. We added 77 patients with complex lipomas to our original lipoma series published in 2009 and 2010, to a total of 315 patients who had had total or near-total resection and followed for a span of 20 years. Long-term outcome is measured by overall progression-free survival (PFS) with the Kaplan-Meier analysis, and by subgroup Cox proportional recurrence hazard analysis for the influence on outcome of 4 predictor variables of lipoma type, presence of symptoms, prior surgery, and post-operative cord-sac ratio. These results are compared to an age-matched, lesion-matched series of 116 patients who underwent partial lipoma resection over 11 years. The results for total resection is also compared to two large published series of asymptomatic lipomas followed without surgery over 9 to 10 years, to determine whether prophylactic total resection confers better long-term protection over conservative treatment for children with asymptomatic lipomas..

RESULTS

The PFS after total resection for all lipoma types and clinical subgroups is 88.1 % over 20 years versus 34.6 % for partial resection at 10.5 years (p < 0.0001). Culling only the asymptomatic patients with virgin (previously unoperated) lipomas, the PFS for prophylactic total resection for this subgroup rose to 98.8 % over 20 years, versus 67 % at 9 years for one group of non-surgical treatment and 60 % at 10 years for another group of conservative treatment. Our own as well as other published results of partial resection also compare poorly to non-surgical treatment for the subset of asymptomatic virgin lipomas. Multivariate subgroup analyses show that cord-sac ratio is the only independent variable that predicts outcome, with a 96.9 % PFS for ratio < 30 % (loosest sac), 86.2 % for ratio between 30 and 50 %, and 78.3 % for ratio > 50 % (tightest sac), and a threefold increase in recurrence hazard for high ratios (p = 0.0009). Pre-operative patient profiling using multiple correspondence analysis shows the ideal patient for total resection is a child less than 2 years old with a virgin asymptomatic lipoma, who, with a PFS of 99.2 %, is virtually cured by total resection.

CONCLUSION

Total/near-total resection of complex lipomas and complete reconstruction of the neural placode achieves far better long-term protection against symptomatic recurrence than partial resection for all lesions; and for the subset of asymptomatic virgin lipomas, also better than non-surgical treatment. Partial resection in many cases produces worse outcome than conservative treatment for asymptomatic lesions.

Pathoembryogenesis of terminal myelocystocele: terminal balloon in secondary neurulation of the chick embryo

PURPOSE

Terminal myelocystocele (TMC) is thought to be caused by a misstep during secondary neurulation. However, due to the paucity of data on secondary neurulation and the rarity of TMC, proofs of this pathogenetic mechanism are unavailable. Based on a previous observation that TMC resembles a step of secondary neurulation in chick, a closer look was taken at secondary neurulation of chick embryos focusing on the cerebrospinal fluid-filled distal neural tube (terminal balloon).

METHODS

Chick embryos at Hamburger and Hamilton (H-H) stages of 28, 30, 33, 35, 37, and 40 were harvested. Hematoxying-eosin staining, additional immunohistochemistry (laminin, cytokeratin, nestin), and scanning electron microscopy were performed.

RESULTS

In H-H stages 28 to 30, after merging of the lumina of the primary and secondary neural tubes, the caudal end of the confluent tube dilates into a balloon-like structure (terminal balloon). As the proximal tube progressively becomes narrower, the terminal balloon dilates even further, and its wall fuses with the surface ectoderm (H-H stage 33). Later in H-H stages 35 to 40, the terminal balloon shrinks and becomes detached from the surface ectoderm and ultimately disappears, as the proximal lumen of the secondary neural tube continues to collapse.

CONCLUSION

A dilated balloon doubtlessly exists in the terminal secondary neural tube in chick embryos, and its subsequent disappearance occurs in a variable time course and sequence. Arrest of apoptosis resulting in failure of detachment of the terminal balloon from the surface ectoderm may well be the basis for human TMC.

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.

Identification and characterization of pig embryo microRNAs by Solexa sequencing

MicroRNAs (miRNAs) are a class of small, non-coding RNAs of approximately 22 nucleotides in length that regulate gene expression by binding to the 3'-untranslated regions of target mRNAs. It is now clear that miRNAs are involved in many biological processes, including proliferation, differentiation and regulation of gene expression during early embryonic development. The miRBase 16.0 (2010) shows that there are 175, 673, 408 and 1048 annotated miRNAs for Caenorhabditis elegans, Mus musculus, Rattus norvegicus and Homo sapiens, respectively. However, there are only 211 miRNAs described for Sus scrofa. In particular, the full set of miRNAs and their expression patterns are still poorly understood in the embryo. Therefore, we combined Solexa sequencing with computational techniques to analyse the sequences and relative expression levels of S. scrofa miRNAs at embryonic day 33 (E33). Of the distinct miRNAs identified, 76 previously known miRNAs and 194 candidate miRNAs were identified in head, and 77 known miRNAs and 130 predicted candidate miRNAs were identified in organ region. Furthermore, we performed additional investigation for identifying the potential target mRNAs using PicTar and TargetScan. Concurrent function analysis suggested that highly expressed miRNAs are mostly involved in the development of nerves, cerebrum, muscle and organs. Our results provide useful information for the investigation into embryonic miRNAs of pig and provide a valuable resource for investigators interested in the regulation of embryonic development in pigs and other animals.

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.

Analysis of myostatin and its related factors in various porcine tissues

Myostatin is expressed in skeletal muscle tissue where it functions to suppress myoblast proliferation and myofiber hypertrophy. Recently, myostatin was detected in the tendon, mammary gland, and adipose tissue of mice. We sought to determine whether myostatin is expressed in the liver, spleen, lung, and kidney of pigs. Real-time PCR and Western blots demonstrated that myostatin, follistatin, decorin, and activin receptor IIB (ActRIIB) mRNA and proteins were expressed in skeletal muscle, heart muscle, and adipose tissue, and also in liver, spleen, lung, kidney, and cultured fibroblasts. The relative abundance of myostatin was closely related to follistatin and decorin in porcine tissues. Immunohistochemical analysis further demonstrated the presence of myostatin, follistatin, and decorin in the skeletal muscle, adipose tissue, heart muscle, liver, spleen, lung, and kidney of pigs. These results suggest that myostatin could be associated with certain functions of the internal organs, such as energy metabolism or fibrosis. We conclude that myostatin is a factor broadly expressed in the internal organs and muscle tissues of pigs.

Embryology and bony malformations of the craniovertebral junction

BACKGROUND

The embryology of the bony craniovertebral junction (CVJ) is reviewed with the purpose of explaining the genesis and unusual configurations of the numerous congenital malformations in this region. Functionally, the bony CVJ can be divided into a central pillar consisting of the basiocciput and dental pivot and a two-tiered ring revolving round the central pivot, comprising the foramen magnum rim and occipital condyles above and the atlantal ring below. Embryologically, the central pillar and the surrounding rings descend from different primordia, and accordingly, developmental anomalies at the CVJ can also be segregated into those affecting the central pillar and those affecting the surrounding rings, respectively.

DISCUSSION

A logical classification of this seemingly unwieldy group of malformations is thus possible based on their ontogenetic lineage, morbid anatomy, and clinical relevance. Representative examples of the main constituents of this classification scheme are given, and their surgical treatments are selectively discussed.

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.

Change in plasma Aß peptides and onset of dementia in adults with Down syndrome

OBJECTIVE

To examine changes in levels of plasma amyloid-β (Aβ) peptides, Aβ42 and Aβ40, in relation to onset of Alzheimer disease (AD) in adults with Down syndrome (DS).

METHODS

Plasma Aβ42 and Aβ40 were measured at initial examination and at follow-up in a community-based cohort of 225 adults with DS who did not have dementia at baseline and were assessed for cognitive/functional abilities and health status and followed at 14- to 20-month intervals. We used Cox proportional hazards modeling to estimate the cumulative incidence of AD by Aβ peptide change group (increasing, no change, or decreasing), adjusting for covariates.

RESULTS

Sixty-one (27.1%) of the participants developed AD. At follow-up, a decrease in Aβ42 levels, a decrease in the Aβ42/Aβ40 ratio, and an increase in Aβ40 levels were related to conversion to AD. Compared with the group with increasing levels of Aβ42, the likelihood of developing AD was 5 times higher for those whose plasma Aβ42 levels decreased over follow-up (hazard ratio [HR] = 4.9, 95% confidence interval [CI] 2.1-11.4). Decreasing Aβ42/Aβ40 was also strongly related to AD risk (HR = 4.9, 95% CI 1.8-13.2), while decreasing Aβ40 was associated with lower risk (HR = 0.4, 95% CI 0.2-0.9).

CONCLUSIONS

Among adults with DS, decreasing levels of plasma Aβ42, a decline in the Aβ42/Aβ40 ratio, or increasing levels of Aβ40 may be sensitive indicators of conversion to AD, possibly reflecting compartmentalization of Aβ peptides in the brain.

Atlantoaxial Rotatory Fixation

OBJECTIVE

Atlantoaxial rotatory fixation (AARF) remains a recondite entity. Our normative study using CT motion analysis shows that there is a high degree of concordance for rotational behavior of C1 and C2 in children 0 to 18 years. C1 always crosses C2 at or near 0 degree. The predictable relationship between C1 and C2 is depicted by 3 distinct regions on the motion curve: when C1 rotates from 0 to 23 degrees, it moves alone while C2 remains stationary at 0 (the single-motion phase). When C1 rotates from 24 to 65 degrees, C1 and C2 move together (the double-motion phase), but C1 always moves faster as C2 is being pulled by yoking ligaments. From 65 degrees onward, C1 and C2 move in unison (the unison-motion phase) with a fixed, maximal separation angle of approximately 43 degrees, the head rotation being carried exclusively by the subaxial segments. Because of this high concordance among patients and a relatively narrow variance from the mean, the physiological composite motion curve can be used as a normal template for the diagnosis and classification of AARF.

METHODS

Using a 3-position CT protocol to obtain the diagnostic motion curve, we identified 3 distinct types of AARF. Type I AARF patients show essentially unaltered (“locked”) C1–C2 coupling regardless of corrective counterrotation, with curves that are horizontal lines in the upper 2 quadrants of the template. Type II AARF patients show reduction of the C1–C2 separation angle with forced correction, but C1 cannot be made to cross C2. Their curves slope downward from the right to left upper quadrants but never traverse the x axis. Type III AARF patients show C1–C2 crossover but only when the head is cranked far to the opposite side. Their motion curves traverse the x axis far left of 0 degree ( C1 &lt; −20). Thus, type I, II, and III AARF are in descending degrees of pathological stickiness. A fourth group of patients showing motion curve features between normal and type III AARF are designated as belonging to a diagnostic gray zone (DGZ). The AARF patients are further classified as acute if treatment is started less than 1 month from the onset of symptoms, as subacute if the delay in treatment is 1 to 3 months, and chronic if treatment delay exceeds 3 months. The treatment protocol for AARF consists of reduction using either halter or caliper traction and then immobilization with brace or halo, depending on the AARF type and chronicity. Recurrent slippage and irreducibility are treated with C1–C2 fusion.

RESULTS

The treatment course and outcome of AARF are analyzed according to the AARF type and chronicity. The difficulty and duration of treatment, the number of recurrent slippage, the rate of irreducibility, the need for halo and fusion, and the percentage ultimately losing normal C1–C2 rotation are significantly greater in type I patients than type III patients, with type II patients somewhere in between. Likewise, all parameters are much worse in patients with any type of chronic AARF than acute AARF. The worse subgroup is chronic type I versus the best subgroup of acute type III. Recurrent AARF patients do much worse than nonrecurrent AARF patients. Recurrence is, in turn, adversely influenced by both the severity (type) and chronicity of AARF. The symptoms of most DGZ patients will resolve with analgesics, but a few remain symptomatic or deteriorate to true AARF requiring the full treatment.

CONCLUSION

Thus, children with painful torticollis should undergo the 3-position CT protocol not only to confirm the diagnosis of AARF but also to grade its severity. Closed reduction with traction should be instituted immediately to avoid the serious consequences of chronicity. Proper typing and reckoning of the pretreatment delay are requisites for selecting treatment modalities. Recurrent dislocation and incomplete reduction should be treated with posterior C1–C2 fusion in the best achievable alignment.