Airway management in children with major craniofacial anomalies.

OBJECTIVES: Delineation of clinical characteristics affecting the airway in a cohort of craniofacially deformed children. What factors differ between patients requiring and those not requiring surgical airway intervention? What factors predispose to the need for tracheotomy? When can decannulation be expected if tracheotomy is required? What interventions aid decannulation? STUDY DESIGN: Five-year retrospective chart review at tertiary center. METHODS: Two hundred fifty-one patients met the following entry criteria: enrollment in the New York University Institute of Reconstructive and Plastic Surgery's Craniofacial Clinic and admission to Tisch Hospital in Manhattan for surgery from 1990 to 1994. Hospital, clinic, and departmental office records were reviewed. All patients had major craniofacial bony anomalies and underwent administration of general anesthesia at least once. RESULTS: Nearly 20% of all children required tracheotomy (47/251). Craniofacial synostosis patients (Crouzon, Pfeiffer, or Apert syndrome) had the highest rate of tracheotomy (48% [28/59]). Mandibulofacial dysostoses patients (Treacher Collins or Nager syndrome) had the next highest rate (41% [28/59]). Patients with oculo-auriculo-vertebral sequence were less likely to undergo tracheotomy (22% [9/41]). Children with craniosynostosis rarely required a surgical airway, unless there was marked associated facial dysmorphism (1% [1/72]). The duration of cannulation was related to the age at tracheotomy in a bimodal distribution. Generally, tracheotomies required before age 4 years remained for several years, whereas those placed after age 4 were removed after several weeks. The presence of a cleft palate correlated with reduced risk for tracheotomy, but the presence of a ventriculoperitoneal shunt correlated with an increased risk for tracheotomy. Procedures selectively used to improve the airway included midface advancement, mandibular expansion, tonsillectomy and adenoidectomy, uvulopalatopharyngoplasty, anterior tongue reduction, and endoscopic tracheal granuloma excision. CONCLUSIONS: The likelihood for surgical airway management is related to specific craniofacial diagnosis. The length of tracheal cannulation is greatest for infants and young children who manifest severe airway compromise, often because of nasal obstruction in combination with other anatomic factors. Early tracheotomy is advocated for these patients to promote optimal growth and development. Choanal atresia is often misdiagnosed in these infants; nasal obstruction is actually secondary to midface retrusion. Staged surgical interventions can allow eventual successful decannulation in nearly all cases of craniofacial syndromes.

Paradoxical spread of renal cell carcinoma to the head and neck.

OBJECTIVES: To present cases of renal cell carcinoma presenting with only head and neck metastases, to review theories of physiology and anatomy describing this phenomenon, and to discuss the role of the otolaryngologist in the treatment of these lesions. STUDY DESIGN: Retrospective review of the records of three patients who presented with renal cell carcinoma with head and neck metastases over the 3-year period from 1992 to 1995. METHODS: Retrospective review of the records of three patients who presented with renal cell carcinoma with head and neck metastases. In addition, English-language literature was reviewed with special focus on the anatomic and physiologic pathways possible to allow for such a phenomenon. CONCLUSIONS: Renal cell carcinoma has an occasional presentation as a head and neck mass without evidence of disease elsewhere. Various routes of spread have been postulated. Batson's venous plexus, as postulated by Nahum and Bailey, is an anatomic route through which emboli could navigate to the head and neck and avoid pulmonary vascular filtration. Interactions on the cellular level may also be responsible for the seemingly paradoxical spread. We recommend local excision of head and neck metastases of renal cell carcinoma without sacrifice of vital structures as a sound treatment regimen.

Moving the retina: choroidal modulation of refractive state.

The chick eye is able to change its refractive state by as much as 7 D by pushing the retina forward or pulling it back; this is effected by changes in the thickness of the choroid, the vascular tissue behind the retina and pigment epithelium. Chick eyes first made myopic by wearing diffusers and then permitted unrestricted vision developed choroids several times thicker than normal within days, thereby speeding recovery from deprivation myopia. Choroidal expansion does not occur when visual cues are reduced by dim illumination during the period of unrestricted vision. Furthermore, in chick eyes presented with myopic or hyperopic defocus by means of spectacle lenses, the choroid expands or thins, respectively, in compensation for the specific defocus imposed. Consequently, when the lenses are removed, the eye finds its refractive error suddenly of opposite sign, and the choroidal thickness again compensates by changing in the opposite direction. If a local region of the eye is made myopic by a partial diffuser and then given unrestricted vision, the choroid expands only in the myopic region. Although the mechanism of choroidal expansion is unknown, it might involve either a increased routing of aqueous humor into the uveoscleral outflow or osmotically generated water movement into the choroid. The latter is compatible with the increased choroidal proteoglycan synthesis either when eyes wear positive lenses or after diffuser removal.

The retinal targets of centrifugal neurons and the retinal neurons projecting to the accessory optic system.

In birds, neurons of the isthmo-optic nucleus (ION), as well as "ectopic" neurons, send axons to the retina, where they synapse on cells in the inner nuclear layer (INL). Previous work has shown that centrifugal axons can be divided into two anatomically distinct types depending on their model of termination: either "convergent" or "divergent" (Ramon y Cajal, 1889; Maturana & Frenk, 1965). We show that cytochrome-oxidase histochemistry specifically labels "convergent" centrifugal axons and target neurons which appear to be amacrine cells, as well as three "types" of ganglion cells: two types found in the INL (displaced ganglion cells) and one in the ganglion cell layer. Labeled target amacrine cells have distinct darkly labeled "nests" of boutons enveloping the somas, are associated with labeled centrifugal fibers, and are confined to central retina. Lesions of the isthmo-optic tract abolish the cytochrome-oxidase labeling in the centrifugal axons and in the target amacrine cells but not in the ganglion cells. Cytochrome-oxidase-labeled ganglion cells in the INL are large; one type is oval and similar to the classical displaced ganglion cells of Dogiel, which have been reported to receive centrifugal input; the other type is rounder. Rhodamine beads injected into the accessory optic system results in retrograde label in both types of cells, showing that two distinct types of displaced ganglion cells project to the accessory optic system in chickens. The ganglion cells in the ganglion cell layer that label for cytochrome oxidase also project to the accessory optic system. These have proximal dendrites that ramify in the outer inner plexiform layer.(ABSTRACT TRUNCATED AT 250 WORDS)

Scleral changes in chicks with form-deprivation myopia.

The sclera in myopic regions of chick eyes was studied histologically and compared to the sclera in corresponding regions of normal fellow eyes. Chicks had been monocularly deprived of form vision in the nasal half of the retina from hatching. The fellow control eye and the temporal retina of the deprived eye had normal vision. With this treatment, the resulting form-deprivation myopia and eye enlargement are restricted to the retinal region that had been form deprived. We found that the cartilaginous sclera in the myopic nasal region exhibited several differences from that in the corresponding non-myopic region: it was thicker, its cell density was lower, and the number of chondrocytes and binucleate cells was higher. In contrast, the fibrous sclera was thinner. These changes suggest that form-deprivation myopia causes an increased production of extracellular matrix and an increased level of mitotic activity in the cartilaginous sclera. As expected, the non-myopic temporal regions of experimental and control eyes did not differ in any of these parameters. The findings of the present study suggest that the eye enlargement accompanying form-deprivation myopia is not the consequence of scleral stretching but of abnormal growth.

Visual deprivation causes myopia in chicks with optic nerve section.

Deprivation of form vision restricted to a region of the retina produces myopia and axial elongation only in that region. We asked whether this control of eye growth by the presence or absence of visual stimuli might take place entirely within the eye. Chicks with neonatal optic nerve section, wearing an occluder that deprived one half of the retina of form vision, had vitreous chamber elongation and myopia both restricted to the deprived region. Chicks with optic nerve section but without occluders had eyes smaller than normal with severe hyperopia. These results suggest that two different mechanisms may control eye growth, one within the eye and the other in the brain.

Different visual deprivations produce different ametropias and different eye shapes.

To compare the effects on the postnatal development of the eye of both total and partial form deprivation in diurnally reared chicks and of dark-rearing, chicks were reared with occluders covering one eye from hatching for up to 6 weeks. In diurnally reared birds, both total and partial form deprivation resulted in severe axial myopia and increased eye size. These effects were greatest for the eyes of chicks raised with total form deprivation; they had highly curved corneas and very deep anterior and vitreous chambers. In addition, the amount of myopia produced in eyes with total form deprivation was the same at 2 and 6 weeks, whereas eyes with partial form deprivation showed substantial remission even with the occluders left on. The partially deprived eyes developed a striking shape asymmetry: the posterior globe only became enlarged in the deprived region of the retina. The eyes of dark-reared chicks, regardless of whether or not an occluder was worn, also were enlarged but were hyperopic owing to a severe flattening of the cornea. This hyperopia was slow to develop compared to the myopia produced in the diurnally reared visually restricted eyes. Finally, the shape of the posterior globe of these hyperopic eyes was no different from that of normal eyes.

Local retinal regions control local eye growth and myopia.

In chicks, visual deprivation leads to myopia and enlargement of the vitreous chamber of the eye. When chicks were raised with white translucent occluders over their eyes so that either the nasal half, the temporal half, or all of the retina was visually deprived, the resulting myopia (median = -15 diopters) was limited to the deprived part of the retina, regardless of which half of the retina was visually deprived; the nondeprived part remained nearly emmetropic. Correspondingly, the vitreous chamber was elongated only in the region of the visual deprivation, resulting in eyes with different asymmetric shapes depending on which retinal region was deprived. These results argue for a local regulation of ocular growth that is dependent on vision and suggest a hypothesis to explain the epidemiological association of myopia in humans with large amounts of reading. Because most nonfoveal retinal neurons have large receptive fields, they cannot resolve the individual letters on the printed page; this may lead to their activity being less during reading than during most other forms of visual stimulation. Thus, the impoverished stimulus situation of reading may lead to myopia, as do other types of visual form deprivation.

Two-pulse temporal integration functions in the fovea and peripheral retina.

The temporal integration of luminous energy was compared in the fovea and at 7 degrees eccentricity using two-pulse stimuli and two methodologies. The two-pulse stimuli consisted of two 1-msec. light pulses separated by intervals of darkness ranging from 1 to 400 msec.; they were provided by a glow modulator tube transilluminating a 21.8' opal glass target. In Exp. 1 (equal-performance design), integration functions were generated using a forced-choice staircase procedure to estimate threshold luminance. The data for two Os showed that the critical duration (CD), and thus the period of complete integration, was briefer in the fovea than at 7 degrees. Beyond the CD, integration continued to differ for the two retinal locations. In the fovea, two-pulse stimuli beyond CD evidenced partial integration and at the longest stimulus durations no integration or inhibition. In contrast, at 7 degrees stimuli beyond CD appeared to evidence probability summation. In Exp. 2 (equal-energy design), integration functions were generated by measuring the detectability of two-pulse stimuli of different durations but equal in total luminous energy. A signal-detection procedure yielded measures of both response frequency and signal detectability, P(A). The data for two Os showed that for both measures CD was briefer in the fovea than at 7 degrees. Also, in the fovea, long two-pulse stimuli appeared to show no integration or inhibition. Both experiments then showed a foveal-peripheral difference in two-pulse measures of visual temporal integration, with the fovea evidencing less integration. In addition, the forced-choice and signal-detection procedures showed that these loci differences in integration were independent of the Os' response criterion.

Light and electron microscopic study of an avian pretectal nucleus, the lentiform nucleus of the mesencephalon, magnocellular division.

Using several light microscopic methods we have identified the lentiform nucleus of the mesencephalon, magnocellular division, by its position in the pretectum, its cellular composition, and its complement of retinal afferents and have distinguished it from neighboring structures. At the light microscopic level large neurons (approximately 30 X 21 microns) and small neurons (approximately 13 X 9 microns), which are more numerous, are seen interspersed among myelinated axons. The large neurons are generally ovoid and contain an eccentrically located nucleus and large clumps of Nissl-stained material. In the electron microscope the most notable feature of these neurons is the presence of ribosome rosettes and many parallel arrays of rough endoplasmic reticulum (RER). On the basis of cytological and ultrastructural features, we conclude that only one class of large neuron is present. Although in the light microscope the small neurons appear to be similar, at the ultrastructural level three neuron types have been distinguished: (1) ovoid shape with cytoplasm densely packed with organelles especially RER, (2) round shape with very little cytoplasm with few organelles, and (3) triangular shape with a pale cytoplasmic matrix with some RER. Subsurface membrane configurations are often seen in the somata of all neuron types. In addition, axon terminals, some containing flat vesicles, and other less frequent ones containing round vesicles are seen terminating on the somata of all neuronal cell types. In the neuropil, three types of presynaptic profiles can be identified. Two of these profiles are axodendritic and the third is dendrodendritic. The type R profile, which is often as large as 4 micron 2, is the most numerous, contains large round synaptic vesicles, and is often seen synapsing on several dendritic profiles. The type F profile contains flat vesicles and a relatively dense cytoplasm, and is smaller in area than type R. The third profile, which contains small clusters of pleiomorphic vesicles and apparently is dendritic, forms synapses with dendritic profiles. We propose that the type R axon terminals originate mostly from the retina and the type F mostly from the visual telencephalon.

Early postnatal development of the monkey visual system. I. Growth of the lateral geniculate nucleus and striate cortex.

The postnatal growth of the dorsal lateral geniculate nucleus (LGNd) and the striate cortex (SCx) was compared in the same monkeys, by estimating LGNd volume, and the volume, surface area, and thickness of the SCx at birth, 1, 2, 4, 8 and 17 weeks. Shrinkage during histologic manipulations was determined in individual animals, and the above measurements were adjusted accordingly so that final volumes reflected a common, and, therefore, comparable state before processing. The volume of the LGNd increases approximately 17% between 2 and 4 weeks, and this growth primarily reflects that of the parvocellular laminae, the magnocellular components contributing a stable amount in absolute terms. Lamina 1 is larger than lamina 2 at all ages sampled. In contrast, the SCx expands about 75% in volume from birth to the oldest age examined without reaching an asymptote during the period of study. During the first 2 postnatal months, the growth results from increases in the thickness of the SCx whereas in the second 2 months it is caused by expansion in surface area. A comparison of exposed vs buried SCx does not reveal differences in the developmental patterns of regions subserving central vs peripheral visual fields, respectively, the exposed cortex being consistently greater in volume and area but thinner than the buried segment. No significant right/left asymmetries are found across the subjects in either of the structures studied. The findings indicate that the early postnatal development of the monkey visual system proceeds in a sequential fashion with the LGNd preceding that of the SCx.