Although the vertebral columns of anurans have received much study in the last 150 years, few detailed descriptions exist of the skeletal morphogenesis of this anatomical unit. Herein, the ontogeny of the vertebral skeleton of the hylid frog Acris crepitans is described based on cleared and double-stained specimens, radiographs, and 3D reconstructions generated from synchrotron microCT scans. The adult axial formula is 1-7-1-1, and the vertebral centra are epichordal and procoelous. The neural arches are nonimbricate, and there is a medial articulation between the laminae of Presacrals I and II. Free ribs are absent. The sacral diapophyses are uniform in width or slightly expanded distally. The urostyle is slender, round in cross section, and about equal in length to the presacral region. Presacral vertebrae are the first to form, developing in a cephalic-to-caudal sequence. However, development and growth are decoupled and growth is fastest initially in the posterior presacrals and sacrum. In addition, there is a time lag between the formation of the presacral/sacral region and the postsacral region. More than 8.5% of the specimens examined have vertebral anomalies, and about 50% display small variants from the typical vertebral column morphology. However, these malformations do not seem to have been so severe as to have affected survival.

The spinal cord and spinal motoneurons are densely innervated by terminals of serotonin (5-HT) and norepinephrine (NE) neurons arising mostly from the brain stem, but also from intrinsic spinal neurons. Even after long-term spinal transection (chronic spinal), significant amounts (10%) of 5-HT and NE (monoamines) remain caudal to the injury. To determine the role of such endogenous monoamines, we blocked their action with monoamine receptor antagonists and measured changes in the sodium currents and firing in motoneurons. We focused on persistent sodium currents (Na PIC) and sodium spike properties because they are critical for enabling repetitive firing in motoneurons and are facilitated by monoamines. Intracellular recordings were made from motoneurons in the sacrocaudal spinal cord of normal and chronic spinal rats (2 mo postsacral transection) with the whole sacrocaudal cord acutely removed and maintained in vitro (cords from normal rats termed acute spinal). Acute and chronic spinal rats had TTX-sensitive Na PICs that were respectively 0.62 +/- 0.76 and 1.60 +/- 1.04 nA, with mean onset voltages of -63.0 +/- 5.6 and -64.1 +/- 5.4 mV, measured with slow voltage ramps. Application of 5-HT2A, 5-HT2C, and alpha1-NE receptor antagonists (ketanserin, RS 102221, and WB 4101, respectively) significantly reduced the Na PICs, and a combined application of these three monoamine antagonists completely eliminated the Na PIC, in both acute and chronic spinal rats. Likewise, reduction of presynaptic transmitter release (including 5-HT and NE) with long-term application of cadmium also eliminated the Na PIC. Associated with the elimination of the Na PIC in monoamine antagonists, the motoneurons lost their ability to fire during slow current ramps. At this point, the spike evoked by antidromic stimulation was not affected, suggesting that activation of the transient sodium current was not impaired. However, the spike evoked after a slow ramp depolarization was slightly reduced in height and rate-of-rise, suggesting decreased sodium channel availability as a result of increased channel inactivation. These results suggest that endogenous monoamine receptor activation is critical for enabling the Na PIC and decreasing sodium channel inactivation, ultimately enabling steady repetitive firing in both normal and chronic spinal rats.

Flap techniques have been performed with success in the treatment of pilonidal disease. However, some complex cases such as perianal pilonidal disease need special attention. We describe a modification of a well-known flap technique for secondary perianal pilonidal disease and its early results.Total subcutaneous fistulotomy combined with Karydakis flap was performed on 14 patients. An elliptical incision, described by Karydakis, was made while not including the perianal opening. Both sides of the elliptical incision were deepened down to the gluteal muscle and postsacral fascia. At the level of subcutaneous tissue, attention was directed to the secondary perianal opening. A fine probe was inserted through the perianal skin pit, and the connection site between the fistula and the cyst was observed. A small circular skin incision was made around the probe and the fistula tract was totally excised using electrocautery together with the main cyst. The flap was prepared as described by Karydakis. Before suturing the flap to the other side, perianal subcutaneous tissue was sutured with a fine absorbable material, then, the flap was sutured with 4/0 polypropylene.One patient developed seroma. Neither early failure in wound healing nor recurrence was observed at a mean of 16.2 months (range 4-36 months) follow-up.Total subcutaneous fistulectomy plus Karydakis flap as a single-stage procedure is an effective surgical modality for sacroccocygeal pilonidal disease with secondary perianal opening.

The anuran pelvic girdle is unique among all amphibians in that its acetabular portion is located far posterior to the sacrum, lateral to the postsacral (= caudal) vertebral column, which is reduced to a single rod-like element called the urostyle. This situation in the adult is strikingly different not only from that in ancestral temnospondyls but also in other modern amphibians. Because there is no fossil that would document this evolutionary anatomical modification except for Triadobatrachus, the only data may be inferred from development in modern anurans. We chose seven anuran species (belonging to the genera Discoglossus, Bombina, Pelobates, Bufo, Rana and Xenopus), representing the principal locomotory types (saltation, swimming, crawling and burrowing). Development of the pelvic girdle was studied on cleared and stained whole mounts and partly on serial histological sections. The basic developmental pattern was similar in all species: the pelvis on both sides develops from two centres (puboischiadic and iliac, respectively). The ilium then extends vertically towards the sacral vertebra and later rotates posteriorly so that ultimately the acetabulum is lateral to the tail (= urostyle). Only minor deviations from this pattern were found, mainly associated with differences in water and terrestrial dwelling.

Postembryonic skeletal ontogeny of the pelobatid frog Scaphiopus intermontanus is described based on a developmental series of cleared-and-stained, whole-mount specimens. The focus is on laboratory-reared individuals fed a herbivorous diet as larvae. Although there is variation in the timing of ossification of individual skeletal elements relative to developmental stages based on external morphological criteia, the sequence of skeletal development generally is conservative. Compared with its close relative, S. bombifrons, ossifications that occur during prometamorphosis tend to be slightly delayed in S. intermontanus; however, cranial bones that ossify during late metamorphic climax in S. intermontanus are delayed until post-metamorphosis in S. bombifrons. The differences in timing between the two species are consistent, however, with differences observed between two developmental series of S. intermontanus raised at two different temperatures. Noteworthy features of skeletal development in S. intermontanus include: 1) presence of palatine ossifications that form from independent centers of ossification and soon fuse with the postnarial portion of the vomers to form the compound vomeropalatine bones; 2) compound sphenethmoid that may arise from four or more endochondral centers of ossification and one dorsal, dermal center of ossification; and 3) presence of transverse processes and vestigal prezygapophyses on the first postsacral vertebra. The morphology of the larval orbitohyoideus and interhyoideus muscles is compared. The record of skeletal ontogeny and muscle morphology presented herein for the herbivorous larval morph can serve as a baseline for comparisons with the ontogeny of the carnivorous larval morph of Scaphiopus.

Myxopapillary ependymomas are highly vascular tumors that arise almost exclusively in the thoracolumbar region and produce symptoms that may mimic discogenic pathology. The purpose of our study was to define the typical MR features of myxopapillary ependymoma and to determine the value of MR imaging in identifying the tumor, establishing its extent, and defining its relationship to intraspinal structures.MR studies performed on 20 patients (13 men and seven women; mean age, 35 years) with 24 pathologically proven myxopapillary ependymomas were evaluated retrospectively for size and location of lesions, expansion of the central spinal canal and neural foramina, and MR signal characteristics and enhancement patterns. T1-weighted (16 patients), proton density-weighted (15 patients), T2-weighted (14 patients), and enhanced T1-weighted (nine patients) sequences were examined.In all patients, masses were detected on MR images. MR imaging defined solitary masses in 17 patients and multiple lesions in three. Of the 24 tumors, MR imaging characterized 21 as predominately intradural extramedullary, two as intramedullary and intradural extramedullary, and one as extradural postsacral. Two lesions had associated syrinxes. Lesions occurred most often at the level of the L2 vertebral body, and no tumor extended above T9. Tumors spanned an average of four vertebral segments. MR imaging showed expansion of the spinal canal in five of eight tumors that extended over five or more vertebral segments. Two tumors extended into the neural foramina. The T1-weighted signal of the tumor was isointense in 12 patients, hypointense in three patients, and hyperintense in one patient. The T2-weighted signal was always hyperintense. All tumors imaged after administration of IV contrast material showed enhancement.MR imaging was valuable in identifying the extent of tumors and in defining their relationship to the intraspinal structures. Although the MR findings in myxopapillary ependymoma are nonspecific, the diagnosis can be suggested by a large, intensely enhancing, intradural extramedullary thoracolumbar mass that extends for several vertebral levels. Imaging protocols should examine the entire thoracolumbar region and include IV contrast.

Using a variety of neuroanatomical and histological techniques, we compare the spinal cord and peripheral nerve distribution in the tails of larvae from Xenopus laevis and three species of Rana. The relatively large, postsacral spinal cord of Xenopus contains abundant motoneurons and their axons. Spinal nerves exit from the spinal cord in a regular array, one nerve per myotome, from the cervical region to near the end of the tail. Somata of motoneurons innervating caudal myotomes are found along the entire length of the tail. In contrast, the caudal cord of Rana is reduced to a filum terminale consisting of little more than an ependymal tube; spinal nerves to all caudal myotomes leave the cord in the sacral region and reach their motor targets via a cauda equina and caudal plexus. Motoneuron cell bodies innervating caudal myotomes are found only in the sacral region. The Rana larval pattern is similar to that of adult frogs and mammals, whereas the Xenopus larval pattern is more like that of salamanders and reptiles. These gross neuroanatomical differences are not due to differences in the size or developmental stage of the tadpoles, but instead are associated with differences in the swimming behavior of the larvae. The presence of motoneurons in the caudal spinal cord of Xenopus may provide local intermyotomal control within the tail; the elongated topography of the cord appears to permit finer, rostral-to-caudal regulation of neuromuscular activity. The Rana spinal cord, on the other hand--with motoneurons clustered anteriorly--may produce concurrent firing of adjacent ipsilateral myotomes, but at the expense of fine intermyotomal regulation. The fact that nerves in the tail of Xenopus enter and exit from the spinal cord locally, as opposed to far anteriorly as in Rana, means that for tadpoles of the same size, reflex arc lengths are many times shorter in Xenopus.

A subcutaneous sacrococcygeal located myxopapillary ependymoma is a rare presentation of this malignancy. It has a tendency to metastasize, even after a long latent period. This is a report of such a case together with proposals for treatment and follow-up.

A 29-year-old woman underwent surgery for an expanding subcutaneous postsacral mass. At surgery the mass was found to be an extraspinal ependymoma, completely separated from the central nervous system. The tumor was completely excised, with no evidence of recurrence 12 months postoperatively. Review of the literature reveals that only 17 cases of extraspinal postsacral ependymoma and 28 cases of presacral ependymoma have been reported. Postsacral tumors usually present as subcutaneous masses, but presacral tumors present with constipation, abdominal mass, neurologic deficit, and bony erosion. The treatment of choice for this tumor is wide local excision. Radiation may be of some value for local disease; chemotherapy has not been successful. Local recurrence has occurred in 23.5 per cent of the postsacral cases; 50 per cent of these patients died. The local recurrence rate is 14 per cent for patients with presacral masses, and the subsequent mortality rate has been 75 per cent. Distant metastases have occurred in three patients with postsacral tumors and in two patients with presacral tumors. The greatest chance for cure of this tumor lies with complete excision at the initial operation.

Lesions from the SC region of children examined histologically at the RAHC were: 1. Malformations almost always associated with spina bifida aperta or occulta: 183 myelomeningocele (MM), 32 meningocele (M), 35 lipoMM and lipoma, 19 dermoid cyst, six occult meningocele, two Pacinian hamartoma, one short filum, four hindgut cysts or sinuses, two tailgut cysts, and two epithelial heterotopia. 2. Neoplasms, usually without spina bifida: 56 teratomas (11 malignant), five ependymomas (two purely subcutaneous), and 14 miscellaneous primary malignancies, (most neuroblastoma and rhabdomyosarcoma). Distinction between MM with glial tissue and M without glial tissue is important as M had a much better prognosis, less than a third developing hydrocephalus, and 77% walking unaided. Of those with glial tissue, the eight without Arnold-Chiari malformation were myelocystocele associated with cloacal exstrophy (six), caudal regression syndrome (one), and microcephaly (one). Postsacral glial tissue without paraplegia may occur with a subcutaneous vestige of filum terminale, or with herniation of the nonfunctioning half of a diplomyelia. Of postsacral "lipomas" and dermoids, 70% had an intraspinal connection through an occult spina bifida. This posterior vertebral defect is easily overlooked as the arches normally may not ossify until after 6 years. Therefore, the pathologist receiving a postsacral specimen may wish to alert the clinician to the high incidence of late effects from an occult intraspinal component or tethering of the spinal cord. Transsacral hindgut herniations and cysts probably result from ectoendodermal adhesions. Presacral multicystic malformations with mixed squamous and mucus cell lining are probably tailgut remnants or anorectal duplications, and may be mistaken for dermoid or teratoma. In SC teratoma in infants, contrary to some reports on ovarian teratoma in adults, immature tissues do not indicate a worse prognosis. Malignancy is virtually confined to teratomas including a carcinomatous or "yolk sac" component. It is more common in predominantly presacral examples and rare before the age of 4 months. SC ependymoma differs from ependymoma elsewhere in that it may be primary outside the craniospinal cavity (presacral or postsacral), may have a myxopapillary pattern special to the region, and although low-grade and slow growing, is more likely to metastasize beyond the central nervous system. Postsacral examples arise from vestiges of the filum terminale which are normal in the subcutis there. Combinations of all these lesions occur with vertebral defects and with each other.(

ABSTRACT

TRUNCATED AT 400 WORDS)